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The butter flavoring additive, diacetyl (DA), can cause bronchiolitis obliterans (BO) by inhalation. A risk assessment was performed using data from a microwave popcorn manufacturing plant.Current employees' medical history and pulmonary function tests together with air sampling over a 2.7-year period were used to analyze forced expiratory volume in 1 second (FEV1) and FEV1/forced vital capacity (FVC). The exposure responses for declining pulmonary function and for possible early onset of BO were estimated using multiple regression methods. Several exposure metrics were investigated; benchmark dose and excess lifetime risk of impairment were calculated.Forty-six percent of the population had less than 6 months exposure to DA. Percent-of-predicted FEV1 declined with cumulative exposure (0.40 per ppm-yr, P 10) as did percent FEV1/FVC (0.13 per ppm-yr, P = 0.0004). Lifetime respiratory impairment prevalence of one per thousand resulted from 0.005 ppm DA and one per thousand lifetime incidence of impairment was predicted for 0.002 ppm DA.DA exposures, often exceeding 1 ppm in the past, place workers at high risk of pulmonary impairment.

Invasive rainbow smelt (Osmerus mordax) have spread rapidly throughout inland lakes of North America with detrimental effects on several native fishes. To test for the potential to control this species, we conducted an experimental removal of rainbow smelt in Sparkling Lake, Wisconsin during 2002–2009. We combined intensive spring harvest of rainbow smelt with an effort to increase predation on this invasive through restricted angler harvest of walleye and increased stocking of walleye (Sander vitreus). Over 4,170 kg of rainbow smelt were harvested during the experiment; up to 93% of adults were removed annually. We observed a significant decline in rainbow smelt gillnet catches during the removal. However, rainbow smelt relative abundances began increasing upon cessation of the removal effort. Bioenergetics modeling suggested that despite achieving higher than the regional average walleye densities, walleye consumed only a fraction of the rainbow smelt standing stock biomass. Our findings suggest that removal of rainbow smelt from invaded lakes may be difficult, and reinforce the importance of prevention as a strategy to limit the expansion of this invasive fish.

Errors in the estimation of exposures or doses are a major source of uncertainty in epidemiological studies of cancer among nuclear workers. This paper presents a Monte Carlo maximum likelihood method that can be used for estimating a confidence interval that reflects both statistical sampling error and uncertainty in the measurement of exposures. The method is illustrated by application to an analysis of all cancer (excluding leukemia) mortality in a study of nuclear workers at the Oak Ridge National Laboratory (ORNL). Monte Carlo methods were used to generate 10,000 data sets with a simulated corrected dose estimate for each member of the cohort based on the estimated distribution of errors in doses. A Cox proportional hazards model was applied to each of these simulated data sets. A partial likelihood, averaged over all of the simulations, was generated; the central risk estimate and confidence interval were estimated from this partial likelihood. The conventional unsimulated analysis of the ORNL study yielded an excess relative risk (ERR) of 5.38 per Sv (90% confidence interval 0.54-12.58). The Monte Carlo maximum likelihood method yielded a slightly lower ERR (4.82 per Sv) and wider confidence interval (0.41-13.31).

Rainbow smelt (Osmerus mordax) are invaders of inland lakes in the Laurentian Great Lakes region of North America and have negatively affected native fish populations. Walleye (Sander vitreus) comprise an important fishery throughout the Great Lakes region and could be affected by rainbow smelt invasions. We test for declines of young-of-the-year walleye (YOY-W) density in 12 of the 26 known rainbow smelt invaded lakes in Wisconsin. Invaded lakes showed significantly lower YOY-W densities than uninvaded lakes during the period 1985–2004. In 94% (17/18) of years, YOY-W densities from invaded lakes were lower than those from uninvaded lakes. Declines (~70%) in YOY-W densities were observed in three lakes with data from before and after rainbow smelt invasion. For 10 invaded lakes with more than two YOY-W density estimates between 1985 and 2004, YOY-W densities averaged 13% below expected densities. Our results demonstrate the potential impacts of rainbow smelt invasion on walleye tribal, commercial, and recreational fisheries and highlight the importance of preventing their further spread.

We used creel surveys from 55 northern Wisconsin lakes during the period 1990–1999 to characterize the sport fishery for northern pike Esox lucius. The northern pike daily creel limit on all lakes was five fish of any size (no length limit). Creel surveys were conducted both during the open-water and ice fishing seasons. Directed effort (anglers specifically fishing for a certain species) for northern pike was 5.5 h/acre for open-water fishing and 3.9 h/acre for ice fishing. A greater percentage of all anglers directed effort toward northern pike during ice fishing (mean, 31%) than toward open-water fishing (mean, 11.9%). Directed catch rates for northern pike were highest during the open-water fishery. Open-water directed catch rates averaged 0.31 fish/h, compared with 0.20 fish/h for ice anglers. However, releases of living northern pike exceeded 80% during the open-water fishery but were less than 50% during the ice fishery, resulting in higher harvest rates for ice fishing. Ice fishing harves...

