Air Pollutants: Detecting The Invisible With Advanced Technology

Air pollution is a pressing issue that affects the health of people and the environment. It is caused by various sources, including human-induced emissions from vehicles, industrial facilities, and cooking, as well as natural sources such as dust storms, wildfires, and volcanoes. To combat this, different technologies are used to measure and monitor air quality, such as stationary measuring devices used by government agencies, personal pollution sensors, and satellite imaging. These tools help identify pollution hotspots and provide data to take targeted action, protect human well-being, and improve air quality.

Personal pollution sensors

There are many technologies available for measuring air quality, with precision, cost, and size being key differentiators. Personal sensors are relatively cheap, costing hundreds of pounds, and are portable. This makes them a valuable tool for individuals who want to track their personal exposure to pollutants. However, it is important to exercise caution when using these devices as they vary in accuracy. Some cheaper devices are advertised as being for raising pollution awareness rather than providing accurate measurements.

While personal sensors can provide valuable data, they should not be solely relied upon for making important decisions. To ensure the effectiveness and accuracy of personal pollution sensors, researchers and the academic air-pollution community must focus on calibration, testing, and creating better devices.

Some examples of personal pollution sensors include Flow by Plume Labs, PurpleAir sensors, and Atmotube PRO. Flow measures particulate matter (PM10, PM2.5, and PM1), NO2, and VOCs. PurpleAir sensors measure particulate pollution (PM2.5), temperature, humidity, and pressure. Atmotube PRO is a portable indoor and outdoor air quality tracker that detects fine particles and total volatile organic compounds (TVOC).

Air quality monitoring

One common method is the use of air quality sensors or monitors, which can be stationary or portable. These sensors are designed to detect specific pollutants and can measure particulate matter, NO2, VOCs, and other pollutants. Some sensors use lasers to scan particulate matter density, while others use satellite imaging to measure energy reflected or emitted by the Earth. For example, the GOES-R Series satellites provide particle pollution measurements approximately every five minutes, while the JPSS satellites offer higher-resolution measurements of aerosols over the entire planet once a day.

Government agencies and research laboratories often employ sophisticated stationary measuring devices that provide precise readings up to the part per billion (ppb) level. In contrast, personal pollution sensors are smaller and more accessible, allowing individuals to measure indoor and outdoor air quality and track their exposure over time.

Air quality databanks, such as those maintained by the UNEP and IQAir, aggregate readings from various sources, including governmental, crowd-sourced, and satellite-derived air quality monitors, to produce an Air Quality Index (AQI) reading. The AQI provides a standardized way to communicate air quality levels, similar to a thermometer, with higher values indicating higher pollution levels. These databases may weigh data differently based on reliability and the type of pollution measured.

Additionally, models and calculations are used to estimate emissions of certain pollutants. For example, the amount of sulfur dioxide produced from burning coal in a power plant can be calculated, providing valuable insights into historical and global trends in air pollution.

By combining data from various sources and technologies, governments and organizations can identify air pollution hotspots and implement targeted actions to protect and improve human and environmental well-being.

Human senses

However, human senses are limited in their ability to accurately and precisely detect and measure air pollutants. While we may be able to perceive some pollutants through our senses of smell, sight, or physical sensations (such as an itchy throat), we cannot directly sense many other types of pollutants. For instance, harmful gases like carbon monoxide are odourless and colourless, making them undetectable by human senses.

Furthermore, the concentration and levels of pollutants are important factors in determining their impact on human health and the environment. Human senses are not capable of quantifying these levels or distinguishing between different types of pollutants. We rely on technology and scientific measurements to provide precise data on the specific types and amounts of pollutants present in the air.

Despite these limitations, human senses can still play a role in raising awareness and prompting further investigation. For example, if someone notices an unusual smell or a persistent itchy throat, they may be motivated to investigate further, potentially uncovering a source of pollution or a problem with indoor air quality.

In summary, while human senses can provide initial indications of air pollution, they are limited in their accuracy, precision, and ability to quantify and identify specific pollutants. Technology and scientific measurement methods are necessary to comprehensively understand and address air pollution.

Satellite imaging

One of the key advantages of satellite imaging is its ability to capture vast areas that ground-based monitoring stations cannot cover. Satellites can detect and measure various atmospheric pollutants, including nitrogen dioxide (NO2), ozone (O3), particulate matter (PM), and trace gases. These pollutants are often invisible to the naked eye, making satellites an essential tool for identifying and studying them.

Additionally, satellite data is used to measure the concentration of particles (aerosols) in the atmosphere. This is done by observing how much light reaches the Earth's surface and how much is reflected off the aerosols. The measurement, known as aerosol optical depth or aerosol optical thickness, helps in understanding the spatial distribution of pollutants and identifying air pollution hotspots.

To further enhance the accuracy of air quality assessments, satellite data is combined with ground measurements. This fusion of information is achieved through multi-modal AI models, such as AQNet, which integrate data from pollution monitoring stations with satellite imagery. By aggregating these diverse data sources, an "air-quality index" can be created, enabling comparisons of air quality across different regions.

Air Quality Index (AQI)

The Air Quality Index (AQI) is a tool used by the EPA to communicate 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 greater the health concern. For example, an AQI value of 50 or below represents good air quality, while an AQI value over 300 indicates hazardous air quality. AQI values at or below 100 are generally considered satisfactory. When AQI values exceed 100, the air quality is unhealthy, initially for certain sensitive groups of people, and then for everyone as AQI values increase further.

The AQI is a useful tool for individuals to understand the air quality in their local area and take appropriate action to protect their health. There are also personal pollution sensors available that allow individuals to measure the quality of indoor air and track their personal exposure to air pollution over time. These personal sensors are smaller and more accessible than government-issued sensors and can help individuals reduce their overall exposure to air pollution.

The AQI is also used by local governments and businesses to monitor air quality and make informed decisions about air pollution control. For example, the Airly platform provides advanced analytics and insights about air quality in specific areas.

In addition to the AQI, individuals can also use their senses to detect changes in air quality. For instance, a pungent smell when walking behind a car or a throat that itches when painting can indicate poor air quality. However, when it comes to quantifying air pollution, scientific and technological tools, such as the AQI, are necessary. These tools can vary in terms of precision, cost, and size, with government agencies typically using sophisticated, stationary measuring devices that are precise up to the part per billion (ppb).

Frequently asked questions