Plastiome: Plastisphere-enriched mobile resistome in aquatic environments.

Aquatic microplastics (MPs) act as reservoirs for microbial communities, fostering the formation of a mobile resistome encompassing diverse antibiotic (ARGs) and biocide/metal resistance genes (BMRGs), and mobile genetic elements (MGEs). This collective genetic repertoire, referred to as the "plastiome," can potentially perpetuate environmental antimicrobial resistance (AMR). Our study examining two Japanese rivers near Tokyo revealed that waterborne MPs are primarily composed of polyethylene and polypropylene fibers and sheets of diverse origin. Clinically important genera like Exiguobacterium and Eubacterium were notably enriched on MPs. Metagenomic analysis uncovered a 3.46-fold higher enrichment of ARGs on MPs than those in water, with multidrug resistance genes (MDRGs) and BMRGs prevailing, particularly within MPs. Specific ARG and BMRG subtypes linked to resistance to vancomycin, beta-lactams, biocides, arsenic, and mercury showed selective enrichment on MPs. Network analysis revealed intense associations between host genera with ARGs, BMRGs, and MGEs on MPs, emphasizing their role in coselection. In contrast, river water exhibited weaker associations. This study underscores the complex interactions shaping the mobile plastiome in aquatic environments and emphasizes the global imperative for research to comprehend and effectively control AMR within the One Health framework.

Hazardous implications of halogenated polycyclic aromatic hydrocarbons in feedstuff: Congener specificity and toxic levels in feed ingredients and feeds.

Studies have shown that halogenated polycyclic aromatic hydrocarbons (HPAHs), including chlorinated (ClPAHs) and brominated PAHs (BrPAHs), could be hazardous pollutants due to their pervasive occurrence in the environment. However, their accumulation properties and toxic potentials in animal feedstuffs remain unclear. This study investigated 75 congeners of parent PAHs, ClPAHs, and BrPAHs in animal-based feed ingredients and fish and swine feeds in Japan using a GC/Orbitrap MS system. The total parent PAHs ranged from below the method detection limit (

Voyaging of halogenated polycyclic aromatic hydrocarbons, an emerging group of pollutants, on micro-mesoplastics in the marine environment.

The limited existing research on the accumulation of hazardous chlorinated and brominated polycyclic aromatic hydrocarbons (ClPAHs and BrPAHs) in micro-mesoplastics (mMPs) motivated this investigation. We collected mMPs from the coastal environments of Sri Lanka and Japan. Out of 75 target compounds analyzed, 61 were detected, with total parent PAH concentrations reaching 16,300 and 1770 ng/g plastic in Sri Lanka and Japan, respectively. The total parent PAH concentrations in mMPs from the southern Sri Lankan coastline were relatively higher than those from the eastern coastline. Phenanthrene and naphthalene were the dominant parent PAH congeners in most mMP samples. Chlorinated pyrenes and brominated naphthalene were predominant among halogenated PAHs. The estimated toxic equivalency quotient (TEQ) ranged from 0.67 to 1057 ng-TEQ/g plastic, with the highest levels observed in polystyrene (PS) particles from the southern Sri Lankan coast. Benzo[a]pyrene and dibenzo[a,h]anthracene exhibited elevated TEQ for parent PAHs, whereas dichloropyrene, and dibromopyrene represented the highest TEQs for ClPAHs and BrPAHs, respectively. The data evidenced that several HPAH congeners can increase the PAH-like toxicity (∼86%) in mMPs. This study provides insights into the accumulation of parent and halogenated PAHs in mMPs, highlighting their potential combined implications in marine and terrestrial ecosystems.

Characteristics of antimicrobial residues in manure composts from swine farms: Residual patterns, removal efficiencies, and relation to purchased quantities and composting methods in Japan.

Present study provides first comprehensive results on the residual levels of 19 antimicrobial (AM) residues in 12 Japanese swine manure composting facilities that use open or enclosed types of treatment methods. Tilmicosin (14000 µg/kg d.w.) and tiamulin (15000 µg/kg d.w.) were present in the highest concentrations in manure composts. Morantel (MRT) had the highest detection frequency (100%) in compost, suggesting its ubiquitous usage and resistance to degradation during composting. Sulfamethoxazole had low detection frequencies and concentrations, likely due to limited partitioning to the solid phase. A positive correlation (p < 0.05) between purchasing quantities and residue levels in manure composts was detected for fluoroquinolones (FQs). The removal efficiencies of AMs in enclosed-type facilities were lower and more inconsistent than those in open-type facilities. Tetracyclines (TCs), lincomycin, and trimethoprim were easily removed from open-type facilities, whereas FQs and MRT persisted in both facilities. After discontinuing the usage of oxytetracycline (OTC), TCs concentrations reduced drastically in input materials, remained pseudo-persistent in composts for up to 4 months, suggesting a time lag for composting and were not detected (<10 µg/kg) after 4 months of OTC withdrawal. This study emphasizes on the effectiveness of manure composting methods in reducing AM residues in swine waste.