Variability in background risk and distribution of various risk factors for hearing loss may explain some of the diversity in excess risk of noise-induced hearing loss (NIHL). This paper examines the impact of various risk factors on excess risk estimates of NIHL using data from the 1968-1972 NIOSH Occupational Noise and Hearing Survey (ONHS). Previous analyses of a subset of these data focused on 1172 highly "screened" workers. In the current analysis, an additional 894 white males (609 noise-exposed and 285 controls), who were excluded for various reasons (i.e., nonoccupational noise exposure, otologic or medical conditions affecting hearing, prior occupational noise exposure) have been added 2066) to assess excess risk of noise-induced material impairment in an unscreened population. Data are analyzed by age, duration of exposure, and sound level (8-h TWA) for four different definitions of noise-induced hearing impairment, defined as the binaural pure-tone average (PTA) hearing threshold level greater than 25 dB for the following frequencies: (a) 1-4 kHz (PTA1234), (b) 1-3 kHz (PTA123), (c) 0.5, 1, and 2 kHz (PTA512), and (d) 3, 4, and 6 kHz (PTA346). Results indicate that populations with higher background risks of hearing loss may show lower excess risks attributable to noise relative to highly screened populations. Estimates of lifetime excess risk of hearing impairment were found to be significantly different between screened and unscreened population for noise levels greater than 90 dBA. Predicted age-related risk of material hearing impairment in the ONHS unscreened population was similar to that predicted from Annex B and C of ANSI S3.44 for ages less than 60 years. Results underscore the importance of understanding differential risk patterns for hearing loss and the use of appropriate reference (control) populations when evaluating risk of noise-induced hearing impairment among contemporary industrial populations.

Many species of fish make seasonal movements among geographic areas. Management of such mobile populations is often hindered by lack of knowledge of the patterns and rates of movement among the areas. In northern Wisconsin, spring population estimates (PEs) of walleyes Stizostedion vitreum are used in managing the joint tribal-sport angler fishery. Many lakes in this region are interconnected by streams or waterways that allow movement of walleyes among lakes. Because the movement of fish among lakes complicates the interpretation and use of PEs, we estimated postspawning movement rates of walleyes among interconnected lakes in four different lake chains (of two, two, four, and five lakes). Walleyes were captured and released on three occasions in each chain, with marks to indicate in which lake within the chain they were originally captured. We used Akaike's information criterion to select among four stratified capture-recapture models, with or without mortality and with constant or variable cap...

Background Standardized mortality ratios (SMRs) and other measures of relative risk by themselves may not suffice as descriptors of occupational hazards for many audiences including decision-makers and those at direct risk from hazardous work. To explore other approaches, we calculated excess years of potential life lost and excess lifetime risk for both lung diseases and fatal injuries in a cohort of uranium miners with historical records of exposure to radon gas. Methods We used relatively simple life table (SMR) methods and also analyzed lung cancer mortality with Poisson regression methods permitting control for smoking. Results Among uranium miners hired after 1950, whose all-cause SMR was 1.5, 28 percent would experience premature death from lung diseases or injury in a lifetime of uranium mining. On average, each miner lost 1.5 yr of potential life due to mining-related lung cancer, or almost 3 months of life for each year employed in uranium mining. As a consequence of all excess lung disease and injury risks combined, a year of mining was associated with 5.9 months loss of potential life. For each year actually working underground, miners lost more than 8 months of potential life. When controlled for smoking (and healthy worker effect) with Poisson regression, the estimates for radon-related lung cancer effects were slightly larger. Although chronic disease deaths dominated in excess years of life lost (due to radon, silica and possibly other exposures), more years were lost on average per individual injury death (38 yr), than per excess lung cancer (20 yr) or other lung disease death (18 yr). Fatal-injury dominated the potential years of life lost up to about age 40. Conclusions Years of life lost per years employed provides another, more intuitive summary of occupational mortality risk. Am. J. Ind. Med. 42:1–10, 2002. Published 2002 Wiley-Liss, Inc.

