Exposure to benzene and other hydrocarbons and risk of bladder cancer among male offshore petroleum workers.

BACKGROUND: Occupational exposures constitute the second leading cause of urinary bladder cancer after tobacco smoking. Increased risks have been found in the petroleum industry, but high-quality exposure data are needed to explain these observations. METHODS: Using a prospective case-cohort design, we analysed 189 bladder cancer cases (1999-2017) and 2065 randomly drawn non-cases from the Norwegian Offshore Petroleum Workers cohort. Cases were identified in the Cancer Registry of Norway, while work histories (1965-1998) and lifestyle factors were recorded by questionnaire at baseline (1998). Occupational petroleum-related hydrocarbon exposures were assessed by expert-developed job-exposure matrices. Hazard ratios were estimated by weighted Cox-regressions, adjusted for age, tobacco smoking, education, and year of first employment, and with lagged exposures. RESULTS: Increased risks were found in benzene-exposed workers, either long-term exposure (≥18.8 years, HR = 1.89, 95% CI: 1.14-3.13; p-trend = 0.044) or high-level cumulative benzene exposure (HR = 1.60, 95% CI: 0.97-2.63; p-trend = 0.065), compared with the unexposed. Associations persisted with 20-year exposure lag. No associations were found with skin or inhalation exposure to crude oil, mineral oil (lubrication, hydraulics, turbines, drilling), or diesel exhaust. CONCLUSIONS: The results suggest that exposures in the benzene fraction of the petroleum stream may be associated with increased bladder cancer risk.

Night shift work and risk of aggressive prostate cancer in the Norwegian Offshore Petroleum Workers (NOPW) cohort.

BACKGROUND: Night shift work may acutely disrupt the circadian rhythm, with possible carcinogenic effects. Prostate cancer has few established risk factors though night shift work, a probable human carcinogen, may increase the risk. We aimed to study the association between night shift work and chlorinated degreasing agents (CDAs) as possible endocrine disrupters in relation to aggressive prostate cancer as verified malignancies. METHODS: We conducted a case-cohort study on 299 aggressive prostate cancer cases and 2056 randomly drawn non-cases in the Norwegian Offshore Petroleum Workers cohort (1965-98) with linkage to the Cancer Registry of Norway (1953-2019). Work history was recorded as years with day, night, and rollover (rotating) shift work, and CDA exposure was assessed with expert-made job-exposure matrices. Weighted Cox regression was used to estimate hazard ratios (HRs) and 95% confidence intervals (CIs) for aggressive prostate cancer, adjusted for education and year of first employment, stratified by 10-year birth cohorts, and with 10, 15, and 20 years of exposure lag periods. RESULTS: Compared with day work only, an increased hazard of aggressive prostate cancer (HR = 1.86, 95% CI 1.18-2.91; P-trend = 0.046) was found in workers exposed to ≥19.5 years of rollover shift work. This persisted with longer lag periods (HR = 1.90, 95% CI 0.92-3.95; P-trend = 0.007). The exposure-hazard curve for a non-linear model increased linearly (HRs ≥1.00) for 18-26 years of rollover shift work. No association was found with CDA exposure. CONCLUSIONS: Long-term exposure to rollover shift work may increase the hazard of aggressive prostate cancer in offshore petroleum workers.

Night shift work, chemical coexposures and risk of female breast cancer in the Norwegian Offshore Petroleum Workers (NOPW) cohort: a prospectively recruited case-cohort study.

OBJECTIVES: This study examined the association between night shift work and risk of breast cancer, overall and by hormone receptor subtype, among females in the Norwegian Offshore Petroleum Workers (NOPW) cohort. We also examined the association of coexposure (chlorinated degreasers and benzene) and breast cancer risk, and possible interaction with work schedule. DESIGN: Prospectively recruited case-cohort study within the NOPW cohort. SETTING: Female offshore petroleum workers active on the Norwegian continental shelf. PARTICIPANTS: 600 female workers (86 cases and 514 non-cases) were included in the study. We excluded workers that died or emigrated before start of follow-up, had missing work history, were diagnosed with breast cancer or other prior malignancy (except non-melanoma skin cancer) before start of follow-up. RESULTS: No overall association was found between breast cancer risk and work schedule (HR 0.87, 95% CI 0.52 to 1.46 for work schedule involving night shift vs day shift only). There was no significant association between work schedule and risk of any breast cancer subtype. No significant interactions were found between work schedule and chemical coexposures (breast cancer overall Pinteraction chlorinated degreasers=0.725 and Pinteraction benzene=0.175). CONCLUSIONS: Our results did not provide supporting evidence that work schedule involving night shift affects breast cancer risk in female offshore petroleum workers, but should be considered cautiously due to few cases. Further studies with larger sample sizes are warranted.

