Comparing electron ionization high-resolution and electron capture low-resolution mass spectrometric determination of polybrominated diphenyl ethers in plasma, serum and milk

Gas chromatography coupled to low-resolution mass spectrometry with electron capture negative ionization as detection mode (GC-LRMS (ECNI)) has been compared to gas chromatography coupled to high-resolution mass spectrometry using electron ionization as detection mode (GC-HRMS (EI)) for determination of polybrominated diphenyl ethers (PBDEs) in biological samples. Extracts of 5.0 g plasma, serum and milk samples were analyzed using both methods. The GC-LRMS (ECNI) and GC-HRMS (EI) systems were found to be equally well suited for determination of PBDEs in the biological samples, as well as in standard solutions, with respect to response, detection limits and repeatability at the pg-level. The estimated limits of detection (LOD) in milk extracts ranged from 0.3-0.6 pg PBDE/g milk and 0.4-0.7 pg PBDE/g milk, for the GC-LRMS (ECNI) and GC-HRMS (EI) systems, respectively. The method repeatability including sample preparation was in the range 4.7-8.4% and 0.6-10% relative standard deviation (RSD) for the GC-LRMS (ECNI) and GC-HRMS (EI) systems, respectively.     

Modelling the Choice Between Multiple-Use vs. Specialised Forest Management and its Impact on Forest Management Costs

Forests provide ecosystem services, including timber production. In some cases, private forest owners perform management actions in order to enhance the provision of such services, or they may be encouraged by public policies and payments. This paper focuses specifically on the decision to set forest land aside for biodiversity conservation, as part of the more general question of the efficiency of multiple-use vs. specialised management of forest lands. We propose an econometric analysis to identify factors in the set-aside choice and measure the impact of this decision on forest management costs. The results show that the set-aside choice depends on the landowners’ income and motivations related to forest amenities. The choice of specialised management, as reflected in the set-aside decision, has a significant and positive impact on the intensity of management in the remainder of the forest and on management costs. From a policy implications point of view, these results suggest that instruments such as forest certification, subsidies and reverse auctions for conservation will be most likely to attract the interest of those forest owners with personal motivations and forest properties that offer both benefit and cost advantages in opting for such specialised management strategies.

     

Determinants of brominated flame retardants in breast milk from a large scale Norwegian study

Brominated flame retardants (BFRs), particularly polybrominated diphenyl ethers (PBDEs), are widely present in human populations. In order to investigate human exposure pathways and associations with socioeconomic and lifestyle factors, 393 breast milk samples from mothers living in various regions throughout Norway were analyzed. Up to ten PBDE congeners were measured in all the samples, hexabromocyclododecane (HBCD) and BDE-209 in subsets of 310 and 46, respectively. The median concentrations of the sum of the seven most prominent PBDEs (BDE-28, 47, 99, 100, 153, 154 and 183), BDE-209 and HBCD were 2.1, 0.32 and 0.86 ng/g lipids, respectively. These concentrations are comparable to the levels generally observed in human populations in Europe. The frequency distributions were quite skewed with long tails towards higher concentrations. Maternal age, parity, education, having a cohabitant employed as electrician, and ventilation were factors significantly associated with some of the BFRs, although these factors only explained a small amount of the variability (R² 0.04–0.16). The mothers' diet was not found to influence the breast milk PBDE and HBCD levels. Our results show that sources other than the diet are important for the variability seen in breast milk BFR concentrations and that exposure from the indoor atmosphere should be emphasized in future studies.     

Characterisation of human exposure pathways to perfluorinated compounds--comparing exposure estimates with biomarkers of exposure

Commercially used per- and polyfluorinated compounds (PFCs) have been widely detected in humans, but the sources of human exposure are not fully characterized. The objectives of this study were to assess the relative importance of different exposure pathways of PFCs in a group of Norwegians and compare estimated intakes with internal doses obtained through biomonitoring. Individual PFC intakes from multiple exposure sources for a study group of 41 Norwegian women were estimated using measured PFC concentrations in indoor air and house dust as well as information from food frequency questionnaires and PFC concentrations in Norwegian food. Food was generally the major exposure source, representing 67-84% of the median total intake for PFOA and 88-99% for PFOS using different dust ingestion rates and biotransformation factors of 'precursor' compounds. However, on an individual basis, the indoor environment accounted for up to around 50% of the total intake for several women. Significant positive associations between concentrations of PFCs in house dust and the corresponding serum concentrations underline the importance of indoor environment as an exposure pathway for PFCs. For breast-fed infants, breast milk was calculated to be the single most important source to PFCs by far. The estimated intakes were confirmed by comparing serum concentrations of PFOA and PFOS calculated using PK models, with the corresponding concentrations measured in serum. Even though food in general is the major source of exposure for PFCs, the indoor environment may be an important contributor to human exposure. This study provides valuable knowledge for risk assessment of PFCs and control strategies.     

Comparison of GC and LC determinations of hexabromocyclododecane in biological samples - results from two interlaboratory comparison studies

In order to assess the quality and comparability of results from determinations of 1,2,5,6,9,10-hexabromocyclododecane (HBCD) in biological samples, two interlaboratory comparison studies have been organized. Up to 13 laboratories determined either the total HBCD concentration, or concentrations of alpha-, beta- and gamma-HBCD, or both in cod liver oil, herring filet, salmon filet, butter and chicken meat. The laboratories were able to determine total HBCD concentrations in the marine samples with satisfying quality (RSD <35%). However, the analysis of samples with low HBCD contamination (相似文献   

Modelling Gene Flow between Fields of White Clover with Honeybees as Pollen Vectors

The portion-dilution model is a parametric restatement of the conventional view of animal pollination; it predicts the level of pollinator-mediated gene dispersal. In this study, the model was applied to white clover (Trifolium repens) and its most frequent pollinator, the honeybee (Apis mellifera). One of the three parameters in the portion-dilution model is the mean number of flowers a pollinator visits in one foraging bout. An alternative method to estimate this parameter was developed that was not depending on pollinator hive-seeking behaviour. The new estimation method, based on nectar collection, seems to be a good alternative, when reliable observation on visiting behaviour of pollinators is not possible. The gene flow in white clover was modelled. Where fields were assumed to be well separated, and only a low fraction of bees travelled between fields, the gene flow was estimated to be 0.7%, but subjected to large uncertainty. In a worst case scenario with adjacent fields—one with a genetically modified (GM) T. repens cultivar and the other with a conventional T. repens cultivar—and where all arriving bees were expected to transfer GM pollen, the median gene flow was modelled to be 7% with an estimated 95% percentile of 70%. The results show that the European Union threshold limit of 0.9% GM admixture for food and feed will likely be exceeded at times and especially organic farmers that do not accept GM admixture and often have clover and clover–grass fields might face challenges with admixture of GM.