Air Pollutants: Harmful Effects And Criteria Insights

Criteria air pollutants are six common air pollutants that are found all over the United States and much of the world. They include particle pollution, ground-level ozone, carbon monoxide, sulfur dioxide, nitrogen dioxide, and lead. These pollutants are harmful to human health and the environment, and can cause property damage. The Environmental Protection Agency (EPA) sets National Ambient Air Quality Standards (NAAQS) for these pollutants, which all states must abide by. Nonattainment areas, or areas that do not meet the NAAQS, must develop plans to achieve federal standards.

Particulate matter, ground-level ozone, carbon monoxide, sulfur dioxide, nitrogen dioxide, and lead are the six criteria air pollutants

Particulate matter, or particle pollution, refers to a mixture of solid particles and liquid droplets in the air. These particles can be large, such as dust, dirt, or smoke, or they can be so small that they can only be detected with an electron microscope. The smaller particles, known as fine particles or PM2.5, pose the greatest risk to health as they can be inhaled and reach deep into the lungs, and even the bloodstream. These fine particles are also the main cause of reduced visibility (haze) in many parts of the United States, affecting national parks and wilderness areas.

Ground-level ozone is a harmful air pollutant and the main ingredient in "smog." It is formed through chemical reactions between oxides of nitrogen and volatile organic compounds, which are emitted by cars, power plants, industrial boilers, and other sources. Ground-level ozone is particularly likely to reach unhealthy levels on hot, sunny days in urban areas, affecting people with asthma and sensitive vegetation.

Carbon monoxide (CO) is an outdoor air pollutant that can be dangerous when present at elevated levels. It is particularly concerning for individuals with heart disease, as it can lead to reduced oxygen in the heart and chest pain.

Nitrogen dioxide is another criteria air pollutant that has been associated with respiratory virus-induced injury and inflammation. Studies have also shown that exposure to nitrogen dioxide can cause alterations to lung metabolism, structure, and function, as well as increased susceptibility to pulmonary infections.

Lastly, lead is a persistent pollutant that can accumulate in the bones and affect various systems in the body, including the nervous system, kidney function, immune system, and reproductive and developmental systems. Children are especially vulnerable to the effects of lead exposure, which may contribute to behavioural problems, learning deficits, and lowered IQ.

Criteria air pollutants are found all over the US and can harm human health and the environment

Criteria air pollutants are common across the US and can have detrimental effects on both human health and the environment. These pollutants include particle pollution, ground-level ozone, carbon monoxide, sulfur dioxide, nitrogen dioxide, and lead. The Environmental Protection Agency (EPA) identifies areas that fail to meet air quality standards, and these are known as "nonattainment" areas. Los Angeles County, for example, currently does not meet the EPA's national air quality standards for several pollutants.

The Clean Air Act requires the EPA to set National Ambient Air Quality Standards (NAAQS) for these six common air pollutants. The EPA refers to these as "criteria" air pollutants because it develops human health-based and environmentally based criteria for setting permissible levels. The limits based on human health are called primary standards, which aim to protect the health of vulnerable groups such as asthmatics, children, and the elderly. Secondary standards are designed to prevent environmental and property damage, safeguarding animals, crops, vegetation, and buildings.

Particle pollution, or particulate matter, is of particular concern due to its ability to penetrate deep into the lungs. Smaller particles are more worrisome as they can pass through the nose and mouth, reaching the lungs and causing respiratory issues such as coughing and breathing difficulties. Prolonged exposure to elevated levels of particulate pollution increases the risk of death from cardiovascular and respiratory diseases. Ground-level ozone is also a widespread health threat, especially for those with asthma, children, older adults, and people who are active outdoors. It can cause chest pain, coughing, throat irritation, and airway inflammation, and worsen pre-existing conditions like bronchitis.

Nitrogen dioxide, a significant component of nitrogen oxides, is primarily emitted by vehicles and non-road equipment. It can irritate the lungs, causing coughing and wheezing, and increasing susceptibility to pulmonary infections and bronchitis. Carbon monoxide is another harmful pollutant, and sulfur dioxide is also regulated, with certain states, including New Hampshire, being designated as part of the Ozone Transport Region (OTR), requiring them to address the pollutants that form ozone. Lead, a heavy metal, can cause adverse health effects when inhaled or ingested, demonstrating the diverse and insidious dangers of criteria air pollutants.

Prolonged exposure to particulate pollution increases the risk of death from cardiovascular and respiratory diseases

Criteria air pollutants are six common air pollutants that are found all over the United States. They include particle pollution, ground-level ozone, carbon monoxide, sulfur dioxide, nitrogen dioxide, and lead. These pollutants can cause harm to human health, the environment, and property.

