Air Quality Measurement: What Does It Mean?

Air quality is a measure of the pollutants in the air, including particulate matter and gaseous pollutants. Air quality is measured using the Air Quality Index (AQI), a scale that runs from zero to 500, with higher values indicating greater levels of air pollution and health concerns. The AQI is calculated using data from air quality monitors, which may be government-run, crowd-sourced, or satellite-based, that detect specific pollutants such as PM2.5, PM10, ground-level ozone, nitrogen dioxide, and sulfur dioxide. While the AQI is a useful tool, it has limitations in capturing local variations in air pollution and disparities in exposure. Different countries and localities may also use their own air quality indices and thresholds for good air quality.

Air Quality Index (AQI)

Air quality is measured using the Air Quality Index (AQI). The AQI is a scale that runs from 0 to 500, with higher values indicating a greater level of air pollution and health concern. An AQI value of 50 or below represents good air quality, while a value over 300 indicates hazardous air quality. The AQI is divided into six colour-coded categories, each corresponding to a different level of health concern.

The AQI is based on the measurement of several air pollutants, including particulate matter (PM2.5 and PM10), ozone (O3), nitrogen dioxide (NO2), sulfur dioxide (SO2), and carbon monoxide (CO). These pollutants are monitored by instruments on the ground and satellites orbiting the Earth, such as the Joint Polar Satellite System (JPSS) and the Geostationary Operational Environmental Satellites-R (GOES-R) Series.

The data from these sources is processed by air quality databases, which may weigh the information differently depending on reliability and pollution type. These databases produce an aggregated AQI reading, which is used to inform the public about the current air quality and any potential health risks. For example, the AirNow website provides air quality data for local, state, national, and global levels.

It is important to note that air quality is a critical issue, as the World Health Organization estimates that 99% of the global population breathes unclean air, leading to approximately 7 million premature deaths annually. Therefore, the AQI plays a vital role in helping individuals understand the air quality in their communities and take appropriate actions to protect their health when necessary.

Air quality sensors

There are various types of air quality sensors available, from low-cost air pollution monitors to more advanced satellite-based systems. Low-cost air pollution sensors are designed to detect, monitor, and report on specific air pollutants like particulate matter (PM), carbon dioxide, and environmental factors such as temperature and humidity. These sensors are becoming increasingly accessible due to advancements in technology, providing consumers with a simple and quick way to assess indoor air quality. However, it is important to note that low-cost sensors may have limitations in detecting all pollutants and do not provide a complete representation of indoor air quality.

On the other hand, satellite-based sensors, such as those used by NOAA's GOES-R series and the Joint Polar Satellite System (JPSS), provide global coverage and measure particle pollution, smoke from wildfires, airborne dust, urban and industrial pollution, and volcanic ash. These satellites can provide frequent and high-resolution measurements of aerosols and particles in our atmosphere, contributing to a better understanding of air quality on a larger scale.

The data collected by air quality sensors is processed to generate Air Quality Index (AQI) values. The AQI is a scale that ranges from 0 to 500, with higher values indicating increased levels of air pollution and associated health concerns. For example, an AQI value of 50 or below represents good air quality, while a value over 300 indicates hazardous air quality. The AQI is an essential tool for communicating about outdoor air quality and its potential impact on human health.

Overall, air quality sensors play a crucial role in monitoring and assessing air pollution, enabling governments, researchers, and individuals to take informed actions to improve air quality and protect public health. With the ongoing deterioration of air quality globally, these sensors provide valuable insights that can help address the air pollution crisis and mitigate its impact on human health, climate change, and the environment.

Air quality standards

The Air Quality Index (AQI) is a yardstick that measures the level of air pollution and indicates the potential health concerns associated with it. The AQI is calculated using data from air quality monitors, which are outfitted with sensors designed to detect specific pollutants. These monitors may be ground-based instruments or satellites orbiting the Earth. The higher the AQI value, which ranges from 0 to 500, the greater the level of air pollution and the more significant the health concern. For instance, an AQI value of 50 or below indicates good air quality, whereas an AQI value exceeding 300 signifies hazardous air quality.

The AQI is divided into six categories, each represented by a distinct colour. This colour-coding system enables people to swiftly ascertain the air quality level in their communities. AQI values of 100 or below are generally considered satisfactory. When AQI values surpass 100, the air quality is deemed unhealthy, initially for specific vulnerable groups and subsequently for everyone as the values continue to rise.

In the United States, the Environmental Protection Agency (EPA) establishes an AQI for five major air pollutants regulated by the Clean Air Act. These pollutants include ground-level ozone, nitrogen dioxide, and particulate matter (PM2.5 and PM10). Each pollutant is subject to a national air quality standard set by the EPA to safeguard public health. The Clean Air Act identifies two types of national ambient air quality standards: primary and secondary. Primary standards aim to protect public health, including vulnerable populations such as asthmatics, children, and the elderly. Secondary standards focus on public welfare protection, encompassing aspects like visibility, damage to crops and vegetation, and impacts on wildlife and property.

