Environment Canada has been doing fewer inspections, investigations and prosecutions over the last five years to enforce a law protecting people from toxic chemicals and air pollution.

According to figures provided last month in response to a written question submitted in the House of Commons, the department investigated 43 companies for violations of the Canadian Environmental Protection Act in 2015-16. There were 22 prosecutions and convictions.

In each of the last two fiscal years, however, the department investigated 12 companies. One was prosecuted and convicted.

"It definitely raises a lot of questions and concerns," said NDP MP Laurel Collins, the critic for environment and climate change who posed the question.

"It's wild that there was only one investigation that led to a prosecution in 2018 and 2019," she said. "I think most Canadians would be surprised to hear that. I don't think anyone thinks there is only one company violating."

The Canadian Environmental Protection Act (CEPA) governs how Canada manages toxic chemicals and air pollution.

In February, Collins submitted the order paper question, which is what MPs use when they want a more detailed answer from the government than is usually possible during the daily oral question period in the House of Commons. She was seeking an update to a 2018 report on CEPA enforcement from the federal environment commissioner.

That report called out Environment Canada for disproportionately focusing on dry cleaners and the fluid they use for cleaning — known as perchloroethylene — even though it was not more toxic than other substances investigators were supposed to be monitoring.

Collins says she was disheartened to find that enforcement has fallen "dramatically."

Asked to explain the drop in investigations under the act, a spokesperson for Environment Canada said only that investigations can be complex and take many years to complete.

Environment Minister Jonathan Wilkinson would not comment because enforcement is an arm's-length process that must remain outside the political realm, according to spokeswoman Moira Kelly.