Exposure assessment for a multicentric cohort study of cancer risk among European asphalt workers

There is a long-standing controversy about the health effects of fumes and vapors generated during paving and waterproofing with bitumen. Such emissions may be carcinogenic. To address this question, a historical multicentric cohort of asphalt workers was assembled by in eight countries. Assessment of historical exposures to known and suspected carcinogens (bitumen, organic vapour, coal tar, respirable silica, diesel exhaust, and asbestos) in the cohort became the main objective of this dissertation. First, published reports on exposures in the industry were reviewed. They provided some insight into the identity of factors that influence exposure to bitumen among road construction workers. However, the data available through published reports have limited value in assessing historical exposure levels in road construction industry. Next, a database of European asphalt individual workers' exposure measurements was created. The database allowed retrieval and consistent coding of 38 data sets, of which 34 have never been described in peer-reviewed scientific literature. It was used to create statistical models of bitumen fume, organic vapour and polycyclic aromatic hydrocarbons exposure intensity among paving workers, the most numerous bitumen-exposed group in the cohort. Individual exposure measurements from pavers (N=1581) were available from all countries enrolled in the study. Statistical models indicated that for paving workers, exposure intensity could be reconstructed quantitatively on the basis of time period and production characteristics. Alternative exposure assessment models were explored in a subset of data with more detailed contextual information in order to see whether they might have produced more optimal exposure grouping for epidemiological analyses. It was observed that on the basis of the available data and given constraints of retrospective cohort study design, we could not produce more uniform exposure groups by employing different exposure models. Internal validity of statistical models was assessed in a cross-validation procedure. External validity was evaluated using data not used to develop the original models. Validation of the models increased our confidence in their applicability to exposure assessment. Next, the statistical models were applied to the creation of an exposure matrix: the link between exposure estimates and actual working conditions in studies companies. Procedures were also developed for semi-quantitative estimation of exposure for (a) cohort members not employed in paving and (b) agents for which few or no exposure measurements were available. Production characteristics in the companies enrolled in the study were ascertained via a questionnaire. Our approach produced a data-driven exposure matrix that can be challenged in future studies and easily re-estimated. Performance of the exposure matrix was evaluated in analysis of the hypothesized relationship between bitumen fume exposure and lung cancer mortality. Constructing quantitative exposure indices appeared to have been justified because (a) the healthy worker effect confounded any associations between duration of exposure and lung cancer mortality and (b) we identified statistically significant associations between average bitumen fume exposure and lung cancer risk (after adjustment for coal tar co-exposure) that require further investigation. Many of the unresolved issues in the cohort analysis may be remedied in a nested case-control study

Assessing Cumulative Health Risks from Exposure to Environmental Mixtures—Three Fundamental Questions

Differential exposure to mixtures of environmental agents, including biological, chemical, physical, and psychosocial stressors, can contribute to increased vulnerability of human populations and ecologic systems. Cumulative risk assessment is a tool for organizing and analyzing information to evaluate the probability and seriousness of harmful effects caused by either simultaneous and/or sequential exposure to multiple environmental stressors. In this article we focus on elucidating key challenges that must be addressed to determine whether and to what degree differential exposure to environmental mixtures contributes to increased vulnerability of exposed populations. In particular, the emphasis is on examining three fundamental and interrelated questions that must be addressed as part of the process to assess cumulative risk: a) Which mixtures are most important from a public health perspective? and b) What is the nature (i.e., duration, frequency, timing) and magnitude (i.e., exposure concentration and dose) of relevant cumulative exposures for the population of interest? c) What is the mechanism (e.g., toxicokinetic or toxicodynamic) and consequence (e.g., additive, less than additive, more than additive) of the mixture’s interactive effects on exposed populations? The focus is primarily on human health effects from chemical mixtures, and the goal is to reinforce the need for improved assessment of cumulative exposure and better understanding of the biological mechanisms that determine toxicologic interactions among mixture constituents

