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P A Demers

Publications and source records attributed to P A Demers.

At least 19 recordsLinked to original sources
PubMed2003

Validation of a semi-quantitative job exposure matrix at a Söderberg aluminum smelter.

OBJECTIVES: We tested the validity of a job exposure matrix (JEM) for coal tar pitch volatiles (CTPV) at a Söderberg aluminum smelter. The JEM had been developed by a committee of company hygienists and union representatives for an earlier study of cancer incidence and mortality. Our aim was to test the validity and reliability of the expert-based assignments. METHODS: Personal CTPV exposure measurements (n = 1879) overlapped 11 yr of the JEM. The arithmetic mean was calculated for 35 job/time period combinations (35% of the exposed work history), categorized using the original exposure intervals, and compared with the expert-based assignments. RESULTS: The expert-based and the measurement-based exposure assignments were only moderately correlated (Spearman's rho = 0.42; weighted kappa = 0.39, CI 0.10-0.69). Only 40% of the expert-based medium category assignments were correctly assigned, with better agreement in the low (84%) and high (100%) categories. Pot operation jobs exhibited better agreement (rho = 0.60) than the maintenance and pot shell repair jobs (rho = 0.25). The mid-point value of the medium category was overestimated by 0.3 mg/m(3). CONCLUSIONS: The expert-based exposure assignments may be improved by better characterizing the transitions between exposure categories, by accounting for exposure differences between pot lines and by re-examining the category mid-point values used in calculating the cumulative exposure. Lack of historical exposure measurements often requires reliance on expert knowledge to assess exposure levels. Validating the experts' estimates against available exposure measurements may help to identify weaknesses in the exposure assessment where improvements may be possible, as was shown here.

Air Pollutants, Occupational↗
PubMed2002

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.

Adult↗
PubMed2001

Measuring psychosocial job strain with the job content questionnaire using experienced job evaluators.

BACKGROUND: A union/management system of job evaluation has been in place in the British Columbia (BC) sawmill industry since the late 1960s. This system uses an instrument, very similar to the job content questionnaire (JCQ) to evaluate psychosocial work conditions for sawmill jobs. METHODS: Four experienced evaluators, one from the union and three from industry, independently estimated psychosocial work conditions for 54 current job titles in a "typical" coastal sawmill using a shortened, 18-question version of the JCQ questionnaire. RESULTS: Inter-rater reliability was acceptable for control but not for co-worker social support, physical demand, or psychological demand. Reliability was least for psychological demand. CONCLUSIONS: Experienced job evaluators in the sawmill industry were able to reliably estimate only the control dimension of the JCQ. The observed lowest reliability for psychological job demand may be due to the imprecise construct definition in the domain of the JCQ instrument.

Evaluation Studies as Topic↗
PubMed2001

Comparison of expert-rater methods for assessing psychosocial job strain.

OBJECTIVES: This study tested the reliability and validity of industry- and mill-level expert methods for measuring psychosocial work conditions in British Columbia sawmills using the demand-control model. METHODS: In the industry-level method 4 sawmill job evaluators estimated psychosocial work conditions at a generic sawmill. In the mill-level method panels of experienced sawmill workers estimated psychosocial work conditions at 3 sawmills. Scores for psychosocial work conditions were developed using both expert methods and applied to job titles in a sawmill worker database containing self-reported health status and heart disease. The interrater reliability and the concurrent and predictive validity of the expert rater methods were assessed. RESULTS: The interrater reliability and concurrent reliability were higher for the mill-level method than for the industry-level method. For all the psychosocial variables the reliability for the mill-level method was greater than 0.90. The predictive validity results were inconclusive. CONCLUSIONS: The greater reliability and concurrent validity of the mill-level method indicates that panels of experienced workers should be considered as potential experts in future studies measuring psychosocial work conditions.

Adult↗
PubMed2000

Laryngeal and hypopharyngeal cancers and occupational exposure to formaldehyde and various dusts: a case-control study in France.

