Understanding the Health Risks of Radon Exposure

Radon is a colorless, odorless, and tasteless radioactive gas that forms naturally from the decay of uranium in soil, rock, and water. It is the second leading cause of lung cancer after smoking, responsible for an estimated 21,000 lung cancer deaths each year in the United States. The Environmental Protection Agency (EPA) and the Surgeon General have identified radon as a major public health concern, urging all Americans to test their homes for elevated levels. Unlike other environmental hazards, radon can accumulate in any building regardless of age or construction type, making testing and mitigation essential for every property owner.

The primary route of radon entry into buildings is through cracks in concrete slabs, floor-wall joints, gaps around pipes, and sump pits. Because radon concentrations vary by geography, soil composition, and building characteristics, state and local regulations have evolved to address these risks in a targeted manner. Understanding the patchwork of radon regulations across the United States is critical for homeowners, landlords, real estate professionals, and public health officials.

For comprehensive background on radon health effects and testing recommendations, readers can refer to the EPA’s radon page and the CDC’s radon health information.

National Framework and Federal Guidelines

While the federal government does not mandate radon testing or mitigation for private homes, the EPA has established an action level of 4 picocuries per liter (pCi/L) of air. Any home or building with radon levels at or above this threshold should undergo mitigation to reduce exposure. The EPA also provides guidance for builders, schools, and commercial facilities through its Radon-Resistant New Construction (RRNC) program and the Indoor Air Quality (IAQ) Tools for Schools program. However, enforcement and specific requirements are left entirely to state and local authorities.

The lack of a national mandate has resulted in a diverse regulatory landscape. Some states have enacted stringent laws, while others rely on voluntary guidelines. Understanding your region’s requirements is essential for compliance and safety. The following sections break down state-level and local regulations, including mandatory testing in real estate transactions, new construction standards, and public building requirements.

State-Level Radon Regulations

State radon programs vary widely, from comprehensive mandated testing to minimal advisory roles. Below we detail the regulatory approaches in several key states, categorized by the strength and scope of their requirements.

States with Comprehensive Mandatory Testing and Mitigation

California

California’s Radon Program, managed by the California Department of Public Health, requires radon testing in public schools and childcare facilities. If test results exceed 4 pCi/L, school districts must conduct mitigation measures. California also mandates radon-resistant construction features in new homes built in high-risk zones (Zone 1 and Zone 2 counties). While there is no statewide requirement for real estate transactions, disclosure forms often ask about known radon levels. Homeowners are strongly encouraged to test their homes, especially in high-radon areas such as the Sierra Nevada foothills and parts of the Central Valley.

Pennsylvania

Pennsylvania has one of the most robust radon programs in the nation. The Pennsylvania Department of Environmental Protection (DEP) mandates that all homes, schools, and workplaces be tested for radon, with particular emphasis during real estate transactions. Sellers must provide radon test results to buyers or offer a waiver. All radon testing and mitigation must be performed by certified professionals. The state also requires radon-resistant construction in new homes within high-radon areas. Pennsylvania’s Radon Certification Act ensures that only licensed professionals install mitigation systems, maintaining quality and safety.

Illinois

Illinois mandates radon testing in all public school buildings every five years, with immediate action required when levels exceed 4 pCi/L. The Illinois Emergency Management Agency (IEMA) oversees radon certification for testers and mitigators. The state also encourages, but does not require, testing during real estate transactions through its Radon Disclosure Act. New construction in high-risk counties must incorporate passive radon mitigation systems. Additionally, Illinois offers free radon test kits to residents in some counties through local health departments.

New Jersey

New Jersey requires radon testing in all residential properties at the time of sale. If results exceed 4 pCi/L, the seller must mitigate the property before closing or provide a credit. All mitigation work must be performed by a certified radon mitigation contractor. The New Jersey Department of Environmental Protection (NJDEP) maintains a list of certified professionals. Public school testing is also mandatory, with mitigation required for any building exceeding the action level.

Colorado

Colorado’s high geological radon potential has led to strong regulatory measures. The Colorado Department of Public Health and Environment (CDPHE) mandates radon testing in all new public schools and requires testing in existing schools every three years. Real estate transactions in Colorado require sellers to disclose any known radon levels and provide a copy of a test result if one exists. The state also offers free radon test kits to residents through a partnership with local universities. New construction must include radon-resistant features in high-risk areas.

States with Moderate Regulatory Frameworks

These states have testing requirements in specific contexts but lack universal mandates or rely heavily on voluntary compliance.

Florida

Florida does not have a statewide requirement for radon testing in homes, but it mandates testing in public schools and certain public buildings. The Florida Department of Health provides educational materials and low-cost test kits. Several counties, including Miami-Dade and Orange, have their own radon testing programs for schools. Builders in high-risk areas are encouraged to adopt radon-resistant construction practices, but it is not legally required.

Texas

Texas has no statewide radon testing requirement for private homes. The Texas Department of State Health Services manages a voluntary radon testing program and offers free test kits. However, some municipalities, such as Austin and Houston, have implemented local ordinances requiring radon testing in new public buildings and during major renovations. Real estate agents in Texas must disclose known radon information if asked, but there is no mandated testing.

New York

New York State requires radon testing in all public schools every five years. For homes, the state recommends testing but does not mandate it during real estate transactions. Localities like New York City have stricter rules, as noted below. The New York State Department of Health offers free radon test kits to residents and maintains a list of certified mitigation professionals.

States with Minimal or Voluntary Guidelines

Many states rely on public education campaigns and voluntary testing, leaving enforcement to local health departments or individual responsibility. Examples include Alabama, Hawaii, and Oklahoma. In these states, homeowners must proactively seek radon testing, and mitigation is rarely mandatory. The EPA encourages these states to adopt stronger policies through grant programs.

