University of Sourthern California


How to Measure Air Pollution and Its Effects

Clouds of pollution above a city skyline.Air quality is fundamental to a healthy living environment. Clean air improves public health by reducing health problems associated with air pollution, including severe asthma, decreased lung function and premature death. Lower air pollution levels can also protect environmental ecosystems, as clean air promotes healthy soil, improves long-term forest health and decreases toxins in the food chain. Additionally, clean air has positive economic effects, as health improvements can translate to reduced medical costs and absenteeism rates.

While the positive benefits of clean air are evident, the unfortunate reality is that air pollution is still a major concern in major cities around the country. Nowhere is this situation more dire and infamous than in Los Angeles, California, where decades of poor air quality have long made it the municipal face of the air pollution crisis.

The situation is important and needs to be resolved. Poor air quality impacts the lives of the nearly 10 million residents that live in Los Angeles County. The need to address the issue is immediate: The 2022 edition of the American Lung Association (ALA) State of the Air report delivered a failing grade to LA’s air quality. If left unchecked, this could lead to a greater risk of heart and lung illnesses; according to the ALA, this places those with cardiovascular disease and chronic obstructive pulmonary disease (COPD) at particular risk.

Failing to address the problem can deliver massive issues concerning public health and its associated socioeconomic fallout. It can also do significant damage to the city’s dynamic natural environment. For the city’s public health officials, understanding how to measure air pollution in LA is just the first step. That data must be followed up with actions that make a difference.

How to Measure Air Pollution

Air pollution can be measured in many different ways. These measuring tools help public health officials quantify current air quality, predict future progression and gain insight into strategies to improve health conditions. Below are some methods of how to measure air pollution.

Air Quality Index

The U.S. Environmental Protection Agency’s Air Quality Index, also known as the AQI, is a numerical system that measures the level of air pollution in a given region. The higher the number, the worse the air quality. The index is split into six different categories that correspond to a different numerical value, color and level of concern. The categories are as follows:

  • Green (0-50) — Good: Air pollution is of little to no risk.
  • Yellow (51-100) — Moderate: While air quality is acceptable, some may be at risk, particularly those who have heightened sensitivity to air pollution.
  • Orange (101-150) — Unhealthy for Sensitive Groups: People with sensitivities may experience negative health effects, but the general public will less likely be affected.
  • Red (151-200) — Unhealthy: The general public may experience health effects, and those with sensitivities may experience more serious effects.
  • Purple (201-300) — Very Unhealthy: Everyone’s at increased risk of health effects, and a health alert is enacted.
  • Maroon (301 and Higher) — Hazardous: A health warning of emergency conditions is enacted, meaning that everyone’s more likely to be impacted.

Public health officials can use the AQI to help make recommendations on specific behaviors. These can include the level of outdoor activity or the length of time that sensitive people should be outdoors.

Air Pollution Calculators

An air pollution calculator allows public health officials to focus on a specific pollutant. They input a pollutant and its AQI level — for example, carbon monoxide, 4 — and the calculator responds with the concentration level and AQI category — for example, 0.3 parts per million, good — along with corresponding information for sensitive groups and health impact statements.

Air Emissions Monitoring

Air emissions monitoring is the gathering and interpretation of information to determine whether EPA regulatory requirements are being met. The EPA quantifies two types of monitoring, each with a specific purpose.

  • Ambient Air Quality Monitoring: This type of monitoring measures ambient air pollutant samples to determine how the current atmosphere compares with historical information and clean air standards.
  • Stationary Source Emissions Monitoring: This type of monitoring measures emissions data at individual stationary emissions sources. This can include measuring facility output, the performance of emissions control devices or confirming specific work practices.

Both types can provide public health officials with vital information that can be useful in determining whether current emissions processes need to be adjusted.

Air Quality Forecasting via Interactive Maps

IQAir provides real-time information on air quality standards according to the guidelines set forth by the World Health Organization (WHO). This data can be useful in predicting trends and developing proactive air quality strategies.

What Causes Air Pollution?

Air pollution is complex. Several different components can be and contribute to poor air quality in unique ways.  Those exploring how to measure air pollution should understand the impact of these different elements.

