DDT sprayed in New Brunswick forests persists in trout at ‘alarming’ levels: study

The insecticide was used to control spruce budworm, which mainly feeds on balsam fir and white spruce, and is a natural pest found in the province's forests.

More than 50 years after it was last used in New Brunswick, new research shows the insecticide DDT is still found in “alarming” rates in trout in the province’s lakes, potentially posing a danger to other wildlife and humans that eat the fish.

Josh Kurek, associate professor in Mount Allison University’s department of geography and environment, said in an interview Tuesday that DDT was sprayed over more than half of the province’s forests between 1952 and 1968.

“New Brunswick ran arguably one of the largest aerial spray programs of DDT ever undertaken on planet Earth,” said Kurek, lead author of a study published in the journal PLOS One this week

The insecticide was used to control spruce budworm, which mainly feeds on balsam fir and white spruce, and is a natural pest found in the province’s forests.

For the study, researchers analyzed fish, invertebrates and sediment in seven lakes alongside publicly available data on how much DDT had been sprayed.

“What our study showed is there’s incredibly high amounts of DDT in the sediments of our lakes, but also in brook trout,” Kurek said. “These are brook trout that are just a few years old, and they’re exposed to this legacy DDT mostly through their diet.”

Brook trout mainly feed on small aquatic insects although their diet consists of a variety of prey, he said. The insects live in the mud at the bottom of lakes, rivers and wetlands, which have large amounts of DDT in the sand, he said.

“We showed that brook trout in five study lakes in this part of the world are about 10 times above levels that the Canadian Council of Ministers of the Environment considers as sort of safe levels for DDT for wildlife,” he said.