UNITED STATES ENVIRONMENTAL PROTECTION AGENCY

MEMORANDUM 

SUBJECT: Summary of ecotoxicity

potassium phosphate, & potassium phosphate) in relation to the 

Review Scoping Document

Registration Review Case #: 

PC Code:

CAS #:

Chemical Class: 

FROM: Miachel Rexrode, Ph.D., Senior Biologist 

Biochemical Pesticides Branch

Biopesticide & Pollution Prevention Division (7511P)

TO: Leonard Cole, 

Biochemical Pesticides Branch

Biopesticide & Pollution Prev

ACTION REQUESTED

The following is the ecotoxicity assessment for phosphoric acid salts 

Registration Review Scoping Document

RECOMMENDATIONS AND CONCLUSIONS

Executive Summary

Based on the available information for 

need for additional ecotoxicity data for a new risk assessment and has 

exposure data on these chemicals

UNITED STATES ENVIRONMENTAL PROTECTION AGENCY

 WASHINGTON, D.C. 20460

OFFICE OF CHEMICAL SAFETY AND POLLUTION PREVENTION

MEMORANDUM September 14, 2012

cotoxicity risk assessment for phosphoric acid salts (iron phosphate, 

potassium phosphate, & potassium phosphate) in relation to the for

Review Scoping Document

Registration Review Case #: 6027

 034903, 076413, 176407

 10045-86-0, 7778-77-0, 7758-11-4

 Biochemicals

Miachel Rexrode, Ph.D., Senior Biologist /s/ 09/1

Biochemical Pesticides Branch

Biopesticide & Pollution Prevention Division (7511P)

Leonard Cole, Regulatory Action Leader /s/ 09/1

Biochemical Pesticides Branch

Biopesticide & Pollution Prevention Division (7511P)

The following is the ecotoxicity assessment for phosphoric acid salts in support of

Scoping Document. 

RECOMMENDATIONS AND CONCLUSIONS

Based on the available information for phosphoric acid salts the Agency does not foresee the 

data for a new risk assessment and has waived all 

s. These active ingredients are naturally occurring, have a non

OFFICE OF CHEMICAL SAFETY AND POLLUTION PREVENTION

, 2012

phosphoric acid salts (iron phosphate, 

for Registration 

/s/ 09/14/2012

/s/ 09/14/2012

in support of the 

the Agency does not foresee the 

waived all hazard and 

ly occurring, have a non-
toxic mode of action, and are of low toxicity. There is reasonable certainty of no harm to the 

non-target species from exposure to these chemicals in pesticide products when they are used 

according to label instructions. Environmental hazard and fate data requirements for the 

Registration Review of Phosphoric Acid Salts have been fully satisfied for this Scoping 

document. An evaluation of risk to endangered/ threatened species will be completed for the 

final registration review.

Background

Phosphoric Acid Salts

Iron (ferric) phosphate (034903) 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 resulting in death three to six days later (Iron Phosphate 

Fact Sheet, 2001). Iron (ferric) phosphate 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. The maximum application rate is 0.5 –

1.0 lbs ai/1000 sq ft.

Potassium phosphate (076413) 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). Potassium phosphate 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. Monoand di- potassium salts of phosphorous acid or sulfur are additional active ingredient for the 

products. 

Dipotassium phosphate (176407) 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). Dipotassium 

phosphate was first registered by the Agency in 2002. There is currently one registered product 

containing the active ingredient. This product is an EP. Dipotassium 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.
Ecological Effects

Iron (ferric) phosphate

As a pesticide active ingredient, iron 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. 

The substance is not harmful to humans, to other non-target organisms, or to the environment. It 

is an alternative to a more toxic chemical that has been used for controlling snails and slugs.

Iron phosphate is applied to the soli as granular bait (0.5 – 1 lb ai/1000 sq ft; 2.4 - 4.9 g/ m2). Use 

sites include food crops, ornamentals, lawns and gardens, and greenhouses.

