Washington ? Hard-rock mining companies and coal-burning power plants are America’s largest toxic polluters, responsible for nearly two-thirds of the poisonous contaminants in the nation’s air and water, the Environmental Protection Agency said Thursday.

In its most comprehensive inventory of pollution and its sources, the EPA said mining of hard-rock minerals gold, silver, uranium, copper, lead, zinc and molybdenum was responsible for 3.4 billion pounds of toxic pollutants in 2000. Coal-burning electric plants were responsible for another 1.2 billion pounds.

While mines and power plants continued to be the biggest source of pollution, the EPA said the total amount of toxic chemicals released in 2000 had declined 8 percent from 1999, from 7.7 billion pounds to 7.1 billion pounds.

EPA’s latest annual Toxics Release Inventory was expanded to include eight new toxic chemicals, including dioxin. It also includes new reporting requirements for 20 other chemicals such as mercury and PCBs that are worrisome in even small amounts because they persist and accumulate in the food chain.

Dioxin and 11 other chemicals in the EPA inventory are covered under a global treaty banning so-called persistent organic pollutants that President Bush earlier this month sent to the Senate for ratification.

EPA Administrator Christie Whitman said the new data would help citizens make decisions about protecting their environment and assist the agency in analyzing trends nationally and locally.

The EPA focuses on the amount of toxic chemicals that industry reports as having been released into the environment, not the entire amount produced. In 2000, 38 billion pounds of such chemicals in production-related waste were reported as having been handled or processed an increase of 26 percent over the nearly 30 billion pounds in 1999, the EPA said.

Environmentalists contend many more chemicals are released into the environment after they are managed than is reported in EPA’s inventory. They say treatment facilities, incinerators and landfills don’t remove all the toxic chemicals, and that many federal Superfund sites that handle the nation’s most hazardous waste are leaking.