Air Pollution: Indicators And Warnings

Air pollution is a pressing issue that poses significant risks to both human health and the environment. It is caused by a range of economic and social activities, with certain sectors such as power generation, transportation, industry, and agriculture being major contributors. The impact of air pollution is widespread, leading to an increased disease burden, healthcare costs, reduced life expectancy, and adverse effects on ecosystems, water and soil quality, and vegetation. To address this global challenge, it is essential to identify indicators of air pollution that can guide decision-making and drive progress toward sustainable development. These indicators help monitor and assess the complex interactions between different pollutants, providing crucial data on pollutant levels, their exceedances beyond ambient air quality standards, and their subsequent impacts on health and the environment.

Air Quality Index (AQI)

The Air Quality Index (AQI) is a tool used by the US Environmental Protection Agency (EPA) to communicate information about outdoor air quality and health. The AQI includes six colour-coded categories, each corresponding to a range of index values. The higher the AQI value, the greater the level of air pollution and the more significant the health concern.

An AQI value of 50 or below represents good air quality, indicating little to no risk to health. When AQI values are above 100, the air quality is unhealthy, initially for certain sensitive groups of people, and then for everyone as the AQI value increases. AQI values at or below 100 are generally considered satisfactory. An AQI value over 300 represents hazardous air quality.

The AQI is based on measurements of particulate matter (PM2.5 and PM10), ozone (O3), nitrogen dioxide (NO2), sulfur dioxide (SO2), and carbon monoxide (CO) emissions. These are the six most common air pollutants, also known as "criteria" air pollutants. The data for these indicators are obtained from the EPA's Air Quality System (AQS) database, which uses ambient air monitors placed throughout the United States, focusing on areas expected to have higher pollutant concentrations or larger populations.

The AQI values are based on daily monitoring data for up to five criteria air pollutants. However, it is important to note that not all counties in the United States have air pollution monitors, and some monitors do not operate every day, resulting in some days without AQI values for every pollutant.

Criteria air pollutants

Carbon monoxide is a highly toxic gas that is produced by the incomplete combustion of fossil fuels. It is dangerous because it binds to red blood cells, preventing them from carrying oxygen throughout the body. Lead is a heavy metal that can contaminate air, water, and soil. Exposure to lead can cause serious health problems, including damage to the brain and nervous system, especially in children. Ground-level ozone is a harmful gas that is formed when sunlight reacts with pollutants from vehicles and power plants. It can irritate the respiratory system, causing coughing and throat irritation.

Particulate matter refers to tiny solid or liquid particles suspended in the air, which can include dust, dirt, smoke, and liquid droplets. These particles can be directly emitted or formed in the atmosphere through chemical reactions. They are classified according to their size, with PM10 and PM2.5 being the most commonly monitored particles. Nitrogen dioxide is a highly reactive gas that contributes to the formation of ground-level ozone and particulate matter. It is primarily produced by vehicles, power plants, and industrial processes involving combustion.

Sulfur dioxide is another harmful gas that is released into the atmosphere primarily through the burning of fossil fuels, such as coal and oil, by power plants and industrial facilities. Short-term exposure to sulfur dioxide can harm the human respiratory system, and elevated concentrations can contribute to particulate matter pollution and regional haze. The Clean Air Act requires the EPA to set National Ambient Air Quality Standards (NAAQS) for these criteria air pollutants, and ambient air monitors are placed throughout the United States to measure their concentrations.

Health effects

Air pollution is a serious threat to human health, causing or worsening lung and heart disease, and shortening lives. It is estimated that air pollution kills around seven million people worldwide each year, with 90% of people breathing air that contains high levels of pollutants. Both short-term and long-term exposure to air pollutants can lead to a wide range of health issues, including respiratory problems, heart disease, stroke, lung cancer, and aggravated asthma.

One of the main health effects of air pollution is its impact on the respiratory system. Air pollution can cause or worsen respiratory diseases such as asthma, COPD, emphysema, and chronic bronchitis. It can also lead to reduced lung function, respiratory infections, and breathing problems such as chest tightness, coughing, and shortness of breath. Ozone, a powerful lung irritant, is a common air pollutant that can cause inflammation and damage to the delicate lining of the small airways.

