U.S. Environmental Protection Agency Hazard Characterization Document September, 2014 SCREENING-LEVEL HAZARD CHARACTERIZATION 2,5-Dihydrothiophene 1,1-Dioxide (CASRN 77-79-2) The High Production Volume (HPV) Challenge Program1 was conceived as a voluntary initiative aimed at developing and making publicly available screening-level health and environmental effects information on chemicals manufactured in or imported into the United States in quantities greater than one million pounds per year. In the Challenge Program, producers and importers of HPV chemicals voluntarily sponsored chemicals; sponsorship entailed the identification and initial assessment of the adequacy of existing toxicity data/information, conducting new testing if adequate data did not exist, and making both new and existing data and information available to the public. Each complete data submission contains data on 18 internationally agreed to "SIDS" (Screening Information Data Setl'2) endpoints that are screening-level indicators of potential hazards (toxicity) for humans or the environment. The Environmental Protection Agency's Office of Pollution Prevention and Toxics (OPPT) is evaluating the data submitted in the HPV Challenge Program on approximately 1400 sponsored chemicals by developing hazard characterizations (HCs). These HCs consist of an evaluation of the quality and completeness of the data set provided in the Challenge Program submissions. They are not intended to be definitive statements regarding the possibility of unreasonable risk of injury to health or the environment. The evaluation is performed according to established EPA guidance2,3 and is based primarily on hazard data provided by sponsors; however, in preparing the hazard characterization, EPA considered its own comments and public comments on the original submission as well as the sponsor's responses to comments and revisions made to the submission. In order to determine whether any new hazard information was developed since the time of the HPV submission, a search of the following databases was made from one year prior to the date of the HPV Challenge submission to the present: (ChemID to locate available data sources including Medline/PubMed, Toxline, HSDB, IRIS, NTP, AT SDR, IARC, EXTOXNET, EPA SRS, etc.), STN/CAS online databases (Registry file for locators, ChemAbs for toxicology data, RTECS, Merck, etc.), Science Direct and ECHA4. OPPT's focus on these specific sources is based on their being of high quality, highly relevant to hazard characterization, and publicly available. OPPT does not develop HCs for those HPV chemicals which have already been assessed internationally through the HPV program of the Organization for Economic Cooperation and Development (OECD) and for which Screening Initial Data Set (SIDS) Initial Assessment Reports (SIAR) and SIDS Initial Assessment Profiles (SIAP) are available. These documents are presented in an international forum that involves review and endorsement by governmental 1 U.S. EPA. High Production Volume (HPV) Challenge Program; http://www.epa.gov/chemrtk/index.htm. 2 U.S. EPA. HPV Challenge Program - Information Sources; http://www.epa.gov/chemrtk/pubs/general/guidocs.htm. 3 U.S. EPA. Risk Assessment Guidelines; http://cfpub.epa.gov/ncea/raf/rafguid.cfm. 4 European Chemicals Agency, http://echa.europa.eu. ------- U.S. Environmental Protection Agency Hazard Characterization Document September, 2014 authorities around the world. OPPT is an active participant in these meetings and accepts these documents as reliable screening-level hazard assessments. These hazard characterizations are technical documents intended to inform subsequent decisions and actions by OPPT. Accordingly, the documents are not written with the goal of informing the general public. However, they do provide a vehicle for public access to a concise assessment of the raw technical data on HPV chemicals and provide information previously not readily available to the public. 