With a food safety bill likely to be introduced in Congress next month, a new report on herbal supplements is adding to the debate about regulation of this growing industry. The report, released Wednesday by the Government Accountability Office, found that almost all the herbal dietary supplements tested contained trace levels of heavy metals, including lead, cadmium, arsenic and mercury, and 16 of the 40 products tested contained pesticide residues that exceeded the legal limit, The New York Times reports.

The tests did not find levels of heavy metals above the legal limit. However, one herbal supplement, Vita Breath, was found to contain lead at 10,000 times the recommended limit. An industry representative said it is not surprising that herbal supplements contain traces of heavy metals because they are common in plants. A health official from the Food and Drug Administration also expressed confidence in the overall safety of dietary supplements.

The GAO report also found at least nine products that included illegal health claims, including one advertised as a treatment for Alzheimer’s and another sold as a cancer treatment.

Congress is expected to take up the food safety bill in two weeks, and it is not clear how much additional regulation the $25 billion-a-year industry will receive. For example, almost all the vitamin C supplements taken in the U.S. are made in plants in China, where the FDA does not have to perform inspections and almost never does.

Sources told The Times that mandatory recalls of dangerous products and manufacturer registration with the FDA will most likely make it into the bill; a requirement that supplements include only FDA-approved ingredients and the submission of approved safety plans by manufacturers will most likely not make it into the final version.

The GAO’s report and a video showing examples of deceptive marketing of herbal supplements is available here.