HEALTH
RISK
BASED
CONCENTRATIONS
FOR
FERTILIZER
PRODUCTS
AND
FERTILIZER
APPLICATORS
February
22,
1999
Prepared
for:
The
Fertilizer
Institute
Washington,
D.
C.

1220
Nineteenth
St,
NW,
Suite
300
Washington,
DC
20036­
2400
e­
mail
science@
weinberggroup.
com
THE
WEINBERG
GROUP
INC.
WASHINGTON
BRUSSELS
PARIS
NEW
YORK
SAN
FRANCISCO
ii
TABLE
OF
CONTENTS
Page
EXECUTIVE
SUMMARY
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v
1.0
INTRODUCTION
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1
2.0
SELECTION
OF
METALS
OF
POTENTIAL
CONCERN
(
MOPC)
AND
DISCUSSION
OF
MACRONUTRIENT
AND
MICRONUTRIENT
FERTILIZERS
AND
THEIR
APPLICATION
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4
3.0
EXPOSURE
ASSESSMENT
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5
3.1
Identification
and
Characterization
of
Potential
Receptors
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5
3.1.1
Residential
Applicator
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6
3.1.2
Professional
Applicators
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6
3.1.2.1
Nursery
Worker
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6
3.1.2.2
Farm
Worker
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7
3.1.2.3
Golf
Course
Worker
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7
3.1.2.4
Lawn
Care
Professional
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7
3.2
Qualitative
Evaluation
of
Applicator
Scenarios
and
Selection
of
Representative
Case
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8
3.2.1
Resident
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8
3.2.2
Professional
Applicators
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8
3.2.2.1
Nursery
Worker
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8
3.2.2.2
Farm
Worker
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8
3.2.2.3
Golf
Course
Worker
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9
3.2.2.4
Lawn
Care
Professional
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9
3.2.4
Selection
of
the
Applicator
Scenario
Representative
Case
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9
3.3
Pathways
of
Exposure
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9
3.4
Development
of
Exposure
Parameters
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10
3.4.1
Standard
USEPA
Recommended
Default
Exposure
Parameters
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10
3.4.2
Other
Exposure
Parameters
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11
3.4.2.1
Fraction
of
Day
and
Exposure
Frequency
Parameter
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11
3.4.2.2
Dermal
Absorption
Fraction
for
the
MOPCs
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12
3.4.2.3
Air
Concentrations
of
Fertilizer
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12
4.0
TOXICITY
EVALUATION
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12
4.1
Carcinogenic
Effects
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13
4.2
Non­
Carcinogenic
Effects
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13
4.3
Toxicity
Value
for
Lead
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13
iii
5.0
CALCULATION
AND
PRESENTATION
OF
RISK
BASED
CONCENTRATIONS
(
RBCs)
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14
5.1
Calculation
of
the
RBC
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14
5.2
How
the
RBCs
Should
be
Used
to
Screen
Specific
Fertilizer
Products
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16
6.0
UNCERTAINTY
ANALYSIS
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17
7.0
SUMMARY
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17
8.0
REFERENCES
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19
APPENDIX
A
Modeled
Air
Concentrations
for
Fertilizer
Dust
iv
TABLES
(
presented
at
the
end
of
the
document)

Table
1
Qualitative
Evaluation
of
the
Exposure
Potential
Associated
with
Major
Exposure
Factors
for
Typical
Fertilizer
Applicators
Table
2
Exposure
Parameters
and
Assumptions
for
Fertilizer
Applicator
Risk
Based
Concentrations
(
RBCs)

Table
3
Oral
and
Dermal
Toxicity
Criteria
for
Metals
of
Potential
Concern
(
MOPCs)

Table
4
Inhalation
Toxicity
Criteria
for
Metals
of
Potential
Concern
(
MOPCs)

Table
5
Dermal
Absorption
Values
for
Metals
of
Potential
Concern
(
MOPCs)
and
Route
Specific
Absorption
Values
for
Lead
Table
6
Risk
Based
Concentrations
(
RBCs)
for
Fertilizer
Applicator
Scenarios
Table
7
Risk
Based
Concentrations
(
RBCs)
for
Screening
Table
8
Major
Assumptions
and
Uncertainties
Associated
with
the
Risk
Based
Concentrations
(
RBCs)
v
EXECUTIVE
SUMMARY
This
document
develops
screening­
level
health
risk
based
concentrations
(
RBCs)
for
applicators
of
commercial
inorganic
fertilizers.
RBCs
are
the
amount
or
concentration
of
a
non­
nutrient
element
in
a
fertilizer
that
is
considered
health
protective
at
a
given
acceptable
risk
level
and
a
particular
type
of
exposure.
The
purpose
of
this
document
is
to
provide
fertilizer
manufacturers,
applicators
and
interested
regulators
with
an
easy
tool
to
evaluate
whether
the
concentrations
of
select
non­
nutrient
elements
in
a
particular
commercial
inorganic
fertilizer
may
pose
a
health
risk
to
the
applicator
as
a
result
of
exposures.
The
RBCs
are
conservatively
derived,
using
high
end
values
for
exposure
and
toxicity
parameters,
to
ensure
that
fertilizer
applicator
health
risks
are
not
underestimated.

RBCs
are
developed
for
four
non­
nutrient
elements:
arsenic,
cadmium,
lead,
and
mercury,
termed
metals
of
potential
concern
(
MOPC),
that
are
components
of
phosphate
fertilizers
and
micronutrient
fertilizers.
These
metals
and
fertilizers
are
considered
to
represent
the
greatest
potential
health
concern
for
applicators
because
(
1)
the
metals
are
generally
considered
to
be
more
toxicologically
significant
compared
to
other
metals
found
in
inorganic
commercial
fertilizers,
and
(
2)
because
these
particular
fertilizers
tend
to
contain
the
highest
concentrations
of
these
metals
among
all
inorganic
fertilizers.

In
addition,
RBCs
are
developed
for
two
fertilizer
applicator
scenarios.
The
first
is
a
lawn
care
professional
who
is
considered
to
have
the
highest
exposure
potential
among
all
applicators.
Exposure
is
assumed
to
occur
200
days
per
year,
four
hours
per
day,
for
30
years.
The
second
is
a
farm
worker
who
is
considered
to
be
representative
of
applicators,
including
nursery
workers,
golf
course
workers
and
home
applicators,
whose
overall
exposure
potential
is
significantly
less
than
the
lawn
care
professional.
These
two
sets
of
RBCs
provide
some
degree
of
initial
flexibility
in
evaluating
products
that
are
used
only
in
lawn
or
in
crop
applications.

In
general,
United
States
Environmental
Protection
Agency
(
USEPA)
standard
approaches
and
values
were
used
in
developing
these
RBCs.
The
standard
direct
pathways
of
exposure
included
incidental
ingestion,
dermal
contact,
and
inhalation.
Acceptable
target
cancer
risks
of
1
in
100,000
(
or
1
X
10­
5)
for
occupational
settings
and
an
acceptable
non­
cancer
hazard
index
of
1
were
used
to
develop
the
RBC
values.
Industry
professionals
were
consulted
and
published
data
were
used
in
developing
reasonable
high
end
exposure
and
toxicity
estimates.
Where
available,
standard
USEPA
exposure
parameters
were
selected.
An
uncertainty
analysis
is
presented
to
account
for
the
major
assumptions
applied
in
developing
the
RBCs.
It
concludes
that
the
RBCs
for
fertilizer
applicators
are
health
protective.

The
screening­
level
RBC
values
are
presented
in
Table
7.
These
RBCs
can
be
directly
compared
to
the
measured
concentration
of
the
particular
non­
nutritive
element
in
a
fertilizer
product.
A
procedure
for
such
a
screening­
level
risk
evaluation,
along
with
considerations
for
adjusting
the
RBCs
to
take
into
account
more
specific
product
use
and
applicator
exposure
information,
is
described
in
this
report.
Actual
comparisons
are
presented
in
a
separate
document
being
prepared
by
THE
WEINBERG
GROUP
for
The
Fertilizer
Institute.
1
1.0
INTRODUCTION
This
document
presents
generic
health
risk
based
concentrations
(
RBCs)
for
applicators
of
commercial
inorganic
fertilizers.
For
our
purposes,
RBCs
are
the
amount
or
concentration
of
a
non­
nutrient
element
in
a
fertilizer
that
is
considered
health
protective
at
a
given
acceptable
risk
level
and
a
particular
type
of
exposure.
The
purpose
of
this
document
is
to
provide
fertilizer
manufacturers,
applicators
and
interested
regulators
with
an
easy
tool
to
evaluate
whether
the
concentrations
of
select
non­
nutrient
elements
in
a
particular
commercial
inorganic
fertilizer
may
pose
a
health
risk
to
the
applicator
as
a
result
of
exposures.
The
RBCs
are
conservatively
derived
to
ensure
that
health
risks
are
not
underestimated.
If
the
concentration
of
the
non­
nutrient
element
in
the
fertilizer
is
below
the
RBC,
there
is
no
health
risk
to
the
applicator
due
to
handling
the
product.
If
the
concentration
of
the
non­
nutrient
element
in
the
fertilizer
is
above
the
RBC,
there
may
be
a
health
risk
to
the
applicator;
however,
a
more
intensive
evaluation
of
the
specific
exposure
scenario,
and
of
the
conservative
assumptions
used
to
derive
the
RBC
value,
would
need
to
be
conducted
before
a
firm
conclusion
can
be
reached.
The
RBC
approach
described
in
this
document
provides
a
screening­
level
evaluation.

In
this
document,
RBCs
are
developed
for
four
select
non­
nutrient
elements:
arsenic,
cadmium,
lead,
and
mercury.
Two
sets
of
RBCs
are
developed
for
each
non­
nutrient
element,
one
for
macronutrient
(
N­
P­
K)
fertilizers
and
one
for
micronutrient
fertilizers.
These
generic
RBCs
can
be
directly
compared
to
the
measured
concentration
of
the
particular
non­
nutritive
element
in
the
product.
A
shorthand
term
used
to
identify
these
elements
is
"
MOPC",
or
metal
of
potential
concern.
The
procedure
for
this
comparison
of
RBCs
to
measured
concentrations
of
MOPCs
is
described
in
this
report.
Actual
comparisons
are
presented
in
a
separate
document
being
prepared
by
THE
WEINBERG
GROUP
for
The
Fertilizer
Institute.
This
comparison
is
the
initial
step
in
a
health
risk
assessment
of
applicators
exposed
to
non­
nutritive
elements
in
fertilizer
products.

Many
resources
were
consulted
in
the
preparation
of
this
document.
A
number
of
contacts
were
made
within
the
fertilizer
applicator
industry
to
gather
relevant
information
on
potential
exposure
including:
amount
of
fertilizer
applied,
frequency
of
application,
forms
of
fertilizer
used,
modes
of
application
and
precautions
taken
to
minimize
exposure
in
the
workplace.
In
general,
the
development
of
the
RBCs
follows
basic
United
States
Environmental
Protection
Agency
(
USEPA)
risk
assessment
procedures.
The
following
published
resources
were
primarily
consulted
in
preparing
this
report:


California
Department
of
Food
and
Agriculture
(
CDFA)
1998.
Development
of
Risk­
Based
Concentrations
for
Arsenic,
Cadmium,
and
Lead
in
Inorganic
Commercial
Fertilizers.


USEPA
1989.
Risk
Assessment
Guidance
for
Superfund:
Volume
I­
Human
Health
Evaluation
Manual.
2

USEPA
1997a.
Exposure
Factors
Handbook.
Volumes
I,
II
and
III.
EPA/
600/
P­
95/
002Fa,
b,
c.


USEPA
1997b.
Standard
Operating
Procedures
(
SOPs)
for
Residential
Exposure
Assessments.
Draft,
prepared
by
the
Residential
Exposure
Assessment
Group
(
Office
of
Pesticide
Programs,
Health
Effects
Division,
and
Versar,
Inc.).
Contract
No.
68­
W6­
0030,
Work
Assignment
No.
3385,102.
December
18.

The
following
sections
are
presented
in
this
report.

