Under a bridge near downtown Whitefish, Paige Weigand is wading into the Stillwater River. She’s with the Flathead Lake Biological Station and is here to collect water that will be tested for pesticides.
Weigand plunges an amber glass bottle into the turquoise water.
“We try to hold it up in the middle of the water column and wait until it fills,” she says.
This is the second year of water sampling. Rachel Malison is one of the researchers analyzing the data. The 600 samples taken from Butte to the Flathead last year did contain low levels of mostly herbicides like 2,4-D and Atrazine, among many others. Some fungicides and insecticides were also detected.
“So we’re getting detections from April all the way to November," Malison says. "Even though the pesticides aren’t being really sprayed in November, they are still in the water.”
Malison’s team has identified hotspots throughout northwest Montana. Those sites either had more frequent detections or higher concentrations.
“I believe five out of six of those hotspot sites were all downstream of urban-suburban areas," she says. "Only one was downstream of a predominantly agricultural use area.”
That shows pesticide runoff is coming from a variety of sources, including people spraying lawns, and industrial uses – not just farm fields.
Malison says until now, there’s been very little data on how much pesticides are leaching into waters and where those chemicals are coming from. As an ecologist, she’s mostly worried about impacts on fish, plants and insects.
Most detections were below what’s considered harmful to people. But Malison thinks Montanans should know what they’re being exposed to, "Because it’s really hard to know all the effects.”
Malison says the Biological Station will be sharing its findings with communities. Her team also plans to work with people interested in reducing their pesticide use. That work will happen over the next few years.
