Air Pollution's Impact On Agriculture: A Growing Concern

Air pollution is a pressing issue that has been threatening human health and the environment for over a century. While its detrimental effects on human health are well-established, air pollution also poses a significant risk to agriculture, impacting food security and the nutritional quality of crops. This is a two-way relationship, as certain agricultural activities also contribute to air pollution. This complex interplay between air pollution and agriculture warrants further exploration to understand the full scope of its consequences and devise effective strategies to mitigate its adverse effects.

Ozone and its precursors

Ozone is a major air pollutant that affects agriculture. It is a secondary air pollutant, formed when other primary pollutants, mainly oxides of nitrogen (NOx), carbon monoxide (CO), and volatile organic compounds (VOCs), undergo photochemical reactions under sunny conditions. These primary pollutants are emitted from the burning of fossil fuels in transport, industry, and power generation.

Ozone is a well-known and interesting gas. It is considered "good" when present in the stratosphere, forming an ozone layer that protects life from detrimental ultraviolet radiation. However, in the lowest atmospheric layer, the troposphere, ozone becomes a concern for human and plant health. It is the third most important greenhouse gas after carbon dioxide and methane, and there is substantial evidence that it is one of the most phytotoxic (toxic to plants) air pollutants, causing significant damage to agricultural crops worldwide.

Ozone enters plant leaves through stomata, which are pores that facilitate gas exchange. Once inside the plant, ozone reacts with cellular components, creating a series of chemical reactions that result in strong oxidative stress. This oxidative stress can cause visible leaf injuries, such as yellowing (chlorosis) and stippling, and localized cell deaths (necrosis). It can also lead to more subtle physiological changes, such as reduced photosynthesis and premature senescence. These effects ultimately reduce crop yields.

The impact of ozone on crops is particularly significant in regions with high current and future ozone levels, including prominent global agriculture and food production areas. China and India, for example, are facing threats to their crop production due to ozone pollution. In India, up to 14% and 6% yield losses in wheat and rice, respectively, are attributed to ozone.

Ozone pollution has far-reaching socioeconomic implications, exacerbating existing issues such as poverty, malnourishment, and climate change impacts, which collectively challenge food and nutrition security in affected regions. It is crucial to address air quality concerns in rural areas and raise awareness among farmers, policymakers, and the public about the risks and damage caused by ozone pollution.

Air pollution and economic losses

Air pollution has been affecting agriculture for more than a century. It is a global problem that requires investments from governments and industries worldwide. The economic losses caused by air pollution in agriculture are significant and far-reaching.

In 2014, a study found that air pollution in India cut wheat and rice crop yields in half, resulting in a loss of more than 24 million tonnes of wheat in 2010, worth around $5 billion. The same study also estimated that ground-level ozone (O3) pollution caused by nitrogen oxides from combustion processes reduced global staple crop yields by 5-12%, with associated economic losses of up to $20 billion per year. According to the United Nations Environment Programme (UNEP), this trend is expected to continue, with a projected 26% reduction in staple crop yields by 2030.

The impact of air pollution on agriculture is not limited to crop yields. It also affects the nutritional quality and safety of food crops, imposing a major risk to food security. For example, in India, high levels of pollutants in major cities often surpass safe limits, and an increasing proportion of agricultural land is being affected by air pollution as cities expand into these areas. This trend is not unique to India; it is a global issue that threatens global food security.

The economic losses caused by air pollution in agriculture can also be indirect. For example, in areas like the tropics and subtropics, air pollution and global warming will reduce the number of days that subsistence farmers and outdoor labourers can work, limiting their incomes and increasing the price of food worldwide.

Furthermore, agriculture is a significant contributor to air pollution, with smoke from slash-and-burn agriculture and the production of silt, ash, and soil dust from activities like tillage, transportation, and harvesting contaminating the air with particulate matter. According to the European Court of Auditors, the amount of ammonia emitted by agriculture has increased since 2012, and agriculture's contributions to particulate matter, nitrogen dioxide, and ground-level ozone not only threaten crops but also human health.

Air pollution and human health

Air pollution is a pressing environmental issue that significantly impacts human health. It is the leading environmental cause of premature mortality and disease in Europe, with fine particulate matter (PM2.5) being the most significant contributor. The effects of air pollution on human health are wide-ranging and can lead to various diseases, including stroke, chronic obstructive pulmonary disease, trachea, bronchus and lung cancers, aggravated asthma, and lower respiratory infections. The World Health Organization (WHO) has also found links between air pollution exposure and type 2 diabetes, obesity, systemic inflammation, Alzheimer's disease, and dementia.

Children and adolescents are especially vulnerable to the effects of air pollution as their bodies and immune systems are still developing. Exposure to air pollution during childhood can increase the risk of developing diseases later in life, and they have little agency in protecting themselves or influencing policies to improve air quality.

