Page 2 of 25

as histopathological lesions in the nasal turbinates were observed. In a 7-repeat dose oral feeding 

study in rats, no systemic toxicity was observed at doses up to 1805 mg/kg/day. No effects were 

seen for parental toxicity, offspring/developmental toxicity or reproductive performance in a 

combined reproductive/developmental toxicity screening test at doses up to 1000 mg/kg/day. In 

one developmental toxicity study in rats, no parental systemic or developmental toxicity was 

observed at doses up to 400 mg/kg/day. Available prenatal developmental toxicity data showed 

some evidence of slight maternal toxicity but no developmental effects. Methane sulfonic 

acid was not mutagenic and did not induce chromosomal aberrations. There are no metabolism, 

chronic toxicity or carcinogenicity studies available on methane sulfonic acid. However, based 

on the lack of systemic toxicity at 1000 mg/kg/day and above in a combined 

reproductive/developmental screening study and 7-day dietary study, and the lack of 

mutagenicity concern, there are low concerns for cancer. 

Although neurotoxicity studies have not been submitted for methane sulfonic acid there is no 

evidence of neurotoxicity in any study in the toxicity database including a combined 

reproductive/developmental toxicity screening test and prenatal developmental toxicity studies.

The inhalation toxicity NOAEL was taken from the repeat-dose inhalation study discussed 

earlier. There were no treatment related macroscopic findings in the treated animals. 

Microscopic findings believed attributable to the test material included mucosal necrosis, 

suppurative inflammation and/or nasal exudate in males and females in the 0.23 and 0.74 mg/L 

groups. The NOAEL was determined to be 0.74 mg/L (~191 mg/kg/day).

The dermal toxicity NOAEL is selected from an oral developmental toxicity study with the 

assumption of 100% dermal absorption. Based on the results of this study, the dermal toxicity 

NOAEL was 400 mg/kg/day. 

The oral toxicity NOAEL is taken from the developmental toxicity study with female SpragueDawley rats where the NOAEL was identified as 400 mg/kg/day. This dose is used for the 

dietary exposure assessment. 

Based upon the requested use patterns, humans may be exposed to methane sulfonic acid via 

diets, dermal and inhalation. Dietary exposure may occur as a result of residues transferred from 

treated food contact areas and eating meat from treated animals. Dietary exposure may occur as 

a result of residues remaining in treated food/dairy processing equipment or systems. Dermal 

and inhalation exposures may occur as a result of the use of sanitizing solutions which contain 

methane sulfonic acid. Exposures from the use of sanitizing solutions may be “occupational” 

exposures or “residential” exposures. Occupational exposures are those that result from persons 

who use/apply sanitizing solutions during the course of normal work related activities such as 

cleaning/disinfecting food contact preparation surfaces and food or dairy processing machinery 

or systems. “Residential” dermal and inhalation exposure may occur when individuals use 

cleaning solutions that contain methane sulfonic acid.

The proposed use on animals at 3 % concentration is for use in a disinfectant teat wash for dairy 

cattle, goats or sheep. This could result in dietary exposure. However, the Agency believes that 

use as a disinfectant teat wash would contribute negligible amounts of methane sulfonic acid to 
Page 3 of 25

food/dairy processing. The current Agency assessments of dietary exposure are believed to be 

conservative (protective) enough to negate any health concerns as a result of that use pattern. 

Margins of Exposure for residential exposures (including aggregate exposure) and for 

occupational exposures are greater than 100 which do not exceed the Agency’s level of concern.

Discussion of environmental fate and effects is taken from EPA (2008). The conclusions in the 

earlier evaluation is not expected to have changed and thus are relied upon herein. The relative 

distributions of chemicals released into the environment can be estimated using the Level III 

Fugacity Model. This model (Table 6) shows that methane sulfonic acid will partition primarily 

to soil and water, with a higher affinity to soil, and a negligible portion to air and sediment. 

Methane sulfonic acid is a strong acid with pKa of -1.92. This value indicates that methane 

sulfonic acid will exist as an anion in moist soils and water. Methane sulfonic acid is minimally 

volatile from water since anions do not volatilize. Methane sulfonic acid is highly mobile in soil 

with a Log Koc of 0.0 and biodegradation occurs rapidly; 100% of theoretical biochemical 

oxygen demand in 28 days using an activated sludge inoculum. If released to the atmosphere, 

methane sulfonic acid will degrade by reaction with photochemically produced hydroxyl radicals 

with an estimated half-life of approximately 58 days. Methane sulfonic acid is expected to have 

low persistence and low bioaccumulation potential. 

Based upon the findings presented earlier in the human health and risk assessment and the 

findings regarding environmental fate and effects, the Agency approves of the requested uses of 

methane sulfonic acid. As such, methane sulfonic acid may be formulated into products for use 

as an acid cleaner in pesticide formulations with a limit not to exceed 3 % final end use 

concentration when used on animals [as a disinfectant teat wash for dairy cattle, goats or sheep]; 

and not to exceed 0.5% (5,000 ppm in end-use dilution solution) when used in antimicrobial 

formulations for food-contact surface sanitizing in public eating places, dairy-processing 

equipment, and food-processing equipment and utensils. 

II. INTRODUCTION

On 30 May 2014, the U.S. Environmental Protection Agency (EPA or “the Agency”) received a 

request (Petition No. IN-10720) from the firm Lewis & Harrison (122 C Street, N.W., Suite 505, 

Washington, DC 20001) on behalf of the BASF Corporation (100 Park Avenue, Florham Park, 

NJ 07932) to approve an exemption from the requirement of a tolerance under 40 CFR § 180.930 

and § 180.940(a) for methane sulfonic acid (CAS Reg. No. 75-75-2) as an inert ingredient used 

as an acid cleaner in pesticide formulations. The petition proposes that methane sulfonic acid

“may be formulated into products for use as an acid cleaner in pesticide formulations with a limit 

of 3 % when used on animals [as a disinfectant teat wash in dairy cattle, goats or sheep]; and 

0.5% (5,000 ppm in use-dilution solution) when used in antimicrobial formulations for foodcontact surface sanitizing in public eating places, dairy-processing equipment, and foodprocessing equipment and utensils.” Based on the foregoing statement, the Agency utilizes 

5,000 ppm as the maximum permissible end-use concentration.

The Agency has previously reviewed and approved the non-food use of methane sulfonic acid

(EPA, 2009). Some of the information contained in the Agency’s 2009 assessment is used 
Page 4 of 25

within the current document. Further, some information contained in Petition No. IN-10720 is 

also used in this document. 

Methane sulfonic acid is marketed worldwide by BASF in various grades up to a very pure 

electronics grade. The registrant has verified that the maximum concentration of methane 

sulfonic acid for use in a formulation is 15% (email, J. Delahay (BASF) to K. Samak (EPA), 

dated 10/26/2009). Typically, most formulations will contain < 5% methane sulfonic acid. It is 

a strong organic acid and is readily biodegradable, ultimately forming sulfate and carbon 

dioxide. Methane sulfonic acid has many uses, including; metal finishing, electropolishing, lead 

recovery, and the proposed use as a cleaner in non-food contact regulated formulations. 

III. PHYSICAL/CHEMICAL PROPERTIES (EPA, 2009)

The Agency’s High Production Volume Screening website, lists the physical properties of 

methane sulfonic acid (CAS No. 75-75-2). Methane sulfonic acid is a liquid at room 

temperature. 