Air pollution has also been linked to an increased risk of heart disease and stroke. Fine particulate matter (PM2.5), a common air pollutant, can be inhaled deeply into the lung tissue and contribute to serious cardiovascular problems. Exposure to PM2.5 from coal has been associated with a mortality risk twice as high as that from other sources of PM2.5. This is due to the high levels of sulfur dioxide, black carbon, and metals found in coal-derived PM2.5.

The health effects of air pollution are not limited to the respiratory and cardiovascular systems. Air pollution has been linked to an increased risk of cancer, diabetes, neurological development issues in children, obesity, systemic inflammation, Alzheimer's disease, and dementia. Maternal exposure to air pollution is also associated with adverse birth outcomes, such as low birth weight, pre-term birth, and small gestational age births.

Certain groups of people are more vulnerable to the health effects of air pollution. Children, the elderly, pregnant women, and those with pre-existing health conditions are more susceptible to air pollution-related diseases. Additionally, low-income communities and minority populations are disproportionately exposed to air pollution and are more vulnerable to its adverse health impacts due to factors such as proximity to pollution sources and limited access to healthcare.

Ambient air pollution

Air pollution is a major environmental health problem affecting people in low-, middle-, and high-income countries. According to the World Health Organization (WHO), ambient (outdoor) air pollution is responsible for an estimated 4.2 million premature deaths worldwide annually, with 89% of these occurring in low- and middle-income countries.

PM2.5 and PM10 particle pollution is considered one of the most harmful types of air pollution. These fine particles can penetrate deeply into the respiratory tract, increasing the risk of respiratory infections and diseases, lung cancer, and cardiovascular diseases. Nitrogen dioxide (NO2) is another key pollutant monitored by the WHO, primarily originating from human activities related to fossil fuel combustion.

In addition to the WHO's efforts, various organizations and projects contribute to monitoring and addressing ambient air pollution. For example, the World Air Quality Index (WAQI) project provides real-time air quality data for over 10,000 stations worldwide, utilizing laser particle sensors to measure PM2.5 and PM10 pollution levels. The Environmental Protection Agencies (EPA) also play a crucial role in monitoring air quality through initiatives like the Air Quality System (AQS) database in the United States.

To reduce ambient air pollution levels and protect populations from associated health risks, the WHO's Air Quality and Health Unit works across three main areas: knowledge, evidence, and measuring progress; institutional capacity building and technical support; and leadership and coordination. Successful policies and governance depend on coordinated action between various stakeholders, including cooperation with other UN agencies and non-state actors. Additionally, addressing key sources of outdoor air pollution, such as transport, energy, waste management, and industry, is crucial for improving air quality and protecting public health.

Real-time air pollution monitoring

Technologies and Systems

Real-time air quality monitoring is made possible through advanced technologies and systems that provide data and insights. For example, Aeroqual offers integrated sensors and software for accurate real-time air quality monitoring. PurpleAir is another company that provides real-time air quality monitoring through sensors that measure particulate pollution (PM2.5), temperature, humidity, and pressure.

Harmful Air Pollutants

One of the most harmful air pollutants is PM2.5 and PM10 particle pollution. These fine particles can be monitored in real-time using laser particle sensors, such as the GAIA air quality monitor. By measuring these pollutants in real-time, individuals and communities can make informed decisions to protect their health and reduce exposure.

Data Sources and Maps

Applications and Benefits

Limitations and Considerations

While real-time air pollution monitoring provides valuable data, it is important to note that the measurements may not cover all areas. For example, in the context of the United States, not all counties have air pollution monitors, and some monitors do not operate daily. As a result, there may be limitations in the availability of Air Quality Index (AQI) values for every pollutant, every day. Additionally, the data is typically unvalidated at the time of publication and may be amended without notice due to quality assurance processes.

Frequently asked questions