OBJECTIVES: A case-control study was conducted in France to assess possible associations between occupational exposures and squamous cell carcinomas of the larynx and hypopharynx. METHODS: The study was restricted to men, and included 201 hypopharyngeal cancers, 296 laryngeal cancers, and 296 controls (patients with other tumour sites). Detailed information on smoking, alcohol consumption, and lifetime occupational history was collected. Occupational exposure to seven substances (formaldehyde, leather dust, wood dust, flour dust, coal dust, silica dust, and textile dust) was assessed with a job exposure matrix. Exposure variables used in the analysis were probability, duration, and cumulative level of exposure. Odds ratios (ORs) with their 95% confidence intervals (95% CIs) were estimated by unconditional logistic regression, and were adjusted for major confounding factors (age, smoking, alcohol, and when relevant other occupational exposures). RESULTS: Hypopharyngeal cancer was found to be associated with exposure to coal dust (OR 2.31, 95% CI 1.21 to 4.40), with a significant rise in risk with probability (p<0.005 for trend) and level (p<0.007 for trend) of exposure. Exposure to coal dust was also associated with an increased risk of laryngeal cancer (OR 1.67, 95% CI 0.92 to 3.02), but no dose-response pattern was found. A significant relation, limited to hypopharyngeal cancer, was found with the probability of exposure to formaldehyde (p<0.005 for trend), with a fourfold risk for the highest category (OR 3.78, 95% CI 1.50 to 9.49). When subjects exposed to formaldehyde with a low probability were excluded, the risk also increased with duration (p<0.04) and cumulative level of exposure (p<0.14). No significant association was found for any other substance. CONCLUSION: These results indicate that exposure to formaldehyde and coal dust may increase the risk of hypopharyngeal cancer.

Aged↗
PubMed2000

Childhood cancer in the offspring of male sawmill workers occupationally exposed to chlorophenate fungicides.

The objective of this study was to determine whether paternal occupational exposure to chlorophenol fungicides and their dioxin contaminants is associated with childhood cancer in the offspring of sawmill workers. We used data from 23,829 British Columbian sawmill workers employed for at least 1 continuous year between 1950 and 1985 in 11 sawmills that used chlorophenates. Probabilistic linkage of the sawmill worker cohort to the provincial marriage and birth files produced an offspring cohort of 19,674 children born at least 1 year after the initiation of employment in the period 1952-1988. We then linked the offspring cohort to the British Columbia Cancer Registry. We included all malignancies in cases younger than 20 years of age that appeared on the cancer registry between 1969 and 1993. We calculated standardized incidence ratios (SIRs) using the British Columbia population as a reference. A nested case-control analysis assessed the effects of paternal cumulative exposure and windows of exposure on the risk of developing cancer in the offspring. We identified 40 cases of cancer during 259,919 person-years of follow-up. The all-cancer SIR was 1.0 [95% confidence interval (CI), 0.7-1.4]; the SIR for leukemia was 1.0 (CI, 0.5-1.8); and the SIR for brain cancer was 1.3 (CI, 0.6-2.5). The nested case-control analysis showed slightly increased risks in the highest categories of chlorophenol exposure, although none was statistically significant. Our analyses provide little evidence to support a relationship between the risk of childhood cancer and paternal occupational exposure to chlorophenate fungicides in British Columbian sawmills.

Adolescent↗
PubMed1999

Sinonasal cancer, occupation, and tobacco smoking in European women and men.