2.0
SELECTION
OF
METALS
OF
POTENTIAL
CONCERN
(
MOPC)
AND
DISCUSSION
OF
MACRONUTRIENT
AND
MICRONUTRIENT
FERTILIZERS
AND
THEIR
APPLICATION
This
section
presents
the
selection
of
the
metals
of
potential
concern
(
MOPC).
A
general
discussion
of
difference
between
macronutrient
fertilizers
and
micronutrient
fertilizers
and
the
basis
for
evaluating
them
separately
is
also
presented.

3.0
EXPOSURE
ASSESSMENT
This
section
describes
and
supports
the
potential
exposure
scenarios
and
exposure
pathways.
The
population
and
exposure
pathways
of
concern
are
identified
and
presented.
The
specific
exposure
parameters
are
presented
along
with
a
justification
for
each
parameter.

4.0
TOXICITY
ASSESSMENT
This
section
presents
the
toxicity
values
that
are
used
to
calculate
the
RBCs.
In
accordance
with
standard
risk
assessment
practice,
cancer
and
noncancer
toxicity
endpoints
were
considered.
In
addition,
the
evaluation
of
lead,
which
has
unique
toxicity,
is
presented.

5.0
CALCULATION
AND
PRESENTATION
OF
RISK
BASED
CONCENTRATIONS
(
RBCs)

The
risk
based
concentrations
(
RBCs)
for
each
non­
nutrient
element
and
fertilizer
are
presented
in
this
section.
A
discussion
of
how
these
RBCs
are
calculated
and
how
they
should
be
used
is
provided.

6.0
UNCERTAINTY
ANALYSIS
This
section
presents
an
analysis
of
the
uncertainties
and
variabilities
associated
with
the
assumptions
that
were
made
in
developing
the
RBCs.
A
qualitative
assessment
of
the
degree
to
which
these
assumptions
affects
the
RBCs
is
presented.
3
7.0
SUMMARY
This
section
provides
a
summary
of
the
RBC
values,
what
they
represent,
and
how
they
should
be
used
to
evaluate
whether
there
are
potential
health
risks
to
applicators
from
exposure
to
select
non­
nutrient
elements
in
fertilizers.

8.0
REFERENCES
Full
citations
for
documents
cited
in
this
report
are
presented
in
this
section.
4
2.0
SELECTION
OF
METALS
OF
POTENTIAL
CONCERN
(
MOPC)
AND
DISCUSSION
OF
MACRONUTRIENT
AND
MICRONUTRIENT
FERTILIZERS
AND
THEIR
APPLICATION
Generic
RBCs
are
presented
for
four
metals
of
potential
concern
(
MOPC):
arsenic,
cadmium,
lead,
and
mercury.
These
metals
were
selected
as
MOPCs
in
this
evaluation
of
risks
to
fertilizer
applicators,
because,
they
are
generally
considered
to
have
high
toxicological
significance
among
non­
nutrient
elements
that
are
present
in
inorganic
fertilizers.
For
example,
the
USEPA's
Guide
to
the
Biosolids
Risk
Assessments
for
the
EPA
Part
503
Rule
(
USEPA
1995a),
indicates
these
metals
among
the
lowest
RBCs
in
soil.
The
same
approach
can
be
used
to
derive
RBCs
for
the
other
non­
nutrient
elements
in
inorganic
fertilizers.

This
assessment
focuses
on
two
types
of
inorganic
fertilizers,
macronutrient
(
specifically
phosphate)
fertilizers
and
micronutrient
fertilizers.
Although
all
classes
of
inorganic
fertilizers
contain
some
concentration
of
these
metals,
in
general,
phosphate
fertilizers
and
micronutrient
fertilizers
tend
to
contain
higher
levels
of
the
MOPCs
than
other
fertilizers
(
e.
g.,
urea,
potash,
limestone,
and
gypsum
fertilizers)
(
CDFA
1998,
The
Weinberg
Group
1998).

The
MOPCs
are
present
in
phosphate
fertilizers
because
the
phosphate
fertilizers
are
manufactured
from
phosphate
rock
ores.
Phosphate
ores
contain
naturally
occurring
levels
of
metals.
The
concentration
of
the
MOPC
in
any
phosphate
fertilizer
is
directly
related
to
the
concentration
in
the
original
phosphate
ore.
Some
of
the
metal
in
the
phosphate
ore
can
be
lost
during
the
manufacturing
process
resulting
in
lower
concentrations
in
the
fertilizer
product
(
CDFA
1998).

The
MOPCs
and
their
levels
in
micronutrient
fertilizers
are
dependent
on
material(
s)
from
which
the
fertilizer
is
manufactured.
Along
with
the
essential
nutrients
in
these
materials
(
e.
g.,
zinc,
boron
and
selenium)
there
can
also
be
varying
levels
of
non­
nutrient
elements
including
arsenic,
cadmium,
lead
and
mercury,
the
MOPCs
considered
in
this
analysis.

The
MOPC
concentration
in
a
blended
fertilizer
correlates
primarily
with
the
phosphate
or
micronutrient
fraction
of
the
fertilizer.
While
the
fraction
of
the
fertilizer
that
is
phosphate
or
micronutrient
varies
among
products,
for
the
purposes
of
calculating
conservative,
screening
level
RBCs,
the
assumption
was
made
that
the
fertilizer
product
being
applied
is
100%
phosphate
or
100%
micronutrient.
This
overestimate
of
the
percent
P2O5
and/
or
micronutrient
in
a
given
fertilizer
product
and
its
implications
for
deriving
and
applying
the
RBC
values
are
discussed
in
more
detail
in
Sections
5.0
and
6.0.

The
most
critical
exposure
factors
in
assessing
potential
risks
to
fertilizer
applicators
are
how
often
and
how
long
the
applicator
is
likely
to
be
exposed
to
the
fertilizer.
The
application
rate
(
e.
g.,
pounds
per
acre)
is
much
less
a
factor
for
applicator
exposure
than
it
is
for
crop
ingestion
exposure
(
which
was
the
focus
of
the
1998
CDFA
evaluation
of
RBCs).
The
application
rate
is
a
critical
factor
when
assessing
soil
loading
(
how
much
fertilizer
is
present
in
soil
over
an
extended
period),
and
subsequent
crop
uptake
and
crop
ingestion.
How
often
fertilizer
is
applied
(
frequency)
and
how
long
it
takes
the
applicator
to
apply
the
fertilizer
varies
by
applicator
5
scenario,
as
detailed
in
Section
3.1
below.

The
frequency
and
amount
of
any
fertilizer
applied
will
depend
on
several
factors
including
the
size
of
the
area
to
be
treated,
the
geographic
location
(
e.
g.,
more
frequent
applications
in
warm
climates
with
longer
growing
seasons)
and
the
soil
characteristics.
The
frequency
of
application
and
the
amount
of
fertilizer
that
is
applied
are
also
dependent
on
the
nutrient
needs
of
the
plant,
crop,
or
grass.
The
application
frequency
and
application
amounts
of
micronutrient
fertilizers
are
expected
to
be
considerably
lower
than
for
macronutrient
fertilizers,
because,
micronutrient
needs
are
generally
less.
[
This
is
particularly
relevant
to
this
assessment,
because,
the
focus
is
on
how
much
exposure
an
individual
applicator
might
have
to
MOPCs
in
fertilizers.]

3.0
EXPOSURE
ASSESSMENT
The
exposure
assessment
first
identifies
the
potential
populations
(
called
receptors)
that
may
come
in
contact
with
MOPCs
in
macronutrient
and
micronutrient
fertilizers
during
application,
then
describes
the
representative
exposure
scenarios,
and
finally
selects
associated
pathways
of
exposure
that
are
judged
to
be
most
important.
Reasonable
maximum
potential
exposures
are
then
estimated
based
on
identified
exposure
parameters.
These
parameters
are
combined
with
toxicity
criteria
to
calculate
an
RBC
(
as
presented
in
Section
5.0).

One
factor
that
significantly
influences
the
RBC
is
how
often
a
fertilizer
is
handled
and
applied.
As
discussed
above,
this
factor
is
partly
a
function
of
the
nutrient
needs
of
the
plant
or
crop
and
the
size
of
the
application
area.
This
factor
is
also
dependent
on
the
nature
of
the
scenario
in
which
the
fertilizer
is
being
used,
as
further
discussed
below.
In
addition
to
these
factors,
standard
exposure
assumptions
about
receptors
(
such
as
activity
level,
body
weight,
and
surface
area
of
the
skin
that
is
exposed)
are
considered.
The
objective
of
this
exposure
assessment
is
to
develop
an
exposure
scenario
that
is
representative
and
health
protective
of
the
most
reasonable
and
typical
fertilizer
applicator
scenario.

3.1
Identification
and
Characterization
of
Potential
Receptors
This
document
is
specifically
and
purposely
focused
on
exposures
to
MOPCs
in
commercial
inorganic
fertilizers
during
application.
Therefore,
the
potential
receptors
are
persons
who
handle
and
apply
the
fertilizers.
There
are
many
potential
applicator
scenarios.
Examples
covering
the
likely
range
of
reasonable
and
typical
exposures
include:


residents
who
apply
fertilizers
to
lawns,
gardens,
or
plants
at
home.


professional
application
of
fertilizers
in
settings
such
as
golf
courses,
nurseries,
and
lawn
care.
This
would
be
a
true
occupational
exposure.


application
of
fertilizers
in
farming.
Agricultural
use
of
fertilizers
(
and
the
related
exposures)
varies
greatly
depending
on
many
factors
such
as
the
type
of
crops,
size
of
farm,
whether
is
a
single
crop
farm
or
multi­
crop
farm,
and
geographic
region.
6
Development
of
RBCs
for
all
potential
applicator
scenarios
is
not
considered
necessary
for
the
purposes
of
this
screening
level
evaluation.
Applicator
scenarios
that
are
considered
most
representative
and
health
protective
of
all
potential
exposures
were,
therefore,
selected
as
detailed
below,
for
the
development
of
RBCs
for
fertilizer
applicators.

The
process
of
identifying
a
representative
applicator
scenario
is
difficult
and
somewhat
subjective,
largely
because
of
the
high
degree
of
variability
(
as
briefly
presented
above)
among
the
different
application
scenarios,
and
because,
there
is
a
limited
amount
of
information
that
can
be
used
to
determine
the
most
representative
applicator
scenario.
In
developing
the
descriptions
for
these
scenarios,
information
was
obtained
from
discussions
with
professionals
in
the
fertilizer
application
industry.
Information
on
the
farm
applicator
scenario
was
extracted
from
CDFA
1998.
There
is
also
some
general
information
on
exposure
scenarios
in
standard
USEPA
documents
that
was
considered
where
applicable.

3.1.1
Residential
Applicator
At
home,
fertilizers
may
be
applied
on
lawns,
plants
and
bushes,
or
gardens
(
both
edible
and
ornamental).
Residential
application
of
fertilizers
are
expected
to
occur
on
a
relatively
small
scale
and
at
a
relatively
low
frequency
(
e.
g.
one
to
several
times
per
year).
The
fertilizer
may
be
in
granular
or
liquid
form
and
applied
by
a
spreader,
by
hand,
or
by
spraying.
A
residential
applicator
is
likely
to
apply
fertilizers
during
warm
weather
and
may
or
may
not
wear
clothing
that
would
reduce
exposure.
The
home
applicator
may
or
may
not
wear
gloves.

3.1.2
Professional
Applicators
Professional
applicator
scenarios
vary
considerably
from
profession
to
profession.
Several
typical
professional
applicator
scenarios
include
a
nursery
worker,
a
farm
worker,
a
golf
course
worker
and
a
lawn
care
professional.
General
descriptions
of
these
scenarios
follow.

