Phosphoric Acid Salts PC Code: 034903, 076413, 176407 

Type of Review: Toxicology (Registration Review)

OFFICE OF CHEMICAL SAFETY

AND POLLUTION PREVENTION

UNITED STATES ENVIRONMENTAL PROTECTION AGENCY

WASHINGTON, D.C. 20460

 

MEMORANDUM

DATE: September 6, 2012

SUBJECT: Toxicology Scoping Document for the Registration Review of Phosphoric Acid Salts (iron 

phosphate, potassium phosphate, & dipotassium phosphate).

Registration Review Case #: 6027

PC Code: 034903, 076413, 176407

CAS #: 10045-86-0, 7778-77-0, 7758-11-4

Chemical Class: Biochemicals

FROM: Sadaf Shaukat, Biologist 

Biochemical Pesticides Branch

Biopesticides & Pollution Prevention Division (7511P)

TO: Leonard Cole, Senior Regulatory Specialist

Biochemical Pesticides Branch

Biopesticides & Pollution Prevention Division (7511P)

ACTION REQUESTED

The following scoping document contains the human health assessment for the biopesticides Phosphoric acid 

salts

in support of the development of the Registration Review Work Plan. 

Executive Summary

Based on the available data and information, the Agency does not foresee the need for new data or for new risk 

assessments for phosphoric acid salts. Hazard and exposure information as well as Agency risk assessments on 

these chemicals were evaluated against current safety standards established by the Agency’s scientific policies 

and regulations and it was determined that there is no need to conduct additional risk assessments. The active 

ingredients naturally occurring, have a non-toxic mode of action, and are of low toxicity. There is reasonable 

certainty of no harm to the general population from exposure to these chemicals in pesticide products when they

are used according to label instructions.
Phosphoric Acid Salts PC Code: 034903, 076413, 176407 

Type of Review: Toxicology (Registration Review) 

 

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I. Background

Phosphoric Acid Salts

As a pesticide, iron (ferric) phosphate is used in controlling snails and slugs on food crops and ornamentals at 

outdoor and indoor sites. Iron phosphate is a common chemical with a variety of uses, including as a human 

nutritional supplement and as an ingredient in fertilizer. It is applied to soil as part of a pellet that also contains 

bait to attract snails and slugs. When the pests eat the pellets, the iron phosphate interferes with calcium 

metabolism in their gut, causing the snails and slugs to stop eating almost immediately. They die three to six 

days later. (Iron Phosphate Fact Sheet, 2001)

The chemical was first registered by the Agency in 1997. There are currently four registered products 

containing the active ingredient. All four products are end-use products (EPs). Iron phosphate is the sole active 

ingredient in three of the products. Spinosad is an additional active ingredient for one of the products. There are 

no currently approved uses for this chemical as an inert ingredient in pesticide products.

As a pesticide, potassium phosphate is used as a fungicide against powdery mildew on food crops. It does 

have a toxic mode of action, so is therefore not classified as a biochemical. However, it is eligible for reduced 

data requirements because of its simple structure and natural occurrence. (Potassium Phosphate Fact Sheet, 

2009)

The chemical was first registered by the Agency in 1998. There are currently four registered products 

containing the active ingredient. All four products are EPs. Potassium phosphate is not the sole active ingredient

in these products. Mono- and di- potassium salts of phosphorous acid or sulfur are additional active ingredient 

for the products. There are no currently approved uses for this chemical as an inert ingredient in pesticide 

products.

As a pesticide, dipotassium phosphate is also used as a fungicide against a broad spectrum of diseases 

including powdery mildew, leaf spot, root dot, downy mildew, etc. on turf, ornamentals, and non-bearing fruit 

and nut tree crops. It appears to have a mixed mode of action involving direct toxicity to the pathogen, aided by

a boosting of the plant’s defense mechanisms due to the fertilizing properties of the compound. (Dipotassium 

Phosphate Fact Sheet, 2002)

The chemical was first registered by the Agency in 2002. There is currently one registered product containing 

the active ingredient. This product is an EP. Diotassium phosphate is not the sole active ingredient in this 

product. Mono- and di- potassium salts of phosphorous acid are the additional active ingredients for the product. 

