India’s first systematic assessment of inhalable microplastics has found that tiny airborne particles from synthetic fibres and plastics can transport toxic contaminants and disease-causing microbes that could reach the lungs.
Scientists at the Indian Institute of Science Education and Research (IISER) in Calcutta, who analysed air samples from marketplaces in Calcutta, Chennai, Delhi and Mumbai, have documented bacterial and fungal species as well as lead, arsenic and chromium on the surfaces of airborne microplastics.
Their study has found average concentrations of about 14 micrograms inhalable microplastics per cubic metre of air in Calcutta and Delhi and below five micrograms per cubic metre in Chennai and Mumbai, flagging concerns about a hitherto overlooked air pollutant.
At a typical breathing rate of about 14 breaths per minute, a person exposed for eight hours per day to these concentrations would inhale 370 particles daily in Calcutta, 300 in Delhi, 190 in Chennai and 160 in Mumbai, their calculations suggest.
Electron microscope images pointed to several bacterial and disease-causing fungal species adhering to the surfaces of the microplastics, the IISER researchers said, describing their findings in the journal Environment International.
“Airborne microplastics can act as Trojan horses with microbes and other hazardous contaminants,” Gopala Krishna Darbha, an associate professor of earth sciences at IISER Calcutta, and his colleagues wrote in their study. “Their rough surfaces provide ideal habitats for microbes.”
Darbha, research scholar Abhishek Biswas and collaborators analysed air samples from New Market, Burrabazar, Hatibagan, Gariahat and Sealdah in Calcutta; Connaught Place, Nehru Place and Sarojini Market in Delhi; and comparable marketplaces in Chennai and Mumbai.
Darbha and the others found that polyester fibres shed from clothing were the most abundant component of inhalable microplastics, followed by particles from single-use packaging and vehicle emissions.
Chemical analysis revealed heavy metals adhered to these particles. Among a set of 10 inhalable microplastics sampled in Calcutta, seven contained lead, five chromium and four arsenic.
Toxicology experts have long emphasised that lead has no role in the human body, and exposure raises the risk of endocrine, respiratory and other health disorders.
Crowded urban markets linked by open sewage drains can accumulate household microplastics. These particles degrade, retain nutrients and create surface conditions favourable for microbial growth and cross-contamination, the researchers said.
Winter evenings showed the highest levels of airborne microplastics in markets, linked to heavy footfalls, widespread synthetic apparel and poor waste handling.
The share of inhalable microplastics within particulate matter measuring 10 microns (PM10) ranged from 0.2 per cent to 5.6 per cent, depending on the site.
“These measurements of inhalable microplastics are timely and relevant,” Nilabja Sikdar, a human geneticist at the Indian Statistical Institute in Calcutta, who was not associated withthe IISER study, told The Telegraph. “There is strong evidence linking microplastics with several cancer tissues — including the breast, lungs, colon and prostate — where they trigger inflammatory processes.”
