Crop Burning: A Major Cause Of Air Pollution

Burning crops is a traditional agricultural practice that has been used for centuries to clear stubble, weeds, and waste before planting a new crop. While this method may be economical and efficient, it has severe environmental and health consequences. The burning of crops releases large amounts of particle pollutants, such as black carbon, into the atmosphere, contributing to air pollution and climate change. This practice has been linked to increased mortality rates and respiratory issues, with the World Health Organization (WHO) estimating that air pollution kills approximately 7 million people annually. In addition, crop burning reduces soil fertility and contributes to flooding and drought, threatening food security and impacting billions of lives. As a result, there is a growing global effort to promote alternatives to crop burning and reduce air pollution.

Burning crops releases particle pollutants like black carbon, reducing soil fertility

Burning crops is a common practice in many parts of the world, where farmers set fire to fields to clear stubble, weeds, and waste before planting a new crop. While this method may be economical and efficient for farmers, it has detrimental effects on the environment and human health. The burning of crops releases particle pollutants, such as black carbon, into the atmosphere, which has far-reaching consequences, including reduced soil fertility.

Black carbon, a short-lived air pollutant, is a product of the incomplete combustion of fossil fuels, biomass, and biofuels. It is a major component of particulate matter, known as PM2.5, which is hazardous to human health. PM2.5 is a mixture of solid particles and liquid droplets found in the air, with a diameter of 2.5 micrometres or less. These particles are so small that they can penetrate deep into the respiratory tract, causing serious health issues. Epidemiological studies have shown that exposure to PM2.5 increases the risk of premature death, even at low levels.

The release of black carbon and other particle pollutants from crop burning contributes to poor air quality, particularly in agricultural regions. In India, for example, crop residue burning has been associated with severe air pollution in cities like Delhi. From 2003 to 2019, it was estimated that agricultural residue burning caused 44,000–98,000 premature deaths annually in India, with certain states contributing more significantly to these figures.

The impact of crop burning extends beyond air quality and human health. Black carbon, when deposited on snow and glaciers, can accelerate melting, contributing to increased flooding and drought. In the context of the Himalayan glaciers, the melting caused by black carbon emissions from crop burning affects the lives of billions who depend on rivers originating in those mountains.

Furthermore, the practice of burning crops reduces soil fertility. This reduction in soil fertility has economic implications, as it can lead to lower crop yields and impact the livelihood of farmers. The negative impact on soil fertility creates a cycle where farmers may feel compelled to continue the practice of burning to clear fields for new crops, perpetuating the environmental and health issues associated with crop burning.

Burning agricultural waste is a fast and economical practice that farmers use to clear stubble, weeds and waste

Burning agricultural waste is a fast and economical practice that farmers use to clear stubble, weeds, and waste. It is a common method to remove excess residue, control pests, and facilitate timely planting. While it is inexpensive and effective, it also has several negative consequences.

The burning of agricultural waste has been associated with increasing air pollution due to the release of particulate matter, greenhouse gases, and other pollutants that damage the ozone layer. In India, for example, stubble burning contributes to a thick haze of smog, containing fine black and brown carbon, that affects light absorption and poses significant health risks. The practice of stubble burning is illegal in India and Pakistan, but weak enforcement has allowed it to continue.

The negative impacts of burning agricultural waste extend beyond air pollution. It also results in the loss of essential plant nutrients, organic carbon (C), and soil organic matter. This, in turn, reduces the soil's ability to supply nutrients to future crops, hold water, and maintain its structure. Additionally, the burning of crop residues can lead to damage to electrical and electronic equipment from floating threads of conductive waste.

To address the negative consequences of burning agricultural waste, alternative practices have been proposed. These include mechanical residue management techniques such as disking and tilling, which incorporate residues into the soil. However, these methods require significant fuel and labor costs. Another alternative is winter flooding, which is commonly used in rice fields, but it also entails additional equipment and irrigation costs.

Some companies have developed innovative solutions, such as the Indian Agricultural Research Institute's enzyme bio-decomposer solution, which can be sprayed on fields after harvest to increase organic carbon in the soil and maintain soil health. Other alternatives include growing sustainable crops like millets and maize instead of rice and wheat to conserve water. While these options may incur higher costs, they offer environmental and health benefits that make them attractive choices in the long run.

Epidemiological studies show that exposure to PM2.5 increases the risk of mortality

Burning crops releases harmful pollutants into the atmosphere, contributing to poor air quality. This is a well-known issue in India, where crop residue burning is a common practice despite government interventions. The burning of crop residues, such as stubble and straw, releases particulate matter, including PM2.5, which is a major concern for human health.

PM2.5 refers to fine particulate matter with a diameter of 2.5 micrometres or less. These tiny particles can be inhaled and are small enough to penetrate deep into the respiratory tract, causing adverse health effects. Epidemiological studies have found a strong association between exposure to PM2.5 and an increased risk of mortality, even at low levels of exposure.

Numerous studies have linked long-term exposure to PM2.5 with elevated mortality rates. For instance, a Canadian cohort study found that for each 1 μg/m3 increase in black carbon exposure, a major component of PM2.5, there was a 3.7% increased risk of non-accidental death. Similarly, Gan et al. examined the impact of traffic-related air pollutants, including PM2.5, on coronary heart disease (CHD) mortality in Vancouver. They found that an interquartile range elevation in black carbon concentration was associated with a 6% increase in CHD-related deaths, even after adjusting for various factors.

