In response to a request for information on indoor air quality problems, the U.S. Occupational Health and Safety Administration (OSHA) has proposed a rule addressing indoor air quality in general, and especially envir...
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In response to a request for information on indoor air quality problems, the U.S. Occupational Health and Safety Administration (OSHA) has proposed a rule addressing indoor air quality in general, and especially environmental tobacco smoke (ETS), in indoor work environments. As justification for the proposed rule, OSHA relies on a quantitative risk assessment used to provide estimates of lifetime risk of lung cancer and heart disease associated with workplace exposure to ETS. However, there are a number of concerns regarding the OSHA risk assessment. (i) The form of the underlying mathematical model used in the risk assessment is inappropriate. (ii) OSHA was highly selective in choosing what data values to use in their risk assessment. (iii) Many data values required as input to the OSHA risk assessment model are simply not known at this time. When such values are required, known, but possibly inappropriate, values were substituted. The conclusions arrived at by OSHA on the basis of this risk assessment seem unwarranted. (C) 1996 Academic Press, Inc.
We describe a method for modeling aggregation in a flowing fluid. In the model, aggregation proceeds by the accumulation of a “nutrient.” The nutrient is modeled using a lattice Boltzmann model of transport. The agg...
We describe a method for modeling aggregation in a flowing fluid. In the model, aggregation proceeds by the accumulation of a “nutrient.” The nutrient is modeled using a lattice Boltzmann model of transport. The aggregate absorbs the nutrient, and the amount absorbed determines the local growth probability. This model contains some of the essential features of growth of stony corals. We find that the morphology of the aggregates changes drastically as we increase the Péclet number from a regime where nutrient transport is diffusion controlled to a regime where hydrodynamic transport dominates. This is in qualitative agreement with the morphogenesis of stony corals.
A joint study on effects of formaldehyde exposure in industrial populations by the National Cancer Institute and the Formaldehyde Institute, Inc. (Blair et al. [1986]: J Natl Cancer Inst 76: 1071-1084;Blair and Stewar...
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A joint study on effects of formaldehyde exposure in industrial populations by the National Cancer Institute and the Formaldehyde Institute, Inc. (Blair et al. [1986]: J Natl Cancer Inst 76: 1071-1084;Blair and Stewart [1989]: J Occup Med 31: 881, Blair et al. [1990]: Am J Ind Med 17:683-700) reported no significant elevation in risk ratios standardized to the general population. Using the same data as Blair et al., we compared more exposed to less exposed workers to compute relative risk for respiratory and lung cancers using a multivariate, log-linear model incorporating factors for job type (hourly vs. salaried), cumulative exposure (0.1-0.5, 0.5-2, 2 + vs. <0.1 ppm/years), length of exposure (1-5, 5-10, 10 + vs. <1 years), and age. Models were fit for all workers, all males, all workers less than 65 years of age, and for all males less than 65 years of age. Hourly workers have a significantly elevated relative risk when compared to salaried workers. While only high levels of cumulative exposure show a significant elevation in relative lung cancer risk, trend analyses of the coefficients of a log-linear model show a significant trend of increasing risk with increasing formaldehyde exposure. The significantly elevated respiratory and lung cancer risk for workers younger than 65 may indicate a shift of respiratory cancer mortality towards younger ages among those occupationally exposed to formaldehyde. Coupled with the recent report of the American Cyanamid Company's Cohort Mortality Study that finds a significantly elevated lung cancer risk related to formaldehyde exposure of greater than or equal to 0.2 ppm and with Blair et al.'s finding of an elevated lung cancer risk ratio, the conclusion of an association between lung cancer and occupational formaldehyde exposure seems well supported. (C) 1994 Wiley-Liss, Inc.
The number of deaths that would not have occurred had an exposure or trait been absent is generally estimated by observing mortality rates in sample populations of exposed and nonexposed persons and applying them to t...
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The number of deaths that would not have occurred had an exposure or trait been absent is generally estimated by observing mortality rates in sample populations of exposed and nonexposed persons and applying them to the population of interest. Three methods used to estimate deaths due to tobacco use are evaluated. Each method requires estimates of certain absolute and relative risks, and the published estimates based on them assume that the absolute and relative risks observed in the two large American Cancer Society prospective studies can be applied to the US population or to populations in developed countries. Computations using large representative samples of US decedents and of the entire US population for these methods result in estimated numbers of deaths for the US population that are substantially lower than those based on Cancer Prevention Survey-I or Cancer Prevention Survey-II. Computations also showed that controlling for confounding from two smoking-related variables results in still lower estimates of the number of excess deaths. Consequently, published results that ignore confounding and are based on nonrepresentative data overstate the contribution of smoking. It is imperative that estimates of excess deaths be based on representative data and control for relevant confounders.
Between 1982 and 1988 a growth study was carried out at the Division of Pediatric Oncology of the University Hospital of Groningen. A special feature of the project was that sample sizes are small and that ages at ent...
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If the same information on the distribution of risk factors is available for both the general population and a subset distinguished by some disease outcome, it becomes possible to derive relative risk estimates applic...
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If the same information on the distribution of risk factors is available for both the general population and a subset distinguished by some disease outcome, it becomes possible to derive relative risk estimates applicable to the entire population with the assurance that the data upon which the estimates are based is representative of that population. To illustrate this approach, data from the 1986 National Mortality Followback Survey and the 1987 National Health Interview Survey were used to compute rate ratios for several causes of death for work in dirtier as compared with cleaner occupations by three methods commonly employed in cohort and case-control studies: the usual standardized rate ratio, the Mantel-Haenszel estimate of the rate ratio, and a multiplicative model fit to an appropriate cross-classification. Properly placed questions in appropriate surveys might very well serve as a substitute for cohort studies and could be performed at less cost and with less overall effort, and completed in a shorter time. Moreover, this approach is less subject to problems of representativeness than cohort and case-control studies.
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