In 1990 the Wisconsin Department of Natural Resources implemented a 15-in (1 in = 2.56 cm) minimum length limit for walleyes Stizostedion vitreum on waters throughout the state, excluding some lakes where walleyes demonstrated slow growth or high mercury contamination. To determine if management goals for the regulation had been met, we examined the effects on lakes with self-sustaining walleye populations in the ceded territory of Wisconsin, specifically effects on population structure, exploitation, and angler catch and harvest. We compared creel survey data from up to 19 lakes sampled before and after the regulation had been implemented, including lakes affected by (N = 13) and exempted (N = 6) from the 15-in regulation. We also compared postregulation (1990–1998) creel and biological data from up to 76 lakes that were both affected and exempted. Effects of tribal harvest, which occurred on all of these 76 lakes but was not subject to the same length limit, were also examined using postregulat...

OBJECTIVE—To use various exposure-response models to estimate the risk of mortality from lung cancer due to occupational exposure to respirable crystalline silica dust. METHODS—Data from a cohort mortality study of 2342 white male California diatomaceous earth mining and processing workers exposed to crystalline silica dust (mainly cristobalite) were reanalyzed with Poisson regression and Cox's proportional hazards models. Internal and external adjustments were used to control for potential confounding from the effects of time since first observation, calendar time, age, and Hispanic ethnicity. Cubic smoothing spline models were used to assess the fit of the models. Exposures were lagged by 10 years. Evaluations of the fit of the models were performed by comparing their deviances. Lifetime risks of lung cancer were estimated up to age 85 with an actuarial approach that accounted for competing causes of death. RESULTS—Exposure to respirable crystalline silica dust was a significant predictor (p

Objectives The purpose of this study was to evaluate empirically the relevance of animal-bioassay-based models for predicting human risks from exposure to 1,3-butadiene (BD) using epidemiologic data. Methods Relative-risk results obtained with a regression model in a recent epidemiologic study were used to estimate leukemia risk for occupational and environmental exposures to BD and to compare these estimates with those previously derived from an analysis of animal bioassay data. Results The estimates of risk were found to be highly dependent on the model used when low levels of exposure were evaluated that are of environmental concern, but not at the levels of occupational concern. For example, at the level (1 part per million) of the recently revised standard of the Occupational Safety and Health Administration in the United States the estimates of lifetime excess risk ranged from 1 to 8 per 1000 workers. The range of the risk estimates derived from the epidemiologic models was remarkably similar to the range of risk estimates for occupational exposures (1 to 9 per thousand) previously developed by Dankovic et al in 1993 from an analysis of a mouse bioassay study for lymphocytic lymphoma. Conclusions Results for BD seem to provide another example of a high degree of concordance between the risk predictions from models of toxicologic and epidemiologic data, particularly at occupational levels of exposure.

Fatal injury surveillance data coupled with life expectancy data may be used to assess the impact of occupational fatal injuries on years of potential life lost (YPLL). We compare three definitions of YPLL and trends over time in YPLL. Two definitions determine YPLL as expected life lost to fixed life expectancies of 65 or 85 years. The third definition uses actuarial adjustments of life expectancy given survival to a given age stratified by gender and race. Fatalities from the National Traumatic Occupational Fatality (NTOF) database are used to illustrate the three definitions of YPLL. The three YPLL measures were similar in magnitude and direction of the trend in YPLL over 1980-1992. Proper interpretation of these trends can only be made in conjunction with other measures (e.g., rates). Almost all YPLL trends are declining, implying that over time fatal injuries are shifting to older workers. The exception is the increasing trend in YPLL for the retail trade industry, injury rates have also been increas...

OBJECTIVES: An updated version of a national surveillance system of traumatic occupational fatalities was used to explore adjusted and unadjusted trends in rates of fatal injury. METHODS: Data from the national traumatic occupational fatalities surveillance system were combined with data on employment from the United States Bureau of Labor Statistics. Poisson regression was then used to examine trends in rates of occupational fatality injuries while controlling for demographic and workplace characteristics. RESULTS: Adjusted annual changes in rates of fatal injuries ranged from a decline of 6.2% for workers in technical and administrative support occupations--for example, health, science, and engineering technicians, pilots, computer programmers--to an increase of 1.6% in machine operators, assemblers, and inspectors. For industries, annual changes ranged from a decline of 5.3% for workers in public administration--for example, justice, public order, and safety workers--to an increase of 2.6% for workers in the wholesale trade. By comparison, the annual decline over all industries and occupations was 3.1%. In many industries and occupations, an effect modification of annual trends by the age of the worker was also found with the oldest workers experiencing either no decline or a significant increase in rates of fatal injuries. CONCLUSIONS: This general pattern of decline, adjusted for the effects of demographic characteristics of the worker population, is encouraging; however, increases in rates of fatal injuries found in particular industries and occupations, suggest appropriate targets for increased injury prevention efforts.

