 

UNITED STATES ENVIRONMENTAL PROTECTION AGENCY

WASHINGTON, D.C.  20460

OFFICE OF

PREVENTION, PESTICIDES AND

TOXIC SUBSTANCES

MEMORANDUM

March 6, 2008

SUBJECT:	Sodium Nitrate (076104) and Potassium Nitrate (076103).  Human
Health Assessment Problem Formulation Document in Support of
Registration Review.  Registration Review Case No. 4052  Nitrates and
Nitrites.  DP# 342935.  

FROM:	Susan V. Hummel, Chemist and Senior Scientist

		Reregistration Branch 4

		Health Effects Division (7509P)

THRU:	Ray Kent, Chief

		Reregistration Branch 4

		Health Effects Division (7509P)

		

TO:	Eric Miederhoff, CRM Team 53	

		Reregistration Branch 3

		Special Review and Reregistration Division (7508P)

		

Executive Summary

Attached is the Health Effects Division’s (HED) human health risk
assessment problem formulation document for the nitrate and nitrites
reregistration case to support Registration Review.  

Two pesticide active ingredients are part of the nitrates and nitrites
reregistration case, sodium nitrate, and potassium nitrate.  Both of
these pesticide ingredients are used in multiple active ingredient
products also containing carbon, sulfur, and/or sawdust; these products
are fumigant gas cartridge products intended to be placed in burrows to
control small mammals.  The use is outdoors only.  The products have a
fuse, which the user lights, and then the cartridge is immediately
placed inside the burrow, and the burrow entrance covered with dirt. 
The contents of the cartridge burn and release carbon dioxide and toxic
gases.

HED has considered recent risk assessments for sodium and potassium
nitrate, updates to its toxicity, exposure and usage databases, and the
most updated Agency science policy and risk assessment methodologies. 
The most recent risk assessment for sodium and potassium nitrate was
conducted in 1991 in connection with the Reregistration Eligibility
Document (Engler, 1991).  Risks of concern were mitigated by
cancellation of the products with risk concerns.  There are no other
changes to the registrations or to the database of studies.  

HED does not believe that new data are needed for Registration Review
and that existing risk assessments will support Registration Review. 
There are no pesticidal food uses, so there is no dietary assessment,
and no aggregate assessment is required.  Residential and occupational
exposure assessments are available for all uses, and there are no
exposure risks of concern.  No additional human health risk assessments
will be needed for the existing uses of sodium nitrate and potassium
nitrate.

Introduction

The most recent risk assessment for sodium nitrate and potassium nitrate
was conducted in 1991 in connection with the Nitrates and Nitrites
Reregistration Eligibility Document (Engler, 1991), with a supporting
occupational and residential exposure assessment (Morris, 1991), and an
undated, unsigned toxicology assessment.  Risks of concern were
mitigated by cancellation of the products with risk concerns.

Databases consulted for this problem formulation document include HED
databases, OPPIN databases, including the label database.  HED also
conducted an open literature search using Google Scholar.  

The only pesticidal use of sodium nitrate and potassium nitrate is in
multiple active ingredient products also containing carbon, sulfur,
and/or sawdust; these products are fumigant gas cartridge products
intended to be placed in burrows to control small mammals.  

OPPIN lists 3 products containing 46.2 – 53% sodium nitrate, and 3
products containing 38.8 – 45 % potassium nitrate.  There are no
technical products containing sodium nitrate or potassium nitrate.

The product labels contain instructions on how to find the burrow,
prepare the burrow for the use of these products, and the treatment. 
For treatment, the user is instructed to light the fuse, place the
cartridge into the burrow, fuse end first, and then close the burrow
with plenty of dirt.  The following cautions are on the product labels: 
Do Not Inhale!  TOXIC FUMES!  If smoke is seen coming from burrow
entrance, plug firmly with soil.

Chemical Identity

The chemical identity for sodium nitrate and potassium nitrate are
described in the following Tables 1a and 2b.

