Radiation Biology and Carcinogenesis

• Evaluate experimental evidence on inverse dose-rate relations and its implications.

• Attempt to correlate risks of radon-induced lung tumors with those of tumors induced by external exposure to low-LET radiation.

• Examine in more detail the induction and repair of molecular changes after exposure to alpha particles.

Exposure-Dose Relations

• Gain access to additional information that is relevant to radon dosimetry from the use of noninvasive methods for monitoring ventilation and from an improved model.

• Use activity-weighted size-distribution data that have become available on residences.

• Use the recent data on growth of particles from various sources typically found in homes.

• Use biologic dosimetry to reduce the uncertainties associated with the exposure-dose relationship and apply the reduced uncertainties in various aspects of lung dosimetry to risk calculations.

Studies of Miners

• Critique the recently completed analyses of pooled data on 11 cohorts and whatever new risk models emerge from them and use the database to suggest additional analyses.

• Model the pooled data with emphasis on biologically-driven modeling.

• Formally evaluate sources of exposure error in the miner cohorts and the consequences of those errors for risk estimation and risk assessment.

Studies of Lung Cancer in the General Population

• Evaluate and interpret the results of completed case-control and ecologic studies, including evaluation of their limitations and uncertainties.

• Determine the appropriate role of case-control studies in developing a risk model of residential exposure to radon.

• Make general recommendations regarding the potential role of case-control studies that are not yet complete.

• Estimate the statistical power of the completed studies for various end points as a group and identify the expected upper and lower confidence limits according to the assumptions of the recommended model and alternative models.

• Estimate the potential of the completed studies for providing information on the modifying effects of smoking and other factors, taking into account uncertainties in exposure estimates.

• Make recommendations on the desirability of initiating new case-control or ecologic studies of residential radon exposure.

Modifications to the Phase 1 Recommendations

• Assess the validity and scientific reliability of analytic approaches used by various investigators.

• Examine in detail the interaction between radon exposure and cigarette-smoking on the basis of data on US and other miners.

• Reexamine the effect of the rate of exposure to radon on the incidence of lung-cancer.

• Critically examine exposure estimates for miner cohorts and reassess the consequences of the exposure rates.

• Propose, in light of the phase 1 findings, a mathematical model of risk based on more complete and up-to-date U.S. and international miner data.