Natural resource-based industries and prostate cancer risk in Northeastern Ontario: a case-control study.

OBJECTIVE: Prostate cancer continues to be the most commonly diagnosed cancer in men, and there is limited knowledge on its preventable risk factors. A number of occupational exposures in natural resource-based industries are suspected to be related to prostate cancer risk. This study investigates associations between employment in these industries and prostate cancer. METHODS: Data were from a population-based, case-control study previously conducted in Northeastern Ontario. Incident cases (N=760) aged 45-85 years and diagnosed with prostate cancer between 1995 and 1998 were identified from the Ontario Cancer Registry. Controls (N=1632) were recruited using telephone listings, and were frequency matched to cases by age. Lifetime occupational history was collected for all participants. Logistic regression was used to estimate ORs and their associated 95% CIs. RESULTS: Elevated risks were observed for employment in forestry and logging industries (OR=1.87, 95% CI 1.32 to 2.73) and occupations (OR=1.71, 95% CI 1.24 to 2.35), and these risks increased with duration of employment for ≥10 years. Elevated risks were also found for employment in wood products industries (OR=1.45, 95% CI 1.07 to 1.97), and paper and allied products industries (OR=1.43, 95% CI 1.03 to 2.00), and when duration of employment was ≥10 years. There were also elevated risks in agriculture and mining-related work; however, these findings were not consistent across industry and occupation categories. CONCLUSIONS: Prostate cancer risk may be associated with work in several natural resource industries, primarily in the forest industries. To further evaluate observed associations, studies should focus on natural resource-based exposures in larger populations with improved exposure assessment.

Prostate cancer and occupational whole-body vibration exposure.

Prostate cancer is common and its etiology largely unknown; therefore, it is important to explore all potential risk factors that are biologically plausible. Recent literature suggests a relationship between whole-body vibration (WBV) and prostate cancer risk. The aim of this study was to determine whether occupational WBV was a risk factor for prostate cancer. Existing data, collected on 447 incident cases and 532 population controls (or their proxies), in Montreal, Canada, were used to evaluate this question. Personal interviews collected detailed job descriptions for every job held, the tasks involved, and type of equipment used. For each job, experts assessed the intensity and daily duration of WBV exposure. Inter-rater agreement for WBV ratings was examined using the kappa statistic, with values that ranged from 0.83 to 0.94. Logistic regression models explored the relationship between WBV exposure and prostate cancer, using various combinations of intensity, daily duration, and years of exposure. Potential confounders were also examined. Occupations with WBV exposure demonstrated an increased statistically non-significant risk [odds ratio (OR) = 1.44, 95% confidence interval (CI): 0.99-2.09]. The risk for transport equipment operation, a job with WBV exposure, was significantly elevated (OR = 1.90, 95% CI: 1.07-3.39). These results, together with those of an earlier study, suggest that workers in heavy equipment and transport equipment operation may have increased risk of prostate cancer. Further investigation is warranted.

Prostate cancer and driving occupations: could whole body vibration play a role?

PURPOSE: To summarize the literature on the risk of prostate cancer in whole body vibration (WBV) related occupations and estimate a combined meta-rate ratio. METHODS: A systematic review and meta-analysis of five case-control and three cohort studies published between 1996 and 2004 was conducted. A pooled relative risk (RR) estimate was calculated and the studies were evaluated for homogeneity and publication bias. RESULTS: The overall pooled RR estimate was 1.14 (95% CI 0.99-1.30) for the random effects model, based on 17 estimates of relative risk from the eight studies. Significant heterogeneity was found. There was no indication of publication bias. CONCLUSIONS: The increased, though not statistically significant pooled RR for prostate cancer obtained in this meta-analysis indicates that occupational exposure to WBV cannot be ruled out as a possible risk factor for the disease. However, all included studies involved driving occupations with exposure to other risk factors for prostate cancer. Therefore, further epidemiologic studies are needed to better understand this association.

Personal factors influencing agreement between expert and self-reported assessments of an occupational exposure.

This study aimed to identify personal factors associated with expert and respondent agreement on past occupational exposure. Epidemiologic data was collected from 1995 to 1998 in a community-based, case-control study of prostate cancer. Using longest jobs and excluding agreement on "never" exposure, self-reported and expert estimates of ever/ never exposure, by skin or ingestion, to polycyclic aromatic hydrocarbons were compared. Agreement between respondents and the expert was 53.9 percent (N=1,038), with overreporting being more common than underreporting relative to the expert (31.8 percent versus 14.4 percent). In multiple logistic regression models, white-collar occupational status was significantly associated with overreporting (odds ratio [OR] = 0.142; 95 percent confidence interval [CI]: 0.095-0.211; blue-collar versus white-collar), while age was associated with underreporting (OR=1.077; 95 percent CI: 1.043-1.112; one-year increase). Neither job satisfaction nor risk perception appeared to confound other associations. In future studies, overreporting by white-collar workers might be avoided by providing clearer definitions of exposure, whereas elderly respondents may require aids to enhance exposure recall.

