Is PCBs concentration variability between and within freshwater fish species explained by their contamination pathways?

Many chemical, physiological, and trophic factors are known to affect bioaccumulation of polychlorinated biphenyls (PCBs) in biota. Understanding the primary factors affecting fish contamination is critical for predicting and assessing risks to upper-trophic level consumers, including humans. Here we identify PCB contamination pathways that could explain within- and between-species variability in fish concentration levels. Three freshwater river fish species (barbel, chub and bream) were sampled at three sites along the Rhone River (France) where fish consumption is partially prohibited because of PCB levels exceeding the European health-based benchmark. The trophic position was assessed using an innovative approach based on stable isotope analyses and Bayesian inference, which takes into account both isotope data variability and parameter uncertainty. The effect of foraging habitat on fish contamination was addressed using stable isotope mixing models. The fish trophic position and PCB concentrations were found to be unrelated while the exploitation of sediment detrital carbon as a food source appeared to be a critical factor affecting fish contamination. Fish length, PCB concentration of the sediment, and individual fish foraging habitat (exploitation of detrital versus planktonic carbon sources) explained 80% of within- and between-species variability observed in PCB concentrations. These results, obtained for species that have overlapping TPs and exploit different carbon sources, reveal that the important factor in fish PCB contamination is not only what fish consume, but also and essentially the feeding location.

Childhood cancer survival in Cuba.

Reports dealing with childhood cancer population-based survival have not yet been published in Cuba. A survival study including cases reported to the National Cancer Registry in the period 1988-1989 have been accomplished in the National Cancer Registry of Cuba. A comprehensive view of its results in childhood cancer is intended to be shown in this paper. All sites childhood cancer cases aged below 15 years (400) and reported in this period were included derived from a total of 578 incident cases. Vital status of cases was checked-up to December of 1994 by a mixed follow-up. Survival analysis was achieved by the life-table method using the SPSS for Windows software. Relative survival rates were not included because no differences were appreciated with the observed ones. Cases between 0-4 years and females account for the highest frequencies. Leukaemia accounts for 27% of the cases, followed by lymphomas and tumours of the central nervous system. Lymphoid and non-lymphoid acute leukaemia had 41 and 9% 5-year survival rate respectively being the latter comparable with Bangalore, India (10%). For lymphomas, Hodgkin's disease present better prognosis compared with non-Hodgkin lymphoma with 73 and 35% 5-year survival rates, respectively. Figures are comparable to the corresponding to Bangalore, India (72 and 33%, respectively). For time trends survival distribution were compared by period of diagnosis (1982/1988-1989). In all cases differences resulted statistically non-significant with lower rates for 1988-1989 except for lymphomas. International reports show increasing time trends for childhood cancer. Nevertheless, these results may serve as a milestone for future comparisons, corresponding with the creation of the National Program for Childhood Cancer Control and future studies will confirm the success of its measures.