Here’s why you should be worried about the rising ozone pollution
Summer is here. This is the time when two major outdoor pollutants — suspended fine particulate matter (PM2·5) and ozone — become our worst enemies. You should be worried, very worried. Here’s why.health and fitness Updated: Feb 27, 2017 07:54 IST
Toxic airborne contaminants and noxious gasses that constitute polluted air are steadily growing each day, but the concentrations of some vary with the weather and the time of day. Summer is the period when overwhelming level of two major outdoor pollutants — suspended fine particulate matter (PM2·5) and ozone — become threat to people in India, China, Pakistan and Bangladesh, where the deadliest concentrations of PM2·5 (>75 μg/m3) are found, warns The State of Global Air 2017 report, released last week.
For South Asians particularly, hot summer brings with it lungfuls of dangerous ozone, levels of which are the highest in hot sunny weather between March to June.
Ozone is a unique gas because it protects and hurts you depending on whether your breathing it in or not. This colourless, odourless gas is beneficial for us in the higher stratosphere level because it blocks the sun’s harmful ultraviolet rays from reaching the earth’s surface and reduces our risk of skin cancer. Greenhouse gases such as CFCs (chlorofluorocarbons) destroy ozone molecules in the stratosphere and, over time, have led to the creation of a giant ozone hole in the Southern Hemisphere over Antarctica, which is an ever-growing concern.
Trouble on the ground
The ozone that threatens us across south Asia all through summer is found on earth’s surface level, which is deadly. It is formed when two air pollutants volatile organic compounds (VOCs) from products such as solvents and paints and oxides of nitrogen (NOx) from emissions from vehicles, industries, power plants react in sunlight. When inhaled, ozone causes airway and lung irritation, making you cough and wheeze. Over time, it aggravates breathing disorders and causes permanent lung damage.
At ground level, exposure even for a short duration can harm health, which is why standards for ozone are set for one-hour and eight-hour durations. India’s national ambient safe standard for ozone is 100 μg/m3 (microgram/ cubic metre) for eight-hour average and 180 μg/m3 for one-hour average, yet values in many parts of India routinely cross 200μg/m3 during hot, summer afternoons.
In Delhi, for example, ozone peaks rose to 250 μg/m3 in April and May in 2015, with 92% days in April and 97% in May exceeding 100 μg/m3, showed a Centre for Science and Environment analysis.
How ozone hurts health
Ozone makes the inner lining of the airways raw and inflamed, making them constrict to cause wheezing and breathing difficulty. It aggravates lung diseases such as asthma, emphysema, chronic bronchitis and chronic obstructive pulmonary disease (COPD). Ozone also accelerates the rate at which our lungs age, making young people start wheezing like chronic smokers do after a lifetime of smoking.
Exposing healthy young people to as little as 0.3-ppm ozone for two hours while intermittently exercising lowered lung function and raised risk of lung and heart damage by pushing up vascular markers of inflammation and autonomic control of heart rate, reported a study in the journal Circulation. Temporary loss of lung function and breathing trouble in healthy people begin at concentrations as low as 0.12 ppm, but these changes are reversible.
Away Airway lung inflammation makes you more sensitive to allergens, which makes ozone among the most common triggers of asthma attacks. Since people with asthma have trouble breathing, raw and swollen airways and lungs further restricts breathing and further reduces lung function. People with asthma, irrespective of whether their sensitivity is to dust, pollen, smog or some other allergen, must be prepared to control unexpected attacks in hot summer months.
Who’s at most risk
Inhaling ozone also makes the lungs more susceptible to infection, which puts young children, people who are physically active during the day, persons over 65 years and people with chronic lung diseases at frequent risk of infection, leading to overmedication, frequent visits to doctors and hospital admissions.
Children are at greatest risk because their airways are narrower and their lungs are still developing. Children, including teenagers, inhale more air per kg of body weight compared adults and are more likely to be active outdoors during the day when ozone levels are high, which increases the amount of ozone and other pollutants they end up inhaling.
Since ground-level ozone forms usually on hot summer days, it’s levels are highest in the afternoon and early evening. Make sure you step outdoors in summer early in the morning or late in the evening. Children must avoid playing outdoor sports during the day. An added plus of these precautions is that they lower the risk of dehydration and heatstroke.
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First Published: Feb 25, 2017 16:04 IST