Posted on 13/03/2019 in 2019
Regulatory pressure tightens on antimony (ATO)

Tighter regulations and questions about carcinogenicity may impact use of antimony trioxide (ATO, Sb2O3) as a synergist for brominated flame retardants. Germany has put into place a very low workplace exposure limit of 0.006 mg/m3 respirable antimony since May 2018 (BAuA) and Japan implemented 0.1 mg/m3 inhalable antimony in 2017 (‘respirable’ concerns smaller particles, generally <10 µm versus <100 µm for ‘inhalable’). These limits are considerably lower than most limits which are generally currently 0.5 mg inhalable Sb per m3.
The US National Toxicology Program (US Federal Department of Health and Human Services) published end 2017 a report (NTP TR 590) on studies of ATO in rats and mice, and in October 2018 a “Report on Carcinogens. Monograph on Antimony Trioxide”. This report responds to the US legislator requirement to identify substances which are known or reasonably anticipated to be human carcinogens. The report identified 5 500 references and assessed over 500, concluding that ATO can “reasonably anticipated to be a human carcinogen based on sufficient evidence of carcinogenicity from studies in experimental animals and supporting evidence from mechanistic studies”. ATO was indicated to lead to increases in oxidative stress and damage, impairment of DNA damage repair and possibly inhibition of cell differentiation.
In the EU, evaluation of ATO classification for CLP is underway, led by Germany (BAuA, see above). BAuA are reported to have commented that reclassification of ATO as Category 1B carcinogen is possible, based on the US NTP reports. This could lead to consideration for classification as SVHC under REACH.

US National Toxicology Programme, 19 October 2018 “Report on Carcinogens Monograph on Antimony Trioxide”

US National Toxicology Programme, December 2017, report NTP TR 590 “NTP Technical report on the toxicology and carcinogenesis studies of antimony trioxide (CAS no. 1309-64-4) in Wistar HAN [Crl:XI(Han)] rats and B6C3F1/N mice”
“Draft US report recommends adding antimony trioxide to carcinogen list”, Chemical Watch 4 January 2018

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