Dynamic Critical Phenomena of Polymer Solutions

Recently, a systematic experiment measuring critical anomaly of viscosity of polymer solutions has been reported by H. Tanaka and his co-workers (Phys.Rev.E, 65, 021802, (2002)). According to their experiments, the dynamic critical exponent of viscosity y_c drastically decreases with increasing the molecular weight. In this article the kinetic coefficients renormalized by the non-linear hydrodynamic interaction are calculated by the mode coupling theory. We predict that the critical divergence of viscosity should be suppressed with increasing the molecular weight. The diffusion constant and the dynamic structure factor are also calculated. The present results explicitly show that the critical dynamics of polymer solutions should be affected by an extra spatio-temporal scale intrinsic to polymer solutions, and are consistent with the experiment of Tanaka, et al.Comment: 17 pages, 2 figures, to be published in J.Phys.Soc.Jp

Exposure of bakery and pastry apprentices to airborne flour dust using PM2.5 and PM10 personal samplers

<p>Abstract</p> <p>Background</p> <p>This study describes exposure levels of bakery and pastry apprentices to flour dust, a known risk factor of occupational asthma.</p> <p>Methods</p> <p>Questionnaires on work activity were completed by 286 students. Among them, 34 performed a series of two personal exposure measurements using a PM_2.5and PM₁₀personal sampler during a complete work shift, one during a cold ("winter") period, and the other during a hot ("summer") period.</p> <p>Results</p> <p>Bakery apprentices experience greater average PM_2.5and PM₁₀exposures than pastry apprentices (p < 0.006). Exposure values for both particulate fractions are greater in winter (average PM₁₀values among bakers = 1.10 mg.m^-3[standard deviation: 0.83]) than in summer (0.63 mg.m^-3[0.36]). While complying with current European occupational limit values, these exposures exceed the ACGIH recommendations set to prevent sensitization to flour dust (0.5 mg.m^-3). Over half the facilities had no ventilation system.</p> <p>Conclusion</p> <p>Young bakery apprentices incur substantial exposure to known airways allergens, a situation that might elicit early induction of airways inflammation.</p

Moving from contractor to owner operator: Impact on safety culture; a case study

Purpose – The purpose of this paper is to investigate whether a change in staffing contractual arrangements, specific training in hazard identification, mentoring of supervisors and the introduction of a robust safety system could improve an organisation\u27s safety culture. How safety conditions change under contracted out labour compared to direct labour and the influence that contracting out has on organisational safety culture is explored. Design/methodology/approach – The study used a case study methodology to detail how the change occurred over a six month period in 2011. As part of the analysis a model of the change process and push-pull factors is offered. Findings – As a result of the change, all areas saw some improvement. Work-related injury statistics dropped significantly, supervisors were clear of their roles, actively monitoring their crews to ensure they worked in a safer manner than before, and staff were actively addressing work-place hazards. With the safety system in place the organisation should be deemed compliant and diligent by the state auditing authorities. This study has also shown that using contractor workers together with in-house workers that are managed under different safety regimes is problematic. The problems don’t occur due to the contractor\u27s safety systems being less robust than the parent company\u27s or that contract workers are themselves less safe; it is the added complexity of managing multiple safety regimes and the lack of trust of the robustness of each system that create conflict. Research limitations/implications – The paper reports on the change process of one mining organisation in Western Australia as a case study from a managerial sample and is thereby limited. Practical implications – This study demonstrates the difficulties in changing safety culture in an underground mining organisation. The paper argues the need for specialised training in identifying hazards by the staff, the mentoring of supervisory staff and the adoption of a robust safety system to support improved safety culture. Originality/value – There is little research conducted in the resources sector researching changes in human resource supply and OHS management, in particular moving from contracted labour to hiring in-house. This case provides an insight into how a change in staffing hiring arrangements, together with specific safety initiatives, has a positive impact on safety performance