WASHINGTON — Democratic lawmakers are questioning a Bush administration plan to eliminate requirements for farms to disclose air pollution from animal waste.

Currently, farms must report to federal, state and local officials when emissions of hazardous substances like ammonia and hydrogen sulfide exceed certain levels. In a little-noticed proposed rule change published in the Federal Register on Dec. 28, when Congress was on its winter recess, the Environmental Protection Agency proposed eliminating the reporting requirement.

The EPA argued that the requirement created an unnecessary burden for farms and that the emission-release reports weren't acted on at the federal level. The public comment period for the proposed change closes March 27.

Democratic Rep. John Dingell of Michigan, chairman of the House Energy and Commerce Committee, sent a letter to EPA Administrator Stephen L. Johnson on Tuesday arguing that the proposed reporting exemption "appears ill-considered and contrary to the public interest." The letter was also signed by Reps. Hilda Solis, D-Calif., and Al Wynn, D-Md.

"The Bush administration's plan to exempt industrial-sized animal feeding operations from emissions reporting requirements is nothing more than a favor to big agribusiness at the expense of the public health," Dingell said in a statement.

EPA spokesman Jonathan Shradar said agency officials would review and respond to Dingell's letter. He said that the proposed exemption is limited in scope, as it would only apply to emissions from animal waste.

A February 2004 memo from EPA's Office of Air Quality Planning and Standards concluded that exposure to ammonia emissions at the 100 pound-per-day level that triggers the reporting requirement could irritate the respiratory tract, eyes and mucus membranes for a few days. Exposure to hydrogen sulfide at that level could have the same but longer-lasting effects accompanied by memory problems, headaches and dizziness.

According to EPA hearing testimony to Congress, an estimated 140 animal-feeding operations reported ammonia releases exceeding the 100 pound-per-day level in the 2006 fiscal year, and an estimated 130 operations in the 2007 fiscal year. Some facilities regularly exceeded the reporting levels. One example was a dairy farm in Oregon called Three Mile Canyon Farms, which reported daily ammonia emissions of 15,500 pounds.

There are no federal laws or regulations capping release of these substances from animal waste, so EPA critics argue that the reporting requirements are the only way for communities to know what they're being exposed to.

"If the public doesn't know that the emissions in their area are hazardous to their health, how are they going to find out, unless the sources are required to report?" asked Bill Becker, executive director of the National Association of Clean Air Agencies. Becker said the reports are used by some states to respond to local concerns about farm pollution.