Polychlorinated Biphenyls in Food

Room-to-Room Variability of Airborne Polychlorinated Biphenyls in Schools and the Application of Air Sampling for Targeted Source Evaluation

Airborne polychlorinated biphenyl (PCB) concentrations are higher indoors than outdoors due to their historical use in building materials and their presence in modern paints and surface treatments. For some populations, including school children, PCB levels indoors result in inhalation exposures that may be greater than or equivalent to exposure through diet. In a school, PCB exposure may come from multiple sources. We hypothesized that there are both Aroclor and non-Aroclor sources within a single school and that PCB concentration and congener profiles differ among rooms within a single building. To evaluate this hypothesis and to identify potential localized sources, we measured airborne PCBs in nine rooms in a school. We found that schoolroom concentrations exceed outdoor air concentrations. Schoolroom concentrations and congener profiles also varied from one room to another. The concentrations were highest in the math room (35.75 ng m-3 ± 8.08) and lowest in the practice gym (1.54 ng m-3 ± 0.35). Rooms in the oldest wing of the building, originally constructed between 1920 and 1970, had the highest concentrations. The congener distribution patterns indicate historic use of Aroclor 1254 as well as modern sources of non-Aroclor congeners associated with paint pigments and surface coatings. Our findings suggest this noninvasive source identification method presents an opportunity for targeted source testing for more cost-effective prioritization of materials remediation in schools.

Characterization of the Metabolic Pathways of 4-Chlorobiphenyl (PCB3) in HepG2 Cells Using the Metabolite Profiles of Its Hydroxylated Metabolites

The characterization of the metabolism of lower chlorinated PCB, such as 4-chlorobiphenyl (PCB3), is challenging because of the complex metabolite mixtures formed in vitro and in vivo. We performed parallel metabolism studies with PCB3 and its hydroxylated metabolites to characterize the metabolism of PCB3 in HepG2 cells using nontarget high-resolution mass spectrometry (Nt-HRMS). Briefly, HepG2 cells were exposed for 24 h to 10 μM PCB3 or its seven hydroxylated metabolites in DMSO or DMSO alone. Six classes of metabolites were identified with Nt-HRMS in the culture medium exposed to PCB3, including monosubstituted metabolites at the 3'-, 4'-, 3-, and 4- (1,2-shift product) positions and disubstituted metabolites at the 3',4'-position. 3',4'-Di-OH-3 (4'-chloro-3,4-dihydroxybiphenyl), which can be oxidized to a reactive and toxic PCB3 quinone, was a central metabolite that was rapidly methylated. The resulting hydroxylated-methoxylated metabolites underwent further sulfation and, to a lesser extent, glucuronidation. Metabolomic analyses revealed an altered tryptophan metabolism in HepG2 cells following PCB3 exposure. Some PCB3 metabolites were associated with alterations of endogenous metabolic pathways, including amino acid metabolism, vitamin A (retinol) metabolism, and bile acid biosynthesis. In-depth studies are needed to investigate the toxicities of PCB3 metabolites, especially the 3',4'-di-OH-3 derivatives identified in this study.

A state-of-the-science review of polychlorinated biphenyl exposures at background levels: relative contributions of exposure routes

Exposure to polychlorinated biphenyls (PCBs) can occur through multiple routes and sources, including dietary intake, inhalation, dermal contact, and ingestion of dust and soils. Dietary exposure to PCBs is often considered the primary exposure route for the general population; however, recent studies suggest an increasing contribution from indoor inhalation exposure. Here, we aim to estimate the relative contribution of different PCB exposure pathways for the general population, as well as for select age groups. We conducted a targeted literature review of PCB concentrations in environmental media, including indoor and outdoor air, indoor dust, and soils, as well as of total dietary intake. Using the average concentrations from the studies identified, we estimated PCB exposure through different routes for the general population. In addition, we assessed exposure via environmental media for select age groups. We identified a total of 70 studies, 64 that provided background PCB concentrations for one or more of the environmental media of interest and 6 studies that provided estimates of dietary intake. Using estimates from studies conducted worldwide, for the general population, dietary intake of PCBs was the major exposure pathway. In general, our review identifies important limitations in the data available to assess population exposures, highlighting the need for more current and population-based estimates of PCB exposure, particularly for indoor air and dietary intake.

