Analysis of the eggs of wild birds in California's San Joaquin Valley appears to show that recycling agricultural runoff is causing high levels of selenium.
The U.S. Bureau of Reclamation is considering expansion of the recycling program, the Los Angeles Times reported. But this year's sampling of eggs found the highest levels of selenium in five years.
The drainage project keeps selenium-tainted water out of the San Joaquin River by using it to irrigate crops that can tolerate high levels of salt. Irrigation builds up levels of selenium and other chemicals that occur naturally by washing them out of the soil.
In the 1980s, water in farm drainage ponds became so toxic that it caused birth defects in birds.
"They have to be extremely careful; that water is so potent, they can't make any mistakes," said U.S. Fish and Wildlife biologist Joseph Skorupa. "If they make a mistake, they'll have dead birds."
Joe McGahan, coordinator of the reclamation program, said the high selenium levels could be a one-year spike. He said scientists have found no evidence that birds are dying or being born deformed.
Copyright 2006 by United Press International