2 ------- U.S. Environmental Protection Agency Hazard Characterization Document September, 2014 Chemical Abstract Service Registry Number 77-79-2 (CASRN) Chemical Abstract Index Name Thiophene, 2,5-dihydro-, 1,1-dioxide Structural Formula o SMILES: 0=S(=0)(CC=C1)C1 Summary 2,5-Dihydrothiophene 1,1-dioxide is a clear, odorous solid possessing high water solubility and moderate vapor pressure. It is expected to have high mobility in soil. It was not readily biodegradable using two standard OECD testing methods, but a structural analog was shown to eventually degrade under typical environmental conditions. Volatilization is expected to be low. The rate of hydrolysis is considered negligible. The rate of atmospheric photooxidation is rapid. 2,5-Dihydrothiophene 1,1-dioxide is not readily biodegradable. 2,5- Dihydrothiophene 1,1-dioxide is expected to have moderate persistence (P2) and low (Bl) bioaccumulation potential. The acute oral toxicity of 2,5-Dihydrothiophene 1,1-dioxide is low in rats. The acute inhalation toxicity of 2,5-Dihydrothiophene 1,1-dioxide in rats was not determined because the concentration of saturation was not reported; however, no mortalities occurred at the saturated concentration. In an oral gavage combined repeated-dose/reproductive/developmental screening test in rats, 2,5-dihydrothiophene 1,1-dioxide showed an increase in male neuropathy at 150 mg/kg-day; the NOAEL for systemic toxicity is 75 mg/kg-day. No treatment-related effects were observed in the functional observational battery (FOB); however, significant increases were noted in total and ambulatory activity in males at 150 mg/kg-day. No treatment-related effects were observed on reproductive parameters; the NOAEL for reproductive toxicity is 150 mg/kg-day; highest dose tested. In the same study, a decrease in mean body weight in dams and mean pup weight was observed at 75 mg/kg-day; the NOAEL for maternal and developmental toxicity is 25 mg/kg-day. 2,5-Dihydrothiophene 1,1-dioxide was not mutagenic in bacteria or mammalian cells in vitro. 2,5-Dihydrothiophene 1,1-dioxide did not induce chromosomal aberrations or sister chromatid exchange in vitro. 2,5-Dihydrothiophene 1,1-dioxide is irritating to the rabbit eye but not rabbit skin. 2,5- Dihydrothiophene 1,1-dioxide did not increase the incidence of tumors in rats and mice. For 2,5-Dihydrothiophene 1,1-dioxide, the 96-h LCso for fish is 940 mg/L, the 48-h ECso for aquatic invertebrates is 800 mg/L and the 96-h ECso aquatic plant growth rate is > 1000 mg/L. No data gaps were identified under the HPV Challenge Program. 3 ------- U.S. Environmental Protection Agency Hazard Characterization Document September, 2014 The sponsor, Chevron Phillips Chemical Company, LP, submitted a Test Plan and Robust Summaries to EPA for 2,5-dihydrothiophene 1,1-dioxide (CASRN 77-79-2; CA Index name: thiophene, 2,5-dihydro-,l,l-dioxide) on April 6, 2004. EPA posted the Submission on the ChemRTK HPV Challenge website on April 19, 2004 (http://www.epa.gov/oppt/chemrtk/pubs/summaries/25disulf/cl5167tc.htm). EPA comments on the original submission were posted to the website on July, 20, 2005. Public comments were also received and posted to the website. The sponsor submitted updated/revised documents on November 14, 2006, which were posted to the ChemRTK website on January 10, 2007. 1. Chemical Identity 1.1 Identification and Purity The robust summary states a purity of 92-99% for particular studies in this hazard characterization, where indicated. The sponsor states in its 2006 Test Plan that 2,5- dihydrothiophene 1,1-dioxide is a clear, solid, odorous organosulfur compound (C4H602S) used as a specialty solvent in petroleum refining and as a chemical intermediate in the production of tetrahydrothiophene 1,1-dioxide (Sulfolane). The National Toxicology Program (NTP) states that Sulfolene is an intermediate in the production of sulfolane, which is used in the petroleum, plastics, and textile industries, and in the synthesis of one or more fungicides or additional chemicals. The substance can also be used as a catalyst. The purity of this substance in the conducting of NTP studies was not specified. 1.2 Physical-Chemical Properties The physical-chemical properties of 2,5-dihydrothiophene 1,1-dioxide are summarized in Table 1. 