New Delhi: For some weeks every fall, the Air Quality Index in most Indian cities hits ‘severe’ and with it surges our level of panic. Volumes of writings and hours of air time are dedicated to the ill-effects of polluted air.
However, scientists say the panic is misplaced as there is no safe threshold for air pollution. A study published in the British Medical Journal this week reiterates that just fixating on higher levels of air pollution does not work. Continuous exposure to even low or moderate levels of air pollution causes blood vessel damage.
“There is a continuous relationship between air pollution and risk of heart attacks. Constant and continuous exposure to low level of air pollution can also cause damage to blood vessels and increase the risk of heart attacks,” says Dr Srinath Reddy, Senior Cardiologist and Founder of Public Health Foundation of India (PHFI).
The study
The study published in British Medical Journal says there is a continuous relationship between polluted air and heart health. It doesn't matter whether the exposure is limited to a few days of severe pollution levels or continuous exposure to lower levels of air pollution over a period of time. Benefits can only be achieved if we adhere to WHO guidelines for air quality.
The research titled ‘Exposure-response associations between chronic exposure to fine particulate matter and risks of hospital admission for major cardiovascular diseases: population based cohort study’ showed that chronic exposure to fine-sized particulate matter PM 2.5 increases the risk of cardiovascular disease and there is no safe threshold.
Cardiac arrhythmia and heart failure are among the most vulnerable conditions found in patients exposed to PM2.5. Cardiac arrhythmia is a condition where the heart beats with irregular or abnormal rhythm. The researchers further say adhering to the WHO's air quality standards of ≤5 µg/m3 can provide considerable advantages.
What is PM or SPM 2.5 ?
Particulate matter with an aerodynamic diameter of ≤2.5 µm (PM2.5) is a major component of ambient air pollution, something we have known for decades now.
also know these particles are small enough to be inhaled deeply into the lungs, and they can enter the bloodstream, leading to a range of health problems such as systemic inflammation, vasoconstriction, cardiac electrical changes, and formation of blood clots, all of which can contribute to the development of cardiovascular disease (CVD).
These particulate matters have in fact been called the major environmental risk factor for cardiac diseases. These two studies have found that exposure to PM2.5 can trigger adverse cardiovascular conditions and increase the risk of cardiovascular related hospital admission and mortality.
In layman terms
Dr Reddy says people are comfortable if the AQI is between 100 to 150 and presume these are safe levels. “We often hear people say AQI is higher. It’s going to be terrible for your health. Panic sets in when the AQI levels reach 400 plus. We often presume AQI of 100 to 150 is safe. But that is not the case,'' he says.
“This study shows that even a lower level of exposure to air pollution triggers an inflammatory response. It is like a dose response relationship. An exposure to increased levels of pollution increases the damage to heart vessels and heart. But the cumulative time period of exposure also matters. If we have a moderate or relatively low level of exposure going on for six or eight months a year, it is going to be a constant irritation to the blood vessels and can increase the risk of heart attacks and strokes,'' Dr Reddy explains.
He says in acute exposure of 600 or 700 AQI for one or two days, heart attacks risk increases as unstable plaques can get destabilised and one can get an acute clot and heart attack. “But the constant damage to blood vessels is more likely to occur, even at very modest levels of exposure going on for a long time and trigger a similar reaction.”
“For example high blood pressure is defined by 140/90 but that doesn't mean 130/85 doesn't carry a risk.” Dr Reddy says other conditions also matter. “If you already have diabetes or high blood pressure, even moderate levels of air pollution can be more damaging,” he says.
What the study adds
No safe threshold exists for air pollution and overall cardiovascular health, and substantial benefits could be attained through adherence to the World Health Organization’s air quality guideline.
The idea here is don't be fixated on only higher levels of air pollution, even lower levels of air pollution can cause blood damage and hence heart attacks. The only thing we can do is bring down the air pollution levels as low as possible. Fine particulate matter (PM2.5) is a key air pollutant and is recognized as a primary environmental risk factor for cardiovascular disease (CVD)
Chronic exposures to PM2.5, lasting one year or more, pose a much greater risk to cardiovascular health than short term exposures spanning only a few days.
Dr Reddy suggests
1. There has to be a general policy and public systems response where we have to reduce the levels of exposure to everybody.
2. There is also an individual's response which is to limit your exposure to polluted air.
3. Move out only when the weather is a little clearer, when the air is not smoky.
4. Use masks when you are moving out.
5. Try to avoid highly polluted areas. Move around in well ventilated places where particles don't stick around as particle clouds. In well ventilated places the air flow is good.
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