While no statistics are available in Mumbai to directly correlate air pollutants with heart attacks, there is growing evidence in the West and some data from India as well. For instance, the World Health Organisation's Global Diseases Burden statistics showed that 6.2 lakh people had died prematurely in India from air pollution-related diseases in 2010. More than half of these deaths were triggered by heart attacks. It is believed that air pollutants, especially microscopic particulate matter, enter the airways easily and irritate the blood vessels as well. It is now well-established these pollutants lead to inflammation of blood vessels that, over a period of time and prolonged exposure, could worsen a patient's existing heart diseases (such as building up of plaque in arteries).

In fact, doctors in Mumbai believe it is time to tweak the risk factors associated with heart diseases. It has traditionally been held that heart diseases among Indians are the result of familial history or habits such as smoking or consuming calorie-rich foods. "It is time we not only asked patients who come in with heart problems about their smoking and family history, but also about the air pollution around them,'' said Dr A B Mehta, director of cardiology at Jaslok Hospital on Pedder Road.

In March 2014, WHO reported that one in eight of total global deaths in 2012 resulted from air pollution exposure. This finding doubled previous estimates and confirmed that

air pollution was the world's largest single environmental health risk. "Reducing air pollution could save millions of live,'' said the WHO report.

The American Heart Association had in 2009 brought out statements linking air pollutants, especially the microscopic particulate matter (both PM2.5 and PM 10), with worsening of existing heart disease. "A study on emergency admissions in Boston reported a significant association of NO2 (nitrogen dioxide) and PM2.5 with the risk of acute myocardial infarction,'' said a large review of studies that appeared in Toxicology Research medical journal this year.

It talked about a study conducted across 21 US cities that reported an association between NO2 and PM10 exposure and risk for hospitalization. "This Intermountain Heart Collaborative Study revealed a 4.5% increase in coronary artery disease with every 10 ig/m3 (microgram) increase in PM2.5,'' said the review.

"Given the new evidence relating air pollution and heart attacks, it is easy to surmise that air pollutants shorten people's lifespan,'' said Dr Mehta, adding "Dr S R Kamath, who headed KEM Hospital's chest medicine department, used to tell me long back that living in the Lalbaug area can reduce one's lifespan by a decade''.

Cardiologist Dr Brian Pinto said, "While there are no research papers linking air pollution and heart attacks in India, there is no question in my mind that it affects the heart. If smog affects one's lungs, how can it not affect the heart as well?'' He said air pollutants-heart link is the reason that people are advised not to jog or exercise early in winter mornings.