Priority issues in occupational cancer research: Ontario stakeholder perspectives

INTRODUCTION

Workers are potentially exposed to known and suspected carcinogens in the workplace, many of which have not been fully evaluated. Despite persistent need, research on occupational cancer appears to have declined in recent decades. The formation of the Occupational Cancer Research Centre (OCRC) is an effort to counter this downward trend in Ontario. The OCRC conducted a survey of the broad stakeholder community to learn about priority issues on occupational cancer research.

METHODS

The OCRC received 177 responses to its survey from academic, health care, policy, industry, and labour-affiliated stakeholders. Responses were analyzed based on workplace exposures, at-risk occupations and cancers by organ system, stratified by respondents' occupational role.

DISCUSSION

Priority issues identified included workplace exposures such as chemicals, respirable dusts and fibres (e.g. asbestos), radiation (e.g. electromagnetic fields), pesticides, and shift work; and occupations such as miners, construction workers, and health care workers. Insufficient funding and a lack of exposure data were identified as the central barriers to conducting occupational cancer research.

CONCLUSION

The results of this survey underscore the great need for occupational cancer research in Ontario and beyond. They will be very useful as the OCRC develops its research agenda.

Physical activities and future risk of Parkinson disease

OBJECTIVE

To prospectively investigate the relationship between physical activity and Parkinson disease (PD).

METHODS

We evaluated physical activity in relation to PD among 213,701 participants of the NIH-AARP Diet and Health Study cohort. Physical activities over 4 periods (ages 15-18, 19-29, and 35-39, and in the past 10 years) were noted in 1996-1997, and physician-diagnosed PD was reported on the 2004-2006 follow-up questionnaire. Only cases diagnosed after 2000 (n = 767) were included in the analyses.

RESULTS

Higher levels of moderate to vigorous activities at ages 35-39 or in the past 10 years as reported in 1996-1997 were associated with lower PD occurrence after 2000 with significant dose-response relationships. The multivariate odds ratios (OR) between the highest vs the lowest levels were 0.62 (95% CI confidence interval [CI] 0.48-0.81, p for trend 0.005) for ages 35-39 and 0.65 (95% CI 0.51-0.83, p for trend 0.0001) for in the past 10 years. Further analyses showed that individuals with consistent and frequent participation in moderate to vigorous activities in both periods had approximately a 40% lower risk than those who were inactive in both periods. Moderate to vigorous activities at earlier ages or light activities were not associated with PD. Finally, the association between higher moderate to vigorous physical activities and lower PD risk was demonstrated in a metaanalysis of prospective studies.

CONCLUSIONS

Although we cannot exclude the possibility that less participation in physical activity is an early marker of PD, epidemiologic evidence suggests that moderate to vigorous exercise may protect against PD.

Differential effects of smoking on lung cancer mortality before and after household stove improvement in Xuanwei, China

Background:

In Xuanwei County, Yunnan Province, China, lung cancer mortality rates in both males and females are among the highest in China.

Methods:

We evaluated differential effects of smoking on lung cancer mortality before and after household stove improvement with chimney to reduce exposure to smoky coal emissions in the unique cohort in Xuanwei, China. Effects of independent variables on lung cancer mortality were measured as hazard ratios and 95% confidence intervals using a multivariable Cox regression model that included separate time-dependent variables for smoking duration (years) before and after stove improvement.

Results and conclusion:

We found that the effect of smoking on lung cancer risk becomes considerably stronger after chimney installation and consequent reduction of indoor coal smoke exposure.

Smoking duration, intensity, and risk of Parkinson disease

OBJECTIVE

To evaluate the relative importance of smoking duration vs intensity in reducing the risk of Parkinson disease (PD).

METHODS

The study included 305,468 participants of the NIH-AARP Diet and Health cohort, of whom 1,662 had a PD diagnosis after 1995. We estimated odds ratios (OR) and 95% confidence intervals from multivariate logistic regression models.