3.1.2.1
Nursery
Worker
In
a
nursery,
fertilizers
can
be
applied
to
plants,
shrubs,
and
other
vegetation
products.
The
degree
of
application
and
occurrence
is
variable
and
will
depend
on
several
factors,
such
as,
the
size
of
the
nursery,
the
type
of
nursery
(
e.
g.,
tree
or
home
and
garden),
and
its
location.
The
frequency
and
amount
of
fertilizer
application
by
an
individual
worker
is
expected
to
be
greater
than
for
a
resident,
but
still
relatively
low.
As
with
the
residential
scenario,
the
formulation
of
the
fertilizer
may
be
granular
or
liquid
and
the
application
could
be
with
a
spreader,
by
hand,
sprayed,
or
poured
straight
from
the
container.
A
nursery
worker
is
likely
to
wear
more
clothing
than
the
resident
during
application
such
as
pants,
gloves,
and
possibly
long
sleeve
shirts;
however,
the
clothing
coverage
will
vary.
Exposure
could
occur
during
stocking,
mixing
or
applying
the
fertilizer.
7
3.1.2.2
Farm
Worker
In
the
farm
setting,
fertilizers
will
be
applied
to
crops.
The
amount
and
frequency
of
fertilizer
application
will
depend
heavily
on
whether
the
farm
is
single
or
multi­
crop,
the
type
of
crop(
s)
the
farm
cultivates,
the
size
of
the
farm
and
its
geographic
location.
Typically,
dry
fertilizers
are
applied
on
a
farm
using
a
spreader
truck
(
CDFA
1998).
Some
dry
and
liquid
fertilizers
are
applied
below
surface
by
injecting
the
fertilizer
in
the
seed
line.
During
both
of
these
methods
of
application,
the
farm
worker
is
not
in
a
location
where
direct
exposure
is
likely
to
occur.
For
example,
during
the
truck
spreader
application,
the
farm
worker
is
in
the
cab
driving
the
truck,
and
the
fertilizer
is
spread
away
from
him.
During
underground
injection,
the
farm
worker
is
not
in
the
field
during
most
of
the
application
(
CDFA
1998).
Exposure
could
occur
during
handling
of
the
fertilizer
and
while
mixing
and/
or
loading
the
fertilizer.
Exposure
while
applying
the
fertilizer
is
expected
to
be
minimal.

3.1.2.3
Golf
Course
Worker
According
to
industry
professionals,
a
normal
part
of
a
golf
course
workers
job
is
to
maintain
the
turf,
which
includes
fertilizing
it.
The
amount
and
frequency
of
application
will
depend
on
the
size
of
the
course
and
the
geographic
location
(
e.
g.,
more
frequent
applications
in
a
warm
climate).
A
typical
golf
course
worker
in
a
warm
climate
may
apply
fertilizer
anywhere
from
a
couple
times
a
month
to
several
days
per
week
(
Industry
Communication,
1999a).
The
most
likely
mode
of
application
will
be
a
spreader
or
spray;
the
spreader
could
be
pushed
by
a
person
or
pulled
by
a
truck.
A
golf
course
applicator
is
likely
to
wear
more
clothes
than
a
resident
and
similar
clothes
to
a
nursery
worker.
Typical
attire
for
a
golf
course
applicator
depends
largely
on
the
weather
and
may
be
shorts
or
pants,
shirts
(
long
or
short
sleeves),
a
hat,
and
gloves.
The
potential
exposure
for
a
golf
course
applicator
is
variable
and
affected
by
many
factors
(
e.
g.,
the
method
of
application,
frequency
of
application,
size
and
geographic
location).
A
golf
course
applicator
may
be
exposed
to
fertilizers
while
mixing
and
handling
the
fertilizer,
and
while
applying
the
fertilizer,
depending
on
the
mode
of
application.
Overall
exposure
would
be
limited
by
the
time
spent
applying
fertilizer,
which
may
be
low
when
compared
to
the
golf
course
worker's
other
responsibilities.

3.1.2.4
Lawn
Care
Professional
A
worker
hired
by
a
professional
lawn
care
service
takes
care
of
residential
and/
or
commercial
lawns
and
may
apply
fertilizers
nearly
every
work
day
(
Industry
Communication
1999b).
The
amount
and
frequency
of
fertilizer
applied
will
depend
on
the
climate,
characterization
of
soil,
size
of
the
lawn,
and
the
number
of
lawns
maintained
each
day.
Similar
to
the
golf
course
worker
scenario,
a
lawn
care
professional
may
apply
granular
or
liquid
fertilizer.
The
size
of
a
residential
or
commercial
lawn
is
much
smaller
than
the
golf
course
lawn,
however,
a
residential
lawn
care
professional
may
care
for
up
to
5
or
6
lawns
per
day
(
Industry
Communication
1999b).
A
lawn
care
professional
is
most
likely
to
apply
fertilizer
by
a
hand
powered
device
(
e.
g.,
spray
with
hose
attached
to
a
truck
or
spread
with
a
man
powered
spreader).
The
protective
clothing
a
lawn
care
professional
may
wear
will
vary.
8
3.2
Qualitative
Evaluation
of
Applicator
Scenarios
and
Selection
of
Representative
Case
The
first
step
in
assessing
exposure
to
a
receptor
is
determining
the
representative
exposure
scenarios
for
the
receptor(
s)
of
interest.
As
mentioned
previously,
developing
RBCs
for
all
of
the
potential
applicator
scenarios
is
not
necessary
for
a
screening­
level
assessment.
Two
scenarios
were
selected
through
a
qualitative
evaluation
of
each
scenario
using
the
different
factors
that
could
contribute
to
the
magnitude
of
exposure
(
presented
in
Table
1).
The
qualitative
descriptors
are
low,
medium,
and
high
indicating
the
relative
level
of
expected
exposure.

3.2.1
Resident
In
comparison
to
the
other
applicator
scenarios,
a
resident
caring
for
his/
her
yard
is
expected
to
have
a
low
exposure
to
fertilizers
for
several
reasons.
First,
the
size
of
the
application
would
be
lower
than
in
professional
settings.
Also
the
number
of
times
fertilizer
is
applied
over
the
course
of
a
year
is
expected
to
be
lower
(
i.
e.,
once
to
several
times
a
year).
One
factor
that
could
contribute
to
exposure
of
residents
is
direct
exposure
to
hands.
Residents
may
apply
the
fertilizer
by
hand
and
may
or
may
not
wear
gloves.
Overall,
residential
exposure
to
fertilizers
is
expected
to
be
low
in
comparison
to
the
other
application
scenarios.

3.2.2
Professional
Applicators
The
potential
for
exposure
during
application
of
fertilizers
in
the
professional
setting
is
typically
expected
to
be
higher
than
for
a
resident.
This
exposure
is
typically
higher
primarily
because
the
frequency
and
length
of
application
is
greater;
professional
applicators
can
be
applying
fertilizer
a
high
percentage
of
their
work
time,
varying
by
profession
as
described
below.

3.2.2.1
Nursery
Worker
In
comparison
to
the
other
professional
applicator
scenarios,
a
nursery
worker
is
expected
to
have
a
low
to
medium
exposure
to
fertilizers.
Nurseries
move
their
stock
as
quickly
as
possible
and
fertilizing
would
add
to
their
costs.
It
is
likely
that
some
fertilizing
would
occur
during
plantings
for
residential
or
commercial
customers.
Nursery
workers
may
also
handle
fertilizers
during
stocking
and
during
loading
into
customer
vehicles.
Contact
with
fertilizers
would
occur
for
a
limited
portion
of
the
work
day
and
would
be
variable
among
nurseries
and
among
nursery
workers.
The
exposure
potential
for
a
nursery
worker
is,
however,
expected
to
be
relatively
low
primarily
because
the
frequency
of
fertilizer
use
is
expected
to
be
low.

3.2.2.2
Farm
Worker
As
discussed
above,
the
amount
and
frequency
of
fertilizer
application
in
a
farm
scenario
is
variable
and
depends
largely
on
the
size
and
location
of
the
farm
and
type
of
crops
cultivated.
This
adds
considerable
variability
into
estimating
the
relative
exposure
potential
for
a
farm
worker.
A
farmer's
resources
and
fertilizer
equipment
options
are
also
a
factor
in
exposure
potential.
A
common
factor
among
the
farm
worker,
nursery
worker,
and
golf
course
worker
that
limits
their
overall
exposure
potential
is
that
fertilizer
handling
and
application
are
only
a
small
9
part
of
their
overall
activities.
The
farm
worker's
exposure
is
estimated
to
be
anywhere
from
low
to
medium.

3.2.2.3
Golf
Course
Worker
As
with
nursery
workers
and
farm
workers,
the
potential
for
exposure
to
fertilizers
for
golf
course
workers
is
expected
to
vary
considerably.
The
frequency
of
application
and
amount
of
fertilizer
used
at
a
golf
course
is
expected
to
be
higher
than
for
a
nursery
or
a
residence,
but
uncertain
compared
to
a
large,
multi­
crop
farm.
Liquid
fertilizers
are
increasing
in
their
popularity
and
may
be
particularly
practical
in
large
area
applications.
The
overall
exposure
potential
for
a
golf
course
worker
could
be
anywhere
from
low
to
high.

3.2.2.4
Lawn
Care
Professional
The
exposure
scenario
and
assessment
of
potential
exposure
to
fertilizer
for
a
lawn
care
professional
is
very
similar
to
the
golf
course
worker.
However,
the
lawn
care
professional
is
considered
to
a
have
higher
potential
for
exposure
primarily,
because,
the
job
calls
for
much
more
frequent
and
lengthy
contact
with
fertilizers.
The
lawn
care
worker
is
predicted
to
have
the
greatest
potential
for
exposure
among
all
the
scenarios
considered.

3.2.4
Selection
of
the
Applicator
Scenario
Representative
Case
The
criteria
for
selecting
the
applicator
scenarios
for
which
RBCs
will
be
developed
include:


Representative
scenario
that
is
health
protective
of
all
potential
applicator
scenarios
and,

Identification
of
a
"
high­
end"
exposure
scenario
plus
an
additional
scenario
that
is
representative
of
the
remaining
"
low­
end"
exposure
scenarios.

Based
on
the
qualitative
evaluation
described
above,
the
resident,
nursery
worker,
and
farm
worker
scenarios
are
typically
expected
to
have
a
relatively
low
potential
for
exposure.
The
golf
course
worker
and
lawn
care
professional
are
typically
expected
to
have
greater
exposure
potential.
The
farm
worker
was
selected
as
a
representative
low­
end
exposure
scenario,
and
the
lawn
care
professional
was
selected
as
the
representative
high­
end
exposure
scenario.
The
development
of
RBCs
for
both
scenarios
is
intended
to
allow
risk
evaluations
more
in
line
with
the
"
lower"
and
"
higher"
ranges
of
possible
exposures;
however,
the
RBCs
for
lawn
care
professionals
would
be
health
protective
for
all
of
the
applicator
scenarios.

3.3
Pathways
of
Exposure
The
second
step
in
assessing
exposure
to
a
receptor
is
determining
the
pathways
of
exposure.
An
exposure
pathway
will
only
be
included
in
calculating
the
RBC
if
the
pathway
is
complete.
An
exposure
pathway
is
considered
complete
if
there
is
(
1)
a
source
and
release
of
the
MOPC
into
the
environment
of
the
receptor,
(
2)
a
transport
mechanism
or
contact
medium,
(
3)
a
potential
point
of
contact
with
the
medium,
and
(
4)
an
exposure
route
at
the
contact
point.
The
principal
routes
of
exposure
for
fertilizer
applicators
are:
10

Dermal
contact
during
handing
and
application;

Incidental
ingestion
during
handling
and
application;
and

Inhalation
of
fertilizer
dust
or
aerosol
during
handling
and
application.

3.4
Development
of
Exposure
Parameters
One
major
component
in
the
development
of
the
RBCs
includes
determining
exposure
parameters
that
quantitatively
define
potential
fertilizer
exposure.
In
general,
the
exposure
parameters
that
were
selected
for
each
scenario
represent
the
reasonable
maximum
exposure
scenario
(
defined
under
USEPA
(
1989)
as
the
highest
exposure
that
is
reasonably
expected
to
occur
that
is
well
above
the
average
case
but
within
the
bounds
of
the
high
end
exposure
case).
In
some
cases,
for
example,
exposure
frequency
and
fraction
of
day
potentially
exposed,
no
information
on
fertilizers
was
available
in
the
standard
USEPA
references.
The
values
for
these
parameters
are
based
on
information
gathered
from
industry
professionals
and,
are
therefore,
considered
best
estimates.
An
attempt
was
made
to
use
values
that
would
be
considered
reasonable
maximum
values.
Other
parameters,
such
as
body
weight,
averaging
time,
and
exposure
duration,
are
standard
USEPA
parameters.
A
detailed
discussion
of
each
of
the
parameters
is
presented
below;
the
values
used
in
the
exposure
modeling
and
the
sources
of
that
information
are
presented
in
Table
2.

