Hidden danger in the air? What you need to know about rising ozone pollution

As India grapples with the sweltering heat of its summers, a less visible but equally menacing threat looms in the air: surface ozone pollution. While the nation's bustling cities and industries have been associated with the haze of particulate matter, ground-level ozone has been silently making its presence felt.

India, unfortunately, is home to numerous highly polluted cities in the world. While particulate matter often dominates headlines, the menace of ozone pollution has been lurking in the shadows.

According to the Central Pollution Control Board's (CPCB) Air Quality Index, ozone levels in parts of Delhi and other metropolitan cities is on a rising trend. Recent data shows ozone levels spiking to hazardous levels in major metros as temperatures climb.

Yet national air quality standards and plans remain heavily focussed on particulate matter (PM2.5) alone. The National Clean Air Programme (NCAP), which was launched by the government in 2019, India's primary initiative against air pollution, has been predominantly targeting PM2.5 particles.

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These minuscule particles, less than 2.5 micrometres in diameter, can infiltrate our lungs, posing grave health risks. However, our preoccupation with particulates might be overshadowing other equally pressing threats.

R Suresh, Area Convener in The Energy and Resources Institute explained unlike other pollutants, ozone is not directly emitted from any source. It forms when nitrogen oxides (NOx), volatile organic compounds (VOCs), carbon monoxide (CO) and methane (CH4) react in the presence of sunlight and high temperatures.

This reaction is influenced by the relative concentrations of VOCs and NOx, creating what scientists refer to as "ozone isopleths." Vehicle exhaust, fossil fuel combustion, gasoline vapours, chemical solvents and natural sources release NOx and VOCs into the air - the essential ingredients for ozone formation.

At optimum temperatures and ultraviolet radiation intensity, these hydrocarbons undergo complex photochemical reactions to form ozone pollution that builds up strongly during the day but can persist late into the night. Of particular concern are NOx emissions from transportation - diesel and petrol vehicles are the largest source of ozone-forming NOx across urban India. As NOx emissions have not fallen in proportion to PM2.5, ozone levels keep creeping upwards every summer.

He gave an example that, China offers a cautionary tale in this regard. Vigorous emission controls reduced PM2.5 concentrations significantly. However, this led to a surge in ozone levels. Data from 2017 to 2019 in China's Northern Central Plains indicates a 15 per cent decrease in PM2.5, potentially driving the continued anthropogenic increase in ozone, coupled with unmitigated VOC emissions. This scenario mirrors the current trajectory in India, emphasising the need for a holistic approach to air quality management.

Ozone can wreak havoc once inhaled into the lungs. According to the WHO's Regional Office for Europe, ozone causes breathing problems, asthma attacks, lung inflammation, coughing, chest pain and throat irritation. It reduces lung function and harms the respiratory system.

Numerous studies conducted globally over decades have linked both short and long-term ozone exposure to increased hospitalisations and premature deaths from respiratory and cardiovascular causes.

Ozone likely even weakens the immune system and increases susceptibility to respiratory infections - a grave concern in the post-COVID era. A study done by scientists from University of Leeds, UK, says that by 2050, projections suggest that 1.6 million deaths in India could be attributed to ozone pollution.

But the ramifications of ozone pollution extend beyond human health. Ozone can damage crops, reducing yields and affecting food security. Ozone also cripples crop yields and harms food security. As this pollutant enters leaves through pores called stomata, it damages plant tissues, accelerates ageing, slows photosynthesis, stunts growth and eventually slashes crop yields. A study published in the American Geophysical Union’s Journal highlighted that the present-day ozone-induced damage to wheat and rice in India is sufficient to feed roughly 35 per cent of the nation's poor.

Models suggest wheat production losses of 26-35 million metric tonnes globally due to ozone pollution. Studies conducted locally at Indian Agriculture Research Institute and other institutes show ozone exposure during peak crop growth results in 10-15 per cent yield loss for grains like rice, wheat and soybean across parts of India.

With extreme heat, erratic rainfall and other climate change effects already shrinking farm incomes, unchecked ozone pollution poses a significant risk to India's agriculture sector and self-sufficiency goals.

Ozone isn't just toxic to humans and plants - it degrades materials as well. As a strong oxidising agent, ozone accelerates corrosion of metals, degrades polymers and erodes building materials over time. Studies estimate it causes between 3-5 per cent additional economic losses due to reduced service life of rubber, textiles, dyes and paints. India's prized monuments like the Taj Mahal face enhanced degradation from rising ozone pollution in urban centres like Agra. The economic toll from ozone's infrastructure damage will only rise over time if left unaddressed.

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Addressing this multifaceted challenge requires a comprehensive strategy. Transitioning to electric vehicles can significantly curtail NOx emissions. Promoting public transportation, carpooling, and implementing stricter emission norms can further help. But it's not just about reactive measures. Proactive monitoring, understanding the interplay of different pollutants, and public awareness campaigns are equally crucial. While PM2.5 has been the poster child of India's air pollution narrative, it's time to broaden the discourse. A myriad of pollutants, each with its unique challenges and health implications, contribute to the air we breathe. Our goal should be unequivocal: safeguard public health. Achieving this necessitates a comprehensive approach to air quality management.

The urgency to address ozone pollution in India is palpable. With awareness, collective responsibility, and actionable strategies, we can pave the way for cleaner air. It's not merely an environmental concern; it's about our health, our future, and the legacy we leave for subsequent generations. As India strides forward, ensuring that every breath we take is a step towards a brighter, healthier future should be paramount.

(Disclaimer: The views of the writer do not represent the views of WION or ZMCL. Nor does WION or ZMCL endorse the views of the writer.)

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