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Canadian regulators have added the ketone 2,4-pentanedione (2,4-PD) to the country’s Watch List, making it the first chemical placed on the nation’s inventory of substances of potential concern.
The addition of 2,4-PD to the Watch List on 16 July comes less than three months after the government finalised its approach for identifying substances of potential concern. While the listing does not impose any regulatory requirements for 2,4-PD – a substance the government concluded was not a concern in a final assessment in May – the action does signal that the compound could be scrutinised for potential follow-up activity at a later time.
The Watch List was created as part of the 2023 overhaul of the Canadian Environmental Protection Act (CEPA) to provide greater transparency around substances that may have properties of concern and to encourage businesses and the public to select safer alternatives.
Many NGOs welcomed the creation of the Watch List, with groups like Environmental Defence and Ecojustice saying it would bring much-needed transparency around chemicals management and help prevent the "regrettable substitution" of one hazardous chemical with another.
Several industry experts, however, believe the list could ultimately confuse the public about the safety of substances.
Nick Addesso, environment and health policy analyst for the Chemistry Industry Association of Canada (CIAC), said the list "moves away from the risk-based approach that has been a cornerstone [of CEPA] and has the potential to create confusion about substances that have already been determined not to pose a risk under their intended conditions of use".
"CIAC has consistently expressed concerns about the creation of the CEPA Watch List since it was first proposed," Addesso told Chemical Watch News & Insight.
While CIAC supports providing Canadians with clear information about chemicals, he said, "we believe regulatory decisions should continue to be grounded in robust scientific risk assessments".
Substance cleared in May
Canada completed its assessment of 2,4-PD and nine other ketones in May, finding that two of the substances – MEK and MIBK – meet the toxicity criteria under CEPA section 64. The government signalled plans to develop regulatory controls to reduce inhalation exposures to MEK and MIBK.
The other eight substances in the group, including 2,4-PD, were found not to pose harm to the environment or to pose a risk to human health under current exposure conditions.
That final assessment reversed an earlier finding from a 2019 preliminary review that identified 2,4-PD as a potential concern to human health due to its potential to cause systemic toxicity and developmental effects.
In the final assessment, the government said it no longer considered 2,4-PD to be a concern because it is "not currently present in products available to consumers".
But those concerns could change if exposure levels were to increase, the government said in its assessment, prompting it to propose adding 2,4-PD to the Watch List of substances capable of becoming toxic.
The compound was formally added to the Watch List on 16 July, one day after the 60-day comment period ended.
Additional substances could be added to the Watch List in the coming weeks, after Canada proposed putting four more substances on the list late last month.
Current system works
Attorney Scott Thurlow, whose practice focuses on CEPA issues, said the government’s finding that 2,4-PD is no longer used in consumer products in Canada suggests that CEPA’s traditional risk-based approach works just fine.
Industry "self-selected to not use this substance", he said.
The final assessment’s reversal of the preliminary CEPA-toxic designation "demonstrates that Canada’s science- and risk-based chemicals management system works as intended", he said.
"Where a scientific assessment concludes that a substance is not toxic under CEPA and does not require risk management, we believe that finding should provide clarity and certainty for regulators, industry and the public," Thurlow said.
"Introducing additional lists that suggest concern despite that conclusion risks creating unnecessary confusion without delivering meaningful health or environmental benefits," he said.