The sources below are key contributors to what causes air pollution.


Ozone is an atmospheric gas that occurs when pollutants from cars, refineries and power plants and emissions from similar sources chemically react to the presence of sunshine. This is better known as smog. Long-term exposure to ozone can reduce lung capacity, particularly for those with lung disease.

Noxious Gasses

Noxious gasses include carbon monoxide, carbon dioxide, sulfur oxides, and nitrogen oxides. They’re found in vehicular emissions and can also be by-products of industrial processes. Prolonged exposure to noxious gasses can cause respiratory irritation and aggravate respiratory diseases.

Particulate Matter

Particulate matter (PM) consists of a class of chemicals that includes carbon, mineral dust, nitrates, and sulfates. This matter can come from several sources, including the following:

  • Motor vehicles
  • Cigarette smoke
  • Industrial emission via the combustion of fossil fuels
  • Wildfires and other burning organic matter

PM also contains the subcategory of fine particulate matter, which is typically 30 times thinner than a human hair. This enables it to embed itself into lung tissue, where it can cause serious health issues, including cardiovascular concerns.

Volatile Organic Compounds

Volatile organic compounds (VOCs) are carbon-containing compounds that vaporize at around room temperature. Natural gas and gasoline can produce VOCs during combustion. Pesticides, glue, cleaning supplies and paints can also create VOCs. Exposure carries a wide range of effects, from eye, nose and throat irritation to headaches and nausea. Prolonged exposure can also cause serious issues, such as liver, kidney and central nervous system damage.

Polycyclic Aromatic Hydrocarbons

Polycyclic aromatic hydrocarbons (PAHs) are organic compounds that contain carbon and hydrogen. They can be found in particulate matter or on their own. They can be produced via combustion or through industrial processes such as power generation or the manufacturing of iron, steel and rubber. Several PAHs are classified as carcinogens: agents that can potentially cause cancer.

Traffic-Related Air Pollution

Traffic-related air pollution (TRAP) is a blend of many of the particles and gasses named above. This combination of elements can contribute to a wide range of health issues.

Air pollution comes from a wide range of sources. These are decided into categories, which can help public health officials address air pollution by reducing its impact one group at a time, according to the National Institute of Environmental Health Sciences: Traffic-related air pollution, ozone, noxious gasses, particulate matter, volatile organic compounds and polycyclic aromatic hydrocarbons.

Air Pollution in Los Angeles

Air pollution in Los Angeles is a perennial focus for discussions of poor air quality in the United States. Its reputation for high ozone and particulate pollution is well-earned and persists to this day.

Historically speaking, air pollution has been a problem in LA since the turn of the 20th century, when the rise of industry produced thick, dense emissions that blanketed the city. This issue worsened as the city’s population grew and its infamous car culture flourished. The city’s peak problems manifested in the 1940s and 1950s, just before the advent of concentrated scientific exploration of air pollution.

While government regulations designed to measure air pollution and reduce air pollution-causing elements have helped reduce pollutants since this peak, poor air quality continues to plague the greater Los Angeles area.

Air quality index tools and sources such as the ALA highlight the serious level of the issue. Here are examples:

  • ALA data determine an average of around 114 high ozone days in LA per year.
  • While the ALA notes that particle pollution within a 24-hour period has declined significantly since 2000, it has steadily increased since 2014.
  • IQAir estimates that air pollution contributed to approximately 11,000 deaths in LA in 2021.
  • IQAir also estimates that air pollution cost LA approximately $25 billion in 2021.

The ALA also notes that LA’s poor air quality can place several large groups at a health risk. These include the following:

  • 2,099,477 children under 18
  • 1,444,480 adults 65 and over
  • 737,556 people with adult asthma
  • 534,658 people with cardiovascular disease
  • 414,388 people with COPD
  • 143,253 children with pediatric asthma
  • 109,495 pregnant women

Additionally, the ALA notes that poor air quality places an increased health risk on the 1,289,368 people who live in poverty.

