Shona Kelly

A comparison between the effort-reward imbalance and demand control models

BackgroundTo compare the predictive validity of the demand/control and reward/imbalance models, alone and in combination with each other, for self-reported health status and the self-reported presence of any chronic disease condition.MethodsSelf-reports for psychosocial work conditions were obtained in a sample of sawmill workers using the demand/control and effort/reward imbalance models. The relative predictive validity of task-level control was compared with effort/reward imbalance. As well, the predictive validity of a model developed by combining task-level control with effort/reward imbalance was determined. Logistic regression was utilized for all models.ResultsThe demand/control and effort/reward imbalance models independently predicted poor self-reported health status. The effort-reward imbalance model predicted the presence of a chronic disease while the demand/control model did not. A model combining effort-reward imbalance and task-level control was a better predictor of self-reported health status and any chronic condition than either model alone. Effort reward imbalance modeled with intrinsic effort had marginally better predictive validity than when modeled with extrinsic effort only.ConclusionsFuture work should explore the combined effects of these two models of psychosocial stress at work on health more thoroughly.

Effect of de-industrialisation on working conditions and self reported health in a sample of manufacturing workers

Study objective: To explore the impact of de-industrialisation over a 20 year period on working conditions and health among sawmill workers, in the province of British Columbia (BC), Canada. Design and Setting: This investigation is based on a sample of 3000 sawmill workers employed in 1979 (a year before the beginning de-industrialisation) and interviewed in 1998. The sample was obtained by random selection from an already gathered cohort of approximately 28 000 BC sawmill workers. Change in working conditions from 1979 to 1998 are described. Self reported health status, in 1998, was used as a dependent variable in logistic regression after controlling for confounders. Main results: Downsizing in BC sawmills eliminated 60% of workers between 1979 and 1998. Working conditions in 1998 were better for those who left the sawmill industry and obtained re-employment elsewhere. Workers who remained employed in restructuring sawmills were approximately 50% more likely to report poor health than those re-employed elsewhere. Conclusions: Working conditions and health status were better for workers who, under pressure of de-industrialisation, left the sawmill industry and obtained re-employment outside this sector.

Reliability of retrospective chlorophenol exposure estimates over five decades

For a cohort study of chlorophenate-exposed sawmill workers, historical exposures from the 1940s to the 1980s were estimated by teams of 9-20 employees (each interviewed individually). The mill histories were divided into eras when jobs and exposures were relatively stable. Raters with at least 5 years of work experience in an era were asked to estimate the frequency and duration of exposure for each job in the mill. Reliability measures for these estimates were calculated for each of the 39 mill and time period combinations, using the individual intraclass correlation coefficient (ICCind) to assess agreement between raters and the group intraclass correlation coefficient (ICCgroup) to assess the stability of the mean estimates of exposure. ICCind were low, with means that increased from 0.24 to 0.35 over the five decades. ICCgroup were considerably higher (means increasing from 0.78 to 0.88 over time), indicating that the number of raters used in this study was sufficient to produce stable average estimates of exposure throughout the study period. These data confirm the intuitive expectation that reliability of exposure estimates decreases when reconstruction of conditions in the distant past is required, and therefore that the random component of exposure misclassification is a greater threat to validity in these earlier time periods.

Background levels of PCBs in residents of British Columbia, Canada.

Regulations adopted in 1977 and 1980 by Environment Canada under the Environmental Contaminants Act prohibited the sale of new equipment containing polychlorinated biphenyls (PCBs), and restricted existing PCB uses to electrical equipment sufficiently enclosed to prevent a threat to either the environment or human health (Garrett 1985). In 1985, further regulations were promulgated to control the release of PCBs into the environment and to further restrict the sale of existing PCB equipment. At that time, the major users of PCBs in the western Canadian province of British Columbia (BC) were the electrical utilities (28%), the forest industry (43%, mainly in pulp and paper mills), and the mining industry (15%) (Rottluff et al 1990).

Dioxins and furans in residents of a forest industry region of Canada

Abstract Forestry has been the major industry in British Columbia for the last century. There has been concern that by-products of pulp and paper production and chlorophenol fungicides used in sawmills may present opportunities for residents to be environmentally or occupationally exposed to polychlorinated dibenzo-p-dioxins and dibenzofurans. To examine this possibility, dioxin and furan levels were measured in the adipose tissue of 41 British Columbians selected to match the age and sex distribution of the population and compared with levels in exposed and unexposed populations reported in the literature. Concentrations of dioxins and furans in the adipose tissue of the study subjects were in general very low, on the order of parts per trillion (pg/g lipid) for all furans and for dioxins with low levels of chlorination. Dioxin and furan levels in the British Columbia study group were similar to those of residents of other parts of Canada and to those of industrial populations not known to have direct exposure. Personal characteristics of the study subjects, including age, sex, weight, diet, area of residence, and occupation, were examined to determine whether these factors were related to dioxin and furan levels. Of these, only age showed a consistent effect; dioxin and most furan concentrations increased with age. Residence in a pulp mill town did not influence dioxin and furan concentrations. Additional investigations would be required to determine the effects of occupation and other locations of residence on dioxin concentrations in British Columbia residents.