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Environmental monitoring typically assumes samples and sampling activities to be representative of the population being studied. Given a limited budget, an appropriate sampling strategy is essential to support detecting temporal trends of contaminants. In the present study, based on real chemical analysis data on polybrominated diphenyl ethers in snails collected from five subsites in Tianmu Lake, computer simulation is performed to evaluate three sampling strategies by the estimation of required sample size, to reach a detection of an annual change of 5% with a statistical power of 80% and 90% with a significant level of 5%. The results showed that sampling from an arbitrarily selected sampling spot is the worst strategy, requiring much more individual analyses to achieve the above mentioned criteria compared with the other two approaches. A fixed sampling site requires the lowest sample size but may not be representative for the intended study object e.g. a lake and is also sensitive to changes of that particular sampling site. In contrast, sampling at multiple sites along the shore each year, and using pooled samples when the cost to collect and prepare individual specimens are much lower than the cost for chemical analysis, would be the most robust and cost efficient strategy in the long run. Using statistical power as criterion, the results demonstrated quantitatively the consequences of various sampling strategies, and could guide users with respect of required sample sizes depending on sampling design for long term monitoring programs., (Copyright © 2017 Elsevier Ltd. All rights reserved.)

Temporal and spatial trends of perfluoroalkyl acids (PFAAs) were investigated in Baltic Sea herring liver (Clupea harengus) from three sites, and white-tailed sea eagle (WTSE) eggs (Haliaeetus albicilla) from two freshwater and two marine areas in Sweden. Trends of most quantifiable PFAAs increased over the monitored period (1980-2014 in herring, 1960s/1980s-2010 in WTSE). No significant decreasing trends were observed for the most recent ten years for any substances, except perfluorooctane sulfonamide (FOSA). Concentrations of perfluorooctanesulfonic acids (PFOS) in herring showed a distinct decreasing spatial trend moving from the more southern site toward the more northern site, indicating main input of PFOS into the southern Baltic Sea. For WTSE, PFOS concentration was higher in the marine compared to the freshwater environment, explained by the cumulative historic contamination of the Baltic Sea. Similarly, concentrations in WTSE were lower in the northern part of the Baltic Sea compared to further south. Concentrations of PFUnDA, representing long-chain perfluoroalkyl carboxylic acids (PFCAs), showed a more homogeneous spatial distribution compared to PFOS for both herring and WTSE, indicating that atmospheric inputs (via precursors) of the long-chain PFCAs are important contributors in the study areas.

Persistent organic pollutants (POPs) have been of environmental and health concern for more than half a century and have their own intergovernmental regulation through the Stockholm Convention, from 2001. One major concern is the nursing child's exposure to POPs, a concern that has led to a very large number of scientific studies on POPs in mothers' milk. The present review is a report on the assessment on worldwide spatial distributions of POPs and of their temporal trends. The data presented herein is a compilation based on scientific publications between 1995 and 2011. It is evident that the concentrations in mothers' milk depend on the use of pesticides and industrial chemicals defined as POPs. Polychlorinated biphenyls (PCBs) and "dioxins" are higher in the more industrialized areas, Europe and Northern America, whereas pesticides are higher in Africa and Asia and polybrominated diphenyl ethers (PBDEs) are reported in higher concentrations in the USA. POPs are consequently distributed to women in all parts of the world and are thus delivered to the nursing child. The review points out several major problems in the reporting of data, which are crucial to enable high quality comparisons. Even though the data set is large, the comparability is hampered by differences in reporting. In conclusion, much more detailed instructions are needed for reporting POPs in mothers' milk. Temporal trend data for POPs in mothers' milk is scarce and is of interest when studying longer time series. The only two countries with long temporal trend studies are Japan and Sweden. In most cases, the trends show decreasing concentrations of POPs in mothers' milk. However, hexabromocyclododecane is showing increasing temporal concentration trends in both Japan and Sweden.