Occurrence and the potential ecological risk of veterinary antimicrobials in swine farm wastewaters in Japan: Seasonal changes, relation to purchased quantity and after termination of oxytetracycline usage.

This study provides the first comprehensive investigation of the residual concentrations of eight classes of antimicrobial agents (AMs, 20 compounds) in 13 swine wastewater treatment facilities in Japan. These facilities implemented the aerobic activated sludge (AS) or its alternative methods. The maximum concentrations before treatment were found at the level of 7100, 6900, 6000, 3600, 3400, and 1400 µg/L for tilmicosin, oxytetracycline (OTC), chlortetracycline, lincomycin , sulfamethoxazole, and trimethoprim, respectively. The highest detection rate (96.3%) in influents was noted for the morantel, which was a feed additive. The seasonal difference in residual concentration was much greater for tetracyclines (TCs) and macrolides (MLs) when their residual concentrations were high, especially in the cold season. There was a positive correlation between the purchased quantity of TCs and fluoroquinolones (FQs) and their residue levels detected in the effluents (p < 0.01). The estimated removal rate of AMs was greater than 80%. In contrast, on a few occasions, it was diminished due to failing operating conditions, such as water temperature and AS rate in the aeration tank. The estimated ecological risks of AMs in effluents based on risk quotients (RQs) considered to enhance the selection pressure for drug resistance (RQs-AMR) were high for TCs and FQs, whereas ecotoxicological effects (RQs-ENV) to aquatic organisms were higher for sulfonamides and MLs. When OTC usage ceased, its concentration in wastewater decreased rapidly; however, it remained longer period in the effluents, probably due to OTC desorption from the AS. The concentrations (and respective RQs) of TCs were decreased by >99.8% and >92% in the influents and effluents, respectively. This data suggested that it is essential to reduce the amount used and introduce more efficient methods and operating conditions to constantly remove AMs during the treatment to reduce the risk of AM discharge from swine farms.

Pilot-scale incineration of wastes with high content of chlorinated and non-halogenated organophosphorus flame retardants used as alternatives for PBDEs.

Chlorinated and non-halogenated organophosphorus flame retardants (OPFRs) including tris(2-chloroisopropyl) phosphate (TCIPP), diethylene glycol bis(di(2-chloroisopropyl) phosphate) (DEG-BDCIPP), triphenyl phosphate (TPHP), and bisphenol A bis(diphenyl phosphate) (BPA-BDPP) have been used increasingly as alternatives to polybrominated diphenyl ethers and other brominated flame retardants. For this study, five batches of incineration experiments of wastes containing approximately 1% of TCIPP, DEG-BDCIPP, TPHP, and BPA-BDPP were conducted using a pilot-scale incinerator. Destruction and emission behaviors of OPFRs were investigated along with the effects on behaviors of unintentional persistent organic pollutants (POPs) such as polychlorinated dibenzo-p-dioxins (PCDDs), polychlorinated dibenzofurans (PCDFs), dioxin-like polychlorinated biphenyls (dl-PCBs), hexachlorobenzene (HCB), pentachlorobenzene (PeCB), and pentachlorophenol (PCP). Incineration conditions were chosen according to current regulations for waste incinerators in Japan and UNEP. The OPFRs in the input materials were mainly destroyed in the primary combustion with destruction efficiencies greater than 99.999%. Concentrations of the OPFRs in the exhaust gases and ash were, respectively, <0.01-0.048 µg m(-3) and <0.5-68 µg kg(-1). Almost all of the total phosphorus in the input materials was partitioned into the ash, but less into final exit gases, indicating negligible emissions of volatile phosphorus compounds during incineration. Inputs of chlorinated OPFRs did not affect the formation markedly. Destruction and emission behaviors of unintentional POPs were investigated. Emissions of such POPs in exhaust gases and the ash were lower than the Japanese and international standards. Results show that even in wastes with high contents of chlorinated and non-halogenated OPFRs, waste incineration by the current regulations for the waste incinerators can control environmental emissions of OPFRs and unintentional POPs. Incineration is regarded as a best available technology (BAT) for waste management systems.