Accumulation characteristics and estimated dietary intakes of polychlorinated dibenzo-p-dioxins, polychlorinated dibenzofurans and polychlorinated biphenyls in plant-origin foodstuffs from Chinese markets

The levels and accumulation characteristics of polychlorinated dibenzo-p-dioxins and dibenzofurans (PCDD/Fs) and polychlorinated biphenyls (PCBs) were investigated in nine pools of representative plant-origin foodstuffs randomly collected from markets located in five regions of the Chinese mainland during 2018-2019. The collected foodstuffs consisted of cereals, beans, potatoes, leafy vegetables, root and stem vegetables, melon vegetables, legume vegetables, edible fungi, and mixed vegetable oil. In the fresh plant food pools, the concentrations of toxic equivalency (WHO-TEQ) were in the ranges of 0.9-14.5 pg/kg in upperbound (UB) scenario and 0.002-7.3 pg/kg in lowerbound (LB) scenario on a fresh weight basis; and TriCDFs and TeCBs were the predominant PCDD/F and PCB homologues, respectively. In the mixed vegetable oil, the WHO-TEQ concentrations were 129.4 pg/kg and 103.6 pg/kg on a lipid weight basis in UB and LB scenarios, respectively; and high-chlorinated PCDD/F and PCB homologues were much more abundant. The estimated plant food-borne dietary intakes of WHO-TEQ by a standard adult in the five surveyed regions were in the ranges of 3.39-4.20 and 1.57-2.13 pg WHO-TEQ/kg body weight/month in UB and LB scenarios, respectively. Among all surveyed regions, consumption of cereals and vegetable oil made up the primary contributions to the estimated dietary intakes of WHO-TEQ. TriCDFs accounted for 41.1-83.9% of the PCDD/Fs dietary intakes via consumption of plant foods, and TeCBs made up 61.2-73.0% of the PCBs dietary intakes via consumption of plant foods, suggesting that the potential toxic effects of TriCDFs and TeCBs on human health should be concerned.

Application of gas chromatography coupled to triple quadrupole mass spectrometry (GC-(APCI)MS/MS) in determination of PCBs (mono-to deca-) and PCDD/Fs in Chinese mitten crab food webs

Polychlorinated biphenyls (PCBs) and dibenzo-p-dioxins and furans (PCDD/Fs) are notorious persistent organic pollutants (POPs), which may bioaccumulate through food chain and play detrimental effects to organisms even at trace levels. Quantification of PCBs and PCDD/Fs in biotic samples is a great challenge. In the present study, gas chromatography coupled to triple quadrupole mass spectrometry with an atmospheric pressure chemical ionization source (GC-(APCI)MS/MS) was studied for the isotope-dilution analysis of PCBs (mono-to deca-) and PCDD/Fs in Chinese mitten crab food webs. High-resolution mass spectrometry (HRMS) was applied for comparison. Light PCBs are compared between the two instruments for the first time. After optimization of instrument parameters, the RSDs of relative response factors of calibration curves were between 3.4% and 15.5% for PCBs and 1.7%-7.9% for PCDD/Fs. The limits of detection were between 0.021 and 0.150 pg/mL for PCBs and 0.051-0.237 pg/mL for PCDD/Fs. PCB concentrations in crab food web samples detected by GC-(APCI)MS/MS were well correlated with those detected by HRGC/HRMS. A DiCB, 3,3'-dichlorobiphenyl (PCB11), was the dominant PCB congener in aquatic food webs. Other MoCB and DiCB congeners were also widely identified; hence, low-weight PCB congeners should arouse more concern in the future. GC-(APCI)MS/MS may become an alternative instrument satisfying the PCB and PCDD/F detection.