Agriculture's Air Pollution: Is Farming Making Us Sick?

Agriculture is a significant source of air pollution, with a range of practices contributing to poor air quality. These include the application of fertilisers and insecticides, livestock rearing, the use of heavy-duty machinery, and the burning of crop stubble. The chemicals in fertilisers and insecticides can evaporate into the air, contaminating the local atmosphere and contributing to climate change. Livestock farming generates methane, a potent greenhouse gas, as well as ammonia and hydrogen sulphide, which can form dangerous aerosols. The combustion of fossil fuels to power farm machinery releases carbon emissions, further polluting the air. Additionally, the growing trade in agricultural products has intensified the pollution emitted during the intensification process, shifting the burden to producer countries. This two-way relationship between agriculture and air pollution has raised concerns about its impact on food production and global food security.

Livestock farming

Livestock waste, or manure, also produces ammonia and hydrogen sulphide. Ammonia can react with other contaminants in the air to form dangerous aerosols. Meanwhile, hydrogen sulphide is an under-reported greenhouse gas that also contributes to global warming.

In addition, the large amounts of manure produced in livestock farming can negatively impact air quality in other ways. For example, manure that accumulates in litter can increase airborne particulate matter.

Furthermore, the heavy use of fertilisers in livestock farming contributes to fine-particulate air pollution. When combined with industrial emissions, fumes from nitrogen-rich fertilisers form solid particles that can penetrate deep into the lungs, causing heart or pulmonary disease.

Burning crop stubble

Stubble burning is the practice of intentionally setting fire to the straw stubble remaining after grains such as rice and wheat have been harvested. It is a quick, easy, and cheap way to clear fields, and is still widespread today, especially in Asia. However, it is a major contributor to air pollution.

The burning of crop stubble releases harmful pollutants into the atmosphere, including particulate matter contamination, carbon dioxide (CO2), carbon monoxide (CO), nitrogen oxides (NOx), sulfur oxides (SOx), and methane (CH4). These emissions cause serious damage to human health and the environment. For example, in 2012, air pollution led to about 5 million deaths in South Asia, with stubble burning being a significant factor. The emissions from stubble burning can cause skin and eye irritation, as well as severe neurological, cardiovascular, and respiratory diseases, asthma, chronic obstructive pulmonary disease (COPD), bronchitis, lung capacity loss, emphysema, and cancer.

In India, stubble burning generates a thick haze of smog, which affects people with respiratory conditions and causes eye irritation and conjunctival hyperemia. It also releases greenhouse gases and other pollutants that damage the ozone layer. Additionally, the floating threads of conductive waste produced by the burning can damage electrical and electronic equipment. There is also a risk of fires spreading out of control.

Despite the negative consequences of stubble burning, it is still practised in many places, even where it is illegal, such as in India, Pakistan, and some parts of the United States. This is due to factors such as the low cost and ease of execution of this method, as well as a lack of awareness among farmers about the harmful consequences and alternative methods.

To reduce the pollution caused by stubble burning, alternative methods such as the use of crop residues for fuel or compost, and the adoption of new technologies and sustainable management practices, have been proposed. However, the implementation of these alternatives has been varied, with some farmers citing the cost of new machinery as a significant financial burden.

Heavy machinery

The use of heavy machinery in agriculture has made farming more efficient, but it also has negative consequences for the environment. Tractors, combine harvesters, and other heavy-duty farm vehicles are essential for modern farming but contribute to air pollution through the combustion of fossil fuels. The diesel that powers these vehicles generates carbon emissions, contaminating the local atmosphere and endangering the health of nearby humans and animals.

The burning of fossil fuels to power farm machinery releases carbon dioxide, a greenhouse gas that contributes to climate change. In addition, the combustion process produces other harmful pollutants, such as nitrogen oxides and sulfates, which can have detrimental effects on human health. These emissions can lead to respiratory and other health issues, particularly for farm workers who are directly and continuously exposed to them.

