Dentists are facing new pollution rules from the Environmental Protection Agency that could cost the industry millions of dollars to comply with.
The EPA is targeting the excess mercury often used in dental fillings, and is seeking to have dentists filter out the substance when dumping into the water supply.
The agency proposed the rules in September, but is just now publishing them in the Federal Register, which starts a 60-day comment period.
The agency estimates the rules would cost the dental industry between $44 million and $49 million each year.
Dental amalgam, which is used in teeth fillings, contains mercury. EPA says allowing the substance to be put in the water supply is a threat to public health.
"Removing mercury from the waste stream when it is in a concentrated and easy to handle form like in waste dental amalgam is an important and commonsense step to take to prevent that mercury from being released back into the environment where it can become diffuse and a hazard to humans," the agency wrote.
The public has 60 days to comment on the proposed rule.