MIAMI — Everglades game fish recently were found to contain mercury in some of the highest concentrations ever recorded in the United States, and environmental experts were searching for a cause.
Last week, the Florida Department of Health and Rehabilitative Services issued warnings against eating largemouth bass or warmouth caught in the western portions of Palm Beach, Broward and Dade counties.
Samples of the fish were found to contain up to 4.4 parts per million of methyl mercury--more than four times the maximum level the federal government considers safe.
"That's one of the highest concentrations ever recorded in the country," Frank D'Itri, a Michigan State University expert on mercury, said.
New tests have been ordered all over southeastern Florida since the unexpected findings.
Scientists said they are puzzled by the presence of methyl mercury in the Everglades. The poisonous metal has been found frequently in the industrial Northeast, but seldom in Florida's rural wetlands.
Mercury, which is especially dangerous to unborn children, can damage the central nervous system. Eating enough of the Everglades fish to cause such damage would take months, but over a long enough time, poisoning would show its effects.
There are many theories as to how the metal could have entered the fish, scientists said.
Winds from other regions could have blown mercury-laden factory smoke into southern Florida from as far away as Mexico. Midnight dumpers could have left residue from electronic manufacturing in the Everglades. Another theory holds that conditions of fire, drought and rain could combine to leech the heavy metal from natural deposits in the soil.