US EPA

1433581 

Journal Article 

Occupational Exposure to Radon Daughters in Mammoth Cave National Park 

Eheman, C; Carson, B; Rifenburg, J; Hoffman, D 

1991 

Yes 

Health Physics
ISSN: 0017-9078
EISSN: 1538-5159 

NIOSH/00201473 

60 

6 

831-835 

A study of occupational exposures to radon daughters in Mammoth Cave National Park, Kentucky, was conducted. The cohort consisted of 454 persons employed at Mammoth Cave between 1976 and 1986. These included 256 tour guides, 61 maintenance workers, and 108 special projects workers. The tour guides were usually seasonal workers. The maintenance workers were permanent employees. The special projects workers usually worked for one season only on projects such as repairing trails in caves. Employment records of cumulative exposures to radon daughters were examined. Data on radon-222 (Rn-222) daughter levels measured during 1976 to 1989 were reviewed. Rn-222 daughter concentrations inside the caves averaged 2.8 kilobecquerels per cubic meter (kBq/m3) from 1976 to 1989. The concentrations were highest in the fall and lowest in the summer. Mean cumulative exposures for the tour guides, maintenance workers, and special project workers over the study period were 3.69, 4.38, and 0.99 working level months (WLM), respectively. The mean exposure rate for all Mammoth Cave employees in 1986 was 1.09WLM per year (WLM/yr). Rn-222 daughter exposures experienced by Mammoth Cave employees were comparable to those of experienced by employees in other state or federally owned caves. The authors recommend that new exposure limits be developed for National Park Service employees who work in caves. Possible ways of reducing Rn-222 daughter exposure include limiting the length of tours in the caves, reducing the number of cave guides, and rotating employees between jobs above and below ground. 

DCN-201344; Occupational exposure; Radiation exposure; Radon daughters; Ionizing radiation; Uranium miners; Work environment; Radiation measurement; Workplace monitoring; Seasonal factors; Maintenance workers