There are no currently approved uses for this chemical as an inert ingredient in pesticide products.

II. Tolerances

40 CFR § 180.1191: Ferric phosphate; exemption from the requirement of a tolerance.

An exemption from the requirement of a tolerance is established for residues of the biochemical pesticide, ferric 

phosphate (FePO4, CAS No. 11045–86–0) in or on all food commodities. [62 FR 56105, Oct. 29, 1997].
Phosphoric Acid Salts PC Code: 034903, 076413, 176407 

Type of Review: Toxicology (Registration Review) 

 

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40 CFR § 180.1193: Potassium dihydrogen phosphate; exemption from the requirement of a tolerance.

Potassium dihydrogen phosphate is exempted from the requirement of a tolerance in or on all food commodities 

when applied as a fungicide in accordance with good agricultural practices. [63 FR 43085, Aug. 12, 1998]

III. Incidents

According to the Incident Data System, there have been no reports of incidents resulting from the use of 

pesticide products containing potassium phosphate and dipotassium phosphate as active ingredients from 

January 1, 1992 to October 27, 2011.

There have been 50 reported incidents resulting from the use of pesticide products containing iron phosphate as 

the active ingredient.

IV. Toxicity Profile

Iron Phosphate

Sufficient data have been provided to fulfill the biochemical pesticide data requirements under 40 CFR 

158.2050 for the current use patterns for iron phosphate. The data available to the Agency are summarized in 

Table 1 below.
Phosphoric Acid Salts PC Code: 034903, 076413, 176407 

Type of Review: Toxicology (Registration Review) 

 

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Table 1. Human Health Assessment Data Requirements for iron phosphate* (40 CFR § 158.2050)

Study/OCSPP Guideline No. Results Toxicity 

Category/Description MRID

Acute oral toxicity (rat)

(870.1100) LD50 > 5,000 mg/kg IV 44042704

Acute dermal toxicity (rabbit)

(870.1200) LD50 > 5,000 g/kg for males and females IV 44042705

Acute inhalation toxicity (rat)

(870.1300)

Waived. FDA regards iron phosphate as GRAS; it is 

abundant in nature, has low toxicity, is used as a 

nutritional supplement, and has low water-solubility.

Primary eye irritation (rabbit)

(870.2400)

Minimally irritating. Minimal irritation of the 

conjunctivae, resolved within 48 hours. III 44042706

Primary dermal irritation (rabbit)

(870.2500) No irritation observed IV 44042407

Dermal sensitization (Buehler-guinea pig)

(870.2600)

Waived. FDA regards iron phosphate as GRAS; it is 

abundant in nature, has low toxicity, is used as a 

nutritional supplement, and has low water-solubility.

Dermal sensitization (LLNA)

(870.2600)

Waived. FDA regards iron phosphate as GRAS; it is 

abundant in nature, has low toxicity, is used as a 

nutritional supplement, and has low water-solubility.

90-Day oral toxicity

(870.3100)

Waived. FDA regards iron phosphate as GRAS; it is 

abundant in nature, has low toxicity, is used as a 

nutritional supplement, and has low water-solubility.

90-Day dermal toxicity

(870.3250)

Waived. FDA regards iron phosphate as GRAS; it is 

abundant in nature, has low toxicity, is used as a 

nutritional supplement, and has low water-solubility.

90-Day inhalation toxicity

(870.3465)

Waived. FDA regards iron phosphate as GRAS; it is 

abundant in nature, has low toxicity, is used as a 

nutritional supplement, and has low water-solubility.

Mutagenicity

(Bacterial reverse mutation test; 870.5100)

Waived. FDA regards iron phosphate as GRAS; it is 

abundant in nature, has low toxicity, is used as a

nutritional supplement, and has low water-solubility.