Table 1. Physical and Chemical Properties of Methanesulfonic Acid

Parameter Value MRID 

or Source

Structure O

||

O=S-OH

|

CH3

HPV, 2008

CAS Reg. No. 75-75-2 HPV, 2008

Molecular Weight 96.10 HPV, 2008

Common Names Methanesulfonic Acid HPV, 2008

Physical State Liquid at room temperature HPV, 2008

Density (kg/m3) 1481 @ 18°C

Melting Point (°C) 19 (measured) HPV, 2008

Boiling Point (°C) 167 at 10 Hg; Decomposition at 225 

(measured)

HPV, 2008

Flash Point (°C) 189 HPV, 2008

Water Solubility (g/L at 20°C) 1000 

1 × 106 mg/L; miscible2 (measured)

HPV, 2008

Vapor Pressure (mm Hg at 20°C) 9.75 × 10-3 (measured)

4.28 × 10-4 mm Hg at 25°C2

HPV, 2008

Partition Coefficient (log Kow) -4.98 (estimated) HPV, 2008

Photodegradation Half-life = 39 days HPV, 2008

Stability in Water (Hydrolysis)(t1/2) Not expected to undergo hydrolysis in the 

environment

HPV, 2008

Biodegradation at 28 days (%) 100 HPV, 2008
Page 5 of 25

IV TOXICOLOGICAL PROFILE

Acute Oral Toxicity (EPA. 2009).

(1) Male and female Sprague-Dawley rats were administered methane sulfonic acid via oral 

gavage at 300, 500 or 750 mg/kg. Most clinical abnormalities were observed in two animals that 

died and those that survived to day 14 and included salivation, decreased activity, wobbly gait, 

breathing abnormalities, apparent hypothermia, decreased/no defecation, feces small in size, 

urine stain, hunched posture, unkempt appearance, rough hair coat, piloerection, extremities pale 

in color, dehydration, emaciation, distended abdomen, decreased food consumption and dark 

material around the facial area. Body weight loss was noted for one 300 mg/kg-bw male, one 

500 mg/kg-bw male, two 500 mg/kg females and one 750 mg/kg male during the study day 0-7 

interval. Body weight loss was noted for one 300 mg/kg male and one 750 mg/kg male during 

the study day 7-14 interval. Gross internal findings observed in the animals that died included 

distension/abnormal content/reddened mucosa in the digestive tract, dark red/mottled lungs,

blackish-purple spleens, dark red lymph nodes, stained glandular mucosa in the stomach and 

body fat depletion/ discoloration/adhesions in the abdominal cavity.

LD50 (male) > 750 mg/kg

LD50 (female) < 500 mg/kg

LD50 (combined) = 649 mg/kg

(2) Male and female Sprague-Dawley rats were administered methane sulfonic acid via oral 

gavage at 500, 1000 or 1500 mg/kg. Clinical abnormalities observed during the study included 

salivation, breathing abnormalities, wobbly gait, decreased activity, decreased defecation, rough 

haircoat, urine/fecal stain and dark material around the facial area. Body weight loss was noted 

for one 1000 mg/kg male and one 1000 mg/kg female during the study day 0-7 interval and for 

one 300 mg/kg male and one 1000 mg/kg male during the study day 7-14 interval. In animals 

that died, gross pathologic findings included dark red foci on the liver, blackish-purple spleens 

and abnormal content, reddened/thickened mucosa and discoloration in the digestive tract.

LD50 (male) < 1000 mg/kg

LD50 (female) < 1500 mg/kg

LD50 (combined) = 1157.5 mg/kg

(3) Male Wistar rats were given methane sulfonic acid via oral gavage at 0.25, 0.5 or 1.0 mL/kg 

(or 2000, 4000, or 8000 mg/kg). All rats died by day 5. Sluggishness and unsteady gait were 

seen at all doses. At 1.0 mL/kg, deep breathing was immediately observed. Findings at necropsy 

included: livers mottled and burned, stomach burned, pylorus hemorrhaged and gas filled, 

intestines hemorrhaged and gas filled, kidneys mottled and slightly congested.

LD50 > 0.25 mL/kg equivalent to 2000 mg/kg

Acute Dermal Toxicity (EPA. 2009)

(1) New Zealand White rabbits (10) were treated with 1000 mg/kg of methane sulfonic acid for 

24 hours and observed for 14 days. Instances of few feces were the only abnormal physical signs 

noted during the observation period. Dermal responses were slight to well defined on day 1, 

absent to severe on day 7 and absent to slight on day 14.

LD50 > 1000 mg/kg
Page 6 of 25

(2) Six albino New Zealand White rabbits were treated with 200 or 2000 mg/kg of methane 

sulfonic acid for 24 hours. At the end of the exposure period, no systemic toxicity was observed. 

Two rabbits at 2000 mg/kg died 28 hours after contact and an additional rabbit was euthanized 3 

days after treatment for humane reasons. The 2000 mg/kg dermal exposure is highly toxic 

(severe skin injuries causing death) whereas the 200 mg/kg exposure induces minor skin lesions 

(erythema and acid burns). LD50 >200 < 2000 mg/kg

Acute Inhalation Toxicity (MRID 49396007)

Twenty mice (strain not specified) received a one-time whole-body exposure for one hour in a 

saturated (with methanesulfonic acid) atmosphere estimated to be 0.05 mg/L. No discernable 

effects were seen during the one-hour test or during the 7-day observation period. 

Skin Irritation (MRID 49396007)

A skin irritation study was conducted with the mouse (strain not known). The distal 4 cm of four 

anesthetized mice were immersed in undiluted methane sulfonic acid for one hour then plunged 

into a saturated solution of sodium bicarbonate for 30 seconds. The tail of each mouse was white 

when exposure was terminated and the appendages fell off within one or two days. Methane 

sulfonic acid was determined to be corrosive to the skin.

Eye Irritation (MRID 49396007)

One eye each of two rabbits (strain not specified) received a single dose of 1.0 ml undiluted 

methane sulfonic acid. There was immediate vocalization as a result of the pain. The reaction 

involved all ocular tissues and occurred immediately. The conjunctiva became completely 

necrotic without evident swelling. The iris was dilated with ragged edges and failed to react to 

light. The cornea opacified completely within 24 hours. Methane sulfonic acid is extremely 

corrosive to the eye. 

Sensitization (MRID 49396007)

A skin sensitization test was conducted on Hartley Guinea pigs (10/sex/dose) using the Buehler 

derived test method. There were 5 (male and female) control animals. From a pilot study 

undiluted methane sulfonic acid at 70% produced grades of 2,1 and ± with edema, blanching and 

scabbing on two sites. At 50, 25, 10, 5, 2.5 and 1.0% there were grades of ± and 0.5 % produced 

grades of ± and 0. The 50% concentration was chosen for the study. On day 1 0.3 ml of the test 

substance was applied to the left shoulder. On day 7, the same region received a second dose. 

On day 14, the treated site received and 3rd and final dose. All applications lasted approximately 

6 hours. For the challenge, on day 28 all animals received 0.3 ml of test substance at 25% 

concentration on their left flank. The challenge duration was 24 hours. There was no positive 

control. Twenty guinea pigs were induced by 50% methane sulfonic acid 70% solution (i.e. 35% 

methane sulfonic acid) and challenged by 25% methane sulfonic acid 70 % solution (i.e., 17.5 % 

methane sulfonic acid). None of the test animals responded with a skin grade that would have 

been suggestive of sensitization. 
Page 7 of 25

Repeat-Dose Toxicity (MRID 49396007)

Inhalation

A four-week inhalation repeat dose toxicity study was conducted using “albino rats”. Fifteen 

male and 15 female per dose group were exposed 6hr/day 5day/week for 4 weeks. Doses were 

0.026, 0.073 and 0.242 mg/L aerosol. During the study, 4, 1, 1 and 5 animals in the control, low 

dose, mid-and high-doses were found dead. The deaths were attributed to the confinement in the 

restraint tubes and none were attributable to exposure to the test article. Exposure related clinical 

signs included rales in the high-dose group and an increased incidence of yellow matting on 

various body surfaces in the mid-dose and high-dose groups (males and females). No significant 

findings were noted during the recovery period. There was a transient reduction in body weight 

gain in the high-dose males during the first week. The high dose groups had slightly decreased 

food consumption during the entire exposure period. There were no adverse effects noted in 

hematology, biochemistry, urinalysis or organ weights. Test article related microscopic findings 

were observed in the nasal turbinates of the high dose group that were found dead and in all 

treated groups at study week 4 and 6 evaluations. After the 2-week recovery period there 

seemed at least partial recovery from the irritative effects of the test material. Since this is a 

localized effect, it was not considered as systemic toxicity. Therefore the NOAEL was 0.242 

mg/L, the highest dose tested. The LOAEL was not established in this study. 