In addition to the direct health impacts, air pollution also affects human health by reducing crop yields and nutritional quality. For example, a 2014 study in India found that air pollution, particularly ground-level ozone (O3), reduced wheat and rice crop yields by up to 50%. This not only impacts food security but also contributes to economic losses, with an estimated value of around $5 billion in 2010 for wheat crops alone.

Agricultural practices themselves contribute to air pollution, with animal-raising operations releasing methane, nitrous oxide, and ammonia. These gases not only accelerate climate change but also directly impact the health of farmers, farmworkers, and nearby communities. For instance, exposure to ammonia and hydrogen sulfide, which are present in high concentrations in animal waste, can cause respiratory ailments, dizziness, nausea, eye irritation, and even death in extreme cases.

Furthermore, the use of pesticides and herbicides in industrial agriculture can have detrimental effects on human health. Fugitive pesticide emissions and the application of animal waste on fields can expose farmworkers and nearby residents to harmful chemicals, impacting their health and quality of life.

Overall, the relationship between air pollution and human health is complex and far-reaching, underscoring the urgency of implementing sustainable practices to improve air quality and mitigate the health risks associated with air pollution.

Agriculture as a contributor to air pollution

Agriculture is a significant contributor to air pollution worldwide. Food production is responsible for a quarter of the world's greenhouse gas emissions.

The use of fertilizers is a major contributor to fine-particulate air pollution. Nitrogen-rich fertilizers and animal waste combine in the air with industrial emissions to form solid particles, which are a huge source of disease and death. These fumes from farms outweigh all other human sources of fine-particulate air pollution in much of the United States, Europe, Russia, and China.

Ammonia is the primary form of agricultural air pollution. It enters the air as a gas from heavily fertilized fields and livestock waste, combining with nitrogen oxides and sulfates from vehicles, power plants, and industrial processes to create tiny solid particles, or aerosols. These particles are no more than 2.5 micrometers across, small enough to penetrate deep into the lungs and cause heart or pulmonary disease.

Emissions from livestock manure and chemicals comprise 95% of ammonia emissions, which, in turn, account for 58% of the particulate matter air pollution in European cities. Chemical drift with pesticides, herbicides, and fertilizers can also occur as these compounds reach nearby lands or neighborhoods, contributing to poor air quality beyond the immediate area of agricultural activity.

Agricultural air pollution also contributes to smog and acid rain, which further damage crop yields by affecting the soil in which plants live.

Other ways in which agriculture contributes to air pollution include pesticides, odors, smoke, dust, allergenic pollen, and trash.

Air pollution and soil quality

Air pollution has been affecting agriculture for over a century. The burning of coal and petroleum, smelting, and the manufacture of glass and ceramics, among other industrial processes, release a host of contaminants into the air. These include aldehydes, hydrocarbons, organic acids, ozone, peroxyacetyl nitrates, pesticides, and radionuclides. The impact of these pollutants on crops varies depending on concentration, geography, and weather conditions.

Particulate Matter

Particulate matter refers to solid or liquid particles found in the air, such as soot, smoke, and dust. These particles can be large enough to be seen or so small that they can only be detected with an electron microscope. Particulate matter less than 10 micrometers in size, including fine particles less than 2.5 micrometers, can penetrate deep into the lungs, causing serious health issues. Particulate matter can also have adverse effects on soil quality and, consequently, agricultural productivity.

Cement Dust

Cement dust, for example, can accumulate in the soil, increasing soil pH to levels that are detrimental to crop growth. Additionally, when deposited on vegetation, cement dust can interfere with the normal respiration and photosynthesis processes within the leaves. It does this by forming a thick crust and producing alkaline toxicity, particularly in wet weather. The dust coating may also affect the effectiveness of pesticides and other agricultural chemicals applied to the foliage.

Acid Gases

Acid gases, such as fluorides, sulfur dioxide, and chlorine, are another category of air pollutants that can have detrimental effects on soil quality and agricultural crops. Hydrogen fluoride, for instance, is extremely toxic to plants, causing damage to chlorophyll and subsequent cell death. Fluorides are released into the atmosphere through the combustion of coal, the production of brick, tile, ceramics, and glass, and the manufacture of aluminium and steel, among other industrial processes.

Oxidants

Oxidants, primarily consisting of ozone, are another significant contributor to air pollution that can impact soil quality and agricultural productivity. Ozone is produced in the atmosphere through a photochemical reaction involving nitrogen oxides and reactive hydrocarbons, which are found in automobile exhausts and released during the combustion of fossil fuels. Vegetation injury caused by oxidant build-up in the air can occur over large rural areas. Ozone can cause a range of symptoms in plants, including flecking, bronzing, or bleaching of leaf tissues, and can lead to reduced yields and crop loss.

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