BACKGROUND: In this analysis of European case-control studies on sinonasal cancer, we examined the risk for occupation and smoking, by gender and histological type. METHODS: The pooled data included 104 female and 451 male cases, and 241 female and 1,464 male controls. Lifetime smoking and occupational history were recoded following uniform criteria, and job-exposure matrices were applied for wood and leather dust. RESULTS: Wood dust exposure was associated with an excess risk in men (OR = 2.36, 95% CI 1.75-3.2) but not in women (OR = 1.17, 95% CI 0.31-4.47). Exposure to leather dust was associated with an excess risk in both genders. Both wood and leather dust were associated with adenocarcinomas rather than squamous cell carcinomas. Excess risks for smoking were higher for squamous cell carcinomas and higher in men than in women. CONCLUSIONS: In these European populations, occupation was associated with about 11% of all sinonasal cancers in women and 39% in men. This difference can, in part, be attributed to variation in exposure patterns between genders.

Adenocarcinoma↗
PubMed1999

Crystalline silica exposure, radiological silicosis, and lung cancer mortality in diatomaceous earth industry workers.

BACKGROUND: The role of silicosis as either a necessary or incidental condition in silica associated lung cancer remains unresolved. To address this issue a cohort analysis of dose-response relations for crystalline silica and lung cancer mortality was conducted among diatomaceous earth workers classified according to the presence or absence of radiological silicosis. METHODS: Radiological silicosis was determined by median 1980 International Labour Organisation system readings of a panel of three "B" readers for 1809 of 2342 white male workers in a diatomaceous earth facility in California. Standardised mortality ratios (SMR) for lung cancer, based on United States rates for 1942-94, were calculated separately for workers with and without radiological silicosis according to cumulative exposures to respirable crystalline silica (milligrams per cubic meter x years; mg/m3-years) lagged 15 years. RESULTS: Eighty one cases of silicosis were identified, including 77 with small opacities of > or = 1/0 and four with large opacities. A slightly larger excess of lung cancer was found among the subjects with silicosis (SMR 1.57, 95% confidence interval (CI) 0.43 to 4.03) than in workers without silicosis (SMR 1.19, 95% CI 0.87 to 1.57). An association between silica exposure and lung cancer risk was detected among those without silicosis; a statistically significant (p = 0.02) increasing trend of lung cancer risk was seen with cumulative exposure, with SMR reaching 2.40 (95% CI 1.24 to 4.20) at the highest exposure level (> or = 5.0 mg/m3-years). A similar statistically significant (p = 0.02) dose-response gradient was observed among non-silicotic subjects when follow up was truncated at 15 years after the final negative radiograph (SMR 2.96, 95% CI 1.19 to 6.08 at > or = 5.0 mg/m3-years), indicating that the association among non-silicotic subjects was unlikely to be accounted for by undetected radiological silicosis. CONCLUSIONS: The dose-response relation observed between cumulative exposure to respirable crystalline silica and lung cancer mortality among workers without radiological silicosis suggests that silicosis is not a necessary co-condition for silica related lung carcinogenesis. However, the relatively small number of silicosis cases in the cohort and the absence of radiographic data after employment limit interpretations.

Adult↗
PubMed1999

Determinants of exposure to inhalable particulate, wood dust, resin acids, and monoterpenes in a lumber mill environment.

In a lumber mill in the northern inland region of British Columbia, Canada, we measured inhalable particulate, resin acid, and monoterpene exposures, and estimated wood dust exposures. Potential determinants of exposure were documented concurrently, including weather conditions, tree species, wood conditions, jobs, tasks, equipment used, and certain control measures. Over 220 personal samples were taken for each contaminant. Geometric mean concentrations were 0.98 mg/m3 for inhalable particulate, 0.49 mg/m3 for estimated wood dust, 8.04 micrograms/m3 for total resin acids, and 1.11 mg/m3 for total monoterpenes. Multiple regression models for all contaminants indicated that spruce and pine produced higher exposures than alpine fir or mixed tree species, cleaning up sawdust increased exposures, and personnel enclosure was an effective means of reducing exposures. Sawing wood in the primary breakdown areas of the mill was the main contributor to monoterpene exposures, so exposures were highest for the barker operator, the head rig operator, the canter operator, the board edgers, and a roving utility worker in the sawmill, and lowest in the planer mills (after kiln drying of the lumber) and yard. Cleaning up sawdust, planing kiln-dried lumber, and driving mobile equipment in the yard substantially increased exposures to both inhalable particulate and estimated wood dust. Jobs at the front end of the sawmill where primary breakdown of the logs takes place had lower exposures. Resin acid exposures followed a similar pattern, except that yard driving jobs did not increase exposures.