Sprague-Dawley rats were exposed to 0, 0.026, 0.082, 0.23 and 0.74 mg/L in a 5 day repeat 

inhalation toxicity study (five males, 5 females per dose groups + control group). Exposures 

were nose-only for 6 hr/day. Two and three test article related deaths occurred in the 0.23 and 

0.74 mg/L groups. All other survived to scheduled necropsy. There were test article related 

rales in the 0.23 and 0.74 mg/L groups. Mean body weight loss and or reduced mean body 

weight gain were noted in males and females in the 0.74 mg/L group during day 0-1 through2-3. 

Mean body weights were generally reduced in males and females in the group through the entire 

study. Food consumption was reduced through the entire study in males and females of the 0.74 

dose group. Organ weights were unaffected by exposure to the test material. There were no 

treatment related macroscopic findings in the treated animals. Microscopic findings believed 

attributable to the test material included mucosal necrosis, suppurative inflammation and/or nasal 

exudate in males and females in the 0.23 and 0.74 mg/L groups. Since this is a localized effect, 

it was not considered as systemic toxicity.The NOAEL was determined to be 0.74 mg/L (191

mg/kg/day) under the conditions of this study.

Feeding Studies

A 7-day repeat dose feeding study was conducted with Wistar rats. Five male and female rats 

per dose were given 0, 51, 185, 420 and 1805 mg/kg/day in males and 0, 55, 201, 551 and 2122 

mg/kg/day for females. There was a concurrent, untreated control group. Methane sulfonic acid 

was administered in the feed ad libitum. There were no treatment related deaths during the 

study. There were no changes in food consumption, body weight change, liver and kidney 

weight as a result of exposure from the food. The NOAEL was determined to be 1805 and 2122 

mg/kg/day for males and females respectively.

In Vitro Genotoxicity (MRID 49396007)

(1) A reverse gene mutation assay was conducted using Salmonella typhimurium test strains TA 

1535, TA 1537, TA1538, TA98 and TA100. Test concentrations were 100, 500, 1000, 2500 and 
Page 8 of 25

5000 μg/plate and 5000 and 10000 μg/plate on TA98 and TA100. The test was conducted with 

and without metabolic activation. Methane sulfonic acid induced marked toxicity on two test 

strains TA98 and TA100 at 1000 μ/plate with and without metabolic activation. It was observed

that the S9 mix preparation precipitated at those two concentrations. Without metabolic 

activation at 5000 μg/plate a moderate toxic effect was noted on TA100 whereas on TA98 a 

decrease of the revertant colonies number with a sparse background was noted. Methanesulfonic 

acid with or without metabolic activation did not induce any increase of revertant colonies per 

plate at any dosage. 

(2) In another reverse gene mutation assay, Salmonella typhimurium strains TA98, TA100, 

TA1535, TA1537 and TA1538 were tested with and without metabolic activation with 

concentrations of 10, 32, 100, 316 and 1000 μg/plate. There were no increases in reversion to 

prototrophy in any of bacterial strains, either with or without metabolic activation. Inhibition of 

growth, observed as thinning of the background lawn of non revertant cells and reduction in 

colony numbers occurred in all strains with exposure to 1000 μ/plate which was determined to be 

the cytotoxic concentration. 

(3) In a third reverse gene mutation assay, Salmonella typhimurium strains TA100 and 1535 

were tested with concentrations of methane sulfonic acid of 384.4 1to 12300 μ/plate with and 

without metabolic activation. There were three replicates per dose. Metabolic activation was 

from S9-mix from Sprague Dawley rats treated with Aroclor 1254 with distilled water as the 

vehicle. The test was negative for test related revertant colonies. 

(4) A micronucleus assay was conducted using CD-1 mice. In a preliminary study a single oral 

gavage dose of 0, 125, 250, 500, 1000 and 2500 mg/kg. Subsequently, male and female mice 

were given a single dose of methane sulfonic acid of 20, 100 or 500 mg/kg. In all cases methane 

sulfonic acid was dosed orally in distilled water. Concurrent vehicle and positive control groups 

of mice were similarly dosed with distilled water or chlorambucil (30 mg/kg) respectively. Five 

males and five females from each group were sacrificed at 24 after treatment. Additional lots of 

five males and five females were given methane sulfonic acid at 0, 20, 100 or 500 mg/kg or the 

vehicle control and were sacrificed at 48 and 72 hours after treatment. Bone marrow smears on 

glass slides were stained and prepared for examination. At least 2000 erythrocytes per animal 

was taken for the presence of micronuclei. In the range finding study one female died 

approximately 30 seconds post-dose at 2500 mg/kg. One male was sacrificed in extremis 

approximately 30 minutes post-dose. Signs included hunched posture, piloerection, slow labored 

breathing and inability to move. At the 1000 mg/kg dose, one male was found dead at about 2 

hours post-dose. The remaining male and both females were killed in extremis approximately 21 

hours post-dose. All other animals survived to schedule sacrifice. Piloerection was noted in all 

animals in the 24 hour period following dosing at 500 mg/kg. No adverse reactions to treatment 

were recorded for any other group of animals dosed with methane sulfonic acid. 

In the main study two males dosed at 500 mg/kg were found dead approximately 212 hours postdose. One animal exhibiting piloerection, severe rales and loss of facial hair was killed 

approximately 48 hour post-dose. All surviving males in the 500 mg/kg groups showed piloerection. One male and one female showed rales. All other animals remained unsymptomatic.
Page 9 of 25

No significant variation in treated animals was reported in terms of micronucleated erythrocytes 

per animal. The chlorambucil group exhibited a significant increase of micronucleated 

polychromatic erythrocytes. No indication of bone marrow toxicity as evidence by depression of

bone marrow proliferation was noted in any group treated with methanesulfonic acid. 

Reproductive Toxicity (EPA. 2009)

In a combined reproductive/developmental toxicity screening test, Sprague-Dawley rats were 

administered methane sulfonic acid daily via gavage at 250, 500, or 1000 mg/kg/day. Males 

were dosed four weeks prior to mating, two weeks during the mating period and until sacrifice. 

Females were dosed four weeks prior to mating, two weeks during the mating period, through 

gestation (3 weeks), lactation until day 4 post-partum (pp) and until sacrifice (day 5 pp). No 

mortality was seen. Clinical signs in males included ptyalism (excessive salivation) at 1000 

mg/kg/day. There were no treatment-related effects on body weights, organ weight changes or 

histopathology. Methane sulfonic acid did not affect male and female reproductive performance 

or the progeny of the parental rats up to 1000 mg/kg/day.

NOAEL (parental/reproductive/offspring toxicity) = 1000 mg/kg/day (based on no effects at 

highest dose tested)

Developmental Toxicity (EPA. 2009)

(1) Female rats (25/dose; strain: Sprague-Dawley) were given daily oral gavage doses of 

methane sulfonic acid at 0, 25, 100 or 400 mg/kg/day from gestation day 6 through 15 (GD 6-

15). Based on the results of this study, the NOAEL was determined to be 400 mg/kg/day for 

maternal toxicity and developmental toxicity. 

