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Background: Metalworking fluids (MWF) are used for lubrication during metal manufacturing. Previous studies have observed increased risks of several cancers among MWF-exposed workers. We hypothesized that MWF may be associated with risk of breast cancer because they can contain carcinogenic or endocrine-disrupting chemicals., Methods: We conducted a case-control study nested in a cohort of 4,680 female automobile workers employed for at least 3 years between 1/1/41 and 1/1/85, with follow-up through 1994. Cases were identified using the National Death Index (NDI), Michigan cancer registries, and company records. Detailed quantitative MWF exposure data were available for each subject, although data on known breast cancer risk factors were not., Results: Ninety-nine cases of breast cancer and 626 matched controls were identified. There was a weak positive association between lifetime cumulative exposure to soluble MWF and breast cancer risk, but no evidence of association with either straight or synthetic fluids. When exposure was divided into time-windows, the association was strongest for soluble MWF in the decade preceding diagnosis. Controlling for earlier exposures, there was an odds ratio of 1.18 (95% CI=1.02-1.35) per mg/m3-year of cumulative exposure to soluble MWF in this 10-year period., Conclusion: This hypothesis-generating study provides some preliminary evidence for an association between exposure to soluble MWF and increased risk of breast cancer. Additional studies of MWF and breast cancer, with data on known breast cancer risk factors, are warranted.

Purpose: To determine whether cumulative daily average wet-bulb globe temperature (WBGT) index, over one or two preceding days, is a better measure for predicting cases of exertional heat illness (EHI) than current daily average WBGT, which is the standard heat index used by the Marine Corps; and to identify the most accurate index of heat stress to prevent and predict future cases of EHI., Methods: A case-crossover study was conducted in male and female Marine Corps recruits in basic training at Marine Corps Recruit Depot, Parris Island, SC. Weather measurements were obtained for 2069 cases of EHI during 1979-1997 and for randomly selected control periods before and after each EHI episode., Results: The risk of EHI increased with WBGT (OR = 1.11 degrees F(-1); 95% CI, 1.10-1.13). EHI risk was associated not only with the WBGT at the time of the event (OR = 1.10 degrees F(-1); 95% CI, 1.08-1.11) but with the previous day's average WBGT as well (OR = 1.03 degrees F(-1); 95% CI, 1.02-1.05). Alternative combinations of WBGT components were identified that better predicted EHI risk., Conclusion: Our results provide evidence for a cumulative effect of previous day's heat exposure on EHI risk in these Marine Corps recruits. A simple index for use in predicting EHI risk is proposed that includes the dry-bulb temperature and the relative humidity.

Background: Uncontrolled confounding by personal exposures like smoking can limit the inferential power of occupational cohort studies. We developed and demonstrate a refinement of an existing type of sensitivity analysis, indirect adjustment, for evaluating the potential magnitude of confounding by alcohol and tobacco. Results of a large retrospective cohort study of laryngeal cancer and exposure to metalworking fluids (MWF) are used to illustrate the methods., Methods: Data on smoking and drinking habits representative of the study cohort were obtained from a sample of US manufacturing workers from the 1977 National Health Interview Survey (NHIS). Two different mechanisms were assumed to affect the distribution of confounding factors between MWF exposure groups: socially determined and chance differences. Chance variation was investigated with Monte Carlo sampling from the NHIS survey distribution of smoking and drinking. An upper bound on systematic differences in smoking and drinking was set by assuming that differences between exposure groups within the same unionized blue collar workforce were very unlikely to be larger than differences between blue and white collar manufacturing workers in the NHIS data., Results: Under plausibly large differences in smoking and drinking habits among MWF exposure groups occurring by either mechanism, the exposure-risk association was unlikely to have been over- or under-estimated by as much as 20%., Conclusions: When comparing exposure groups within the same working population, it is unlikely that either systematic or chance differences in smoking and drinking habits will cause as much as a 20% change in the relative risk in large studies. While this study focused on an occupational exposure and laryngeal cancer, there are many situations in which epidemiologists are concerned that unmeasured 'lifestyle factors' may differ among exposure groups, and it would appear that the likely confounding effect of such differences will often be modest.

Objectives: Several studies have shown a relation between smoking and suicide. It is not clear if this relation should be considered causal, or if other risk factors for suicide, left unmeasured in many studies, might explain the smoking-suicide association. The aim of this cohort study was to analyse the role of smoking and other potential risk factors measured in adolescence on subsequent suicide., Methods: Information on smoking, and other potential risk factors from childhood and adolescence was collected among 49 323 men, born 1949-1951, at conscription for compulsory military training in the years 1969-1970. Mortality data were obtained from the Swedish cause of death register for the years 1971-1996., Results: There was a clear trend of increasing suicide risk with increasing intensity of smoking reported at conscription. Those smoking >20 cigarettes/day had a strongly increased relative risk of suicide (OR = 3.03, 95% CI: 1.72, 5.34) during the first 13 years of follow-up. From 14 to 26 years after conscription, the risk was only slightly weaker (OR = 2.53, 95% CI: 1.36, 4.72). When we adjusted for other risk factors for suicide measured at the conscription examination (psychiatric diagnosis, parental divorce, low emotional control, medication for nervous problems, contact with police and childcare, heavy alcohol consumption, drug use, and education) in a multivariate analysis, the trend with smoking intensity disappeared, and there was no longer an increased relative risk for the heavy smokers (follow-up years 1-13: OR = 0.98, 95% CI: 0.53, 1.82; years 14-26: OR = 1.31, 95% CI: 0.91, 1.87)., Conclusion: The increased risk of suicide among smokers was almost entirely explained by an increased prevalence of heavy alcohol consumption and low mental well-being among smokers. That is, the association between smoking and suicide is probably due to confounding by these other factors. These results do not support the hypothesis that tobacco consumption itself is a risk factor for suicide.

Objective: Meta-analysis was used to summarize the published evidence on the associations between alcohol and tobacco consumption and cancers of the oropharynx, pharynx, larynx, and esophagus. The objective was to produce summary risk estimates with uniform methods and on uniform exposure scales so that the magnitudes of the risks could be compared across tumor sites., Methods: Epidemiologic studies that estimated the effects of alcohol and tobacco consumption on the risk of cancers of the upper aero-digestive tract were identified from the MEDLINE database, 1966-2001. Alcohol and tobacco data were converted into common units (grams/week). For all studies meeting eligibility criteria, effect parameters (slopes) were estimated for both exposures. The exposure-risk slopes for each study were combined, site by site, using random effects meta-regression methods., Results: Fourteen studies met the final selection criteria. The carcinogenic effects of alcohol and tobacco were found to be multiplicative on the relative risk scale. Tobacco appeared to have a much stronger effect on the larynx than on any of the other aerodigestive sites, while alcohol's effect was strongest on the pharynx. The weakest association was that of alcohol and adenocarcinoma of the esophagus--an order of magnitude weaker than that for tobacco and laryngeal cancer., Conclusions: Meta-analysis was used to combine the results from all available studies, providing a comprehensive summary of the combined effects of alcohol and tobacco on the upper aerodigestive cancers.

Background: Among epidemiologic studies that found evidence for associations between exposures to metal working fluids (MWF) and pulmonary function impairments, one found effects restricted to workers with fixed obstruction at baseline. We reanalyzed a previously published study on MWF exposure and cross-shift pulmonary function to further evaluate this finding., Methods: Pulmonary function was measured cross-shift on Monday and Friday in 131 male automotive workers. Quantitative personal MWF exposure data were available. Those with an FEV(1)/FVC ratio of