Phytoplankton may respond both to elevated temperatures and reduced nutrients by changing their cellular stoichiometry and cell sizes. Since increased temperatures often cause increased thermal stratification and reduced vertical flux of nutrients into the mixed zone, it is difficult to disentangle these drivers in nature. In this study, we used a factorial design with high and low levels of phosphorus (P) and high and low temperature to assess responses in cellular stoichiometry, levels of RNA, and alkaline phosphatase activity (APA) in the chlorophyte Chlamydomonas reinhardtii. Growth rate, C:P, C:N, N:P, RNA, and APA all responded primarily to P treatment, but except for N:P and APA, also temperature contributed significantly. For RNA, the contribution from temperature was particularly strong with higher cellular levels of RNA at low temperatures, suggesting a compensatory allocation to ribosomes to maintain protein synthesis and growth. These experiments suggest that although P-limitation is the major determinant of growth rate and cellular stoichiometry, there are pronounced effects of temperature also via interaction with P. At the ecosystem level, nutrients and temperature will thus interact, but temperatures would likely exert a stronger impact on these phytoplankton traits indirectly via its force on stratification regimes and vertical nutrient fluxes.
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.
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.
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