NOAEL (maternal and developmental toxicity) = 400 mg/kg/day (based on no effects at highest 

dose tested)

(2) Female rats (8/dose; strain: Sprague-Dawley) were given daily oral gavage doses of the test 

substance at 0, 25, 50, 100, 200 or 300 mg/kg/day from GD 5 through 15. Treatment-related 

clinical signs included rales, labored respiration and gasping in the 100, 200 and 300 mg/kg/day 

groups. Findings of red material around the nose and/or mouth in the 100, 200 and 300 

mg/kg/day groups often correlated with occurrences of the aforementioned respiratory

abnormalities. Slight mean body weight losses and reduction in food consumption occurred in 

the 100, 200 and 300 mg/kg/day groups during GD 6-9 when evaluated on a group mean basis. 

Food consumption was slightly reduced in the 100, 200 and 300 mg/kg/day groups during GD 6-

9 when the group means were compared with the control group mean. This reduced food 

consumption seemed to be the result of a localized gastro-intestinal effect due to the dosage 

concentration to these groups and the corrosive nature of the test article. No effects on any other 

parameters were reported in the dams. No developmental toxicity was observed at dose levels up 

to 300 mg/kg/day.

LOAEL (maternal toxicity) = 100 mg/kg/day (based on slight changes in body weight and food 

consumption)

NOAEL (maternal toxicity) = 50 mg/kg/day

Sub chronic toxicity

No sub chronic toxicity studies are available on methane sulfonic acid. 

 
Page 10 of 25

Chronic toxicity and carcinogenicity

No chronic or carcinogenicity studies are available on methane sulfonic acid. 

Neurotoxicity

Although neurotoxicity studies have not been submitted for methane sulfonic acid, there is no 

evidence of neurotoxicity in any study in the toxicity database. No treatment-related effects 

were seen for parental toxicity or reproductive performance in a combined 

reproductive/developmental toxicity screening test at the highest dose tested (1000 mg/kg/day). 

Available prenatal developmental toxicity data showed no clinical sign of neurotoxicity at the

highest dose tested (400 mg/kg/day). In another developmental toxicity study, treatment-related 

clinical signs included rales, labored respiration and gasping at 100, 200 and 300 mg/kg/day, but 

these signs were considered secondary to corrosive nature of the chemical and not a 

neurotoxicity trigger Based on the above weight of evidence, methane sulfonic acid is not 

expected to be neurotoxic.

V. Toxicity Endpoint Selection 

The inhalation toxicity NOAEL was taken from the 5 day repeat dose inhalation toxicity study

where Sprague-Dawley rats were exposed to 0, 0.026, 0.082, 0.23 and 0.74 mg/L. There were no 

treatment related macroscopic findings in the treated animals. Microscopic findings believed 

attributable to the test material included mucosal necrosis, suppurative inflammation and/or nasal 

exudate in males and females in the 0.23 and 0.74 mg/L groups. The NOAEL was determined to 

be 0.74 mg/L (191 mg/kg/day) under the conditions of this study.

The inhalation NOAEL was converted to mg/kg/day using the convention described by Whalen 

in 2001 (Whalen, J. 2001. Policy: inhalation Toxicity Study Waivers for Active Ingredients and 

Formulations” Internal memorandum unpublished to OPP Toxicology Reviewers 12 SEPT 

2001, Health Effects Division/Office of Pesticide Programs.)

Inhalation Mg/L → Oral mg/kg/day = Rat

Mg/L * A * MV * D = mg/kg/day

 BW

A The inhalation:oral absorption ratio. In the absence of oral and inhalation absorption 

data, the ratio is assumed to be 1.

MV minute volume (L/min) (0.17 L/M average volume for Sprague-Dawley rats)

D Duration of daily exposure (minutes/day)(360 min/day = number of minutes in six hour 

exposure

BW Body weight = 0.236 kg (avg. weight for male and female Sprague-Dawley rats.

0.74 mg/L * 1 * 0.17 L/min * 360 min/day = 191 mg/kg/day. 

 0.236 kg
Page 11 of 25

The dermal toxicity NOAEL is selected from a developmental toxicity study (EPA, 2009).

Female Sprague-Dawley rats (25/dose; strain) were given daily oral gavage doses of methane 

sulfonic acid at 0, 25, 100 or 400 mg/kg/day from gestation day 6 through 15 (GD 6-15). Based 

on the results of this study, the NOAEL was determined to be 400 mg/kg/day for maternal 

toxicity and developmental toxicity. NOAEL (maternal and developmental toxicity) = 400 

mg/kg/day (based on no effects at highest dose tested).

The oral toxicity NOAEL is taken from the developmental toxicity study (EPA, 2009) with 

female Sprague-Dawley rats where the NOAEL was identified as 400 mg/kg/day. This dose is 

used for the dietary exposure assessment. 

VI. EXPOSURE

Based upon the requested use patterns, there are a number of ways by which humans may be 

exposed to methane sulfonic acid. Dietary exposure may occur as a result of residues transferred 

from treated food contact areas. Dietary exposure may occur as a result of residues remaining in 

treated food/dairy processing equipment or systems. Dermal and inhalation exposures may 

occur as a result of the use of sanitizing solutions which contain methane sulfonic acid. 

Exposures from the use of sanitizing solutions may be “occupational” exposures or “residential” 

exposures. Occupational exposures are those that result from persons who use/apply sanitizing 

solutions during the course of normal work related activities such as cleaning/disinfecting food 

contact preparation surfaces and food or dairy processing machinery or systems. “Residential” 

dermal and inhalation exposure may occur when individuals use cleaning solutions that contain 

methane sulfonic acid.

The proposed use on animals at 3 % concentration is for use in a disinfectant teat wash for dairy 

cattle, goats or sheep. This could result in dietary exposure. The use as a disinfectant teat wash 

contributes small amounts of methane sulfonic acid to food from meat and dairy products (inert 

dietary assessment attached).

 

Dietary Exposure/Risk Characterization

To assess dietary exposure resulting from residues on food contact surface areas, the Agency 

uses the Food and Drug Administration (FDA) Food Contact Surface Sanitizing Solution Dietary 

Exposure Assessment Model (FDA/CFSAN OPA: Chemistry Guidance – Sanitizing Solution 

version 1.1; January 1993; Office of Premarket Approval now Office of Food Additive Safety). 

The model is presented in the attachment. The model was run using the maximum concentration 

expected for methane sulfonic acid (5000 ppm) and adjusted for body weight according to 

current OPP policy. The results are summarized as follows:

EDI = (1 mg/cm2)(5000 ug methane sulfonic acid /1000 mg)(4000 cm2food contact surface area/person/day)(100% 

transfer rate of sanitizer to food) = 20,000μg/person/day = 20 mg/person/day

Mg/kg/day

Adult 20 mg/day ÷ 80 kg bw = 0.25 mg/kg/day

Child 20 mg/day ÷ 15 kg bw = 1.3 mg/kg/day

Margin of Exposure (MOE) = NOAEL (400 mg/kg/day)/Exposure
Page 12 of 25

Adult 400 mg/kg/day/0.25 mg/kg/day =1,600

Child 400 mg/kg/day/1.3 mg/kg/day = 310

Dietary Exposure from Clean-In-Place (CIP)

The assessment of dietary exposure as a result of food handling/processing machinery that is 

cleaned-in-place. The sanitizing solution is pumped through the plumbing of the machinery and 

not followed by a rinse with potable water. The algorithm, food mass to surface ratios and 

consumption levels of various foods are taken from Shamim (2006; MRID 49396009). 

