Environmental Engineering Reference
In-Depth Information
Chinese tin (L10)
Port radium (H35)
Colorado (H17,L10)
Newfoundland fluorspar (V4)
Ontario (K12,K13,L10)
French (R10,F30)
Swedish (R2,L10)
Beaverlodge (H35)
Czech (B9)
Combined
0.1
0.2
0.5 1
Excess relative risk (100 WLM) -1
2
5
10
FIGURE  21.7  Underground miner lung cancer risk estimates from 11 follow-up cohort studies. (From
UNSCEAR, Sources-to-Effects Assessment for Radon in Homes and Workplaces , United Nations Scientiic
Committee on the Effects of Radiation, New York, 2006.)
meta-analyses are shown in Figure 21.8. Residential risk can be calculated without reliance on
underground miner risk projections.
The residential risk from pooled studies is similar to the mine studies with an ERR of 0.16 for
lifetime exposure to 100 Bq m −3 . This is equal to an ERR of about 0.01 WLM −1 but depends on
the years assumed for exposure in a residence. An important conclusion from both the residential
(Darby et al., 2005) and miner studies (Schnelzer et al., 2010) is that the ERR is the same for both
smokers and nonsmokers. The much higher lifetime lung cancer risk in smokers is due to the higher
baseline lung cancer rate, the ERR multiplying the baseline.
21.13  GUIDELINES FOR INDOOR  222 RN
Based on the domestic radon surveys conducted in many countries, both NCRP and ICRP have
set guidelines for indoor radon concentrations (NCRP, 1984a,b, 2003; ICRP, 2007). NCRP
recommended that lifetime exposure to individuals above an annual rate of 2 WLM, including
background, be avoided. Using the average value for the equilibrium factor, Feq, of 40%, 2 WLM
equals exposure to 370 Bq m −3 (10 pCi L −1 ) from all sources. ICRP (2007) recommends an upper
reference level of 600 Bq m −3 for domestic dwellings and 1500 Bq m −3 for workplaces. The ICRP
(2007) reference levels are undergoing review and may be reduced. The U.S. EPA recommends a
domestic concentration 150 Bq m −3 (4 pCi L −1 ) and Canada recommends 750 Bq m −3 (20 pCi L −1 ).
21.14  SUMMARY
All atmospheres contain radon. Based on 60 countries, the global indoor residential average is
55 ± 30 Bq m −3 (1.5 ± 0.8 pCi L −1 ). The estimate for the U.S. residential average is 46 Bq m −3 . An EPA
survey of outdoor radon in all 50 U.S. states determined an average of 15 Bq m −3 at ground level.
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