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Environmental toxicity and climate crisis threaten Nepal’s medicinal plants

Heavy metal contamination also has implications on human health, while the climate crisis could greatly alter the habitats of plant species.

Arjun Poudel/ The Kathmandu Post/ ANN | Kathmandu |

Toxic metals like arsenic, cadmium, lead, and mercury have been found in three medicinal plants used in Ayurvedic medicines to treat common diseases and ailments.

Officials say the medicinal plants might have been exposed to such hazardous metals in the past too but they weren’t aware of the level of toxicity.

“This study was carried out to measure the levels of toxicity in medicinal plants,” said Dr Basudev Upadhyay, director general at the Department of Ayurveda and Alternative Medicine under the Ministry of Health and Population. “This study will help us compare the level of toxicity in the plants in the future.”

Toxic metals were assessed in Tinospora cordifolia (Guduchi), Berberis aristata (Daruharidra) and Neopicrorhiza scrophulariiflora (Katuki) in the study “Impact of Climate Change on Medicinal Plants of Selected Districts in Nepal-2020,” carried out by the department.

The study was carried out in three districts—Manang, Dhading and Parsa—and three important medicinal plants were chosen for the study.

The researchers traced 0.14, 0.008, 0.65, and 0.08 parts per million (ppm) of arsenic, cadmium, lead, and mercury, respectively in the sample of Neopicrorhiza scrophulariiflora.

Similarly, the sample of Berberis aristata had 0.08ppm of arsenic, 0.08ppm of cadmium, 0.08ppm of lead, and 0.04ppm of mercury.

The Tinospora cordifolia also showed 0.09ppm of arsenic, 0.08 of cadmium, 0.40ppm of lead, and 0.08ppm of mercury.

The World Health Organisation’s acceptable limits for these most common heavy metals are 3ppm for arsenic, 0.3ppm for cadmium, 10ppm for lead, and 0.03ppm for mercury.

“Environment pollution, mainly soil pollution, is the chief cause of high exposure of medicinal plants to toxic metals,” said Dr Puneshwar Keshari, an expert on medicinal plants. “The report of the study shows that negative impacts of environmental pollution are not only limited to cities but are also visible in rural areas. It has impacted not only food products and human health but also medicinal herbs.”

Tinospora cordifolia has been used for ages in the treatment of fever, jaundice, chronic diarrhoea, cancer, dysentery, bone fracture, pain, asthma, skin disease, poisonous insect, snake bite, and eye disorders.

Berberis aristata is used as an antibacterial, antiperiodic, antidiarrheal and anticancer medicine and it is also used in the treatment of ophthalmic infections. Neopicrorhiza scrophulariiflora is effective in curing fever, jaundice, hemorrhoid, and dysentery.

Experts say exposure to high levels of lead may cause anaemia, weakness, and kidney and brain damage. Exposure to excessive levels of mercury may cause lung damage, and potential damage to the brain and kidney, and blood loss.