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HPMTS 

REGISTRATION REVIEW DECISION

PRODUCT CHEMISTRY, ENVIRONMENTAL FATE AND

 ECOLOGICAL EFFECTS SUMMARY

PC Code: 035604; Case No. 3033

Introduction: 

HPMTS is an organosulfur compound known by the trade name Busan 74. Chemically, 

HPMTS (2-Hydroxypropyl methanethiosulfonate) is Methanesulfonothioic acid, S-(2-

hydroxypropyl) ester. It is a transparent, amber colored liquid with a sour, pungent, vegetablelike odor, is completely soluble in water and has a high vapor pressure of 1.78 mm Hg @ 25°C. 

HPMTS (80% TGAI) was first registered with the EPA on February 2, 1971. Currently 

there is only one active product registered for formulating use and there are no registered end-use 

products. See Table 1 below. A Reregistration Eligibility Decision (RED) was issued by EPA in 

December 1995. 

The chemical name for the active ingredient in this registration review case is 2-

hydroxypropyl methanethiolsulfonate (HPMTS). Busan 74 is a trade name that refers to a 

product, which is no longer registered, that contained HPMTS as an active ingredient. Although 

the name for this registration review case is Busan 74, hence forward this case will be referred to 

by its chemical name, 2-hydroxypropyl- methanethiolsulfonate (HPMTS).

Table 1. Registered Active Products of HPMTS

Registration Number Registration 

Name Company Name Formulation Type 

% of Active 

Ingredient 

1448-31 HPMTS Buckman 

Laboratories Inc.

Formulating Use 

Only 

80% 

Use Patterns: 

For Formulating Use Only. 

No use sites or use patterns are listed on the label. 

HPMTS 

EPA Reg. No.: 1448-31 

Active Ingredient: 2-Hydroxypropyl methanethiosulfonate 80% 

For formulating use only. 
 

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Science Findings

The Agency has conducted a review of the available product chemistry, environmental 

fate and ecotoxicity data for HPMTS. The findings are summarized below. 

Product Chemistry Summary 

The data submitted pertaining to the physical and chemical characteristics of the active 

ingredient, HPMTS are adequate. All product chemistry data requirements have been fulfilled

for the active ingredient HPMTS. Therefore, the Agency does not anticipate needing additional 

product chemistry data for HPMTS at this time. Tables 2 and 3 contain the chemical and 

physical properties of HPMTS. 

Table 2. Chemical Identity of HPMTS 

Chemical Name HPMTS 

Common Names Methanesulfonothioic acid, S-(2-hydroxypropyl) ester 

Synonyms 2-Hydroxypropyl methanethiosulfonate (HPMTS) 

Methanesulfonic acid, thio-, S-(2-hydroxypropyl) ester 

S-(2-Hydroxypropyl) thiomethanesulfonate 

Trade Name Busan 74 

Molecular Weight 171.25 g/mole 

PC Code 035604 

CAS Registry Number 30388-01-3 

Molecular Formula C4H10O3S2

Registration Review Case No. 

Registration Review Case Name 

3033 

Busan 74 

Classification Sulfonate 

Thiosulfonates 
Table 2. Chemical Identity of HPMTS 

Molecular Structure: 

CH3CH(OH)CH2SSO2CH3 

Table 3. Product Chemistry Data Summary of HPMTS (TGAI 80 %) 

 

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Guideline No. Physical and Chemical 

Properties 

Value 

830.1550 Product identity and 

composition 

Refer to Table 2 

830.1600 Description of materials 

used to produce the product 

CBI 

830.1620 Description of production 

process 

CBI 

830.1650 Description of formulation 

process 

CBI 

830.1670 Discussion of formation of 

impurities 

CBI 

830.1700 Preliminary analysis CBI 

830.1750 Certified limits CBI 

830.1800 Enforcement analytical 

method 

Gas chromatography 

830.1900 Submittal of samples NA 

830.6302 Color Light yellow/brilliant yellow 

830.6303 Physical State Transparent, amber liquid with no trace of solid or sediment. 

830.6304 Odor Strong sour, pungent vegetable-like odor 

830.6313 Stability to sunlight, normal 

and elevated temperature, 

metals/metal ions 

% Change from nominal after 4 days exposure to: 

Iron: -4.01% 

Copper: -0.14% 

Aluminum: -1.63% 

After 24 cumulative hours exposure to sunlight: -1.11 % 

Some evidence of separation after 18 hours in 1:20 water 

solution. 

830.6314 Oxidation/Reduction: 

Chemical Incompatibility 

Not required; product does not contain any oxidizing or reducing 

agent. 

