A Mount Allison professor is one of the lead researchers in a study that has documented the lasting legacy of large-scale pesticide spraying in New Brunswick in the 50’s and 60’s.
Josh Kurek and a team of researchers including some Mount Allison students have sampled sediments and Brook Trout from seven different lakes in the province, and looked for evidence of DDT, a synthetic insecticide widely used during and after World War II, and later widely banned due to its environmental effects.
In five lakes within the former spray zone, Kurek says the team found “measures that are some of the highest in North America. And that’s 60, 70 years after we stopped using DDT.”
Kurek says that on average, the levels of DDT found in the flesh of Brook Trout are 10 times above ecological guidelines.
The study and its findings were published Monday in the peer-reviewed and open access PLOS One scientific journal.
CHMA stopped in to the Environmental Change and Aquatic Biomonitoring (ECAB) lab on the Mount Allison campus to find out more.
During the 50’s and 60’s, says Kurek, “New Brunswick and its forestry stakeholders ran arguably the world’s largest aerial insecticide spray program,” with nearly all forests receiving at least one treatment of an insecticide.
When it comes specifically to DDT, the spray program was more selective, but still extensive. “Roughly 50% of our forests have received anywhere from one application to over 20 applications between 1952 and 1968,” says Kurek. DDT was sprayed in an attempt to control the spruce budworm, which plagues New Brunswick’s forest industry with outbreaks every few decades.
And now Kurek’s study shows that that DDT is still present in lake sediments, and finding its way into the province’s Brook Trout.
“We know that DDT persists a long time,” says Kurek. “It’s half life is anywhere from a few decades to up to 150 years. And so the environment at the bottom of lakes, it’s cold, it’s dark, it’s perfect to preserve DDT for long periods of time.”
“We tend to view lake sediments as a sink for pollution,” says Kurek. “We think about them almost as out of sight, out of mind.” But what’s happening now, says Kurek, is that lake sediments are now “a source of DDTs to both the aquatic and the terrestrial environment.”
“An insect that lives in the mud hatches from the lake, and then a bird or a bat can eat that insect,” says Kurek. “And so now there’s an aquatic to terrestrial link with pollution that we know is widespread in our province.”
Kurek wasn’t exactly surprised to find evidence of DDT in New Brunswick lakes and fish, given that the chemical is known to be a persistent organic pollutant. It’s the extent of what his study found that shocks him.
“When you can say that 50% of a province in Canada is polluted with a contaminant, that’s a shocking number,” says Kurek. And the amount of DDT and its metabolites the study found in Brook Trout is high. “They’re at levels of DDT in their tissue that would be similar to what we saw in the Great Lakes in the 50s and 60s,” says Kurek, “so shockingly high amounts.”
Kurek says, “there has to be harm to other organisms in the environment by such high amounts of the DDT, and part of our continuing work is to understand that.”
Kurek is not human health researcher, and says that while the DDT levels he’s found in New Brunswick fish are an ecological concern, Health Canada does not consider them a serious risk to humans. That said, Kurek still advises some caution to New Brunswick’s roughly 50,000 anglers, many of whom report Brook Trout as their number one fish to keep.
”Exposure, I think, is how you want to think about contaminants in the environment,” says Kurek. DDT is prone to bioaccumulation, that is that amount ingested can build up in tissue. “There’s a lot of DDT in our waters. It’s high in our fishes. I don’t think you want to be eating too many Brook Trout.”
For those who do eat Brook Trout, Kurek recommends following New Brunswick’s wild fish consumption guidelines, which favour smaller fish, and recommend that small children and breastfeeding women avoid Brook Trout over 25 centimetres.
Kurek finds himself studying the legacy impacts of New Brunswick’s enthusiasm for DDT thanks in part to a dinner party conversation, and the work of biologist Rachel Carson, who wrote the seminal book Silent Spring in 1962 .
Kurek recalls talking about research with a marine biologist a bit older than himself. “He said, you must know a lot about DDT in the province, given that chapter nine in Rachel Carson’s Silent Spring was titled Rivers of Death, and it was all about our use of DDT.”
At that point, recalls Kurek, “I was new to the province. I just started my professorship here at Mount Allison. My mind just kind of got excited, and I knew immediately that this is something that I should look into.”
Kurek’s lab, the Environmental Change and Aquatic Biomonitoring lab at Mount Allison studies legacy pollution and stressors.
“Most pollution, it’s not acute,” says Kurek. “It’s not like a nuclear bomb going off in a lake. It gradually builds up over time, and you have to have a long term perspective, long term data sets to really know how our pollution, or environmental change like climate warming, has affected the ecosystem.”
Kurek says he hopes the takeaway from the recently released study is not just about hindsight, but about present day and future considerations as well.
“Society needs to be aware that our broad application of synthetic chemicals has consequences,” says Kurek. “There are other contaminants, like salt that we apply to roadways and sidewalks that we know harm aquatic life and fundamentally alter the way that our fresh water systems work.”
And Kurek also points to the herbicide glyphosate, which is sprayed on New Brunswick forests to kill hardwoods and encourage softwood growth. “It doesn’t persist nearly as long as DDT, and so it has different properties, but it’s still a synthetic chemical that we’re applying all over the place,” says Kurek.
“I think this is a wake up call,” says Kurek of the DDT study. “The fact that something we applied 70 years ago can still be found in modern ecosystems, in such high concentrations and throughout the province, it should shock everyone into trying to do things better.”
