Crystal structure of δ-isobutoxypentabromo-cyclododecanes, kinetics and selectivity of their isomerization during thermal treatment of flame-proofed polystyrenes

Hexabromocyclododecanes (HBCDs) are persistent organic pollutants now ubiquitous in the environment. Technical HBCD mixtures and with it flame-proofed polystyrenes (FP-PS) also contain isobutoxypentabromocyclododecanes (iBPBCDs) as minor constituents, which are possibly released together with HBCDs. So far, eight diastereomeric pairs of enantiomers named as α-, β-, γ-, δ-, ?-, ξ-, η-, and θ-iBPBCDs with proportions of 10%, 5%, 2%, 21%, 11%, 11%, 12% and 28% were found in technical HBCD. Herein the crystal structure of racemic δ-iBPBCD, the second most prominent diastereomer, is presented and assigned to (1S)-1-isobutoxy-(2R,5R,6S,9S,10S)-2,5,6,9,10-pentabromocyclododecane and its enantiomer. During thermal treatment of FP-PS, e.g. the production of extruded polystyrenes (XPS), proportions of δ-iBPBCDs decrease and those of other stereoisomers increase. Evidence was found that δ-iBPBCDs isomerize stereo- and regioselectively to β-iBPBCDs. Based on structural and kinetic data, a transformation mechanism was proposed. Apparent first-order rate constants (k_iso) of 0.0019, 0.0050, and 0.012 min⁻¹ are found for the δ- to β-iBPBCD isomerization at 120, 130, and 140 °C, respectively, corresponding to half-lives of 360, 140, and 56 min. These transformations also occur during the production of XPS, which predominantly contain β-iBPBCDs, whereas δ-iBPBCDs dominate in materials experiencing lower thermal stress, e.g. expanded polystyrenes (EPS). The relative configurations of δ- and θ-iBPBCDs are TtCtCt, like the one of γ-HBCDs. γ-HBCDs are the kinetically and α-HBCDs with a TcCtCc configuration the thermodynamically favored products. In analogy, β-iBPBCDs are assumed to have a TcCtCc configuration like α-HBCDs because they are formed from δ-iBPBCDs under thermodynamic control. In conclusion, HBCD- and iBPBCD-patterns in flame-proofed polystyrenes vary substantially, reflecting the thermal stress these materials have experienced. When released to the environment, these patterns might further change, as observed for HBCDs.     

Revisiting old lessons from classic literature on persistent global pollutants: This article belongs to Ambio’s 50th Anniversary Collection. Theme: Environmental contaminants

Looking back 50 years at classic literature was a reminder of inspiring discoveries and clever theories that were formative to the field of environmental chemistry, but also of the irreparable costs that persistent global pollutants have had on ecosystems and human society. In my view, these three papers have greatly impacted contemporary science and influenced development of policies that have limited the spread of hazardous contaminants. At the same time, a sobering reality is that reversing decades of past pollution has proven impossible in our lifetime, and global trends are dire for both legacy and emerging contaminants. Lessons in these papers are clear to most environmental scientists, but I argue have not resulted in adequate investment in infrastructure or manpower to enable systematic unbiased searching for pollutants as proposed by Sören Jensen in 1972. Acknowledging that the costs of new global contaminants will be too high, we must incentivize safer chemicals and their sustainable use, increase international exchange of lists of chemicals in commerce, and coordinate international efforts in nontarget screening to identify new contaminants before they circulate the world.     

城市内湖表层沉积物中有机氯农药残留特征及风险评价

中国曾大量生产和使用有机氯农药(OCPs),目前虽已被禁止生产和农业中使用,但含三氯杀螨醇的林丹和滴滴涕(DDTs)仍在非法生产和使用。为了解农业大省江西省城市内湖OCPs的残留情况,以鄱阳湖生态经济区象湖为研究对象,用GC/ECD 分析象湖表层沉积物中8 种OCPs的残留水平,采用ArcGIS空间分析、主成分分析法探讨OCPs 的残留特征、来源及其可能的风险。结果表明,8 种OCPs 在象湖表层沉积物中均有不同程度检出,六六六( ∑ HCHs) 含量为nd~61.89 ng/g, ∑ DDTs含量为nd~81.47 ng/g。含量较高的组分为o,p'-DDT、β-HCH和δ-HCH。象湖表层沉积物中OCPs残留空间分布不均,其中象湖南边湿地花卉公园沉积物中OCPs含量相对较高。同中国其他城市内湖/内河相比,象湖表层沉积物中HCHs和DDTs残留水平偏高,这可能与象湖区域曾经作为南昌市农业发展区有关。来源解析结果表明象湖HCHs和DDTs主要来源于农药的历史使用,但近年来很可能有林丹和三氯杀螨醇的输入。风险评价结果显示目前象湖表层沉积物中DDTs类污染物对人体健康风险总体处于较低水平,但湿地花卉公园周边环境生态风险较高,对周围环境的生物毒性较大。研究结果可为城市内湖的污染控制及风险管理提供科学依据。     