2,5-Dihydrothiophene 1,1-dioxide is a clear, odorous solid at room temperature. It has high water solubility and moderate vapor pressure. It is used as an industrial solvent and isolated intermediate for the production of 2,5-dihydrothiophene 1,1-dioxide (sulfolane, CASRN 126-33- 0). It is also used as a chemical intermediate in the production of transmission fluids. Table 1. Physical-Chemical Properties of 2,5-Dihydrothiophene 1,1-Dioxide1 Property Value CASRN 77-79-2 Molecular Weight 118.15 Physical State Solid at room temperature Melting Point 63-65.5°C (measured) Boiling Point Decomposes before boiling Vapor Pressure 9.75><10"3 mm Hg at 25°C (measured) Dissociation Constant (pK) Not applicable 4 ------- U.S. Environmental Protection Agency Hazard Characterization Document September, 2014 Table 1. Physical-Chemical Properties of 2,5-Dihydrothiophene 1,1-Dioxide1 Property Value Henry's Law Constant 2.6x 10"8 atm-m3/mole (estimated)2 Water Solubility -59,000 mg/L at 25°C (measured) Log Kow <1 (measured); -0.45 (estimated) 'Chevron Phillips. 2006. Revised Robust Summary and Test Plan for 2,5-dihydrothiophene 1,1-dioxide (Sulfolene). U.S. High Production Volume (HPV) Chemical Challenge Program. Available online at http://www.epa.gov/chemrtk/pubs/summaries/25disulf/cl5167tc.htm as of July 23,2012. 2U.S. EPA. 2012. Estimation Programs Interface Suite™ for Microsoft® Windows, v4.10. U.S. Environmental Protection Agency, Washington, DC, USA. Available online at http://www.epa.gov/opptintr/exposure/pubs/episuitedl.htm as of July 26, 2012. 2. General Information on Exposure 2.1 Production Volume and Use Pattern 2,5-Dihydrothiophene 1,1-dioxide had an aggregated production and/or import volume in the United States between 1 to 10 million pounds during calendar year 2005. Industrial processing and uses for the chemical were claimed confidential. No commercial and consumer uses were reported for the chemical. 2.2 Environmental Exposure and Fate The environmental fate properties are provided in Table 2. 2,5-Dihydrothiophene 1,1-dioxide is expected to have high mobility in soil. 2,5- Dihydrothiophene 1,1-dioxide achieved 0% of its theoretical biochemical oxygen demand (BOD) after 28 days using an activated sludge inoculum and the closed bottle (OECD 301D) test. It was degraded 2% as measured by CO2 evolution after 28 days using the modified Sturm (OECD 301B) test. A structural analog, thiophene, tetrahydro-, 1,1-dioxide, was also not readily biodegradable using the MITI (OECD 301C) test; however, it did biodegrade under aerobic conditions within a few days using aquifer slurries obtained from ground water and sediment from a sour gas plant following a 10-day acclimation period. Data from other microcosm and field studies indicate that, under typical groundwater conditions (aerobic or anaerobic but very low in nutrients, particularly phosphate), 2,5-dihydrothiophene 1,1-dioxide degradation may be very slow or nonexistent. However, under conditions typical of surface water (aerobic, sufficient nutrients), it has been shown that 2,5-dihydrothiophene 1,1-dioxide degradation can be relatively rapid. This suggests that 2,5-dihydrothiophene 1,1-dioxide will have similar biodegradation rates under similar environmental conditions. The rate of volatilization for 2,5-dihydrothiophene 1,1-dioxide is considered low based on the Henry's Law constant for this substance. The rate of hydrolysis is considered negligible. The rate of atmospheric photooxidation is rapid. 2,5- Dihydrothiophene 1,1-dioxide is expected to have moderate persistence (P2) and low (Bl) bioaccumulation potential. 5 ------- U.S. Environmental Protection Agency Hazard Characterization Document September, 2014 Table 2. Environmental Fate Properties of 2,5-Dihydrothiophene 1,1-dioxide1 Property Value CASRN 77-79-2 Photodegradation Half-life 1.4-1.9 hours (estimated)2 Hydrolysis Half-life Stable Biodegradation 2% at 28 days (not readily biodegradable, OECD 301B); 0% at 28 days (not readily biodegradable, OECD 301D) Bioaccumulation Factor BAF = 0.91 (estimated)2 Log Koc 0.9 (estimated)2 Fugacity (Level III Model)2 Air (%) 0.1 Water (%) 38.4 Soil (%) 61.5 Sediment (%) <0.1 Persistence3 P2 (moderate) Bi oaccumul ati on3 Bl (low) 'Chevron Phillips. 2006. Revised Robust Summary and Test Plan for 2,5-dihydrothiophene 1,1-dioxide (Sulfolene). U.S. High Production Volume (HPV) Chemical Challenge Program. Available online at http://www.epa.gov/chemrtk/pubs/summaries/25disulf/cl5167tc.htm as of July 23,2012. 