Air pollution due to crop residue burning in northern India causes an estimated economic loss of $30 billion annually, or nearly Rs 2 lakh crore, and is a leading risk factor of acute respiratory infections, especially among children, according to a study published on March 4.

Researchers from the US-based International Food Policy Research Institute (IFPRI) and partner institutes found that living in districts with air pollution from agriculture crop residue burning (ACRB) is a leading risk factor for acute respiratory infection (ARI), particularly in children less than five years of age. The study that estimates the health and economic costs of ACRB in northern India also found that it leads to an estimated economic loss of over $30 billion annually.

“Poor air quality is a recognised global public health epidemic, with levels of airborne particulate matter in Delhi spiking to 20 times the World Health Organisation’s safety threshold during certain days,” said Samuel Scott, IFPRI research fellow and co-author of the study.

“Among other factors, smoke from crop burning in Haryana and Punjab especially contributes to Delhi’s poor air, increasing the risk of ARI threefold for those living in districts with intense crop burning,” he said.

The study analysed health data from more than 250,000 individuals of all ages residing in rural and urban areas in India. It used NASA satellite data on fire activity to estimate the health impact of living in areas with intense crop burning by comparing them with areas not affected by ACRB. The researchers observed that as crop burning increased in Haryana, respiratory health worsened. Health was measured by the frequency of reported hospital visits for ARI symptoms.

Air pollution behind 12.5% of deaths

In India in 2015, exposure to outdoor air pollution was found to be the third leading risk factor (after high blood pressure and high fasting plasma glucose) contributing to mortality among 79 behavioural, environmental and metabolic factors. A recent study found that 12.5 per cent of the total deaths in India in 2017 were attributable to air pollution. Delhi was the state with the highest annual population-weighted mean PM2.5, followed by Uttar Pradesh, Bihar and Haryana. Whereas indoor air pollution due to burning of solid fuels in poor states like Uttar Pradesh and Bihar were important factors, the ambient particulate-matter pollution was highest in Uttar Pradesh, Haryana, Delhi, Punjab and Rajasthan.

How does air pollution become fatal?

Respiratory infections are the most common chronic disease of children globally, are a leading cause of death in developing countries and make a large contribution to the overall burden of disease as measured by disability-adjusted life years (DALYs) lost. Air pollution is a recognised contributor to respiratory disease, as airborne fine particulate matter (PM2.5) from the burning of solid fuels, vehicle exhaust, windblown soil, construction and other sources can penetrate deep into lung tissue, triggering an inflammatory cascade and oxidative stress. PM2.5 exposure has been linked to increased asthma-related emergency-room visits and hospitalisations, progression of carotid intima-medial thickness, greater chronic obstructive pulmonary disease mortality and reduced life expectancy.

Stubble burning affects health, soil fertility

ACRB is still widely practised due to political economy issues and lack of alternatives to burning among poor farmers. In Punjab alone, an estimated 44-51 million metric tonnes of residue are burned each year, with rice being the primary source. Winds carry suspended particles hundreds of miles, generating a thick cloud of smog above northern India visible by satellite. Among different sources of outdoor air pollution, ACRB was responsible for an estimated 66,200 deaths in 2015 in India. In addition to affecting human health, ACRB deteriorates soil fertility, releases greenhouse gases that contribute to global warming and results in the loss of biodiversity.

Why farmers continue crop burning?

Researchers noted that crop burning is a widespread global practice and in India is concentrated in northwest India, though has spread to other regions of the country in the past decade as new crop harvesting technology is adopted. Farmers try to maximise their yields by planting the next crop as soon as possible after the previous crop has been harvested (generally wheat after rice). To quickly clear the field for the next crop, they burn the leftover stubble rather than using the traditional method of clearing it by hand.

Firecrackers add to the damage

Researchers also examined other factors that could contribute to poor respiratory health such as firecracker burning during Diwali (it usually coincides with the time of ACRB) and motor vehicle density. Economic losses owing to exposure to air pollution from firecracker burning are estimated to be around $7 billion or nearly Rs 50,000 crore a year, researchers said. In five years, the economic loss due to burning of crop residue and firecrackers is estimated to be $190 billion, or nearly 1.7 per cent of India’s GDP, they said.

Even though air pollution has been linked to numerous health outcomes, and respiratory infections are a leading cause of death and disease in developing countries, none of the existing studies have directly linked crop burning to ARI. This study suggests that targeted government initiatives to improve crop disposal practices are worthy investments, researchers said.