The German Commission for the Investigation of Health Hazards of Chemical Compounds in the Work Area has re‐evaluated sodium pyrithione [3811‐73‐2; 15922‐78‐8] considering all toxicological endpoints. Available publications and unpublished study reports are described in detail.
Sodium pyrithione is neurotoxic in rats and rabbits, but not in monkeys. As there is no sufficient mechanistic explanation for the observed differences between the species, the rat as the most sensitive species is used for the derivation of a maximum concentration at the workplace (MAK value).
The NOAEC in a 90‐day inhalation study with rats is 1.1 mg/m3. In a chronic feeding study with rats, a NAEL of 0.16 mg/kg body weight and day is derived from the LOAEL of 0.5 mg/kg body weight and day. Both the NOAEC and the NAEL correspond to a MAK value of 0.2 mg/m3 for the inhalable fraction.
As a systemic effect is critical, the substance remains classified in Peak Limitation Category II. As the initial half‐life of sodium pyrithione is in the range of up to 2.8 hours, an excursion factor of 2 is assigned.
In developmental toxicity studies, the most critical effects of sodium pyrithione are skeletal anomalies in rats. NOAELs for developmental effects are 2 mg/kg body weight and day after oral treatment of rats as well as 3 and 5 mg/kg body weight and day after dermal application to rats and rabbits, respectively. The differences between the NOAELs for rats and rabbits scaled to an inhalation concentration at the workplace and the MAK value are considered sufficient. Therefore, damage to the embryo or foetus is unlikely when the MAK value is not exceeded and sodium pyrithione is assigned to Pregnancy Risk Group C. Sodium pyrithione is still regarded as a non‐genotoxic and non‐carcinogenic substance. Skin contact may contribute significantly to systemic toxicity and sodium pyrithione remains designated with an “H” notation. Sensitization is not expected based on the limited data available.