RESULTS

Compared with never smokers, the multivariate ORs were 0.78 for past smokers and 0.56 for current smokers. Among past smokers, a monotonic trend toward lower PD risk was observed for all indicators of more smoking. Stratified analyses indicated that smoking duration was associated with lower PD risk within fixed intensities of smoking. For example, compared with never smokers, the ORs among past smokers who smoked >20 cigarettes/day were 0.96 for 1-9 years of smoking, 0.78 for 10-19 years, 0.64 for 20-29 years, and 0.59 for 30 years or more (p for trend = 0.001). In contrast, at fixed duration, the typical number of cigarettes smoked per day in general was not related to PD risk. Close examination of smoking behaviors in early life showed that patients with PD were less likely to be smokers at each age period, but if they smoked, they smoked similar numbers of cigarettes per day as individuals without PD.

CONCLUSIONS

This large study suggests that long-term smoking is more important than smoking intensity in the smoking-Parkinson disease relationship.

Residential proximity to industrial facilities and risk of non-Hodgkin lymphoma

Industrial pollution has been suspected as a cause of non-Hodgkin lymphoma (NHL), based on associations with chemical exposures in occupational studies. We conducted a case-control study of NHL in four SEER regions of the United States, in which residential locations of 864 cases and 684 controls during the 10 years before recruitment were used to characterize proximity to industrial facilities reporting chemical releases to the Environmental Protection Agency's Toxics Release Inventory (TRI). For each of 15 types of industry (by 2-digit SIC code), we evaluated the risk of NHL associated with having lived within 2 miles of a facility, the distance to the nearest facility (miles categories of < or =0.5, >0.5-1.0, >1.0-2.0, >2 [referent]), and the duration of residence within 2miles (years categories of 10, 1-9, 0 [referent]), using logistic regression. Increased risk of NHL was observed in relation to lumber and wood products facilities (SIC 24) for the shortest distance of residential proximity (< or =0.5 mile: odds ratio [OR]=2.2, 95% confidence interval [CI]: 0.4-11.8) or the longest duration (10 years: OR=1.9, 95% CI: 0.8-4.8); the association with lumber facilities was more apparent for diffuse large B-cell lymphoma (lived within 2 miles: OR=1.7, 95% CI: 1.0-3.0) than for follicular lymphoma (OR=1.1, 95% CI: 0.5-2.2). We also observed elevated ORs for the chemical (SIC 28, 10 years: OR=1.5, 95% CI: 1.1-2.0), petroleum (SIC 29, 10 years: OR=1.9, 95% CI: 1.0-3.6), rubber/miscellaneous plastics products (SIC 30, < or =0.5mile: OR=2.7, 95% CI: 1.0-7.4), and primary metal (SIC 33, lived within 2miles: OR=1.3, 95% CI: 1.0-1.6) industries; however, patterns of risk were inconsistent between distance and duration metrics. This study does not provide strong evidence that living near manufacturing industries increases NHL risk. However, future studies designed to include greater numbers of persons living near specific types of industries, along with fate-transport modeling of chemical releases, would be informative.

Portable stove use is associated with lower lung cancer mortality risk in lifetime smoky coal users

Domestic fuel combustion from cooking and heating, to which about 3 billion people worldwide are exposed, is associated with increased lung cancer risk. Lung cancer incidence in Xuanwei is the highest in China, and the attributable risk of lung cancer from unvented smoky coal burning is greater than 90%. To evaluate any lung cancer mortality reduction after changing from unvented stoves to portable stoves, we used lifetime smoky coal users in a retrospective cohort of all farmers born during 1917–1951 and residing in Xuanwei in 1976. Of the 42 422 enrolled farmers, 4054 lifetime smoky coal users changed to portable stoves, 4364 did not change, and 1074 died of lung cancer. Lung cancer morality associated with stove change was assessed by product-limit survival curves and multivariate Cox regression models. Both men (P<0.0001) and women (P<0.0001) who changed to portable stoves had a significantly increased probability of survival compared with those who did not change. Portable stoves were associated with decreased risk of lung cancer mortality in male participants (hazard ratio (HR)=0.62, 95% confidence interval (CI)=0.46–0.82) and female participants (HR=0.41, 95% CI=0.29–0.57). Portable stove use is associated with reduced lung cancer mortality risk, highlighting a cost-effective intervention that could substantially benefit health in developing countries.

