Combining Passive Sampling with Toxicological Characterization of Complex Mixtures of Pollutants from the Aquatic Environment

Direct sample introduction GC-MS/MS for quantification of organic chemicals in mammalian tissues and blood extracted with polymers without clean-up

Solvent extracts of mammalian tissues and blood contain a large amount of co-extracted matrix components, in particular lipids, which can adversely affect instrumental analysis. Clean-up typically degrades non-persistent chemicals. Alternatively, passive sampling with the polymer polydimethylsiloxane (PDMS) has been used for a comprehensive extraction from tissue without altering the mixture composition. Despite a smaller fraction of matrix being co-extracted by PDMS than by solvent extraction, direct analysis of PDMS extracts was only possible with direct sample introduction (DSI) GC-MS/MS, which prevented co-extracted matrix components entering the system. Limits of quantitation (LOQ) ranged from 4 to 20 pg μL⁻¹ ethyl acetate (PDMS extract) for pesticides and persistent organic pollutants (POPs). The group of organophosphorus flame retardants showed higher LOQs up to 107 pg μL⁻¹ due to sorption to active sites at the injection system. Intraday precision ranged between 1 and 10%, while the range of interday precision was between 1 and 18% depending on the analyte. The method was developed using pork liver, brain, and fat as well as blood and was then applied to analyze human post-mortem tissues where polychlorinated biphenyls (PCBs) as well as dichlorodiphenyltrichloroethane (DDT) and DDT metabolites were detected.

Ex situ determination of freely dissolved concentrations of hydrophobic organic chemicals in sediments and soils: basis for interpreting toxicity and assessing bioavailability, risks and remediation necessity

The freely dissolved concentration (C_free) of hydrophobic organic chemicals in sediments and soils is considered the driver behind chemical bioavailability and, ultimately, toxic effects in benthic organisms. Therefore, quantifying C_free, although challenging, is critical when assessing risks of contamination in field and spiked sediments and soils (e.g., when judging remediation necessity or interpreting results of toxicity assays performed for chemical safety assessments). Here, we provide a state-of-the-art passive sampling protocol for determining C_free in sediment and soil samples. It represents an international consensus procedure, developed during a recent interlaboratory comparison study. The protocol describes the selection and preconditioning of the passive sampling polymer, critical incubation system component dimensions, equilibration and equilibrium condition confirmation, quantitative sampler extraction, quality assurance/control issues and final calculations of C_free. The full procedure requires several weeks (depending on the sampler used) because of prolonged equilibration times. However, hands-on time, excluding chemical analysis, is approximately 3 d for a set of about 15 replicated samples.

Growth Stimulation Effects of Environmentally Realistic Contaminant Mixtures on a Marine Diatom

To estimate mixture effects caused by the high number of chemicals simultaneously present in the environment, methods for routine effect assessment of environmentally realistic contaminant mixtures are needed. We repeatedly exposed the marine diatom Phaeodactylum tricornutum to Speedisk^TM passive sampler extracts and observed statistically significant growth stimulation up to 6 and 7% for samples from inside and outside the harbor of Zeebrugge, respectively. These effects were found at summed contaminant concentrations (159-166 ng L^-1 ) that were within a 1.1- to 2.4-fold range of those observed in grab water samples taken during sampler deployment. These stimulatory effects were confirmed in 2 independent tests with extracts stored for <1 or 8 mo that had undergone limited sample handling, whereas no effects were observed for extracts that had been stored for 16 mo that had undergone repeated handling (notably repeated freezing and thawing) before biotest spiking. Targeted analysis by ultra-high performance liquid chromatography was performed to quantify 88 personal care products (n = 8), pesticides (n = 28), and pharmaceuticals (n = 52). Among these compounds, multivariate statistical analysis put forward the β-blocker atenolol as explaining most of the observed variation in mixture composition between the growth-stimulating and no effect-causing extracts. However, when tested individually over the entire concentration range present in the extracts, atenolol did not have any effect on P. tricornutum, suggesting that nontargeted substances in the extracts may have contributed to the observed stimulatory effects. Nevertheless, the present study shows that exposure to contaminant mixtures at environmentally realistic concentrations can lead to small but significant growth stimulation effects on the marine diatom P. tricornutum. Environ Toxicol Chem 2019;38:1313-1322. © 2019 SETAC.