Moreover, the weight and size of agricultural machinery have significantly increased over the years, exacerbating the problem of soil compaction. Soil compaction occurs when heavy machinery is driven over soil used for growing plants, leading to increased soil density, reduced air volume, and impaired drainage of surplus water. This, in turn, can result in poorer crop yields and increased pollution from agricultural land. Compacted soil is more susceptible to erosion and nutrient loss, and it reduces the effectiveness of added nitrogen, as plants are less able to absorb it.

Regulations and limitations on maximum axle load are being considered to protect the soil's potential for growth and reduce the negative impacts of heavy machinery on the environment. While some regions, like Norway, have lower-risk agricultural land due to the presence of moraine soil, which is resistant to compaction, other areas are more vulnerable to the damaging effects of heavy machinery.

Fertilisers and pesticides

Chemical fertilisers are synthetically prepared by adding required nutrients in specific ratios. When excessive fertilisers are added, they alter the characteristics of the soil and pollute the land. These chemicals can then be blown off course or evaporate into the air, contaminating the local atmosphere. The presence of nitrogen compounds in the air, caused by the overuse of synthetic fertilisers, seriously affects public health, damaging the respiratory, circulatory and immune systems. In addition, the release of reactive nitrogen from synthetic fertilisers into the atmosphere oxidises into nitrogen monoxide and nitrogen dioxide, causing damage to the ozone layer and encouraging the greenhouse effect, which accelerates global warming.

The production of artificial fertilisers has skyrocketed from about 20 million tons in 1950 to nearly 190 million tons today, with about a third of them being nitrogen-based. This increase in production is set to continue, as the global population grows and more food is needed. However, the amount of aerosols created as a result depends on many factors, including air temperature, precipitation, season, time of day, wind patterns and other necessary ingredients from industrial or natural sources.

Pesticides are chemical substances used to control pests, such as insects, fungi, and weeds. While they are effective in protecting crops, they can also be harmful to human health if exposure occurs over a long period. Pesticides are toxic by design, and this toxicity is what makes them effective at killing and deterring pests. However, it is this same toxicity that can cause health issues in humans, such as endocrine and neurotoxic disorders, respiratory diseases, and bladder, ovarian and lymphatic cancers.

The increasing use of fertilisers and pesticides has raised concerns about their impact on the environment and human health. Over the past few decades, the use of these chemicals has increased exposure for farmers, farm workers, and the general population. As a result, there has been a push for more sustainable and organic farming practices that reduce the use of synthetic fertilisers and pesticides, and instead focus on crop rotation, organic farming, and the use of organic or ecological fertilisers.

Impact on food production

Agriculture is the single largest contributor to ammonia pollution, which, along with other nitrogen compounds, has a detrimental impact on soil quality and the ability of the soil to sustain plant and animal life. The intensification of the production process in producer countries has also increased the amount of pollution emitted.

Ozone precursor emissions (nitrogen oxides and volatile organic compounds) are of particular concern for global food security as they react to form ground-level ozone, which impairs the ability of plants to develop. Ozone is estimated to cause relative global crop losses for soy by 6-16%, wheat by 7-12%, and maize by 3-5%. Some crops are more sensitive to ozone exposure than others, with wheat and soybean being particularly vulnerable. Of concern is the fact that these crops are staple foods for most of the world's population.

In India, air pollution is halving yields of wheat and rice crops. Researchers attribute this to ground-level ozone, which is formed when nitrogen oxides—mostly released from power stations and vehicles—react with air pollutants, including vehicle exhaust, oil refining, petrochemicals, and bushfires during sunlight.

Ozone forms free radicals when absorbed by plants, which attack cell membranes, causing leaf damage and reducing crop yields. It is thought to be the most important air pollutant affecting crop growth and productivity.

Livestock cultivation also contributes to air pollution, with methane being the chief greenhouse gas emitted by cows, sheep, and other livestock. Manure produced by these animals also generates ammonia and hydrogen sulphide. The former can react with other contaminants in the air to form dangerous aerosols, while the latter is a significant contributor to global warming.

The use of heavy-duty machinery in agriculture, such as tractors and combine harvesters, also contributes to air pollution through the combustion of fossil fuels. The diesel that powers these vehicles generates carbon emissions, which contaminate the local atmosphere and jeopardize the health of nearby animals and humans.

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