A National Toxicology Program Peer review panel has agreed to the classification of antimony trioxide as a carcinogen when it accepted the draft assessment that the chemical is reasonably anticipated to be” a human carcinogen.
Widely used as flame retardants, antimony substances are also in paints, lead batteries, plastics, brake pads, glass, ceramics ammunition, and semiconductors. It is also used as catalyst in polyethylene terephthalate (PET) production.
Lung cancer incidence among workers in smelting plants processing antimony-containing ore into antimony metal is reported to be higher compared to that in the general population going back to the 1970s. This observation has caused regulators to worry that antimony trioxide can cause lung cancer.
The draft Report on Carcinogens (RoC) monograph that the six-person panel reviewed on January 24, 2018, was based on NTP’s two-year study on the inhalation carcinogenicity of antimony trioxide. Then, the panel released their actions statement of their unanimous acceptance of NTP’s findings that although data for “studies in human are inadequate” there is “sufficient evidence of carcinogenicity for antimony trioxide from studies in experimental animals.”
The animal study showed increasing occurrences of tumors in rats and mice that inhaled air with antimony trioxide. Higher incidences of white blood cells, skin and lung tumors were observed in mice while rats had higher incidences of adrenal glands and lung tumors.
The panel was also in agreement with the statement that a good number of people living in the United States are exposed to antimony trioxide.”
During the discussion, three comments were addressed to the NTP by researchers on medical toxicology from Drexel University College of Medicine in Philadelphia, Campine, a Belgian producer of antimony products and Caroline Braibant from the International Antimony Association.
According to Braibant, the draft monograph contained factual inaccuracies. She also expressed her significant reservations about:
summary statistics regarding antimony use, consumption and occupational exposure;
- missing data on particle size distribution;
- a probability of errors in the manner of data extraction from the scientific literature;
- conclusions based on NTP’s inhalation bioassays; and
- the validity of the genotoxicity studies performed by the NTP.
- Campine said in its comment that worker health data collected based on Belgian legislation led to its conclusion that:
- · there 1s a weak relationship between exposure and changes in pulmonary function parameters;
- · the relationship between average urinary antimony concentration and abnormalities in lung or liver function was not clear, and
- · no pulmonary lesions were seen in 20 years of chest X-rays.
The company appealed that the panel to postpone its review in order to include the worker health data it has collected.
The chemical industry is worried that the result of the panel’s review of NTP’s study could lead to stricter rules and requirements after Germany’s REACH and BAuA, the CLP competent authority begins their evaluation in March of antimony trioxide, antimony metal,