Table 1a. Chemical Identity of Sodium Nitrate

Common Name	Sodium Nitrate

Chemical Name	Sodium Nitrate

PC Code	076104

Chemical Abstracts No.	7631-99-4

Registration Review Case No.	4052

Chemical Class	Inorganic salt

Chemical Structure	NaNO3



Table 1b. Chemical Identity of Potassium Nitrate

Common Name	Potassium Nitrate

Chemical Name	Potassium Nitrate 

PC Code	076103

Chemical Abstracts No.	7757-79-1

Registration Review Case No.	4052

Chemical Class	Inorganic salt

Chemical Structure	KNO3



The registered products of sodium and potassium nitrate also contain
sulfur, carbon, and/or sawdust.  These products will undergo chemical
reactions and produce toxic fumes after ignition.  Although no toxicity
data are available on the fume by products, HED believes that worker and
bystander exposure scenarios are not likely to exist based on the use
patterns (underground) and with current label precautions.

Hazard Identification/Toxicology

There is very little potential for exposure to sodium or potassium
nitrate from the registered pesticide uses – gas producing cartridges
placed in animal burrows.   Because of the registered use pattern, many
of the normally required toxicity studies were considered unnecessary
for sodium and potassium nitrate.  In addition, these compounds are
normally present in the environment. Nitrates are in the soil and in
plants that take up the nitrates from the soil. Thus, there is no reason
to expect reasonable pesticide usage to constitute any hazard beyond
ordinary exposure.

Sodium nitrate is in Category III for acute oral and dermal toxicity,
toxicity Category II for primary eye irritation, and toxicity Category
IV for primary dermal irritation.  Acute inhalation toxicity has not
been determined.  No subchronic toxicity studies are available.  In some
chronic and carcinogenicity studies, sodium nitrate has been reported as
carcinogenic, in others it has not.  There are several positive
mutagenicity studies.  Nitrate in food may be converted to nitrite,
which, in large doses, converts the hemoglobin in the blood to
methemoglobin, which cannot carry oxygen.  In addition, nitrite produced
can combine with amines to form nitrosamines. Many nitrosamines are
mutagens and carcinogens under laboratory conditions.

Potassium nitrate is in Category III for acute oral toxicity.  No other
toxicity studies were found, with the exception of some mutagenicity
studies.  Some of the mutagenicity studies with potassium nitrate were
positive.  There is no reason to believe that the toxicity of potassium
nitrate is different from the toxicity of sodium nitrate.

No additional toxicity data were required as a condition of
reregistration.  The most recent endpoint table for sodium and potassium
nitrate is found in the HED chapter for the RED (Engler, 1991). 

The product labels contain different first aid instructions, in case the
product gets into eyes, skin, or on clothing.  Cartridge produces oxide
of sulfur gasses.   Fumes may be harmful if inhaled.  If inhaled, and
person has poisoning symptoms (headache, nausea, dizziness, and
weakness, transfer victim to fresh air.  Have victim lie down and keep
warm.  If respiration is adequate recovery will be rapid…   Once
ignited by the fuse, this cartridge will burn vigorously until
completely spent and is capable of causing severe burns to exposed skin
and clothes, and of igniting dry grass, leaves, and other combustible
materials.

Conclusions: The toxicological database on potassium and sodium nitrate
is adequate for human health risk assessment and to support the
continuing registration of sodium nitrate and potassium nitrate.  No new
toxicity studies have been received since the last assessment.  No
re-evaluation of toxicological endpoints and/or safety factors is
required.  Label first aid statements should be standardized.  

Dietary Exposure

There are no pesticidal food uses of potassium and sodium nitrate. 
Nitrates are listed by the Food and Drug Administration as food
additives that may be used in curing of fish, meat, and meat products
and color fixatives (21 CFR 170.60, 21 CFR 172.170).  In 21 CFR 181.33,
the Food and Drug Administration regulations cite prior sanctions issued
by the U.S. Department of Agriculture for the use of sodium and
potassium nitrates in cured red meat products and cured poultry
products.

No dietary exposure assessment is required.  There is very little
possibility of sodium and potassium nitrate reaching drinking water
sources from the current use pattern.