Degreasing and risk of non-Hodgkin lymphoma

OBJECTIVE

To investigate the relationship between selected solvent-related workplace tasks (degreasing, painting, gluing, stripping paint, staining) and risk of non-Hodgkin lymphoma (NHL).

METHODS

We analysed occupational data from a large population-based case-control study of NHL conducted in the USA. For participants reporting occupations with possible exposure to organic solvents, job-specific interview modules were administered to elicit in-depth information on solvent-related workplace tasks and other exposure-related factors (225 cases, 189 controls). Unconditional logistic regression models were fit to calculate odds ratios (ORs) and 95% CI for average frequency, maximal frequency and cumulative number of hours having performed each task. Individuals with jobs rated as unexposed to organic solvents in the workplace (180 cases, 213 controls) were used as a reference group.

RESULTS

We observed an increased risk of NHL among subjects in the highest category of maximal degreasing frequency (>520 h/year: OR 2.1, 95% CI 0.9 to 4.9, trend test p = 0.02). We found similar associations for the highest levels of average frequency and, among men, cumulative number of hours. Other solvent-related tasks were not associated with NHL.

CONCLUSION

Findings from this case-control analysis of solvent-related tasks suggest that frequent degreasing work may be associated with an elevated risk of NHL.

Occupation/industry and risk of non-Hodgkin's lymphoma in the United States

AIMS

To identify occupations and industries associated with non-Hodgkin's lymphoma (NHL) in a large population-based, case-control study in the USA.

METHODS

Cases (n = 1189) of histologically confirmed malignant NHL ages 20-74 were prospectively identified in four geographic areas covered by the National Cancer Institute SEER Program. Controls (n = 982) were selected from the general population by random digit dialling (<65 years of age) and from residents listed in Medicare files (65-74 years of age). Odds ratios and 95% confidence intervals for occupations and industries were calculated by unconditional logistic regression analyses, adjusting for age, gender, ethnicity and study centre. Further analyses stratified for gender and histological subtype were also performed.

RESULTS

Risk of NHL was increased for a few occupations and industries. Several white collar occupations, with no obvious hazardous exposures, had elevated risks, including purchasing agents and buyers, religious workers, physical therapists and information clerks. Occupations with excesses that may have exposures of interest include launderers and ironers, service occupations, food/beverage preparation supervisors, hand packers and packagers, roofing and siding, leather and leather products, transportation by air, nursing and personal care facilities, and specialty outpatient clinics. Significantly decreased risks of NHL were found for a number of occupations and industries including post-secondary teachers and chemical and allied products.

CONCLUSIONS

The results of this study suggest that several occupations and industries may alter the risk of NHL. Our results support previously reported increased risks among farmers, printers, medical professionals, electronic workers and leather workers. These findings should be evaluated further in larger studies that have the power to focus on specific exposures and histological subtypes of NHL.

Multicenter study on in vitro characterization of dendritic cells

BACKGROUND

There is growing interest in the use of in vitro-expanded dendritic cells (DC) in cancer immunotherapy as cellular-based vaccines. However, the methods used for in vitro preparation vary widely between institutions. Therefore, a strong need exists for standardization, characterization and quality control (QC) of such vaccines. A first prospective multicenter pilot study was performed to investigate basic QC parameters of frozen/thawed DC. The study design was focused on comparison of test results for cell counts, immunophenotyping and cell viability.

METHODS

CD14+ monocytes were isolated from three healthy volunteers. The cells were expanded in vitro, matured and cryopreserved using a standardized protocol in one laboratory. The aliquots of cryopreserved DC and a panel of reagents were shipped to eight laboratories worldwide. The objective was to compare the results of non-functional QC assays between sites by testing identical DC vaccines and using a pre-defined test protocol.

