The amount of toxic chemicals released into the environment nationwide in 2010 increased 16 percent over the year before, reversing a downward trend in overall toxic releases since 2006, according to a report released Thursday by the Environmental Protection Agency.

The spike was driven largely by metal mining, but other sectors — including the chemical industry — also contributed to the rise in emissions, according to the new analysis from the annual federal Toxics Release Inventory.

Air releases of dioxin, which is linked to cancer as well as neurological and reproductive problems, rose 10 percent from 2009 to 2010, according to the report. Other releases, such as landfill disposal, increased 18 percent.

Dioxins are formed as a byproduct of some processes with intense heat, such as smelting and recycling metals. The 2010 increase stemmed largely from the hazardous-waste-management and mining industries, according to the EPA.

In a statement Thursday, EPA Administrator Lisa P. Jackson did not address the specific sources of emissions but said that the public reporting “has played a significant role in protecting people’s health and the environment by providing communities with valuable information on toxic chemical releases.”

According to EPA officials, a handful of metal mining operations helped drive the overall increase in toxic emissions.

“In this sector, even a small change in the chemical composition of the ore being mined — which EPA understands is one of the reasons for the increase in total reported releases — may lead to big changes in the amount of toxic chemicals reported nationally,” the statement read.

Some environmentalists said the new data show why the EPA should swiftly move to release a long-anticipated environmental assessment of dioxin, the first installment of which the agency plans to issue this month. EPA officials say they will issue a report addressing dioxin’s non-cancerous effects first and then later release a cancer-related report.

Some industry groups, including the American Chemistry Council, have urged the EPA to hold off issuing the report in what the trade association’s president and chief executive, Cal Dooley, has called “a piecemeal fashion.” Chemical manufacturers accounted for nearly 64 percent of total disposal of dioxins in 2010, though they reported a 7 percent decrease from 2009 to 2010.

In a letter dated Dec. 20, Dooley wrote Jackson that “it is worth noting that the Agency’s efforts to manage dioxin emissions have been successful. Indeed, as a result of both regulatory and voluntary initiatives, U.S. dioxin emissions from man-made sources have dramatically declined and environmental levels of dioxin have plummeted.”

ACC spokeswoman Anne Kolton noted in an e-mail: “U.S. emissions of dioxin have declined more than 92 percent since 1987 [through 2009] to the point where backyard trash burning is the primary source of dioxin emissions.”

Mike Schade — a campaign coordinator for the Center for Health, Environment and Justice — said the fact that emissions are now on the upswing makes it important for the EPA to release a report it started working on in 1985.

“Communities across America have been exposed to dioxin for decades as EPA has continued to work on this study. Every American has measurable levels of dioxin in their body,” Schade said in an interview, noting that most humans are exposed by eating meat or dairy products from animals that have accumulated the chemical in their bodies. “It’s critically important for EPA to finalize this study so the EPA can protect Americans from this toxic chemical.”