Heavy Metal Contamination of Medicinal Plants in India - A Perspective

The presence of heavy metals in medicinal plants (MP) is a matter of serious concern as it directly affects human health. In India, the problem is especially significant since the country is a major consumer as well as exporter of medicinal plant-based raw materials and products. Raw material available in the market is often reported to contain traces of heavy metals and these consequently compromise the quality of medicinal plants-based medicinal formulations. In the present study, the reports of heavy metals in MP from India were collated to ascertain the extent of the problem and highlight the source of contamination. The states with the highest number of metals above permissible limits included Chhattisgarh, Maharashtra, Delhi, Kerala, Karnataka, and Uttar Pradesh. The levels of Cd and Cr metals were found to be the highest in Rajasthan, Odisha, Pb in Kerala and Hg, As in the state of Tamil Nadu. Plants growing in areas having mining activities as well as those growing on urban landscapes such as along roadsides or areas having an inflow of industrial effluents or agricultural run-off showed higher metal content than the standard limit. The presence of metals in natural habitats such as the mangroves and low lands of the Himalayan range was also noted. The review provides an insight into the magnitude of the issue, its causes and the possible lacuna that needs to be addressed to mitigate the problem.