Concern is raised by Dobie [J. Acoust. Soc. Am. 103, 2734 (1998)] regarding a recent analysis [, J. Acoust. Soc. Am. 101, 950–963 (1997)] of the NIOSH Occupational Noise and Hearing Survey data. Specifically, issues are raised concerning (1) definition of hearing handicap, (2) the use of frequency-specific articulation index (AI) weights applied to the binaural pure-tone average of 1, 2, 3, and 4 kHz, and (3) conclusions regarding significant excess risk based on this definition. We have reviewed the development of the definitions of hearing handicap and provide additional support for the use of a hearing handicap definition based on the binaural pure-tone average of 1, 2, 3, and 4 kHz and the weighting of specific frequencies. Furthermore, our definition of noise-induced hearing handicap is similar to one of several proposed by the International Standards Organization (Reference 1999Reference 1990) and the American National Standards Institute (Reference 3Reference 44Reference 1996). Additional analyses show that there is significant evidence of excess risk at daily exposure levels below 85 dB using any of the pure-tone average and/or weighting strategies we have examined. Hence we have provided additional support for our conclusions regarding exposure-response curves and we have reaffirmed that our methods are appropriate for the scope of our analysis.

Management of angler harvest of walleyes Stizostedion vitreum assumes that angling catch rates can be regulated by fish densities. Data on walleye densities in northern Wisconsin lakes obtained between 1990 and 1993 were used to develop a predictive model for walleye angling catch rates. Data collected in 1993–1994 were used to validate these models. Total numbers of walleye per acre were estimated from mark-recapture experiments conducted during April and May of each year. Creel surveys were conducted starting on the first Saturday in May and ending on 1 March of the following year for waters where population estimates were made. Linear regression indicated a high correlation between walleye densities and yearly walleye catch rates (r = 0.92, P < 0.05). Using the linear equation generated from this analysis, we predicted yearly walleye catch rates from walleye population estimates in 11 lakes for 1993–1994. All 11 angler catch rates were within the 95% prediction intervals. When data from 1993–1...

Two commonly used simulation models were combined to assess the effects of stocking and harvest regulations on the consumption dynamics of walleyes Stizostedion vitreum in Lake Mendota, Wisconsin. An age-structured population model was used to estimate the effects of five harvest scenarios on walleye population and fishery characteristics. Implementation of a 15-in minimum size limit resulted in increases in total yield (by weight), average weight of fish harvested, and walleye biomass remaining in the lake, Changes in walleye age structure resulting from various harvest scenarios were used as inputs to an energetics model to estimate how prey consumption by walleyes would vary under different harvest regulations. Simulations indicated that a stocking program that produced 8,000 yearling recruits annually would double walleye predation on planktivorous fish compared with predation estimated in 1987, when the study began. The modeling further indicated that a 15-in minimum size limit in conjunctio...

To estimate excess lifetime risk of (a) mortality from lung disease other than cancer (LDOC), and, (b) onset of radiographic silicosis, arising from occupational exposure to respirable crystalline silica dust.Data from a cohort of California diatomaceous earth mining and processing workers exposed to crystalline silica dust (mainly as cristobalite) were reanalyzed with Poisson regression methods with internal and external adjustments for potential confounding by calendar time, age, smoking, Hispanic ethnicity, and time since first observation. Model fit was evaluated by comparing deviances and fitting cubic spline models. Lifetime risks of death from LDOC and radiographic silicosis were estimated up to age 85 with an actuarial approach accounting for competing causes of death.For deaths due to LDOC, a linear relative rate model gave the best fit in Poisson regression analyses. At the mean cumulative exposure of LDOC cases to silica, after adjustment for smoking, the estimated rate ratio was 4.2 (p0.0001); at the maximum cumulative exposure of cases, the rate ratio was 18.4. The excess lifetime risk for white men exposed to respirable cristobalite dust for 45 years at the current permissible exposure limit (PEL; about 0.05 mg/m(3)) of the Occupational Safety and Health Administration was 54/1000 (95% confidence interval (95% CI) 17 to 150). For 70 incident cases of radiographic silicosis largely manifest before the end of employment, the best fit was also the linear relative rate model, predicting a rate ratio of 25.6 for silicosis at the mean cumulative exposure of the cases (p0.0001). The excess lifetime risk for silicosis at the current PEL was 75/1000.Current occupational health standards for crystalline silica permit risks of lung disease other than cancer far in excess of what is usually considered acceptable by the Occupational Safety and Health Administration (a lifetime risk of less than one in a thousand deaths).