As the ice cap of the Arctic diminishes due to global warming, the polar sailing route will be open larger parts of the year. These changes are likely to increase the pollution load on the pristine Arctic due to large vessel traffic from specific contaminant groups, such as polycyclic aromatic hydrocarbons (PAHs). A well-documented baseline for PAH concentrations in the biota in the remote regions of the Nordic Seas and the sub-Arctic is currently limited, but will be vital in order to assess future changes in PAH contamination in the region. Blue mussels (Mytilus edulis) were collected from remote sites in Greenland, Iceland, the Faroe Islands, Norway and Sweden as well as from urban sites in the same countries for comparison. Cod (Gadus morhua) was caught north of Iceland and along the Norwegian coast. Sixteen priority PAH congeners and the inorganic trace elements arsenic, cadmium, mercury and lead were analysed in the blue mussel samples as well as PAH metabolites in cod bile. Σ16PAHs ranged from 28 ng/g dry weight (d.w.) (Álftafjörður, NW Iceland) to 480 ng/g d.w. (Ísafjörður, NW Iceland). Mussel samples from Mjóifjörður, East Iceland and Maarmorilik, West Greenland, contained elevated levels of Σ16PAHs, 370 and 280 ng/g d.w., respectively. Levels of inorganic trace elements varied with highest levels of arsenic in mussels from Ísafjörður, Iceland (79 ng/g d.w.), cadmium in mussels from Mjóifjörður, Iceland (4.3 ng/g d.w.), mercury in mussels from Sørenfjorden, Norway (0.23 ng/g d.w.) and lead in mussels from Maarmorilik, Greenland (21 ng/g d.w.). 1-OH-pyrene was only found above limits of quantification (0.5 ng/mL) in samples from the Norwegian coast, ranging between 44 and 140 ng/ml bile. Generally, PAH levels were low in mussels from the remote sites investigated in the study, which indicates limited current effect on the environment., (Copyright © 2014 Elsevier B.V. All rights reserved.)

Within Europe, the Marine Strategy Framework Directive (MSFD) is aimed at addressing the chemical status and quality of the marine environment. One of the main goals is to achieve Good Environmental Status (GES) in the marine environment. Environmental monitoring of biota e.g., Baltic herring and guillemot eggs, is conducted annually in Sweden to follow temporal changes in environmental contaminants. To determine the suitability of guillemot eggs as a sentinel species for investigating GES, we compared temporal trends of polychlorinated dibenzo-p-dioxins and dibenzofurans (PCDD/Fs) and dioxin-like polychlorinated biphenyls (dl-PCBs) in these two species from single sampling sites within Sweden. Lipid content from guillemot eggs was consistently high and stable (yearly mean for >40 years, ∼12%) compared to that of herring (yearly mean for >20 years, ∼3%). A significant decreasing trend of ΣPCDD/F in TEQ WHO1998 was observed in guillemot eggs, but no trend was seen in herring. CB118 significantly decreased in both species, but in the last 10 years this decrease was not significant in herring. A number of advantages, such as high lipid content in the egg and a low coefficient of variation make guillemot suitable as a sentinel species. The advantages and disadvantages of using either guillemot eggs or Baltic herring are compared., (Copyright © 2014 Elsevier Ltd. All rights reserved.)

Choosing an appropriate sampling strategy for chemical analysis within environmental monitoring includes the important decision of whether to sample and store individual or pooled samples. This choice impacts on future analyses from Environmental Specimen Bank samples. A number of advantages exist to support using either individual or pooled samples for temporal trend studies. However, it is important to know the total and analytical variance to be able to design the best sampling strategy. Statistical power in temporal or spatial studies is determined by the random/unexplained sample variation. The relationship between chemical analytical error and other sources of variation, as well as the cost for collection, preparation of samples and chemical analysis, will determine the number of individuals in each pool, and the number of pools that should be analysed to achieve high cost efficiency and good statistical power. Various scenarios of different numbers of individual samples, different numbers of pooled samples containing various numbers of individual specimens, the relationships between chemical analytical error and other sources of sample variance, have been compared by simulating random sampling from computer generated populations using realistic measures of variation from ongoing monitoring activities. These results offer guidance in the design of a cost-efficient, statistically sound sampling strategy., (Copyright © 2013 Elsevier Ltd. All rights reserved.)

Temporal trends of polychlorinated dibenzo-p-dioxins (PCDDs), dibenzofurans (PCDFs) and dioxin-like polychlorinated biphenyls (DL-PCBs) in mothers' milk are still quite rare. Data are particularly scarce when it comes to concentrations from the last decade, 2000 and onwards. The aims of the present study were to assess temporal trends of PCDD, PCDF and DL-PCB in mothers' milk from Stockholm, 1972-2011 and to compare the results with previous analysis of some of the older samples. The samples were analyzed by high resolution GC/MS and results were statistically evaluated for the periods, 1972-2011 and 2002-2011. The rate of which ∑PCDDs, ∑DL-PCBs and the ∑TEQ are decreasing (on pg/g fat WHO-TEQ2005) is higher in the last decade compared to the 40year period, 1972-2011. A similar trend is indicated, but not confirmed, for ∑TEQ of PCDFs, probably due to too many PCDF congeners below LOQ in the period 2002-2011. Concentrations of ∑PCDDs, ∑PCDFs, ∑DLPCBs and ∑TEQ, all expressed as pg/g fat on TEQ-WHO2005-basis, show a statistically significant decline over time, 5.8-6.8% per year, 1972-2011. The last ten years the annual declines for ∑PCDDs, ∑DL-PCBs and ∑TEQ are 9.2-11% and for ∑PCDF, 5.4%. Congener specific trend analysis, 2002-2001, of PCDDs and DL-PCBs showed the same pattern, while the PCDF congeners showed no such general trend. The results from the re-analysis showed good agreement with slightly lower ∑TEQ1998 pg/g fat concentrations in six out of seven samples and mean difference of 13% in ∑TEQ1998. The study shows that time series can be elongated from previous studies, as long as the sample population remains the same., (© 2013.)

