Learning from the COVID-19 pandemic among migrants: An innovative, system-level, interdisciplinary approach is needed to improve public health.

The effects of the COVID-19 pandemic are amplified among socially vulnerable groups, including international migrants, in terms of both disease transmission and outcomes and the consequences of mitigation measures. Migrants are overrepresented in COVID-19 laboratory-confirmed cases, hospital admissions, intensive care treatment and death statistics in all countries with available data. A syndemic approach has been suggested to understand the excess burden in vulnerable populations. However, this has not stopped the unequal burden of disease in Norway. Initially, the disease was mainly imported by Norwegians returning from skiing holidays in the Alps, and the prevalence of infection among migrants in Norway, defined as people born abroad to foreign parents, was low. Later, confirmed cases in migrants increased and have remained stable at 35-50% - more than twice the proportion of the migrant population (15%). To change this pattern, we need to understand the complex mechanisms underlying inequities in health and their relative and multiplying impacts on disease inequalities and to test the effect of counterfactual policies in order to reduce inequalities in disease burden. Yet, the current paradigm in the field of migration and health research, that is, the theories, research methods and explanatory models commonly applied, fail to fully understand the differences in health outcomes between international migrants and the host population. Here, we use the Norwegian situation as a case to explain the need for an innovative, system-level, interdisciplinary approach at a global level.

Fixed wavelength fluorescence (FF) of bile as a monitoring tool for polyaromatic hydrocarbon exposure in fish: an evaluation of compound specificity, inner filter effect and signal interpretation.

Fixed wavelength fluorescence (FF) of bile has been evaluated as a monitoring tool for the screening of polyaromatic hydrocarbon (PAH) contamination in fish. The methodology was studied through laboratory and field experiments with Atlantic cod (Gadus morhua L.) and flounder (Platichthys flesus L.) exposed to various forms of PAH contamination. The present study demonstrates the ability of FF screening to discriminate between 2-, 4- and 5-ring PAH metabolites by using the wavelength pairs 290/335 nm, 341/383 nm and 380/430 nm, respectively. In general, the degree of fluorescence interference between these metabolite groups appears to be low. Dose- and time-response patterns of the FF signals were shown to give a good reflection of the PAH exposure. Further, the necessity of an appropriate dilution of bile samples prior to fluorescence measurements is demonstrated by a study of inner filter effect. Normally a dilution of 1000-2000-fold is necessary. Individual differences in the bile density, e.g. measured as the concentration of the bile pigment biliverdin, have to be allowed for when applying the FF method. However, it is shown that normalizing the FF signals to biliverdin concentrations on an individual basis added extra error to the data set. The simple, rapid and cost-effective FF method is found to be well suited for screening fish for PAH contamination.

Interaction of benzo[a]pyrene, 2,3,3',4,4',5 hexachlorobiphenyl (PCB 156) and cadmium on biomarker responses in flounder (Platichthys flesus L.).

Interactive effects of a mixed pollutant exposure on biomarker responses were studied in European flounder (Platichthys flesus L.). The model chemicals, benzo[a]pyrene (BaP, 2.5 mg kg(-1)), 2,3,3',4,4'5 hexachlorobiphenyl (PCB-156, 2.5 mg kg(-1)), and cadmium (cadmium, 1 mg kg(-1)), were administered to fish by subcutaneous injections. Biomarker responses were quantified both following administration of single chemicals and sequential combinations of the chemicals in pairs. Significant induction of CYP1A protein levels and corresponding ethoxyresorufin-O-deethylase (EROD) activities was observed in BaP and PCB treated flounder after 2 and 8 days, respectively. The strongest induction (44 fold) was caused by BaP. No further induction was observed after additional treatment with PCB 156. CYP1A induction caused by BaP was inhibited (40% compared with BaP treatment alone) in flounder pre treated with cadmium, whereas induction by PCB 156 appeared to be unaffected by pre treatment with cadmium. Flounder treated with cadmium only had significantly elevated hepatic levels of metallothionein (MT) after 15 days. Pre treatment with BaP and PCB prior to cadmium inhibited the MT induction (30-50%) compared with cadmium alone. Furthermore, significantly higher glutathione S transferase activities were observed in flounder administered cadmium alone, and in flounder treated with BaP or PCB 156 prior to cadmium. GST selenium independent peroxidase activities appeared to be unaffected by any of the treatments in the present study. The results indicate that chemical mixtures may affect biomarker responses differently from compounds administered alone, and that the sensitivity of both CYP1A and MT are influenced by pollutants other than their primary inducers.