Effects of 50-year-old DDT spraying program still present in remote lakes of province

More than 50 years after New Brunswick stopped spraying DDT to kill the spruce budworm, researchers have found "concerning" levels of the banned pesticide in five remote lakes in north-central New Brunswick.

Mount Allison professor Josh Kurek is lead author of a study that set out to find how the lake ecosystems are recovering, but the results were not encouraging.

"The levels of DDT are concerning and are at levels that we know that aquatic organisms are harmed."

Kurek and his team took samples from the bottom of five remote lakes, Upsaquitch, California, Sinclair, Goodwin and Middle Peaked Mountain. Each is part of a different watershed in north-central New Brunswick.

Kurek began the research because he thought it would be a good chance to examine the long-term effects of a chemical like DDT, and the ability of the affected ecosystem to recover.

He was looking for "improvements in the organisms that exist in these lakes decades after we stopped using the insecticide."

Kurek said he was surprised to find that while DDT levels detected in the sediment do register a decrease, "modern sediments" or mud currently in contact with the water still has a high concentration of the chemical.

Those concentrations are high enough to affect organisms living in the lakes. One of the reasons Canada banned DDT in the early 1970s was the chemical's tendency to persist in the environment and accumulate in organisms.

Kurek said his research suggests that the lakes are now "radically different compared to years before use of DDT."

Budworm City

The report states that at least 5.7 million kg of DDT were sprayed on New Brunswick forests between 1952 and 1968. In comparison, Quebec used less than one million kg during the same time period.

"New Brunswick was ground zero for DDT to fight outbreaks of forest insects," Kurek said.

"These are some of the highest values in Canada."

A CBC report from 1957 said 220 planes armed with what was then considered a "miraculous" pesticide flew in and out of a remote airbase dubbed "Budworm City".

And while DDT was effective in killing insects, it became clear it also had a devastating effect on birds.

Peregrine falcons died in rapid succession after the increased usage of DDT.

DDT was banned in 1972, a decade after Rachel Carson's Silent Spring sounded alarms about the chemical, but the damage had been done. The peregrine falcon was listed as endangered in 1978.

The species was removed from the list nearly four decades later in 2017.

Legacy effect

Kurek said given the sediment levels they measured, there could be a lasting impact on wildlife.

"Other studies show contaminants can move from water to ground relatively easily."

He said small insects, living in fresh water are eaten by birds or frogs, and DDT can be passed from one to the other.

"Organisms that are eating other organisms will simply see more DDT in their fatty tissues."

"If it's still around our fresh waters, in our forest soils, organisms are being exposed to it, it's still kicking around our food web decades after we stopped using it."

Kurek said this study only looked at five lakes, but it's a cautionary tale.

"It's likely hundreds and hundreds of lakes across our beautifully forested province that probably contain a similar story."

The study is published in the peer-reviewed journal Environmental Science and Technology of the American Chemical Society.