Pesticides and pharmaceuticals: B.C. waters contaminated following 2021 floods

Pesticides and pharmaceuticals: B.C. waters contaminated following 2021 floods
Pesticides and pharmaceuticals: B.C. waters contaminated following 2021 floods

The catastrophic flooding of November 2021 caused widespread damage to many parts of British Columbia, and the impacts are still being felt to this day.

One area hit exceptionally hard was the Lower Fraser Valley, originally known as the Semá:th X̱ó:tsa (Sumas Lake) region. The widespread contamination of the waters of the Lower Fraser Valley is detailed in a new report released by the Raincoast Conservation Foundation, A lake re-emerges: Analysis of contaminants in the Semá:th X̱ó:tsa (Sumas Lake) region following the BC floods of 2021.

The study, presented to Sumas First Nation on November 17th, documented an astounding diversity of contaminants including excess nutrients, metals, fecal coliform, hydrocarbons, pesticides, pharmaceuticals and personal care products, perfluorinated compounds, sucralose and tire-related chemicals in fish habitat.

According to researchers, there were 59 exceedances of Environmental Quality Guidelines among the surface water samples during their study, “suggesting that fish habitat in the Semá:th X̱ó:tsa region is heavily degraded by multiple contaminants.”

The Raincoast Conservation Foundation and their partners took samples of water in the former Semá:th X̱ó:tsa (Sumas Lake) area over a seven-week period following the floods. Twenty-nine surface water samples were collected, and 379 analytes were examined, including 262 anthropogenic contaminants.

Researchers noted, “While no Environmental Quality Guidelines are available to interpret the 177 new and emerging contaminants in this study, the widespread detection of cocaine, painkillers, and pesticides raises fundamental questions about the health of an area that is home to both fish and people.”

While the lack of baseline data prior to the floods makes it difficult to determine the extent to which the 2021 disaster may have impacted water quality, researchers say the degradation in the health of Sumas fish habitat became clear during this study.

"The flood did us a favour," said Raincoast Conservation Foundation program director Dr. Peter Ross in an interview with The Weather Network. "We were asleep at the switch and the floods reminded us that collectively we are leaving our footprint on healthy fish habitat and that's going to have consequences".

The Raincoast Conservation Foundation is a part of many projects that help protect the environment and land in British Columbia. For more information please visit their website,

For more details on the Raincoast Conservation Foundation's report, watch the video that leads this article.