Pesticides, normally found in Great Lakes tributaries during summer, now found year-round

Pesticides are making their way into tributaries around the Great Lakes, many at toxicity levels that exceed federal thresholds considered safe for aquatic life, according to a recent study.

A study published in Environmental Toxicology and Chemistry shows that these pesticides are present year-round and not just during the warmer months when they are typically applied.

“What you use makes it into the water,” Sam Oliver, an author of the study, and a scientist with the U.S. Geological Survey who researches lakes and water quality.

The study also identified specific compounds that make up common herbicides, fungicides and insecticides of particular concern throughout the region. One such concern is atrazine, one of the world’s most common herbicides, which is also known for turning some male frogs into females.

From 2015 to 2016, the team of scientists took water samples in 16 tributaries, representing different land uses across all five lakes: agriculture, urban or a mix of the two. For example, the Bad and St. Louis Rivers that drain into Lake Superior are mostly forested or surrounded by wetlands, so they see low human impacts. The Maumee River, which flows into Lake Erie, runs through Ohio’s breadbasket. The Milwaukee River was one river that the scientists sampled that flows through an urban landscape, along with the Cuyahoga River, flowing through Cleveland to Lake Erie.

In urban and suburban areas, herbicides and insecticides are used to maintain golf courses and lawns as well as for pest control. Fungicides are commonly used in building materials to kill or stop the growth of mold.

“Freshwater ecosystems are very vulnerable to these pesticides… because they can get into the water in so many different ways,” said Cheryl Nenn, who manages the water quality monitoring program for Milwaukee Riverkeeper. Pesticides can soak into the land getting into the groundwater or they can wash directly into the water.

What is particularly concerning, though, is that high levels of pesticides were found all year, much longer than previous studies have shown, Nenn said.

Because there are so many chemicals that wash into these rivers, it’s unclear what the exact impact on aquatic life might be, Oliver said.

But Oliver hopes the results will help when it comes to protecting freshwater around the region, showing what compounds should be prioritized. It also will help scientists zoom in on what compounds to look at to better understand how pesticides impact fish and other aquatic life.

All but one river had unsafe pesticide levels

All but one of the rivers sampled, the Bad River, had pesticide levels that exceeded benchmarks set by the Environmental Protection Agency. Even the St. Louis River, flowing through relatively pristine forest and wetland habitats, exceeded federal levels four months out of the year.

The Maumee River, which has the largest watershed flowing into the Great Lakes, had the highest levels of pesticides. Researchers found 72 pesticides in the river, 47 of them above federal thresholds.

Pesticides aren’t the only type of pollution in the Maumee River; there is a long history of environmental contamination. Every summer, Lake Erie is plagued by harmful algae blooms caused by fertilizer runoff largely making its way to the lake via the Maumee.

More: What's the state of the Great Lakes? Successful cleanups tempered by new threats from climate change

In Wisconsin, the Manitowoc River had the most hazardous levels of pesticides, followed by the Milwaukee and Fox rivers. The team found a total of 35 different pesticides in the Manitowoc River and 31 in the Milwaukee River, according to Oliver.

One challenge in assessing the impacts of pesticides is that when they get into the water, they can break down, Nenn said. When that happens, the pesticide is no longer detectable, only the byproducts.

Nenn said that a lot of times these chemicals make it to market before scientists and agencies understand the impacts. And then it’s a “huge lift” to get them restricted or banned after the fact, she said. She added that manufacturers have a lot of influence over policy decisions, adding even more of a hurdle.

But she’s hopeful that studies like this could lead to “policy conversations” about how to better regulate these chemicals.

Caitlin Looby is a Report for America corps member who writes about the environment and the Great Lakes. Reach her at clooby@gannett.com or follow her on Twitter @caitlooby.

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This article originally appeared on Milwaukee Journal Sentinel: Pesticides found in Great Lakes' tributaries year-round, study says