Statistical issues in assessing human population exposures (original) (raw)
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Statistical Methods to Estimate Human Exposure to Environmental Pollutants
2005
Using statistical methods to assess human exposure to environmental pollutants is a relatively new concept in environmental sciences. This paper contains discussion of (1) the importance of exposure studies to EP A's environment research and regulatory efforts; (2) new approaches to measuring total human exposure; (3) several recent human exposure field studies, looking at the specific contributions of survey research techniques to these studies: and (4) implications of the findings of total human exposure studies.
Statistical Modeling to Determine Sources of Variability in Exposures to Welding Fumes
Annals of Occupational Hygiene, 2011
Background/Aims: Exposures to total particulate matter (TP) and manganese (Mn) received by workers during welding and allied hot processes were analyzed to assess the sources and magnitudes of variability. Methods: Compilation of data from several countries identified 2065 TP and 697 Mn measurements for analysis. Linear mixed models were used to determine fixed effects due to different countries, industries and trades, process characteristics, and the sampling regimen, and to estimate components of variance within workers (both intraday and interday), between workers (within worksites), and across worksites. Results: The fixed effects explained 55 and 49% of variation in TP and Mn exposures, respectively. The country, industry/trade, type of ventilation, and type of work/welding process were the major factors affecting exposures to both agents. Measurements in the USA were generally higher than those in other countries. Exposure to TP was 67% higher in enclosed spaces and 43% lower with local exhaust ventilation (LEV), was higher among boilermakers and was higher when either a mild-steel base metal or a flux cored consumable was used. Exposure to Mn was 750% higher in enclosed spaces and 67% lower when LEV was present. Air concentrations of Mn were significantly affected by the welding consumables but not by the base metal. Resistance welding produced significantly lower TP and Mn exposures compared to other welding processes. Interestingly, exposures to TP had not changed over the 40 years of observation, while those of Mn showed (non-significant) reductions of 3.6% year 21. After controlling for fixed effects, variance components between worksites and between-individual workers within a worksite were reduced by 89 and 57% for TP and 75 and 63% for Mn, respectively. The within-worker variation (sum of intraday and interday variance components) of Mn exposure was three times higher than that of TP exposure. The estimated probabilities of exceeding occupational exposure limits were very high (generally much >10%) for both agents. Conclusions: Welding exposures to TP and Mn vary considerably across the world and across occupational groups. Exposures to both contaminants have been and continue to be unacceptably high in most sectors of industry. Because exposures to the two agents have different sources and characteristics, separate control strategies should be considered to reduce welders' exposures to TP and Mn.
Agreement between qualitative exposure estimates and quantitative exposure measurements
American Journal of Industrial Medicine, 1987
A method for qualitative estimation of the exposure at task level was used and validated with actual measurements in five small factories. The results showed that occupational hygienists were in general the most successful estimators. Plant supervisors and workers handled the estimation method less successfully because of more misclassification of the tasks.
International Journal of Environmental Research and Public Health
On 20 October 2020, the Working Group “Exposure Models” of the Europe Regional Chapter of the International Society of Exposure Science (ISES Europe) organised an online workshop to discuss the theoretical background of models for the assessment of occupational exposure to chemicals. In this report, participants of the workshop with an active role before and during the workshop summarise the most relevant discussion points and conclusions of this well-attended workshop. ISES Europe has identified exposure modelling as one priority area for the strategic development of exposure science in Europe in the coming years. This specific workshop aimed to discuss the main challenges in developing, validating, and using occupational-exposure models for regulatory purposes. The theoretical background, application domain, and limitations of different modelling approaches were presented and discussed, focusing on empirical “modifying-factor” or “mass-balance-based” approaches. During the discuss...
Estimating Benchmark Concentrations and Other Noncancer Endpoints in Epidemiology Studies
Risk Analysis, 1997
Methods for evaluating the hazards associated with noncancer responses with epidemiologic data are considered. The methods for noncancer risk assessment have largely been developed for experimental data, and are not always suitable for the more complex structure of epidemiologic data. In epidemiology, the measurement of the response and the exposure is often either continuous or dichotomous. For a continuous noncancer response modeled with multiple regression, a variety of endpoints may be examined: (1) the concentration associated with absolute or relative decrements in response; (2) a threshold concentration associated with no change in response; and (3) the concentration associated with a particular added risk of impairment. For a dichotomous noncancer response modeled with logistic regression, concentrations associated with specified added/extra risk or with a threshold responses may be estimated. No-observed-effect concentrations may also be estimated for categorizations of exposures for both continuous and dichotomous responses but these may depend on the arbitrary categories chosen. Respiratory function in miners exposed to coal dust is used to illustrate these methods.
