The amount of toxic chemicals emitted by industry in the U.S. grew by 5 percent in 1999, the U.S. EPA said yesterday in its annual Toxics Release Inventory. Two-thirds of the 7.7 billion pounds of chemicals came from hard-rock mining companies and electric power-plant operators. Four mining states — Nevada, Utah, Arizona, and Alaska — headed the list, as they did in 1998, the first year releases from the mining industry were considered. Environmentalists said the data show the danger of rolling back environmental protections. In particular, they criticized President Bush’s decisions to rescind new regulations that would have reduced the amount of arsenic in drinking water and pollution from hard-rock mining operations — two moves that favor the mining industry.