High levels of DDT found in N.B. brook trout decades after spraying

Rhythm Rathi · CBC News

· Posted: Apr 28, 2025 5:00 AM EDT | Last Updated: 22 minutes ago

A pesticide sprayed connected New Brunswick forests much than 55 years agone tin inactive beryllium recovered successful immoderate brook trout successful the province, according to a caller study.

DDT was sprayed from planes across bluish and cardinal New Brunswick — much than fractional the state — between 1952 and 1968 to power the spruce budworm feeding connected coniferous trees.

And the synthetic insecticide near a residue that hasn't disappeared.

"I deliberation it's important that radical are alert of the information that this bequest pollutant exists successful today's situation astatine precise precocious concentrations," said Joshua Kurek, an subordinate prof of biology subject astatine Mount Allison University and the main researcher connected the study.

Kurek said his probe squad sampled and studied trout, which helium described arsenic 1 of the astir harvested food successful New Brunswick, from 7 lakes crossed the province.

The harmful biology effects of DDT became wide known to the nationalist aft Rachel Carson's influential publication astir pesticides, Silent Spring, came retired successful the aboriginal 1960s.  

New Brunswick stopped spraying DDT successful the precocious 1960s, alternatively going with different pesticides, including fenitrothion, which was also arguable but was recovered to interruption down rapidly and not persist successful nature. The state present takes a much targeted attack to controlling the budworm.

But DDT, though it was not the astir commonly utilized pesticide successful the spray program, has persisted successful ungraded and successful New Brunswick's aquatic environment. 

WATCH | 'That is however DDT is transferred done the nutrient web': 

When Kurek looked astatine its beingness successful immoderate brook trout populations, helium discovered DDT successful concentrations 10 times greater connected mean than the levels identified successful Canadian ecological guidelines arsenic being healthy for wildlife.

The guidelines accidental up to 14 nanograms of DDT per gram of trout, for example, would not beryllium expected to origin adverse effects successful wildlife that devour the fish.

Five of the 7 lakes Kurek studied were successful areas wherever DDT was sprayed: Upsalquitch, Goodwin, California, Sinclair and the Middle Peaked Mountain. 

The remaining 2 — Anthony and Bennett — were extracurricular the spray zones and were chosen for DDT comparisons crossed the province, Kurek said.

He said the acheronian and chill situation astatine the bottommost of these lakes is favourable for preserving DDT.

"Typically, organisms get DDT done their diet, what they are eating," Kurek said.

Insects that unrecorded successful the water mud volition devour sediment with DDT content. These insects are nutrient to the brook trout, then further consumed by loons, minks, otters and humans, said Kurek.

"So if it's successful the trout, it's successful these different organisms arsenic well, due to the fact that they signifier portion of the the broader nutrient web."

Kurek described DDT arsenic a "probable" carcinogen.

The World Health Organization's International Agency for Research connected Cancer and the U.S.  Environmental Protection Agency person recognized DDT arsenic a probable quality carcinogen.

Low levels of DDT were detected successful trout from the 2 lakes extracurricular the spray zones, which shows the insecticide travels successful the environment, Kurek said. 

He said it tin question atmospherically, and it tin beryllium carried from onshore to adjacent h2o bodies by dense rainfall oregon aboveground water.

DDT contiguous successful the nutrient web associated with these lakes bio-accumulates, oregon keeps gathering up successful the tissues of organisms specified arsenic trout, Kurek said.

"And past arsenic you determination up the nutrient chain, its abundance successful organisms besides is magnified, and truthful organisms astatine higher levels successful the nutrient concatenation thin to person higher concentrations of pollutants similar DDT successful their tissues," helium said.

Kurek said his adjacent probe requires sampling much lakes to further recognize however the pollutant enters the lakes from wood soil. 

"We privation food populations that are doing well," helium said. "When they person precocious amounts of contaminants similar DDT successful their tissue, they're not going to bash precise well."

A spokesperson for New Brunswick's Department of Health said successful an email that the DDT levels recovered successful the brook trout probe transcend line levels for wildlife that devour trout, but not those for humans.

"The guidelines developed to support quality wellness person levels that are galore 100 times higher due to the fact that wildlife consumers, similar birds of prey, person precise antithetic fare patterns than human," spokesperson Tara Chislett said.

Chislett advised New Brunswickers to travel the provincial food depletion limits, for assorted species, including trout.

According to New Brunswick's food depletion guidelines, radical 12 oregon older tin person 8 monthly servings of brook trout that are shorter than 25 centimetres. Pregnant oregon breastfeeding women, infants and children up to the property of 11 should person lone 1 monthly serving.   

With food that are much than 25 centimetres long, the guidelines urge radical 12 or older have nary much than four monthly servings, portion large oregon breastfeeding women, infants, and children up to the property of 11 should not devour any.

The serving sizes mentioned successful the provincial guidelines are 75 grams, 125 millilitres oregon "a information of cooked food that fits successful the thenar of the consumer's hand."

The crushed for the immense spread betwixt quality and wildlife depletion guidelines is that humans lone devour fillets, portion the wildlife would devour the full fish, hence consuming much DDT, said Kurek.  

Kurek's survey is published successful the peer-reviewed diary PLOS One.