People trust dentists with their health. Some members of Congress are more skeptical.

The dental industry, asked to testify Tuesday about pollution from mercury in tooth fillings, found itself under attack from lawmakers who blame mercury for everything from autism in children to skin discoloration.

The hearing was about whether dentists should be required to install "separator" equipment to keep pieces of fillings from getting into public wastewater. Currently, dentists in nine states are required to use separators.

The American Dental Association, before its spokesman testified, faced deeply personal diatribes from Reps. Dan Burton, R-Ind., and Diane E. Watson, D-Calif.

Burton began by saying he'd had a cap replaced, and a silver filling removed, over the weekend, and that he worried as he swished the water in his dentist's office about where his filling would go.

Then Burton talked about his grandson, saying the child became autistic not long after receiving nine vaccination shots, seven of them containing mercury. While such theories have been rejected in mainstream medicine, Burton has held several hearings on it in the past. Mercury has not been in childhood vaccines since 2001.

"Mercury should not be ingested into the human body in any way," he said.

Watson had her own issues. She blamed mercury fillings she got as a 9-year-old for allergies, headaches, darker and splotchy skin and trouble remembering people's names. She talked to researchers who thought she had mercury poisoning.

"I had to go to Mexico — I asked my own dentist about it, and he stuffed something in my mouth and wouldn't even discuss it," Watson said.

Mercury makes up as much as 54 percent of silver fillings, also called dental amalgam.

Last month, the government warned for the first time that silver dental fillings and the mercury they contain may pose a safety concern for pregnant women and young children. The Food and Drug Administration posted the precaution on its Web site to settle a lawsuit.

The ADA spokesman, William J. Walsh, seemed taken aback by the focus on mercury poisoning. He said his profession already acknowledges that dental fillings are the biggest single contributor to mercury in wastewater.

But his organization opposes a mandatory requirement for separators, which can cost anywhere from $750 to nearly $3,000 to install, according to Burton. Walsh said dentists have worked hard to keep filling pieces from getting into wastewater and today manage to keep about 80 percent from leaving their offices.

"Dentists drink and fish and swim in the same waters as everyone else in their communities," Walsh said. "They bring to these efforts the same commitment they bring to providing the best possible oral health care to the American people."

Polling indicates that people trust dentists to protect their health. A 2006 Gallup poll said people rated dentists as the fifth most trustworthy professions, after nurses, pharmacists, veterinarians and medical doctors and well ahead of clergy, journalists, business executives, lawyers, and politicians.