Joshua Kurek wasn’t surprised to discover that DDT showed up in the sediments of a number of lakes in his province of New Brunswick but he was concerned at the levels. In fact, “concerning” is exactly the conclusion drawn from the study that Kurek, an aquatic scientist and assistant professor at Mount Allison University, conducted along with a team of researchers.
Between 1952 and 1968, “New Brunswick ran, arguably, the world’s largest insecticide spray program,” he explains. “They used close to six million kilograms of DDT.”
DDT, the familiar acronym for dichloro-diphenyl-trichloroethane, was a widely used insecticide for which the creator won the Nobel Prize in Medicine. New Brunswick used it specifically — and liberally — to kill the spruce budworm.
It was banned by both Canada and the United States in 1972, a decade after Rachel Carson sounded the alarm in her seminal book Silent Spring, in large part due to a recognition of the impact DDT had on wildlife and humans. In particular, DDT had devastated birds of prey, leading to some species being declared endangered. But while recovery of these species has been largely successful, Kurek remained curious about the legacy of DDT, particularly in New Brunswick lakes.
Kurek points out that other bird species, particularly insectivores, continue to suffer low populations. “We can make connections from the findings of our widespread use of DDT and declines in these insect-eating bird species,” he says. And yet, there’s been little investigation into potential residual effects of DDT. “When governments ban a contaminant, that often stops their efforts in learning about how that contaminant might impact the environment,” he says. “DDTs were banned … so we kind of moved on from that.”
While Kurek is quick to assure cottagers that the DDTs appearing in lake sediments don’t pose a particular threat to anyone swimming, boating, or working around the water. However, “given public concern about this, it might be wise to look a little more closely at the contaminant levels of DDTs and some of the fish species that people could be consuming … Because we eat fairly high on the food chain, we often acquire greater concentrations of contaminants because DDTs bioaccumulate.”