Herbal cigarettes, widely sold in India and abroad as natural, tobacco-free, and even therapeutic alternatives to conventional cigarettes, are not safer than regular tobacco cigarettes. They produce emissions that can be comparably or even more damaging than tobacco smoke. That is the conclusion of a new study conducted by researchers at the Indian Institute of Technology Gandhinagar (IITGN), in collaboration with the University of Illinois Urbana-Champaign (UIUC).
The paper, published in the Journal of Hazardous Materials , presents a comprehensive comparison of the physical, chemical, and oxidative properties of mainstream (firsthand) smoke from commercially available herbal and tobacco cigarettes in the Indian market.
The study compared emissions from two of India's best-selling tobacco brands and four popular herbal varieties containing combinations of basil, clove, cinnamon, mint, green tea, water lily, and chamomile. Notably, two of the herbal brands utilised tendu (ebony) leaves as wrappers, identical to those used in bidis, India's most widely consumed smoking product.
To isolate the emissions, each cigarette was combusted inside a sealed, automated two-chamber rig designed to replicate human inhalation rate. The cigarette emission was funnelled into real-time instruments, and filter samples were collected for physical and chemical characterisation of particles. As a proxy for the potential toxicity of emissions, the oxidative potential of the collected samples was quantified.
"Our findings challenge the widely held belief that tobacco-free means risk-free," said Prof Sameer Patel, an Assistant Professor at IITGN's Department of Civil Engineering and Chemical Engineering, and co-coordinator of Dr Kiran C Patel Centre for Sustainable Development. "Emissions from herbal cigarettes are comparable to or exceeded 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."
A key finding was that sub-500-nanometer particles were emitted at approximately 20 per cent higher concentrations in herbal smoke than in tobacco smoke. These fine particles are increasingly linked to cardiovascular and respiratory disease.
The team also measured a property called oxidative potential (OP), which quantifies the smoke's capacity to generate reactive oxygen species, aggressive molecules that drive inflammation, lung tissue remodelling, and the vascular changes underlying heart disease. Particulate matter from herbal cigarettes recorded significantly higher OP than that from tobacco cigarettes. Tendu-leaf-wrapped variants, in particular, showed OP roughly 49 per cent higher than paper-wrapped versions. Interestingly, chemical analysis revealed one herbal cigarette, filled with basil, had the highest lead concentration, despite being marketed as "chemical-free with 100% natural filler for a healthy lifestyle."
"That finding is important because many consumers associate nicotine-free products with reduced harm," noted Prof Vishal Verma, research collaborator and an Associate Professor of Environmental Engineering in the Department of Civil and Environmental Engineering at UIUC.
The study also lays bare the regulatory gap problem 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, but products marketed as tobacco-free often fall outside these frameworks. Comparable regulatory gaps exist in several other countries.
According to lead author Dr Alok Kumar Thakur, several of the herbal cigarettes they tested were marketed with claims of relieving cough, improving sleep, or easing anxiety. "However, there is limited scientific evidence evaluating the emissions and toxicological impacts of these products." Dr Thakur completed his PhD at IITGN as a Prime Minister Research Fellow and is currently pursuing postdoctoral research at Colorado State University, USA.
The researchers emphasise that the study does not make direct epidemiological claims about disease outcomes. Instead, it focuses on measurable properties of the emitted smoke particles and their potential biological reactivity. "Combustion, fine particles, soot, trace metals, and the wrapper around them all matter more than what is written on the box," said Dr P S Ganesh Subramanian, currently a postdoctoral researcher at Washington University in St. Louis, USA.
The paper's findings coincide with the theme of World No Tobacco Day on May 31, "Unmasking the appeal: countering nicotine and tobacco addiction." With the herbal cigarette category potentially attracting younger consumers and first-time smokers using wellness-oriented language, there is an urgent need to develop frameworks to regulate the marketing of tobacco alternatives. This study adds to a growing body of scientific evidence that could help inform evidence-based regulation and public-health discussions around alternative smoking products.
