In the miners, about 40% of all lung cancer deaths may be due to radon progeny exposure, 70% of lung cancer deaths in never-smokers, and 39% of lung cancer deaths in smokers. In the United States, 10% of all lung cancer deaths might be due to indoor radon exposure, 11% of lung cancer deaths in smokers, and 30% of lung cancer deaths in never-smokers. This risk model estimates that reducing radon in all homes exceeding the U. S. Environmental Protection Agency's recommended action level may reduce lung cancer deaths about 2%-4%. These estimates should be interpreted with caution, because concomitant exposures of miners to agents such as arsenic or diesel exhaust may modify the radon effect and, when considered together with other differences between homes and mines, might reduce the generalizability of findings in miners.

Protection standards for radon should continue to be based on consideration of the lung cancer risk alone.

No abstract

Two U.S. surveys suggested that dental hygienists (DHs) may suffer from carpal tunnel syndrome (CTS), but these studies did not use validated questionnaires, adjust for confounders, or include external controls. We conducted a questionnaire survey of all 2,142 DHs belonging to the Ontario Dental Hygienists' Association, and a referent group of 305 dental assistants (DAs), who do not scale teeth. The Standardized Nordic Questionnaire was used as the basis for asking about musculoskeletal symptoms. The response rates in the two groups were identical. Of the DHs, 7.0% had been told by a physician since starting work that they had CTS, but only 1 of 65 had received workers' compensation. Compared to the DAs, after adjusting for age the DHs were 5.2 times (95% confidence interval [CI] 0.9-32) more likely to have been told they had CTS and 3.7 times (95% CI 1.1-11.9) more likely to meet a CTS case definition. The DHs were also 2.5 (95% CI 1.6-3.9), 2.8 (95% CI 1.8-4.4), and 1.8 (95% CI 1.2-2.7) times more likely to report hand/wrist, shoulder, and neck problems in the past 12 months, respectively, but were less likely to report low back trouble. In internal analyses among DHs using logistic regression models, the number of heavy calculus patients per day, "clock" position around the dental chair, and years in practice were significant predictors of CTS. Days worked per week (but not heavy calculus patients), time with the trunk rotated, and years of practice were significant predictors of reported shoulder trouble in the past 12 months. Given that there are more than 9,000 DHs in Canada and about 100,000 in the United States, these findings suggest an important public health problem. They highlight the need to inform DHs during training and continuing education about musculoskeletal problems in general and CTS in particular. Attention should be directed to areas such as work station design, posture, treating patients with heavy calculus, and scheduling rest periods.

Some recent estimates of lung cancer risk from exposure to radon progeny in homes have been based on models developed from a pooled analysis of 11 cohorts of underground miners exposed to radon. While some miners were exposed to over 10,000 working level months (WLM), mean exposure among exposed miners was 162 WLM, about 10 times the exposure from lifetime residence in an average house and about three times the exposure from lifetime residence at the "action level" suggested by the U.S. Environmental Protection Agency. The extrapolation of lung cancer risk from the higher exposures in the miners to the generally lower exposures in the home is a substantial source of uncertainty in the assessment of the risk of indoor radon. Using the pooled data for the miners, analyses of lung cancer risk were carried out on data restricted to lower exposures, either <50 WLM or <100 WLM. In the pooled data, there were 115 lung cancer cases among workers with no occupational WLM exposure and 2,674 among exposed miners, with 353 and 562 lung cancer cases in miners with <50 WLM and <100 WLM, respectively. Relative risks (RRs) for categories of WLM based on deciles exhibited a statistically significant increasing trend with exposure in each of the restricted data sets. In the restricted data, there was little evidence of departures from a linear excess relative risk model in cumulative exposure, although power to assess alternative exposure-response trends was limited. The general patterns of declining excess RR per WLM with attained age, time since exposure and exposure rate seen in the unrestricted data were similar to the patterns found in the restricted data. Risk models based on the unrestricted data for miners provided an excellent fit to the restricted data, suggesting substantial internal validity in the projection of risk from miners with high exposures to those with low exposures. Estimates of attributable risk for lung cancer (10-14%) in the U.S. from residential radon based on models from the unrestricted data were similar to estimates based on the data for miners receiving low exposures.