Soil burdens of persistent organic pollutants - Their levels, fate and risk. Part II. Are there any trends in PCDD/F levels in mountain soils?

Good quality data apt for an assessment of temporal trends of polychlorinated dibenzo-p-dioxins and furans (PCDDs/Fs) in soils are difficult to obtain since there is a general lack of information on their residues in soils. Variability of soil profiles, non-homogeneity of samples, and often also inconsistency of applied sampling procedures further complicate this problem. To assess spatial and temporal trends of contamination, three soil sampling campaigns have been performed over the period of 12 years at the mountain forest sites in the Czech Republic. Relation between the air, needle and soil contaminations was addressed in addition to time-related variability of soil. It has been confirmed that soil is a good matrix for evaluation of spatial distribution of persistent organic pollutants (POPs) but difficult for establishment of temporal trends. A slow rate of the soil-forming processes and their site-specificity was generally the major source of uncertainties.     

Characterization of bacterial communities during persistent fog and haze events in the Qingdao coastal region

• Light haze had little effect on bacterial communities. • Fog and heavy haze had significant effects on these communities. • Air pollution exerted a greater influence than particle size on bacterial community. Here, we report the characteristics of bacterial communities in aerosols with different particle sizes during two persistent fog and haze events in December of 2015 and 2016 in Qingdao, China. In the early stage of pollution, the accumulation of PM_2.5 led to the accumulation of microorganisms, thus increasing the bacterial richness and diversity of fine particle sizes. With the persistence and aggravation of pollution, the toxic effect was strengthened, and the bacterial richness and diversity of each particle size decreased. When the particle concentration was highest, the richness and diversity were low for each particle size. Light haze had little influence on bacterial communities. The occurrence of highly polluted humid weather and heavy haze resulted in significant changes in bacterial community diversity, composition and structure, and air pollution exerted a greater influence than particle size on bacterial community structure. During persistent fog and haze events, with the increase of pollutants, bacteria associated with each particle size may be extensively involved in aerosol chemistry, but the degree of participation varies, which requires further study.     

Changes over time in persistent organic pollutants (POP) concentrations in human milk in the Republic of Moldova

Persistent organic pollutants (POP) in human milk originating from various sources are used as environmental exposure markers. Further, mothersmilk is a predominant pathway for human exposure for suckling infants to POP. The aim of present study was to provide baseline and time trend information on human milk POP concentrations in the Republic of Moldova. A pooled sample of breast milk was analyzed in 2009 and 2015 and health risk evaluated by comparing reference values of humans' daily intake with estimated daily intake (EDI). Results showed decreases for concentrations of dichlorodiphenyltrichloroethane, hexachlorobenzene, dieldrin, heptachlor, α and β-hexachlorocyclohexane, polychlorinated biphenyls, dioxin-like polychlorinated biphenyls, polychlorinated dibenzo-p-dioxins and dibenzofurans between sampling periods. Regardless of the decrease, EDI was higher than reference values for dioxins toxic equivalents, polychlorinated biphenyls and β-hexachlorocyclohexane in both phases. However, increased levels were detected for polybrominated diphenyl ethers (twofold) and hexabromocyclododecane (threefold) from 2009 to 2015, but the EDI in both phases is much lower than the reference. The decline in certain POP levels may be attributed to coordinated efforts undertaken by national and international entities to regulate these compounds. The basis for the elevated levels of polybrominated diphenyl ethers and hexabromocyclododecane remains unknown but raises concerns regarding lactational exposure.     

