The upsurge in the poor quality of air in Delhi on Tuesday, on the eve of Diwali, can be consequential for people who have respiratory and heart problems, increasing chances of heart attacks, if researchers are to be believed.

According to a recent study conducted by researchers in Utah in the US, poor-air-quality days can lead to an increased chance of heart attack for patients with heart diseases.

"Our research indicated that during poor-air-quality days, namely those with high levels of PM2.5, patients with heart disease are at a higher risk of suffering from a STEMI heart attack," said Kent Meredith, MD, cardiologist and researcher at the Intermountain Medical Centre Heart Institute.

Delhi's air pollution problem already poses health risks to citizens who can expect a reduced life expectancy by 3.2 years. On Diwali eve, with firecrackers exploding everywhere, Delhi saw an upsurge in the level of suspended particulate matter.

Areas in Delhi such as Anand Vihar crossed the safety limit of 100 micrograms per cubic metre by more than seven times, standing at 721 micrograms per cubic metre of suspended particulate matter i.e. PM 10, while PM levels ranged between 2.5-10 in residential areas like Mandir Marg, Punjabi Bagh, RK Puram, Pusa Road, Civil Lines, etc, the evening before the festival of lights.

According to the US study which examined 16,000 patients who had suffered three kinds of heart attacks – STEMI, non-STEMI and unstable angina -- from 1993 to 2014,  it was found that on bad-air-quality days, more cases of STEMI, the most severe kind of heart attack, had a greater chance of occurring.

"The study suggests that during many yellow-air-quality days, and all red-air-quality days, people with known coronary artery diseases may be safer if they limit their exposure to particulate matter in the air by exercising indoors, limiting their time outdoors, avoiding stressful activities, and remaining compliant with medications," said Dr Meredith.

In other words, the alarm bells are ringing for residents of the national capital with coronary problems. In Delhi, the System of Air Quality and Weather Forecasting and Research (SAFAR) project in-charge Gurfan Beig had said: "In all likelihood, air quality during Diwali this year is going to be inferior to that of Diwali-2014 owing to cooler temperature and downward shift of the inversion layer." 

The evening readings of the Delhi Pollution Control Committee and SAFAR stations on Tuesday categorised the air quality in Delhi between "poor" and "very poor".

The toxic air in Delhi is also the source of increasing cases of acute respiratory diseases, with the National Health Profile reporting 3.5 million cases the previous year.