Oct 23, 2014 11:18 AM EDT By J Baulkman, UniversityHerald Reporter

Herbal medicines such as licorice, Indian rennet and opium poppy could contain dangerous levels of toxic mold.

A new study from researchers at the University of Peshawar in Pakistan suggests that the medicinal plant market goes untested for health hazards, putting herbal medicines at a higher risk of contamination with toxic mold.

An estimated 64 percent of people use medicinal plants to treat illnesses and relieve pain. The herbal medicine market is worth $60 billion globally, and growing fast. Despite the increasing popularity of herbal medicine, the sale of medicinal plants is mostly unregulated.

"It's common to use medicinal plants in our country and to buy from local markets and shops," Samina Ashiq, one of the authors of the study, said in a statement. "There's a common misconception that just because they're natural, the plants are safe. We knew from experience that this wasn't the case, but we wanted to really test it and quantify the contamination."

For the study, researchers analyzed 30 samples of plants known for their medicinal properties, including licorice, Indian rennet and opium poppy. They found that 90% percent of the samples were contaminated with mold, and the levels exceeded permissible limits in 70 percent of the samples.

They then grew the molds to find out if they produced toxins that could be harmful to human health. Nineteen percent of the molds produced aflatoxins, and 12 percent produced ochratoxin A. Overall, 31 percent of the molds growing on the plants they tested produced harmful toxins.

"These results are a clear indicator that we need more stringent regulation in place," Ashiq said. "There is a real public health concern due to the lack of effective surveillance of the quality, safety and efficacy of these medicinal plants. It's time for regulators to step in and set limits to protect people who want to use herbal medicines like these."

The plants can become contaminated at each stage of production: during growth, handling, collection, transportation and storage. Those that are exported for sale may be contaminated before they reach their destination. In Pakistan and many other countries, these plants are primarily sold on markets where hygiene is not top priority.

The findings are detailed in the journal Fungal Biology. 

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