Ammonium Sulphate Emerges as Deadliest PM2.5 Pollutant in Delhi Air, Harvard Study Warns of Severe Lung and Heart Risks

Delhi’s

air pollution problem is often discussed in terms of PM2.5 levels, but new research shows that the composition of this pollution may be just as important as its quantity. Recent analysis by the Centre for Research on Energy and Clean Air (CREA) has found that nearly one-third of Delhi’s annual PM2.5 pollution is made up of secondary ammonium sulphate, a pollutant now linked to serious respiratory and heart-related health risks.Health researchers warn that ammonium sulphate can be more harmful than overall PM2.5. 5 measurements suggest, that how strongly it affects the lungs and cardiovascular system.

What Is Ammonium Sulphate?

Ammonium sulphate isn’t something that comes straight out of a factory smokestack or a car’s exhaust. It actually forms in the air when sulphur dioxide mixes with ammonia. Most of the sulphur dioxide comes from burning coal, running factories, or traffic, while ammonia usually drifts in from farms, waste, or city life.After it forms, ammonium sulphate turns into a component of PM2.5—those super fine particles that float around in the air. They’re so tiny, they slip deep into your lungs and can even end up in your blood. That’s what makes them so risky for your health.

Strong Connection to Asthma

A 2025 study led by researchers at Harvard T.H. Researchers at the Chan School of Public Health found that sulphate particles—like ammonium sulphate—play a big role in sending people with asthma to the hospital. When pollution with lots of sulphate in it went up, so did asthma hospitalisations. Kids were especially affected.What’s interesting is that the study showed sulphate particles have a stronger connection to asthma risk than many other parts of PM2.5. So, it’s clear: not every bit of air pollution hits our health the same way.

Impact on Heart Health

It’s not just our lungs at risk. Back in December 2024, Nature Communications published a study digging into how different bits of PM2.5—a kind of tiny air pollution—actually hit your heart, not just your lungs. They looked at the risk for things like heart attacks, and the results were pretty eye-opening.Sulphate particles stood out. The researchers found that these had a stronger link to sudden heart problems than just the overall PM2.5 levels did. Even a small uptick in sulphate pollution could seriously hike up the odds of heart trouble. So, ammonium sulphate pollution is looking especially dangerous, especially for people living in cities where bad air is just part of daily life.

What’s happening in Delhi?

Doctors are seeing more and more people come in with breathing problems, stuffy noses, constant colds, and weaker lungs. This is happening even to folks who’ve never had breathing issues before. Over the past ten years, as the air has gotten worse, these symptoms have just kept climbing.While individual protective steps, such as wearing masks or using air purifiers, can lower exposure, these options are not affordable or accessible for much of the population. This makes the health impact of air pollution more widespread and harder to control at a personal level.With ammonium sulphate now identified as a major and highly harmful part of Delhi’s air pollution, researchers stress the need to reduce sulphur dioxide and ammonia emissions at their sources. Addressing air pollution requires coordinated, large-scale action rather than small, isolated measures.