The Nickel Institute has said it is "somewhat surprised" by an announcement that regulators in California will meet in October to discuss the possible developmental and reproductive toxicity (DART) of nickel and its compounds. Up for discussion is the possibility of a DART Proposition 65 listing, which would have regulatory implications for companies using the substances.
The hazards of nickel use have been evaluated many times by authoritative bodies around of the world. Nickel is produced in high volumes, is widely used and has known adverse effects on human health and the environment. But historically regulators have tended to focus on other endpoints, particularly skin sensitisation and carcinogenicity.
For example, nickel and several nickel compounds are already listed under Proposition 65 for carcinogenicity; just one compound, nickel carbonyl, is also listed for DART.
The Office of Environmental Health Hazard Assessment (Oehha) raised the possibility of a DART listing for nickel in 2015. But the Developmental and Reproductive Toxicant Identification Committee (Dartic) subsequently set a prioritisation level of "medium/low" for the metal and its compounds.
"We are somewhat surprised that this has been brought forward now," a Nickel Institute spokesperson told Chemical Watch.
Oehha has published a hazard identification document and Dartic will consider whether to list the substances for DART at a public meeting on 11 October.
The 342-page document describes a range of relevant human studies, including:
- five cohort studies of humans exposed to nickel particles in ambient air, all of which reported "small but statistically significant" associations adverse effects on fetal growth parameters;
- an epidemiological study of female human reproductive effects of nickel exposure that reported an association with levels of sex-hormone binding globulin (SHBG); and
- an epidemiological study of male reproductive effects that reported an association between inhaled nickel and levels of nickel in urine, with urinary nick was in turn associated with lower plasma testosterone.
It also describes a range of animal studies, mainly involving rats and mice, that reported associations between exposure to nickel or nickel compounds and various DART endpoints.
Nickel and its compounds are used in: stainless steel and other nickel alloys; catalysts; batteries; pigments; and ceramics. Nickel is particularly valued in applications for its resistance to corrosion, extreme temperature and mechanical stress. Nickel salts meanwhile, are widely used in electroplating baths, batteries, textile dyes, and catalysts.
Water soluble nickel compounds have mandatory reprotoxicity 1B classifications under EU CLP, but there is no equivalent classification for nickel metal and insoluble nickel compounds.
The Nickel Institute spokesperson said this is because, based on toxicokinetic studies, they are expected to have much lower bioavailability. "IE, it is more difficult for these forms of nickel to be absorbed into the body either by inhalation, oral ingestion or through the skin."
They added that "relevant exposure to nickel and nickel compounds is limited to the workplace. Any potential risks to workers are controlled by workplace safety and health regulations. Importantly, epidemiology studies do not support a causal association between exposure to nickel, soluble and insoluble forms, and adverse reproductive outcomes."
The organisation is planning to review the document and contribute to the Dartic process.
Oehha has launched a 45-day public consultation on the hazard identification document and interested parties have until 11 September to submit comments.