2U.S. EPA. 2012. Estimation Programs Interface Suite™ for Microsoft® Windows, v4.10. U.S. Environmental Protection Agency, Washington, DC, USA. Available online at http://www.epa.gov/opptintr/exposure/pubs/episuitedl.htm as of July 26, 2012. 3Federal Register. 1999. Category for Persistent, Bioaccumulative, and Toxic New Chemical Substances. Federal Register 64, Number 213 (November 4, 1999) pp. 60194-60204. Conclusions: 2,5-Dihydrothiophene 1,1-dioxide is a clear, odorous solid possessing high water solubility and moderate vapor pressure. It is expected to have high mobility in soil. It was not readily biodegradable using two standard OECD testing methods, but a structural analog was shown to eventually degrade under typical environmental conditions. Volatilization is expected to be low. The rate of hydrolysis is considered negligible. The rate of atmospheric photooxidation is rapid. 2,5-Dihydrothiophene 1,1-dioxide is expected to have moderate persistence (P2) and low (Bl) bioaccumulation potential. 3. Human Health Hazard A summary of the human health toxicity data submitted for SIDS endpoint is provided in Table 3. Acute Oral Toxicity Sprague-Dawley rats (five/sex/dose) were administered 2,5-dihydrothiophene 1,1-dioxide (purity not specified) via gavage at 1000, 2000, 2500 (females only), 3000, 4000 or 5000 mg/kg and observed for up to 14 days following dosing. Mortality was observed at > 2500 mg/kg in 6 ------- U.S. Environmental Protection Agency Hazard Characterization Document September, 2014 females and at > 3000 mg/kg in males. Specific mortalities were identified at 2500 (3F), 3000 (2M, 5F), 4000 (5M, 4F) and 5000 (all animals died for both sexes). LDso = 2876 mg/kg (combined) Acute Inhalation Toxicity Wistar rats (10/sex/control, 5/sex/treatment) were administered a saturated concentration of 2,5- dihydrothiophene 1,1 -dioxide 99% pure mixed with isopropyl alcohol via vapor inhalation for 4 hours and observed for 14 days. The saturation concentration was not quantified. No mortalities occurred during the study. Additional information was included from OTS0533768. LD50 > Saturated concentration of 2,5-dihydrothiophene 1,1-dioxide in air at 25°C Repeated-Dose Toxicity In a modified combined repeated-dose/reproductive/developmental toxicity screening test, CrL:CD(SD) rats (12/sex/dose, 18/sex in the control and high-dose groups) were administered 2,5-dihydrothiophene 1,1-dioxide (98.9% pure) via gavage in corn oil at 10, 25 or 75 mg/kg-day for females and 25, 75 or 150 mg/kg-day for males. Control animals received corn oil only. Males were dosed for 28 days (premating through 1 day prior to scheduled sacrifice) and females were dosed for 40 to 44 days (14 days premating through lactation day 3). Females with no evidence of mating were dosed through the day prior to sacrifice for a total of 52 doses. At the end of the study, 6/sex in the control and high-dose groups remained on study for 14 days of recovery. Mortality was observed in 1/12 dams at 75 mg/kg-day during lactation day 4. Mid- and high-dose males and high-dose females exhibited statistically significant (p < 0.01) decreased mean body-weight gains and decreased food consumption during study days 0 - 7. A statistically significantly (p < 0.01) decrease in mean body weight gains and food consumption was observed in high-dose males during the remainder of the premating and treatment periods and in high-dose females during the entire pre-mating period. No treatment-related effects were observed on functional observational battery (FOB); however, total and ambulatory activity was statistically significant (p=0.007) in males at 150 mg/kg-day. Increases in motor activity were noted in females at 75 mg/kg-day. Treatment-related effects were observed in the hematology and urinalysis endpoints, but were considered not toxicologically significant because these values either had slight difference in or were within normal control values. The total volumes of urine for recovery phase males in the high-dose group were increased by more than 2-fold compared to the control group, but the increase was not statistically significant. Statistically significant (p < 0.01) increases in relative liver and kidney weights were observed in high-dose males. Histopathology revealed increased incidences of centrilobular hepatocellular