Destruction behavior of hexabromocyclododecanes during incineration of solid waste containing expanded and extruded polystyrene insulation foams.

Hexabromocyclododecanes (HBCDs) have been used for flame retardation mainly in expanded polystyrene (EPS) and extruded polystyrene (XPS) insulation foams. Controlled incineration experiments with solid wastes containing each of EPS and XPS were conducted using a pilot-scale incinerator to investigate the destruction behavior of HBCDs and their influence on the formation of polybrominated dibenzo-p-dioxins and dibenzofurans (PBDD/DFs). EPS and XPS materials were respectively blended with refuse derived fuel (RDF) as input wastes for incineration. Concentrations of HBCDs contained in the EPS- and XPS-added RDFs, were 140 and 1100 mg kg(-1), respectively. In which γ-HBCD was dominant (68% of the total HBCD content) in EPS-added RDF and α-HBCD accounted for 73% of the total HBCDs in XPS-added RDF. During the incineration experiments with EPS and XPS, primary and secondary combustion zones were maintained at temperatures of 840 °C and 900 °C. The residence times of waste in the primary combustion zone and flue gas in the secondary combustion zone was 30 min and three seconds, respectively. HBCDs were steadily degraded in the combustion chambers and α-, ß-, and γ-HBCD behaved similarly. Concentration levels of the total HBCDs in the bag filter exit gas for the two experiments with EPS and XPS were 0.7 and 0.6ngmN(-3), respectively. HBCDs were also not detected (<0.2 ng g(-1)) in the bottom and fly ash samples. From the obtained results, it was calculated that HBCDs were sufficiently destroyed in the whole incineration process with destruction efficiencies of more than 99.9999 for both of EPS and XPS cases. For PBDD/DFs, the levels detected in the bottom and fly ash samples were very low (0.028 ng g(-1) at maximum). In the case of XPS-added experiment, 2,3,7,8-TeBDD and 2,3,7,8-TeBDF were determined in the flue gas at levels (0.05-0.07 ng mN(-3)) slightly over the detection limits in the environmental emission gas samples, suggesting HBCDs in XPS are possibly a precursor of detected PBDD/DFs. Operational care should be taken when the ratio of HBCD-containing polystyrene is increased in the input wastes just to make sure of formation prevention and emission control of PBDD/DFs. The concentrations and congener patterns of PCDD/DFs and dl-PCBs in the samples during the three experiments were not affected by an addition of HBCDs.

Detection of benzotriazole UV stabilizers in the blubber of marine mammals by gas chromatography-high resolution mass spectrometry (GC-HRMS).

Benzotriazole UV stabilizers (BUVSs), such as UV-328 and UV-327, were identified in the blubbers of finless porpoises (Neophocaena phocaenoides) collected from the Ariake Sea, western Japan, by gas chromatography-high resolution mass spectrometry (GC-HRMS). The mean concentrations and standard deviations of UV-328 and UV-327 in five blubber samples were 38 ± 28 ng g(-1) (lipid wt) and 19 ± 19 ng g(-1), respectively. The bioconcentration factor (BCF) of UV-327 between water and finless porpoises was estimated to be 33 300, which is approximately one order of magnitude higher than that found for small fish inhabiting the same regions. The BCF of UV-327 in finless porpoises was similar to that of persistent organochlorine pesticide, hexachlorocyclohexane (HCH: 37 000) in marine mammals from the western North Pacific Ocean. These results suggest that BUVSs appear to be persistent and bioaccumulative in the aquatic food chain. Further investigations on temporal trends, and regional and global monitoring of BUVSs are needed to understand their environmental profiles and potential risks to wildlife and human.

Hepatic CYP1A induction by chlorinated dioxins and related compounds in the endangered black-footed albatross from the North Pacific.