Sources of personal exposure to fine particles in Toronto, Ontario, Canada.

Individuals are exposed to particulate matter from both indoor and outdoor sources. The aim of this study was to compare the relative contributions of three sources of personal exposure to fine particles (PM2.5) by using chemical tracers. The study design incorporated repeated 24-hr personal exposure measurements of air pollution from 28 cardiac-compromised residents of Toronto, Ontario, Canada. Each study participant wore the Rupprecht & Patashnick ChemPass Personal Sampling System 1 day a week for a maximum of 10 weeks. During their individual exposure measurement days the subjects reported to have spent an average of 89% of their time indoors. Particle phase elemental carbon, sulfate, and calcium personal exposure data were used in a mixed-effects model as tracers for outdoor PM2.5 from traffic-related combustion, regional, and local crustal materials, respectively. These three sources were found to contribute 13% +/- 10%, 17% +/- 16%, and 7% +/- 6% of PM2.5 exposures. The remaining fraction of the personal PM2.5 is hypothesized to be predominantly related to indoor sources. For comparison, central site outdoor PM2.5 measurements for the same dates as personal measurements were used to construct a receptor model using the same three tracers. In this case, traffic-related combustion, regional, and local crustal materials were found to contribute 19% +/- 17%, 52% +/- 22%, and 10% +/- 7%, respectively. Our results indicate that the three outdoor PM2.5 sources considered are statistically significant contributors to personal exposure to PM2.5. Our results also suggest that among the Toronto subjects, who spent a considerable amount of time indoors, exposure to outdoor PM2.5 includes a greater relative contribution from combustion sources compared with outdoor PM2.5 measurements where regional sources are the dominant contributor.

Medical history, sexual, and maturational factors and prostate cancer risk.

PURPOSE: Sexual, physical, and medical factors were investigated in a case-control study of prostate cancer. METHODS: This population-based study, conducted from 1995 to 1999 in northeastern Ontario, used cancer registry-identified cases (n=760), aged 45 to 84 years, diagnosed between 1995 and 1998. Age-frequency matched controls (n=1632) were obtained from telephone listings. Two separate logistic regression analyses considered: 1) sexual and physical; and 2) medical factors. RESULTS: For the sexual-physical model, marital status, family income, maximum height, number of marriages, having children, age at first marriage, birth, and needing to shave, and acne were not significantly related to risk. In the medical model, a family history of prostate cancer (OR, 2.99; 95% CI, 2.21-4.04) and history of venereal disease (OR, 2.12; 95% CI, 1.27-3.53) were associated with significantly increased risk. A history of allergies (OR, 0.78; 95% CI, 0.60-1.00), benign prostatic hyperplasia (OR, 0.63; 95% CI, 0.49-0.81), and an annual physical exam (OR, 0.43; 95% CI, 0.21-0.85) were associated with reduced risk. Other factors considered in the medical conditions model, body mass index, smoking non-filter cigarettes, and family income were not associated with prostate cancer. CONCLUSIONS: This study is consistent with other studies that suggest that infectious agents may be involved in prostate cancer development.

Development of models to predict dose of pesticides in professional turf applicators.

Epidemiologic studies designed to assess the chronic effects of pesticides are limited by inadequate measurements of exposures. Although cohort studies have been initiated to evaluate the effects of 2,4-dichlorophenoxyacetic acid (2,4-D) and other pesticides in professional turf applicators, they may have limited power to detect significant health risks and may be subject to bias from exposure measurement error. In this study, the doses of 2,4-D, mecoprop [2-(4-chloro-2 methylphenoxy) propionic acid, MCPP] and dicamba (3,6-dichloro-o-anisic acid) were evaluated in a group of 98 professional turf applicators from 20 companies across southwestern Ontario. During a 1-week period (Saturday to Thursday), the volume of pesticide (active ingredient) applied was only weakly related to the total dose of 2,4-D absorbed (R(2)=0.21). Two additional factors explained a large proportion of variation in dose: the type of spray nozzle used and the use of gloves while spraying. Individuals who used a fan-type nozzle had significantly higher doses than those who used a gun-type nozzle. Glove use was associated with significantly lower doses. Job satisfaction and current smoking influenced the dose but were not highly predictive. In the final multiple regression models predicting total absorbed dose of 2,4-D and mecoprop, approximately 63-68% of the variation was explained. The future application of these models for epidemiologic research will depend on the availability of information and records from employers, the feasibility of contacting study subjects and cost.

Prostate cancer risk and diet, recreational physical activity and cigarette smoking.

