Toxic Mercury Lingers in Nevada Rivers Decades After Mining Boom

Study finds alarming levels of mercury in wood ducks along the Carson River, highlighting the enduring environmental impact of historic mining practices.

Published on Feb. 24, 2026

Got story updates? Submit your updates here. ›

Researchers at the University of Nevada, Reno have discovered alarmingly high levels of toxic mercury in wood ducks along the Carson River, a legacy of the Comstock Lode silver mining operations that took place in the 19th century. The study found that some ducklings carried mercury concentrations up to 66 micrograms per gram, far exceeding the FDA's safety level for human consumption. The contamination is a persistent issue stemming from the mercury amalgamation process used to extract gold and silver from ore between 1860 and 1895, during which an estimated 15 million pounds of mercury were lost to the Carson River drainage system.

Why it matters

The study highlights the enduring environmental impact of historic mining practices and the threat posed by mercury contamination to wildlife and potentially human health. As climate change brings more extreme weather events, the problem is expected to worsen as high flows wash out mercury from riverbanks and floodplains. Currently, Nevada does not have a statewide advisory for consuming wild waterfowl, raising concerns about potential health risks for those who regularly eat duck or fish from the Carson River.

The details

Researchers analyzed 15 years of feather samples from wood ducks that reside year-round along the Carson River, finding that mercury is continuously being absorbed by the aquatic food web, impacting invertebrates, fish, and the birds that consume them. The study also discovered that mercury levels are roughly three times higher in young wood ducks than in their mothers, driven by both inherited exposure and post-hatch consumption of contaminated invertebrates.

  • The Comstock Lode mining operations took place between 1860 and 1895.
  • The study was published in February 2026.

The players

University of Nevada, Reno

The university where the research on mercury contamination in Nevada's rivers was conducted.

Perry Williams

Associate professor in the College's Department of Natural Resources & Environmental Science and the principal investigator of the study.

Mae Gustin

Co-author of the study.

Nevada Bureau of Mines and Geology (NBMG)

The organization that estimates approximately 15 million pounds of mercury were lost to the Carson River drainage system during the Comstock Lode mining operations.

Food and Drug Administration (FDA)

The agency that has set a safety level of 1 microgram per gram for mercury in food for human consumption.

Got photos? Submit your photos here. ›

What they’re saying

“Mercury is not just in the water or in the banks. It's continuously being taken up…and everything in the food web. And we're part of that food web as well.”

— Perry Williams, Associate professor

“Exposure begins before they hatch. Mercury stored in adult females is transferred into developing eggs, giving ducklings an initial mercury burden at birth.”

— Perry Williams, Associate professor

“High flows 'wash out' mercury from the banks, increasing exposure for wildlife.”

— Mae Gustin, Co-author

What’s next

Continued monitoring of mercury levels in the Carson River and other impacted watersheds is crucial. Further research is needed to fully understand the extent of the contamination and its potential effects on both wildlife and human populations.

The takeaway

This study serves as a stark reminder of the long-term environmental consequences of 19th-century mining practices and the need for proactive measures to mitigate these risks. As climate change brings more extreme weather events, the problem is expected to worsen, underscoring the importance of responsible environmental stewardship.