January is National Radon Action Month, during which time the U.S. Environmental Protection Agency (EPA) and other concerned organizations encourage awareness of the danger that radon, a gaseous radioactive element, poses to those exposed in buildings and homes. Toxic, odorless, and colorless, radon is the number one cause of lung cancer among non-smokers, according to EPA estimates. The below article from Tina Jordan, an industrial hygienist at ALTA Environmental, explains where radon may be a threat in the U.S. and describes the basic elements of radon testing and remediation.
By Tina Jordan
Clean air is an asset, especially top quality indoor air. When evaluating indoor air quality (IAQ), aspects such as temperature, relative humidity, and office or classroom cleanliness are often examined, as well as proper storage of cleaning products and everyday chemicals. One commonly forgotten component of good indoor air quality is radon gas. Radon gas is an odorless, colorless soil gas that is a by-product of the breakdown of uranium in soil, rock, and water that gets into buildings and schools and into the air we breathe. Only the visible components of the air quality are evaluated and included in most indoor air quality programs, which means that radon can often go overlooked.
Yet, high levels of radon gas may have significant health effects. Elevated radon levels can occur in any indoor environment, and exposure in the school or workplace can increase the risk of developing lung cancer.
Background levels of radon gas in the ambient outdoor air are typically below one picocurie per liter of air (pCi/L). A “picocurie” is the unit of measurement for radon gas concentrations used by the United States Environmental Protection Agency (EPA). The level of concern as established by the EPA is 4.0 pCu/L.
Locations where people spend much of their time, such as homes, offices and schools, may be a source of radon exposure.
Radon typically is present in certain areas with geologic conditions which may lead to radon gas. There are some areas where radon is not thought to be present because of the geological setting of the site. The EPA and some states have developed maps based on geologic conditions where radon is suspected to be a potential concern. Some of the maps also include testing data as well. For instance there are several “pockets” in southern California such as the Palos Verdes peninsula, areas in Ventura and Santa Barbara that have high levels of radon due to geologic conditions. Without the geologic conditions, radon is unlikely to be present.
The initial concern about radon gas was in single family residences and schools. The protocols subsequently developed included one or two samples in a house and samples in each classroom of a school. Elevated radon gas levels are primarily a concern in spaces closest to the building’s foundation, such as basements and ground floor spaces. However, office buildings and multi-unit apartments are more complicated structures with a different set of air flow dynamics and pathways for radon entry.
Radon Testing In Buildings
Commercial buildings and multi-family housing, especially those with lower level-parking garages, utility and storage rooms, plumbing and other utility chases and heating, ventilating and air-conditioning systems, require a different approach to testing.
Current protocols for testing were developed by the American National Standard Institute (ANSI) and American Association of Radon Scientists and Technologists (AARST). These protocols currently recommend testing all basement spaces, such as utility and storage rooms, occupied spaces above a garage, 10% of spaces in the floor above and staggered spaces in additional above spaces so the tested units on one floor are not directly above tested units directly below.
In commercial or office spaces, there is a concern for worker safety since every employer has a legal obligation to provide and maintain a safe and healthful workplace for employees, according to the California Occupational Safety and Health Act of 1973.
Residential care facilities, public housing, governmental offices as well as schools must have testing conducted by a certified individual. In California, the certifying entity is the California Department of Public Health which requires performance testing and continuing education for certification.
Testing for radon may be short-term (48 hours) and requires specific conditions to be met including “closed-house” conditions which limit the amount of air entering a building from doors, windows or whole-house fans, or a long-term test (90 days) which does not have specific testing conditions that are required. Testing is the only way to determine the concentrations of radon gas in a classroom or office.
What do the results mean? A result greater than the EPA-established 4.0 pCu/L indicates that radon gas is entering the space and concentrating, most likely on the lower level of the structure, and dissipating to the upper levels. At this level, the health effects of radon gas may be significant, especially for young children. A qualified and certified radon mitigation contractor can design a system to lower the radon gas concentrations below the EPA action level of 4.0 pCu/L.
School and commercial building measurements and mitigations are not a simple extension of residential services. Due to increased air movement from the building’s HVAC system(s), varying occupancy times, unusual radon entry mechanisms, inappropriate energy conservation applications, and unusual structural features, it may be difficult to characterize the radon concentrations in a school or commercial building.
These structures present multiple challenges to maintain a low radon level. Since large volumes of air are involved, the first consideration to lower radon levels is to evaluate the air handling system. Making a determination of the building’s air pressure differentials is critical to designing the radon mitigation system.
Utility tunnels, other service chases, and how the ventilation system affects building air pressure differentials must be investigated. This is typically done by building inspections, consultation with maintenance personnel, and consultation with architects and building engineers.
The EPA has published radon mitigation standards for residential buildings but there are no published mitigation standards for commercial buildings or schools. It is generally an accepted practice, however, to use the residential standards as a minimum for commercial buildings.
The system is designed to reduce radon gas concentrations and typically consists of a fan on the roof and a vent pipe under the structure to draw out the radon gas and discharge it outside. In a commercial building, multiple fans and piping systems to depressurize the slab may be required to effectively reduce the radon levels below 4.0 pCi/L.
In summary, designing radon mitigation systems for large commercial buildings or schools requires more extensive considerations than residential buildings. Commercial mitigation system’s design requires knowledge of: a building’s HVAC operation and foundation components, where to seal openings especially into block walls or in finished rooms, how to make differential pressure measurements and interpret results, and whether to size fan and piping based on sub-slab communication testing, pressure drop tables and anticipated airflows.
Jordan is an industrial hygienist at ALTA Environmental, a full-service consulting firm specializing in subsurface remediation, air quality, building sciences, sustainability, water resources, and environmental health and safety compliance services. The firm is located in Long Beach, CA.