Air Pollutants, Occupational↗
PubMed1999

A field comparison of inhalable and thoracic size selective sampling techniques.

We measured inhalable, thoracic, and so-called "total" wood dust exposure in British Columbia lumber mill workers. Particle-size selective sampling was conducted using the GSP and Seven hole inhalable samplers, the PEM thoracic sampler and the 37-mm closed-face cassette "total" sampler. All measurements were full-shift personal samples, obtained from randomly selected workers. We obtained intersampler comparison data for the following pairs of instruments: GSP and 37-mm sampler; GSP and seven-hole sampler (SHS); and PEM and 37-mm sampler. The intersampler measurement ratios were estimated as: GSP/37-mm sampler = 4.2; GSP/SHS = 1.7; and PEM/37-mm sampler = 1.6. The GSP/37-mm sampler ratio is consistent with previously reported findings, while PEM/37-mm sampler and GSP/SHS ratios were both larger than expected. We found that in all comparisons, the measurement ratio had significant variability that was greatest at low ambient dust concentrations. Although it was not possible to attribute the source of the variability to specific sampler types, we concluded that the GSP sampler might be susceptible to "projectile" particles not normally aspirated, and may be vulnerable to direct aspiration of dust from accidentally contacted surfaces. The PEM was designed for environmental monitoring, and it is possible that it is unsuited to the higher particulate concentrations found in some occupational settings. Disparities among inhalable sampling techniques such as that between GSP and SHS should be investigated further in light of the proposed adoption of the inhalable method as an industrial standard.

Air Pollutants, Occupational↗
PubMed1998

Cancer mortality and wood dust exposure among participants in the American Cancer Society Cancer Prevention Study-II (CPS-II).

In 1994, the International Agency for Research on Cancer (IARC) classified wood duct as a human carcinogen, based on very strong evidence of a carcinogenic risk of sino-nasal cancer. Excesses of other cancers, including lung and stomach, have been reported among persons employed in wood industries or occupationally exposed to wood dust, but not as consistently. We investigated such possible associations using the mortality experience of 362,823 men enrolled in the American Cancer Society's Cancer Prevention Study-II in 1982 and followed up for 6 years. Within this group, 45,399 men (12.5%) reported either employment in a wood-related occupation or exposure to wood dust or both. Among woodworkers, a small but significant excess risk was found for all cases of death (RR 1.17 (95% CI 1.11-1.24)) and for total malignancies (RR 1.17 (1.05-1.30)). Among men who reported exposure to wood dust, there was an elevated risk of total mortality (Rr 1.07 (1.03-1.11)), total malignancies (RR 1.08 (1.01-1.15)), and lung cancer (RR 1.17 (1.04-1.31)). Among woodworkers, a significant trend (P = 0.02) of increasing risk of lung cancer with increasing duration of exposure was observed. An unexpected, significantly increased mortality from prostate cancer was observed in both wood-employed and wood-exposed, and a twofold increased risk of fatal brain cancer was seen among the former. Lung cancer mortality was especially high among woodworkers who also reported exposure to asbestos or formaldehyde, and it appears that exposure to these known carcinogens may partly explain the observed increased risks. Excess sino-nasal cancer was not observed, but the number of cases was small.

Cause of Death↗
PubMed1998

Nonmalignant respiratory disease mortality among woodworkers participating in the American Cancer Society Cancer Prevention Study-II (CPS-II).