The present study assesses effects of dioxins and related compounds (DRCs) including polychlorinated dibenzo-p-dioxins, polychlorinated dibenzofurans, and dioxin-like polychlorinated biphenyls (DL-PCBs) on cytochrome P450 1A (CYP1A) expression level in liver of black-footed albatrosses (Phoebastria nigripes) collected from the North Pacific. Total 2,3,7,8-tetrachlorodibenzo-p-dioxin (2,3,7,8-T(4)CDD) toxic equivalents (TEQs) derived from toxic equivalency factor for birds proposed by World Health Organization were in the range of 2100 to 10 000 pg/g lipid wt (120-570 pg/g wet wt). Simultaneously, microsomal alkoxyresorufin O-dealkylase (AROD) activities, including methoxy-, ethoxy-, pentoxy-, and benzyloxy-resorufin O-dealkylase activities were also measured in the same specimens. Total TEQs and TEQ (on wet wt basis) from some individual DRC congeners had significant positive correlations with AROD activities, suggesting induction of CYP1A by DRCs. Congeners like 2,3,7,8-T(4)CDD and most of the DL-PCBs that showed no significant positive correlations between the concentrations and AROD activities, exhibited significant negative correlations between AROD activities and the concentration ratio of the congener to a recalcitrant CB169, suggesting preferential metabolism of these congeners by induced CYP1A. As far as we know, this is the first direct evidence revealing that hepatic CYP1A level is elevated with the accumulation of DRCs in the wild black-footed albatross population. The present study gives more robust estimate of impacts of DRCs on CYP1A induction in this rare pelagic species than indexes like hazard quotient and TEQ-threshold comparison that have been so far carried out.

Behavior of polychlorinated benzenes, PCDD/Fs and dioxin-like PCBs during incineration of solid waste contaminated with mg/kg levels of hexachlorobenzene.

Hexachlorobenzene (HCB), one of the well-known Persistent Organic Pollutants (POPs), is present in some pigments and these raw materials with maximum level of several thousand of mg/kg. Considering that these pigments have been used in long-life products, such as car parts, construction materials and electrical and electronic equipments, the articles containing HCB at a concentration of several hundred mg/kg still have to undergo waste management. In this study, we performed a combustion experiment involving solid waste containing 300 mg/kg of HCB as the input material using a pilot-scale incinerator to determine the destruction of HCB and its influence on the behavior of other polychlorinated benzenes (CBzs) and unintentionally produced POPs, such as polychlorinated dibenzo-p-dioxins and dibenzofurans (PCDD/Fs) and dioxin-like polychlorinated biphenyls (dl-PCBs). HCB at a concentration of 300 mg/kg in the input material was destroyed mainly in the primary combustion zone. Overall the destruction efficiency of HCB was > 99.9985%. The input concentration of HCB did not significantly affect the formation and destruction or the final emissions of other CBzs, PCDD/Fs and dl-PCBs. These results indicate that incineration, when operated and structured to minimize emissions of dioxin-related compounds, is considered to be one of the Best Available Technologies for the appropriate treatment of waste containing HCB with a concentration in the order of mg/kg.

Behavior of 2-(3,5-di-tert-butyl-2-hydroxyphenyl)benzotriazole (DBHPBT) and 2-(3,5-di-tert-butyl-2-hydroxyphenyl)-5-chlorobenzotriazole during incineration of solid waste contaminated with thousand mg/kg levels of DBHPBT.

2-(3,5-Di-tert-butyl-2-hydroxyphenyl)benzotriazole (DBHPBT) is classified as a "Class I Specified Chemical Substance" by the Chemical Substance Control Law, Japan, meaning that DBHPBT has comparable nature and toxicity to well-known Persistent Organic Pollutants (POPs). In this study, we performed a combustion experiment of solid waste containing DBHPBT using a pilot-scale incinerator to determine the destruction behavior of DBHPBT and the effects on emission of 2-(3,5-di-tert-butyl-2-hydroxyphenyl)-5-chlorobenzotriazole (DBHPCBT), which is structurally similar to DBHPBT and has a persistent nature, and nitrogen oxides (NOx). DBHPBT was destroyed mainly in the primary combustion zone. Overall destruction efficiency of DBHPBT in input at the concentration of 5000 mg/kg was >99.9999%. The input amount of DBHPBT did not affect the formation and destruction behavior of DBHPCBT and NOx. These results indicate that appropriate management of combustion conditions and flue gas treatment can minimize the emission of DBHPBT.

Influence of combustion temperature on formation of nitro-PAHs and decomposition and removal behaviors in pilot-scale waste incinerator.

