Recognizing Radon Gas Concerns

By Scott A. Summers



Since the mid-1980s, radon testing has become commonplace in the residential transaction process, particularly throughout much of the state of Maryland and Howard County. But radon testing has remained relatively scarce in the commercial real estate market, despite today's shift in environmental focus toward indoor air quality issues like "Sick Building Syndrome" and concerns surrounding mold. Yet, builders, developers and owners should consider that any building can exhibit a radon problem, whether the structure is new or old, well or poorly sealed, does or does not contain a below-grade level. The potential for radon gas to accumulate within a building at elevated levels is largely dependent on factors such as local geologic conditions and the building construction type. Owners and investors in real estate alike may wish to consider the possible risks associated with neglecting to evaluate whether future or

existing building occupants may be exposed to radon gas at levels posing a health concern.



What is Radon Gas?

Radon is a naturally occurring gaseous substance resulting from the decay of uranium to radium and then to radon. Uranium is a common element occurring in many rock units, particularly igneous and metamorphic rocks and to lesser degrees in sedimentary and unconsolidated sedimentary rocks. Radon is both colorless and odorless, has a half-life of only 3.8 days, and decays to several daughter elements.

Radon gas levels are directly influenced by the natural uranium concentration in the rock or unconsolidated soils and their associated permeability (a measure of how easily gas and water migrate through a medium such as soil particles). Radon migrates upward or along paths of greatest permeability and accumulates in below-grade portions of buildings where air circulation is restricted or directly beneath the building footprint.

Radon typically migrates into buildings through cracks in below-grade walls or floor slabs, but can also follow openings through building foundations such as sumps and unsealed utility penetrations. Radon gas also dissolves readily in ground water; therefore, water withdrawn from wells has the potential to release radon gas to an indoor environment. Radon is considered a potential health risk once it has migrated into a building and is subsequently inhaled by building occupants.



What Are the Health Effects of Radon Gas Exposure?

Although some debate exists over what radon gas levels translate into increased risk of lung cancer, the Environmental Protection Agency (EPA) and all major national and international organizations concur that there is no debate about radon being a lung carcinogen to humans. The World Health Organization (WHO), the EPA and the United States Department of Health and Human Services have classified radon as a "Class A" known carcinogen, based on a wealth of biological and epidemiological evidence and data showing the connection between exposure to radon and lung cancer in humans.

The EPA and the Surgeon General have estimated that between 15,000 and 22,000 lung cancer deaths each year in the United States are caused by radon exposure, making it second only to smoking as the leading cause of lung cancer in the United States. The latency period for lung cancer due to radon gas exposure is estimated at five to 25 years, with the highest risk groups being those who smoke and are exposed to elevated radon concentrations. In addition, the EPA maintains that there is no scientific evidence that children or the elderly are at any greater risk of radon induced lung cancer than adults.



How Do I Know If I Have a Radon Gas Concern?

The EPA has published a "Map of Radon Zones," which assigns each of the 3,141 counties in the United States to one of three zones based on radon potential. The majority of counties within Maryland (with exception of the eastern shore) are designated as Zone 1 or 2 and have the highest average indoor radon levels. In addition to the "Map of Radon Zones," the EPA has published radon test results for the State of Maryland, which was compiled in 1997. This document, entitled, "Maryland Radon," provides a statistical summary of radon readings for each zip code in the state.

Testing is the only way to determine if an existing or future building has or will have a radon problem. A qualified and experienced professional should perform the radon gas testing and evaluation. Radon testing to address future development concerns can be performed through in-ground test procedures. Indoor testing can also be conducted for evaluating the radon gas potential within existing structures. Radon tests are typically considered either "short-term," accomplished in less than 30 days, or "long-term," lasting over 30 days. Radon test devices are either placed within the proposed building footprint or at the lowest existing floor level one might occupy. In addition to testing, an evaluation of the existing building components and structure type should be considered to identify possible points or areas of radon gas entry into the building.

Radon testing and evaluation surveys are relatively inexpensive, with each individual test kit costing approximately $25. The extent of radon testing and strategies for performing "short-term" versus "long-term" tests can vary and should be discussed with a qualified professional. Although test kits usually come complete with "easy-to-do" instructions, it is not recommended that an owner undertake such a study independently. Radon concentrations can be significantly affected by a number of factors, including meteorological and seasonal conditions.



What If Radon Gas Exists Within My Building?

A hazard or risk evaluation should be performed in the event that testing identifies radon gas as a potential concern to new development or within an existing building. Once a radon gas risk has been identified, there are several mitigation options to choose from, including active and passive sub-slab ventilation systems, block wall and drain tile depressurization, fan installation and implementation of other engineering controls.

Whether you're a developer or an owner, the evaluation and/or mitigation of radon gas should be considered in the initial planning of a project or property transaction. The process and costs associated with identifying potential hazards such as radon and controlling those hazards are typically performed at low costs and can be far more expensive in the later stages of development or investment if such issues are not addressed in early stages.



Scott A. Summers is a senior project manager and registered professional geologist of Engineering Consulting Services, Ltd. He can be reached at 410-859-4300 .