IIT Gandhinagar and University of Illinois study finds herbal cigarettes emit harmful particles comparable to tobacco smoke

A joint study by the Indian Institute of Technology Gandhinagar and University of Illinois Urbana-Champaign has found that herbal cigarettes marketed as natural and tobacco-free alternatives are not safer than conventional tobacco cigarettes and can produce emissions that are comparable to or exceed tobacco smoke.

The study compared emissions from two tobacco cigarette brands sold in India and four herbal cigarette variants containing basil, clove, cinnamon, mint, green tea, water lily and chamomile. Two herbal variants used tendu leaves as wrappers, similar to those used in bidis.

The findings were published in the Journal of Hazardous Materials. The paper was co-authored by Alok Kumar Thakur and Sameer Patel from IIT Gandhinagar and P.S. Ganesh Subramanian and Vishal Verma from the University of Illinois Urbana-Champaign.

The research examined the physical, chemical and oxidative properties of mainstream smoke generated from herbal and tobacco cigarettes available in the Indian market.

Prof. Sameer Patel said, “Our findings challenge the widely held belief that tobacco-free means risk-free. Emissions from herbal cigarettes are comparable to or exceed those from tobacco cigarettes on nearly every metric we measured. Leaf-wrapped herbal variants turned out to be the most hazardous of all the samples tested.”

The study used a sealed automated two-chamber rig designed to simulate human inhalation. Smoke emissions were channelled into real-time instruments, while filter samples were collected for physical and chemical characterisation. Researchers also measured oxidative potential to assess the biological reactivity of emitted particles.

The researchers found that particles smaller than 500 nanometres were emitted at concentrations around 20 per cent higher in herbal cigarette smoke than in tobacco smoke. The study stated that such particles are associated with cardiovascular and respiratory diseases.

The research team also measured oxidative potential, which reflects the capacity of smoke particles to generate reactive oxygen species linked to inflammation, lung tissue remodelling and vascular changes associated with heart disease. Herbal cigarette particulate matter recorded higher oxidative potential than tobacco cigarette particulate matter.

Tendu leaf-wrapped herbal cigarette variants recorded oxidative potential around 49 per cent higher than paper-wrapped variants. Chemical analysis also found that one basil-filled herbal cigarette contained the highest lead concentration among the samples tested, despite being marketed as “chemical-free with 100% natural filler for a healthy lifestyle.”

Prof. Vishal Verma said, “That finding is important because many consumers associate nicotine-free products with reduced harm.”

The study also highlighted regulatory gaps surrounding herbal cigarettes. India’s Cigarettes and Other Tobacco Products Act, 2003 (COTPA) regulates tobacco products through warning labels, advertising restrictions and public smoking rules, while tobacco-free products may fall outside these provisions.

According to lead author Dr Alok Kumar Thakur, several herbal cigarette brands were marketed with claims related to cough relief, sleep improvement and anxiety reduction. “However, there is limited scientific evidence evaluating the emissions and toxicological impacts of these products,” he said.

Dr Thakur completed his PhD at IIT Gandhinagar under the Prime Minister Research Fellowship programme and is currently pursuing postdoctoral research at Colorado State University.

Dr P.S. Ganesh Subramanian said, “Combustion, fine particles, soot, trace metals, and the wrapper around them all matter more than what is written on the box.”

The findings were released around World No Tobacco Day on 31 May, whose theme this year is “Unmasking the appeal: countering nicotine and tobacco addiction”.

The researchers stated that herbal cigarettes marketed using wellness-oriented messaging may attract younger consumers and first-time smokers, and called for frameworks to regulate the marketing of tobacco alternatives.