Conclusions:  No dietary exposure assessment is required.  There is very
little possibility of sodium and potassium nitrate reaching drinking
water sources from the current use pattern.

Residential Exposure

For both sodium and potassium nitrates, the potential for applicator and
post-application residential exposure should be minimal, providing the
products are used in accordance with label instructions.  There is no
mixing/loading involved with the end use products; therefore, there
should be no human exposure.  

Aggregate Risk Assessment

There are no food uses for sodium and potassium nitrate.  Residential
exposure should be minimal.  No aggregate risk assessment is required. 

Occupational Exposure 

For both sodium and potassium nitrates, the potential for applicator and
post-application worker exposure should be minimal, providing the
products are used in accordance with label instructions.  There is no
mixing/loading involved with the end use products; therefore, there
should be no human exposure.  

There are no dislodgeable foliar residue data available. Soil
dissipation residue data are not required; nitrates are naturally
present in soils and plants that absorb nitrates from the soil. 

There is the potential for dermal burns following premature flare
ignition.

Conclusions:  There is sufficient information available to assess
occupational exposure.  All of the occupational exposure scenarios for
the registered uses of sodium and potassium nitrates have been assessed
adequately. No new assessment required. 

Public Health and Pesticide Epidemiology Data 

The Agency’s incident database shows 17 incidents involving sodium
nitrate products between January 1992 and October 2007.  Several of the
incidents (4) were listed as property damage.  One incident cited an
injury to a domestic animal, and ten (10) incidents involved injury to
humans when flames exploded from the gas cartridge and burned hands,
legs, or face. 

 

The Agency’s incident database shows 16 incidents involving potassium
nitrate products between January 1992 and October 2007.  Many of the
incidents (10) involved injury to humans when flames exploded from the
gas cartridge and burned hands, legs, or face.  The other incidents (6)
involved are listed as damage to property. 

Severe incidents reported at the time of the RED, resulted in the
cancellation of products containing higher levels of sodium nitrate.

Tolerance Assessment and International Harmonization

There are no pesticidal food uses of potassium and sodium nitrate. 
There are several food additive regulations established by FDA for
curing and color-fixing in fish, and meat and meat products.   There is
no problem with harmonization of tolerances with international MRLs.

Environmental Justice

Potential areas of environmental justice concerns, to the extent
possible, were considered in this human health risk assessment, in
accordance with U.S. Executive Order 12898, "Federal Actions to Address
Environmental Justice in Minority Populations and Low-Income
Populations,"   HYPERLINK
"http://www.eh.doe.gov/oepa/guidance/justice/eo12898.pdf" 
http://www.eh.doe.gov/oepa/guidance/justice/eo12898.pdf ).  The Office
of Pesticide Programs (OPP) typically considers the highest potential
exposures from the legal use of a pesticide when conducting human health
risk assessments, including, but not limited to, people who obtain
drinking water from sources near agricultural areas, the variability of
diets within the U.S. (including different ages, regions, and
ethnicities), and people who may be exposed when harvesting crops. 
Should these highest exposures indicate potential risks of concern, OPP
further refines the risk assessments to ensure that the risk estimates
are based on the best available information.  

There is no dietary or water exposure from pesticidal uses of sodium and
potassium nitrate.  

Cumulative

Sodium and potassium nitrate have not been identified as part of a
common mechanism group.  No cumulative assessment has been conducted.  

Human Studies

No human studies have been relied on in previous risk assessments.

Data Requirements

There are no outstanding data requirements for sodium or potassium
nitrate.  No new studies are needed for registration review.

References

Engler, R., 1991.  “Reregistration Eligibility	Document (RED) for
Sodium Nitrate and Potassium Nitrate,” EPA Memorandum from Reto Engler
to Allan Abramson, dated July 18, 1991.

Morris, L.  1991.  “Review of Potential Occupational and Residential
Exposure to Sodium Nitrate and Potassium Nitrate for the Reregistration
Eligibility Document (RED),” EPA Memorandum from Laura Morris to
Esther Saito, dated June 26, 1991.

	

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