Releases of toxic chemicals into the environment fell more than 6 percent in 2003, although the level of mercury (search), PCBs and dioxin rose, the Environmental Protection Agency (search) said Wednesday.

Some 4.44 billion pounds were released in 2003, the latest year for which figures are available, the EPA said. The decrease was partly due to metal mining's 1.5 billion pounds of releases, an 18 percent cut from the previous year.

Revised figures show that 4.74 billion pounds were released in 2002, a year that marked the first increase reported by EPA since 1997.

EPA officials said 23,000 facilities reported information on about 650 chemicals, including those managed in landfills and underground injection wells or emitted into the water and air.

Participation by facilities has fallen steadily. EPA said 24,379 facilities provided information in 2002, while 25,388 facilities reported findings in 2001.

Environmentalists expressed concern at the increases in three chemicals that do not easily degrade and work their way up the food chain.

"Although it is good news that overall releases are back on track, it is a major concern that some of the most hazardous chemicals have increased so dramatically," said Meghan Purvis, an environmental health advocate for the U.S. Public Interest Research Group (search).

Mercury releases from coal-burning power plants and other industrial sources were 7.4 million pounds, 41 percent higher than in 2002. Most at risk of nerve damage from the toxic metal are pregnant women, women of childbearing ages and young children.

About 22 million pounds of polychlorinated biphenyls, or PCBs, were released — a 1,000 percent increase from a year earlier. PCBs have been banned by the government as a suspected cancer-causing agent, but they were once used as insulators in electrical equipment.

Releases of dioxin, a chemical that can be hazardous even in small amounts, rose to 269,037 grams, a 93 percent increase from 2002.

Lead releases were 432 million pounds, a 7 percent increase. It is the third year in a row that the EPA is requiring facilities to tell state and federal authorities about lead releases of more than 100 pounds. Only much larger releases were reported previously.

EPA's annual Toxics Release Inventory began under a 1986 community right-to-know law. The biggest polluters in recent years have been hard-rock mining companies and electric utilities.

Purvis said EPA, which has been considering proposals to change the public information program, should resist anything that might reduce what gets reported.

"When facilities have to report their toxic releases to the public, they reduce them," she said. "The Bush administration should not weaken the public's right to know."