Air quality is an important determinant of human health and has been greatly impacted by increased air pollution from industry and transportation. In response, government agencies and scientists have created air quality standards that set benchmarks for unhealthy air quality.

This article will cover the following questions about air quality standards:

• What are air quality standards?
• What pollutants are evaluated?
• How are air quality standards set?
• How is air quality measured?

The 2020 Environmental Performance Index study (EPI) out of Yale University looks at three indicators to determine overall air quality in a country:

• PM_2.5 Exposure: A score standardized by years of life lost per 100,000 people per day as a result of exposure to the particulate matter below the size of 2.5 micrometers

• Household Solid Fuels: Measured in years of life lost per 100,000 people per day due to exposure to air pollution from household burning of coal and wood

• Ozone Exposure:  Compared through years of life lost per 100,000 people per day due to exposure to ground-level ozone

All three scores are taken into account to give a country an air quality score out of 100. The countries are then ranked according to their scores. These three parameters were chosen because they are good global indicators of air quality that apply to all countries relatively evenly for comparison.

The United States has its own system of standards set by the Environmental Protection Agency (EPA). The EPA is a government agency dedicated to setting, researching, and enforcing environmental standards across the United States. Although the standards do not legally apply worldwide, they provide a helpful base for examining air quality more specifically.

What are Air Quality Standards?

The air quality standards set by the EPA aim to provide a national standard for what healthy air is so that unhealthy air quality can be quickly identified and managed. They have similarities to the parameters chosen by the EPI, however, there are more specific factors the EPA looks for.

What Pollutants are Evaluated?

Air quality standards are set by the EPA in accordance with the Clean Air Act of 1963. The Clean Air Act requires the EPA to set standards for these six common air pollutants we will cover here briefly:

• Ground-Level Ozone: A gaseous molecule that can aggravate the lungs and cause issues for the elderly or asthmatic. 

• Particulate Matter: Floating solid particles and liquid droplets that can cause respiratory distress at high levels.

• Carbon Monoxide: A deadly, gaseous molecule released from burning fuels. 

• Lead: A naturally occurring toxic metal released into the air by metal processing plants and airplanes. 

• Sulfur Dioxide: A respiratory irritant released from the burning of sulfur. 

• Nitrogen Dioxide: A gaseous respiratory irritant released from cars and trucks.

These six pollutants, in particular, are standardized because they are both:

• Relatively common in the air

                    and

• Toxic or harmful at set concentrations

How are the Standards Set?

The standards are set based on a process developed by the EPA. This process is conducted periodically to update air quality standards to ensure they fall in accordance with the most recent findings from the scientific community. 

Below is the five-step process conducted by the EPA to set or update air quality standards:

1. Planning: The EPA plans what issues need to be researched and what standards should be updated based on input from the scientific community

2. Integrated Science Assessment: The EPA looks at specific scientific research based on the plan created to evaluate recent key findings

3. Risk/Exposure Assessments: The assessments then move to determine the health effects of exposure to the substance/s being researched and estimates at what concentration the substance becomes harmful

4. Policy Assessment: The EPA uses the scientific review process to recommend what policies should be enacted or updated to respond to new findings

5. Rulemaking: The EPA officially proposes specific rules based on the assessments, and a final decision is made creating new standards or updating old ones

How is Air Quality Measured?

Once standards are set, the EPA measures air quality in different areas and compares it to the standards to determine if air quality is unhealthy. This process is what the EPA calls designation. 

Air quality is measured on a state scale. So, individual states measure the criteria air pollutants using monitoring devices that can test for the six pollutants. The state is then designated as one of the two options:

• Attainment: Pollutant levels are lower than the set standard
• Nonattainment: Pollutant levels are at or above the set standard

In nonattainment areas, the EPA will implement a process to diagnose the cause of the high air pollutant and aim to solve the problem from there.

Key Takeaways

• Air quality standards determine the concentration of various pollutants in the air that is acceptable for human health

• The Environmental Performance Index study looks at three areas of air pollution (PM_2.5, household solid fuels, and ozone exposure) to give each country a score for the health of its air

• The EPA evaluates a set of six common pollutants to determine air quality in an area

• The standards are set through a process that includes the evaluation of scientific research on air pollutants and end with a rule created by the EPA regarding acceptable levels of air pollutants 

• Air quality is measured at a state level and states can meet each criterion (attainment) or not meet the criterion (nonattainment) 

• If air quality standards are not being met, the EPA will diagnose the issue and attempt to fix it