Rising temperatures and severe wildfires in the LA area due to climate change mean that issues of air pollution will continue to be critical. The situation is poised to get worse: According to the Southern California Association of Governments (SCAG), Los Angeles County is anticipated to have 37 extreme heat days by 2060. This is more than five times the number of extreme heat days experienced in the county at the end of the 20th century.

Other Cities With Poor Air Quality

While the ALA reports that the greater Los Angeles area currently ranks in the top 10 cities impacted by ozone (first), year-round particle pollution (fifth) and short-term particle pollution (eight), it’s far from the only major metropolitan area in the country that suffers from poor air quality.

Phoenix, Arizona

The Phoenix-Mesa, Arizona, metropolitan area currently ranks fifth in cities impacted by high ozone days, 11th for 24-hour particle pollution and eighth for annual particle pollution. The sprawling area’s large population means that approximately 5.1 million people are at risk due to poor air quality.

San Diego, California

The San Diego-Chula Vista-Carlsbad, California, area currently ranks sixth in cities impacted by high ozone days, 13th for 24-hour particle pollution and 33rd for annual particle pollution. These conditions put the roughly 3.3 million residents within the cluster of coastal communities at risk.

Denver, Colorado

The Denver-Aurora, Colorado, area currently ranks seventh in cities impacted by high ozone days, 26th for 24-hour particle pollution and 31st for annual particle pollution. The roughly 3.6 million people living within this region are considered at risk due to pollution conditions.

Houston, Texas

The Houston-The Woodlands, Texas, area currently ranks eighth in cities impacted by high ozone days, 44th for 24-hour particle pollution and 22nd for annual particle pollution. Overall, air pollution poses a threat to the area’s massive population of roughly 7.3 million residents.

Salt Lake City, Utah

While the Salt Lake City-Provo-Orem, Utah, area ranks 105th for annual particle pollution, it currently ranks 10th in cities impacted by high ozone days and 20th for 24-hour particle pollution. These conditions put the roughly 2.6 million residents in the area at risk.

Negative Effects of Air Pollution

In the short term, air pollution can cause irritation, discomfort and difficulty breathing. While these conditions are commonly associated with poor air quality, the prolonged effects of air pollution can cause substantially more serious health conditions, including the risk of premature death. Understanding how to measure air pollution can help researchers understand these health effects and the associated risk factors.


Poor air quality can increase the risk of certain cancers. For example, living near airborne toxic substances or major roadways — where TRAP conditions thrive — can put women at an increased risk of developing breast cancer. Long-term exposure to PM in air pollution can increase the risk of lung cancer, according to the American Cancer Society’s CA: A Cancer Journal for Clinicians.

Cardiovascular Disease

Poor air quality can increase the risk of a host of cardiovascular conditions. For example, prolonged exposure to fine PM may negatively impact blood vessel function and accelerate artery calcification. Increased exposure to noxious gasses can increase the risk of hemorrhagic stroke in postmenopausal women. TRAP can also have negative effects on the blood pressure of pregnant women; this can lead to premature birth, low birth weight and maternal and fetal death.

Respiratory Disease

The respiratory conditions caused by poor air quality often go beyond temporary discomfort. Air pollution can adversely impact lung development and fuel chronic conditions such as asthma, emphysema, COPD and bronchitis.

Children’s Health and Development

Poor air quality can have serious detrimental effects on childhood long-term respiratory health. Exposure can make children particularly susceptible to the development of asthma, particularly if they live near busy roads or play outdoor sports in areas with high ozone levels. These conditions can also impede childhood development in ways beyond health; air pollution can increase the potential for short-term respiratory infections, which can lead to increased school absences and hinder educational opportunities.

Prenatal Developmental Health and Development

The impact of air pollution on young children can develop into other conditions as they age. Exposure to even low PM levels can alter the size of a child’s brain as it develops, potentially leading to an increased risk of cognitive and emotional problems in the adolescent years. Low birth weight, early onset high blood pressure and a greater risk of autism have also been linked to exposure to certain forms of air pollutants, such as fine PM.

Beyond individual health, air pollution can directly impact environmental health, causing negative changes to groundwater and soil. It can also disrupt weather patterns and lead to acid rain and global warming.