hypertrophy and eosinophilic kidney tubules in high-dose males and increased incidences of hyaline droplets in kidney proximal tubular epithelial cells of mid- and high-dose males. Brain and heart weights were statistically significantly (p < 0.05) increased among certain test groups, but these differences were considered to be a result of the 2,5-dihydrothiophene 1,1-dioxide-related effects on final body weight. No consistent treatment-related effects were found for the functional observational battery (FOB), locomotor activity patterns, hematology, serum chemistry or findings at necropsy. No additional treatment-related effects were found on organ weights 7 ------- U.S. Environmental Protection Agency Hazard Characterization Document September, 2014 (adrenal glands, brain, epididymides, heart, ovaries and oviducts, spleen, testes, thymus gland and thyroids with parathyroid) or histology (comprehensive set of tissues evaluated for the reproduction phase in the control, high-dose males and females and from females that died or failed to deliver and liver and kidneys from low-dose, mid-dose and recovery-phase males). LOAEL (systemic toxicity) = 150 mg/kg-day (based on male nephropathy)5 NOAEL (systemic toxicity) = 75 mg/kg-day Reproductive Toxicity In a combined repeated-dose/reproductive/developmental toxicity screening test in CrL:CD(SD) rats previously mentioned, no treatment-related effects were evident for reproductive performance, gestation and lactation, food consumption, pup sex ratios, pup survival, pup external examinations, gestation length or litter size to postnatal day (PND) 4. No treatment- related effects on mating or fertility were observed in males or females at any dosage level. Mating indices were 100.0%, 100.0%, 100.0%) and 91.7% each in the control, 25, 75 and 150 mg/kg-day groups (males) and control, 10, 25 and 75 mg/kg-day groups (females), respectively. Fertility indices were 91.7%, 100.0%), 100.0%) and 91.7%, and male copulation and female copulation indices were 91.7%, 100.0%), 100.0%) and 100.0%) in the same respective groups. The mean numbers of days between pairing and coitus in the test article-treated groups were similar to the control group value. None of these differences were statistically significant and none were attributed to the test article. LOAEL (maternal toxicity) = 75 mg/kg-day (based on decreased mean body weight in dams on lactation days 1 and 4) NOAEL (maternal toxicity) = 25 mg/kg-day NOAEL (reproductive toxicity) = 150 mg/kg-day (highest dose tested) Developmental Toxicity In a combined oral gavage repeated-dose/reproductive/developmental toxicity screening test, CrL:CD(SD) rats previously mentioned(12/sex/dose, 18/sex in the control and high-dose groups) were administered 2,5-dihydrothiophene 1,1-dioxide via gavage in corn oil at 10, 25 or 75 mg/kg-day for females and 25, 75 or 150 mg/kg-day for males. Control animals received corn oil. Males were dosed for 28 days (14 days premating through 1 day prior to scheduled euthanasia) and females were dosed for 40 - 44 days (14 days premating through lactation day 3). Females with no evidence of mating were dosed through the day prior to euthanasia for a total of 52 doses. At the end of the study, six animals/sex in the control and high-dose groups remained on study for 14 days without treatment. On PND 1 and 4, mean body weights of dams 5 The presence of nephropathy in association with the hyaline droplet accumulation in male rats suggests that the nephropathy in the males is occurring by an alpha2U-globulin-mediated mechanism, which appears to be unique to male rats and the response is probably not relevant to humans for purposes of risk assessment. EPA's Risk Assessment Forum has outlined the key events and the data that are necessary to demonstrate this mode of action (Alpha2U-Globulin: Association with Chemically Induced Renal Toxicity and Neoplasia in the Rat, EPA/625/3-91/019F). Although the protocol for this study on sulfolene indicated that immunohisto-chemical staining was to be used to evaluate alpha2U-globulin in kidney tissue sections from control and high-dose males, the result section did not describe the findings from such a study. Therefore, one of the key events, alpha 2u-globulin accumulation, has not been demonstrated and the nephropathy is assumed to be relevant to human health. 