Dimethyl sulfoxide (DMSO) [MAK Value Documentation, 2009]

The German Commission for the Investigation of Health Hazards of Chemical Compounds in the Work Area has re‐evaluated the maximum concentration at the work place (MAK value) of dimethyl sulfoxide (DMSO) [67‐68‐5] of 50 ml/m3, considering the endpoints local and systemic toxicity as well as developmental toxicity. In a 13‐week inhalation study the olfactory and respiratory epithelia and the pharynx of rats are the target tissues, and a reduction of body weight gain, possibly secondary to the irritation, is seen. The NOAEC for these effects is 964 mg/m3 (297 ml/m3, vapour). As local effects are critical, the assignment to Peak Limitation Category I and the excursion factor of 2 are confirmed. In a developmental toxicity study with rats a borderline increase in incidences of pups with dilated renal pelvis were seen at the low dose of 200 mg/kg body weight and day. The developmental toxicity study in rabbits revealed an increase in the incidence of malformations of the kidneys after oral administration of 1000 mg/kg body weight and day; this may have been an effect of the treatment. Therefore, a substance‐specific effect on the urinary tract cannot be ruled out. Because a NOAEL for developmental toxicity for rats cannot be established, damage to the embryo or foetus cannot be judged and dimethyl sulfoxide is assigned to Pregnancy Risk Group D. DMSO is not genotoxic in vitro and in vivo. Long‐term carcinogenicity studies are not available, short‐term studies do not indicate a potential for carcinogenicity. DMSO is not a skin sensitizer, data on respiratory sensitization are not available. Skin contact is expected to contribute significantly to the systemic toxicity of DMSO therefore, it is still designated with an “H