Nonmalignant respiratory disease (NMRD) mortality was examined among woodworkers participating in the American Cancer Society's CPS-II cohort study. During the 6-year prospective follow-up there were 97 NMRD death's among 11,541 men reporting employment in wood-related occupations and 1,338 NMRD deaths among 317,424 men reporting no exposure to wood dust or wood-related jobs. Relative risks, adjusted for age and smoking, were calculated using Poisson regression. A small excess of NMRD was observed among woodworkers. However, the relative risk was higher among woodworkers who did not report exposure to wood dust (RR = 1.52, 95% CI = 1.18-1.97) than those who did (RR = 1.27, 95% CI = 0.91-1.77), and no clear trend with duration of exposure was observed. An excess of NMRD was observed among woodworkers reporting exposure to asbestos (RR = 1.59, 95% CI = 0.85-2.96), as well as the small number of woodworkers reporting exposure to formaldehyde (RR = 1.95, 95% CI = 0.63-6.06), but men not reporting exposure to these substances also had an excess risk. Although limited by a short follow-up period and crude indicators of exposure, the strengths of this analysis were the ability to compare woodworkers to a similar, healthy population and to adjust for the effects of smoking. Cohort studies with better exposure information are needed to examine the role of occupational exposures among woodworkers in the etiology of respiratory disease.

Cohort Studies↗
PubMed1998

Radiographic evidence of silicosis risk in the diatomaceous earth industry.

There is limited and conflicting evidence regarding the exposure-response relationship between exposure to crystalline silica and silicosis; the level of risk to current workers remains uncertain. We conducted an epidemiologic investigation of 1,809 workers in the diatomaceous earth industry, where exposures to crystalline silica are primarily to the cristobalite form. On the basis of the median of three independent readings, 81 (4.5%) workers were judged to have opacities on chest radiographs (small opacities, profusion >= 1/0, and/or large opacities). Age-adjusted relative risk of opacities increased significantly with cumulative exposure to crystalline silica. The concentration of respirable crystalline silica to which workers were exposed (highly correlated with period of hire) was an important determinant of risk after accounting for cumulative exposure. For workers with an average exposure to crystalline silica of <= 0.50 mg/m3 (or hired >= 1950), the cumulative risk of opacities for a cumulative exposure to crystalline silica of 2.0 mg/m3-yr was approximately 1.1%; for an average exposure > 0.50 mg/m3 (or hired < 1950), the corresponding cumulative risk was 3.7%. These findings indicate an exposure-response relationship between cumulative exposure to crystalline silica and radiographic opacities; moreover, the relationship was substantially steeper among workers exposed at the highest average concentrations of crystalline silica.

Adult↗
PubMed1998

A case study comparing a meta-analysis and a pooled analysis of studies of sinonasal cancer among wood workers.

A pooled analysis of raw data from 12 case-control studies of sinonasal cancer has recently been conducted by the International Agency for Research on Cancer; the summary odds ratio for all wood-related occupations was 2.0 (95% confidence interval = 1.6-2.5). We have conducted a meta-analysis of the published results of 14 studies on the same topic, including 11 studies from the pooled analysis, and compared the results for several categories of wood workers. Usable results were available for 12 studies: male wood workers had a summary odds ratio of sinonasal cancer of 2.6 (95% confidence interval = 2.1-3.3). The corresponding value based only on the studies that were also included in the pooled analysis was 2.4 (95% confidence interval = 1.9-3.0). When our meta-analysis was based on a relatively large number of studies, results tended to be higher than those of the pooled analysis. As compared with the meta-analysis, the pooled analysis controlled the effect of publication bias by using data from studies for which no specific result was reported, and it reduced misclassification of exposure; the resources used in the pooled analysis, however, were one order of magnitude greater than those needed for the meta-analysis. Whether a pooled analysis of raw data or a meta-analysis should be carried out depends on the research question; we propose some criteria for this decision.

Case-Control Studies↗
PubMed1997

Dose-response associations of silica with nonmalignant respiratory disease and lung cancer mortality in the diatomaceous earth industry.

