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Dioxin analysis in food and feed can be characterized as an analytical application where very high accuracy is required at very low levels of contamination. Gas chromatography (GC) in combination with 13C-label isotope dilution (ID) high resolution mass spectrometry (HRMS) is the reference congener-specific technique characterized by pronounced selectivity, precision and trueness at parts-per-trillion (ppt) and sub-parts-per-trillion (sub-ppt) levels. The quality of the analytical data produced routinely by a laboratory should be adequate for its intended purpose, i.e., one will seek a compromise between the cost and time needed and the consequences of incorrect decisions due to erroneous results. The requirements for reproducibility are usually dependent on the analyte concentrations and have been expressed in various empirical functions. While Horwitz or modified functions are widely useful for many purposes, it would be difficult to expect these functions to cover every analytical problem. This study reports on precision characteristics achieved by the GC-ID-HRMS reference method for polychlorinated dibenzo-p-dioxins (PCDDs), polychlorinated dibenzofurans (PCDFs) and dioxin-like polychlorinated biphenyls (DL-PCBs) in food and feed in two interlaboratory method-performance studies among expert laboratories with long-standing experience in this field. Striking linear functions in log scale between reproducibility standard deviation and congener’s level over a concentration range of 10−8–10−14 g per g fresh weight are observed. The data fit very well to a Horwitz-type function of the form s R =0.153c 0.904, where s R and c are dimensionless mass ratios expressed in pgg−1 on fresh weight, regardless of the nature of the toxic congeners, food and feed matrices, or sample preparation methods. We demonstrate that the proposed function is suitable for use as a fitness-for-purpose criterion for proficiency assessment in interlaboratory comparisons on dioxins and related compounds in food. [Copyright &y& Elsevier]

[Display omitted] • A wide range of pre- and postnatal environmental exposures affects child behavior. • The exposome includes outdoor, indoor, chemical, lifestyle and social exposures. • Maternal tobacco smoke and car traffic increased behavioural problems in children. • Child sleep, healthy diet and higher family social capital reduced symptoms. • Child exposure to lead, copper, indoor air pollution, increased symptoms. Environmental exposures in early life influence the development of behavioral outcomes in children, but research has not considered multiple exposures. We therefore aimed to investigate the impact of a broad spectrum of pre- and postnatal environmental exposures on child behavior. We used data from the HELIX (Human Early Life Exposome) project, which was based on six longitudinal population-based birth cohorts in Europe. At 6–11 years, children underwent a follow-up to characterize their exposures and assess behavioral problems. We measured 88 prenatal and 123 childhood environmental factors, including outdoor, indoor, chemical, lifestyle and social exposures. Parent-reported behavioral problems included (1) internalizing, (2) externalizing scores, using the child behavior checklist (CBCL), and (3) the Conner's Attention Deficit Hyperactivity Disorder (ADHD) index, all outcomes being discrete raw counts. We applied LASSO penalized negative binomial regression models to identify which exposures were associated with the outcomes, while adjusting for co-exposures. In the 1287 children (mean age 8.0 years), 7.3% had a neuropsychiatric medical diagnosis according to parent's reports. During pregnancy, smoking and car traffic showing the strongest associations (e.g. smoking with ADHD index, aMR:1.31 [1.09; 1.59]) among the 13 exposures selected by LASSO, for at least one of the outcomes. During childhood, longer sleep duration, healthy diet and higher family social capital were associated with reduced scores whereas higher exposure to lead, copper, indoor air pollution, unhealthy diet were associated with increased scores. Unexpected decreases in behavioral scores were found with polychlorinated biphenyls (PCBs) and organophosphate (OP) pesticides. Our systematic exposome approach identified several environmental contaminants and healthy lifestyle habits that may influence behavioral problems in children. Modifying environmental exposures early in life may limit lifetime mental health risk. [ABSTRACT FROM AUTHOR]