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A comprehensive review of available PCDD/F time trend data is presented. This focuses on industrialized countries, drawing heavily on those countries that have been actively involved in PCDD/F monitoring and research, notably Germany, the United States, Sweden, The Netherlands, and the U.K. Information on temporal trends comes from the analysis of dateable deposits (e.g., sediments), retrospective analysis of preserved or archived samples, and ongoing monitoring programs. The data on changes in air concentrations, deposition, sediments, soil, biota, food, and human tissues are reviewed. The evidence for natural input/formation of PCDD/Fs is also briefly reviewed and discussed. Human activity has dominated PCDD/F inputs to the environment this century. Conceptually, it is probably appropriate to consider a 'pulse' of PCDD/Fs arising from human activities entering the environment in the 1930/1940s, peaking in the 1960/1970s, and continuing to a lesser degree today. A series of measures introduced in the past, recently, and anticipated for the future have reduced emissions to the atmosphere of industrialized countries and are projected to continue to reduce emissions over the coming decade. Comprehensive monitoring programs are required to confirm the interpretation of past changes and projected future declines presented here.

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In this study we explored the use of butter as a sampling matrix to reflect the regional and global scale distribution of PCBs and selected organochlorine pesticides/metabolites in air. This was because persistent organic pollutants (POPs) concentrate in dairy fats, where concentrations are controlled by feed intake (primarily from pasture/silage), which is in turn primarily controlled by atmospheric deposition. Butter sigmaPCB concentrations varied by a factor of approximately 60 in 63 samples from 23 countries. They were highest in European and North American butter and lowest in southern hemisphere (Australian, New Zealand) samples, consistent with known patterns of historical global usage and estimated emissions. Concentrations in butter reflected differences in the propensity of PCB congeners to undergo long range atmospheric transport from global source regions to remote areas and the relatively even distribution of HCB in the global atmosphere. Concentrations of p,p'-DDT, p,p'-DDE, and HCH isomers all varied over many orders of magnitude in the butter samples, with highest levels in areas of current use (e.g. India and south/central America for DDT; India, China, and Spain for HCH). We conclude that butter is sensitive to local, regional, and global scale spatial and temporal atmospheric trends of many POPs and may therefore provide a useful sampling medium for monitoring purposes. However, to improve the quantitative information derived on air concentrations requires an awareness of climatic and livestock management factors which influence air-milk fat transfer processes.

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Summary 1. There are increasing demands to predict ecohydrological responses to future changes in catchments but such predictions will be inevitably uncertain because of natural variability and different sources of knowledge (epistemic) uncertainty. 2. Policy setting and decision‐making should therefore reflect these inherent uncertainties in both model predictions and potential consequences. 3. This is the focus of a U.K. Natural Environment Research Council knowledge exchange project called the Catchment Change Network (CCN). The aim is to bring academics and practitioners together to define Guidelines for Good Practice in incorporating risk and uncertainty into assessments of the impacts of change. 4. Here, we assess the development of such Guidelines in the context of having catchment models of everywhere.

Polybrominated diphenyl ether (PBDE) congeners are constituents of flame retardants, and there is growing concern regarding their persistence, bioaccumulation, and toxicity. We collected breast milk samples between late 2001 and early 2003 from 54 U.K.-resident mothers. Of these, 27 originated from southeast England (London), and the other 27 originated from northwest England (Lancaster). Analysis of milk-fat extracts by gas chromatography–mass spectrometry was performed to determine the levels of 15 PBDE congeners, 15 polychlorinated biphenyl (PCB) congeners, and other selected chlorinated compounds. PCB and organochlorine (OC) levels in southeast samples were consistently higher, and significant differences (p < 0.05) were observed. ∑PBDE levels ranged from 0.3 to 69 ng/g lipid (geometric mean, 6.6 ng/g), and PBDE-47 was the most abundant congener. ∑PCB levels ranged from 26 to 530 ng/g lipid (geometric mean, 150 ng/g) and were composed mainly of PCB-153 (26%), PCB-138 (20%), and PCB-180 (13%). OC levels for 1,1,1-trichloro-2,2-bis(p-chlorophenyl)ethane (p,p′-DDT) and its metabolites (∑DDX) ranged from 24 to 2,300 ng/g lipid (geometric mean, 160 ng/g); hexachlorobenzene ranged from nondetectable levels to 180 ng/g lipid (geometric mean, 17 ng/g); and ∑hexachlorocyclohexane levels ranged from 1.2 to 1,500 ng/g lipid (geometric mean, 16 ng/g). Using nuclear magnetic resonance–based metabonomics, samples (n = 7) containing the highest contaminant levels were compared with samples (n = 7) containing the lowest levels. Excellent separation along the first principal component implied that the chemical constituents of the two groups were significantly different. Although reasons for such differences remain obscure, lifestyle factors associated with a more heterogeneous London cohort could be responsible. Identifying primary routes of contaminant exposures and their biologic effects is of great importance.