Working to Find Ways to Reduce Selenium In Our Locally Affected Waterways
What is the Problem?
The problem with Selenium is: Elevated levels of selenium have been shown to cause reproductive failure and deformities in fish and aquatic birds.
Based on known margins of safety between normal and toxic dietary exposures, selenium is more poisonous than either arsenic or mercury. Most of us should not be worried about high selenium concentrations affecting our health. Selenium poisoning would only be an issue if a person were consuming selenium contaminated fish daily.
However, selenium, in minor amounts, is an essential trace nutrient for animals and humans. In July 1997, the State Water Quality Control Commission adopted a 4.6 ppb dissolved selenium (parts per billion - see definition below) aquatic life standard in the Gunnison River Basin.
Several stream segments (see maps) within the Gunnison Basin did not meet this new standard, and the E.P.A then imposed temporary standards modifications to allow measures to be taken locally in an attempt to bring these segments into compliance.
Locally, it has been shown that deep percolation from irrigation, large quantities of groundwater movement, and other sources may increase selenium concentrations in streams, ponds, reservoirs, lakes and wetland areas. Upstream from the major irrigated areas in the Colorado River Basin, including the Gunnison and Uncompahgre River Basins, selenium concentrations are generally less than 1 ppb, but downstream from irrigated areas, the selenium concentrations in surface waters often exceed the State standard.
The Gunnison Basin and Grand Valley Selenium Task Forces were formed to address these problems and resolve them at the local level. To learn more about what we are doing to address the selenium problems in each basin, take a look at the Grand Valley Action Plan or Gunnison Basin Action Plan.
What is a part per billion (ppb)? It was not until just recently that advanced analytical techniques allowed scientists to detect trace elements, such as selenium, at the parts per billion level. Although as a toxic element, selenium can cause environmental problems even at very low levels. The following is provided to help us gain perspective on the quantities in question: