Microplastics laden with toxins and pathogens fill India’s marketplace air

The air in India’s crowded marketplaces carries more than just the scent of street food and traffic fumes. It is also laced with invisible plastic particles — small enough to breathe, laden with toxic chemicals and microbes — that could pose a mounting threat to public health.

A new study¹ by researchers at the Indian Institute of Science Education and Research (IISER) Kolkata and The Institute of Mathematical Sciences (IMSc) in Chennai has found high levels of inhalable microplastics (iMPs) — particles smaller than 10 micrometres — suspended in the air of major Indian cities. These tiny pollutants, the researchers say, may accumulate up to three grams in human lungs over a lifetime.

“iMPs are a consistent fraction of both PM10 and PM2.5 samples — they must now be recognised as a new class of respirable air pollutants with implications for public health and atmospheric chemistry,” said Gopal Krishna Darbha, who led the study at IISER Kolkata.

Plastic in the air

The team sampled outdoor air in Kolkata, Delhi, Chennai and Mumbai during the winter of 2022–23, collecting filter papers placed at breathing height in busy markets. Kolkata and Delhi recorded the highest concentrations — around 14 micrograms per cubic metre — while coastal cities such as Chennai and Mumbai showed lower levels, due to sea breezes that help disperse particles.

On average, the study estimated that a person spending time in these markets inhales about 114 micrograms of microplastics each day, roughly 2.6% of the total particulate matter in the air. Though that may sound small, these particles dominate the number of airborne pollutants, thanks to their lightness, persistence, and electrostatic properties that keep them suspended longer.

“Unlike mineral dust, microplastics are lighter and can remain airborne for longer periods, allowing them to travel greater distances,” Darbha said.

The researchers identified 11 types of polymers in the samples using advanced chemical analysis. Polyester from clothing was most common, followed by polyethylene and synthetic rubber from packaging, footwear, and tire wear — pointing to textile waste and packaging as key sources. “In winter, when synthetic clothing is common, more microplastics slough off,” said Jawed Iqbal, an air pollution modeller at BIT Mesra, who was not involved in the study.

Trojan horses for toxins

What most alarmed scientists was not just the plastics themselves, but what they carry. The researchers found that iMPs were coated with 28 toxic chemicals — including five carcinogens such as benzene and styrene, and nine endocrine-disrupting compounds like diethyl phthalate and bis(2-ethylhexyl) phthalate, which can affect fertility and hormone balance.

“A single microplastic particle can simultaneously dump carcinogens, reproductive toxins, irritants, and neurotoxins directly into the lungs,” said Areejit Samal, co-author at IMSc.

This “Trojan horse effect” — where microplastics act as delivery platforms for toxic additives and absorbed pollutants — makes them particularly dangerous. “Lead and phthalates embedded within plastics are released slowly once inside the body,” said Jeroen Sonke, a microplastics researcher at the CNRS Geoscience and Environment Laboratory in France. “And airborne plastics can also absorb additional pollutants before they are inhaled.”

The study also uncovered traces of heavy metals and volatile compounds that damage the nervous system, such as toluene and pyridine derivatives. These chemicals are known irritants of the skin, eyes, and respiratory tract and are regulated in many countries — but India currently lacks monitoring protocols for airborne microplastics or their associated toxins.

Carriers of microbes

The study detected microbial colonisation on these airborne plastics. During Kolkata’s autumn festival season, researchers found six bacterial strains — including a potentially novel Paenibacillus species — carrying antibiotic resistance genes, as well as 22 fungal taxa such as Aspergillus fumigatus and Candida auris, both known to cause respiratory infections.

These findings suggest that microplastics could also serve as vectors for pathogens, further complicating their health impact. “The combination of persistent plastic, toxic chemicals, and live microbes makes this a truly multipronged hazard,” Darbha said.

A regional and global threat

Microplastics are now recognised as part of a global atmospheric cycle, drifting across continents and oceans. Using NOAA’s HYSPLIT model, the Indian team showed that particles from Delhi can disperse across northern India and into Bangladesh and Assam, while emissions from Mumbai, Chennai and Kolkata can reach the Bay of Bengal, the Arabian Sea and the Indian Ocean — and eventually re-enter the food chain through seafood.

Sonke’s research² in 2021 found evidence of similar plastic transport from urban regions into the Arctic atmosphere. “Microplastics behave like any other aerosol — they move with the winds,” he said. “What we release locally doesn’t stay local.”

Policy gaps and possible fixes

The study’s authors call for targeted interventions to reduce exposure in public markets, such as improving ventilation, promoting natural-fibre clothing, restricting heavy-vehicle access, and encouraging chemical recycling of weathered plastic waste.

But experts say that broader change will depend on better monitoring and coordinated global policy. “Microplastic analysis is still laborious and time-consuming,” Sonke said. “But a major effort is underway to standardise measurement techniques so that government labs and industry can perform reliable monitoring within the next three to five years.”

That timeline aligns with renewed hopes for the stalled United Nations Plastic Treaty, which seeks to curb global plastic pollution. “The treaty process needs to resume and adopt majority voting, rather than consensus, if we’re serious about cutting emissions and exposure,” Sonke said.

He adds that India’s public transport and waste management systems could play an unexpected role in reducing both microplastic and carbon emissions. “Every small improvement in urban design and mobility has co-benefits for air quality and health,” he said.