Indoor Radon in K-12 Schools in the United States: Where Are We Today?

What Is Radon and Why It Matters in Schools

Radon forms naturally from the decay of uranium found in soil and rock. The gas can migrate through cracks in foundations, construction joints, and other openings in buildings, allowing it to accumulate indoors. Because radon is colorless, odorless, and tasteless, its presence cannot be detected without specialized testing.

Health organizations classify radon as a known human carcinogen. When inhaled, radon decays into radioactive particles that can become lodged in the lungs, damaging lung tissue and increasing the risk of cancer over time.

In the United States, radon exposure is considered the second leading cause of lung cancer after smoking, responsible for approximately 21,000 lung cancer deaths annually.

For children, the issue is particularly concerning. Students have smaller lungs and higher breathing rates relative to body weight, potentially increasing their vulnerability to airborne contaminants such as radon. Because children spend a large portion of their day in school buildings, addressing radon exposure in these environments is a key public health priority.

The Scale of the Problem in U.S. Schools

Despite growing awareness of indoor air quality issues, radon remains widespread in school buildings. One of the most comprehensive datasets comes from the U.S. Environmental Protection Agency’s National School Radon Survey.

According to the EPA, approximately 19.3% of U.S. schools, nearly one in five, have at least one frequently occupied room with radon levels above the recommended action level of 4 picocuries per liter (pCi/L). This threshold represents the level at which mitigation actions are recommended to reduce exposure. The survey also estimated that more than 70,000 classrooms nationwide have radon levels exceeding the EPA action level. These findings suggest that elevated radon exposure could potentially affect large numbers of students and staff members across the country. Given that more than 55 million students and roughly 6 million adults occupy U.S. K-12 schools daily, even localized radon issues may impact a substantial population.

Testing Status and Awareness

One of the major challenges in addressing radon in schools is the lack of consistent nationwide testing.

Radon concentrations vary significantly between buildings, and even between rooms within the same building, because radon entry depends on soil characteristics, building design, and ventilation conditions. As a result, testing is the only reliable method for identifying elevated radon levels.

Research examining nationally representative school data found that only about 46% of schools reported ever testing for radon. Earlier assessments suggested that historically only about 20% of schools nationwide had conducted radon testing, indicating that many school buildings may still have unknown radon conditions.

Testing rates vary widely depending on geographic location, state policies, and awareness among school administrators. Schools located in regions with high geological radon potential are generally more likely to conduct testing, but schools in moderate-risk areas may remain untested.

Why Radon Levels Vary Across Schools

Radon concentrations in schools depend on several environmental and structural factors. These include:

• Local geology: Areas with uranium-rich soils or rock formations tend to produce more radon gas.

• Building construction: Slab-on-grade construction, foundation cracks, and penetrations for utilities can allow radon to enter buildings.

• Ventilation performance: Poor ventilation can allow radon to accumulate indoors.

• Seasonal variations: Radon levels often increase during colder months when buildings are sealed more tightly.

Because these factors vary widely between locations and buildings, radon levels can differ dramatically even between neighboring schools. This variability underscores the importance of building-specific testing rather than relying solely on regional risk maps.

Mitigation and Risk Reduction

The good news is that radon problems are technically solvable and well understood. When elevated levels are detected, several mitigation strategies can effectively reduce radon concentrations.

Common mitigation approaches include:

• Sub-slab depressurization systems, which use fans and piping to vent radon gas from beneath the building to the outdoors

• Sealing foundation cracks and openings to reduce radon entry pathways

• Improving ventilation and HVAC system operation

These technologies are widely used in residential buildings and have also been successfully applied in school environments. In many cases, mitigation systems can reduce radon concentrations by 80–99%, making them a highly effective risk reduction measure.

The EPA recommends that schools integrate radon management into broader indoor air quality programs, ensuring routine testing and mitigation when necessary.

Policy Landscape and Future Directions

Radon testing policies for schools vary across the United States. Some states require testing in public schools or mandate radon-resistant construction techniques for new school buildings. Other states rely primarily on voluntary guidance or recommendations.

Public health organizations, including the American Lung Association, have called for stronger nationwide policies and broader testing programs to protect students and staff from radon exposure.

Moving forward, several actions could significantly improve radon protection in schools:

1. Expanding radon testing programs nationwide

2. Implementing routine retesting schedules

3. Incorporating radon control into school IAQ management plans

4. Designing new school buildings with radon-resistant construction techniques

Such measures could significantly reduce exposure risks and improve environmental health in school buildings.

Conclusion

Radon remains one of the most important yet underrecognized environmental hazards in U.S. school buildings. Current research suggests that nearly one in five schools may have at least one classroom with elevated radon levels, and tens of thousands of classrooms exceed recommended exposure limits.

At the same time, a large percentage of schools have never tested for radon, leaving potential risks unidentified. Expanding testing programs, strengthening policies, and incorporating radon mitigation into school infrastructure planning will be essential steps toward improving indoor air quality in educational environments.

Ensuring safe air in schools is not only a matter of building management, it is a matter of protecting the health and long-term well-being of millions of children and educators across the United States.

References

1. U.S. Environmental Protection Agency (EPA). Radon in Schools.

2. U.S. Environmental Protection Agency (EPA). Indoor Air Quality Tools for Schools – Radon Appendix.

3. U.S. Environmental Protection Agency (EPA). Radon Measurement in Schools Technical Guidance.

4. American Lung Association. Radon and Lung Cancer Risk.

5. American Lung Association. Radon in Schools.

6. Washington State Department of Health. Radon in Schools Guidance.

7. Wang, Y. et al. (2018). Radon Testing Status in Schools by Radon Zone and School Location and Demographic Characteristics in the United States.

8. U.S. Environmental Protection Agency (EPA). Managing Radon in Schools.