Soap Salts Human Health Risk Assessment D399690 

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1.0 Executive Summary 3

2.0 Regulatory Recommendations 3

3.0 Introduction 4

4.0 Hazard Identification and Dose-Response Assessment 4

5.0 Dietary Exposure and Risk Assessment 6

5.1 Food Residue Profile 6 

5.2 Dietary Exposure and Risk Assessment 6 

6.0 Residential (Non-Occupational) Exposure/Risk Characterization 6

7.0 Aggregate Exposure/Risk Characterization 6

8.0 Cumulative Exposure/Risk Characterization 7

9.0 Occupational Exposure/Risk Characterization 7

10.0 References 8

 
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1.0 Executive Summary 

HED has prepared a human health risk assessment to support registration review for the uses of 

sodium, potassium, and ammonium soap salts as active ingredients in pesticides. Because of the 

limited uses, minimal potential for exposure, and low toxicity, HED determined that a qualitative 

risk assessment is appropriate for the soap salts. 

Potassium and ammonium salts are currently exempt from the requirement of a tolerance. An 

exemption for sodium salts is not needed, as there are no uses on/near food crops. There are no 

concerns for residential and occupational exposures since the labels specify adequate protection 

from the irritating effects of soap. 

Fatty acids are normally metabolized by the cells, where they are oxidized to simple compounds 

for use as energy sources and as structural components utilized in all living cells. Sodium, 

potassium, and ammonium are normally part of the body’s metabolism and electrolyte balance. 

Oral exposure to soaps is generally self-limiting because the taste of soap is unpleasant. Also, 

the ammonium soap salts have a notable ammonia odor that is self-limiting. To date, EPA has 

waived all generic mammalian toxicity data requirements for the soap salts. No in vivo toxicity 

testing studies relevant to HED’s human health risk assessments were identified in a literature 

screen. 

HED continues to believe that it is appropriate to waive all generic mammalian toxicity data 

requirements for the soap salts, due to the lack of effects at high doses in the available toxicity 

studies, the nature of the chemicals (fatty acids) and their ubiquity in nature, and the limited 

exposure via the oral route resulting from established uses. 

While exposure to soap salts is possible via dietary exposure, HED has not identified any 

toxicological endpoints for human health risk assessment. Therefore, HED concludes that no 

quantitative dietary assessments are needed. 

Soap salts do not belong to a common mechanism group, and therefore there are no cumulative 

risk concerns. No human studies were used in the soap salts risk assessment. 

2.0 Regulatory Recommendations

Sufficient data are available to support HED’s decision to waive generic mammalian toxicity 

data requirements for the soap salts. 

Residues of potassium soap salts are exempt from the requirement of a tolerance in 40 CFR § 

180.1068 when used in accordance with good agricultural practice. Similarly, residues of 

ammonium soap salts are except from the requirement of a tolerance in 40 CFR § 180.1284 

when used in accordance with good agricultural practices. Further, the potassium and sodium 

salts are generally recognized as safe (GRAS) in food and in the manufacture of food, as 

described in 21 CFR § 172.863. 

Codex has not established maximum residue limits for any of the soap salts. 

HED has no objection to the continuing registration of soap salts for current uses. 
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3.0 Introduction

The soap salt registration review case is comprised of three active ingredients which are 

currently associated with active product registrations. These chemicals are (1) ammonium salts 

of C8 - C18 saturated and C18 unsaturated fatty acids; (2) potassium salts of C12—C18 saturated 

fatty acids; and (3) sodium salts of mixed fatty acid esters. Potassium salts are produced by 

adding potassium hydroxide to fatty acids found in animal fats and in plant oils, such as palm, 

coconut, olive, castor, and cottonseed oils. A similar process is used for producing ammonium 

and sodium soap salts. 

The potassium salts are used as insecticides, herbicides, fungicides, and algaecides in a variety of 

settings, including food crops and residences. The ammonium salts are used as herbicides and 

deer and rabbit repellents, also in a wide variety of settings including agricultural settings. The 

sodium salts are used as a deer repellent in residential settings only. 