8 ------- U.S. Environmental Protection Agency Hazard Characterization Document September, 2014 were 8.6 and 6.9% respectively at 75 mg/kg-day. A decrease in mean male (11%) and female (10.4%) pup body weights was observed at 75 mg/kg-day. At the same dose, mean pup body- weights on PND 4 remained lower than values in historical controls. No additional treatment- related effects were found for organ weights (adrenal glands, brain, epididymides, heart, ovaries and oviducts, spleen, testes, thymus gland and thyroids with parathyroid) or histology (comprehensive set of tissues evaluated for the reproduction phase in the control, high-dose males and females and from females that died or failed to deliver and liver and kidneys from low-dose, mid-dose and recovery-phase males). LOAEL (maternal and developmental toxicity) = 75 mg/kg-day (based on decreased mean body weight in dams on lactation days 1 and 4 and decrease mean male and female pup weights on PND 1 and 4) NOAEL (maternal and developmental toxicity) = 25 mg/kg-day Genetic Toxicity — Gene Mutation In vitro (1) Mouse lymphoma L5178Y TK+/- cells were exposed to 2,5-dihydrothiophene 1,1-dioxide (purity not specified) at concentrations of 0, 61, 90, 135, 202, 301, 449, 670 or 1000 |j,g/mL in the presence and absence of metabolic activation. Positive controls were used and produced appropriate responses. Based on percent survival, the highest test concentration was not cytotoxic. 2,5-Dihydrothiophene 1,1-dioxide was not mutagenic in this assay. (2) In an NTP study, Mouse lymphoma cells were exposed to 2,5-dihydrothiophene 1,1-dioxide (purity not specified) at concentrations of 0, 312.5, 625, 1250, 2500 and 5000 |j,g/mL or 0, 1000, 2000, 3000, 4000, or 5000 |j,g/mL in the absence of metabolic activation or at concentrations of 0, 1000, 2000, 3000, 4000 or 5000 |j,g/mL in two trials in the presence of metabolic activation. Positive controls were used and produced appropriate responses. There was no indication of cytotoxicity in the absence or presence of metabolic activity. Trial two in the absence of metabolic activity was inconclusive. Study ID # 964398 2,5-Dihydrothiophene 1,1-dioxide was not mutagenic in this assay. (3) Salmonella typhimurium strains TA98, TA100, TA1535, TA1537 and TA1538 were exposed to 2,5-dihydrothiophene 1,1-dioxide (purity not specified) at concentrations of 0, 123.5, 370.4, 1111.1, 3333.3 or 10,000 |j,g/plate in the presence and absence of metabolic activation. Positive controls were used and produced appropriate responses. The cytotoxic concentration was not provided. 2,5-Dihydrothiophene 1,1-dioxide was not mutagenic in this assay. (4) In an NTP study, Salmonella typhimurium strains TA98, TA100, TA1535 and TA1537 were exposed to 2,5-dihydrothiophene 1,1-dioxide (purity not specified) at concentrations of 0, 100, 3333, 1000, 3333 or 10,000 |j,g/plate in the presence and absence of metabolic activation. Positive controls were used and produced appropriate responses. The cytotoxic concentration was not provided. Study ID #430543 2,5-Dihydrothiophene 1,1-dioxide was not mutagenic in this assay. 9 ------- U.S. Environmental Protection Agency Hazard Characterization Document September, 2014 Genetic Toxicity - Chromosomal Aberrations In vitro (1) In a Sister Chromatid Exchange (SCE) study, Chinese Hamster Ovary (CHO) cells, CCL 61 were exposed to 2,5-dihydrothiophene 1,1-dioxide (purity not specified) at concentrations of 0, 10, 34, 100, 334 or 1000 |j,g/mL in the presence and absence of metabolic activation. Positive controls were used and produced appropriate responses. No increase in the number of SCEs per chromosome was seen at any dose level in the presence or absence of metabolic activation. The cytotoxic concentration was not provided. 2,5-Dihydrothiophene 1,1-dioxide did not induce SCE in this assay. (2) In two NTP studies, CHO cells were exposed to 2,5-dihydrothiophene 1,1-dioxide (purity not specified) at concentrations of 0, 368, 1110 or 3680 |j,g/mL (Study 067203) and at 0, 1600, or 3000 |ig/mL (Study #080941) in the presence and absence of metabolic activation. Positive controls were used and produced appropriate responses. The cytotoxic concentration was not provided. 