Traditional herbal medicines used by Americans may contain high levels of toxins, a new study in the U.S. shows.

Published in the Journal of the American Medical Association, the findings say that an estimated 20 percent of Ayurvedic medicines, herbal mixtures used in India for thousands of years, contained toxins such as lead, mercury or arsenic.

Arsenic and many of its compounds are potent poisons which can cause cancer. Lead can damage nervous connections and cause blood and brain disorders, and mercury can lead to chronic and acute poisoning.

Starting 1978, more than 80 cases of lead poisoning have been reported across the world, the study’s authors said. 

Ayurveda medicines have been designed to prevent sicknesses by maintaining balance in the human body, mind, and “consciousness through proper drinking, diet, and lifestyle, as well as herbal remedies,” according to the University of Maryland Medical Center’s Web site.

Despite the fact that the medications are mainly used by adults, an estimated 4 percent of the 193 products which lead researcher Dr Robert Saper analyzed were designed to be used by children.

What researchers suggest, taking into consideration the study’s results, is that the use of herbal remedy should be more controlled. “Our first priority must be the safety of the public. Herbs and supplements with high levels of lead, mercury, and arsenic should not be available for sale on the internet or elsewhere," Saper said.