DRAFT  Policy

Science Advisory Council for Exposure

Policy #:  	007

Regarding:	Use of Values from the PHED Surrogate Exposure Guide and from
Analyses of 		Individual PHED Data Sets

Date:		January 28, 1999

Index terms:	PHED; Surrogate Table; surrogate data, pesticide
occupational handler exposure

ISSUE:	There is a need to assure consistency in the assessment of
occupational exposure 		to pesticide handlers in the absence of exposure
monitoring data.  This includes 		the need to know how to utilize the
surrogate data in the Pesticide Handlers 		Exposure Database (PHED). 

BACKGROUND:	

When no handler exposure data are submitted in support of a particular
pesticide action, 	an exposure assessment for each use scenario is
developed using exposure values 		calculated by the Pesticide Handlers
Exposure Database (V 1.1).   PHED data are used 	to complete an
assessment only for those scenarios where the surrogate data are deemed 
appropriate for the assessment.  PHED was designed by a task force
consisting of 		representatives from the U.S. EPA, Health Canada, the
California Department of 		Pesticide Regulation, and member companies of
the American Crop Protection 		Association.  PHED is a generic database
containing voluntarily submitted empirical 	exposure data for workers
involved in the handling or application of pesticides in the 	field
(i.e., currently contains data for over 2000 monitored exposure events).
The basic 	assumption underlying the system is that exposure to
pesticide handlers can be 		calculated generically, based on the
available empirical data for chemicals, as exposure 	is primarily a
function of the formulation type and the handling activities (e.g., 	
packaging type, mixing/loading/application method, and clothing
scenario), rather than 	chemical-specific properties.  

PHED also contains the algorithms necessary for the user to calculate
surrogate 		scenario-based unit exposures (i.e., ug exposure per lb
active ingredient handled), 	beginning with one of the four main data
files contained in the system (i.e., 		mixer/loader, applicator,
flagger, and mixer/loader/applicator).  Users can select data 	from each
major PHED file and construct unit exposure for scenarios that are 	
representative of use patterns associated with specific chemicals. 
However, to add 	consistency to the risk assessment process, the EPA in
conjunction with the PHED task 	force, has evaluated all data within the
system and developed a table that contains a 	series of standard unit
exposure values for the most common occupational exposure 	scenarios
(PHED Surrogate Exposure Guide of May, 1997).  

PHED calculates the “best fit” exposure values by assessing the
distributions of 		exposures for each body part (e.g., chest or forearm)
and then calculates a composite 	unit exposure value representing the
entire body. PHED categorizes these distributions 	as normal, lognormal,
or “other.” Generally, most data contained in PHED are 		lognormally
distributed or fall into the PHED “other” distribution category.  If
the 	distribution is lognormal, the geometric mean for the distribution
is used in the 		calculation of the “best fit” exposure value.  If
the data are an “other” distribution, the 	median value of the
dataset is used in the calculation of the “best fit” exposure value.
 	

Use of the Surrogate Exposure Guide offers certain advantages over using
subsets 	of the PHED: 1) the Guide contains more replicates for each
scenario than individual 	subsets of PHED can provide; 2) use of the
Guide results in consistency among exposure 	assessments for similar
pesticide exposure scenarios; and 3) use of the Guide is relatively 
easy and, therefore, saves resources by reducing the time spent on
analyzing individual 	data sets.   

Use of the PHED subsetting capability offers one major advantage over
using the 		summary Guide: subsetting allows the creation of tailored
data sets that more closely 	match the specific exposure scenario of
concern (forcing the Guide to cover an 		inappropriate scenario can
provide unit exposure estimates that are not meaningful 	and result in
misleading risk estimates.

It should be noted that whether using the summary table or performing a
tailored 		individual PHED analysis, there are relatively few data
points to allow a high confidence 	that the exposure of the entire
population of handlers is represented.  However, when the 	data in PHED
are all that are available, they serve as an invaluable aid in
estimating 	exposure potential.  Below are some guidelines for when to
use the PHED summary table 	and when to conduct a individualized
assessment using the data and PHED algorithm.

POLICY: 	

Use unit exposure values from the Pesticide Handlers Data Base (PHED) 	
Surrogate Exposure Guide (V 1.1 or most recent version) as a source of 	
	information solely, or in combination with other information to support
a 		particular pesticide action when no, more-applicable,
scenario-specific handler 		exposure data are submitted.   When handler
exposure data are submitted to 		support the action, these data should
be combined with the data in the 			Surrogate Exposure Guide. (See
“Pesticide Handlers Data Base Evaluation 		Guidance, PHED V 1.1,” 
March 15, 1995)

Use the PHED algorithm on individualized data subsets to support a
particular 		pesticide registration action or special review, when no,
more-applicable, 		scenario-specific handler exposure data are
submitted, and for any pesticide 		action when the exposure scenario of
concern is not adequately covered in the 		Surrogate Exposure Guide
(e.g., with atypical applications such as ultra low 		volume (ULV)
aerial application).  The PHED algorithm is based on Guideline 		Series
875 Part A.  For more detail on the algorithm, see the PHED Reference 	
Manual, V 1.1, February 1995.

