Some 5.7 billion pounds of toxic chemicals were released by industry to the nation's air, water and land in 1989, an 18 percent decrease from 1987 levels, the Environmental Protection Agency said Thursday.

However, while the EPA said its third annual Toxic Release Inventory report showed an apparent "downward trend" in pollution between 1987 and 1989, an environmental group said the agency's summary reflected only a tiny percentage of all harmful chemicals spewed out of smokestacks and discharge pipes.The Natural Resources Defense Council said dozens of high-pollution industries - ranging from mining to power plants to hazardous waste incinerators - were exempt from the federal "right-to-know" law requiring industry to report toxic discharges to the EPA.

In addition, hundreds of dangerous substances - including dioxin, numerous pesticides and radioactive wastes - were not on the list of chemicals that must be disclosed to the EPA, the group said.