Mutagenicity

(Unscheduled DNA synthesis in 

mammalian cells; 870.5550)

Waived. FDA regards iron phosphate as GRAS; it is 

abundant in nature, has low toxicity, is used as a 

nutritional supplement, and has low water-solubility.

Waived. FDA regards iron phosphate as GRAS; it is 

abundant in nature, has low toxicity, is used as a 

nutritional supplement, and has low water-solubility.

Mutagenicity

(In vivo mammalian erythrocyte 

micronucleus test; 870.5395)

Waived. FDA regards iron phosphate as GRAS; it is 

abundant in nature, has low toxicity, is used as a 

nutritional supplement, and has low water-solubility.

Mutagenicity

(In vitro mammalian cell gene mutation 

test; 870.5300)

Waived. FDA regards iron phosphate as GRAS; it is 

abundant in nature, has low toxicity, is used as a 

nutritional supplement, and has low water-solubility.
Phosphoric Acid Salts PC Code: 034903, 076413, 176407 

Type of Review: Toxicology (Registration Review) 

 

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Table 1. Human Health Assessment Data Requirements for iron phosphate* (40 CFR § 158.2050)

Study/OCSPP Guideline No. Results Toxicity 

Category/Description MRID

Developmental toxicity (rabbits)

(870.3700)

Waived. FDA regards iron phosphate as GRAS; it is 

abundant in nature, has low toxicity, is used as a 

nutritional supplement, and has low water-solubility.

*Results taken from studies performed on EPs; No data available on TGAI.

Potassium Phosphate

Sufficient data have been provided to fulfill the biochemical pesticide data requirements under 40 CFR 

158.2050 for the current use patterns for potassium phosphate. The data available to the Agency are 

summarized in Table 2 below.
Phosphoric Acid Salts PC Code: 034903, 076413, 176407 

Type of Review: Toxicology (Registration Review) 

 

6 

Table 2. Human Health Assessment Data Requirements for Potassium Phosphate (40 CFR § 158.2050)

Study/OCSPP Guideline No. Results Toxicity 

Category/Description MRID

Acute oral toxicity (rat)

(870.1100)

LD50 > 5,000 mg/kg for males and > 500 g/kg for 

females III 44234202

Acute dermal toxicity (rabbit)

(870.1200) LD50 > 2,000 g/kg for males and females III 44234203

Acute inhalation toxicity (rat)

(870.1300)

Waived. Low acute mammalian toxicity, exempt from 

requirement of a tolerance 

Primary eye irritation (rabbit)

(870.2400)

Practically non-irritating. No corneal opacity or iritis 

was noted during the study. One hour after test 

substance instillation, all animals exhibited 

conjunctivitis with clearance by 48 hours.

III 44234204

Primary dermal irritation (rabbit)

(870.2500) Non-irritant IV 44234205

Dermal sensitization (Buehler-guinea pig)

(870.2600)

Waived. Low acute mammalian toxicity, exempt from 

requirement of a tolerance 

90-Day oral toxicity

(870.3100)

Waived. Low acute mammalian toxicity, exempt from 

requirement of a tolerance 

90-Day dermal toxicity

(870.3250)

Waived. Low acute mammalian toxicity, exempt from 

requirement of a tolerance 

90-Day inhalation toxicity

(870.3465)

Waived. Low acute mammalian toxicity, exempt from 

requirement of a tolerance 

Mutagenicity

(Bacterial reverse mutation test; 870.5100)

Waived. Low acute mammalian toxicity, exempt from 

requirement of a tolerance 

Mutagenicity

(Unscheduled DNA synthesis in 

mammalian cells; 870.5550)

Waived. Low acute mammalian toxicity, exempt from 

requirement of a tolerance 

Mutagenicity

(In vivo mammalian erythrocyte 

micronucleus test; 870.5395)

Waived. Low acute mammalian toxicity, exempt from 

requirement of a tolerance 

Mutagenicity

(In vitro mammalian cell gene mutation 

test; 870.5300)

Waived. Low acute mammalian toxicity, exempt from 

requirement of a tolerance 

Developmental toxicity (rabbits)

