A coalition of anti-coal export groups is calling for a regional impact study of proposed Oregon and Washington export terminals.

The three terminals under consideration -- Gateway Pacific near Bellingham, Wash.; Millennium Bulk Terminals in Longview, Wash.; and Ambre Energy's Morrow Pacific Project in Boardman, Ore. -- would export a total of 100 million metric tons of coal annually to Asia if all are built.

The petition, to the U.S. Army Corps of Engineers offices in Seattle and Portland, Ore., requests that the requested area-wide environmental impact study include effects from increased mining in Wyoming and Montana, particularly on public lands; increased rail traffic throughout Wyoming, Montana, Idaho, Washington and Oregon and the effects of coal export on domestic energy security and pricing.

Groups who signed the petition include the National Wildlife Federation, the Sierra Club and Greenpeace.

"The threats from these coal export proposals connect communities across the region and cannot be overlooked," Cesia Kearns, senior campaign representative for Sierra Club's Beyond Coal Campaign, said in a statement.

Amid low prices and weak demand in U.S. markets, Western coal producers aim to send more coal from the Powder River Basin in Montana and Wyoming to Asia.

Proponents of the export terminals argue that if the U.S. doesn't make inroads into surging Asian coal markets, other nations will step in to offer that coal, but opponents of the terminals cite coal dust, diesel pollution and increased rail traffic as concerns.

"Coal is the dirtiest and most dangerous fossil fuel," Dr. Susan Katz of Oregon Physicians for Social Responsibility, said in a statement. "The production, transport and combustion of coal is harmful to its workers and to everyone else along the line, from the mines, to the trains, to the barges, to the ports and beyond."

The Alliance for Northwest Jobs and Exports, a Seattle group of business organizations and others who support the export terminals called the coalition's appeal "a stall tactic, pure and simple."

"We continue to support the (environmental study) process as it exists today," Lauri Hennessey, a spokeswoman for the alliance was quoted as saying by The Herald newspaper of Everett, Wash.

A report released this week by the National Mining Association says that rising exports of U.S. coal to Europe and Asia added $16.6 billion to the United States' economy in 2011.

"These findings underscore the potential for other states, especially on the West Coast, to benefit economically from sharply rising coal demand from Asia projected over the coming decades," said NMA President and Chief Executive Hal Quinn, in a statement.