Ultraviolet radiation and risk of cutaneous melanoma and squamous cell carcinoma in males and females in the Norwegian Offshore Petroleum Workers cohort.

BACKGROUND: Increased risk of cutaneous melanoma and squamous cell carcinoma (SCC) has been reported among petroleum workers, but few studies include females, exposure data on ultraviolet radiation (UVR), and potential confounding factors. We aimed to examine UVR exposure in relation to risk of melanoma and SCC among male and female offshore petroleum workers. We also examined the association between UVR exposure and melanoma (Breslow) thickness. METHODS: The Norwegian Offshore Petroleum Workers (NOPW) cohort (n = 27,917) holds information on sunbathing, indoor tanning, sunburns, sunscreen use, and other lifestyle factors recorded in 1998. Linkage to the Cancer Registry of Norway gave information on cancer diagnosis through 2017. We used Cox and logistic regression to estimate hazard ratios (HRs) of skin cancer and odds ratios (OR) of thick (≥1 mm) melanomas, respectively, with 95% confidence intervals (CIs). RESULTS: Melanoma risk increased with increasing frequency of sunbathing after age 20 (ptrend = 0.031), sunburn average intensity (ptrend = 0.028), and sunscreen use (HR = 2.16; 95% CI: 1.42 -3.27 for almost always vs. never/rarely). The risk of thick melanoma was inversely associated with sunbathing frequency after age 20 (OR = 0.38; 95% CI: 0.16 - 0.90 for ≥4 weeks/year vs. 1 week/year). SCC risk increased with increasing frequency of indoor tanning after age 20 (HR = 2.72; 95% CI: 1.22 - 6.05 for ≥3 times/months vs. never), sunburn average intensity (ptrend < 0.001), and sunscreen use (ptrend < 0.001). CONCLUSIONS: Our results support associations between UVR exposure and skin cancer risk in male and female offshore petroleum workers. This occupational group may be especially relevant for targeted sun protection advice.

Self-reported Occupational Exposures Relevant for Cancer among 28,000 Offshore Oil Industry Workers Employed between 1965 and 1999.

The objective of this study was to examine self-reported frequency of occupational exposure reported by 28,000 Norwegian offshore oil workers in a 1998 survey. Predictors of self-reported exposure frequency were identified to aid future refinements of an expert-based job-exposure-time matrix (JEM). We focus here on reported frequencies for skin contact with oil and diesel; exposure to oil vapor from shaker, to exhaust fumes, vapor from mixing chemicals used for drilling, natural gas, chemicals used for water injection and processing, and to solvent vapor. Exposure frequency was reported by participants as the exposed proportion of the work shift, defined by six categories, in their current or last position offshore (between 1965 and 1999). Binary Poisson regression models with robust variance were used to examine the probabilities of reporting frequent exposure (≥¼ vs. <¼ of work shift) according to main activity, time period, supervisory position, type of company, type of installation, work schedule, and education. Holding a non-supervisory position, working shifts, being employed in the early period of the offshore industry, and having only compulsory education increased the probability of reporting frequent exposure. The identified predictors and group-level patterns may aid future refinement of the JEM previously developed for the present cohort.

Suggested excess of occupational cancers in Norwegian offshore workers: preliminary results from the Cancer Registry Offshore Cohort.

OBJECTIVE: The aim of this communication was to report the overall incidence of cancer in a cohort of male Norwegian offshore oil workers. METHODS: The Offshore Cohort was comprised of >25,000 men who were employed at installations in the North Sea in the period 1965-1999, and who responded to a questionnaire that included work history offshore, other occupational experience, education, leisure-time activities, and lifestyle factors. Calculating standardized incidence ratios (SIR), we compared the number of prospective incident cancers diagnosed between 1999 and 2005 with those expected for age-, gender- and period-specific rates in the general Norwegian population. RESULTS: The overall cancer incidence did not differ from that of the reference population [SIR=1.0, 95% -confidence interval (95% CI) 1.0-1.1, N=695]. There were indications of excess risks of acute myeloid leukemia (SIR=2.0, 95% CI 1.0-3.7) and cancer of the pleura (SIR=2.2, 95% CI 0.9-4.6). No data on occupational history was used in these preliminary analyses. CONCLUSIONS: The cohort was relatively young and an extended observation period would be important for in-depth analyses. The suggested excess of leukemia and cancer of the pleura may be linked to occupational exposure during employment offshore; this issue needs to be addressed in further studies.