830.6315 Flammability/Flame Not required; product does not contain any combustible liquids. 
 

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Guideline No. Physical and Chemical 

Properties 

Value 

extention 

830.6316 Explodability Not required; product is not potentially explosive. 

830.6317 Storage Stability Stable under all storage conditions The concentration of HPMTS 

decreased 2.8% when stored at room temperature over a 12-month 

test period. 

830.6319 Miscibility Not required, product will not be diluted with petroleum solvents. 

830.6320 Corrosion Characteristics No signs of corrosion were noted in the packaging material over 

the one-year storage period at room temperature. 

830.6321 Dielectric breakdown 

voltage 

N/A

830.7000 pH 3.7 at 22°C 

830.7050 UV/Visible Light 

Absorption 

Not Required for TGAI 

830.7100 Viscosity Not determinable by standard method; test material crystallized at 

20 °C 

830.7200 Melting point N/A; product is a liquid 

830.7220 Boiling point 164°C 

830.7300 Density 1.2893 at 22°C 

1289.3 (1.2893 relative density) kg/m3 @ 22 °C 

830.7370 Dissociation Constant Not applicable for this active ingredient 

830.7550 Partition coefficient (noctanol/water) Not applicable for organic, polar active ingredients 

830.7840 Solubility in water At concentrations > 40%, soluble at any concentration; 

at concentrations < 40%, not completely soluble 

Completely soluble in water 

830.xxxx Solubility in organic 

solvents 

Ethanol Miscible in all 

proportions 

Hexane <16 mg in 100 ml 

C8-18 Fatty Acids Mean fat solubility 

at 37°C is 

5.42+0.04 g/100 g 

830.7950 Vapor pressure 1.40 mm Hg at 20°C and 1.70 mm Hg at 25°C 

TGAI: Total vapor pressure (20°C) =1.4 mm Hg 

TGAI: Total vapor pressure (25°C) =1.78 mm Hg 

Total vapor pressure = vapor pressure of HPMTS + impurities 

N/A = Not applicable; TGAI=Technical Grade Active Ingredient; CBI= Confidential Business Information 
Environmental Fate Summary 

2-Hydroxypropyl methanethiosulfonate (HPMTS) is an antimicrobial for formulating 

use. The Agency has reviewed one environmental fate study (hydrolysis) for HPMTS and the 

results are summarized in Table 4. The Agency’s conclusion for the hydrolysis study is as 

follows. 

Hydrolysis (Abiotic) 

2-Hydroxypropyl methanethiosulfonate hydrolyzed with half-lives of >30 days at pH 5, 

8.5-9.9 hours at pH 7 and 5.4-6.1 minutes at pH 9 in sterile aqueous buffered solutions that were 

incubated at 25°C in darkness for up to 30 days. The major degradates di-(2-hydroxyisopropyl) 

disulfide and di-(2-hydroxypropyl) disulfide were isolated from all three solutions. The 

hydrolysis study is acceptable and satisfies the hydrolysis data requirements (OPP 161-1) for 

HPMTS. 

Table 4. Environmental Fate Data Summary for HPMTS

OPP 

Guideline Fate Studies Half-Life Degradates Study Status 

161-1 

Hydrolysis 

pH 5 

pH 7 

pH 9 

(101 mg/L) 

>30 Days 

8.5-9.9 Hours 

5.4-6.1 Minutes 

Major Degradates: 

di-(2-hydroxyisopropyl) 

disulfide 

di-(2-hydroxypropyl) 

disulfide 

Acceptable

Table 5. Degradates of HPMTS 

Di-(2-hydroxypropyl) disulfide

 

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Water Quality 

HPMTS is not identified as a cause of impairment for any water bodies listed as impaired 

under section 303(d) of the Clean Water Act, based on information provided at 

http://iaspub.epa.gov/tmdl_waters10/attains_nation_cy.cause_detail_303d?p_cause_group_id=88

5 . In addition, no Total Maximum Daily Loads (TMDL) have been developed for HPMTS, 

based on information provided at 

http://iaspub.epa.gov/tmdl_waters10/attains_nation.tmdl_pollutant_detail?p_pollutant_group_id

=885&p_pollutant_group_name=PESTICIDES . More information on impaired water bodies 

and TMDLs can be found at http://www.epa.gov/owow/tmdl/. The Agency invites submission 

of water quality data for this pesticide. To the extent possible, data should conform to the quality 

standards in Appendix A of the OPP Standard Operating Procedure: Inclusion of Impaired 

Water Body and Other Water Quality Data in OPP’s Registration Review Risk Assessment and 

Management Process (see: http://www.epa.gov/oppfead1/cb/ppdc/2006/november06/session1-

sop.pdf ), in order to ensure they can be used quantitatively or qualitatively in pesticide risk 

assessments. 