Potential areas of environmental justice concerns, to the extent possible, were considered in the 

human health risk assessment, in accordance with U.S. Executive Order 12898, "Federal Actions 

to Address Environmental Justice in Minority Populations and Low-Income Populations1

." 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., 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. 

4.0 Hazard Identification and Dose-Response Assessment

The toxicology database for soap salts is adequate to support reregistration eligibility. 

To date, EPA has waived all generic mammalian toxicity data requirements for the soap salts due 

to the lack of effects at high doses in the available studies, the nature of the chemicals (fatty 

acids) and their ubiquity in nature, and the limited potential for human exposure via the oral 

route from established uses. The ammonium, potassium, and sodium salts demonstrate similar 

toxicity, so that they are grouped in the same EPA case. With no systemic toxicity observed, 

HED did not select endpoints for human health risk assessment and waived all mammalian 

toxicity data. For the current action, a search of the open literature was conducted through 

Google Scholar to identify any new toxicity studies since HED’s 2008 memorandum “Soap 

Salts. Revised Human Health Assessment Scoping Document in Support of Registration 

Review.” (D352949, C. Olinger, September 03, 2008). None were identified. 

According to peer review literature, no single dose or repeated dose study available produced a 

systemic toxic effect up to or near the limit dose in any exposure route. 

Soap salts caused mutagenic effects when administered to laboratory animals at high doses. 

Unscheduled DNA synthesis was found in mouse cells with 35 mg/kg of oleic acid2

. 

Cytogenetic analysis was positive for 2500 ug/L of oleic acid with hamster fibroblasts and for 

 

1

 Available: http://www.eh.doe.gov/nepa/tools/guidance/Volume1/2-6-EO_12898envjustice.pdf
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100 mg/L with Saccaromyces cerevisiae2. As noted earlier, the potassium and sodium soap salts 

are GRAS compounds, and the three soap salts compounds are either exempt from the 

requirement of a tolerance or a tolerance does not apply. Fatty acids like the soap salts are 

ubiquitous in nature and exposures to high dietary or residential doses of the soap salts are 

unlikely given the pesticidal use patterns. 

No toxicological points of departure were selected for soap salts based on the available toxicity 

data. As a result, no dietary, residential, occupational, or aggregate exposure assessments are 

required at this time. 

Fatty acids are normally metabolized by the cells, where they are oxidized to simple compounds 

for use as energy sources and as structural components utilized in all living cells. Sodium, 

potassium, and ammonium are normally part of the body’s metabolism and electrolyte balance. 

Oral exposure to soaps is generally self-limiting because the taste of soap is unpleasant. The 

ammonium soap salts also have a notable ammonia odor that is self-limiting. Eye irritation for 

ammonium, potassium, and sodium salts is addressed through product labeling (See Section 9.0). 

Potassium salts of fatty acids have low acute toxicity by oral, dermal, or inhalation routes of 

exposure and are considered to be severe eye irritants, based on corneal involvement. Potassium 

salts of fatty acids are corrosive to the skin based on severe erythema at both intact and abraded 

sites and cracking and fissuring of epithelial layers, but are not dermal sensitizers. 

Ammonium and sodium salts of fatty acids have low acute toxicity by oral, dermal, or inhalation 

routes of exposure. Ammonium and sodium salts of fatty acids are considered to be mild skin 

irritants, dermal sensitizers, and are corrosive to the eye. 