Progress in Reducing Air Pollution

These health concerns were not fully understood for decades, even as precautionary measures like schools keeping children indoors on particularly smoggy days occurred in Los Angeles during the 1970s and 1980s. This changed in 1992, as a team of USC public health researchers launched the Southern California Children’s Health Study. The study, which is still ongoing, measured the impact air pollution had on children.

The results established the dangerous effects of smog on health and development. Other journals such as the New England Journal of Medicine and The Lancet have corroborated the USC study. Collectively, their work has helped further influence policies designed to reduce smog and its harmful health effects.

Other measures, such as the Clean Air Act of 1990 have helped to mitigate air pollution in large cities like LA. Between 2017 and 2018, LA’s AQI improved by 10.6%, and between 2018 and 2019, it improved by 11.8%.

Poor air quality can have significant long-term health implications. The following health issues are associated with poor air quality, according to the National Institute of Environmental Health Sciences. Cancers: Lung, breast and non-Hodgkin’s lymphoma. Cardiovascular diseases: stroke, hypertension, blood vessel function. Respiratory diseases: emphysema, chronic obstructive pulmonary disease, chronic bronchitis. Children’s health issues: asthma, bronchitis, lung damage. Prenatal issues: brain development, autism, low birth weight.

How to Reduce Air Pollution

For public health officials in LA and other at-risk cities, measuring air pollution and identifying solutions to mitigate its impact is a critical task. While daunting, it’s achievable. However, it’ll require a group effort from multiple stakeholders, from government agencies to corporate interests to the general public.

Alongside that necessary large-scale response, individuals can learn how to reduce air pollution and protect their health.

Everyday Tips for Air Pollution Reduction

Fighting air pollution isn’t always complex. Simple daily activities can make an impact on improving air quality. These include the following:

  • Conserving energy
  • Using alternative means of transportation, such as:
    • Carpool
    • Public transportation
    • Bike
    • Walking
  • Proper vehicle maintenance
  • Composting
  • Using environmentally safe cleaning products

What to Do When Ozone Levels Are High

Strategies that can be deployed during high ozone level events include the following:

  • Combining errands into one trip
  • Walking to errands
  • Conserving electricity
  • Avoiding gardening chores that use gas-powered equipment

What to Do When Particle Levels Are High

Tactics for days with high particle levels include the following:

  • Reducing car trips
  • Reducing wood stove usage
  • Avoiding burning trash and other materials
  • Avoiding gas-powered lawn equipment

Tips to Minimize Air Pollution Exposur

Individuals can take certain steps to protect themselves from unhealthy air pollution levels, including the following:

  • Checking air pollution forecasts daily
  • Avoiding outdoor activities on days with high pollution levels
  • Avoiding exercise near high-traffic areas
  • Prohibiting indoor smoking

Public health officials can use leadership and communication to develop strategic information campaigns that promote strategies to combat air pollution. They can also advocate for communities to work toward measures that help improve air quality. For example, they can promote legislation to make public places smoke-free. To reduce climate change, they can also push for big-picture legislative policies, which typically address clean air.


These resources can help public health workers and LA residents alike make smarter approaches toward air pollution reduction.

American Lung Association, Healthy Air Campaign: Tools to advocate for legislative change, resource information on existing policies and ways to participate in a wide range of virtual and in-person events.

AirNow, Interactive Map of Air Quality: An online map that provides real-time information on air quality for LA and other areas of the United States. It also provides forecasts and 24-hour loops to help monitor quality.

U.S. Environmental Protection Agency, Technical Air Pollution Resources: A comprehensive collection of links to information discussing the measurement, regulation, science and prevention of air pollution.

Push for Cleaner Air

Poor air quality has long plagued the LA area, and while it’s true that it’s improved since the 1950s, there’s still a long way to go. Considering the damage that poor air can do to humans and the environment, it’s not a problem to take lightly.

Public health officials can use their knowledge and skills to measure air pollution and create solutions to this serious issue. From promoting strategies that encourage people to take proactive measures against air pollution to pushing for legislation that can make a difference on a larger scale, their work will continue to be crucial as we aim for a world with clean air rules.

Infographic Source:

National Institute of Environmental Health Sciences, Air Pollution and Your Health