Air pollution is the introduction of harmful chemicals into the atmosphere. Sometimes, air pollution is visible. The exhaust from this truck, for instance, is polluting the air with toxic chemicals such as carbon monoxide and formaldehyde.

Photograph by Erika Allen, MyShot
  • On April 2, 2007, the U.S. Supreme Court declared that carbon dioxide and other greenhouse gasses were air pollutants under the Clean Air Act. This case, Massachusetts vs. the Environmental Protection Agency (EPA), was the first trial on climate change. The outcome gave the EPA the ability to regulate greenhouse gas emissions from vehicles and other industry sources. 
    The case helped give momentum to the conversation about global warming, the current period of climate change. It forced the EPA to set regulations, perform studies, and analyze data about greenhouse gases. The information gained from the EPA's studies, as well as the studies of scientists the world over, gave the world a better understanding of climate change.
  • Term Part of Speech Definition Encyclopedic Entry
    analyze Verb

    to study in detail.

    carbon dioxide Noun

    greenhouse gas produced by animals during respiration and used by plants during photosynthesis. Carbon dioxide is also the byproduct of burning fossil fuels.

    climate change Noun

    gradual changes in all the interconnected weather elements on our planet.

    Encyclopedic Entry: Earth's Changing Climate
    data Plural Noun

    (singular: datum) information collected during a scientific study.

    emission Noun

    discharge or release.

    global warming Noun

    increase in the average temperature of the Earth's air and oceans.

    Encyclopedic Entry: The Greenhouse Effect and our Planet
    greenhouse gas Noun

    gas in the atmosphere, such as carbon dioxide, methane, water vapor, and ozone, that absorbs solar heat reflected by the surface of the Earth, warming the atmosphere.

    pollutant Noun

    chemical or other substance that harms a natural resource.

    regulate Verb

    to determine and administer a set of rules for an activity.