Below you will find printable copies of the Home Radon Survey, Phases I & II, organized by county. Within each report, you will find reported radon levels sorted by city and zip code.
HOME RADON SURVEYS. PHASE I AND PHASE II SUMMARY
The Arizona Radiation Regulatory Agency (ARRA), in cooperation with the U. S. Environmental Protection Agency (EPA), initiated a program to measure radon concentrations in homes. The survey was conducted in response to the growing concern about potential health risks associated with indoor radon exposure. The primary goal of the home indoor radon survey was to determine the statewide distribution of radon in homes and identify areas of potentially high radon concentrations.
During the winter and spring of 1987-88, ARRA and EPA conducted Phase I, a population-based home radon survey in Arizona. ARRA completed a follow-up, Phase II, during the winter and spring of 1988-89. The state legislature provided funds for the purchase of laboratory equipment, charcoal canisters, salaries for part-time employees for Phase I, and miscellaneous administrative expenses. Without these funds, the Agency could not have participated in the EPA survey or accomplished Phase II.
During Phase I, ARRA purchased analytical equipment specifically for radon analysis. The ARRA laboratory developed procedures to analyze charcoal canisters for radon, and successfully participated in the EPA Radon Measurement Proficiency Program (RMP). The laboratory is listed in the National RMP Report as a proficient, non-commercial laboratory for the analysis of radon.
An activated carbon absorption technique was selected for the evaluation program because the measurement method is simple and comparatively inexpensive. A charcoal canisters was placed in a home for a period of 48 hours. To ensure the discovery of any existing high radon concentration within a home, the program called for the charcoal canister to be exposed under closed-house conditions. Canisters were placed in the lowest livable level of the home, where readings would typically be the highest. Therefore, the estimates of indoor radon concentrations obtained from the survey would likely reflect a worse-case scenario. Residences with high radon concentrations were identified. Results from these short-term tests, conducted under closed-house conditions, do not necessarily reflect a true annual average radon concentration.
In addition to exposing a charcoal canister on the lowest livable level in the home for 48 hours, ten percent of the homes received two to four Alpha-Track Detectors (ATD's). The ATD's were to be exposed for a twelve-month period. Information collected from the long-term measurement would permit the assessment of the relationship between long-term and short-term measurements. From this comparison, estimates of annual average residential radon levels could be determined. These estimates would more clearly describe potential health risks than the two-day screening measurements taken on the lowest livable level of the home under closed-house conditions.
The participants in the ARRA/EPA Phase I survey completed a brief telephone interview, which was related to determining their survey eligibility. Phase II participants were interviewed for eligibility at the local level by county health personnel working in cooperation with ARRA. All participants were then provided with a charcoal canister and requested to deploy it in their home, following the instructions provided. They were also requested to complete a short questionnaire that was enclosed in the package with the canister. The package containing the completed questionnaire and the exposed canister were to be mailed to the ARRA laboratory, for processing.
2,619 charcoal canisters were issued for Phase I. 2,079 were returned to ARRA for analysis.
The number of homes with ATD's returned for analysis was 170. The ATD home charcoal canister average was 0.992 pCi/L and the ATD average results were 0.889 pCi/L. Only two of the ATD homes had an annual average above 4.0 pCi/L, whereas the short-term, charcoal canister tests had indicated five of those homes exceeded 4.0 pCi/L.
The arithmetic mean of all homes sampled in Phase I was 1.6 pCi/L. The survey data estimates that 6.6 percent of the homes in Arizona will exceed 4.0 pCi/L and approximately 0.1 percent will exceed 20 pCi/L.
Phase I survey results indicated that Arizona indoor home radon concentrations can exceed the recommended action level of 4 pCi/L in many areas of the state. Arizona is among the lowest for radon levels observed, when compared with other states. The survey identified several areas throughout the state where home radon levels have the potential for causing potential health hazards. Some of these suspect areas are Prescott, (Granite Dells Area), southwest Tucson, Cave Creek, Carefree, Verde Valley, Flagstaff and Payson.
The Phase II survey targeted elevated areas identified in Phase I, areas where geological features indicated higher radon potential, locations not well covered in Phase I, and areas recommended by county health authorities. The results of Phase II closely correlate with data obtained in Phase I.
The Phase II survey showed that 9.9 percent of the homes tested exceeded 4.0 pCi/L, including 0.89 percent above 10.0 pCi/L, and only 0.18 percent above 20.0 pCi/L. ARRA provided canisters to the counties for distribution to survey participants. 1,314 canisters were issued for the Phase II survey. 1,119 were returned for analysis.
The number of Phase I survey results used for statistical analysis by EPA, by county, were: Apache 15, Cochise 39, Coconino 89, Gila 13, Graham 29, Greenlee 8, La Paz 2, Maricopa 765, Mohave 99, Navajo 57, Pima 260, Pinal 33, Santa Cruz 13, Yavapai 51, Yuma 34 (Total: 1507).
The Environmental Protection Agency and the U. S. Surgeon general have determined that radon is the second greatest cause of lung cancer in the United States. EPA strongly recommends testing of all homes, schools, and public facilities for the presence of radon. ARRA concurs with that recommendation.
Radon has become a significant health concern nationally and will continue to be a problem until it is controlled within the indoor environment. A major goal of ARRA is to develop an effective and comprehensive long-term indoor radon surveillance and mitigation program. Objectives to be accomplished include:
- Provide increased information programs to the general public.
- Present lectures to interested organizations.
- Conduct mitigation courses in conjunction with EPA.
- Through geological surveys, identify and define the geological impact for radon in air and water.
- Acquire laboratory capability to complete statewide studies for radon in air and water.
- Provide assistance to schools for radon surveys and mitigation.
- Investigate the radon potential in public facilities.
- Promote adoption of the model building codes developed by EPA.
- Develop regulations for the radon industry in Arizona.