In an open literature report, potassium salt of cocoa fatty acids was examined for developmental 

effects following percutaneous administration to mice and rats (Palmer et al, 1975). Solutions 

containing 0.3, 3 and 30% of a soap salts were applied to shaved skin during pregnancy days 2-

13 in mice and 2-15 in rats. The treated area was not occluded or washed. Dosages employed 

were 0.5 mL/rat or mouse/day. These doses were equivalent to 50, 500 and 5000 mg/kg/day for 

mice and 6, 60, and 600 mg/kg/day for rats. In mice treated with 500 and 5000 mg/kg/day, the 

maternal mice demonstrated marked skin reaction, irritability, weight loss and failure to maintain 

pregnancy. In young mice at 500 mg/kg/day, the incidences of fetal loss, malformations, visceral 

or skeletal anomalies and skeletal variants were within the historical control range (0-4.4%). In 

young mice at 5000 mg/kg/day (a dose level 5X of limit dose), the assessments of these effects 

were impossible due to the negligible numbers of litters and young mice available for 

examination. In rats treated with 600 mg/kg/day (highest dose tested), the maternal animals 

demonstrated erythema and edema. The incidences of fetal loss, litter size, malformations, 

visceral or skeletal anomalies and skeletal variants in all treated rats were comparable to the 

control group. 

A developmental toxicity study in rats dosed with ammonium nonanoic acid (C9 fatty acid) 

(MRID 43843508), reported that the treatment had no adverse effects. No fetal toxicity was 

 

2

 Sax, N. I., and Lewis, R. J. SR, 1989. Dangerous properties of Industrial Materials, 7th Edition. Van Nostrand 

Reinhold, New York. 
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observed. The no observed adverse effect level (NOAEL) for maternal and developmental 

toxicity was 1,500 mg/kg/day and the lowest observed adverse effect level (LOAEL) was > 

1,500 mg/kg/day. The developmental toxicity study for ammonium nonanoic acid showed no 

effects at dose levels below the limit dose (1,000 mg/kg/day). 

5.0 Dietary Exposure and Risk Assessment

5.1 Food Residue Profile

Residues of ammonium soap salts are except from the requirement of a tolerance in 40 CFR § 

180.1284 when used in accordance with good agricultural practices. Similarly, residues of 

potassium soap salts are exempt from the requirement of a tolerance in 40 CFR § 180.1068 when 

used in accordance with good agricultural practice. Further, the potassium and sodium salts are 

generally recognized as safe in food and in the manufacture of food, as described in 21 CFR § 

172.863. 

5.2 Dietary Exposure and Risk Assessment

While exposure to soap salts (potassium, ammonium) could occur via the diet, HED has not 

identified any toxicological endpoints to conduct a human health risk assessment. Therefore, no 

additional data are required and no quantitative dietary assessments are needed. The soap salts 

have a low acute toxicity via the oral route of exposure and residues from the pesticides uses are 

not likely to exceed the levels of naturally occurring fatty acids in commonly eaten foods. 

There is a tolerance exemption for potassium oleate acid related C12-C18 fatty acid potassium 

salts [40 CFR §180.1068] when used under good agricultural practices. A tolerance exemption 

for the ammonium salts of higher fatty acids (C8–C18 saturated; C8–C12 unsaturated) was 

recently established in 40 CFR §180.1284 (Federal Register, Vol. 73, No. 132, pp. 39264-

39269) when applied for the suppression and control of a wide variety of grasses and weeds. 

However, there are product labels for the ammonium salts with instructions for use in 

agricultural settings as a deer repellent to growing crops and orchards with fruit present. 

A 2009 revision to the ammonium soap salts tolerance exemption [Federal Register, Vol. 74, 

47457) exempted ammonium salts of C8-C18 saturated and C8-C12 unsaturated higher fatty 

acids from the requirement of a tolerance for residues in or on all food commodities when used 

in accordance with good agricultural practice. An exemption for sodium salts is not needed, as 

there are no food uses. Residue chemistry studies have not been submitted, and none are 

required. 

6.0 Residential (Non-Occupational) Exposure/Risk Characterization

While exposure to soap salts could occur in the residential environment, HED has not identified 

any toxicological endpoints to conduct a human health risk assessment. 