3.4.1
Standard
USEPA
Recommended
Default
Exposure
Parameters
Standard
USEPA
recommended
default
values
were
used
for
several
parameters
including:
body
weight,
exposure
duration,
inhalation
rate,
and
averaging
time
for
cancer
and
noncancer
toxic
effects.

In
the
absence
of
information
on
the
ingestion
rate
of
fertilizer
(
IR
f)
(
i.
e.,
the
amount
of
fertilizer
an
applicator
will
incidentally
ingest
that
adsorbs
to
the
applicators
hand)
the
recommended
adult
ingestion
for
soil
of
50
mg/
day
was
used
(
USEPA
1997a).

The
surface
area
of
skin
(
SA)
was
calculated
based
on
skin
surface
areas
(
presented
in
USEPA
1997a)
that
may
not
be
covered
with
clothing
and
is
consequently
available
for
direct
contact
with
fertilizer.
A
skin
surface
area
for
the
farm
worker
of
5750
cm2/
day
was
taken
from
CDFA
1998
and
is
based
on
the
assumption
that
25%
of
the
total
skin
surface
area
(
23,000
cm2/
day)
is
available
for
exposure.
The
dermal
skin
surface
area
for
the
lawn
care
professional
is
based
on
the
conservative
(
i.
e.,
health
protective)
assumption
that
the
lawn
care
worker
is
wearing
shorts,
a
short
sleeve
shirt,
and
no
hat
or
gloves.
Therefore,
the
surface
area
is
the
sum
of
50
percentile
surface
area
of
the
lower
legs,
forearms,
head
and
hands
presented
in
USEPA
1997a.
This
value
is
5700
cm2/
day
and
is
very
similar
to
that
used
for
the
farm
worker.

In
the
absence
of
an
adherence
factor
(
i.
e.,
the
amount
of
the
product
that
is
expected
to
adhere
to
the
skin
following
direct
contact)
specifically
for
fertilizer,
a
USEPA
soil
adherence
factor
(
AF)
of
0.03
mg/
cm2
was
used
for
both
scenarios
(
USEPA
1998).
This
value
is
an
adherence
factor
developed
for
grounds
keeper,
which
is
considered
a
similar
exposure
scenario.
11
The
inhalation
rate
(
IR
a)
for
both
scenarios
is
20
m3/
day
and
is
the
recommended
inhalation
rate
for
moderate
activity
(
USEPA
1997).

3.4.2
Other
Exposure
Parameters
Several
exposure
parameters
are
not
standard
USEPA
parameters
and
are
particular
to
these
fertilizer
application
scenarios
including:
fraction
of
day
(
FOD);
exposure
frequency
(
EF);
and
air
concentration
(
AC).

3.4.2.1
Fraction
of
Day
and
Exposure
Frequency
Parameter
Two
exposure
parameters,
exposure
frequency
(
EF),
the
number
of
days
per
year
the
worker
applies
the
fertilizer,
and
the
fraction
of
the
day
the
applicator
is
potentially
exposed
to
fertilizer
(
FOD),
are
estimated
in
this
assessment
based
on
discussions
with
industry
professionals.
Both
EF
and
FOD
are
dependent
on
the
nature
of
a
specific
applicator
scenario.

The
EF
for
the
farm
worker
is
estimated
at
22
days
per
year
and
is
based
on
how
many
days
it
would
take
a
farm
worker
to
fertilize
an
average
size
farm.
Information
on
the
typical
average
farm
size
and
the
speed
a
farm
worker
can
apply
fertilizer
(
how
many
acres
per
day)
is
available
from
the
United
States
Department
of
Agriculture
(
USDA
1997)
and
American
Agricultural
Economics
Association
(
AAEA
1998).
The
average
size
of
a
typical
US
farm
is
reported
as
436
acres.
These
sources
report
the
speed
at
which
fertilizer
is
applied
to
a
farm
ranging
from
136
acres
per
day
for
a
typical
fertilizer
spreader,
to
480
to
1,200
acres
per
day
for
high
speed
machinery,
to
600
acres
per
day
for
corn
and
soybean
row
crops
in
the
midwest.
The
1998
CDFA
assessment
reports
a
much
lower
speed
of
20
acres
per
day.
In
the
interest
of
developing
conservative,
screening
level
RBC
values
for
applicators,
this
lower
speed
was
used
to
estimate
exposure
frequency.

Based
on
the
above
information,
the
number
of
days
that
a
farm
worker
will
apply
fertilizer
is
436
acres
divided
by
20
acres
per
day,
which
equals
approximately
22
days.
This
value
would
apply
to
a
single
annual
application
of
fertilizer
using
the
slowest
method
of
application.

As
indicated
in
Section
2.0,
an
applicator
is
generally
going
to
apply
macronutrient
fertilizers
more
often
and
in
much
greater
amounts
than
micronutrient
fertilizers.
However,
because
of
the
many
factors
that
influence
the
frequency
and
amount
of
fertilizer
that
is
actually
applied,
it
is
very
difficult
to
estimate
just
how
much
lower
the
EF
would
be
for
micronutrient
fertilizers.
The
EF
value
for
phosphate
fertilizers
was
set
at
22
days,
and
the
EF
for
micronutrient
fertilizers
was
set
at
11
days,
or
one­
half
the
EF
value
for
phosphate
fertilizers.

The
second
exposure
parameter
estimated
for
farm
workers
was
the
fraction
of
the
work
day
that
fertilizers
are
being
applied
(
FOD).
As
discussed
in
Section
3.1.2.2
exposure
is
likely
to
occur
primarily
during
loading.
Using
information
from
industry
professionals
on
the
time
that
it
takes
to
load
a
spreader
and
the
number
of
loadings
that
occur
per
day,
an
estimated
FOD
of
0.20
was
calculated
(
10
minutes
per
loading
X
10
loads
per
day
=
100
minutes
per
day;
100
minutes
=
1.7
hours,
given
there
are
8
hours
of
work
per
day,
1.7/
8
is
approximately
0.20).
The
FOD
was
considered
to
be
comparable
for
phosphate
and
for
micronutrient
fertilizers.
12
The
estimated
EF
for
a
lawn
care
professional
is
also
based
on
conversations
with
industry
professionals.
Several
professional
lawn
care
companies
in
warm
climates,
such
as
California
and
Florida,
report
that
lawn
care
workers
can
apply
fertilizers
a
relatively
high
percentage
of
the
time
(
Industry
Communication
1999b).
Because
it
is
reasonable
to
expect
that
lawn
care
workers
would
spend
some
days
engaged
in
other
activities,
such
as,
mowing
and
trimming
lawns,
the
EF
for
phosphate
fertilizer
was
set
at
200
days/
year
(
out
of
a
possible
250
days/
year).
As
with
the
farm
workers,
the
EF
for
micronutrient
fertilizer
was
set
at
one­
half
the
value,
or
100
days/
year.

The
FOD
for
a
lawn
care
professional
is
also
somewhat
subjective
and
is
based
on
conversations
with
industrial
professionals.
As
discussed
above,
considering
that
lawn
care
professionals
have
other
tasks
to
perform
in
caring
for
lawns,
such
as
mowing,
trimming,
raking
and
watering,
it
is
very
unlikely
that
the
entire
8
hour
work
day
is
spent
fertilizing.
It
was
assumed
that
half
of
the
day
is
spent
applying
fertilizer.
The
FOD
for
both
phosphate
and
micronutrient
fertilizers
is,
therefore,
4
hours
divided
by
8
hours
or
0.5.

3.4.2.2
Dermal
Absorption
Fraction
for
the
MOPCs
The
dermal
absorption
fraction
(
ABS)
is
an
important
parameter
in
the
dermal
exposure
pathway
because
the
skin
acts
as
a
barrier
to
exposure.
Only
the
fraction
of
the
MOPC
that
can
absorb
across
the
skin
and
enter
the
blood
stream
is
included
in
the
estimated
intake.
ABS
values
for
each
of
the
MOPCs
were
taken
from
USEPA
1998
and
are
presented
in
Table
5.

3.4.2.3
Air
Concentrations
of
Fertilizer
Air
concentrations
(
AC)
of
fertilizer
were
derived
using
approaches
and
parameters
from
several
sources.
Dust
generated
as
a
result
of
applying
the
fertilizer
is
based
on
USEPA
equations
for
dumping
soils.
Specifically,
dust
generated
as
a
result
of
preparing
the
fertilizer
for
application
was
modeled
using:
a
"
box
model"
to
simulate
loading
the
fertilizer
spreader;
an
application
emission
rate
of
8.4
x
10­
4
kg
dust
/
metric
ton;
the
assumption
that
exposure
during
loading
is
most
likely
to
occur
in
a
small
area;
and
several
additional
assumptions
regarding
the
particular
exposure
scenario
(
e.
g.,
time
required
for
loading,
application
rate,
etc.).
Development
of
the
air
concentrations
of
fertilizer
dust
is
presented
in
Appendix
A.

There
are
insufficient
data
available
for
the
required
input
parameters
(
USEPA
1995b)
to
model
aerosol
concentrations
of
MOPCs.
In
the
absence
of
modeled
data,
the
assumption
was
made
that
aerosol
concentrations
are
similar
to
dust
concentrations,
in
both
the
lawn
care
and
the
farm
worker
scenarios.
The
implications
of
this
assumption
to
the
RBC
values
are
addressed
in
the
uncertainties
section
of
this
report.

4.0
TOXICITY
EVALUATION
In
developing
the
RBCs,
the
toxicity
of
metals
are
evaluated
for
both
cancer
and
non­
cancer
endpoints.
Toxicity
values
were
taken
from
USEPA's
online
Integrated
Risk
Information
System
(
IRIS)
(
USEPA
1999).
13
The
oral
and
dermal
toxicity
values
are
presented
in
Tables
3
and
the
inhalation
toxicity
values
are
presented
in
Table
4.
Toxicity
values
are
generally
available
from
USEPA
for
the
oral
and
inhalation
routes
of
exposure.
Dermal
toxicity
values
were
developed
by
converting
the
oral
toxicity
values
from
an
administered
to
an
absorbed
dose
per
USEPA
standard
guidance
(
by
multiplying
the
fraction
of
MOPC
that
is
absorbed
in
the
gastrointestinal
tract
[
GI
ABS]
by
the
oral
toxicity
value
for
RfDs
and
dividing
by
the
GI
ABS
for
CSFs).
GI
ABS
values
are
also
presented
in
Table
3.
These
values
were
taken
from
the
chemical
specific
Agency
for
Toxic
Substance
Disease
Registry
(
ATSDR)
profiles.

4.1
Carcinogenic
Effects
For
MOPCs
exhibiting
carcinogenic
potential,
cancer
slope
factors
(
SF)
are
developed
by
USEPA's
Carcinogen
Risk
Assessment
Verification
Endeavor
Work
Group
(
CRAVE).
These
slope
factors
are
developed
from
chronic
animal
studies
or
where
possible
human
epidemiological
data,
and
represent
the
excess
lifetime
cancer
risk
associated
with
various
levels
of
exposure.
Cancer
slope
factors
are
expressed
as
in
terms
of
dose
in
units
of
(
mg
chemical/
kg
body
weight/
day)­
1.
They
describe
the
upper
bound
increase
in
an
individual's
risk
of
developing
cancer
over
a
70­
year
lifetime
per
unit
of
exposure
or
dose,
where
the
unit
of
acceptable
exposure
is
expressed
as
mg
chemical/
kg
body
weight/
day
(
mg/
kg/
day).
In
addition
to
developing
the
CSF,
USEPA
assigns
a
weight
of
evidence
classification
for
each
carcinogen,
which
are
also
provided
in
Tables
3
and
4.

