The amount of toxic chemicals released into the environment dropped 8 percent in 2000, continuing a decade-long trend of declining industrial pollution, according to a report released yesterday by the U.S. EPA. The Toxics Release Inventory compiles data from more than 23,000 factories, refineries, hard-rock mines, power plants, and chemical manufacturers, which together reported pumping 7.1 billion pounds of toxics into the nation’s air, water, and land in 2000. That’s down from 7.8 billion pounds in 1999, and represents a 48 percent decrease since 1988. The worst offenders were hard-rock mining companies, which accounted for 3.3 billion pounds of the toxics, followed by the utility industry, which was responsible for 1.1 billion pounds. For the first time, the report tracked chemicals such as dioxins, mercury, and PCBs, which tend to be released in small quantities but are extremely dangerous. Environmentalists called the findings a mixed bag, noting that the decline in direct toxic releases was more than offset by a 25 percent increase in managed toxic waste that wound up in Superfund sites, landfills, incinerators, and recycling facilities.