YADRAV, India – Farmworker Balaso Salokhe predicts the severity of his asthma by observing the sky around him. 

“In the past four years, my health has deteriorated so much that I avoid travelling outside my village,” he shares. During this time, he was hospitalised six times. Every time, the severity of his asthma worsened.

Salokhe, who described himself as “extremely fit” before his frequent asthma attacks, was determined to find out what had exacerbated his condition.

So he consulted with over 10 doctors and community health workers and, during the process, he found that air pollution was a key reason, traced to an increase in automobile industries and textile mills in his area. 

Salokhe is one of over 34 million people affected by asthma in India, a country that accounts for half the asthma deaths globally. In 2019, asthma affected 262 million people, causing 455,000 deaths, with India bearing a significant burden.

Asthma triggers

Smoking, allergies, respiratory infections, and air pollution can trigger asthma. Although the link between air pollution and asthma has long been established, studies have remained inconsistent about the effect of long-term PM2.5 exposure on asthma. 

These tiny particles, 30 times smaller than the width of a human hair, can penetrate deep into the lungs and even enter the bloodstream, causing a range of respiratory and cardiovascular issues. 

Long-term exposure to PM2.5 significantly increases asthma risk in children and adults, contributing to 30% of cases, according to a recent study published in One Earth involving over 25 million people from more than 20 countries. When PM2.5 levels increased by 10 micrograms per cubic meter, the risk of developing asthma rose by 21.4%, the study found.

Asthma was responsible for 21.6 million Disability Adjusted Life years in 2019, and rising air pollution can further exacerbate this. This can create a public healthcare crisis for countries like India, where the PM2.5 concentration was 11 times the World Health Organization’s (WHO) recommended safe level in 2023.

Lack of rural air pollution warnings

“Long-term exposure to PM2.5 has been associated with an increased risk of asthma through a variety of biological mechanisms like chronic inflammation, oxidative stress, immune dysregulation, exacerbation of allergic sensitisation, epigenetic modifications, and structural changes in the respiratory system,” said Yuming Guo, one of the One Earth study authors and an environmental health scientist at Australia’s Monash University. 

India’s average annual particulate pollution has increased by 68% from 1998 to 2021, which has reduced life expectancy by 2.3 years. 

 In November 2024, South Asia reported hazardous air quality. Multan in Pakistan crossed the 2,100 mark on the Air Quality Index (AQI), far exceeding the threshold of 301. The PM2.5 concentration was 947 micrograms per cubic meter, roughly 190 times above the WHO guideline. 

In 2019, ambient PM2.5 pollution from residential combustion, industrial emissions, and power generation caused over a million deaths in South Asia, according to a study published in Environmental Science & Technology. The study identified solid biofuel as the leading combustible fuel contributor to PM2.5-related mortality, followed by coal, oil, and gas.

India’s capital, New Delhi, reported an Air Quality Index exceeding 1,500 last November. This led to schools being shut and construction work halted. 

But 1,600 kilometres from Delhi, in Salokhe’s village of Yadrav in Maharashtra state, the problem was severe yet overlooked because of lack of monitoring.

Alongside industrial and vehicular air pollution around his village, another major source of air pollution is sugarcane farming, which burns thousands of kilograms of sugarcane leaves and tops every alternate day. 

With a tight schedule of harvesting and sowing and a lack of space for residue to decompose, burning is the easiest option for farmers. However,  burning pre-monsoon and post-monsoon crop residue contributed 28% and 64% respectively of the total PM2.5 emissions from burning activities in India, a 2022 study published in Nature found.

Researchers estimated 69,000 premature deaths annually across India caused by ambient PM2.5 exposure due to crop residue burning. 

Breathlessness

“During such times, I experience a lot of coughing and have to move to other parts of the village,” Salokhe said. His region has seen a proliferation in sugarcane production, which led to the establishment of even more nurseries, contributing heavily to air pollution.

Salokhe has also experienced severe breathlessness lately, particularly if he lifts anything heavy, and has stopped working in the field. 

His wife, Shanta, 66, said someone always needs to be around him as “he can get an asthma attack anytime.” 

In the last week of October, he experienced an acute attack and his sons rushed him to a hospital in the nearby town at midnight. 

“Had the treatment been delayed, the doctor warned, I might not have survived,” said Salokhe, who spent five days in the hospital.

His case isn’t an isolated incident. Another resident of the same village, Vasant Davade, 70, who worked as a farmworker, started suffering from asthma three years ago. His health has also deteriorated, and he had to quit farming a year after being diagnosed, taking away his livelihood and severely impacting the family. 

Limited research

Over the years, several studies have tried to unpack the complexity of long-term PM2.5 exposure and how it impacts asthma. However, research gaps remain.

 “While oxidative stress, inflammation, and immune dysregulation are recognized, the specific molecular and cellular mechanisms linking PM2.5 exposure to asthma development and exacerbation remain unclear,” said Guo. 

There is limited research on how genetic predispositions, such as polymorphisms in inflammation or antioxidant genes, interact with PM2.5 exposure to influence asthma risk, he added.

“More studies are needed to explore how long-term PM2.5 exposure induces epigenetic changes that affect asthma-related gene expression.”

A major challenge is that PM2.5 is a complex mixture of several pollutants, making it difficult to identify which components remain most harmful to asthma. 

Another challenge is the meagre amount of studies on low-income populations, racial and ethnic minorities, and the ones from low-and-middle-income countries. 

“The relationship between PM2.5 and asthma in rural settings, where pollutant sources and compositions may differ from urban areas, remains underexplored,” added Guo. What complicates the research further is a poor understanding of the impact of climate change on PM2.5 levels and composition and how it influences asthma risk. 

Lack of affordable solutions

Mitigating asthma risks from PM2.5 exposures requires interventions at several levels. 

Guo suggests using high-efficiency particulate air (HEPA) filters in homes and schools to reduce indoor PM2.5 levels. He also advocates avoiding the use of wood stoves, open fires, or unvented heaters indoors, wearing masks with high filtration efficiency during high pollution episodes, minimising outdoor activities during times of high air pollution, and calls for proper asthma management, ensuring people have access to inhalers. 

However, Salokhe said he did not wear a mask because he had no way to track pollution in the village. Without sensors and real-time data, many people can’t make the right decisions about stepping out or avoiding polluted areas. 

“I simply look at the sky to gauge the black smog. That’s my only way of understanding air pollution,” he said.

Many people can’t afford cleaner energy sources, forcing them to rely on burning firewood, plastic seedling trays, and whatever is available to cook food and heat water for bathing. 

“We even use a traditional stove as we can’t afford frequently refilling LPG (Liquefied Petroleum Gas) cylinder,” shares Shanta. “Almost all the village residents burn firewood daily to heat water.”

She burns firewood for an hour every morning, which has also started affecting her health. “How can you escape that air pollution, and who will stop it when people are burning so many things in and around their households?” she asks.

With the lack of affordable solutions and things beyond his control, Salokhe said his health has been declining quickly: “Anytime my lungs can give up, and that will be my last breath,” he said, looking sadly at his five-decades-old bicycle that he can no longer ride. 

Image Credits: Sanket Jain.