Epidemiologic data is increasingly being used for dose-response analysis in risk assessment. The Environmental Protection Agency (EPA) and other U.S. agencies have expressed a preference for using epidemiologic data rather than toxicologic data when possible. However, there are a number of important sources of uncertainty in using epidemiologic data for this purpose that need to be clearly recognized and, when possible, quantified. This paper presents a critical review of the major sources of uncertainty in the use of epidemiologic data for cancer risk assessment. These may include: (1) study design issues such as potential confounding and other biases, inadequate sample size, and followup, (2) the choice of the data set, (3) specification of the dose-response model, (4) estimation of exposure and dose, and (5) unrecognized variability in susceptibility. Examples from risk assessments for cadmium, asbestos, and diesel exhaust are used to illustrate the potential magnitude of some of these sources of uncertainty. It is shown that the overall uncertainty from these various sources combined may often result in highly uncertain risk estimates from dose-response modeling of epidemiologic data. For this reason, we believe it is best to present a range of possible risk estimates, which, to the extent possible, reflects the variability and uncertainty inherent in the dose-response evaluation of epidemiologic data.

OBJECTIVES: To evaluate alternative models and estimate risk of mortality from lung cancer and asbestosis after occupational exposure to chrysotile asbestos. METHODS: Data were used from a recent update of a cohort mortality study of workers in a South Carolina textile factory. Alternative exposure-response models were evaluated with Poisson regression. A model designed to evaluate evidence of a threshold response was also fitted. Lifetime risks of lung cancer and asbestosis were estimated with an actuarial approach that accounts for competing causes of death. RESULTS: A highly significant exposure-response relation was found for both lung cancer and asbestosis. The exposure-response relation for lung cancer seemed to be linear on a multiplicative scale, which is consistent with previous analyses of lung cancer and exposure to asbestos. In contrast, the exposure-response relation for asbestosis seemed to be nonlinear on a multiplicative scale in this analysis. There was no significant evidence for a threshold in models of either the lung cancer or asbestosis. The excess lifetime risk for white men exposed for 45 years at the recently revised OSHA standard of 0.1 fibre/ml was predicted to be about 5/1000 for lung cancer, and 2/1000 for asbestosis. CONCLUSIONS: This study confirms the findings from previous investigations of a strong exposure-response relation between exposure to chrysotile asbestos and mortality from lung cancer, and asbestosis. The risk estimates for lung cancer derived from this analysis are higher than those derived from other populations exposed to chrysotile asbestos. Possible reasons for this discrepancy are discussed.

Not suprisingly, Lake Mendota’s fishes have been the subject of a multitude of studies since the days of Birge and Juday. However, these studies have focused almost entirely on yellow perch (Perca flavescens), white bass (Morone chrysops), and cisco (Coregonus artedii), probably because of their abundance or importance to the fishery. When this study began, relatively little was known about Lake Mendota’s piscivore community, including abundance, reproductive success, growth rates, diet, and distribution. Hence, we had some fundamental questions that needed to be addressed before we could predict the course of the biomanipulation experiment.

To the Editor: We thank Dr. Morfeld for his interest and appreciate the careful and detailed effort that he has undertaken in analyzing our recent study on work-related years of potential life lost [Park et al., 2003]. Dr. Morfeld is concerned that our approach, while "attractive in its simplicity," may suffer from several sources of bias. However, upon examination, his specific example appears to us to be inappropriate. A key element in Dr. Morfeld's argument for two of the sources of bias is a hypothetical population in which deaths resulting from an exposure are arbitrarily postulated to have been moved forward in time by 5 years. This stipulation was not derived from empirical evidence or a failure-time model, and ignores the reference population's survival characteristics as summarized in a relevant life-table.

Several hearing conservation programs (n=15) from a cross‐section of U.S. industries were examined to test whether there are greater rates of change in hearing levels in relation to increasing cumulative noise exposure during the period of audiometric follow‐up. The analysis also examined whether rates of hearing loss were lower among workers who wear hearing protection relative to workers who do not. These 15 audiometric databases had a total of 15 794 workers with 62 095 audiograms. Differences in a linear combination of 1–4 kHz biaural hearing levels of consecutive audiometric tests were examined using mixed effects models to account for correlated, repeated observations on individuals. These differences were modeled as a function of cumulative noise, gender, race, hearing protection use, age, learning effects, and baseline hearing level (measured after 14 h of quiet time). Analyses were conducted for the combined and individual databases. The analysis indicates there is significant heterogeneity among...