Radon Levels in Pennsylvania and the Rise in Incidence of Thyroid Cancer

Abstract

Objective:

Determine if there is a temporal association between radon levels and the rise in incidence of thyroid cancer in Pennsylvania.

Methods:

Ecological study: The Pennsylvania Cancer Registry and the Department of Environmental Protection were used as data sources for this study for the years 1990-2009. From the registry, geographic information regarding thyroid incidence was recorded. Using SAS, Poisson regression models were fit predicting county level thyroid incidence and change as a function of radon/ lagged radon levels. To account for measurement error in radon levels, a Bayesian Model extending the Poisson models was fit using the winBUGS program.

Results:

Contour plots showing correlations between radon levels by year and yearly thyroid incidence rates failed to detect any association consistent with a causal connection. In the Poisson modeling, no significant association was noted between county radon level and thyroid cancer incidence (P = 0.23). Looking for a lag between the radon level and its effect, no significant effect was seen for a lag of 0 to 6 years between exposure and expected effect (P = 0.063 to P = 0.59). The Bayesian models fit also failed to show a statistically significant association.

Conclusions:

While there is evidence of rising levels of radon as well as thyroid cancer in Pennsylvania, the two do not correlate according to our analysis. Through a variety of models, no association could be elicited between radon levels in Pennsylvania and the rising incidence of thyroid cancer. Further studies, such as using an animal model, may be helpful in determining an association.