Summer is upon us. Temperatures are crossing 40°C in several parts of the country. The IMD has already had to issue heatwave warnings for multiple states. But it's not just the scorching heat and high levels of humidity that people have to watch out for in these months. Sweltering summer days - the kind that bake pavements and roads - also causes air quality across Indian cities to plummet.
Mumbai, for instance, had “poor” air quality while experiencing its hottest February in two decades and above normal temperatures in March. Similarly, residents of Patna and Indore struggled for fresh air this month as temperatures nearly touched 40°C. And just last week, Delhi Environment Minister Gopal Rai directed departments to prepare action plans to curb air pollution in time for the scorching summer.
But why is the air so polluted in the summer lately, and how does it affect us? Let’s find out.
In India, air pollution is common in the winter months when inversion, induced by cold and calm weather, traps pollution close to the ground. These meteorological conditions, however, are absent in the summer. Warm air typically rises and carries pollutants away. At times, however, hot, still, and dry air leads to a build-up of pollutants, particularly dust, particulate matter and ozone. When this mass stays over the same area for several days, the phenomenon is known as stagnation. At such times, light winds cannot blow away the pollutants.
Climate change exacerbates this problem. Our country has been experiencing some of the hottest summers on record in recent years. The seasonal average air temperature last year, for example, was 1.24°C warmer than the baseline trends, as per the Centre for Science and Environment (CSE). More summer heat brings in more stagnation days. In 2022, for instance, a study conducted by the CSE found high PM 2.5 (fine particulate matter) levels across multiple cities and regions of India from March to May. North India fared the worst with a 23 percent increase in average summer pollution, while central India followed at 15.6 percent.
Its effects are further compounded in heat islands - urban areas with highly concentrated structures and limited greenery. These places typically record higher temperatures than the outer regions. They also demand more electricity for cooling during the summer months. It means turning to coal-fuelled power plants, as they play a major role in power generation and produce about 70 percent of the country’s electricity needs. That, in turn, leads to an increase in air pollutants and greenhouse gas emissions. These pollutants also contribute to the formation of smog, fine particulate matter, and acid rain.
Last year, for instance, the densely populated Delhi-NCR area had the worst regional air from March to May. It also had 12 of the cities in the top 20 with highest summer pollution levels, including Delhi, Ghaziabad, Manesar, Noida, Faridabad and Gurugram.
Summers also mean heatwaves, especially in north and central India. Under the effect of climate change, they are now occurring more often, getting longer in duration and more intense with each passing year. In 2022 alone, India recorded 203 heatwave days, the highest in the recent past, as per data shared by the Ministry of Earth Sciences in the Lok Sabha. The maximum number of such episodes were reported from Uttarakhand (28), followed by Rajasthan (26), Punjab and Haryana (24 each), Jharkhand (18) and Delhi (17).
Heatwaves make air pollution deadlier. Ground-level ozone, a kind of pollution, is made more efficiently on hot, sunny days. When there is extreme heat, it can reach dangerous levels in cities and the areas around them. It’s also often ignored. “Even before we could control the problem of particulate pollution, the toxic threat of ground-level ozone is catching up with us. Despite the warning signs, this problem has not attracted adequate policy or public attention for mitigation and prevention. If not addressed early, it can blow up as a serious health crisis in the coming years,” said Anumita Roychowdhury, executive director-research and advocacy, CSE, while talking about summer pollution.
Air pollution adversely affects human health. It causes eye irritation and cardiovascular disease, makes breathing difficult, and leads to inflammation, oxidative stress and even death. That’s why it is recommended that one avoid strenuous outdoor activities at times when pollutant concentrations are high in the air. This is especially true for people with allergies and asthma, though women who are pregnant and the elderly too need to be cautious.
“It’s smart to track the air quality index of your city, and if possible, of your area, since it can vary. Avoid activity during traffic hours, and around major sources of emissions such as industrial facilities, major roads and airports. Be aware that exposure to air pollution increases during exercise since we breathe more heavily, so defer strenuous physical activity when the air quality is bad,” says Dr Tanay Jha, consulting pulmonologist based in Lucknow.
While these steps work at an individual level to reduce exposure, they do not help in avoiding poor air altogether. That will only be possible when policy makers integrate public health into environmental and climate change policy, and urban planning.