Ecological Effects Summary 

The Agency has reviewed seven ecotoxicology studies for HPMTS. The seven studies 

submitted on the HPTMS active ingredient were all found to be acceptable for use in a hazard 

assessment. Ecotoxicity guideline studies and the results are summarized in Table 6. The 

Agency's conclusions for the avian and aquatic effects studies are as follows. 

(1) Terrestrial Data 

(a) Avian Subacute Dietary Toxicity 

HPMTS is slightly toxic to birds on a subacute dietary basis. The guideline requirement 

is fulfilled. 

(2) Aquatic Data 

(a) Freshwater Fish Toxicity 

The results of the aquatic toxicity studies indicate that HPMTS is slightly toxic to both 

cold and warm freshwater fish. The guideline requirement for acute toxicity testing of the 

technical on freshwater fish is fulfilled. 

(b) Freshwater Invertebrate Toxicity 

The results of the aquatic invertebrate toxicity studies indicate that HPMTS is moderately 

to slightly toxic to Daphnia. The guideline requirement for acute toxicity testing on 

freshwater invertebrates is fulfilled. 

HPMTS is slightly toxic to avian species on a subacute dietary basis, slightly toxic to 

fish, and slightly to moderately toxic to aquatic invertebrates. Ecotoxicity data are adequate to 

provide the Agency with sufficient information to determine appropriate label precautions. 
 

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Table 6. Ecotoxicity Data Summary for HPMTS

GUIDE 

LINE 

COMMON 

NAME 

TAXONOMIC 

NAME TYPE % AI 

STUDY

TIME 

DOSE

TYPE

TOXI

CITY 

TOX 

LEVEL NOEL STUDY STATUS 

TOX 

 CATEGORY

Avian Subacute Dietary Toxicity

850.2200 

71-2a 

Bobwhite 

quail 

Colinus 

virginianus 

D 79.8 8 D LC50 >5000

(3991 

 ppm ai)

PPM >5000 

(3991 

 ppm ai)

Core Slightly toxic

850.2200 

71-2b 

Mallard 

duck 

Anas 

platyrhynchos 

D 79.8 8 D LC50 >5000

(3991 

ppm ai)

PPM >5000 

(3991 

ppm ai) 

Core Slightly toxic

Freshwater Fish Acute Toxicity 

850.1075 

72-1c 

Rainbow 

trout 

Oncorhynchus 

mykiss 

F 81.4 96 hr LC50 28 PPM 15.8 Core Slightly toxic

850.1075 

72-1b 

Bluegill 

sunfish 

Lepomis 

macrochirus 

F 81.4 96 hr LC50 38.2 PPM 17 Core Slightly toxic

850.1075 

72-1b 

Bluegill 

sunfish 

Lepomis 

macrochirus 

S 80 96 hr LC50 78 PPM 32 Suppl Slightly toxic

Freshwater Invertebrate Acute Toxicity 

850.1010 

72-2a 

Water flea Daphnia 

magna 

F 81.4 96 hr EC50 3.13 PPM 1.39 Core Moderately 

toxic 

850.1010 

72-2a 

Water flea Daphnia 

magna 

S 80 48 hr EC50 12 PPM 8 Suppl Slightly toxic

Ecological Effects Risk Assessment 

There are no registered end-use products and the registered manufacturing use product 

will not result in human or environmental exposure because it is for formulating use only. 

Therefore, an ecological risk assessment is not needed in support of registration review. 

Risk to Threatened and Endangered Species 

Labels may be categorized into two types: labels for manufacturing uses and label for 

end-use products. Manufacturing use products are not used directly in the environment, but 

instead, are used to make formulated or end-use products. End-use products are used to control 

a pest and carry label instructions that indicate how the product may legally be used. There are 

currently no registered end-use products for HPMTS; the only registration is for the 

manufacturing use product. There is no environmental exposure anticipated and the Agency has 

determined the registration of the manufacturing use product will have "no effect" (NE) on 

endangered or threatened terrestrial or aquatic species, or their designated critical habitats, as 

listed by the U.S. Fish and Wildlife Service (USFWS) and the National Oceanic and 

Atmospheric Administration (NOAA). Therefore, no additional environmental risk assessment 

is anticipated to be undertaken. However, the EPA will review any comments made by the 

public on this document and will conduct an environmental risk assessment, if new information 

warrants such action. If such a decision is made, the environmental risk assessment will 

conclude that the registered pesticide's use has “no effect” or “may affect” federally listed 

threatened or endangered species (listed species) or their designated critical habitats. When an 
 

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assessment concludes that a pesticide’s use “may affect” a listed species or its designated critical 

habitat, the Agency will consult with the U.S. Fish and Wildlife Service and/or National Marine 

Fisheries Service (the Services), as appropriate. 

Environmental Fate and Ecotoxicity Data Gaps and Anticipated Work 

No data gaps.