Associations between prostate cancer and dietary factors, physical activity and smoking were assessed based on data from a population-based case-control study. The study was conducted among residents of northeastern Ontario. Cases were identified from the Ontario Cancer Registry and diagnosed between 1995 and 1998 at ages 50 to 84 years (N=752). Male controls were identified from telephone listings and were frequency matched to cases on age (N=1,613). Logistic regression analyses investigated history of diet, physical activity and smoking as potential risk factors. Tomato intake had a significant positive association with prostate cancer risk for highest versus lowest quartiles (OR=1.6; 95 percent CI: 1.2-2.0). Associations were observed for tomato or vegetable juices and ketchup (OR=1.5; 95 percent CI: 1.2-1.9; OR=1.2; 95 percent CI: 1.0-1.5, respectively). Neither other dietary variables nor smoking were associated with prostate cancer risk. Strenuous physical activity by men in their early 50s was associated with reduced risk (OR=0.8; 95 percent CI: 0.6-0.9). While the recreational physical activity association was consistent with results from previous studies, the tomato products association was not.

Occupational risk factors for prostate cancer.

BACKGROUND: Occupational risk factors for prostate cancer have been investigated with inconsistent findings. METHODS: This was a population-based case-control study of men in Northeastern Ontario, Canada. Cases (n = 760) were from the Ontario Cancer Registry, 50 to 84 years old, and diagnosed with prostate cancer between 1995 and 1998. Age-frequency matched controls (n = 1,632) were obtained from telephone listings. A questionnaire yielded information on occupational history and self-reported exposures to a list of occupational hazards. Exposures to these hazards were assessed by an occupational hygienist. RESULTS: An odds ratio estimate (OR) of 1.21 (95 percent confidence interval (% CI) 1.01, 1.46) was found for employment in trades, transport and equipment operators and related occupations, possibly related to exposure to whole-body vibration (OR = 1.38, 95% CI 1.07, 1.78). For the highest quartile of lifetime cumulative workplace physical activity an OR of 1.33 (95% CI 1.02, 1.74) was found. No statistically significant associations were found for any other occupational category or exposure. CONCLUSIONS: This study does not provide strong evidence for significant occupational risk factors for prostate cancer. However, whole-body vibration exposures, as well as physical activity, may be worth pursuing in future occupational studies.

Associations between personal exposures and fixed-site ambient measurements of fine particulate matter, nitrogen dioxide, and carbon monoxide in Toronto, Canada.

A longitudinal study investigating personal exposures to PM(2.5), nitrogen dioxide (NO(2)), and carbon monoxide (CO) for cardiac compromised individuals was conducted in Toronto, Canada. The aim of the study was (1) to examine the distribution of exposures to PM(2.5), NO(2), and CO; and (2) to investigate the relationship between personal exposures and fixed-site ambient measurements of PM(2.5), NO(2), and CO. In total, 28 subjects with coronary artery disease wore the Rupprecht & Patashnick ChemPass Personal Sampling System one day a week for a maximum of 10 weeks. The mean (SD) personal exposures were 22 microg m(-3) (42), 14 p.p.b. (6), and 1.4 p.p.m (0.5) for PM(2.5), NO(2), and CO, respectively. PM(2.5) and CO personal exposures were greater than central fixed-site ambient measurements, while the reverse pattern was observed for NO(2). Ambient PM(2.5) and NO(2) were correlated with personal exposures to PM(2.5) and NO(2) with median Spearman's correlation coefficients of 0.69 and 0.57, respectively. The correlations between personal exposures and ambient measurements made closest to the subjects' homes or the average of all stations within the study were not stronger than the correlation between personal exposures and central fixed-site measurements. Personal exposures to PM(2.5) were correlated with personal exposures to NO(2) (median Spearman's correlation coefficient of 0.43). This study suggests that central fixed-site measurements of PM(2.5) and NO(2) may be treated as surrogates for personal exposures to PM(2.5) and NO(2) in epidemiological studies, and that NO(2) is a potential confounder of PM(2.5).

Pesticide exposures in professional turf applicators, job titles, and tasks performed: implications of exposure measurement error for epidemiologic study design and interpretation of results.

BACKGROUND: Little information on the validity of job title and task classifications, for the prediction of pesticide use or exposure, is available. METHODS: Job titles and task classifications were evaluated in relation to the absorbed dose of herbicides in 98 professional turf applicators. Self-reported use over a 1-week period and other proxies of pesticide use were compared with employer records. RESULTS: Job titles and tasks performed explained (R(2)) 11% and 16% of the variation in dose, respectively. Individuals who sprayed pesticides only, had the highest average doses in the study followed by those spraying and mixing, and those mixing only. The use of 2,4-D products by individual workers over a work season was not related to standardized measures of the amount purchased or used at the company. CONCLUSIONS: These findings suggest that job titles and tasks performed are poor proxies of pesticide use and exposures in professional turf applicators.