To gain a better understanding of the formation and decomposition behaviors of nitro-polycyclic aromatic hydrocarbons (nitro-PAHs) in solid waste combustion, incineration experiments were conducted using a pilot-scale incinerator. Nitro-PAHs were formed during primary combustion, although the amounts formed were several orders of magnitude lower than those of the PAHs, PCDD/Fs, and the dioxin-like PCBs. Increasing the temperature of primary combustion from 690 to 890 degrees C resulted in a significant decrease in the formation of most of the nitro-PAH compounds studied. More than 99% of nitro-PAHs formed in the primary combustion zone were decomposed in the secondary combustion chamber at 900 degrees C with a 3-s residence time. The results indicate that appropriate secondary combustion conditions are the key to controlling emissions of nitro-PAHs. Under optimized conditions, the amounts of nitro-PAHs in the final off gases and in the ashes were significantly lower than those present in the incinerator input. Overall destruction efficiencies of nitro-PAHs reported in this study were 95.81-98.33%, indicating that emission of nitro-PAHs from solid waste combustion can be minimized by appropriate combustion control.

Identification of brominated and chlorinated phenols as potential thyroid-disrupting compounds in indoor dusts.

Our previous study demonstrated that compounds in indoor dusts strongly inhibit thyroxine (T4) binding to the human thyroid hormone transport protein transthyretin (TTR) in vitro. Exposure assessment indicated that house dust is an important medium of exposure of children to TTR-binding compounds when binding potency and dust ingestion rates are high. Here, we used chemical fractionation with in vitro competitive human TTR-binding assay and GC-MS to analyze the TTR-binding compounds in a sulfuric-acid-treated dust extract. 2,4,6-Tribromophenol (TriBPh) and 2,3,4,5,6-pentachlorophenol (PeCPh) were potent TTR-binding compounds in all dust samples. 2,4,6-TriBPh- and 2,3,4,5,6-PeCPh-derived theoretical T4 equivalents (T4EQs), calculated arithmetically from the concentrations and relative potencies, accounted for about 40-70% of experimental T4EQs detected in indoor dusts, indicating that these compounds contributed strongly to the TTR-binding potency of indoor dust. Indoor sources of 2,4,6-TriBPh might be brominated flame retardants currently used in household materials such as electrical appliances. In contrast, the 2,3,4,5,6-PeCPh might be trace evidence of past use in agricultural chemicals and preservatives in indoor or outdoor environments, because its use has been banned since 1990 in Japan. 2,4,6-TriBPh and 2,3,4,5,6-PeCPh are ubiquitous potential thyroid-disrupting compounds in the home and work environments of Japan and other countries.

Persistent organic pollutants (POPs) in Caspian seals of unusual mortality event during 2000 and 2001.

Persistent organic pollutants including organochlorine pesticides, PCBs, and PCDDs/DFs were determined in the blubber of Caspian seals, which died during an outbreak of canine distemper virus in 2000 and 2001. DDTs were the predominant contaminants that ranged from 3.1 to 560 microg/g lipid. A negative correlation was observed between concentration of contaminants and blubber thickness. During spring, as the blubber layer becomes thin after breeding and moulting, seals may face higher risk due to the increased concentration of organochlorines in their bodies. TEQs in the blubber of Caspian seals (10-340 pg TEQ/g) were lower than those in seals from other locations, suggesting that toxic effects of these contaminants are a deal less in the present population and they are unlikely to be linked to mass mortality. The levels of PCBs and pesticides in Caspian seals, however, comparable to those in other aquatic mammals that have suffered from epizootics, might pose a risk of immunosuppression.

Characterization of semi-volatile organic compounds emitted during heating of nitrogen-containing plastics at low temperature.

Because of recent volume increases, appropriate management of plastic recycling, which generates various organic compounds, is required to ensure the chemical safety of the processes. The processing temperature and resin type are the important factors determining both the efficiency of the processes and the emission of chemicals. Therefore, we studied the thermal degradation of various plastics at various temperatures from 70 to 300 degrees C under oxygen-present conditions to identify the semi-volatile organic compounds (SVOCs) emitted and to understand their thermal behaviors. The plastics examined were nitrogen-containing resins, such as polyamide 6, polyurethane, melamine formaldehyde, urea formaldehyde and acrylonitrile-butadiene-styrene. Major commodity plastics were also investigated for comparison. In total, more than 500 SVOCs were detected as emissions from plastics. While various nitrogen-containing SVOCs were detected from nitrogen-containing resins, the major commodity plastics released only these, which possibly were included as additives. These results indicate that the nitrogen atoms in the SVOCs emitted originated from the resins and additives, and not from ambient air at low temperature. As a result of the detection of raw materials, degradation chemicals and by-products of the polymers in the emissions, we found that the variation in chemical species is dependent on the resins. Additives were also emitted from all the resins, meaning that these chemicals were also released to the environment at the temperature examined. In most cases, the numbers and concentrations of SVOCs increased with increasing heating temperature. The variation of thermal behaviors of SVOCs was related to the origins and chemical species of SVOCs.