4.2
Non­
Carcinogenic
Effects
Toxicity
criteria
for
chemicals
potentially
causing
noncarcinogenic
effects
are
expressed
as
references
doses
(
RfDs).
RfDs
are
expressed
in
units
of
dose
(
mg
chemical/
kg
body
weight/
day).
Chronic
RfDs
are
developed
to
be
protective
for
long­
term
exposure
to
a
chemical
(
for
example
greater
than
7
years
of
exposure).
To
derive
an
RfD
a
series
of
professional
judgements
are
made
to
assess
the
quality
and
relevance
of
the
human
or
animal
data
and
to
identify
the
critical
study
and
the
toxic
effect.
A
toxicity
level
from
the
critical
study,
preferably
the
highest
noobservable
adverse­
effect
level
(
NOAEL),
is
used.
For
each
uncertainty
associated
with
the
NOAEL,
a
standardized
factor
is
applied
to
establish
a
margin
of
safety.
The
oral,
dermal,
and
inhalation
toxicity
values
are
presented
in
Tables
3
and
4.

4.3
Toxicity
Value
for
Lead
No
RfD
or
CSF
has
been
established
for
lead
and
some
data
suggest
that
a
threshold
for
lead
toxicity
does
not
exist
(
ATSDR
1993).
The
general
consensus
on
evaluating
lead
exposure
and
toxicity
is
through
measuring
blood
lead
levels
(
NAS
1980).
USEPA
and
ATSDR
recommend
a
fetal
acceptable
blood
lead
concentration
of
10
µ
g/
dL
(
PbB
fetal,
0.95,
goal).
This
level
is
as
an
upper
limit
indicator
below
which
no
adverse
effects
would
be
expected.
The
USEPA
Technical
Review
Workgroup
for
Lead
(
TRW)
has
developed
guidance
for
determining
risks
associated
with
non­
residential
adult
exposure
to
lead
in
soil
(
USEPA
1996b).
The
USEPA
approach
for
developing
acceptable
concentrations
for
blood
lead
was
used
in
developing
the
acceptable
blood
lead
concentration.
14
The
acceptable
fetal
blood
lead
level
of
10
µ
g/
dL
is
used
to
develop
a
target
blood
lead
concentration
(
PbB
a,
c,
g)
for
adults,
which
represents
the
risk­
based
goal
for
central
estimate
of
blood
lead
concentrations
in
adult
women
that
ensures
the
fetal
blood
lead
concentration
goal
is
not
exceeded.
This
PbB
a,
c,
g
is
calculated
using
the
following
equation:

PbB
PbB
GSD
R
a
c
g
fetal
goal
i
adult
fetal
maternal
,
,
,
.
,

,
.
/
*
=
0
95
1
645
where:
PbB
a,
c,
g
=
Blood
Lead
Level
Central
Goal
for
Adult
PbB
fetal,
0.95,
goal
=
95
Percentile
Fetal
Blood
Lead
Goal
(
10
µ
g/
dL);

=
Geometric
Standard
Deviation
for
Blood
Lead
GSD
i
adult
,
.
1
645
Concentrations
Among
Adults
(
2.1
µ
g/
dL,
recommended
by
TRW
when
considering
an
industrial
population
assumes
heterogeneity);

=
The
Constant
of
Proportionality
Between
Fetal
Blood
Lead
R
fetal
maternal
/

Concentration
at
Birth
and
Maternal
Blood
Lead
Concentration
(
0.9).

PbB
a,
c,
g
is
calculated
to
equal
3.28
µ
g/
dL.
This
target
blood
level
is
adjusted
downward
to
account
for
daily
baseline
exposures
to
lead
from
air,
water,
and
food.
An
average
baseline
blood
lead
level
of
1.95
µ
g/
dL
(
also
from
USEPA
1996b)
is
subtracted
from
the
acceptable
blood
level
to
yield
a
revised
acceptable
blood
lead
level
of
1.33
µ
g/
dL
(
referred
to
as
PbB
a,
a).
In
addition,
USEPA
has
a
recommended
biokinetic
slope
factor
(
BKSF)
for
lead
of
0.4
µ
g/
dL
per
µ
g/
day.
Both
of
these
values
are
used
in
calculating
the
RBC
(
as
presented
below).
The
RBC
is
adjusted
to
an
absorbed
dose
by
multiplying
by
absorption
values
specific
to
the
route
of
exposure.
These
absorption
values
are
presented
in
Table
5.

5.0
CALCULATION
AND
PRESENTATION
OF
RISK
BASED
CONCENTRATIONS
(
RBCs)

The
algorithms
that
were
used
to
calculate
the
RBCs,
along
with
how
the
RBCs
should
be
used
in
evaluating
the
potential
for
health
risks
to
fertilizer
applicators,
are
presented
in
this
section.

5.1
Calculation
of
the
RBC
In
general,
the
standard
USEPA
algorithms
for
calculating
RBCs
were
used
for
each
exposure
pathway.
These
equations
were
mathematically
combined
into
one
algorithm
for
ease
in
computation
of
the
aggregate
exposure.
15
The
RBCs
were
calculated
using
the
following
equations:

for
carcinogens,
RBC
(
mg
MOPC/
kg
fertilizer)
=

(
)
(
)
(
)
(
)
AT
BW
TR
EF
ED
FOD
CF
SA
AF
ABS
SF
IRf
SF
IR
AC
SF
d
o
a
i
*
*
*
*
*
*
*
*
+
*
+
*
*
for
noncarcinogens,
RBC
(
mg
MOPC/
kg
fertilizer)
=

(
)
(
)
(
)
(
)
ATnc
BW
TR
EF
ED
FOD
CF
SA
AF
ABS
RfD
IR
RfD
IR
AC
RfD
d
f
o
a
i
*
*
*
*
*
*
*
*
+
*
+
*
*
1
1
1
/
/
/

for
lead
RBC,
(
mg
lead/
kg
fertilizer)
=

(
)
(
)
(
)
(
)
PbB
ATnc
BKSF
EF
ED
FOD
CF
SA
AF
ABS
IR
ABS
IR
ABS
AC
a
a
f
o
a
i
,

/
,
*
*
*
*
*
*
*
*
+
*
+
*
*
1
1000
m
g
/
mg
where:

BW
=
Body
Weight
(
kg);
TR
=
Acceptable
Target
Risk
for
Cancer
and
Hazard
Index
for
Noncancer;
AT
=
Averaging
Time
(
days)
(
carcinogens
=
70
years
or
25,550
days
and
noncarcinogens
(
nc)
=
ED
*
365
days/
year);
EF
=
Exposure
Frequency
(
days/
year);
ED
=
Exposure
Duration
(
years);
(
30
years);
FOD
=
Fraction
of
Day
Potentially
Exposed
to
Fertilizer
(
unitless);
SA
=
Surface
Area
(
cm2/
day)
of
skin;
AF
=
Adherence
Factor
(
mg/
cm2);
ABS
=
Dermal
Absorption
of
MOPC
across
the
skin
(
unitless);
ABS
i
=
Respiratory
Tract
Absorption
of
Lead
(
unitless);
CF
=
Conversion
Factor
(
kg/
mg);
IR
f
=
Ingestion
Rate
of
Fertilizer
(
mg/
day);
IR
a
=
Inhalation
Rate
(
m3/
day);
AC
=
Modeled
Air
Concentration
of
Fertilizer
(
mg/
m3);
SF
=
Cancer
Slope
Factor;
RfD
=
Reference
Dose;
PbB
aa
=
Acceptable
Blood
Level
for
Adults;
BKSF
=
Biokinetic
Slope
Factor
for
Lead;
o
=
Ingestion;
d
=
Dermal;
and
i
=
Inhalation.
16
USEPA's
National
Contingency
Plan
(
40
CFR
Part
300,
National
Oil
and
Hazardous
Substances
Pollution
Contingency
Plan,
Final
Rule)
defines
an
acceptable
individual
cancer
risk
range
for
decision
making
purposes
between
1x10­
6
and
1x10­
4.
USEPA's
recommended
target
risk
(
TR)
based
on
an
occupational
setting
for
cancer
and
target
hazard
index
for
noncancer
were
used
for
this
screening.
USEPA
uses
an
acceptable
target
cancer
risk
of
1
in
100,
000
or
1
x
10­
5
for
recommended
soil
cleanup
levels
(
USEPA
1991;
USEPA
1996a).
The
USEPA
standard
acceptable
target
hazard
index
for
noncancer
is
1
(
USEPA
1991).
The
cancer
and
noncancer
RBCs
for
each
scenario
and
MOPC
are
presented
in
Table
6.
The
lower
of
the
noncancer
RBC
or
the
cancer
RBC
is
selected
for
each
MOPC.

5.2
How
the
RBCs
Should
be
Used
to
Screen
Specific
Fertilizer
Products
The
procedure
described
above
results
in
the
development
of
RBC
values
for
each
of
the
four
MOPCs
(
arsenic,
cadmium,
lead
and
mercury).
These
RBCs
are
presented
in
Table
6.
Recall
that
an
RBC
is
the
amount
or
concentration
of
the
MOPC
in
fertilizer
that
is
considered
health
protective
for
a
particular
exposure
scenario.
The
RBCs
are
developed
using
conservative
assumptions
regarding
exposure
and
toxicity
in
order
that
risks
are
not
underestimated.
This
is
standard
practice
for
screening­
level
assessments.
There
are
four
RBC
values
for
each
MOPC
corresponding
to
the
four
selected
exposure
scenarios,
which
are:


farm
worker
applying
phosphate
fertilizer

farm
worker
applying
micronutrient
fertilizer

lawn
care
professional
applying
phosphate
fertilizer

lawn
care
professional
applying
micronutrient
fertilizer
A
screening­
level
determination
of
whether
a
particular
fertilizer
product
(
or
product
category)
poses
a
potential
health
risk
to
applicators
is
accomplished
by
comparing
the
measured
concentration(
s)
of
a
MOPC
(
e.
g.
cadmium)
in
the
product
(
or
product
category)
to
the
most
appropriate
RBC
for
that
same
MOPC.
Phosphate
RBCs
need
to
be
compared
to
MOPC
concentrations
in
phosphate
products,
and
micronutrient
RBCs
need
to
be
compared
to
MOPC
concentrations
in
micronutrient
products.
If
a
product
is
used
on
both
lawns
and
crops,
then
the
comparison
should
be
made
to
the
lower
RBC
value,
which
is
the
RBC
for
the
lawn
care
professional
(
lawn
care
professional
has
the
highest
potential
for
exposure).
If
the
product
is
only
used
on
crops,
then
the
comparison
should
be
made
to
the
RBC
value
for
the
farm
worker.

Table
7
presents
the
RBCs
that
should
be
used
for
such
a
screening­
level
comparison.
The
RBCs
are
reported
in
mg
nutrient
/
kg
product.
The
concentrations
of
the
MOPCs
in
products
must
be
in
the
same
units
to
make
a
direct
comparison.
If
the
concentration
of
the
MOPC
in
the
fertilizer
is
below
the
RBC,
there
is
no
health
risk
to
applicators
from
handling
the
product.
If
the
concentration
of
the
MOPC
in
the
fertilizer
is
above
the
RBC,
further
evaluation
is
warranted.
An
exceedence
of
a
screening­
level
RBC
does
not
necessarily
indicate
there
is
a
health
risk
because,
the
RBCs
are
conservatively
derived
to
ensure
that
health
risks
are
not
underestimated.
A
firm
conclusion
regarding
health
risks,
in
the
case
of
an
RBC
exceedence,
therefore,
requires
a
closer
evaluation.
17
A
closer
evaluation
could
involve
several
steps,
each
intended
to
adjust
the
RBC
value
to
more
closely
reflect
the
actual
exposure
scenario
conditions.
A
first
step
is
the
adjustment
of
the
RBC
to
reflect
the
actual
fraction
of
the
nutrient
(
i.
e.,
phosphate
or
micronutrient)
in
the
fertilizer.
As
indicated
when
describing
the
process
for
deriving
the
RBC
values,
the
RBCs
assume
that
the
MOPC
is
in
100%
of
the
fertilizer,
when
in
fact,
the
MOPC
is
actually
associated
with
a
fraction
of
the
fertilizer.
For
example,
the
percent
P2O5
in
a
fertilizer
applied
to
the
soil
is
not
100%,
but
rather,
varies
by
product;
the
percent
is
given
in
the
N­
P­
K
ratio.
The
RBC
can
be
adjusted
to
reflect
the
actual
percent
of
nutrient
in
the
fertilizer
by
dividing
the
RBC
by
the
fraction
of
nutrient
that
contains
the
MOPC.
For
macronutrient
fertilizers,
it
is
the
phosphate
component,
for
micronutrient
fertilizers,
it
is
the
principal
micronutrient
component
(
e.
g.
zinc
or
iron).
If,
for
example,
the
percent
of
P2O5
is
20%
in
a
macronutrient
product,
then
the
RBC
value
is
adjusted
upward
by
a
factor
of
5.

