Invisible toxins from plastic burning harm the lungs in more ways than imagined
The chemical composition and adverse health effects of particulate matter arising from plastic burning have been poorly understood till now. The IIT Madras study addresses this lacuna by demonstrating what the particles are made of and how these particles have a much greater impact on health
Open plastic burning is a widespread but often overlooked source of air pollution in India and many other parts of the world. In places where formal waste management is limited, such as urban slums, landfills, construction sites, and residential settlements, burning waste is frequently used as a quick solution to reduce volume. But this seemingly harmless practice releases invisible and harmful toxins into the air, posing a silent threat to human health.
While industrial emissions are monitored and regulated, these localised burn sites often escape attention. People living nearby breathe air that appears clear but carries a toxic mix of particles. A recent study conducted by us at the Indian Institute of Technology Madras and the University of California, Irvine, and now published in the journal Clean Air, shows that these emissions are far more hazardous than previously understood.
Studying the particles
To better understand what plastic burning actually releases into the air, we recreated the burning process in a controlled laboratory setting.
We burned five types of commonly used plastic materials — low-density polyethylene or LDPE (often used for plastic bags), high-density polyethylene or HDPE (often used for plastic bottles and containers), polyvinylchloride or PVC (often used for pipes and cables), polystyrene or PS (often used for disposable cutlery and food packaging) and polyethylene terephthalate or PET (often used for containers of liquids and foods) — under conditions that mimic real-world open burning and collected the particulate matter.
On burning, PET produced thick black smoke and the highest amount of particulate matter per mass of plastic burned, while LDPE and HDPE produced relatively low particulate matter per mass of plastic burned.
The particles collected were analysed using highly sensitive instruments. The aim was to identify the chemical components in the emissions and understand how they might affect human health when inhaled.
A toxic chemical cocktail
The emissions contained a range of harmful substances, including persistent free radicals — particles that remain chemically active for long periods and can generate reactive oxygen species (ROS) in the human body. When these ROS are inhaled, they can overwhelm the lungs’ natural defenses and lead to a condition known as oxidative stress. This, in turn, can trigger inflammation, allergies, respiratory illnesses, and even cancer.
The study also revealed high levels of redox-active metals such as copper, zinc, nickel and antimony. These metals contribute to even more radical formation, intensifying the toxic potential of the emissions. Additionally, polycyclic aromatic hydrocarbons (PAHs), some of which are known carcinogens, were also found in significant quantities.
Understanding the health impacts
To simulate how the human body responds to these particles, we used surrogate lung fluid in the lab. This helped us assess how much oxidative stress the particles could cause once they entered the lungs. The results were clear: plastics like PVC and polystyrene generated the highest levels of stress, making them particularly harmful.
In a surprising finding, we also detected reactive chlorine species, such as hypochlorous acid, a compound known to damage lung tissue. These chlorine-based radicals are rarely studied in air pollution research, making this one of the first studies to highlight their presence in plastic-burning emissions.
Most air quality monitoring focuses on how much particulate matter is in the air, and epidemiological studies have clearly linked the high concentrations of particulate matter to adverse health impacts such as asthma, allergies, respiratory and cardiovascular diseases, and premature death. However, the chemical composition and adverse health effects of particulate matter arising from plastic burning have been poorly understood till now.
Our study addressed this lacuna by demonstrating what the particles are made of and how these particles, especially the presence of free radicals and other compounds such as metals and organic species like polycyclic aromatic hydrocarbons (PAHs), have a much greater impact on health. An important insight from the study is that the chemical composition of particulate matter matters more than the quantity.
A public health wake-up call
These findings have urgent implications. People who live or work near open burning sites are often unaware of what they’re inhaling every day. The long-term health effects could be severe, especially in densely populated areas where exposure is frequent, and regulation is weak.
The study makes a strong case for banning open plastic burning, improving waste management systems, and increasing public awareness. It also calls for a shift in how we assess air pollution not just by measuring how much is in the air, but by understanding what’s in it and how it affects our bodies.
