Air Quality: Understanding The Norms And Standards

Air quality is a measure of the concentration of pollutants in the air. The Air Quality Index (AQI) is a representation of air pollution concentration levels, with higher AQI numbers indicating higher levels of air pollution and associated public health risks. The AQI is designed to help the public understand the levels of air pollution in their vicinity and the potential health impacts. The AQI is based on measurements of the six major pollutants included in the index and is used to determine when air quality is expected to be unhealthy. When the AQI is high, governmental bodies generally advise individuals, especially children, the elderly, and those with respiratory or cardiovascular problems, to reduce physical activity outdoors or avoid going outside altogether.

Air Quality Index (AQI)

The Air Quality Index (AQI) is a representation of air pollution concentration levels. It is a tool used by government agencies to communicate to the public how polluted the air currently is or how polluted it is forecast to become. The United States' AQI was developed by the Environmental Protection Agency (EPA) to communicate about outdoor air quality and health. The AQI includes six color-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.

The AQI measures the anticipated concentration for each of the six major pollutants included in the index, converts the readings into AQI numbers, and reports the highest AQI number for each reporting zone. Each pollutant's 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. AQI values at or below 100 are generally thought of as satisfactory. When AQI values are above 100, air quality is unhealthy: first for certain sensitive groups of people, then for everyone as AQI values get higher. For example, an AQI value of 50 or below represents good air quality, while a value over 300 represents hazardous air quality.

When the AQI is high, governmental bodies generally encourage people to reduce physical activity outdoors or even avoid going outside altogether. Children, the elderly, and individuals with respiratory or cardiovascular problems are typically the first groups affected by poor air quality.

How to protect yourself from poor air quality

Normal air quality is generally considered to be an Air Quality Index (AQI) value of 100 or below. The AQI is a representation of air pollution concentration levels, with higher values indicating a greater public health risk.

Indoors

• Stay informed about the AQI in your area and limit your time spent outdoors when the AQI is high. Sources for this information include local radio and TV weather reports, newspapers, and online platforms like the EPA's AirNow website.
• Reduce indoor air pollution by avoiding activities such as cooking, especially frying or grilling, and using your fireplace or lighting candles or incense.
• Use an air filter and adjust your air conditioning or heating system to re-circulate air instead of drawing it from outside.
• Avoid vacuuming until air quality improves, as it can re-circulate settled particles.
• Do not smoke inside your home.

Outdoors

• If you must go outside, consider wearing an N95 mask approved by NIOSH (National Institute for Occupational Safety and Health). Cloth or surgical masks do not provide adequate protection against particle pollution.
• Reduce the intensity of your outdoor activities, especially if you are in a high-risk group, including children, the elderly, or individuals with respiratory or cardiovascular issues.
• Avoid exercising outdoors when pollution levels are high. Opt for indoor alternatives, such as using a treadmill or walking in a shopping mall.
• If you must exercise outside, choose areas away from roads and traffic, as vehicles on busy highways can create high pollution levels nearby.
• Take a shower after being outdoors to rinse particles from your skin and hair.

Long-term

• Support national, state, and local efforts to clean up sources of pollution and advocate for policies that prioritize clean air.
• Reduce your energy use at home, as generating electricity contributes to air pollution and greenhouse gas emissions.
• Use public transportation, walk, bike, or carpool whenever possible, and combine trips to decrease vehicle emissions.
• Encourage your child's school to reduce exposure to school bus emissions by not idling outside and transitioning to zero-emissions buses.
• Avoid burning wood or trash, and opt for hand-powered or electric lawn care equipment instead of gasoline-powered options.

How to check your local AQI

The Air Quality Index (AQI) is a representation of air pollution concentration levels. It is an indicator developed by government agencies to communicate to the public how polluted the air currently is or how polluted it is forecast to become. As air pollution levels rise, so does the AQI, along with the associated public health risk. Children, the elderly, and individuals with respiratory or cardiovascular problems are typically the first groups affected by poor air quality. When the AQI is high, governmental bodies generally encourage people to reduce physical activity outdoors or even avoid going out altogether.

There are several ways to check your local AQI. One way is to use the AirNow Interactive Map, which includes data for air quality monitors in the US, Canada, and Mexico. You can access this map by visiting AirNow.gov. The map includes a legend that displays the AQI values and their corresponding colours. Data on the map usually updates during the second half of the hour, and you can refresh your screen periodically to see the most recent data. You can also use the Time Slider to loop through NowCast AQI data for the last 24 hours and click on a monitor to reveal NowCast AQI and raw concentration data.