Table 2.0 Food Mass to Surface Ratios and Consumption Levels

Food Food Mass to Surface Ratio

Gram/cm2

Food Consumption

Gram/person/day

Milk 6.6 124

Mayonnaise 64 9

Beer 150 182

Beverage Other 150 240

The algorithm used to calculate dietary exposure is:

The above assumptions and the following equations were used to calculate EDI and Dietary Daily Dose (DDD):

EDI Estimated Daily Intake (mg/p/day) = AR x RS x DIR x methane sulfonic acid-1 x F x 10-6 x CMF

DDD Dietary Daily Dose (mg/kg/day) = AR x RS x DIR x methane sulfonic acid ACID-1 x F x 10-6 x 

CMF/BW 

Where: 

AR = Application rate of sanitizer (ppm)

RS = Residual solution (mg/cm2)

MSA = Mass-surface area ratio (the treated surface that comes into contact with food) (g/cm2)

DIR = Daily intake rate of food in a given day (g/p/day)

F = Fraction of the pesticide transferred or migrated to food (unitless) (100%)

BW = Body weight (kg)

CMF = Calorie intake modification factor (100% adults; 64.4% Children)

Example of adult consuming milk:

5,000 (ppm) * 1 mg * 124 g * ( 6.6 g ) -1 * 1 * 10-6 * 1 (adult) = 0.094 mg/p/day 

 cm2 person/day cm2

0.094 mg/p/day ÷ 80 kg bw = 1.17-3 mg/kg/day 

0.094 mg/p/day ÷ 15 kg bw * 0.644 calorie intake modification factor = 4.04-3 mg/kg/day
Page 13 of 25

Table 3.0 Estimated Daily Intake from Clean-In-Place (Adult and Toddler)

Food Adult

80 kg bw

Toddler*

15 kg bw

mg/kg/day

Milk 1.17-3

 4.04

-3

Eggs/Mayonnaise 8.8-6

3.01-5

Beer 7.58-5 N/A

Beverages, Other 1

-4

3.43-4

 TOTAL 0.00135 0.00441

* Toddler includes 64.4% calorie intake modification from adult value = CMF

Estimated Dietary Exposure.

Estimated dietary exposures that might result from residues from treated dairy cattle, sheep or 

goats are estimated using the Agency’s dietary exposure model. Estimated residues are 

calculated for meat and dairy products. Results from the inert dietary exposure model (copy 

attached) indicate that the total daily exposure to the total U.S. population is 0.006755 mg/kg/day

(0.2% of the chronic reference dose). The most highly exposed subpopulation is for children 1-2 

years of age and the estimated total daily exposure is 0.029442 mg/kg/day (0.7% of the chronic 

reference dose).

Residential (Non-Occupational) Exposure/Risk Characterization

A final end-use dilution of methane sulfonic acid is stated to be 5000 ppm or 0.5 % 

(5000/1000000)*100% = 0.5. Rates of application are based upon the assumption of 0.5 % 

methane sulfonic acid in final end-use dilution.

Assessment of residential (non-occupational) exposure and risk is done using techniques taken 

from the “Amine Oxide 900439, (C10-16); C10-C18-Alkyldimethylamine oxides; Human Health 

Risk Assessment and Ecological Effects Assessment to Support Proposed Exemption from the 

Requirement of a Tolerance When Used as Inert Ingredients in Pesticide Formulations.” 

(Memorandum, 22 SEPT 09 L. Austin to P. Shah).

The following key assumptions were used in this assessment: 

 For the mopping scenario, the CMA dermal and inhalation unit exposure values for 

ungloved mopping were used (71.6 mg/lb inert. and 2.38 mg/lb inert, respectively). 

These values are based on data collected from six replicates mopping floors and receiving 

exposure via contact with the mop or with the bucket.

 For the wiping scenario, the CMA dermal and inhalation unit exposure values for 

ungloved wiping were used (2,870 mg/lb inert and 67.3 mg/lb inert, respectively). These 

values are based on data collected from six replicates (dental technicians) who used a 

finger pump sprayer to apply the product and then wiped the surfaces with a paper towel.
Page 14 of 25

1 gallon formulated pesticide solution*(8.34 lbs/gallon)*(0.5)% methane sulfonic acid)*(2 oz/ 128 oz dilution factor) = 

0.00065 lbs methane sulfonic acid in formulated pesticide solutions per day

0.13 gallon formulated pesticide solution*(8.34 lbs/gallon)*(0.5)% methane sulfonic acid = 0.0054 lbs methane sulfonic 

acid in formulated pesticide solutions per day

0.094 gallon formulated pesticide solution*(8.34 lbs/gallon)*(4% amine oxide) = 0.0039 lbs methane sulfonic acid in 

formulated pesticide solutions per day

 For aerosol spray, trigger pump and air deodorization scenarios, the PHED dermal and 

inhalation unit exposure values are 220 mg/lb inert and 2.4 mg/lb inert, respectively. The 

values are based on homeowners applying an aerosol insecticide to baseboards in 

kitchens and are representative of a handler wearing short pants and a short sleeve shirt, 

with no gloves.

The quantities handled/treated were estimated based on information from various sources 

and assumptions. 

 For the mopping scenarios, it was assumed that 1 gallon of diluted solution is used. HED 

assumes that cleaning products are assumed to have the same density as water (8.34 

lbs/gallon). While typical product concentrate directions indicate that 1 oz concentrated 

product per 1 gallon of water should be used, HED followed the AD SOP and assumed a 

dilution factor of 2 oz concentrated product/128 oz (1 gallon) of water for the residential 

handler risk assessment to represent heavy-duty cleaning formulations. This is 

comparable to the one quarter cup of cleaner diluted in one gallon of water as stated in 

AD’s SOP. Based on information from RD, the Agency assumed that the maximum 

percentage by weight in indoor products would be 0.5% methane sulfonic acid.

 For the wiping and trigger pump spray scenarios, it was assumed that 0.5 liter (0.13 gal) 

of ready-to-use (RTU) solution is used. For anti-microbial products, 0.5% methane 

sulfonic acid in product is assumed.

 For the aerosol foam spray, it is assumed that one can of product is used. For the aerosol 

spray/trigger pump, it is assumed that a 12 oz net weight product is used (0.094 gallons). 

0.5% methane sulfonic acid amine oxide inert in antimicrobial product assumed.

Dermal and inhalation absorption are assumed to be 100 %.

HED believes the duration of exposure for most homeowner applications of indoor cleaning 

products is believed to be best represented by the short-term duration (1 to 30 days) because the 

different scenarios (i.e. methods of application) are assumed to be episodic, not daily. In 

addition, homeowners are assumed to use different cleaning products with varying active and 

inert ingredients. 

Risk Summary
Page 15 of 25

For all residential handler scenarios, risk estimates are not of concern (i.e., MOEs are all greater 

than 100). A summary of the results are provided below in Tables 4.0, below.

The Agency believes that the handler scenarios assessed represent worse-case exposures 

and risks resulting from use of indoor cleaning products containing methane sulfonic acid 

in residential environments. 

Table 4.0 Estimated Residential “Handler” Exposures and Risks

Exposure 

Scenario 

(Formulation/ 

Application)

Application 

Rate1 (lb 

inert/ 

gallon)

Quantity 

Handled/ 

Treated 

per day2

Dermal 

Unit 

Exposure 

(mg/lb 

inert)3

Inhalation 

Unit 

Exposure 

(mg/ lb 

inert)3

Dermal 

Dose 

(mg/kg 

/day)4

Inhalation 

Dose 

(mg/kg/ 

day)5

Baseline 

Dermal 

MOE6

Baseline 

Inhalation 

MOE7

Indoor hard 

surface, Mopping 

(ST)

(CMA data)

0.00065 

lb/gal 1 gallon 71.6 2.38 0.00058 0.00018 690,000 1M

Indoor hard 

surface, Wiping 

(ST)

(CMA data)

0.0054 

lb/gal

0.13 

gallons 2870 67.3 0.025 0.00059 16000 324,000

Indoor hard 

surface, Aerosol 

spray (ST)

(PHED data)

0.0039

lb/gal

0.094 

gallons 

(12 oz)

220 2.4 0.001 0.00001 400,000 19M

1Application rates are based on maximum application rates of products containing methane sulfonic multiplied by 0.5% to 

convert from product application rate to inert application rate. 

