Canada Clears Metal Industry Waste Products in UVCB Screening

The Canadian government has provisionally concluded that 57 substances, including waste substances from the metals industry, are not harmful to consumers or the environment due to low exposure.

The substances are used in metal smelting and refining, as well as the manufacture of automotive parts, iron and steel, pulp and paper, and cement. They contain a wide range of metals.

The substance ‘solutions, precious metal hydrometallurgical’, for example, may contain metal ions of palladium, platinum, gold, silver and small amounts of rhodium, ruthenium, iridium and other non-ferrous elements, such as copper, nickel, cobalt, lead, Bismuth, antimony, Arsenic, selenium and tellurium.

Each is a ‘substance of unknown or variable composition, complex reaction products and biological materials’ (UVCB). Such substances cannot be defined in terms of composition but are instead normally identified according to the processes by which they are produced. Consequently the assessment contains a wide range of – in some cases anachronistic – industry terms for material types, including: slags; dust; matte; slimes and sludges; liquors; bullion; dross; sponge; waste solids; wastewater; residues; ash; calcines; and fumes.

The assessment report says that many of the substances are known to be hazardous. Some even have components that are already on Schedule 1 of the Canadian Environmental Protection Act, 1999 (Cepa), such as lead, a powerful neurotoxicant that is particularly harmful to development in children. This means that measures - some federal, some voluntary - are already in place to minimise releases from the relevant sites, limiting consumer and environmental exposure.

Furthermore, according to the report, many of the substances are limited to only a few sectors and are expected to be "site-restricted" or "sector-restricted".

But the draft screening assessment takes an unusual approach in so far as it foregoes any analysis of hazard on the basis that the potential exposures are either ‘negligible’ or ‘not expected’.

This concludes that they do not meet any of the criteria set out in section 64 of Cepa. The government is therefore proposing to take no further action against them.

Exposure

For the exposure assessment, the report defines five substance categories: no longer manufactured or imported; intermediate; waste; byproduct; and substance with other commercial uses in other sectors.

It assumes that exposure is "non-existent" for the ‘no longer manufactured or imported’ category and negligible for the intermediate category. For the wastes category, this may be negligible "when considering measures that exist to limit exposure, especially when sent off-site", it says.

For the byproducts category, exposure may be considered "acceptable". "Permitted uses may depend on meeting certain criteria from provincial regulations," the report adds.

Lastly, the ‘substances with other commercial uses in other sectors’ category "may require further assessment if the exposure potential is unknown".

The report assigns the category label on the basis of information from regulatory surveys, voluntary industry submissions, literature reviews, material safety data sheets and consumer product safety.

Thiols and arenes

In two further draft screening assessments, the Canadian government has proposed to conclude that four thiols and two arenes are also not harmful under Cepa.

Three of the thiols - dimethyl sulfide, benzyl disulfide and grapefruit mercaptan - are used as food flavouring agents. The other - tert-dodecyl mercaptan - is used in the manufacture of food packaging materials and may be present as an impurity in paints and coatings.

Dimethyl sulfide is also used as an odourant in natural gas, while tert-dodecyl mercaptan has additional uses in vinyl coverings and paper products, as well as plastic, rubber and metal materials.

One of the arenes - cumene - is used primarily as a chemical intermediate but also used in consumer products, including adhesives, paints, automotive-related products and lubricants. The other, DMBA, is used as a research chemical in laboratories.

Next steps

The Canadian government has launched 60-day public consultation periods for each of the assessments. Interested parties have until 20 September to submit comments.

The final assessments are expected in July 2018.