Another
step
in
a
closer
evaluation
is
selecting
the
RBC
that
best
reflects
the
actual
conditions
surrounding
the
intended
use
of
the
product.
In
the
same
manner
as
deciding
whether
to
use
the
RBC
for
the
lawn
care
professional
or
the
farm
worker,
there
may
be
other
aspects
of
the
exposure
parameters
that
are
known,
and
that
should
be
adjusted
for
specific
conditions.
These
might
include
exposure
frequency
(
number
of
days
per
year),
fraction
of
day,
exposure
duration
(
number
of
years),
and
protective
measures
that
reduce
the
exposed
surface
area
of
the
skin.
An
RBC
that
best
reflects
the
actual
use
conditions
of
the
product
will
provide
the
best
evaluation
of
potential
health
risk.

6.0
UNCERTAINTY
ANALYSIS
Each
step
in
the
developing
the
RBCs
has
some
inherent
uncertainty
associated
with
it.
These
uncertainties
are
evaluated
to
provide
an
indication
of
the
relative
degree
that
the
uncertainty
may
underestimate
or
overestimate
the
RBC,
and
therefore,
the
risks.
An
assessment
of
the
major
uncertainties
associated
with
the
RBC
calculations
is
presented
in
Table
8.

The
purpose
of
this
document
is
to
provide
fertilizer
manufacturers,
applicators,
and
interested
regulators
with
an
easy
tool
to
evaluate
whether
the
concentrations
of
select
non­
nutrient
elements,
in
a
particular
commercial
inorganic
fertilizer,
may
pose
a
health
risk
to
the
applicator.
These
RBCs
were
calculated
based
on
"
high­
end
values"
purposely
selected
to
account
for
the
inherent
uncertainty
associated
with
each
parameter.
They
are
therefore,
more
likely
to
be
overrather
than
under­
protective
of
human
health,
and
the
uncertainty
analysis
supports
this
conclusion.

7.0
SUMMARY
In
summary,
screening­
level
RBCs
were
derived
for
two
representative
exposure
scenarios,
one
"
low
end"
exposure
scenario,
a
farm
worker,
and
one
"
high
end"
exposure
scenario,
a
lawn
care
professional.
The
RBC
values,
which
are
presented
as
mg
MOPC
/
kg
fertilizer,
are
lower
for
the
lawn
care
professional
corresponding
to
higher
anticipated
exposures.
Within
each
scenario,
RBCs
were
calculated
for
two
general
classes
of
inorganic
fertilizers,
macronutrients
(
specifically
phosphate
fertilizers)
and
micronutrient
fertilizers
for
four
MOPCs:
arsenic,
cadmium,
lead
and
mercury.
The
RBC
values
are
presented
in
Table
7.
18
The
RBCs
can
be
used
to
screen
for
potential
health
risks
by
comparing
the
measured
MOPC
content
of
a
fertilizer
product
(
in
mg
MOPC
/
kg
fertilizer)
to
its
corresponding
RBC
in
the
same
units.
Phosphate
fertilizers
are
compared
with
phosphate
RBCs,
and
micronutrient
fertilizers
with
micronutrient
RBCs.
If
the
MOPC
concentration
of
the
product
is
less
than
the
RBC,
the
product
does
not
pose
a
health
risk
to
applicators.
If
the
MOPC
concentration
of
the
product
is
greater
than
the
RBC,
a
closer
evaluation
of
the
assumptions,
including
an
adjustment
for
the
actual
percentage
of
the
nutrient
that
contains
the
MOPC
(
i.
e.,
divide
the
RBC
by
the
fraction
of
nutrient
that
contains
the
MOPC)
should
be
conducted,
and
an
RBC
that
best
reflects
the
intended
use
should
be
selected.
Lastly,
the
RBCs
could
be
adjusted,
if
needed,
to
reflect
a
scenario
that
better
fits
the
intended
use
of
the
product.
This
adjustment
would
involve
replacing
the
default
exposure
parameters
with
actual
values
that
are
representative
of
the
specific
product
and
application
conditions.
19
8.0
REFERENCES
American
Agricultural
Economics
Association
(
AAEA).
1998.
Commodity
costs
and
returns
estimation
handbook.

Agency
for
Toxic
Substances
and
Disease
Registry
(
ATSDR).
1992.
Toxicological
profile
for
arsenic.

Agency
for
Toxic
Substances
and
Disease
Registry
(
ATSDR).
1993.
Toxicological
profile
for
lead.

Agency
for
Toxic
Substances
and
Disease
Registry
(
ATSDR).
1998.
Toxicological
profile
for
mercury.

California
Department
of
Food
and
Agriculture
(
CDFA).
1998.
Development
of
risk­
based
concentrations
for
arsenic,
cadmium,
and
lead
in
inorganic
commercial
fertilizers.

Industry
Communication.
1999a.
Personal
communication
between
The
Weinberg
Group
Inc.
and
manager
of
a
golf
course
in
Maine
and
in
Florida.

Industry
Communication.
1999b.
Personal
communication
between
The
Weinberg
Group
Inc.
and
manager
of
a
professional
lawn
care
company
in
southern
California.

National
Academy
of
Science
(
NAS).
1980.
Lead
in
the
human
environment.
Committee
of
Lead
in
the
Human
Environment.
Washington,
D.
C.

United
States
Department
of
Agriculture
(
USDA).
1997.
Farms
and
land
in
farms.
Final
estimates
1993­
1997.
National
Agriculture
Statistics
Service.
Statistical
Bulletin
Number
955.

United
States
Environmental
Protection
Agency
(
USEPA).
1999.
Integrated
risk
information
system
(
IRIS)
for
arsenic,
cadmium,
and
mercury.
Accessed
on
line
on
January
24,
1999.

United
States
Environmental
Protection
Agency
(
USEPA).
1998.
Risk
assessment
guidance
for
superfund,
Volume
I:
human
health
evaluation
manual,
supplemental
guidance,
dermal
risk
assessment
interim
guidance.

United
States
Environmental
Protection
Agency
(
USEPA).
1997a.
Exposure
factors
handbook.
Volumes
I,
II,
and
III.
EPA/
600/
P­
95/
002Fa,
b,
c.

United
States
Environmental
Protection
Agency
(
USEPA).
1997b.
Standard
operating
procedures
(
SOPs)
for
residential
exposure
assessments.
Draft,
prepared
by
the
Residential
Exposure
Assessment
Group
(
Office
of
Pesticide
Programs,
Health
Effects
Division,
and
Versar,
Inc.).
Contract
No.
68­
W6­
0030,
Work
Assignment
No.
3385,102.
December
18.

United
States
Environmental
Protection
Agency
(
USEPA).
1996a.
Soil
screening
guidance:
users
guide.
Office
of
Solid
Waste
Emergency
Response,
Washington,
D.
C.,
EPA/
540/
R­
69/
018.
20
United
States
Environmental
Protection
Agency
(
USEPA).
1996b.
Recommendations
of
the
technical
review
workgroup
for
lead
for
an
interim
approach
to
assessing
risks
with
adult
exposures
to
lead
in
soil.
December
1996.

United
States
Environmental
Protection
Agency
(
USEPA).
1995a.
Guide
to
the
biosolids
risk
assessments
for
the
EPA
part
503
rule.

United
States
Environmental
Protection
Agency
(
USEPA).
1995b.
Compilation
of
air
pollutant
emission
factors,
Volume
I:
stationary
point
and
area
sources,
fifth
edition.
AP
42:
9.2.2.

United
States
Environmental
Protection
Agency
(
USEPA).
1991.
Risk
assessment
guidance
for
superfund:
Volume
I:
human
health
evaluation
manual
(
part
B,
development
of
risk­
based
preliminary
remediation
goals).

United
States
Environmental
Protection
Agency
(
USEPA).
1989.
Risk
assessment
guidance
for
superfund:
Volume
I:
human
health
evaluation
manual.

The
Weinberg
Group
Inc.
1998.
Industry
and
literature
survey
of
nutritive
&
non­
nutritive
elements
in
inorganic
fertilizer
materials.
Prepared
for
The
Fertilizer
Institute,
Washington,
D.
C.,
December
16,
1998.
TABLE
1
QUALITATIVE
EVALUATION
OF
THE
EXPOSURE
POTENTIAL
ASSOCIATED
WITH
MAJOR
EXPOSURE
FACTORS
FOR
TYPICAL
FERTILIZER
APPLICATORS
Exposure
Factor
Exposure
Potential
(
a)

Residential
Applicator
Professional
Applicators
Lawn
Care
Golf
Course
Nursery
Farmer
Amount
of
Fertilizer
Applied
(
b)
Low
Low
to
Medium
Medium
to
High
Low
to
Medium
Medium
to
High
Frequency
of
Application
(
c)
Low
Medium
to
High
Low
to
High
Low
to
Medium
Low
to
Medium
Mode
of
Application
(
d)
Medium
to
High
Low
to
High
Low
to
Medium
Medium
to
High
Low
to
Medium
Form
of
Fertilizer
(
e)
Low
to
Medium
Low
to
Medium
Low
to
Medium
Low
to
Medium
Low
to
High
Protective
Clothing
Worn
During
Application
(
f)
Low
to
High
Medium
to
High
Medium
to
High
Low
to
Medium
Low
to
Medium
Overall
Potential
for
Exposure
(
g)
Low
Medium
to
High
Low
to
High
Low
to
Medium
Low
to
Medium
(
a)
"
low",
"
medium"
and
"
high"
indicate
the
relative
exposure
potentials
among
the
types
of
applicators
for
the
given
exposure
factor.
(
b)
Considerations
include
the
application
rate,
which
varies
from
product
to
product,
the
nutrient
needs
of
the
plants,
and
the
size
of
the
application
area.
(
c)
Considerations
include
the
plants
nutrient
needs,
climate,
and
the
demands
on
the
applicator
(
e.
g.
home
gardener
or
commercial
position).
(
d)
Ranges
from
hand
applied
to
simple
and/
or
complex
machinery
that
may
be
designed
to
minimize
exposure.
(
e)
Fertilizers
may
be
in
granular
or
liquid
form,
and
may
be
bagged
or
in
bulk.
(
f)
What
is
considered
normal
and
customary.
(
g)
Qualitative
summation
of
the
individual
exposure
factors,
acknowledged
to
be
subjective.
TABLE
2
EXPOSURE
PARAMETERS
AND
ASSUMPTIONS
FOR
FERTILIZER
APPLICATOR
RISK
BASED
CONCENTRATIONS
(
RBCs)

RBC
Cancer
=
AT*
BW*
TR/
EF*
FOD*
ED*
CF((
SA*
AF*
ABS*
SFd)+(
IRf*
SFo)+(
IRa*
AC*
SFi))

RBC
Noncancer
=
AT*
BW*
TR/
EF*
FOD*
ED*
CF((
SA*
AF*
ABS*
1/
RfDd)+(
IRf*
1/
RfDo)+(
IRa*
AC*
1/
RfDi))

Parameter
Farm
Lawn
Care
Code
Parameter
Definition
Units
Worker
Source
Professional
Source
All
Pathways
TR
Acceptable
Target
Risk
or
Hazard
Quotient
unitless
cancer
1.0E­
05
USEPA
1991;
USEPA1996a
(
a)
1.0E­
05
USEPA
1991;
USEPA
1996a
(
a)

noncancer
1
USEPA,
1991
1
USEPA
1991
EF
Exposure
Frequency
days/
year
phosphate
22
USDA
1997,
CDFA
1998
(
b)
200
BPJ
(
c)

micronutrient
11
(
b)
100
BPJ
(
c)

ED
Exposure
Duration
years
30
USEPA
1997
30
USEPA
1997
BW
Body
Weight
kg
70
USEPA
1997
70
US
EPA
1997
AT­
C
Averaging
Time
(
Cancer)
days
25,550
USEPA
1997
25,550
US
EPA
1997
AT­
N
Averaging
Time
(
Noncancer)
days
10,950
ED*
365
10,950
ED*
365
FOD
Fraction
of
Day
Exposed
to
Fertilizer
unitless
0.2
CDFA
1998
(
d)
0.5
BPJ
(
e)

CF
Conversion
Factor
kg/
mg
1.0E­
06
­­
1.0E­
06
­­

Ingestion
IRf
Fertilizer
Ingestion
Rate
mg/
day
50
USEPA
1997
(
f)
50
USEPA
1997
(
f)

Dermal
Contact
SA
Exposed
Skin
Surface
Area
cm2/
day
5750
CDFA
1998
(
g)
5700
USEPA
1998
(
h)

AF
Adherence
Factor
mg/
cm2
0.03
USEPA
1998
0.03
USEPA
1998
(
h)

ABS
Absorption
Factor
unitless
see
Table
5
metal
specific
see
Table
5
metal
specific
Inhalation
of
Dust
or
Aerosol
AC
Modeled
Air
Concentration
(
i)
mg/
m3
0.0041
Modeled
0.0002
Modeled
IRa
Inhalation
Rate
for
Air
m3/
day
20
USEPA
1997
20
US
EPA
1997
­­
Not
Applicable
BPJ
Best
Professional
Judgement
RBC
Risk
Based
Concentration
(
a)
Based
on
the
acceptable
target
cancer
risk
of
1
in
a
one
hundred
thousand
(
1x10
­
5)
for
occupational
(
i.
e.,
industrial)
exposures.