  		The individualized PHED run should be accompanied by an explanation
of the 		special circumstances for which it is required.

All unit exposures derived from use of the PHED algorithm on
individualized 		data subsets (whether by HED assessors or submitted by
registrants) should be 		reviewed by an HED staff member experienced
with the data and capabilities of 		PHED (e.g., someone who can perform
an independent analysis of the same 		scenario and check for accuracy
and reasonableness of the data subsets).  		Contact the Exposure SAC
Chairperson for referral to such individuals.

When PHED data are used in a assessment, include the following language
in 		the exposure/risk characterization sections of your document:

“Chemical-specific data for assessing human exposures during pesticide
		handling activities were not submitted to the Agency in support of the
		(re)registration of {pesticide name}.  It is the policy of the HED to
use data 		from the Pesticide Handlers Exposure Database (PHED) Version
1.1 to assess 		handler exposures for regulatory actions when
chemical-specific monitoring 		data are not available.1 

-or-

Chemical-specific data for assessing human exposures during pesticide 	
handling activities were submitted to the Agencyin support of the 		
(re)registration of {pesticide name}.  It is the policy of HED to
combine 		submitted chemical-specific data with that from the Pesticide
Handlers 		Exposure Database (PHED) Version 1.1 to assess handler
exposures for 		regulatory actions. 1

-then-

PHED was designed by a task force of representatives from the U.S. EPA, 
	Health Canada, the California Department of Pesticide regulation, and 	
member companies of the American Crop Protection Association.  PHED is a
		software system consisting of two  parts -- a database of measured
exposure 		values for workers involved in the handling of pesticides
under actual field 		conditions and a set of computer algorithms used to
subset and statistically 		summarize the selected data.  Currently, the
database contains values for 		over 1,700 monitored individuals (i.e.,
replicates)

Users select criteria to subset the PHED database to reflect the
exposure 		scenario being evaluated.   The subsetting algorithms in PHED
are based on 		the central assumption that the magnitude of handler
exposures to pesticides 		are primarily a function of activity (e.g.,
mixing/loading, applying), 			formulation type (e.g., wettable powders,
granulars), application method 		(e.g., aerial, groundboom), and
clothing scenarios (e.g., gloves, double layer 		clothing).

Once the data for a given exposure scenario have been selected, the data
are 		normalized (i.e., divided by) by the amount of pesticide handled
resulting in 		standard unit exposures (milligrams of exposure per pound
of active 			ingredient handled).  Following normalization, the data are
statistically 		summarized.  The distribution of exposure values for
each body part (e.g., 		chest upper arm) is categorized as normal,
lognormal, or  “other” (i.e., 		neither normal nor lognormal).  A
central tendency value is then selected 		from the distribution of the
exposure values for each body part.  These 		values are the arithmetic
mean for normal distributions, the geometric mean 		for lognormal
distributions, and the median for all “other” distributions.  		Once
selected, the central tendency values for each body part are composited 
	into a “best fit” exposure value representing the entire body. 

The unit exposure values calculated by PHED generally range from the 	
geometric mean to the median of the selected data set.  To add
consistency 		and quality control to the values produced from this
system, the PHED Task 		Force has evaluated all data within the system
and has developed a set of 		grading criteria to characterize the
quality of the original study data.  The 		assessment of data quality is
based on the number of observations and the 		available quality control
data. These evaluation criteria and the caveats 		specific to each
exposure scenario are summarized in Table {#}.  While data 		from PHED
provide the best available information on handler exposures, it 		should
be noted that some aspects of the included studies (e.g., duration, 	
acres treated, pounds of active ingredient handled) may not accurately 	
represent labeled uses in all cases.  HED has developed a series of
tables of 		standard unit exposure values for many occupational
scenarios that can be 		utilized to ensure consistency in exposure
assessments.2

1.	HED Science Advisory Council for Exposure, Policy.007, “Use of 		
Values from the PHED Surrogate Table and Chemical-Specific 			Data.” 
Health Effects Division, Office of Pesticide Programs, January 			1999.

2.	PHED Surrogate Exposure Guide.  Health Effects Division, Office of 		
Pesticide Program, August 1998.”