HED has no objection to the continuing registration of soap salts because there are adequate 

label recommendations regarding potential eye and skin irritation. Current product labels 

require protective eyewear while applying the ammonium salts of fatty acids to prevent 

permanent eye injury. These requirements are appropriate and should be retained. 

7.0 Aggregate Exposure/Risk Characterization
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HED has no concern for aggregate risk resulting from the existing uses of soap salts given the 

lack of toxicity and in light of the natural prevalence of these compounds in the environment. 

While both residential and dietary exposures are possible given the use pattern, HED has not 

identified any toxicological points of departure needed to conduct a quantitative human health 

risk assessment. 

8.0 Cumulative Exposure/Risk Characterization

Unlike other pesticides for which EPA has followed a cumulative risk approach based on a 

common mechanism of toxicity, EPA has not made a common mechanism of toxicity finding as 

to the soap salts and any other substances and soap salts do not appear to produce a toxic 

metabolite produced by other substances. For the purposes of this tolerance action, therefore, 

EPA has not assumed that soap salts have a common mechanism of toxicity with other 

substances. For information regarding EPA’s efforts to determine which chemicals have a 

common mechanism of toxicity and to evaluate the cumulative effects of such chemicals, see the 

policy statements released by EPA’s Office of Pesticide Programs concerning common 

mechanism determinations and procedures for cumulating effects from substances found to have 

a common mechanism on EPA’s website3

. 

 

9.0 Occupational Exposure/Risk Characterization

Occupational exposure to soap salts is possible due to their registered use pattern. While 

exposure to soap salts could occur in occupational settings, HED has not identified any 

toxicological endpoints to conduct a human health risk assessment. 

Potassium salts of fatty acids are used on vegetables up to the day of harvest, indoor plants, and 

unspecified domestics dwellings. Products are typically applied with spray bottles or hand held 

sprayers. Ammonium salts of higher fatty acids are used as an herbicide or rabbit and deer 

repellent on forage and grain crops, vegetables, nursery stock, flowers, fruit trees and vines. The 

sodium salts are used as a deer repellent on trees and shrubs. 

All ammonium salts of fatty acids liquid concentrate products contain the warning “Wear eye 

protection (goggles, face shield, or safety glasses), long sleeved shirt, long pants, socks, shoes 

and rubber gloves. After this product is diluted in accordance with label directions, eye 

protection, gloves and long sleeves are not required.” Additionally, the instructions (e.g., “Avoid 

contact with eyes or clothing. Wash thoroughly with soap and water after handling” and “Causes 

substantial, but temporary eye injury. Causes skin irritation. Do not get on skin, in eyes, or on 

clothing. Wear goggles or safety glasses. Wash thoroughly with soap and water after handling”) 

on the product label are adequate for applicators. 

 

3

 Available: at http://www.epa.gov/pesticides/cumulative/. 
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10.0 References

Table 7.1. Memoranda Relevant to Registration Review Risk Assessment 

Author Barcode Date Title 

Literature 

Study 

N/A 1975 Palmer, A. K., Readshaw, M. A., Neuff, A. M., 1975. 

Assessment of the teratogenic potential of surfactants. Part 

III—Dermal application of LAS and soap. Toxicology, 4 

(1975) 171-181. 

L. Kutney None 6/12/92 Human Health Risk Assessment for the Reregistration 

Eligibility Document (RED) 

C. Swartz D171289 5/26/92 Soap. Potassium Salts of Fatty Acids /Ammonium Salts of 

Fatty Acids Chemistry Branch Input (Product and Residue 

Chemistry) to the Reregistration Eligibility Document (RED) 

P. 

McLaughlin 

None 4/22/92 Toxicology Review for the Reregistration Eligibility 

Document on Soap and Soap Salts

J. Yowell None 6/8/92 Review of Potential Occupational and Residential Exposure to 

Soaps for the Reregistration Eligibility Document (RED) 

C. Olinger D352949 9/3/08 Soap Salts. Revised Human Health Assessment Scoping 

Document in Support of Registration Review.