Particle pollution, also known as particulate matter (PM), is made up of tiny solid or liquid pieces in the air. These particles can be large or dark enough to be seen with the naked eye, like dust, dirt, soot, or smoke. Others are so small that they cannot be seen, and these are called PM2.5, with diameters of 2.5 micrometres or smaller. The small size of these particles means they can penetrate homes and buildings, increasing indoor pollution concentrations.

Scientific evidence has shown that short- and long-term exposure to particulate pollution is linked to an increased risk of death from cardiovascular events and diseases. Fine particulate matter can increase the risk of cardiovascular issues such as coronary syndrome, arrhythmia, heart failure, stroke, and sudden cardiac death. This is especially true for people with pre-existing heart conditions. The evidence is particularly strong for outdoor particle pollution exposure, with PM2.5 able to cause serious health problems.

The risk of cardiovascular disease from particle pollution for an individual is smaller than that of other well-established risk factors such as smoking. However, for the population as a whole, long-term exposure has been shown to increase hospitalisations and deaths from cardiovascular events. People with chronic heart disease may experience symptoms such as chest pain, palpitations, and shortness of breath after exposure to fine particulate matter.

Nitrogen dioxide irritates the lungs, causing coughing and wheezing, and making people more susceptible to colds and bronchitis

Nitrogen dioxide (NO2) is a highly reactive gas and air pollutant composed of nitrogen and oxygen. It is formed when fossil fuels such as coal, oil, and gas are burned at high temperatures. The burning of fuel by cars, trucks, and buses, as well as power plants, are the primary sources of NO2 emissions.

Nitrogen dioxide is harmful to the lungs and respiratory system. Exposure to NO2 irritates the airways and can cause coughing and wheezing. This is especially problematic for people with pre-existing respiratory conditions such as asthma, as NO2 exposure can worsen their symptoms and increase the likelihood of hospital admissions. Scientific evidence also suggests that NO2 exposure may cause asthma in children. Furthermore, NO2 exposure can make people more susceptible to respiratory infections and colds.

In addition to respiratory issues, NO2 has been linked to a range of other harmful health effects. A 2022 review of multiple studies found that elevated levels of NO2 were strongly associated with heart and lung harm, affected pregnancy and birth outcomes, and were likely associated with an increased risk of kidney and neurological harm, autoimmune disorders, and cancer.

While everyone is at risk from the health impacts of nitrogen dioxide pollution, certain subpopulations are at higher risk. These include people who live near emission sources, such as heavily traveled roadways or industrial areas, and people with pre-existing medical conditions such as asthma, chronic obstructive pulmonary disease (COPD), cardiovascular disease, diabetes, or lung cancer. People of color are also identified as a vulnerable subpopulation.

The good news is that nitrogen dioxide emissions have been declining in recent years due to more stringent standards and the cleanup of emission sources. However, it is important to continue advocating for the reduction of air pollution and to take steps to protect oneself on days with unhealthy levels of air pollutants.

Nonattainment areas must develop plans to achieve federal air quality standards in a timely fashion

The Clean Air Act requires the Environmental Protection Agency (EPA) to set National Ambient Air Quality Standards (NAAQS) for six commonly found air pollutants, known as criteria air pollutants. These pollutants are particle pollution, ground-level ozone, carbon monoxide, sulfur dioxide, nitrogen dioxide, and lead. They are found all over the United States and can cause harm to human health, the environment, and property.

The EPA, along with state and local planning agencies, identifies areas where air pollution levels fail to meet these air quality standards. These areas are called "nonattainment" areas and must develop plans to achieve federal standards in a timely fashion. For example, Los Angeles County is a nonattainment area that does not meet the U.S. EPA's national air quality standards for several pollutants. In response, the Air Quality Management District prepared the 2016 Air Quality Management Plan, a comprehensive program to improve air quality in the county.

Nonattainment areas are required to submit State Implementation Plans (SIPs) that outline specific reduction targets for emissions. These targets are set by the EPA and are based on the severity of the nonattainment status. For instance, ozone nonattainment areas classified as Moderate or higher must achieve a 15% reduction in VOC baseline emissions over a 6-year period. The EPA's decision is informed by human health-based and environmentally-based criteria, with the former being called primary standards and the latter, secondary standards.

To ensure compliance, the EPA expects states to certify the adequacy of previously approved SIP elements for a revised NAAQS through written statements. However, some commenters have objected to this process, arguing that it is redundant and a waste of resources. They believe that the EPA's existing processes, such as infrastructure SIPs, are sufficient to ensure that states meet their CAA section 110 planning obligations. Despite this, the EPA maintains its position on the certification process.

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