Attenuation of exposure-response curves in occupational cohort studies at high exposure levels
Scandinavian Journal of Work, Environment & Health, 2003
Numerous occupational cohort mortality studies have observed exposure-response curves to have an increasing slope at low exposure levels that attenuates or even turns negative at high exposure levels. Examples discussed in this paper include dioxin, silica, 1,3-butadiene, cadmium, beryllium, radon daughters, diesel fumes, nickel, arsenic, and hexavalent chromium. Possible explanations for this phenomenon include (i) bias introduced by the healthy worker survivor effect, (ii) a depletion of the number of susceptible people in the population at high exposure levels, (iii) a natural limit on the relative risk for diseases with a high background rate, (iv) mismeasurement or misclassification of exposures, (v) the influence of other risk factors that vary by the level of the main exposure, and (vi) the saturation of key enzyme systems or other processes involved in the development of disease.
From Expert-based to Quantitative Retrospective Exposure Assessment at a Soderberg Aluminum Smelter
Annals of Occupational Hygiene, 2006
Objectives: Expert judgement of exposure levels is often only poorly or moderately correlated with directly measured levels. For a follow-up of a historical cohort study at a Söderberg aluminum smelter we updated an expert-based semiquantitative job exposure matrix of coal tar pitch volatiles (CTPV) to quantitative estimates of CTPV and benzo(a)pyrene (BaP).
Occupational exposure models: a systematic translation into each other
2014
How to find us: Generic exposure tools are currently widely used for chemical safety assessments under REACH. Several 1st tier exposure models such as ECETOC TRA, MEASE, EMKG-EXPO-TOOL, STOFFEN-MANAGER and RISKOFDERM are recommended by the European Chemicals Agency (ECHA) for estimating occupational exposure; however, none of these models have been extensively validated during their development. The German Federal Institute for Occupational Safety and Health, (BAuA) has therefore initiated and sponsored a comprehensive Evaluation of the Tier 1 Exposure Assessment Models (ETEAM). Carried out by the Institute of Occupational Medicine (IOM Edinburgh) and the Fraunhofer Institute for Toxicology (ITEM Hannover) the ETEAM project was intended to compare and contrast the different REACH Tier 1 exposure assessment models in terms of their validity, scope of application, functionality and user-friendliness. 14:10 Session I: Scientific background and user-friendliness of the models Chair Dr. Rüdiger Pipke, BAuA Dortmund Conceptual Evaluation, Discussion Dr. Katrin Schröder, Fraunhofer ITEM Operational analysis User-friendliness, Discussion Judith Lamb, IOM 15:10 coffee break and poster viewing 15:40 Between user reliability, Discussion Dr. Karen Galea, IOM Uncertainty analysis, Discussion Dr. Susanne Hesse, Fraunhofer ITEM 16:40 Session II: Comparison of model estimates with measured data Chair IFA, Dr. Dorothea Koppisch Characterisation of data basis, Discussion Judith Lamb, IOM Methodology of evaluation/statistical analysis, Discussion Dr. Martie van Tongeren, IOM 18:30 Evening program (Dortmunder U) wednesday, march 26 th 2014 * 9:00 Session III: Results and recommendations Chair Prof. Dr. John Cherrie, IOM Results of external validation exercise, Discussion Judith Lamb, IOM Implications from the results and practical recommendations for model users and developers, Discussion Dr. Martie van Tongeren, IOM 10:40 coffee break and poster viewing 11:10 Closing session Chair Andreas Ahrens, ECHA Current activities on model development and validation Prof. Dr. John Cherrie, IOM Panel discussion including model owners: Challenges and actions (the way forward) for tier 1 exposure assessment Representatives of ECETOC, EBRC, BAuA, Stoffenmanager Consortium, IOM/Fraunhofer ITEM
SYN-JEM: A Quantitative Job-Exposure Matrix for Five Lung Carcinogens
The Annals of occupational hygiene, 2016
The use of measurement data in occupational exposure assessment allows more quantitative analyses of possible exposure-response relations. We describe a quantitative exposure assessment approach for five lung carcinogens (i.e. asbestos, chromium-VI, nickel, polycyclic aromatic hydrocarbons (by its proxy benzo(a)pyrene (BaP)) and respirable crystalline silica). A quantitative job-exposure matrix (JEM) was developed based on statistical modeling of large quantities of personal measurements. Empirical linear models were developed using personal occupational exposure measurements (n = 102306) from Europe and Canada, as well as auxiliary information like job (industry), year of sampling, region, an a priori exposure rating of each job (none, low, and high exposed), sampling and analytical methods, and sampling duration. The model outcomes were used to create a JEM with a quantitative estimate of the level of exposure by job, year, and region. Decreasing time trends were observed for all ...