2 Per AD (Revised Residential SOPs 2001) indoor house-hold products are assumed to be used at 1 gallon of solution for the 

mopping scenario, 0.5 L (0.13 gallon) of solution for the wiping scenario, and a 12 oz (0.094 gallon) can of trigger pump

3Unit Exposure data sources are identified in the exposure scenario column. All exposure scenarios assess exposure reflecting 

applicators wearing short-sleeved shirts and shorts and no respiratory protection.

4Daily Dermal Dose = (Dermal Unit Exposure (mg inert /lb inert handled) * Application Rate (lb /gal) * Quantity handled 

(gallons/day))/ Body Weight (80 kg) 

5 Daily Inhalation Dose = (Inhalation Unit Exposure (mg inert / lb inert) * Application Rate (lb /gal) * Quantity handled

(gallons/day)) / Body Weight (80 kg) 

6 Dermal MOE = PoD (NOAEL of 400 mg/kg/day)/ Daily dermal dose (mg/kg/day)

7

Inhalation MOE = PoD (NOAEL of 191 mg/kg/day) / Daily inhalation dose (mg/kg/day)

Occupational Exposure

Estimates of occupational exposures and risks were conducted using standard procedure 

developed by the Science Advisory Committee for Exposure (ExpoSAC)/Health Effects 

Division/Office of Pesticide Programs/EPA. The algorithm to estimate exposure is:

UE * AR * Units ÷ BW where

UE = Unit Exposures (mg/lb inert handled)

AR = Rate of Application (lb inert/gal) (0.5% * 8.34 lb/gal = 0.0417 lb inert/gal)

Units Treated = Quantity Handled (applied)/day (in this case gallons)

BW = Body Weight (80 kg assumed for average adult in U.S.)

Absorption via the dermal and inhalation route of exposure is assumed to be 100% therefore 

there is no correction for absorption factors.
Page 16 of 25

Table 5.0 Occupational Exposures and Risks

From Using Products Containing methane sulfonic acid 

Method of 

Application

Dermal 

Unit 

Exposure 

mg/lb 

handled

Inhalation

Unit

Exposure

mg/lb 

handled

Application 

Rate 

lb Methane 

sulfonic 

acid/gal

Quantity 

Handled/

Treated per 

day 

(gallons)

Dermal 

Dose

mg/kg/day

Inhalation

Dose

mg/kg/day

Dermal

MOE

Inhalation MOE 

Brush 220 0.28

0.0415

lb Methane 

sulfonic 

acid/

gallon

0.26 0.0297 3.8-5 13,500 5M

Foam 220 1.3 0.26 0.0297 1.8-4 13,500 1M

Immersion 11 1.89 10 0.057 9.8-3 7020 20,000

Trigger 

Pump Spray

220 0.681 0.26 0.0297 9.2-5 13,500 2.1M

Low 

pressure 

handwand

(clean) 

220 1.3 2 0.23 1.4-5 1740 1.4M

High 

pressure 

spray 

(sanitize)

11 0.12

40

0.23 2.5-9 1740 7.610

Sponge/mes

h wipe 

(clean) 

2870 67.3 0.26 0.39 9.1-3 1025 21,000

Cleaning in 

Place (CIP) 

(clean and 

sanitize) 

0.135 0.00361 10,000 0.7 0.019 571 10,000

1Dermal Unit Exposures are taken from Leighton (2005).

2

Inhalation Unit Exposures are taken from Smegal et al. (2006).

3Application rate based upon use-solution concentration of 5000 ppm methane sulfonic acid.

4Quantity handled per day taken from Smegal et al. (2006).

5Daily dermal and inhalation dose described above

6Dermal and inhalation Margin of Exposure (MOE) = Toxicological No Observed Adverse Effect Level (NOAEL) 

(mg/kg/day) ÷ Daily dermal or inhalation dose (mg/kg/day).
Page 17 of 25

VII. AGGREGATE RISK

In addition to consideration of single, acute exposures, the Agency also considers the possibility 

of aggregate exposures. Aggregate exposure refers to the sum(s) of individual exposures that 

might occur within a limited time frame. Aggregate exposure assessments are conducted for 

non-occupationally exposed individuals i.e., for adults and toddlers (residents). In this case 

aggregate exposures consider oral (dietary) exposure that might result from residues in meat or 

dairy products from cattle, sheep or goats that were subjected to a disinfectant teat wash, from 

residues from treated food handling surfaces and from non-occupational uses such as hard 

surface cleaning/wiping. Exposures from hard surface cleaning/wiping does not apply to 

toddlers. 

For adults the Agency uses the highest residential applicator exposure (indoor hard surface 

cleaning using hand wiping), dietary exposure from treated dairy animals as estimated by using

the dietary exposure model (results attached) and from estimated post-application exposures 

estimated by the FDA Food Surface Model. For toddlers, the Agency combines estimated 

exposures from the FDA model and the inert dietary exposure model.

Results from the inert dietary exposure model indicate that the total daily exposure to the total 

U.S. population is 0.006755 mg/kg/day (0.2% of the chronic reference dose). The most highly 

exposed subpopulation are children 1-2 years of age and the estimated total daily exposure is 

0.029442 mg/kg/day (0.7% of the chronic reference dose).

Table 6.0 Estimated Aggregate Non-Occupational Exposure

Source Adult

mg/kg/day

Toddler

mg/kg/day

FDA Food Surface Model 0.25 1.3

Daily intake from Clean in Place 0.00135 0.00441

Dietary exposures - meat and dairy products from cattle, sheep and 

goats

0.006755 0.029442

Non-Occupational Use from

 Hard surface wiping

0.025 N/A

 TOTAL 0.283 1.3

Margin of Exposure = NOAEL mg/kg/day ÷ Exposure (daily dose) mg/kg/day 

400 mg/kg/day/ 0.283 = 1680 (adult)

400 mg/kg/day/1.3 mg/kg/day = 307. 

The chronic RfD (cPAD) is 4.0 mg/kg/day. The total aggregate dose for non-occupational 

exposure occupies 0.07 % of the cPAD and therefore does not exceed the Agency’s level of 

concern. 
Page 18 of 25

IX. ENVIRONMENTAL FATE & EFFECTS

Discussion of environmental fate and effects is taken from EPA (2008). The conclusions in the 

earlier evaluation is not expected to have changed and thus are relied upon herein. The relative 

distributions of chemicals released into the environment can be estimated using the Level III 

Fugacity Model. This model (Table 6) shows that methane sulfonic acid will partition primarily 

to soil and water, with a higher affinity to soil, and a negligible portion to air and sediment.

