Bras, breast cancer & radon ( epidemiology study questioned)

["Bjorn Cedervall" <bcradsafers@hotmail.com>]

Bill Field (Iowa) has kindly provided me (and allowed me to post) the 
following below. Obviously the original paper was published a few years 
later than I thought (that is in 1996).

Also - check out:
http://www.junkscience.com/news/radon-breast-cancer.html

My ideas (and obviously that of others' too) are reflected here,

Bjorn Cedervall     bcradsafers@hotmail.com
------------------------------------
Radon and Breast Cancer
Risk Analysis 1997;16:729-730

A recent letter in Risk Analysis presents an hypothesis concerning radon 
(progeny) as a possible risk factor for breast cancer." In addition to 
plateout on synthetic clothes-including brassieres-which the authors 
discuss, radon is fat soluble and can deliver an internal dose to breast 
tissue. (" The authors do not discuss the many risk factors for breast 
cancer including family history, high socioeconomic status, age at 
pregnancy, and obesity.") These factors can change over time, thus 
influencing the reported increase in breast cancer. In addition, improved 
case finding can also be a factor in the reported increase.

The authors also present a cancer map which shows some positive qualitative 
relationship between breast cancer mortality and EPA radon zones. Mortality 
is not an adequate indicator of risk for this disease; incidence data are 
preferred, but are not available for the entire United States.

In order to determine the association between radon levels and breast cancer 
incidence, we examined data from Iowa, a state with the highest mean radon 
screening level and the highest percentage of homes in the U.S. with radon 
screening measurements exceeding the EPA guideline of 148 Bq/ml (4 pCi/L). 
This amounts to 71% of homes exceeding this guideline as measured in the 
lowest livable area (unfinished or finished basement or first floor) using a 
random survey. The methodology of this analysis was similar to that 
described elsewhere.(4)

Population data for White female residents of each county in the state of 
Iowa were obtained from the U.S. Census Bureau for the 1980 and 1990 
periods. Intercensal estimates were also provided by the census bureau for 
the years 1973-1979, 1981-1989, and 1991-1993.

Breast cancer cases were identified through the State Health Registry of 
Iowa, a member of the National Cancer Institute's Surveillance, 
Epidemiology, and End Results (SEER) Program since 1973. Eligibility was 
restricted to newly identified in situ and invasive breast cancers diagnosed 
between 1973 and 1993 among White female residents of the state of Iowa.

Residential radon data were obtained from randomly selected homes whose 
occupants participated in either a joint U.S. Environmental Protection 
Agency/ Iowa Department of Public Health radon screening survey conducted in 
the first half of 1989. All radon measurements were obtained from a single 
detector placed in the lowest livable area of the home during the winter. 
Open-faced charcoal canisters were deployed for 2 days at each site. Radon 
measurements were assigned to a county using the residential address. After 
counties with fewer than ten radon readings were excluded from the analysis, 
77 counties remained out of the original 99.

Age-adjusted breast cancer incidence rates for 1973-1993 were calculated 
directly for each of the three groupings of counties. The standard 
population was the 1970 U.S. population divided into 5-year age groups. The 
95% confidence interval was then calculated in order to determine 
statistical significance. The rates were stratified into low (<8 pCi/L), 
medium (8-10 pCi/L), and high (>10 pCi/L) radon levels. Arithmetic mean 
values of radon were utilized.

Results are presented in Table 1. A total of 32,171 cases are distributed 
across 1732 radon readings. Despite an 83% increase in average radon level, 
there is no increase in invasive breast cancer risk in the highest radon 
counties of Iowa. None of the results were statistically significant. There 
was no dose response trend (i.e., no increased risk as radon levels 
increased). Separate analysis for in situ breast cancer revealed identical 
conclusions.


Table 1. Age-Adjusted Incidence Rates for Invasive Breast Cancers
in 77 Iowa Counties (White females, 1973-1993, stratified by radon levels)

//The table didn't follow my copy-paste action but the following (next 2-3 
lines) are the table head texts. Comment by Bjorn Cedervall//

Radon level  Number of counties  Number of radon readings  Average radon 
reading(a) Number of breast cancer(b) cases Breast cancer incidence rates(c)

<8   24 600 6.9  11,357 93.9
8-10 23 545 8.9  9.748  92.2
>10  30 587 12.6 11,066 93.9

(a) pCi/L.
(b) Invasive breast cancer.
(c) Per 100,000 per year. Age adjusted to the 1970 U.S. Standard Population.

It is recognized that descriptive epidemiology is hypothesis-generating and 
that an analytic design would give more refined data on radon exposure and 
would include data on other risks factors for breast cancer. An annual 
average for radon is a preferred measurement compared to a short-term 
reading (e.g., 2 days). The same comments apply to the letter mentioned 
above. Regardless, these Iowa data do not support the hypothesis that radon 
increases the risk of breast cancer.

REFERENCES

P. M. Kildea, Jr. and T. C. Lee, "Radon Plateout on Synthetic Fibers as a 
Possible Risk Factor in Breast Cancer" (letter), Risk Analysis 16(l), 1-2 
(1996).
N. H. Harley and E. S. Robbins, "Rn-222 Alpha Dose to Organs Other Than 
Lung," Radiation Protection Dosimetry 45(1-4 Suppl.), 619-622 (1992).
J. L. Kelsey, "Breast Cancer Epidemiology: Summary and Future Directions," 
Epidemiologic- Reviews 15(l), 256-263 (1993).
J. S. Neuberger et al., "Residential Radon Exposure and Lung Cancer: 
Evidence of an Urban Factor in Iowa," Health Physics 66(3),263-269 (1994).

John S. Neuberger
University of Kansas
School of Medicine

R William Field
University of Iowa
College of Medicine












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