Short-term exposure to PM2.5 has also been associated with increased mortality. Some studies have reported that short-term increases in PM2.5 components, particularly black carbon, nitrate, and sulfate, may lead to higher hospital admission rates for cardiovascular and respiratory diseases and increased mortality from these conditions. Additionally, Crouse et al. investigated the link between long-term exposure to PM2.5 and cardiovascular mortality in Canada.

The specific mechanisms by which PM2.5 exposure leads to adverse health outcomes include the induction of oxidative stress, inflammation, and immune responses in humans. PM2.5-bound chemical components can exhibit greater toxicity and impact cellular functions, potentially leading to mutations and the development of various diseases. These findings highlight the critical connection between PM2.5 exposure and health outcomes, emphasizing the importance of reducing PM2.5 levels to mitigate the associated health risks.

Burning crops can cause flooding and drought, threatening food security and equality

Burning crops is a major source of air pollution, which has a complex and bidirectional relationship with agriculture. While agriculture can contribute to air pollution, it is also affected by it. Air pollution can cause lower crop yields, damaged crops, and other negative outcomes. For example, a study by Lobell and Burney found that reductions in ozone, particulate matter, nitrogen dioxide, and sulfur dioxide between 1999 and 2019 contributed to about 20% of the increase in US corn and soybean yield gains during that period. Similarly, a 2000 study found that ground-level ozone pollution impacted 23 different crops, resulting in 6.7 billion Euros worth of damage. Current estimates suggest that ground-level ozone pollution is causing between 5% and 12% yield losses globally in staple crops such as wheat, rice, and maize. The associated economic losses from affected crops are estimated to be up to $20 billion per year.

Burning crops, specifically, can release toxic smoke and pollutants into the atmosphere, causing air pollution. This can have significant health and environmental consequences. In India, for example, crop residue burning has been linked to 44,000–98,000 premature deaths annually due to particulate matter exposure. Additionally, air pollution from crop burning can contribute to climate change, which can further impact agriculture.

Climate change and extreme weather events, such as flooding and drought, pose significant threats to food security and equality. Floods and droughts can destroy crops, reduce crop production, cause variable yields, and ruin entire harvests. For example, heavy rainfall and floods in the Brazilian state of Rio Grande do Sul in 2024 impacted soybean fields, while drought in southern Africa during the same year ruined about half of Zimbabwe's maize crop. Similarly, in 2023, a combination of floods and record-high temperatures led to a significant drop in pear yields from Italian orchards.

Burning crops can contribute to climate change and, in turn, increase the frequency and intensity of extreme weather events, including flooding and drought. In Northern India, for instance, reducing air pollution from crop burning could help prevent increased flooding and drought caused by black carbon accelerating the melting of Himalayan ice and glaciers. This would have life-changing outcomes for the billions of people who depend on the rivers fed by those mountains.

Overall, burning crops can indirectly lead to flooding and drought by contributing to climate change and air pollution, which, in turn, threaten food security and equality. The complex relationship between agriculture, air pollution, and climate change underscores the importance of sustainable agricultural practices and efforts to mitigate climate change and improve air quality.

Burning crops releases methane, ammonia, hydrogen sulfide and other harmful chemicals

Burning crops is a common approach to eliminating waste after harvesting. However, this practice releases various harmful chemicals into the atmosphere, contributing to air pollution and causing adverse health effects. One of the primary gases released during crop burning is methane (CH4), a potent greenhouse gas. Methane has a significant impact on global warming and climate change. In addition to methane, crop residue burning emits ammonia (NH3) and hydrogen sulfide (H2S), which are also generated from animal agriculture. These gases not only contribute to climate change but also pose risks to human health.

Ammonia, for example, can react with other pollutants in the atmosphere, forming fine particulate matter (PM2.5) that can penetrate deep into the lungs and cause respiratory issues. Hydrogen sulfide is a toxic gas with a characteristic rotten egg odour. Exposure to hydrogen sulfide can irritate the eyes, nose, and throat and cause respiratory problems, especially for individuals with pre-existing respiratory conditions.

Furthermore, burning crops releases other harmful substances such as nitrous oxide (N2O), a greenhouse gas that contributes to climate change. Nitrous oxide also plays a role in depleting the ozone layer, which is crucial for protecting us from harmful ultraviolet (UV) radiation. The release of these gases during crop burning has significant environmental and health implications.

In addition to the gases mentioned above, crop burning emits carbon dioxide (CO2), carbon monoxide (CO), black carbon (BC), organic carbon (OC), volatile organic compounds (VOCs), non-methane hydrocarbons (NMHCs), ozone (O3), and aerosols. These emissions contribute to the degradation of air quality, leading to increased mortality and other health risks. Epidemiological studies have linked exposure to PM2.5, even at low levels, to an increased risk of premature death.

The impact of crop burning on air quality and public health has been particularly evident in India, where crop residue burning is a widespread practice despite government bans and interventions. Studies have estimated that agricultural residue burning in India caused 44,000–98,000 premature deaths annually due to particulate matter exposure. This issue is not limited to India, as air pollution from agricultural activities, including crop burning, affects regions worldwide.

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