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Air Pollutants & EPA Standards Cheat Sheet
A printable reference covering particulate matter, ozone, carbon monoxide, nitrogen dioxide, sulfur dioxide, lead, AQI, and EPA standards for grades 9-12.
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This cheat sheet covers the major outdoor air pollutants regulated by the U.S. Environmental Protection Agency and the standards used to protect public health. Students need it to connect pollution sources, health effects, concentration units, and legal limits in one quick reference. It is especially useful for comparing pollutants such as PM2.5, ozone, carbon monoxide, nitrogen dioxide, sulfur dioxide, and lead. It also supports labs, data analysis, and environmental policy discussions. The core ideas are that pollutants are measured as concentrations, exposure time matters, and EPA standards set maximum allowable levels for specific averaging periods. Important formulas include concentration = amount of pollutant / volume of air and the AQI interpolation formula for converting pollutant levels into health categories. Primary pollutants are emitted directly, while secondary pollutants form through chemical reactions in the atmosphere. A strong understanding of units such as ppm, ppb, and ug/m3 helps students interpret real air quality data correctly.
Key Facts
- Concentration is calculated as concentration = amount of pollutant / volume of air.
- The 2024 EPA annual PM2.5 standard is 9.0 ug/m3, and the 24-hour PM2.5 standard is 35 ug/m3.
- The EPA ozone standard is 0.070 ppm averaged over 8 hours.
- The EPA carbon monoxide standards are 9 ppm for an 8-hour average and 35 ppm for a 1-hour average.
- The EPA nitrogen dioxide standards are 100 ppb for a 1-hour average and 53 ppb for an annual average.
- The EPA sulfur dioxide standard is 75 ppb for a 1-hour average.
- The EPA lead standard is 0.15 ug/m3 averaged over a rolling 3-month period.
- AQI is calculated within a category using AQI = ((Ihigh - Ilow) / (Chigh - Clow)) x (C - Clow) + Ilow.
Vocabulary
- Criteria air pollutants
- The six common outdoor air pollutants regulated by the EPA under national air quality standards.
- Particulate matter
- A mixture of tiny solid particles and liquid droplets in air, often classified as PM2.5 or PM10 by particle diameter.
- Ground-level ozone
- A secondary pollutant formed when nitrogen oxides and volatile organic compounds react in sunlight near Earth’s surface.
- National Ambient Air Quality Standards
- EPA limits for outdoor pollutant concentrations designed to protect public health and the environment.
- Air Quality Index
- A scale from 0 to 500 that translates pollutant concentrations into health risk categories for the public.
- Averaging period
- The length of time over which pollutant concentrations are averaged before comparing them with a standard.
Common Mistakes to Avoid
- Confusing ppm, ppb, and ug/m3 is wrong because gases and particles are often reported in different units and cannot be compared directly without conversion.
- Comparing a 1-hour measurement to an annual standard is wrong because EPA limits depend on the averaging period used for that pollutant.
- Calling ground-level ozone a directly emitted pollutant is wrong because it usually forms in the atmosphere from precursor pollutants and sunlight.
- Assuming a low AQI means every pollutant is harmless is wrong because AQI reports the main health risk but sensitive groups may still be affected.
- Ignoring particle size is wrong because PM2.5 penetrates deeper into the lungs than larger particles and has different health risks than PM10.
Practice Questions
- 1 A city reports an 8-hour ozone average of 0.083 ppm. Does this meet the EPA ozone standard of 0.070 ppm?
- 2 A filter collects 18 ug of PM2.5 from 2.0 m3 of air. Calculate the PM2.5 concentration using concentration = mass / volume.
- 3 A monitoring station records carbon monoxide at 11 ppm for an 8-hour average. Compare this value with the EPA 8-hour CO standard of 9 ppm and state whether it exceeds the standard.
- 4 Explain why reducing nitrogen oxides from vehicles can help lower ground-level ozone even though ozone is not emitted directly from tailpipes.