Almost 4.1 billion pounds of toxic chemicals were released to the environment in the United States in 2007, according to new data from the Environmental Protection Agency’s Toxics Release Inventory. That’s a five percent overall drop from the prior year, but the release of several specific hazardous substances — including mercury, PCBs, and dioxins — all increased significantly.

The inventory itself has been the source of considerable political controversy. As the Center noted in its Broken Government project, the government made the reporting requirements for the inventory less stringent in December 2006 — meaning fewer facilities had to complete detailed reports. But in the omnibus appropriations bill signed into law by President Obama on March 11, Congress restored the old reporting rules — a change that will go into effect for next year’s TRI.

The program was established after the 1984 Bhopal chemical disaster in India and the release of chemicals from a West Virginia plant the following year.

You can search the TRI data here and the EPA’s summaries of key findings and tables of the facilities with the largest toxic releases here.

Among the hazardous substance releases that the EPA noted were on the rise in 2007:

• Mercury up 38 percent, mostly from mining industry facilities.
• PCBs up 40 percent. Widely used to insulate transformers and electrical equipment for decades, PCBs were banned from further production in 1979. But the EPA says that disposal of the material in hazardous waste landfills continues.
• Dioxins up 11 percent. These likely carcinogens are released at chemical manufacturing facilities, a byproduct of industrial processes.