(HPV, 2008)

Table 7. Level III Fugacity Estimated

Fugacity Level III Methanesulfonic Acid

Air (%) <1

Water (%) 40.7

Soil (%) 59.2

Sediment (%) < 1

Methane sulfonic acid is a strong acid with pKa of -1.92. This value indicates that methane 

sulfonic acid will exist as an anion in moist soils and water. Methane sulfonic acid is minimally 

volatile from water since anions do not volatilize. Methane sulfonic acid is highly mobile in soil 

with a Log Koc of 0.0 and biodegradation occurs rapidly; 100% of theoretical biochemical 

oxygen demand in 28 days using an activated sludge inoculum. If released to the atmosphere, 

methane sulfonic acid will degrade by reaction with photochemically produced hydroxyl radicals 

with an estimated half-life of approximately 58 days. Methane sulfonic acid is expected to have 

low persistence and low bioaccumulation potential. (HPV, 2008)

The evaluation of available aquatic toxicity data for fish, aquatic invertebrates and aquatic plants 

indicates that the potential acute hazard of methane sulfonic acid to fish and aquatic plants is 

low and to aquatic invertebrates is moderate based on the following studies; in acute toxicity 

studies with water fleas (Daphnia magna) the 48-hr EC50 was 260 mg ai/L, with an NOEC of 

120 mg/L; the 96-hr LC50 in rainbow trout (Oncorhynchus mykiss) was 73 mg ai/L with an 

NOEC of 56 mg/L; the NOEC 96-hr LC50 in fresh water green algae (Selenastrum 

capricornutum) was 5.8 mg/L; and the 72-hour EC50 (biomass) (Pseudokirchneriella 

subcapitata) was 14 mg/L (HPV, 2008).

Of all the organic sulfonic acids, methane sulfonic acid has the lowest biochemical oxygen 

demand. It is readily biodegradable, ultimately forming sulfate and carbon dioxide; and is not 

expected to bioaccumulate. Methane sulfonic acid dissolves easily in water and can therefore be 

extracted from the organic phase with only a small amount of water. This allows the acid to be 

readily recycled (BASF, 2008).

Based on the these studies and the biodegradability of methane sulfonic acid to form sulfate and 

carbon dioxide, effects of concern to non-target aquatic organisms resulting from the use of this 

substance as an inert ingredient are not anticipated in the environment. 
Page 19 of 25

X. DETERMINATION OF SAFETY

Section 408(b)(2)(c) of FFDCA provides that EPA shall apply an additional tenfold (10X) 

margin of safety for infants and children in the case of threshold effects to account for 

prenatal and postnatal toxicity and the completeness of the database on toxicity and 

exposure unless EPA determines based on reliable data that a different margin of safety 

will be safe for infants and children. This additional margin of safety is commonly 

referred to as the FQPA safety factor (SF). In applying this provision, EPA either retains 

the default value of 10X, or uses a different additional safety factor when reliable data 

available to EPA support the choice of a different factor. 

Based on lack of any systemic toxicity and the irritating property of the chemical which 

precluded testing at a higher doses, EPA has concluded that there are no toxicological 

endpoints of concern for the U.S. population, including infants and children, and has 

conducted a quantitative assessment. As part of its qualitative assessment, the Agency 

did not use safety factors for assessing risk, and no additional safety factor is needed for 

assessing risk to infants and children. 

Taking into consideration the available information, EPA concludes that the additional 1X FQPA 

safety factor will be retained.

XI. 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," 

http://www.eh.doe.gov/oepa/guidance/justice/eo12898.pdf).

As a part of every pesticide risk assessment, OPP considers a large variety of consumer 

subgroups according to well-established procedures. In line with OPP policy, HED estimates 

risks to population subgroups from pesticide exposures that are based on patterns of that 

subgroup’s food and water consumption, and activities in and around the home that involve 

pesticide use in a residential setting. Extensive data on food consumption patterns are compiled 

by the USDA under the Continuing Survey of Food Intake by Individuals (CSFII) and are used 

in pesticide risk assessments for all registered food uses of a pesticide. These data are analyzed 

and categorized by subgroups based on age, season of the year, ethnic group, and region of the 

country. Additionally, OPP is able to assess dietary exposure to smaller, specialized subgroups 

and exposure assessments are performed when conditions or circumstances warrant. Whenever 

appropriate, non-dietary exposures based on home use of pesticide products and associated risks 

for adult applicators and for toddlers, youths, and adults entering or playing on treated areas 

post-application are evaluated. Further considerations are currently in development as OPP has 

committed resources and expertise to the development of specialized software and models that 

consider exposure to bystanders and farm workers as well as lifestyle and traditional dietary 

patterns among specific subgroups.
Page 20 of 25

XII. HUMAN STUDIES

This assessment does not rely on any studies in which human subjects were intentionally 

exposed to a pesticide. 

XIII. INTERNATIONAL LIMITS: None

XIV. RISK CHARACTERIZATION

Methane sulfonic acid has moderate acute oral toxicity to rats, and moderate acute dermal 

toxicity to rabbits. Methane sulfonic acid is corrosive to mouse skin, extremely corrosive to the 

eye, but showed no evidence of dermal sensitization. Following repeated nose-only 

inhalation exposures in rats to low concentrations, clear evidence of portal-of-entry effects, such 

as histopathological lesions in the nasal turbinates were observed. In a 7-repeat dose oral feeding 

study in rats, no systemic toxicity was observed at doses up to 1805 mg/kg/day. No effects were 

seen for parental toxicity, offspring/developmental toxicity or reproductive performance in a 

combined reproductive/developmental toxicity screening test at doses up to 1000 mg/kg/day. In 

one developmental toxicity study in rats, no parental systemic or developmental toxicity was 

observed at doses up to 400 mg/kg/day. Available prenatal developmental toxicity data showed 

some evidence of slight maternal toxicity but no developmental effects. Methane sulfonic 

acid was not mutagenic and did not induce chromosomal aberrations. There are no metabolism, 

chronic toxicity or carcinogenicity studies available on methane sulfonic acid. However, based 

on the lack of systemic toxicity at 1000 mg/kg/day and above in a combined 

reproductive/developmental screening study and 7-day dietary study, and the lack of 

mutagenicity concern, there are low concerns for cancer. 

Although neurotoxicity studies have not been submitted for methane sulfonic acid there is no 

evidence of neurotoxicity in any study in the toxicity database including a combined 

reproductive/developmental toxicity screening test and prenatal developmental toxicity studies. 

The inhalation toxicity NOAEL was taken from the repeat-dose inhalation study discussed 

earlier. There were no treatment related macroscopic findings in the treated animals. 

Microscopic findings believed attributable to the test material included mucosal necrosis, 

suppurative inflammation and/or nasal exudate in males and females in the 0.23 and 0.74 mg/L 

groups. The NOAEL was determined to be 0.74 mg/L (191 mg/kg/day).

The dermal toxicity NOAEL is selected from a developmental toxicity study. Based on the 

results of this study, the NOAEL was determined to be 400 mg/kg/day for maternal toxicity and 

developmental toxicity. NOAEL (maternal and developmental toxicity) = 400 mg/kg/day

(based on no effects at highest dose tested).

The oral toxicity NOAEL is taken from the developmental toxicity study with female SpragueDawley rats where the NOAEL was identified as 400 mg/kg/day. This dose is used for the inert 

dietary exposure assessment. 

Based upon the requested use patterns, humans may be exposed to methane sulfonic acid. 

Dietary exposure may occur as a result of residues transferred from treated food contact areas. 
Page 21 of 25

Dietary exposure may occur as a result of residues remaining in treated food/dairy processing 

equipment or systems. Dermal and inhalation exposures may occur as a result of the use of 

sanitizing solutions which contain methane sulfonic acid. Exposures from the use of sanitizing 

solutions may be “occupational” exposures or “residential” exposures. Occupational exposures 

are those that result from persons who use/apply sanitizing solutions during the course of normal 

work related activities such as cleaning/disinfecting food contact preparation surfaces and food 

or dairy processing machinery or systems. “Residential” dermal and inhalation exposure may 

occur when individuals use cleaning solutions that contain methane sulfonic acid.