The World Health Organization (WHO) has reported that 99% of the global population breathes air that does not meet clean air standards, leading to approximately 7 million premature deaths annually. PM2.5, which refers to particulate matter with a diameter of 2.5 micrometres or less, is of particular concern. When inhaled, PM2.5 can enter the bloodstream and has been linked to serious health issues such as stroke, heart disease, lung disease, and cancer. To address this pressing issue, experts urge governments to strengthen air quality regulations and enhance monitoring capabilities to effectively track PM2.5 and other harmful pollutants.

Air quality monitoring

AQI values are based on large population studies and provide guidance on the overall health risk of air pollution. When AQI values are above 100, the air quality is considered unhealthy first for sensitive groups, such as children, the elderly, and individuals with respiratory or cardiovascular issues, and then for everyone as values increase. To protect public health, governmental bodies typically recommend reducing physical activity outdoors or even avoiding going outside during periods of poor air quality. In the case of wildfires, the use of masks and indoor air purifiers may also be advised.

Air quality sensors and monitors, including satellite technology, play a crucial role in capturing air quality data. These instruments detect specific pollutants, such as particulate matter (PM), nitrogen oxides, ozone, sulfur oxides, carbon monoxide, and lead. Satellites like those in the Geostationary Operational Environmental Satellites-R (GOES-R) Series and the Joint Polar Satellite System (JPSS) provide particle pollution measurements over specific regions, with the latter also measuring carbon monoxide levels.

While the AQI is a valuable tool, it has some limitations. It relies on air monitors often placed near cities, which may not capture pollution disparities on a smaller scale or from industrial sources. Additionally, different localities and countries use varying thresholds for "good" air quality, depending on the pollutants measured. For instance, Australia uses a linear scale where 100 represents the maximum concentration standard for each pollutant, while India's National Air Quality Index (NAQI) categories range from "Good" to "Severe."

To address these challenges, organizations like NASA have developed networks of low-cost sensors, such as the Inexpensive Network Sensor Technology for Exploring Pollution (INSTEP) program, to enhance local air quality monitoring. Additionally, the Tropospheric Emissions: Monitoring of Pollution (TEMPO) mission measures air quality and pollution over North America, contributing to a more comprehensive understanding of air pollution.

Health risks of air pollution

Air quality is measured using Air Quality Index (AQI) values. Instruments on the ground and satellites orbiting Earth collect information about what is in our air. Air quality monitors are equipped with sensors designed to detect specific pollutants. Some use lasers to scan particulate matter density in a cubic metre of air, while others rely on satellite imaging to measure energy reflected or emitted by the Earth. The greater the density of pollutants in the air, the higher the AQI.

Air pollution is a major health risk, threatening human health at every stage of life. According to the World Health Organization, 99% of the global population breathes unclean air, and air pollution causes 7 million premature deaths annually. The pollutants tied to human and environmental health impacts include PM2.5, PM10, ground-level ozone, nitrogen dioxide, and sulfur dioxide.

Short-term exposure to higher levels of outdoor air pollution is associated with reduced lung function, asthma, cardiac problems, emergency department visits, and hospital admissions. Long-term exposure to fine particulate matter increases a person's risk of developing diseases with a longer onset, such as non-communicable diseases including stroke, heart disease, chronic obstructive pulmonary disease, and cancer.

Air pollution can also lead to oxidative stress and inflammation in human cells, which may lay the foundation for chronic diseases and cancer. Fine particulate matter can penetrate deep into the lungs, enter the bloodstream, and travel to organs, causing systemic damage to tissues and cells. This can impact almost every organ in the body, including the lungs, heart, and brain.

Children are particularly vulnerable to the health impacts of air pollution. Higher air pollution levels increase short-term respiratory infections, which lead to more school absences. Children who play outdoor sports and live in high-ozone communities are more likely to develop asthma. Living in communities with higher pollution levels can cause lung damage and increase the risk of bronchitis symptoms in adulthood. Exposure to air pollution may also alter the size of a child's developing brain, increasing the risk for cognitive and emotional problems later in adolescence.

Pregnant women are also more susceptible to the health impacts of air pollution. Exposure to air pollution increases the risk of dangerous changes in blood pressure, known as hypertensive disorders, which are a leading cause of pre-term birth, low birth weight, and maternal and fetal illness and death.

Additionally, psychosocial stress can amplify the harmful effects of air pollution. Research has shown that people of colour are more likely to be exposed to air pollution and are more vulnerable to its health impacts. This is often due to systemic racism, which has led to discriminatory practices such as redlining and residential segregation, limiting the ability of people of colour to build wealth and relocate to safer areas.

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