A few months ago, a 55-year-old woman from a busy city consulted me about her brain stroke, which had occurred a couple of weeks earlier. Despite maintaining a reasonably healthy lifestyle and having no significant risk factors for a stroke, such as high blood pressure, diabetes, or a family history of stroke, she faced a critical risk factor that neither she nor her family had considered: Long-term exposure to air pollution.

Living in a highly polluted area, her daily exposure to fine particulate matter (PM2.5) had silently and progressively compromised her health. She wasn't alone. In India, thousands of people—especially women, older people, and children- face a similar, invisible threat. We must bring attention to this growing risk. The connection between air pollution and stroke is becoming increasingly evident through research and clinical experiences. In 2021, 99% of the world's population lived in areas that did not meet the World Health Organization (WHO)'s strict air quality guidelines. WHO also states that air pollution accounts for 24% of all stroke deaths globally.

A few months ago, a 55-year-old woman from a busy city consulted me about her brain stroke, which had occurred a couple of weeks earlier. Despite maintaining a reasonably healthy lifestyle and having no significant risk factors for a stroke, such as high blood pressure, diabetes, or a family history of stroke, she faced a critical risk factor that neither she nor her family had considered: Long-term exposure to air pollution.

Living in a highly polluted area, her daily exposure to fine particulate matter (PM2.5) had silently and progressively compromised her health. She wasn't alone. In India, thousands of people—especially women, older people, and children- face a similar, invisible threat. We must bring attention to this growing risk. The connection between air pollution and stroke is becoming increasingly evident through research and clinical experiences. In 2021, 99% of the world's population lived in areas that did not meet the World Health Organization (WHO)'s strict air quality guidelines. WHO also states that air pollution accounts for 24% of all stroke deaths globally.

Stroke, already a leading cause of death and disability worldwide, is worsened by exposure to polluted air, particularly in countries like India, where air quality is poor in both urban and rural areas. At the heart of this crisis are particulate matter (PM), especially PM2.5, which refers to particles that are small enough to enter the lungs and bloodstream.

What is particulate matter (PM)? PM is a mixture of many chemicals. The larger (<10 µm in size, PM10) particles are from industrial emissions, and the smaller (<2·5 µm in size, PM2.5) particles are from traffic emissions. For understanding, both PM10 and PM2.5 are less than the size of the human hair (50-70 µm). While all particulate matter (PM) sizes are harmful, particles <2·5 µm can penetrate deep into the lungs, interact with the body's defences, or enter the bloodstream. In my patient's case, prolonged exposure to these particles had led to inflammation, higher blood pressure, and gradual narrowing of her blood vessels. These conditions significantly heightened her risk of experiencing a stroke. A study published in The Lancet in 2021 found that for every 10µg/m3 increase in PM2.5, the risk of stroke rises by 13%. This statistic is alarming, given that air pollution levels in many Indian cities consistently exceed safe limits.

In India, this issue is particularly acute. The State of Global Air Report revealed that in 2019, over 1.67 million deaths in India were linked to air pollution, many of which were stroke-related. Cities like New Delhi, Kanpur, and Ghaziabad frequently rank among the most polluted in the world, and the effects of this pollution are evident in the rising number of stroke cases. India has recognised the seriousness of air pollution through initiatives like the National Clean Air Programme (NCAP), aiming to reduce PM2.5 concentrations by 20–30% by 2024 in over 100 cities. However, aligning these environmental efforts with public health strategies remains crucial to reduce pollution-related strokes effectively.

This challenge is not limited to large cities; rural areas, where indoor air pollution from cooking fuels is prevalent, also see a heightened risk of stroke, particularly among women who spend extended hours in poorly ventilated, smoke-filled kitchens.

Take, for example, the case of another patient from a rural village in northern India who used biomass fuels for cooking throughout her life and suffered a stroke in her early 50s. The toxic smoke from burning wood and cow dung gradually harmed her cardiovascular health, making her more susceptible to stroke. Despite leading an otherwise healthy life, the polluted indoor air gradually damaged her arteries-an invisible threat she recognised only after her stroke. Indoor air pollution affects women, pregnant individuals, children, and the elderly. Studies show that pregnant women exposed to high levels of pollution are at greater risk for hypertension, which can lead to pregnancy-related strokes. Additionally, cooking fuels in poorly ventilated rural homes increase risks for women who spend hours in those environments.

To address this silent crisis, several steps must be taken. The first step is to increase awareness about this critical health risk. Many people, like my patients, are unaware that the air they breathe can significantly increase their risk of a stroke. Public health campaigns should emphasise the link between air quality and stroke risk, focusing on urban areas with high pollution levels and rural areas where indoor air pollution is a significant concern. Recognising that air pollution is a modifiable environmental risk factor for stroke gives us a powerful opportunity to intervene at multiple levels-individual, community, and policy.

· Reduce vehicle emissions by promoting cycling, public transportation, car-pooling, electric vehicles and regular vehicle check-ups.

· Stay indoors during high-pollutant events and avoid exercising in areas with high pollutants

· Select transportation routes to avoid high-pollutant zones and avoid travel during high-traffic times.

· Avoid using wood or coal stoves and use cleaner fuels like LPG for cooking.

· Control industrial pollution by stricter regulation

· Enforce strict anti-smoking laws in public places

· Conduct regular air quality monitoring and implement immediate corrective actions whenever pollution levels rise

While governments and institutions have a crucial role, we must also take personal responsibility for our health and the environment. By acknowledging our responsibility, we become part of the solution to environmental degradation and the fight against stroke. It's important to understand that combating stroke involves more than just managing traditional risk factors like hypertension and diabetes. Simple behavioural changes—like checking daily air quality indices, avoiding outdoor activity during high pollution, and advocating for cleaner community practices—can substantially reduce health risks.

Environmental factors, especially air pollution, are increasingly threatening the health of millions. Let us each pledge to make a change for our health, for the planet, and future generations. Protecting ourselves from air pollution is no longer optional; it is an urgent public health necessity.

This article is authored by Dr K Madan Gopal, advisor and head of the public Health administration division, National Health Systems Resource Centre (NHSRC), ministry of health and family welfare, New Delhi and Bindu Menon, founder, Dr Bindu Menon Foundation, Nellore.