A rapid method for screening of the Stockholm Convention POPs in small amounts of human plasma using SPE and HRGC/HRMS

A rapid analytical screening method allowing simultaneous analysis of 23 persistent organic pollutants (POPs) in human plasma was developed. Sample preparation based on solid-phase extraction (SPE) with additional clean-up using small multilayer silica gel columns. SPE was performed using a custom made polystyrene-divinylbenzene sorbent for the extraction of chlorinated and brominated POPs. Special efforts to reduce sample volume and improve speed and efficiency of the analytical procedure were made. Determination of 16 polychlorinated biphenyls (PCBs), 5 organochlorine (OC) pesticides, octachlorinated dibenzo-p-dioxin (OCDD) and polybrominated diphenyl ether (BDE #47) in 0.5 mL human plasma was performed by using high resolution gas chromatography coupled to high resolution mass spectrometry (HRGC/HRMS). Recovery of POPs ranged between 46% and 110%, and reproducibility was below 25% relative standard deviation (RSD) for all target compounds, except for trans-nonachlor and OCDD, which were present only at low levels. Limits of detection (LOD) were for the PCBs between 0.8 and 117.7 pg mL⁻¹ plasma and for the OC pesticides between 5.9 and 89.1 pg mL⁻¹ plasma. The LOD for OCDD and BDE #47 were 1.4 pg mL⁻¹ plasma, and 9.2 pg mL⁻¹ plasma, respectively. The presented method was successfully applied to 1016 human plasma samples from an epidemiological study on cardiovascular disease.     

Environmental factors affecting thyroid function of wild sea bass (Dicentrarchuslabrax) from European coasts

Thyroid functional status of wild fish in relation with the contamination of their environment deserves further investigation. We here applied a multi-level approach of thyroid function assessment in 87 wild sea bass collected near several estuaries: namely the Scheldt, the Seine, the Loire, the Charente and the Gironde. Thyroxine (T₄) and triiodothyronine (T₃) concentrations in muscle were analyzed by radioimmunoassay. The activity of hepatic enzymes involved in extrathyroidal pathways of thyroid hormone metabolism, viz. deiodination, glucuronidation and sulfatation were analyzed. Last, follicle diameter and epithelial cell heights were measured. We observed changes that are predicted to lead to an increased conversion of T₄-T₃ and lowered thyroid hormone excretion. The changes in the metabolic pathways of thyroid hormones can be interpreted as a pathway to maintain thyroid hormone homeostasis. From all compounds tested, the higher chlorinated PCBs seemed to be the most implicated in this perturbation.     

Effects of amendments on the uptake and distribution of DDT in Cucurbita pepo ssp pepo plants

The effects of soil amendments on the phytoextraction of ∑DDT (DDT + DDD + DDE) from soil ([∑DDT] ∼ 1500 ng/g) by a pumpkin variety of Cucurbita pepo ssp pepo were tested and the patterns of ∑DDT storage throughout the plant shoot were examined. The soil amendments did not increase the total amount of ∑DDT extracted into plant shoots, but new information about ∑DDT distribution in the plants was obtained. As observed previously, the ∑DDT concentration in plant leaves (mean 290 ng/g) was significantly lower than in plant stems (mean 2600 ng/g). Further analysis revealed that ∑DDT composition was consistent throughout the plant shoot and that ∑DDT concentration in leaves and stems decreased exponentially as distance from the root increased, which was previously unknown. This new information about the patterns of ∑DDT uptake and translocation within pumpkin plants highlights the need for appropriate plant sampling strategies in future POPs phytoextraction research.     

Partitioning of organochlorine pesticides from water to polyethylene passive samplers

The mass transfer rates and equilibrium partitioning behaviour of 14 diverse organochlorine pesticides (OCP) between water and polyethylene (PE) passive samplers, cut from custom made PE sheets and commercial polyethylene plastic bags, were quantified. Overall mass transfer coefficients, k_O, estimated PE membrane diffusion coefficients, D_PE, and PE-water partitioning coefficients, K_PE-water, are reported. In addition, the partitioning of three polycyclic aromatic hydrocarbons (PAHs) from water to PE is quantified and compared with literature values. K_PE-water values agreed mostly within a factor of two for both passive samplers and also with literature values for the reference PAHs. As PE is expected to exhibit similar sorption behaviour to long-chain alkanes, PE-water partitioning coefficients were compared to hexadecane-water partitioning coefficients estimated with the SPARC online calculator, COSMOtherm and a polyparameter linear free energy relationship based on the Abraham approach. The best correlation for all compounds tested was with COSMOtherm estimated hexadecane-water partitioning coefficients.