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On successive weekends in November, hundreds of Delhi residents gathered at India Gate holding placards saying “I miss breathing” and “right to live, not just survive”. Winter’s onset once again plunged the National Capital Region into a dense smog, with the air quality index refusing to exit the ‘severe’ (301-400) or ‘very poor’ (201-300) levels.
Even now, regulators are scrambling to enforce graded action plans to mitigate the concentration of PM2.5 and PM10 particles in the air.
Into this toxic mix, new research has added a previously overlooked problem called inhalable microplastics. According to scientists, they pose a direct and alarming risk to human health.
Atmospheric pollution has traditionally been associated with the so-called criteria pollutants; aside from the two size-wise groups of particulate matter, these include carbon monoxide, lead, sulphur oxides, nitrogen oxides, and ozone. Of late however they’ve been joined by respirable emerging contaminants — including inhalable microplastics — fuelled in no small part by the production of 400 million metric tonnes of plastics every year. The world also releases 52.1 million tonnes a year of plastic waste into the environment.
A first-of-its-kind comprehensive study published in Environment International in November examined inhalable microplastics in India. These are plastic particles smaller than 10 micrometres (µm). The researchers, led by Indian Institute of Science Education and Research Kolkata professor Gopala Krishna Darbha, monitored ambient concentrations at human breathing height (1.5 m) in five highly populated markets in Delhi, Mumbai, Kolkata, and Chennai.
Thus the team estimated the average concentration of inhalable microplastics in all four cities to be 8.8 µg/m3.
This “means the average city resident is breathing in about 132 micrograms every single day,” Dr. Darbha said. “This is a very high daily dose of pollution. The most critical factor is the size of these particles. They are so tiny that they can bypass our natural defenses and penetrate deep into the lungs. This chronic exposure presents a serious, ongoing risk to public health.”
Researchers, however, said that the greater danger is these plastic particles serving as Trojan horses that smuggle in toxic co-pollutants, including heavy metals like lead and cadmium and hormone-disrupting chemical compounds like diethyl phthalates. The team found atmospheric lead levels to be highest in Kolkata, followed by Delhi.
The team members also found, reportedly for the first time, that the inhalable microplastics plastics can also carry microbes, including harmful fungi like Aspergillus fumigatus, that contain antibiotic-resistance genes, meaning they could spread infections that don’t respond to common antibiotics.
By comparing this information with major toxicology databases, the team found that breathing these contaminated plastic particles was associated with a higher risk of cancer, hormone-related diseases, breast problems, and respiratory illnesses.
Time and place
In all four cities, winter evenings had a mean inhalable microplastic concentration of 32.7 particles/m3 while non-winter evenings averaged 18.8 particles/m3, reflecting a 74% seasonal increase during winter.
There was a significant inter-city variation as well: the data revealed that the residents of Delhi and Kolkata were exposed to high concentrations of inhalable microplastics — 14.18 µg/m3 and 14.23 µg/m3 respectively — whereas Mumbai (2.65 µg/m3) and Chennai (4 µg/m3) fared much better.
“The major factors that are coming here are meteorological conditions,” Dr. Darbha said alluding to Mumbai and Chennai being coastal cities. “Second is urban population density, and third one is waste mismanagement.”
Zeroing in on the particles themselves, the researchers identified 11 kinds of plastics in the air, most of them coming from places the researchers said people usually overlook.
“The particles were primarily less than 100 µm in size (56.2%), followed by 100–500 µm (24.7%) and over 500 µm (19.1%). Fragments were more common than filaments,” the team wrote in its paper.
“Larger filament-shaped airborne microplastics typically … originate from synthetic textiles or toy fillings. Smaller fragments, often secondary airborne microplastics, arise from packaging, tire wear, household release, cosmetics, mini- and micro-industries, construction, [and] were more prevalent due to their small size and weathering, particularly in areas like Sealdah Market and Chandni Chowk.”
Policy imperative
According to Dr. Darbha, the current air quality index may capture “a certain percentage of nanoplastics” but describes the existing evidence as “too preliminary” to correlate AQI values with inhalable microplastics. He did say workers such as traffic police and labourers are especially vulnerable, since “tire-wear particles seem to be more carcinogenic or they may cause severe threat to their lungs. Policy reform is needed to protect such vulnerable groups.”
The study also said the particles persist in the air due to low gravitational settling velocity.
“The government should ban single use plastic and many such polymers,” he said, adding that cotton-based clothing is preferable to synthetics and that “recycled and refurbished polyester or reused fabrics … are capable of releasing these tiny plastics.”
He also said uncontrolled waste disposal, improper waste segregation, and burning emitted poisonous gases and smaller particulate matter, some of which could piggyback on the inhalable microplastic particles into our lungs.
Overall Dr. Darbha said the study provides a new baseline for an emerging environmental crisis: “This is a starting point, and we are definitely looking forward to more results coming up in the country, to have more knowledge-sharing in the … scientific community as well as among the common public to have more awareness.”
Against the backdrop of the accumulating evidence of the persistence and harms of microplastic and nanoplastic pollution, the researchers also expressed hope that the Indian government would take serious measures regarding plastic disposal and worsening air quality.
Neelanjana Rai is a freelance journalist who writes about indigenous community, environment, science and health.
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