RESULTS

Measurements of nucleated cell (NC) content of thawed DC vaccines with different types of hematology analyzers (HA) gave similar results for the majority of sites. Immunophenotyping using identical clones of monoclonal antibodies for the detection of surface antigens (i.e. CD1a, CD14, CD16, CD83, CD86 and HLA-DR) provided mostly comparable results between laboratories with an acceptable level of variation. In contrast, highly different results between study sites were generated for measuring the viability of thawed DC by flow cytometry using 7-amino-actinomycin D (7-AAD) dye exclusion.

DISCUSSION

In characterizing frozen/thawed DC vaccines, NC counts generated by HA yielded similar results between different laboratories. Furthermore, immunophenotyping of DC vaccines can be standardized between centers, i.e. by using identical reagents. Because of highly variable results between laboratories, 7-AAD viability testing of thawed DC needs to be studied further to identify potential causes for the observed variability.

Mortality among shipyard Coast Guard workers: a retrospective cohort study

BACKGROUND

The mortality experience of 4702 (4413 men and 289 women) civilian workers in a US Coast Guard shipyard was evaluated.

METHODS

All workers employed at the shipyard between 1 January 1950 and 31 December 1964 were included in the study and were followed through 31 December 2001 for vital status. Detailed shipyard and lifetime work histories found in the shipyard personnel records and job descriptions were evaluated. Workers were classified as likely exposed to any potential hazardous substances. In addition, 20 job groups were created on likely similar exposures. Standardised mortality ratios (SMRs) were calculated based on the general population of the state and adjusted for age, calendar period, sex and race.

RESULTS

The follow-up was successful for 93.3% of the workers. Among all men employed in the shipyard, there was an excess of mortality from all causes of death (SMR 1.08; 95% CI 1.04 to 1.12), respiratory cancers (SMR 1.29; 95% CI 1.15 to 1.43), lung cancer (SMR 1.26; 95% CI 1.12 to 1.41), mesothelioma (SMR 5.07; 95% CI 1.85 to 11.03) and emphysema (SMR 1.44; 95% CI 1.01 to 1.99) and a decrease for cardiovascular diseases (OR 0.95; 95% CI 0.90 to 1.00), vascular lesions of the central nervous system (SMR 0.80; 95% CI 0.67 to 0.96), cirrhosis of the liver (SMR 0.38; 95% CI 0.25 to 0.57) and external causes of death (SMR 0.55; 95% CI 0.44 to 0.68). A similar pattern was observed for the men classified as exposed. No increasing trend of mortality was found with duration of employment in the shipyard, with the exception of mesothelioma (SMRs of 4.23 and 6.27 for <10 years and > or =10 years, respectively). In occupations with at least three cases and with an SMR of > or =1.3, the authors observed a significantly elevated mortality for lung cancer among machinists (SMR 1.60; 95% CI 1.08 to 2.29) and shipfitters, welders and cutters (SMR 1.34; 95% CI 1.07 to 1.65) and for oral and nasopharyngeal cancers among wood workers (SMR 6.20; 95% CI 2.27 to 13.50).

CONCLUSION

Employment in this Coast Guard shipyard revealed a small but significant excess mortality from all causes, lung cancer and mesothelioma, most of which is probably related to asbestos exposure.

Mechanisms of U46619- and 5-HT-induced contraction of bovine pulmonary arteries: role of chloride ions

BACKGROUND AND PURPOSE

Thromboxane A(2) and 5-hydroxytryptamine (5-HT) are implicated in pulmonary hypertension. The involvement of chloride, voltage-operated calcium channels (VOCCs), store-operated calcium channels (SOCCs) and the Rho kinase in the contractile response of bovine pulmonary arteries (BPA) to the thromboxane A(2) mimetic U46619 and 5-HT was investigated.

EXPERIMENTAL APPROACH

Endothelium-intact ring segments of BPA were mounted in Krebs/Henseleit buffer (37 degrees C) under a tension of 2g and gassed with 95%O(2)/5%CO(2).