(
b)
Exposure
frequency
is
based
on
the
use
of
the
low
end
of
the
estimated
rate
of
completion
reported
by
industry
professionals
=
20­
30
acres/
day,
and
the
estimated
farm
size
utilized
for
the
analysis
=
436
acres
(
discussed
in
detail
in
Section
3.0).
Because
the
micronutrient
needs
of
crops
are
much
less
than
the
phosphate
needs,
the
exposure
frequency
for
micronutrient
fertilizer
is
half
the
exposure
frequency
for
phosphate
fertilizer.

(
c)
Based
on
the
assumption
that
a
lawn
care
professional
applies
fertilizer
every
work
day
(
250
work
days/
year)

and
that
80%
of
the
time
(
200
days/
year)
they
apply
fertilizer
that
contains
phosphate.
Based
on
conversations
with
industrial
professionals,

the
micronutrients
needs
of
grass
are
much
less
than
the
macronutrients.
To
account
for
this
difference,
the
number
of
days
a
year
micronutrient
fertilizer
is
applied
is
half
the
number
of
days
a
macronutrient
fertilizer
is
applied.

(
d)
Based
on
reports
from
industrial
professionals
that
predominant
fertilizer
exposure
occurs
only
during
the
loading
of
a
spreader.
Using
high
end
estimated
time
needed
to
load
a
fertilizer
spreader
(
10
minutes)
and
the
estimated
number
of
loads
delivered
(
10)
=
100
minutes
=
1.7
hours/
8
hours
or
approximately
20%.

(
e)
Based
on
the
reasonable
assumption
that
4
hours
of
the
8
hour
work
is
spent
actually
applying
fertilizer.

(
f)
In
the
absence
of
a
fertilizer
ingestion
rate,
or
a
mouth
to
hand
transfer
rate,
the
USEPA
recommended
soil
ingestion
rate
was
used.

(
g)
Calculated
dermal
skin
surface
area
for
a
farm
worker
presented
in
CDFA
1998.
Assumes
that
25%
of
the
total
skin
surface
area
(
23,000
cm
2/
day)
is
actually
exposed.

(
h)
Represents
the
sum
of
the
surface
area
for
lower
legs,
forearms,
hands,
and
head.

(
i)
The
dust
concentration
was
modeled
using
the
standard
USEPA
box
model,
the
application
emission
rate
presented
in
CDFA
1998
of
8.84
E
­
4
kg/
metric
ton,
and
high
end
assumptions
about
each
scenario
(
presented
in
detail
in
Section
3.0
and
Appendix
A).
TABLE
3
ORAL
AND
DERMAL
TOXICITY
CRITERIA
FOR
METALS
OF
POTENTIAL
CONCERN
(
MOPCs)

Gastrointestinal
Noncancer
Toxicity
Criteria
Cancer
Toxicity
Criteria
Metal
of
Absorption
Fraction
Oral
Dermal
Oral
Dermal
Tumor
Type
Potential
Concern
RfD
RfD
(
a)
Safety
Target
Slope
Factor
Slope
Factor
or
(
MOPC)
Value
Source
(
mg/
kg­
day)
(
mg/
kg­
day)
Factor
Organ
Source
(
mg/
kg­
day)­
1
(
mg/
kg­
day)­
1
(
a)
Target
Tissue
WOEC
Source
Arsenic
1
IRIS
3.0E­
04
3.0E­
04
3
skin
IRIS
1.5E+
00
1.5E+
00
skin
A
IRIS
Cadmium
(
food)
0.05
USEPA
1998
1.0E­
03
5.0E­
05
10
kidney
IRIS
­­
­­
­­
­­
­­

Lead
­­
­­
10
ug/
dL
acceptable
fetal
blood
lead
level
and
0.4
ug/
dL
per
ug/
day
biokinetic
slope
factor
USEPA
1996b
Mercury
(
elemental)
0.02
ATSDR
1998
(
b)
8.60E­
05
1.7E­
06
­­
­­
(
c)
­­
­­
­­
­­
­­

­­
No
Data
Available
ATSDR
Agency
for
Toxic
Substance
Disease
Registry
IRIS
USEPA's
Integrated
Risk
Information
System
(
1/
4/
99)

RfD
Reference
Dose
WOEC
Weight
of
Evidence
Classification
(
a)
The
dermal
toxicity
criteria
is
calculated
from
the
oral
toxicity
criteria
by
adjusting
the
oral
toxicity
criteria,
which
is
an
administered
dose,
to
an
absorbed
dose
by
multiplying
by
the
gastrointestinal
absorption
(
GI
ABS)
fraction
for
the
RfD
and
dividing
by
the
GI
ABS
fraction
for
the
slope
factor.

(
b)
Based
on
oral
administration
of
mercuric
chloride
in
mice.
A
1%
GI
absorption
value
was
also
reported.

(
c)
Route
to
route
extrapolation.
TABLE
4
INHALATION
TOXICITY
CRITERIA
FOR
METALS
OF
POTENTIAL
CONCERN
(
MOPCs)

Noncancer
Toxicity
Criteria
Cancer
Toxicity
Criteria
Metal
of
Tumor
Type
Weight
of
Potential
Concern
Reference
Dose
Safety
Target
Slope
Factor
or
Evidence
(
MOPC)
(
mg/
kg­
day)
Factor
Organ
Source
(
mg/
kg­
day)­
1
Target
Tissue
Classification
Source
Arsenic
3.0E­
04
­­
­­
(
b)
1.5E+
01
respiratory
tract
A
IRIS
Cadmium
(
food)
1.0E­
03
­­
­­
(
b)
6.3E+
00
lung
B1
IRIS
Lead
­­
USEPA
1996b
Mercury
8.6E­
05
30
CNS
IRIS
­­
­­
D
IRIS
­­
No
Data
Available
IRIS
USEPA's
Integrated
Risk
Information
System
(
1/
4/
99)

(
b)
Based
on
Route
to
Route
Extrapolation.

(
a)
The
reported
toxicity
value
was
calculated
from
a
reference
concentration
(
RfC)
or
inhalation
unit
risk
assuming
a
70­
kg
individual
inhales
20
m
3
of
air
per
day.

10
ug/
dL
acceptable
fetal
blood
lead
level
and
0.4
ug/
dL
per
ug/
day
biokinetic
slope
factor
Metal
of
Potential
Concern
Absorption
(
MOPC)
(
percent)
Fraction
Source
Dermal
Arsenic
3
0.03
USEPA
1998
Cadmium
(
food)
1
0.01
USEPA
1998
Lead
1
0.01
USEPA
1998
Mercury
1
0.01
USEPA
1998
Inhalation
Lead
50
0.5
ATSDR
1993
(
a)
Ingestion
Lead
12
(
b)
0.12
USEPA
1996b
­­
Not
Applicable
(
a)
Based
on
absorption
into
the
respiratory
tract
following
deposition.
(
b)
Oral
absorption*
Oral
bioavailability
for
soluble
lead
compared
to
lead
in
soil.
TABLE
5
DERMAL
ABSORPTION
VAULES
FOR
METALS
OF
POTENTIAL
CONCERN
(
MOPCs)
and
ROUTE
SPECIFIC
ABSORPTION
VALUES
FOR
LEAD
TABLE
6
RISK
BASED
CONCENTRATIONS
(
RBCs)
FOR
FERTILIZER
APPLICATOR
SCENARIOS
ORAL
INHALATION
DERMAL
Slope
Slope
Slope
Dermal
RBC
(
mg
MOPC/
kg
fertilizer)

Factor
Factor
Factor
Absorption
OR
OR
OR
Factor
Farm
Worker
Lawn
Care
Professional
Reference
Dose
Reference
Dose
Reference
Dose
(
ABS)
Micronutrient
Phosphate
Micronutrient
Phosphate
Oral
Slope
Inhalation
Slope
Dermal
Slope
Factor
(
SFo)
Factor
(
SFi)
Factor
(
SFd)

(
mg/
kg­
day)­
1
(
mg/
kg­
day)­
1
(
mg/
kg)­
1
Carcinogenic
Effects
Arsenic
1.5E+
0
15.0E+
0
1.5E+
0
0.030
3,200
1,600
140
72
Cadmium
­­
6.3E+
0
­­
0.010
520,000
260,000
470,000
240,000
Lead
­­
­­
­­
­­
­­
­­
­­
­­

Mercury
­­
­­
­­
0.010
­­
­­
­­
­­

Oral
Inhalation
Dermal
Reference
Reference
Reference
Dose
(
RfDo)
Dose
(
RfDi)
Dose
(
RfDd)

(
mg/
kg­
day)
(
mg/
kg­
day)
(
mg/
kg­
day)

Noncarcinogenic
Effects
Arsenic
3.
E­
04
3.
E­
04
3.
E­
04
0.030
63,000
31,000
2,800
1,400
Cadmium
1.
E­
03
1.
E­
03
5.
E­
05
0.010
140,000
69,000
6,100
3,000
Lead
(
c)
10
ug/
dL
(
d)
and
0.4
ug/
dL
per
ug/
day
0.010
71,000
35,000
3,200
1,600
Mercury
9.
E­
05
9.
E­
05
2.
E­
06
0.010
7,300
3,700
320
160
­­
Not
Applicable
(
a)
Risk­
based
acceptable
concentrations
(
RBCs)
correspond
to
lifetime
cancer
risk
of
1x10­
5
or
a
hazard
quotient
of
1.
Values
are
based
on
incidental
ingestion,
dermal
contact
and
inhalation
of
dust.

(
b)
Risk­
based
concentrations
(
RBCs)
calculated
based
on
incidental
ingestion,
dermal
contact,
and
inhalation
of
fertilizer
dust
using
the
following
equations
(
see
Section
5.0
for
definition
of
acronyms):

RBC
for
carcinogens
=
TR*
BW*
AT/
EF*
ED*
FOD*
CF((
SFo*
IRf)+(
SFd*
SA*
AF*
ABS)+(
SFi*
IRa*
AC))
;

RBC
for
non
carcinogens
=
TR*
BW*
AT/
EF*
ED*
FOD*
CF((
1/
RfDo)*
IRf)+((
1/
RfDd)*
SA*
AF*
ABS)+((
1/
RfDi)*
IRa*
AC)).

(
c)
The
RBC
for
lead
was
calculated
as
outlined
in
USEPA
1996b,
developed
by
the
Technical
Workgroup
for
lead
using
the
following
equation:

RBC
for
lead
=
PbBaa*
AT/
BKSF*
EF*
ED*
FOD*
1/
CF*
1000
ug/
mg((
IRf*
GI
ABS)+(
SA*
AF*
Dermal
ABS)+(
IRa*
AC*
Inhalation
ABS)).

