NEW IDRIA, Calif.--Abandoned mercury mines throughout central California's rugged coastal mountains are polluting the state's major waterways, rendering fish unsafe to eat and risking the health of at least 100,000 impoverished people.
But an Associated Press investigation found that the federal government has tried to clean up fewer than a dozen of the hundreds of mines—and most cleanups have failed to stem the contamination.
Although the mining ceased decades ago, records and interviews show the vast majority of sites have not even been studied to assess the pollution, let alone been touched.
While millions live in the affected Delta region, the pollution disproportionately hurts the poor and immigrants who rely on local fish as part of their diet, according to a study conducted by University of California, Davis ecologist Fraser Shilling. His research found that 100,000 people, which he calls a conservative estimate, regularly eat tainted fish at levels deemed unsafe by the U.S. Environmental Protection Agency.
"Tens of thousands of subsistence anglers and their (families) are consuming greater than 10 times the U.S. EPA recommended dose of mercury, which puts them at immediate risk of neurological and other harm," Shilling said.
But neither the state nor federal government has studied long-term health effects of mercury on the people who regularly eat fish from these waters.
The legacy of more than a century of mercury mining in California—which produced more of the silvery metal than anywhere else in the nation—harms people and the environment in myriad ways.
Near a derelict mine in this California ghost town, the water bubbling in a stream runs Day-Glo Orange and is devoid of life, carrying mercury toward a wildlife refuge and a popular fishing spot.
Far to the north, American Indians who live atop mine waste on the shores of one of the world's most mercury-polluted lakes have elevated levels of the heavy metal in their bodies and fears about their health.
And other mercury mines are the biggest sources of the pollution in San Francisco Bay and the Sacramento-San Joaquin River Delta, the largest estuary on the Pacific Coast.
In all, this metal known as quicksilver has contaminated thousands of square miles of water and land in the northern half of the state.
Records and interviews show that federal regulators have conducted about 10 cleanups at major mercury mines with mixed results, while dozens of sites still foul the air, soil and water. The AP's review also found that the government is often loathe to assume cleanup costs and risk litigation from a failed project.
Mercury from mine waste travels up the food chain through bacteria, which converts it to methylmercury—a potent toxin that can permanently damage the brain and nervous system, especially in fetuses and children.
The federal government calls methylmercury one of the nation's most serious hazardous waste problems, and the Centers for Disease Control and Prevention says it is a possible carcinogen.
Mercury is considered most harmful to people when consumed in fish. People who regularly consume tainted fish are at risk of headaches, tingling, tremors and damage to the brain and nervous system, according to the CDC.
The toxin is less of a threat in drinking water, which is filtered and monitored more closely.
Mining in California ceased decades ago, leaving behind at least 550 mercury mines, though no one knows for sure how many. One U.S. Geological Survey scientist says the total may be as high as 2,000.
"Mercury tops the list as the most harmful invisible pollutant in the (state's) watershed," said Sejal Choksi of San Francisco Baykeeper, an environmental watchdog group for the bay. "It has such widespread impacts, and the regulatory agencies are just throwing up their hands."
In the 19th and 20th centuries, California produced up to 90 percent of the mercury in the U.S. and more than 220 million pounds of quicksilver were shipped around the world for gold mining, military munitions and thermometers. Much of the liquid mercury was sent to Sierra Nevada gold mines, where miners spilled tons of it into streams and soil to extract the precious ore.