Air Pollution 101

As one of the top-ranked areas for ozone, particle pollution, and toxic air releases, the Houston region is no stranger to air quality concerns. Here you’ll find information about air pollution and what you can do to reduce your exposure.

What is Air Pollution?

An air pollutant is a substance in the air that can have adverse effects on humans and the environment. Pollutants can be classified as primary or secondary:

Primary Pollutants

Primary pollutants are substances emitted directly from a source, such as the carbon monoxide gas from a motor vehicle exhaust or sulfur dioxide released from factories.

Secondary Pollutants

Secondary pollutants form when primary pollutants react in the atmosphere. For example, ground-level ozone is created when hydrocarbons (HC) and nitrogen oxides (NOx) combine in sunlight.

Some pollutants may be both primary and secondary. Formaldehyde, for instance, may be emitted directly from a source and may also be formed by secondary reactions of certain hydrocarbons.

Common Air Pollutants

Learn about Houston’s “Dirty Dozen” air pollutants in our factsheets


What Are the Sources of Air Pollution?

While outdoor air pollution originates from both natural and man-made sources, the contribution from human activities far exceeds natural sources. Often times indoor air pollution can be even worse than outdoor air pollution depending on the chemicals in your building.

Mobile sources are vehicles used in all modes of transport, including cars, trucks, trains, ships and planes. While fossil fuel combustion is the major culprit of mobile source air pollution, tire and brake pad wear is also a significant source of mobile emissions.

There are two types of stationary air pollution sources:

  • Major stationary sources are defined as sources that emit 10 tons per year of any of EPA controlled toxic air pollutants, or 25 tons per year of a mixture of air toxics. These sources include industrial facilities like chemical plants, steel mills, oil refineries, power plants, and hazardous waste incinerators.
  • Stationary area sources consist of smaller-size facilities (e.g. metal recycling facilities, concrete batch plants, dry cleaners, gas stations) that release lesser quantities of toxic pollutants into the air. Collectively the emissions from these sources can be of concern – especially in heavily populated areas. The category also includes agricultural areas.

Natural sources are naturally occurring events which cause air pollution and include dust storms, wildfires, and volcanic eruptions. The ocurrence of these events is becoming more common with climate change, which heightens their impact on air quality. 

Indoor sources include building materials and a range of household goods. Inadequate ventilation, high temperatures and humidity levels can increase indoor pollutant levels.

Health and Equity Effects

An estimated 4.2 million premature deaths globally are associated with poor outdoor air quality, mainly from heart disease, stroke, chronic obstructive pulmonary disease, lung cancer, and acute respiratory infections in children.

While everyone is affected, most of the disease burden is borne by marginalized populations who tend to live near busy roads and industrial sites with higher air pollution levels. Other vulnerable groups include people with pre-existing lung or heart disease, as well as children with developing lungs and the elderly. 

How to Stay Safe?

Until air pollution is stopped at source, minimize your exposure with these simple actions:

Air Pollution Regulation in the U.S. and Texas

The Clean Air Act is a US federal law designed to protect human health and the environment from harmful air pollution caused by a diverse array of pollution sources. 

The Texas Commission on Environmental Quality (TCEQ) is the agency assigned to enforce the Clean Air Act in Texas. However, the TCEQ’s enforcement record leaves much to be desired: A recent investigation by the Environmental Integrity Project found that the TCEQ issued penalties for less than 3 percent of unauthorized air pollution releases from 2011 to 2016.

While the Houston area has never met the air quality standards set for ozone, the Clean Air Act has driven air quality improvements nationally for nearly 50 years, preventing hundreds of thousands of cases of serious health effects each year. 

It is critical that the Act remains enforced to ensure continued protection of all Americans from harmful impacts of air pollution.

Read More About the Clean Air Act