(870.3700)

Waived. Low acute mammalian toxicity, exempt from 

requirement of a tolerance 

Dipotassium Phosphate

Sufficient data have been provided to fulfill the biochemical pesticide data requirements under 40 CFR 

158.2050 for the current use patterns for dipotassium phosphate. The data available to the Agency are 

summarized in Table 2 below.
Phosphoric Acid Salts PC Code: 034903, 076413, 176407 

Type of Review: Toxicology (Registration Review) 

 

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Table 3. Human Health Assessment Data Requirements for Dipotassium Phosphate* (40 CFR § 158.2050)

Study/OCSPP Guideline No. Results Toxicity 

Category/Description MRID

Acute oral toxicity (rat)

(870.1100) LD50 > 5,050 mg/kg for males and females IV 44815005

Acute dermal toxicity (rabbit)

(870.1200) LD50 > 5,050 g/kg for males and females IV 44815006

Acute inhalation toxicity (rat)

(870.1300) >2.97 mg/L IV 44815007

Primary eye irritation (rabbit)

(870.2400) No corneal opacity; positive conjunctival irritation IV 44815008

Primary dermal irritation (rabbit)

(870.2500)

Very slight erythema on 2/6 rabbits one hour after 

patch removal with resolution by 24 hours IV 44815009

Dermal sensitization (Buehler-guinea pig)

(870.2600)

Not a sensitizer 44815010

90-Day oral toxicity

(870.3100) Waived. Low acute mammalian toxicity; non-food use

90-Day dermal toxicity

(870.3250)

Waived. Low acute mammalian toxicity; proposed use 

pattern will not result in prolonged exposure at 

concentrations that are likely to be toxic

90-Day inhalation toxicity

(870.3465)

Waived. Low acute mammalian toxicity; proposed use 

pattern will not result in prolonged exposure at 

concentrations that are likely to be toxic

Mutagenicity

(Bacterial reverse mutation test; 870.5100)

Waived. Low acute mammalian toxicity; very low 

nticipated human exposure, not structurally related to a 

mutagen

Mutagenicity

(Unscheduled DNA synthesis in 

mammalian cells; 870.5550)

Waived. Low acute mammalian toxicity; very low 

anticipated human exposure, not structurally related to 

a mutagen

Mutagenicity

(In vivo mammalian erythrocyte 

micronucleus test; 870.5395)

Waived. Low acute mammalian toxicity; very low 

anticipated human exposure, not structurally related to 

a mutagen

Mutagenicity

(In vitro mammalian cell gene mutation 

test; 870.5300)

Waived. Low acute mammalian toxicity; very low 

anticipated human exposure, not structurally related to 

a mutagen

Developmental toxicity (rabbits)

(870.3700)

Waived. Low acute mammalian toxicity; very low 

anticipated human exposure, not structurally related to 

a mutagen

*All acute tox requirements were waived for the TGAI; Results taken from studies performed on EP
Phosphoric Acid Salts PC Code: 034903, 076413, 176407 

Type of Review: Toxicology (Registration Review) 

 

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VI. References

U.S. EPA Biochemical Fact Sheet for Iron Phosphate. Issued January, 2001. 

<http://www.epa.gov/opp00001/chem_search/reg_actions/registration/fs_PC-034903_01-Mar-01.pdf >

U.S. EPA Biochemical Fact Sheet for Potassium Phosphate. Issued January, 2001. 

<http://www.epa.gov/opp00001/chem_search/reg_actions/registration/fs_PC-076413_25-Nov-09.pdf >

U.S. EPA Biopesticides Registration Action Document (BRAD) for Dipotassium Phosphate. Issued March, 

2003.

<http://www.epa.gov/opp00001/chem_search/reg_actions/registration/decision_PC-176407_23-Mar03.pdf>

cc: S. A. Shaukat, L. Cole, BPPD Science Review File, IHAD/ARS

 S. A. Shaukat, FT, PY-S: 09/06/12