The potential carcinogenicity of crystalline silica to humans remains a controversial issue. The authors conducted an historical cohort mortality study of 2,342 male workers exposed to crystalline silica, predominantly cristobalite, in a diatomaceous earth mining and processing facility in California. During the years 1942-1994, mortality excesses were detected for nonmalignant respiratory diseases (NMRD) (standardized mortality ratio = 2.01, 95% confidence interval (CI) 1.56-2.55) and lung cancer (standardized mortality ratio = 1.29, 95% CI 1.01-1.61). NMRD mortality rose sharply with cumulative exposure to respirable crystalline silica; allowing for a 15-year latency, the rate ratio for the highest exposure stratum (> or = 5.0 mg/m3-years) was 5.35 (95% CI 2.23-12.8). The rate ratio for lung cancer reached 2.15 (95% CI 1.08-4.28) in the highest exposure category. These associations were unlikely to have been confounded by smoking or asbestos exposure. The findings indicate a strong dose-response relation for crystalline silica and NMRD mortality. The lung cancer results, although less convincing, add further support to an etiologic role for crystalline silica.

Adult↗
PubMed1997

Sinonasal cancer and occupation. Results from the reanalysis of twelve case-control studies.

A pooled reanalysis of twelve case-control studies on sinonasal cancer and occupation from seven countries was conducted in order to study associations with occupations other than wood- and leather-related occupations. The pooled data set included a total of 930 cases (680 men and 250 women) and 3,136 controls (2,349 men and 787 women). All the studies included a detailed occupational history for cases and controls. Each job was coded using the same classifications for occupation and industry. Two approaches were used in the analysis: systematic analysis of occupations; a priori analysis using a preestablished list of occupations and industries. The results confirmed associations observed in several studies not included in this analysis. For agricultural workers, significant excesses were observed for squamous cell carcinoma among women (OR = 1.69) and men (OR = 3.72 for ten years or more of employment as an orchard worker), and adenocarcinomas among men (OR = 2.98 for ten years or more of employment). Associations with textile occupations were observed for adenocarcinoma among women (OR = 2.60) and squamous cell carcinoma among men (OR = 5.09 for fiber preparers, 3.01 for bleachers). Elevated risks for both histologic types were observed among men employed in food manufacturing (OR = 3.25, adenocarcinoma), or as food preservers (OR = 13.9, squamous cell carcinoma), and among men employed as cooks (OR = 1.99, squamous cell carcinoma). A positive association with squamous cell carcinoma was observed for male transport equipment operators (OR = 1.21), and also with adenocarcinoma for male motor-vehicle drivers (OR = 2.50). A number of other associations were observed in the systematic analysis.

Adenocarcinoma↗
PubMed1997

What to do about softwood? A review of respiratory effects and recommendations regarding exposure limits.

Wood dust has been classified as a human carcinogen by the International Agency for Research on Cancer with a footnote that the evaluation was based on a marked excess of sino-nasal cancer among workers exposed primarily to hardwood dusts. Because the epidemiologic data on the carcinogenic effects of softwoods are weaker than for hardwoods, standard setting for softwood dust presents a greater dilemma. Unfortunately, the studies of wood dust and cancer do not have the quantitative exposure data necessary for standard setting for either hardwoods or softwoods. Asthma, non-asthmatic airflow obstruction, and both upper and lower respiratory symptoms have been associated with exposure to both 'allergenic' and 'non-allergenic' softwood dusts, and an association with increasing intensity of exposure has been observed in multiple studies. The available evidence seems to indicate that to prevent these nonmalignant effects, the level of exposure to all softwood dust should be at least as low 2 mg/m3. A standard of 1 mg/m3 may be more appropriate to provide a safety margin to protect more sensitive workers. It may be that some of the health effects observed are due to the natural components of wood, such as resin acids or monoterpenes, or to molds.

Air Pollutants, Occupational↗