(
d)
An
adult
acceptable
blood
lead
concentration
of
(
1.33
ug/
dL)
was
developed
from
the
fetal
blood
lead
level
as
outlined
in
Section
4.3.

Potential
Concern
(
MOPC)

Metal
of
Risk
Based
Concentration
Farm
Worker
Lawn
Care
Professional
Metal
of
Potential
Concern
(
MOPC)
Micronutrient
Fertilizer
Phosphate
Fertilizer
Micronutrient
Fertilizer
Phosphate
Fertilizer
Arsenic
3,200
1,600
140
72
Cadmium
140,000
69,000
6,100
3,000
Lead
71,000
35,000
3,200
1,600
Mercury
7,300
3,700
320
160
(
a)
All
RBCs
expressed
as
mg
MOPC/
kg
fertilizer.
(
RBC)
(
a)

TABLE
7
RISK
BASED
CONCENTRATIONS
(
RBCs)
FOR
SCREENING
TABLE
8
MAJOR
ASSUMPTIONS
AND
UNCERTAINTIES
ASSOCIATED
WITH
RISK
BASED
CONCENTRATIONS
(
RBCs)

Assumption
Magnitude
of
Uncertainty
and
Effect
on
Health
Assessment
Rationale
Selection
of
Metals
of
Potential
Concern
The
development
of
risk
based
concentrations
is
focused
on
four
non­
nutritive
elements
(
metals)
considered
to
have
toxicological
significance
compared
to
other
metals
found
in
inorganic
fertilizers.
Low
­
may
underestimate
risk
if
the
other
metals
were
more
toxic
or
were
at
significantly
higher
levels.
Other
metals
found
in
inorganic
fertilizers
have
lower
comparative
toxicity.

The
development
of
risk
based
concentrations
focuses
on
two
classes
of
inorganic
fertilizers,
phosphate
fertilizers
and
micronutrient
fertilizers.
Low
­
may
underestimate
risk
if
other
classes
had
higher
metal
levels.
These
classes
of
inorganic
fertilizers
tend
to
contain
higher
levels
of
the
metals
of
potential
concern.

Exposure
Assessment
RBCs
were
developed
assuming
that
the
nonnutrient
element
is
distributed
throughout
100%
of
the
fertilizer.
Medium
­
may
overestimate
risk
for
all
products.
The
non­
nutrient
element
of
the
fertilizer
is
predominantly
associated
with
the
phosphate
or
micronutrient
(
e.
g.,
zinc)
portion
of
the
fertilizer.

RBCs
were
developed
for
two
select
scenarios
considered
to
be
representative
and
health
protective
of
the
other
potential
applicator
scenarios.
Low
­
may
overestimate
risk
for
other
applicators.
The
two
scenarios
that
were
selected,
the
farm
worker
and
the
lawn
care
professional,
were
estimated
to
have
the
highest
exposure
potential.

In
the
absence
of
exposure
parameters
specific
to
fertilizer,
many
USEPA
standard
default
exposure
parameters
for
soil
were
used
(
e.
g.,
soil
ingestion
rate,
adherence
factor).
In
addition,
exposures
are
primarily
based
on
granular
fertilizer.
Low
­
may
under
or
overestimate
risk.
Exposure
to
fertilizer
in
the
granular
form
is
assumed
to
be
similar
to
soil.
Also,
exposure
to
liquid
fertilizer
is
assumed
to
result
in
similar
exposure
as
to
granular
fertilizer.

High­
end
estimates
of
exposures
were
made
for
exposure
pathways
evaluated.
Low
­
may
overestimate
risk
for
typical
scenarios.
Standard
approach
to
developing
high
end
screening
level
RBCs.

Several
parameters
were
developed
based
on
conversations
with
industry
professionals
including,
exposure
frequency
and
fraction
of
the
day
exposed.
Low
­
may
over
estimate
risk
for
other
applicators.
In
the
absence
of
a
defined
parameter,
high
end
estimates
were
made.

Potential
exposure
for
the
farm
worker
is
assumed
to
occur
primarily
during
loading
activities.
Low
­
may
underestimate
risk.
Exposure
to
farm
workers
during
application
was
assumed
to
be
low
because
the
mode
of
application
limits
the
potential
for
exposure.
Exposure
during
application
may
occur,
but
is
probably
minimal.

The
lawn
care
worker
is
assumed
to
engage
in
activities
with
exposure
potential
half
of
the
work
day.
Exposure
through
the
inhalation
route
is
based
on
time
spent
loading
the
fertilizer
into
the
spreader.
Low
­
may
over
or
underestimate
risk.
In
the
absence
of
defined
exposure
parameters,
reasonable
assumptions
about
the
exposure
scenario.
TABLE
8
(
continued)
MAJOR
ASSUMPTIONS
AND
UNCERTAINTIES
ASSOCIATED
WITH
RISK
BASED
CONCENTRATIONS
(
RBCs)
REVISED
INTERNAL
DRAFT
Assumption
Magnitude
of
Uncertainty
and
Effect
on
Health
Assessment
Rationale
Dust
concentrations
were
modeled
using
an
application
emission
factor,
a
standard
box
model
(
assuming
an
approximate
box
size
of
6
feet
by
10
feet),
and
several
scenario
specific
assumptions
discussed
above.
Low
­
Medium
­
may
over
or
underestimate
risk.
The
dust
model
is
deliberately
conservative
and
the
exposure
parameters
that
were
used
are
high
end
values.

Potential
for
inhalation
of
aerosol
through
spraying
liquid
fertilizers
was
not
evaluated
independently.
Medium
­
may
over
or
underestimate
risk.
The
assumption
that
inhalation
of
fertilizer
dust
is
comparable
to
inhalation
of
aerosol
was
made.

Toxicity
Assessment
Conservatively
derived
USEPA
cancer
slope
factors,
chronic
reference
doses,
and
lead
biokinetic
slope
factor
are
used
to
evaluate
risk.
Medium
­
may
over
or
under
estimate
risk.
For
noncancer
effects,
combinations
of
uncertainty
factors
along
with
doseresponse
data,
often
from
laboratory
animals,
are
used
to
derive
criteria
to
protect
the
most
sensitive
human
receptors.
For
cancer
effects,
doseresponse
data
are
used
to
derive
slope
factors
that
estimate
an
upper
limit
on
risk
associated
with
a
given
exposure.
Actual
risk
could
be
much
lower.

Toxicity
criteria
for
the
dermal
exposure
of
exposure
were
derived
using
route­
to­
route
extrapolation
and
an
adjustment
to
an
absorbed
dose.
Medium
­
may
over­
or
underestimate
risk.
Depending
on
the
metal,
the
route
of
administration
or
exposure
may
change
the
toxicity.

RBCs
were
developed
assuming
risks
to
be
additive
although
they
may
be
antagonistic,
potentiating,
or
synergistic.
Low
­
may
over­
or
underestimate
risk
Recent
research
has
confirmed
the
validity
of
additivity
at
low
doses.

Risk
Based
Concentration
Calculation
The
RBCs
were
developed
with
high­
end
or
reasonable
maximum
exposures.
Medium
­
likely
to
overestimate
risk.
In
general,
screening
level
RBCs
are
purposely
based
on
a
high­
end
exposure
scenario.
APPENDIX
A
MODELED
AIR
CONCENTRATIONS
FOR
FERTILIZER
DUST
Fertilizer
dust
concentrations
were
estimated
using
a
standard
United
States
Environmental
Protection
Agency
(
USEPA)
box
model,
an
application
emission
factor
of
8.4x10­
4
kg
dust/
metric
ton
presented
in
CDFA
1998
(
based
on
dust
emissions
from
soil
dumping
activities),
and
reasonable
exposure
parameters
and
assumptions.

The
equation
used
to
calculate
the
fertilizer
dust
concentration
is:

Dust
Concentration
mg
m
AR
AA
CF
CF
CF
ER
ART
CF
W
H
U
(
/
)
*
*
*
*
*
*
/
*

*
*
3
1
2
3
1
4
=
where:

AR
=
Application
Rate
(
lbs/
acre­
year);
AA
=
Size
of
the
Area
per
Application
(
acres);
CF1
=
Conversion
Factor
1
(
g/
lb);
CF2
=
Conversion
Factor
2
(
kg/
1,000g);
CF3
=
Conversion
Factor
3
(
1x10­
3
metric
ton/
kg);
CF4
=
Conversion
Factor
4
(
1
x106
mg/
kg);
ER
=
Application
Emission
Rate
(
8.4X10­
4
kg/
metric
ton);
ART
=
Estimated
Application
Time
(
seconds
loading/
year);
W
=
Width
Box
Model
(
m)
H
=
Height
Box
Model
(
m);
U
=
Estimated
Wind
Speed
(
m/
s).

The
parameter
values
for
each
scenario
are
presented
in
Table
A­
1.
The
air
concentrations
are
modeled
based
on
application
rates
for
phosphate
fertilizers.
This
assumption
is
likely
to
be
an
over
estimate
for
the
potential
dust
generation
during
the
application
of
micronutrient
fertilizers
because
micronutrient
nutrient
fertilizers
are
expected
to
be
applied
at
considerably
lower
rates
than
phosphate
fertilizers.
This
model
assumes
the
dust
will
result
primarily
from
loading
activities.
TABLE
A­
1
FACTORS
USED
IN
MODELING
FERTILIZER
DUST
CONCENTRATIONS
FOR
FARM
WORKER
AND
LAWN
CARE
PROFESSIONAL
Factor
Descriptor
Units
Farm
Worker
Source
Lawn
Care
Professional
Source
AR
Application
Rate
lbs/
acre­
yr
55
CDFA
1998(
a)
240
BPJ;
Industry
Communication
1999
(
a)

AA
Size
of
Area
per
Application
acres
20
CDFA
1998
0.5
BPJ;
Industry
Communication
1999
(
b)

CF
1
Conversion
Factor
454
g/
lb
­­
­­
­­
­­

CF
2
Conversion
Factor
kg/
1,000
g
­­
­­
­­
­­

CF3
Conversion
Factor
metric
ton/
1,000kg
­­
­­
­­
­­

CF4
Conversion
Factor
1x106
mg/
kg
­­
­­
­­
­­

ER
Application
Emission
Rate
kg
/
metric
ton
8.4
x
10­
4
CDFA
1998
8.4
x
10­
4
­­

ART
Estimate
Application
Time
secs/
yr
13,200
CDFA
1998
(
c)
360,000
BPJ
(
d)

W
Width
of
Box
m
3.05
(
or
10
ft)
BPJ
(
e)
same
as
farm
worker
H
Height
of
Box
m
1.8
m
(
or
6
ft)
BPJ
(
f)
same
as
farm
worker
U
Average
Wind
Speed
m/
s
1.4
CDFA
1998
same
as
farm
worker
%
Not
Applicable
BPJ
Best
Professional
Judgement
(
a)
Average
of
application
rates
of
phosphate
fertilizers
for
three
crops
presented
in
CDFA
1998.
(
b)
The
average
size
of
a
lawn
is
0.5
acres.
(
c)
Calculated
based
on
the
time
a
farm
worker
spends
loading
fertilizer
reported
in
CDFA
(
1998)
of
10
minutes/
loading
and
the
estimated
number
of
days
a
farm
worker
applies
fertilizer
annually
(
22
days/
year).
(
d)
Calculated
based
on
the
time
a
lawn
care
professional
spends
loading
fertilizer
daily
(
i.
e.,
5
minute/
loading,
6
loadings/
day
[
BPJ])
and
the
estimated
number
of
days
a
lawn
care
professional
applies
fertilizer
annually
(
200
days/
year).
(
e)
Width
of
the
box
is
based
on
the
reasonable
assumption
that
the
actual
width
of
the
air
space
is
10
feet
(
or
3.05
m).
(
f)
Based
on
the
assumption
that
the
height
of
the
box
is
the
average
height
of
a
man
(
i.
e.,
6
ft).
REFERENCES
California
Department
of
Food
and
Agriculture
(
CDFA).
1998.
Development
of
risk­
based
concentrations
for
arsenic,
cadmium,
and
lead
in
inorganic
commercial
fertilizers.

Industry
Communication.
1999.
Personal
communication
between
The
Weinberg
Group
Inc.
and
manager
of
a
professional
lawn
care
company
in
southern
California.
