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EC number: 200-898-6 | CAS number: 75-75-2
Endpoint summary
Administrative data
Link to relevant study record(s)
Description of key information
Key value for chemical safety assessment
Additional information
Assessment of Toxicokinetic Behaviour
In the only study available in rats, complete urinary excretion was observed within 24 hours after a single intraperitoneal application of 35S-labelled methanesulfonic acid (MSA) of 50 mg/kg bw to rats. Metabolites were not identified in this study (Jones and Edwards, 1973).
In order to obtain more information on Adsorption/Distribution/Metabolism/Excretion of MSA, an assessment of Toxicokinetic Behaviour was performed using the Physical Chemical properties of MSA.
Physical and Chemical properties of the substance
MSA (molecular weight of 96.1 g/mol) is available in commercial quantities as a 70% solution in water and in anhydrous form. It is highly soluble in water, 1000 g/L at 20 °C (US-EPA, 2003). The low log Kow value of - 2.38 (see IUCLID Chapter 4.7 partition coefficient) suggests that MSA has a low bioaccumulative potential. MSA has a very low vapor pressure (0.000756 hPa at 25 °C) (see IUCLID Chapter 4.6, Vapour Pressure), therefore a very low level of inhalative exposure is expected. MSA has very low pH (< 2), therefore is corrosive in nature.
Adsorption/Distribution/Metabolism/Excretion (ADME)
Absorption:
In an acute oral study, groups of five rats/sex were exposed by oral gavage to 300, 500 and 750 mg/kg bw anhydrous (99.6% pure) MSA (US-EPA, 2003). Clinical signs and gross pathology findings observed were considered as secondary due to the corrosive properties of MSA, no systemic effects were observed and no specific target organ was detected. Similar effects were observed in other acute oral studies, however with low intensity when tested with 70 % MSA in water.
In an OECD 421 study, groups of 12 rats/sex were exposed to MSA (70.5% in water) by oral gavage at doses of 250, 500 and 1000 mg/kg bw/d for 42 days (28 days pre-mating and 14 days mating period) in males and at least 54 days (28 days pre-mating, 1-14 days mating period, 21-22 days pregnancy and 4 days lactation) in females (US-EPA, 2003). There were no substance-induced effects on the male and female reproductive performance, or on the progeny of the parental rats indicating no systemic effects up to the highest dose tested. Therefore, there is no indication for a systemic availability after oral uptake.
No mortalities were observed in mice exposed once for 1h to the saturated vapor concentration of 0.05 mg/L (US-HPA, 2003). Thus, absorption of the substance via the inhalation (vapor) route is not assumed. Additionally, in an OECD Guideline 412 (Repeated Dose Inhalation Toxicity: 28/14-Day) study, only local effects were observed in male and female rats exposed to MSA aerosol at concentrations of 0.026, 0.073 or 0.242 mg/l for 6 hours/day, 5 days/week for 4 weeks followed by 2-week recovery period (US-HPV, 2003). A transient reduced body weight gain and slightly reduced food consumption were observed in 0.242 mg/l exposure level males, but these effects were considered as secondary due to strong local effects on the upper respiratory tract. The result indicates irritating potential of MSA to the respiratory system with no signs of adverse systemic toxicity.
Due to corrosive nature of MSA, irritating effects on the skin are foreseen. In an OECD 402 test with 24 h exposure at dose level of 1000 mg/kg bw (70 % MSA in water), again only local effects were observed. Additionally, the log kow of < -1 suggest that MSA is not likely to be sufficiently lipophilic to cross the stratum corneum (ECHA R7c, 2008). Therefore, a dermal uptake is not assumed.
Metabolism/ Excretion
As discussed above, no systemic effects were observed after oral or inhalation administration in subacute studies in rats. Additionally, no potential metabolites were detected after liver and skin metabolism and after hydrolysis by OECD toolbox 1.1.01. The only metabolites detected were after microbial metabolism (formaldehyde and formic acid); however these are irrelevant for mammalian metabolism.
Complete urinary excretion was observed within 24 hours after a single intraperitoneal application of 35S-labelled MSA of 50 mg/kg bw to rats, however metabolites were not identified in the only available in-vivo study. This indicates that MSA is expected to be completely excreted predominantly via the urine without forming any metabolites.
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