2,5-Dihydrothiophene 1,1-dioxide did not induce chromosomal aberrations in these assays. (3) In two studies conducted by NTP for the induction of sister chromatid exchange (SCE), mammalian (CHO) cells were exposed to 2,5-Dihydrothiophene 1,1-dioxide (purity not specified) at 0, 379, 1140 or 3790 |ig/mL (Study #067203) and concentrations of 0, 160, 500, or 1600, or 5000 |ig/mL (Study #080941) in the presence and absence of metabolic activation. Positive controls were used and produced appropriate responses. The cytotoxic concentration was not provided. 2,5-Dihydrothiophene 1,1-dioxide did not induce SCE in these assays. Additional Information Eye Irritation (1) New Zealand White/Dutchland rabbits (6, sex not specified) were administered 2,5- Dihydrothiophene 1,1-dioxide (0.1 mL, purity not specified) in a "normal saline slurry" into the left eye of each rabbit. Treated eyes were held closed for 1 second and not washed. Ocular reactions were evaluated at 1, 24, 48 and 72 hours and at 4 and 7 days after treatment. Corneal opacity, iritis, conjunctival redness, conjunctival chemosis, phonation, ocular irritation and conjunctival discharge were observed. Total scores were 16.8, 35.7, 36.3, 29.2, 25.5, and 11.8 at 1, 24, 48, 72 hours, 4 and 7 days. 2,5-Dihydrothiophene 1,1-dioxide was irritating to rabbit eyes in this study. (2) New Zealand White/Dutchland rabbits (6, sex not specified) were administered 2,5- Dihydrothiophene 1,1-dioxide (0.1 mL, purity not specified) in a "normal saline slurry" into the left eye of each rabbit. Treated eyes were held closed for 1 second and washed with 40 mL of tap water. Ocular reactions were evaluated at 1, 24, 48 and 72 hours and at 4 and 7 days after treatment. Corneal opacity, iritis, conjunctival redness, conjunctival chemosis, phonation, ocular 10 ------- U.S. Environmental Protection Agency Hazard Characterization Document September, 2014 irritation and conjunctival discharge were observed. Total scores were 34.2, 13.5, 15.0, 8.8, 7.5 and 4.3 at 1, 24, 48, 72 hours and 4 and 7 days. 2,5-Dihydrothiophene 1,1-dioxide was irritating to rabbit eyes in this study. Skin Irritation New Zealand White/Dutchland rabbits (3/sex) were treated with undiluted 2,5-dihydrothiophene 1,1-dioxide (0.5 g, purity not specified) to clipped, abraded and unabraded skin under occluded conditions for 24, then wiped clean. Animals were evaluated at 24 and 72 hours after exposure. No erythema or edema was observed. 2,5-Dihydrothiophene 1,1-dioxide was not irritating to rabbit skin in this study. Carcinogenicity (1) In an NTP study, Osborne-Mendel rats (20/sex/controls; 50/sex/dose) were exposed to 2,5- dihydrothiophene 1,1-dioxide via gavage at 0 (corn oil), 197 or 372 mg/kg-bw/day in males and 0 (corn oil), 120 or 240 mg/kg-bw/day in females 5 days/week for 78 weeks. A significant (p < 0.002) positive association between dosage and mortality was found in treated males and females compared to the vehicle controls. The last high-dose male died at week 60. Incidences of neoplasms in treated animals were within or below spontaneous incidences observed in this rat strain. 2,5-Dihydrothiophene 1,1-dioxide did not shown to induce tumors in this study. (2) In a NTP study, B6C3F1 mice (20/sex/controls; 50/sex/dose) were exposed to 2,5- dihydrothiophene 1,1-dioxide via gavage at 0 (corn oil), 311 or 622 mg/kg-bw/day in males and 0 (corn oil), 384 or 768 mg/kg-bw/day in females 5 days/week for 78 weeks. A significant (p < 0.001) positive association between dosage and mortality was found in treated males and females when compared to control. Although the Cochran-Armitage statistical test indicated that a significant (p = 0.040) positive association between dose and incidence of hepatocellular carcinomas, the Fisher exact test was not significant. Therefore, there was no evidence for carcinogenicity. 