Local and Municipal Radon Regulations

Local governments often fill gaps left by state laws, particularly in high-radon areas. Below are notable examples of local radon initiatives.

New York City

New York City has some of the most stringent radon regulations for a major metropolitan area. Local Law 34 of 2016 requires radon testing in all residential buildings with three or more units, as well as in all hotels and motels. If levels exceed 4 pCi/L, building owners must install mitigation systems within 90 days. The city also mandates radon-resistant construction in all new residential and commercial buildings. Testing must be conducted by a certified radon professional. These regulations aim to protect the dense population of renters and hotel guests.

Denver, Colorado

Denver’s Department of Public Health & Environment runs a comprehensive radon education and mitigation program. The city offers free radon test kits to all residents, and low-income households can receive subsidized mitigation services. Denver also requires radon radon-resistant construction in all new single-family and multi-family buildings. The city regularly conducts community outreach to raise awareness and encourage testing.

Miami-Dade County, Florida

While Florida lacks a strong state mandate, Miami-Dade County has its own radon testing requirement for all public schools. The county also requires pre-construction radon testing for certain large commercial buildings. The Department of Regulatory and Economic Resources manages a radon awareness campaign and distributes test kits at community centers.

Portland, Oregon

Portland requires radon testing in all public schools and childcare facilities. The city also encourages landlords to test rental properties and provides free test kits. Builders must include radon-resistant features in new construction if the property lies within a designated high-risk zone.

Radon in Real Estate Transactions

One of the most critical areas of radon regulation involves real estate transactions. A growing number of states require radon testing as part of the home sale process, either as a mandatory condition or through disclosure laws. Buyers and sellers should be aware of their state’s requirements to avoid legal pitfalls.

In states like Pennsylvania, New Jersey, and Illinois, a radon test must be performed before closing unless both parties waive the requirement. If elevated levels are found, the seller typically must install a mitigation system or offer a financial concession. In disclosure-only states, such as Texas and California, sellers must inform buyers of any known radon but are not required to test. Buyers in these states should always request a radon test as part of the home inspection.

Real estate professionals should carry liability insurance for radon-related claims and stay current with state laws. The National Association of Realtors (NAR) offers resources on radon disclosure best practices.

Radon Testing: Procedures and Standards

Proper radon testing is essential for accurate results. The EPA recommends testing all homes below the third floor, regardless of geographic zone. Short-term tests (2–90 days) are commonly used for real estate transactions, while long-term tests (90+ days) provide a more accurate annual average.

Testing devices include charcoal canisters, alpha-track detectors, and continuous radon monitors. All devices should be placed on the lowest livable level of the home, away from drafts, heat sources, and exterior walls. Windows and doors must remain closed for at least 12 hours before and during the test (except for normal entry and exit).

If a short-term test yields results above 4 pCi/L, follow-up testing is recommended. If the average of two tests exceeds 4 pCi/L, mitigation is strongly advised. The EPA also recommends considering mitigation for levels between 2 and 4 pCi/L, as there is no safe level of radon exposure.

For a detailed guide on testing procedures, see the EPA’s radon testing page.

Radon Mitigation Systems and Standards

When radon levels exceed the action level, mitigation is necessary. The most common method is a sub-slab depressurization (SSD) system, which uses a fan to draw radon from beneath the building and vent it safely outdoors. Other techniques include crawl space ventilation, block-wall depressurization, and sump-hole suction.

Mitigation systems must be installed by certified professionals in states that require certification. The Radon Professionals Certification Program (RPCP) under the National Environmental Health Association (NEHA) and the National Radon Safety Board (NRSB) are the primary certifying bodies. Proper system design includes a sealed suction pit, insulated piping, and a vent fan installed in an unoccupied area (such as an attic or garage). A manometer must be installed to indicate that the system is functioning.

After installation, a post-mitigation test must confirm that radon levels are below 4 pCi/L. Most systems cost between $1,500 and $3,000 for a typical home, but costs vary by region and complexity. Many states and local governments offer financial assistance for low-income households. For example, the Colorado Radon Mitigation Assistance Program provides grants up to $2,000.

For more information on mitigation standards, refer to the EPA’s consumer guide to radon reduction.

Compliance and Enforcement Challenges

Even in states with strong radon regulations, compliance can be inconsistent. Homeowners may neglect testing due to cost or lack of awareness. Landlords might avoid testing to evade mitigation costs. Public schools often struggle with funding for testing and remediation. According to a 2021 report by the Government Accountability Office (GAO), many school districts have not completed required radon testing due to budget constraints.

To improve compliance, some states have implemented penalty structures. In Pennsylvania, failure to disclose radon test results during a real estate transaction can result in fines and legal liability. New York City imposes fines of up to $1,000 per day for building owners who do not comply with testing requirements. Public health advocacy groups continue to push for stronger enforcement and federal funding for radon programs.

Resources and Next Steps for Property Owners

Whether you are a homeowner, landlord, or facility manager, taking action on radon is vital. Start by determining your state and local requirements. The EPA’s State Radon Programs directory provides contact information for each state’s radon office. Many states offer free or low-cost test kits through local health departments.

If you test and find elevated levels, do not hesitate to hire a certified mitigation contractor. The National Radon Proficiency Program (NRPP) and the National Radon Safety Board (NRSB) maintain online directories of certified professionals. For low-income households, check with your state health department for financial assistance programs.

Finally, educate yourself and your community about radon risks. Consider attending a radon awareness workshop or hosting one at your local library. The more people understand the dangers of radon, the more likely they are to test and mitigate their homes. Together, we can reduce the lung cancer burden caused by this invisible gas.