According to the 2010 Global Burden of Diseases (GBD), published by the WHO, indoor air pollution is the second largest killer in India after blood pressure, claiming two lives every minute. The report entitled State of Global Air 2018 based on GBD has estimated that long-term exposure to outdoor and indoor pollution air pollution, the so called ‘double burden’, has contributed to around 6.1 million premature deaths from stroke, heart attacks, lung cancer and chronic lung diseases.

A paper in The Lancet Planetary Health also says that household air pollution is responsible for 40 per cent of air pollution deaths in India. Fine particles or PM2.5 are primarily responsible for the disease burden. Long-term exposure to air pollution contributes to increased risk of illness and death from a multitude of diseases. In 2019, as many as 6.67 million people died due to air pollution in the world out of which 1.67 million deaths occurred due to this reason in India. Share of deaths (in percentage terms) in India stack up as follows: lower respiratory infection (44 per cent), lung cancer (32 per cent), chronic obstructive pulmonary disease (60 per cent), neonatal outcomes (21), with some overlap in these figures.

Moreover, over the past two decades, deaths attributable to ambient PM2.5 in India has increased by 2.5 times and deaths attributable to ozone have increased by 2.9 times. The Air Quality Index (AQI) measures air pollution levels, indicating how clean or polluted the air is. Its calculation is based on five major pollutants; (1) Particulate matters (PM2.5 and PM10); (2) Nitrogen Dioxide (NO2); (3) Ozone (O3); (4) Carbon Monoxide (CO) and (5) Sulphur Dioxide (SO2). Relations among AQI value, category and health risks have been shown in Table-1. India accounts for one out of four deaths due to air pollution in 2019. Poor air quality was the fourth leading risk factor for early death worldwide in 2019, surpassed only by high blood pressure, tobacco use and poor diet.

A majority of cities in the country are in the grip of critical particulate pollution. As of 20 November 2024 the top 10 most polluted cities in India were identified by their worst AQI and recorded by the Central Pollution Control Board (CPCB) (Table -2) Air quality has been in a state of free fall ever since the beginning of the industrial revolution. Globally, 93 per cent of all children live in environments where air pollution levels are higher than what WHO guidelines recommended.

Sources of air pollution, India’s most severe environmental problem, include rapid urbanisation, widespread construction activities coupled with brisk industrialisation and burgeoning motorisation. While trucks and other heavy vehicles have been recognised as a major contributor to air pollution, in India, freight movement by rail has declined, giving way to a road-based freight system dominated by trucks. Rapid expansion of roads and highways has given impetus to road transport. The share of railways in 1950-51 was 89 per cent, which declined to 27 per cent in 2022.

India’s share of road transport is much higher than the US and China. Currently, the average truck distance covered in India per day is between 250 and 400 km. As per the All India study report submitted to PPAC (Petroleum Planning and Analysis Cell), 70 per cent of diesel is consumed in the transport sector alone. Heavy Duty trucks are responsible for high exposure to toxic fumes when they pass through human habitations. Particulate matter emission from bigger engines is higher than smaller ones.

A study conducted by Boston-based Health Effects Institute has found that the maximum effect of vehicular pollution is up to 500 metres from the road. Around 55 to 60 per cent of Delhi’s 34 million population live in high exposure zones. The pollutants disperse from urban and industrial zones into the hinterland which is itself transforming due to motorisation and modernisation, and stack up with traditional sources of air pollution like the use of biomass (coal, dung and wood) in cooking and heating, which causes deteriorating air quality in rural areas as well as.

No place is unpolluted and no one is safe from air pollution. Vehicles plying on inter-city routes and highways do not have access to cleaner fuels and languish at the lower level of emission standards. Diesel vehicles emit high level of tiny particles and NOX that also contribute to the formation of ground ozone. Diesel exhaust is also laced with some of the worst-known toxins that can have severe metabolic effects and cause cancer. Several studies have been carried out demonstrating the high impact of highway traffic on respiratory conditions, heart ailments and size of the brains of children living in close vicinity of highways. In June 2012, the World Health Organisation (WHO) and the International Agency for Research on Cancer have classified diesel exhaust as a Class 1 carcinogenic for its definite link with lung cancer, putting it in the same class as tobacco smoking, asbestos and arsenic.

London Assembly Environment Committee in 2015 in their report titled Driving away from Diesel, reducing air pollution from diesel vehicles says that particulate matter from diesel vehicles can be more harmful than other particulates. It is well established that fine and ultra-fine particulates harm one’s health. Clean air action plans should be devised and activities to reduce road dust, which is primarily PM10, should also be prioritised. Cities must also develop their macroaction plans with clear guidelines and outlines for target attainment.

In addition to these initiatives, emerging sophisticated technologies and satellite based monitoring systems may be adopted to ameliorate impacts of air pollution. The National Environment Engineering Research Institute (NEERI) tested a drone to monitor air quality at a vertical axis. The NEERI-AQ device can be loaded with multiple sensors as per the requirement for different pollutants and can collect real time data at different heights. Use of Geographic Information Systems (GIS)-based satellite data is another emerging source of high quality and standardised pollutant data. A native American proverb says that we do not inherit the earth from our ancestors; we borrow it from our children. Keeping this thoughtful and poignant quotation in mind our endeavours should be for keeping the earth free from pollution

(The writer is a retired IAS officer)