To categorize the marine environmental health status, the Oslo and Paris commissions have recently formulated Ecological Quality Objectives (EcoQOs) for many ecological features including the contamination of coastal bird eggs with mercury and organochlorines. In this study, we describe spatial and temporal patterns of egg contamination around the North Sea and compared them to the EcoQOs. Concentrations of mercury, polychlorinated biphenyl (ΣPCB) congeners, dichlorodiphenyltrichloroethane (ΣDDT) and derivatives, hexachlorobenzene (HCB) and hexachlorocyclohexane (ΣHCH) isomers were analysed in two tern species (Sterna hirundo and Sterna paradisaea) and Oystercatcher (Haematopus ostralegus) eggs collected between 2008 and 2010 in a total of 21 sites in seven countries surrounding the North Sea. Hg, ΣPCB and HCB were highest in the southern sites, while ΣDDT and ΣHCH concentrations were greatest in eggs from the western North Sea and the Elbe estuary. There were rarely any consistent decreases over time for any compounds. In the terns, Hg, HCB and ΣHCH increased at most sites, ΣPCB and ΣDDT in Sweden and Norway. In the Oystercatcher, HCB and ΣHCH increased at more than the half of the sites, ΣPCB, ΣDDT and Hg at several German sites. In the terns, Hg, ΣPCB and ΣDDT exceeded the EcoQO in all, HCB in most years and sites. At most sites, ΣHCH fulfilled the EcoQO in some study years. In the Oystercatcher, Hg, ΣPCB and ΣDDT exceeded the EcoQO in all or most years and sites. HCB and ΣHCH fulfilled the EcoQO in some or all years at most sites. The EcoQO was exceeded most frequently in estuaries. We conclude that EcoQOs are suitable for drawing contamination patterns of the coastal North Sea in an easily understandable manner, offering the opportunity to harmonize the EcoQOs with coordinated environmental monitoring programmes.

To improve the statistical power of detecting changes in contaminant concentrations over time, it is critical to reduce both the within- and between-year variability by adjusting the data for relevant confounding variables. In this study, we present a method for handling multiple confounding variables in contaminant monitoring. We evaluate the highly variable temporal trends of Polycyclic Aromatic Hydrocarbons (PAHs) in blue mussels from the central Baltic Sea during the period 1987–2016 (data from 25 years during this period) using various regression analyses. As potential explanatory variables related to PAH exposure, we use mussel size and retrospective analyses of mussel δ15N and δ13C (representing large scale biogeochemical changes as a result of e.g. eutrophication and terrestrial inputs). Environmental data from concurrent monitoring programmes (seasonal data on Chlorophyll- a , salinity and temperature in the water column, bioturbation of sediment dwelling fauna) were included as variables related to feeding conditions. The concentrations of high-molecular-weight and low-molecular-weight PAHs in blue mussel were statistically linked to different combinations of environmental variables. Adjustment using these predictors decreased the coefficient of variation in all 15 PAHs tested and improved the statistical power to detect changes. Moreover, the adjustment also resulted in a significant downward trend for fluoranthene that could not be detected initially. For another PAH, benzo(g , h , i)perylene, adjustment which reduced variation resulted in the loss of an apparent downward trend over time. Hence, our study highlights the importance of using auxilliary data to reduce variability caused by environmental factors with general effects on physiology when assessing contaminant time trends. Furthermore, it illustrates the importance of extensive and well designed monitoring programmes to provide relevant data. Unlabelled Image • Long term biogeochemical/oceanographical data are linked to PAH burden in mussels. • A method for handling multiple confounding variables in contaminant monitoring • Adjustment for environmental data reduced coefficient of variation in mussel PAH. • Adjustment resulted in significant downward trends not detected in rawdata. • Extensive and well designed monitoring programs are critical to provide relevant data. [ABSTRACT FROM AUTHOR]