Measuring Air Pollution: Practical Steps To Assess Air Quality

Air pollution is a critical global issue, threatening human health and contributing to climate change, biodiversity loss, and pollution. To address this crisis, measuring air pollution levels is the first step, and it can be done through various tools and methods. The Air Quality Index (AQI) is a commonly used tool that provides a simple way to communicate outdoor air quality and its associated health concerns. The AQI categories are color-coded, with green indicating good air quality and maroon indicating an emergency health warning. Other methods include air pollution calculators and air quality monitoring solutions provided by companies like Airly. Additionally, satellites, such as the Joint Polar Satellite System (JPSS), play a crucial role in collecting information about particles in the air, including smoke from wildfires and urban pollution.

Air Quality Index (AQI)

The Air Quality Index (AQI) is a tool developed 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 serious 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.

The AQI is calculated based on the five major air pollutants regulated by the Clean Air Act: ground-level ozone, particle pollution (also known as particulate matter, including PM2.5), carbon monoxide, sulphur dioxide, and nitrogen dioxide. Each of these pollutants has a national air quality standard set by the EPA to protect public health. The AQI value of 100 generally corresponds to an ambient air concentration that equals the level of the short-term national ambient air quality standard for the protection of public health. Values at or below 100 are considered satisfactory, while values above 100 indicate unhealthy air quality for certain sensitive groups of people, and eventually, everyone as values increase.

The AQI is an essential tool for public health officials, as it allows them to focus on specific pollutants and their impacts on different groups. For instance, individuals can use the AQI to learn about the air quality in their local area and take steps to protect themselves from unhealthy air pollution levels. Additionally, public health officials can utilise the AQI to develop strategic information campaigns that promote strategies to combat air pollution and mitigate its effects.

The AQI can be accessed through various sources, such as AirNow.gov, which provides air quality data at the local, state, national, and global levels. AirNow.gov offers interactive maps, calculators, and other resources to help individuals understand the AQI and take appropriate actions to improve their air quality and protect their health.

Personal pollution sensors

The data from these sensors can be accessed through companion apps that allow users to check their air quality remotely and view trend data via simple graphs. This information can help users identify sources and patterns of air pollution, such as rush-hour traffic, and take steps to mitigate chronic issues.

While some personal air quality monitors have been criticized for issues with their apps, connectivity, and customer service, others, like the PurpleAir sensors, have received positive reviews for their accuracy, quality, and customer service.

It is important to note that an AQI app on your phone can also provide information about local air quality conditions, and protective measures such as wearing an N95 respirator mask can safeguard against particulate pollutants like smoke and dust when their levels are high.

Satellite imaging

Satellite data can be used to fill in the spatial gaps of ground monitoring resources and provide information on air quality in areas without a ground monitor. They are also useful for estimating emissions, tracking pollutant plumes, supporting air quality forecasting activities, providing evidence for "exceptional event" declarations, monitoring regional long-term trends, and evaluating air quality model output.

In another study, researchers used 10,400 images to train a model to predict local levels of PM2.5 using satellite images and weather conditions. The model was tested on 2,622 images and found to be accurate within 24% of actual PM2.5 levels measured at reference stations, with a much higher spatial resolution than current standard practices. This method provides a more specific and accurate way to measure air pollution levels, which can be useful for understanding the health impacts of air pollution.

Analytical chemistry techniques

Air pollution is a complex issue that requires a range of technologies and techniques to effectively monitor and measure. Analytical chemistry plays a crucial role in this process, providing various methods to identify and quantify specific pollutants.

One of the most commonly used techniques is gas chromatography (GC). This method separates and analyses the individual components of a mixture. It is particularly useful for identifying volatile organic compounds (VOCs) and hazardous air pollutants (HAPs). For example, the Toxic Organic Method TO-15A is a GC-based technique used to measure VOCs and HAPs, such as ethylene oxide (EtO), in ambient air.

Spectroscopy and spectrophotometry are also widely employed. These techniques use light absorption or emission to identify and quantify pollutants. They can be used to measure formaldehyde concentrations in real-time and to detect trace amounts of pollutants. Spectroscopy has been used by NASA to map pollution with satellites (Mapping Pollution with Satellites, or MAPS).

Flame photometry is another important technique. It is used to measure pollutants that contain certain metals or metal oxides. This method involves passing a gas through a high-temperature flame, causing the emission of light, which is then analysed to determine the concentration of the pollutant.

Other chemical analysis techniques include the use of field sampling and laboratory analysis, which provide precision and accuracy. This includes the use of flow systems to measure gases like carbon dioxide, and the use of absorbers/scrubbers to collect samples.

The choice of analytical technique depends on the specific pollutant and the context of the measurement. For example, workplace air quality monitoring requires highly sensitive methods to reliably quantify pollutants, even at low concentrations, to ensure the safety of workers.

Regulatory bodies

Several regulatory bodies are responsible for monitoring and addressing air pollution levels. Here is an overview of some key organisations:

United Nations Environment Programme (UNEP)

The United Nations Environment Programme (UNEP) plays a crucial role in addressing global air pollution. UNEP is responsible for analysing the state of air pollution initiatives worldwide and providing early warning information to foster international cooperation on environmental issues. They have supported the deployment of low-cost sensors in various countries, including Kenya, Costa Rica, Ethiopia, and Uganda. Additionally, UNEP aims to provide technical support to over 50 countries to enhance their air quality monitoring capabilities.

World Health Organization (WHO)

The World Health Organization (WHO) has established Air Quality Guidelines (AQG) that serve as global targets for governments at all levels to strive towards improving air quality and, consequently, the health of their citizens. The guidelines recommend levels and interim targets for common air pollutants, including particulate matter (PM), ozone (O3), nitrogen dioxide (NO2), and sulfur dioxide (SO2). WHO also integrates scientific evidence on the health impacts of air pollution and monitors countries' progress in improving air quality.

United States Environmental Protection Agency (EPA)

The United States Environmental Protection Agency (EPA) is the primary federal agency in the US charged with protecting people and the environment from harmful radiation and air pollution. They have developed the Air Quality Index (AQI) as a tool to communicate about outdoor air quality and its associated health risks. The AQI is divided into six colour-coded categories, each representing a range of index values corresponding to the level of air pollution and health concerns. The EPA also establishes standards and regulations, such as the Clean Air Act (CAA), to control and reduce emissions from stationary and industrial sources.

Other Regulatory Bodies

Other regulatory and environmental groups also play a role in monitoring and addressing air pollution. These include organisations like the European Commission's Joint Research Centre, which has identified and reviewed various low-cost portable air quality sensors. Additionally, national and regional governments have their own regulatory bodies tasked with implementing and enforcing air quality standards, such as the US Federal Communication Commission (FCC) and the US Food and Drug Administration (FDA).

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