IDAHO — Wildfires have been burning across Idaho this summer, and their list of harmful impacts is long. But a recent U.S. Geological Survey has added another bad side effect to the list: the rise of a toxic chemical. The study sampled 57 streams at the beginning of river systems in Idaho, Oregon and Washington for mercury, a chemical that can damage the human nervous system at high concentrations. In both water and sediment from the streams, one-year post-fire, mercury concentrations were higher. Concentrations of methylmercury, the most toxic form of mercury, were also 178% higher in water from burned streams. Insects that filtered stream water or ate debris also had higher levels. The compound becomes dangerous as it accumulates in animals over time, according to the WHO. “There hasn’t been a lot of work done on the effects of wildfire on mercury,” Austin Baldwin, a USGS research hydrologist who led the study.