A large number of articles/reports concerning levels and time trends of POPs in mothers’ milk from this monitoring program are summarized (with some new original data included) in a review article from the year 2000 ( Norén and Meironyte, 2000), which reports decreasing levels of “dioxins” over time. This is supported by Lignell et al. (2009), who report decreasing levels of POPs, including “dioxins”, in mothers’ milk from Sweden

during 1996–2006. Only a few time series with multiple year sampling of mothers’ milk exists, especially with samples from the last decade. In this study we re-analyze a set of samples from the original (composite) time trend study (Norén and Meironyte, 2000), to test comparability, as well as new samples from 1999 to 2011. This will help UMI-77 ic50 us answer if the decreasing concentrations of “dioxins” are leveling off, i.e. what is the trend for the first decade of the 21st millennia, and if it is possible to compare the established concentrations from previous studies directly. Hence, 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 analyses of

some of the older samples. Three major concerns were considered when choosing mothers’ milk samples; i) to ensure comparability between the new and the previous analyses of Swedish mothers’ milk; ii) to add samples taken in the past to fill gaps in the previous time trend and iii) to expand see more the aforementioned time trend study ending in 1997 (Norén and Meironyte, 2000) to obtain data ranging from 1972 to 2011. In total, 30 samples were analyzed and Terminal deoxynucleotidyl transferase eight of these were non-identical samples from a given year. The samples consisted of pooled mothers’ milk from multiple donors, all healthy native Swedish, but were not exclusively from primiparae. Further information concerning sample composition is presented in Table 1. The samples, 50 g each, were provided by the Swedish Environmental Specimen Bank, Department of Environmental Research and Monitoring, Swedish Museum of Natural

History. The samples were prepared in house before they were shipped, on dry ice, to Eurofins GfA Lab Service GmbH, Hamburg, Germany, for analysis according to the method described by Reis et al. (2007). In brief the method could be described as follows: 13C-labeled surrogate standards were added to the samples followed by liquid–liquid extraction and subsequent gravimetric lipid determination prior to multiple column clean-up, including carbon column purification. The purified extracts were analyzed by GC/HRMS. To test for significant log-linear trends for PCDDs, PCDFs and DL-PCBs, log-linear regression analysis was performed for the entire investigated time period and for the most recent 10 years using the yearly arithmetic mean values.