Another way to check your local AQI is through the World Air Quality Index project, which provides real-time air quality data for over 10,000 stations in more than 80 countries. You can access this information by visiting WAQI.info. The website includes a map with flags indicating the locations of the stations. By hovering your mouse over a flag and clicking, you can access the full air pollution historical data for a specific city.

Additionally, you can use mobile applications such as the AirNow Mobile App to check your local AQI. This app provides real-time air quality data and allows you to set up alerts and notifications for specific locations. You can also enable location services on your mobile device to allow the app to automatically display the AQI for your current location.

It is important to note that all air quality data are unvalidated at the time of publication and may be amended without notice due to quality assurance measures. Therefore, it is recommended to refer to multiple sources and official government websites or applications to ensure the most accurate and up-to-date information.

The six major air pollutants

Air quality is an important aspect of maintaining public health and protecting the environment. The Air Quality Index (AQI) is a commonly used indicator of air pollution concentration levels, helping to determine when air quality is expected to be unhealthy. The AQI is based on federal air quality standards and measures six major air pollutants:

Ozone (O3)

Ozone is a highly reactive gas that can be harmful to humans and the environment. It is formed by the reaction of sunlight with pollutants emitted by vehicles, industrial facilities, and other sources. Ground-level ozone is a significant component of smog and can cause respiratory issues.

Carbon Monoxide (CO)

Carbon monoxide is a colourless, odourless, and toxic gas produced by the incomplete combustion of fossil fuels. It is dangerous as it displaces oxygen in the blood, leading to serious health issues and even death. Sources of carbon monoxide include vehicle emissions, fires, and the operation of certain fuel-powered tools and appliances.

Nitrogen Dioxide (NO2)

Nitrogen dioxide is a harmful gas produced by emissions from vehicles, power plants, and industrial processes. It can irritate the lungs, exacerbate respiratory conditions, and contribute to the formation of ground-level ozone and acid rain. Nitrogen dioxide is particularly harmful to children, the elderly, and individuals with pre-existing health conditions.

Sulfur Dioxide (SO2)

Sulfur dioxide is released into the atmosphere primarily during the burning of fossil fuels, such as coal, oil, and gas. It can also be emitted by volcanoes and other natural sources. Sulfur dioxide contributes to the formation of acid rain, which has detrimental effects on ecosystems, crops, and infrastructure.

Particulate Matter (PM)

Particulate matter refers to a mixture of solid particles and liquid droplets found in the air. It can be made up of various components, including dust, dirt, soot, smoke, and liquid aerosols. Particulate matter is classified into two categories based on particle size: PM2.5 and PM10. These fine particles can be inhaled and cause respiratory and cardiovascular issues.

Lead (Pb)

Lead is a toxic heavy metal that can have severe health effects, especially on children's brain development. While leaded gasoline has been phased out, lead can still be emitted into the air through industrial processes, metal production, and the burning of lead-containing materials.

These six criteria air pollutants are regulated by the U.S. Environmental Protection Agency (EPA) through the National Ambient Air Quality Standards (NAAQS). The EPA works with state, tribal, and local air agencies to monitor and maintain air quality, ensuring that levels of these pollutants remain below mandated thresholds.

How AQI values are calculated

The Air Quality Index (AQI) is calculated by converting measured pollutant concentrations to a uniform index based on the health effects associated with a particular pollutant. The AQI was developed by the Environmental Protection Agency (EPA) to provide a simple, uniform way to report daily air quality conditions. The EPA established National Ambient Air Quality Standards (NAAQS) for each pollutant to protect public health.

An AQI value of 100 generally corresponds to the level of the NAAQS for the pollutant. The Clean Air Act requires the EPA to review these standards every five years to reflect evolving health effects information. The Air Quality Index is adjusted periodically to reflect these changes. The air quality index is a piecewise linear function of the pollutant concentration. At the boundary between AQI categories, there is a discontinuous jump of one AQI unit.

The final AQI value can be calculated either per hour or per 24 hours and is the maximum of these six scores. The score for each pollutant is non-linear, as is the final AQI score. Thus, an AQI of 300 does not mean twice the pollution of an AQI of 150, nor is the air twice as harmful. The concentration of a pollutant when its IAQI is 100 does not mean the pollutant is twice as harmful if its IAQI is 50.

The AQI is divided into six categories, each corresponding to a different level of health concern. Each category also has a specific colour, making it easy for people to quickly determine whether the air quality is reaching unhealthy levels in their communities. When the forecast is for AQI values to be near or exceed 101, an air quality alert is issued. AQI forecasts heavily depend on temperatures, precipitation, wind, and cloud cover. Weather affects pollution creation and transport from other areas. The AQI forecasts enhance human health by helping residents avoid risks from air pollution.

Frequently asked questions