KEY RESULTS

Depletion or removal of extracellular chloride, inhibition of chloride and SOCC, Na:K:2Cl, Cl/HCO(3), Rho kinase inhibited contractions to U46619. Combining Rho kinase inhibition and chloride channel blockade (with NPPB) almost abolished the contractions to U46619. In contrast 5-HT-induced contraction was inhibited by verapamil and mibefradil. Depletion of stored calcium with caffeine almost abolished the response to U46619 but not 5-HT. The contraction by the sarco(endo)plasmic reticulum Ca(2+)-ATPase inhibitor CPA was abolished by SOCC and chloride channel blockade (with NPPB) and by chloride depletion.

CONCLUSIONS AND IMPLICATIONS

This study suggests that the contractile response of BPA to U46619 involves Rho kinase together with a chloride-sensitive mechanism, which does not involve VOCC but may have a role in calcium release and calcium entry via SOCC. In contrast contraction of the BPA by 5-HT appears to involve verapamil- and mibefradil-sensitive VOCC. This study may indicate that the use of calcium channel blockers in the management of pulmonary hypertension may not always be effective and that Rho kinase and chloride channels may be targets for the development of new therapies.

Pesticide exposure and self-reported Parkinson's disease in the agricultural health study

Previous studies based on limited exposure assessment have suggested that Parkinson's disease (PD) is associated with pesticide exposure. The authors used data obtained from licensed private pesticide applicators and spouses participating in the Agricultural Health Study to evaluate the relation of self-reported PD to pesticide exposure. Cohort members, who were enrolled in 1993-1997, provided detailed information on lifetime pesticide use. At follow-up in 1999-2003, 68% of the cohort was interviewed. Cases were defined as participants who reported physician-diagnosed PD at enrollment (prevalent cases, n = 83) or follow-up (incident cases, n = 78). Cases were compared with cohort members who did not report PD (n = 79,557 at enrollment and n = 55,931 at follow-up). Incident PD was associated with cumulative days of pesticide use at enrollment (for highest quartile vs. lowest, odds ratio (OR) = 2.3, 95% confidence interval: 1.2, 4.5; p-trend = 0.009), with personally applying pesticides more than half the time (OR = 1.9, 95% confidence interval: 0.7, 4.7), and with some specific pesticides (ORs > or = 1.4). Prevalent PD was not associated with overall pesticide use. This study suggests that exposure to certain pesticides may increase PD risk. Findings for specific chemicals may provide fruitful leads for further investigation.

Established breast cancer risk factors by clinically important tumour characteristics

Breast cancer is a morphologically and clinically heterogeneous disease; however, it is less clear how risk factors relate to tumour features. We evaluated risk factors by tumour characteristics (histopathologic type, grade, size, and nodal status) in a population-based case-control of 2386 breast cancers and 2502 controls in Poland. Use of a novel extension of the polytomous logistic regression permitted simultaneous modelling of multiple tumour characteristics. Late age at first full-term birth was associated with increased risk of large (> 2 cm) tumours (odds ratios (95% confidence intervals) 1.19 (1.07-1.33) for a 5-year increase in age), but not smaller tumours (P for heterogeneity adjusting for other tumour features (Phet) = 0.007). On the other hand, multiparity was associated with reduced risk for small tumours (0.76 (0.68-0.86) per additional birth; Phet = 0.004). Consideration of all tumour characteristics simultaneously revealed that current or recent use of combined hormone replacement therapy was associated with risk of small (2.29 (1.66-3.15)) and grade 1 (3.36 (2.22-5.08)) tumours (Phet = 0.05 for size and 0.0008 for grade 1 vs 3), rather than specific histopathologic types (Phet = 0.63 for ductal vs lobular). Finally, elevated body mass index was associated with larger tumour size among both pre- and postmenopausal women (Phet = 0.05 and 0.0001, respectively). None of these relationships were explained by hormone receptor status of the tumours. In conclusion, these data support distinctive risk factor relationships by tumour characteristics of prognostic relevance. These findings might be useful in developing targeted prevention efforts.