Assessing Risks to the Environment

Snails and slugs are more sensitive to the effects of iron phosphate than are other organisms. No 

toxicity was seen in mammals (LD50 > 5,000 mg/kg), birds, or fish. For several other organisms,

including earthworms and certain ground beetles, no harmful effects are expected if users follow 

the application rates and use directions on the label. A study (Kuhner, 1996) conducted on 

ground beetles (Poecilus cupreus L) found that tested application rate of 10 g/m2iron phosphate 

showed no effect under field conditions. A reproduction study conducted on Rove Beetles 

(Aleocharu bilineata Gyll) also found no effects after iron phosphate exposure of 10 g/m2for 14 

days (Almond 1996). Wachter (1996), tested earthworms (Eisenia fetida) using artificial soil 

and found LC50 >1,000 mg/kg after exposure to iron phosphate. The exposure of non-target 

insects and earthworms to iron phosphate use as snail bait will not result in toxic risk. The tested 

application rate of 10 g/m2showed no effect and is twice the level of the registered maximum 

application rate (4.9 g/m2) (Risk Quotient = 0.0).

Endangered Species

Environmental hazard and fate data requirements for the Registration Review of Phosphoric Acid 

Salts have been fully satisfied for this Scoping document. An evaluation of risk to endangered/ 

threatened species will be completed for the final registration review.

Potassium Phosphate

Potassium phosphate is naturally occurring, has had widespread use with no adverse effects, but 

has a toxic mode of action on fungi. This compound does not share any common mechanisms of

toxicity with other pesticide active ingredients and is used as an agricultural fertilizer and a 

buffering agent in pesticide formulations. There are no reported adverse effects from these uses 

and toxicology studies submitted indicated low mammalian toxicity (rat LD50 > 5,000 mg/kg). 

Therefore, no impact on the potential for toxic effects from the pesticidal use is expected when 

added to the other uses of potassium phosphate.

Data waivers for ecological effects studies were requested and supported based on the current 

use as a pesticide inert ingredient and fertilizer, and low acute mammalian toxicity. In addition, 

potassium phosphate is ubiquitous in nature, and no adverse effects have been reported on 

nontarget species with current uses. Risk to nontarget species is minimal due to the use pattern, 
application methods, and mitigation of nontarget aquatic organism toxicity with appropriate 

precautionary label statements under "Environmental Hazards."

Endangered Species

Environmental hazard and fate data requirements for the Registration Review of Phosphoric Acid 

Salts have been fully satisfied for this Scoping document. An evaluation of risk to endangered/ 

threatened species will be completed for the final registration review.

Dipotassium Phosphate

Dipotassium phosphate is commonly used as a foliar fertilizer. There have been no adverse 

ecological effects noted from its usage as a fertilizer. As a result, the data requirements for nontarget 

organisms were waived. According to the Mineral Acids Red (dated December, 1993), phosphoric 

acid (and its salts) generally dissociates and releases hydrogen ions in the environment. As a result, 

risk to nontarget organisms is expected to be minimal. BPPD believes that the use of dipotassium 

phosphate according to label use directions should result in no significant adverse effects to wildlife.

Endangered Species

Environmental hazard and fate data requirements for the Registration Review of Phosphoric Acid 

Salts have been fully satisfied for this Scoping document. An evaluation of risk to endangered/ 

threatened species will be completed for the final registration review.

References

Almond, D.S. 1996. NEU 1165M Acute toxicity to the Rove Beetle (Aleocharu bilineata Gyll) in 

the laboratory. (MRID# 44171602)

Kuhner, C. 1996. NEU 1165M: Acute toxicity to the Ground Beetle (Poecilius cupreus L.) in the 

Laboratory. (MRID# 44171601)

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_PC176407_23-Mar-03.pdf>

Wachter, S. 1996. Acute toxicity of NEU 1165M on earthworms (Eisenia fetida) using artificial 

soil testing. (MRID# 44171603)