Selenium, the toxic mineral that maimed and killed thousands of migratory birds at a national refuge in California, is present at "high" levels in at least nine other western areas receiving irrigation runoff, the Interior Department confirmed yesterday.
Five of the areas are national wildlife refuges, similar to the Kesterson refuge in the San Joaquin Valley, where federal officials have been forced to frighten birds away to prevent them from being harmed by contamination from agricultural waste water.
The survey, hastily conducted after the Sacramento Bee reported high levels of selenium at 23 sites in several western states, confirmed the newspaper's basic findings and suggests that the problem of toxic drainage from irrigated western lands may be far more widespread than earlier believed.
Assistant Secretary Robert N. Broadbent said Kesterson remains the only site where Interior Department officials have confirmed toxic effects on wildlife from selenium. The documents released yesterday said that identifying such effects would take detailed probing, and none has been done at any of the sites where the Bee took samples.
"We think there are other areas in the country that may have problems," Broadbent said.
At the root of the problem is the geography of the West. Selenium is a naturally occurring mineral, found in soils throughout the continent and necessary to life in minute amounts. At high levels, however, the mineral can be dangerous and even deadly.
According to Interior Department officials, acid soils, which are common in the East, are capable of binding selenium tightly so that it cannot be leached out by water. But in alkaline soils, which predominate in the West, selenium becomes water-soluble and washes from the soil.
Once free of the soil, selenium can work its way up the food chain. In Kesterson, the substance moved up through algae, insects and small fish until it reached levels that were lethal to birds.
The survey found troublesome selenium levels at three sites in California, including the Salton Sea National Wildlife Refuge, which acts as a natural reservoir for drainage water from the sprawling Imperial Valley. The valley grows millions of dollars worth of products, including much of the nation's winter lettuce, with the help of water from the federal Boulder Canyon Project.
Researchers have found high concentrations of selenium in the livers of waterfowl wintering in the Imperial Valley, the survey said.
Other areas of concern were the Benton Lake and Bowdoin wildlife refuges in Montana, which are watered by runoff from the Bureau of Reclamation's Sun River and Milk River irrigation projects, and the Stillwater National Wildlife Refuge in Nevada.
The report said there have been waterfowl deaths "from unknown causes" at Carson Lake near Stillwater, which also receives drainage from agricultural lands in the federal Newlands Project, but autopsies did not include analysis for selenium.
In addition to the nine areas with "high" selenium levels -- defined as at least 50 percent higher than normal levels at an uncontaminated state refuge in California -- the department found another nine areas where there is "some information to justify concern" about selenium contamination. Eight of those areas receive irrigation runoff, and two are national wildlife refuges.