I. The Issue:
Radon is a naturally occurring odorless radioactive gas commonly found in association with granite based rock formations. Prolonged inhalation of elevated levels of radon gas may cause lung cancer in humans.
Due to the preponderance of granitic bedrock in Massachusetts, we knew that the evolution of radon gas was likely in Burlington. In addition, while surveying the local schools we observed that each school was constructed with a sandy bottom crawl space rather than a sealed concrete slab or foundation. As a result, there existed the possibility that ledge may be present under the crawl space and that radon could enter the schools via the crawl space and adversely impact the indoor air quality.
II. The approach taken:
In an effort to evaluate for this potential hazard, we screened each school for radon using eight to twelve perforated charcoal sampling canisters which were placed in the school for 48 hours. Half the canisters were placed in the crawl space and half were placed in classrooms. The sampling canisters were placed in areas which were free of moisture, drafts, and were located away from the heating and ventilation system. The canisters were left undisturbed during the 48 hour test period. This strategy was utilized as a means to assess the worst case scenario (crawl space) and actual potential occupational exposure (classroom) in each building. We conducted our tests during the winter heating season when fresh air exchange was minimized and radon concentrations could conceivably build up to their highest levels. In addition, we also wanted to note what effect the heating system may have on pressurizing the building and thereby potentially creating a vacuum which could promote the introduction of radon into the building.
III. Observations made:
Fortunately, the majority of the samples analyzed were below the EPA action level of 4 picoCuries of radon per liter of air (4.0 pCi/L). Elevated concentrations were detected initially at several locations, however re-analysis failed to detect elevated concentrations at these locations. Based on this information there does not appear to be a radon concern at any of the local schools.
One concern we noted is that nearby blasting or construction could fracture the local bedrock or a school foundation and create a new pathway for radon migration. As a result, a radon problem could develop at a future date, consequently continued vigilance is required to monitor for this potential problem. Nearby blasting or the discovery of new cracks in the foundation should serve as a warning that additional radon sampling may be necessary.
Tips and suggestions:
1. Before beginning a radon assessment, you should review local geological conditions and existing sampling data to determine if radon is known or believed to be a problem in your community. State and federal environmental agencies and geological surveys may be able to assist this effort.
2. The following potential pathways may make your school susceptible to the introduction of radon: dirt or rock foundation, cracks or holes in the foundation, a sump pump, a drain discharging to a drywell, and well water. In addition, if the heating and ventilation system pressurizes the building, then it may be possible for the operation of this system to enhance the introduction of radon into the building via these openings.
3. If radon is known to be a potential problem in your area, then efforts should be initiated to seal the obvious potential migration pathways to hinder the ability for radon to enter your school. This may be impossible in some areas such as a dirt or stone foundation or crawl space. If elevated radon concentrations are detected then additional ventilation may be required for the locations which cannot be easily sealed.
4. Radon testing should be conducted under the worst case scenario when the building is sealed and fresh air exchange is minimized. The introduction of fresh air via drafts or the ventilation system may lower the radon concentrations and cause you not to detect the highest concentration present in the building.
5. Before initiating expensive remedial measures, re-sample to confirm that elevated concentrations do exist. Sampling errors can occur. Don't compound one error with a more expensive one. Also, check to make sure that another radioactive source is not present in the test area, especially if you are sampling a science classroom or ceramics studio where radioactive materials may be present.
6. Remember to monitor local development because nearby blasting and construction may cause new fractures in your foundation or bedrock and create a new pathway for radon to enter your school. As a result, periodic testing may be required if development is occurring in the vicinity of your school.
I utilized the guidance and resources offered by the Massachusetts Departments of Environmental Protection, and Public Health, the U.S. Environmental Protection Agency, and the U.S. Geological Survey to assist with the completion of our evaluation. Due to the regional differences in geology and building construction, I encourage you to contact your state environmental and public health agencies in addition to your regional About Region 7 and USGS offices for a more accurate description of the conditions and concerns of your area. In addition, these agencies have prepared a wealth of information describing the hazards associated with radon as well as how to screen for and resolve problems associated with the build up of radon gas.
prepared by Todd H. Dresser, Environmental Engineer
Burlington Board of Health, 29 Center Street, Burlington, MA 01803