COEUR d’ALENE — Lead and arsenic concentrations in sediments and recreational waters along Lake Coeur d’Alene and the Spokane River have changed little in the past 25 years, according to a new report from the Idaho Department of Environmental Quality. Metals in open water are unlikely to pose unacceptable health risks as well.

Analysts say that's good news. 

“I think we should be very pleased with these results,” said Haley McDaniel, a senior water quality analyst with DEQ. 

In 2022, the National Academy of Sciences recommended a reevaluation of human health risks from metal exposures around Lake Coeur d’Alene. Those risks were last evaluated in 1998. 

The project’s purpose was to determine whether metals currently present in sediments and recreational waters could harm people while recreating and working on Lake Coeur d’Alene and the Spokane River. 

In 2024, scientists sampled dry sediment, wet sediment, nearshore water, open water and upland soil at 32 sites around the lake and along the river. Most of the sites are publicly accessible. Eight have private owners. 

The samples were analyzed for contaminants of potential concern, including lead and arsenic, and compared to risk-based screening levels (RBSLs) for these chemicals. 

RBSLs are created by using the most current information about the health effects of different chemicals, provided by the Environmental Protection Agency, along with a set of exposure circumstances. 

Mara Thorhaug, an environmental health scientist, joined McDaniel on Wednesday at the Iron Horse in downtown Coeur d’Alene to present DEQ’s findings to the 4C Natural Resources Committee, an informal group of agency officials, local department managers and supervisors and community members. 

“With our open water samples, none of the samples were greater than the screening levels for any of the chemicals,” Thorhaug said. “For near-shore surface water samples, we found that some sample areas were greater than the screening levels for arsenic and some were for lead, but none of the other chemicals.” 

All sample areas for sediment and soil exceeded arsenic screening values, Thorhaug said. However, she noted that the EPA updated arsenic toxicity levels last year, setting a significantly lower RBSL for arsenic. 

“Like lead, there’s no known need for arsenic in our bodies,” Thorhaug said. “The science supports a lower toxicity value.” 

She added that this region has a higher amount of naturally occurring arsenic than some other locales. 

“What we found was the lead and arsenic concentrations in 2024 are actually very similar to those that we found in 1998,” she said.

The risk evaluation included some additional considerations, Thorhaug said, including maximum contaminant levels in drinking water and target blood levels. With these considerations in mind, 11 sites exceeded arsenic screening levels. 

Those sites were Corbin Park, Cheamkwet Park, Atlas Waterfront Park, Blackwell Island, Yap-Keehn-Um Beach, Boardwalk Public Beach, Sanders Beach West, Higgens Point Day Use, Q’emiln Park and two privately-owned sites. All 11 sites were “well below” the action levels at the Bunker Hill Superfund Site, which are 100 milligrams per kilogram arsenic and 700 milligrams per kilogram lead. 

“When it comes to these concentrations, I would have zero problem with my kids playing in any one of these areas,” McDaniel said. “What I would do, and what I think we should do as adults in charge of children in this region, is adhere to safe play practices.” 

DEQ plans to publish the complete findings on its website within the next month.