Selenium and human health implications in California's San Joaquin Valley

An evaluation was conducted on the human health impacts of elevated levels of selenium in the Kesterson National Wildlife Refuge and its surroundings in Merced County, California. Investigative activities of various agencies were summarized and assessed. Agricultural waste water not intended for human use showed elevated selenium concentrations of up to 1400 ppb. Levels of selenium in fish (up to 96 ppm, wet weight), aquatic birds (up to 130 ppm in liver, dry weight), and waterfowl (up to 5.3 ppm flesh, wet weight) were unsafe for unrestricted human consumption. Data on selenium in drinking water (less than 10 ppb), animals (mean values: beef liver 0.3-0.35 ppm, wet weight; milk, 0.01-0.02 ppm), and air (particulate, 14.8 ng/m3; gaseous, less than 1080 ng/m3) did not suggest a high level of exposure. Selenium concentrations in soil were highly variable and suggested a potential source of high exposure. Selenium values in blood and urine of workers were within normal range. A community health survey did not show any trend of adverse health effects in the local population.