The proposed use on animals at 3 % concentration is for use in a disinfectant teat wash for dairy 

cattle, goats or sheep. This could result in dietary exposure. The current Agency assessments of 

dietary exposure are believed to be conservative (protective) enough to negate any health 

concerns as a result of that use pattern. It is not further considered in a quantitative sense.

Margins of Exposure for residential exposures (including aggregate exposure) and for 

occupational exposures are greater than 100 which do not exceed the Agency’s level of concern.

Discussion of environmental fate and effects is taken from EPA (2008). The conclusions in the 

earlier evaluation is not expected to have changed and thus are relied upon herein. The relative 

distributions of chemicals released into the environment can be estimated using the Level III 

Fugacity Model. This model (Table 6) shows that methane sulfonic acid will partition primarily 

to soil and water, with a higher affinity to soil, and a negligible portion to air and sediment. 

Methane sulfonic acid is a strong acid with pKa of -1.92. This value indicates that methane 

sulfonic acid will exist as an anion in moist soils and water. Methane sulfonic acid is minimally 

volatile from water since anions do not volatilize. Methane sulfonic acid is highly mobile in soil 

with a Log Koc of 0.0 and biodegradation occurs rapidly; 100% of theoretical biochemical 

oxygen demand in 28 days using an activated sludge inoculum. If released to the atmosphere, 

methane sulfonic acid will degrade by reaction with photochemically produced hydroxyl radicals 

with an estimated half-life of approximately 58 days. Methane sulfonic acid is expected to have 

low persistence and low bioaccumulation potential. 

Based upon the findings presented earlier in the human health and risk assessment and the 

findings regarding environmental fate and effects, the Agency approves of the requested uses of 

methane sulfonic acid. As such, methane sulfonic acid may be formulated into products for use 

as an acid cleaner in pesticide formulations with a limit not to exceed 3 % final end use 

concentration when used on animals [as a disinfectant teat wash for dairy cattle, goats or sheep]; 

and not to exceed 0.5% (5,000 ppm in use-dilution solution) when used in antimicrobial 

formulations for food-contact surface sanitizing in public eating places, dairy-processing 

equipment, and food-processing equipment and utensils. 

 
Page 22 of 25

REFERENCES

EPA. 2009. United States Environmental Protection Agency. Decision Document for Inert

Approval: Methane sulfonic acid (CAS No. 75-75-2) – Non-Food Use. 

791198.DEC1.doc.

MRID 49396007. 2014. MRID 49396007 cites “Except from IUCLID Data Set for 

Methansulfonic Acid; OPPT # 201-16750B; Received at OPPT NCIC on 25 Sept. 2008. 

Extracted from Final HPV Assessment Report on Methanesulfonic Acid CAS NO. 75-

75-2 Submitted by: Arkema Inc. 20 MAY 2008. 

http://www.epa.gov/chemmrtk/pubs/summaries/methanes/c1424rt3.pdf

Shamim, A. N. 2006. “Dietary Risk Assessment for Alkyl Dimethyl Benzyl Ammonium 

Chloride (ADBAC) for Reregistration Eligibility Decision (RED) Process” EPA 

interoffice memorandum to Jacqueline Campbell-McFarlane. 27 July 2006.

Smegal, D., T. Milano, R. Quick, R. Petrie, C. Walls, N. Shamim, and K. Leifer. “ Alkylbenzene 

Sulfonates (ABS) Risk Assessment for the Reregistration Eligibility Decision (RED) 

Document”, PC Codes: 079010, 190116 and 098002(active); 790102, 790116, 790101 

(inert) Case No. 4006. DP Barcode: D330338. Unpublished memorandum. Health 

Effects Division/OPP.
Page 23 of 25

ATTACHMENT

FDA Food Contact Surface Sanitizing Solution Dietary Exposure 

Assessment Model

(FDA/CFSAN OPA: Chemistry Guidance – Sanitizing Solutions “Sanitizing Solutions: 

Chemistry Guidelines for Food Additive Petitions” version 1.1; January 1993; Office of 

Premarket Approval now Office of Food Additive Safety).

EDI (mg/day) = (1 mg/cm2)(ug chemical/1000 mg)(4000 cm2/person/day) = μg/person/day/1000 mg/μg

EDI (mg/day) = (1 mg/cm2) (ppm inert; in this case expressed as 5000 ug methane sulfonic acid/1000 mg)(4000 

cm2/person/day = 20,000 ug/person/day = 20 mg/person/day

DDD (mg/kg/day) = 

Adult 20 mg/day ÷ 80 kg bw = 0.25 mg/kg/day

Child 20 mg/day ÷ 11 kg bw = 1.3 mg/kg/day

Margin of Exposure (MOE) = NOAEL (400 mg/kg/day)/Exposure

Adult 400 mg/kg/day/0.25 mg/kg/day = 1600

Child 400 mg/kg/day/1.3 mg/kg/day = 310

It is assumed that 100% of the residue is transferred to the exposed individual

Where: 

AR = Application rate (ppm)

RS = Residual solution (mg/cm2)

SA = Surface area of the treated surface which comes into contact with food (cm2)

BW = Body weight (kg)

The input parameters listed in Table below and equations 1 and 2 above are used to calculate EDI, DDD and %PAD 

for the two population subgroups (average adult and infants/children)

Input Parameters for Food Contact Surface Sanitizing Solution Dietary Exposure 

Assessment 

Parameter

Value

Rationale

Residual Solution on 

Surface 1 mg/cm2 FDA assumption

Area of Treated Surface 4,000 cm2 FDA assumption for food 

utensils/surfaces

concentration in diluted 

solution 5000 ppm 

Diluted Solution concentration, based 

on maximum concentration (expressed 

in ppm).

Fraction Transferred 100% US EPA Antimicrobials Div. SOP for 

Residential Exposure 3.1.1
Page 24 of 25

Body Weight (kg) 

Average adult =

Child =

80

15

EPA (2011) Hot sheet 31

US EPA Ver. 3.16, 03-08-d

DEEM-FCID Chronic analysis for INERTS NHANES 2003-2008 2-day

Residue file name: J:\INERTS_57ACTIVE_BeefGoatSheepMilk.R08

 Adjustment factor #2 NOT used.

Analysis Date 06-04-2015/07:56:39 Residue file dated: 06-04-2015/07:55:52

Reference dose (RfD, Chronic) = 4 mg/kg/day

COMMENT 1: Inert 57 active ingredients + MMP

====================================================================

===========

 Total exposure by population subgroup

-------------------------------------------------------------------------------

 Total Exposure

 -----------------------------------

 Population mg/kg Percent of 

 Subgroup body wt/day Rfd 

-------------------------------------- ------------- ----------------

Total US Population 0.006755 0.2%

Hispanic 0.007980 0.2%

Non-Hisp-White 0.006625 0.2%

Non-Hisp-Black 0.006040 0.2%

Non-Hisp-Other 0.006985 0.2%

Nursing Infants 0.002362 0.1%

Non-Nursing Infants 0.009925 0.2%

Female 13+ PREG 0.005348 0.1%

Children 1-6 0.022188 0.6%

Children 7-12 0.010994 0.3%

Male 13-19 0.007426 0.2%

Female 13-19/NP 0.005218 0.1%

Male 20+ 0.005144 0.1%

Female 20+/NP 0.003992 0.1%

Seniors 55+ 0.004110 0.1%

All Infants 0.007591 0.2%

Female 13-50 0.004410 0.1%

Children 1-2 0.029442 0.7%

Children 3-5 0.018965 0.5%

Children 6-12 0.011748 0.3%

Youth 13-19 0.006306 0.2%

Adults 20-49 0.004880 0.1%

Adults 50-99 0.004108 0.1%

Female 13-49 0.004436 0.1%
Page 25 of 25

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