2,5-Dihydrothiophene 1,1-dioxide did not induce the incidence of tumors in this study. Conclusion: The acute oral toxicity of 2,5-Dihydrothiophene 1,1-dioxide is low in rats. The acute inhalation toxicity of 2,5-Dihydrothiophene 1,1-dioxide in rats was not determined because the concentration of saturation was not reported; however, no mortalities occurred at the saturated concentration. In an oral gavage combined repeated-dose/reproductive/developmental screening test in rats, 2,5-dihydrothiophene 1,1-dioxide showed an increase in male neuropathy at 150 mg/kg-day; the NOAEL for systemic toxicity is 75 mg/kg-day. No treatment-related effects were observed in the functional observational battery (FOB); however, significant increases were noted in total and ambulatory activity in males at 150 mg/kg-day. No treatment- related effects were observed on reproductive parameters; the NOAEL for reproductive toxicity is 150 mg/kg-day; highest dose tested. In the same study, a decrease in mean body weight in dams and mean pup weight was observed at 75 mg/kg-day; the NOAEL for maternal and 11 ------- U.S. Environmental Protection Agency Hazard Characterization Document September, 2014 developmental toxicity is 25 mg/kg-day. 2,5-Dihydrothiophene 1,1-dioxide was not mutagenic in bacteria or mammalian cells in vitro. 2,5-Dihydrothiophene 1,1-dioxide did not induce chromosomal aberrations or sister chromatid exchange in vitro. 2,5-Dihydrothiophene 1,1- dioxide is irritating to the rabbit eye but not rabbit skin. 2,5-Dihydrothiophene 1,1-dioxide did not increase the incidence of tumors in rats and mice. Table 3. Summary Table of the Screening Information Data Set as Submitted under the U.S. HPV Challenge Program - Human Health Data Endpoint 2,5-Dihydrothiophene 1,1 -Dioxide (77-79-2) Acute Oral Toxicity LDso (mg/kg) 2876 Acute Inhalation Toxicity LC50 (mg/L) >Saturated concentration in air at 25°C (not quantified) Repeated-Dose Toxicity NOAEL/LOAEL Oral (mg/kg-day) (rat) LOAEL = 150 NOAEL = 75 Reproductive Toxicity NOAEL/LOAEL Oral (mg/kg-day) Reproductive Toxicity NOAEL = 150 (highest dose tested) Developmental Toxicity NOAEL/LOAEL Oral (mg/kg-day) Maternal Toxicity Developmental Toxicity (rat) LOAEL = 75 NOAEL = 25 LOAEL = 75 NOAEL = 25 Genetic Toxicity - Gene Mutation In vitro Negative Genetic Toxicity - Chromosomal Aberrations In vitro Negative Genetic Toxicity - Other SCE Negative Additional Information Carcinogenicity Eye Irritation Skin Irritation Negative (rats and mice) Irritating Not Irritating 12 ------- U.S. Environmental Protection Agency Hazard Characterization Document September, 2014 4. Hazard to the Environment A summary of aquatic toxicity data submitted for SIDS endpoints is provided in Table 4. Acute Toxicity to Fish Rainbow trout (Oncorhynchus myki.s.s, 10/concentration) were exposed to 2,5-dihydrothiophene 1,1-dioxide at nominal concentrations of 0, 100, 200, 500 or 1000 mg/L under static renewal conditions for 96 hours. Measured concentrations were not provided. At 96 hours, 60 % mortality was observed at the highest concentration and 0 % mortality was observed at all other concentrations. 96-h LCso = 940 mg/L Acute Toxicity to Aquatic Invertebrates Water fleas (Daphnia magna, 10/replicate, three replicates/concentration) were exposed to 2,5- dihydrothiophene 1,1-dioxide at nominal concentrations of 50, 100, 200, 500 or 1000 mg/L under static conditions for 48 hours. Measured concentrations were not provided. Immobilization was observed at 1000 mg/L at 24 hours and at 500 and 1000 mg/L at 48 hours. 48-h ECso = 800 mg/L Toxicity to Aquatic Plants Green algae (Pseudokirchneriella subcapitata) were exposed to 2,5-dihydrothiophene 1,1- dioxide at nominal concentrations of 10, 20, 50, 100, 200, 500 or 1000 mg/L for 96 hours. Measured concentrations were not provided. Cell concentrations at 96 hours were 0.76, 0.60, 0.61, 0.46, 0.72, 0.76 and 0.73 x 106 for the 10, 20, 50, 100, 200, 500 and 1000 mg/L groups, respectively. 96-h ECso (growth rate) > 1000 mg/L Conclusion: For 2,5-Dihydrothiophene 1,1-dioxide, the 96-h LC50 for fish is 940 mg/L, the 48-h EC50 for aquatic invertebrates is 800 mg/L and the 96-h EC50 value for aquatic plant growth rate is > 1000 mg/L. 13 ------- U.S. Environmental Protection Agency Hazard Characterization Document September, 2014 Table 4. Summary Table of the Screening Information Data Set as Submitted under the U.S. HPV Challenge Program - Aquatic Toxicity Data Endpoint 2,5-Dihydrothiophene 1,1-Dioxide (77-79-2) Fish 96-h LCso (mg/L) 940 Aquatic Invertebrates 48-h ECso (mg/L) 800 Aquatic Plants 72-h ECso (mg/L; growth rate) > 1000 Bold = experimental data (i.e. derived from testing) 14 ------- |