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Cohort studies
Published in Antony Stewart, Basic Statistics and Epidemiology, 2018
Retrospective cohort studies are also possible, and are common in occupational epidemiology and disease outbreak investigations. These, in effect, are prospective cohort studies in reverse, as depicted in Figure 29.2. Start points, exposure groups and end points are all treated in the same way – the real difference is that retrospective cohort studies look back in time, rather than forward.
Limitations of epidemiologic exposure studies on the health effects of asbestos
Published in Dorsett D. Smith, The Health Effects of Asbestos, 2015
Occupational epidemiology is the scientific study of the effects of workplace exposure on the frequency and distribution of various diseases or injuries in a given population. Basically, an epidemiologist studies the occurrence, or incidence or number of new cases over the sum of time individuals in the population were at risk for having that event, such as lung cancer in a population of workers such as asbestos textile workers, and then compares the rate of disease such as lung cancer to the rate of lung cancer in the general population or another more typical reference population. The term incidence is defined as the fraction of a study population initially free of disease that develops a condition such as lung cancer over a period of time, commonly expressed as events/person/years. Prevalence is the epidemiological term used to describe the proportion of people possessing a clinical condition at a single point of time.
Occupational Cancer
Published in Peter G. Shields, Cancer Risk Assessment, 2005
Robert J. McCunney, Lee Okurowski
Occupational epidemiology studies assess exposure-disease associations in human populations under actual conditions. The long latency periods, however, between initial exposure and the onset of cancers, render the timely epidemiologic evaluation of potential carcinogens in the workplace pressingly difficult (19). Moreover, epidemiological studies tend to be inefficient in detecting low-level cancer risks since relatively large sample sizes are needed to uncover true increases of disease. In vivo and in vitro studies can be valuable supplements to epidemiology in assessing occupational cancer risk. These studies, extensively used over the past 30 years, have also yielded advances in understanding mechanisms of cancer (4).
Evaluation of asbestos exposure resulting from simulated application of spiked talcum powders
Published in Inhalation Toxicology, 2022
Eric W. Miller, Benjamin Roberts, Kara Keeton, Andrew Monnot, Taylor Tarpey, Nicole Zoghby, Alan Segrave, Jennifer S. Pierce
Cumulative tremolite asbestos exposure estimates were calculated assuming that: (1) an individual applied cosmetic talc products containing 0.1% asbestiform tremolite over a period (ED) of 1, 20, 45 and 70 years; (2) the exposure frequency (EF; applications per day) is consistent with the 50th and 90th percentile daily frequencies reported by EPA for ‘baby powder – adult use’ (0.13–0.22 and 0.57–1.00 applications per day), ‘powders’ (0.18–0.39 and 1.00 applications per day), and ‘face powders’ (0.33–0.67 and 1.00–1.29 applications per day) (EPA 2011); and (3) an exposure time (ET) of 0.5 h per application. The mean and maximum measured 30-min PCME measurements (C; f/cc) from this study were used for the 50th and 90th percentile cumulative exposure estimates, respectively. The standardization over a work year permits comparisons to cumulative occupational exposures, occupational epidemiology studies, and occupational standards. The standardization over an environmental year allows for comparisons to asbestos exposures from ambient air.
Hexavalent chromium and stomach cancer: a systematic review and meta-analysis
Published in Critical Reviews in Toxicology, 2019
Mina Suh, Daniele Wikoff, Loren Lipworth, Michael Goodman, Seneca Fitch, Liz Mittal, Caroline Ring, Deborah Proctor
In addition to evidence from occupational epidemiology studies, data from animal toxicology studies contribute insight into the overall assessment of hazard and risk. Typical of animal toxicology studies, the administered doses of Cr(VI) in these studies far exceed potential human exposures. Nonetheless, animal studies offer an evidence stream traditionally used for both hazard identification and risk assessment. For the purpose of this review, important characteristics of animal data include low risk of bias in exposure characterization, because exposure occurred by oral administration with relatively precise measures of individual dose, as compared to the human data. The animal study data also include conflicting and somewhat controversial findings because tumors of the stomach have only been reported in the forestomach of mice, a structure of the stomach that humans lack.
Job titles classified into socioeconomic and occupational groups identify subjects with increased risk for respiratory symptoms independent of occupational exposure to vapour, gas, dust, or fumes
Published in European Clinical Respiratory Journal, 2018
Christian Schyllert, Martin Andersson, Linnea Hedman, Magnus Ekström, Helena Backman, Anne Lindberg, Eva Rönmark
In occupational epidemiology, the healthy worker effect must be considered [32–34]. When the analyses of socioeconomic and occupational groups were stratified for number of years in main occupation, the associations were in general statistically significant for those who had worked 21–30 years, but not for those who had worked more than 30 years. This could be a healthy worker effect; the workers that stay the longest are respiratory healthier, not displaying symptoms. Furthermore, some of those who reported the highest number of working years might have retired when the data collection was conducted, and their respiratory symptoms, if any, may have since remitted. Due to the cross-sectional design of the study, and the fact that we lack data on occupation before onset of respiratory symptoms, we cannot draw any conclusions on causality. Nevertheless, we found similar results when subjects with onset of asthma before the age of 18 were excluded. In the current study, we have used ‘longest held job’ which can create bias as exposure to specific agents in certain occupations can cause symptoms after a shorter period of time, and we do not have data on job changes. However, our results indicate that symptoms such as cough may develop after a shorter period of exposure while a longer period of exposure is needed for symptoms such as wheeze. Further, we have in a previous study found indications that different types of exposure associate with different types of respiratory symptoms [35].