Bioaccumulation of organochlorines in crows from an indian open waste dumping site: evidence for direct transfer of dioxin-like congeners from the contaminated soil.

To assess the significance of waste dumping sites as a source of chemical contamination to ecosystems, we analyzed the residue levels of polychlorinated dibenzo-p-dioxins (PCDDs), polychlorinated dibenzofurans (PCDFs), polychlorinated biphenyls (PCBs), and other organochlorines in the breast muscle of crows from a dumping site in the south of Chennai city, South India. Crows from the dumping site contained significantly higher total TEQs (60 +/- 27 pg/g lipid wt) than those from the reference sites (26 +/- 18 pg/g lipid wt). Especially, certain dioxin-like coplanar PCB congeners (Co-PCBs), such as CB-77 and CB-105, whose source is commercial PCBs,were significantly higher in crows from the dumping site than those from the reference sites. Profiles of PCDDs/DFs and Co-PCBs in crows from the dumping site were similar to those of soil at the same site, which was confirmed by principal component analysis. Furthermore, significant positive correlations were obtained between the congener-specific bioconcentration factors (BCFs) of PCDDs/DFs estimated from concentrations in crows and soil from the dumping site and the theoretical BCFs calculated from water-particle and lipid-water partitioning coefficients. On the other hand, the estimated BCFs had significant negative correlations with the molecular weight of PCDDs/DFs, indicating that molecular size limits their bioaccumulation. These results suggest that dioxin-like congeners in the soil of the dumping site were transferred directly to the crows through the ingestion of on-site garbage contaminated with soil, rather than through trophic transfer in the ecosystem. The present study provides insight into the ecological impacts of dumping sites.

Contamination status and accumulation features of persistent organochlorines in pet dogs and cats from Japan.

Concentrations of persistent organochlorines (OCs) such as polychlorinated dibenzo-p-dioxin (PCDDs), dibenzofurans (PCDFs), biphenyls, dichlorodiphenyltrichloroethane and their metabolites (DDTs), hexachlorocyclohexane isomers, hexachlorobenzene, and chlordane compounds were determined in genital organs of pet dogs and cats and pet foods from Japan. Levels of OCs in dogs were relatively lower than those in cats, while residue levels in their diets were almost similar, implying that accumulation and elimination mechanisms of these contaminants are different between dogs and cats. When bioconcentration factors (BCFs) were estimated from concentrations of OCs in dogs, cats, and their diets, BCFs of all the OCs except PCDD/DFs exceeded 1.0 in cats. On the other hand, in all the dogs, BCFs of DDTs were below 1.0, suggesting that dogs do not bioconcentrate DDTs. Furthermore, BCFs of all the OCs except PCDD/DFs in dogs were notably lower than those in cats, suggesting that dogs have higher metabolic and elimination capacity for these contaminants than cats. When residue levels of OCs in livers, adipose tissue, and genital organs of two pet dogs were examined, hepatic sequestration of PCDD/DFs and oxychlordane was observed.

Global pollution monitoring of polychlorinated dibenzo-p-dioxins (PCDDs), furans (PCDFs) and coplanar polychlorinated biphenyls (coplanar PCBs) using skipjack tuna as bioindicator.

In order to elucidate the global distribution of dioxins and related compounds, such as PCDDs, PCDFs and coplanar PCBs, levels of these compounds were determined in the muscle of skipjack tuna (Katsuwonus pelamis) collected from the offshore waters and open seas near Japan, Taiwan, Philippines, Indonesia, Seychelles and Brazil, and the Japan Sea, the East China Sea, the South China Sea, the Indian Ocean and the North Pacific Ocean. PCDDs, PCDFs and coplanar PCBs were detected in almost all the specimens collected from all the locations surveyed, indicating widespread contamination by these compounds in the marine environment. Higher concentrations of dioxins and coplanar PCBs were detected in the samples from temperate Asian regions, plausibly due to larger usage and anthropogenic generation in highly industrialized countries around the East China Sea and the South China Sea, such as Japan, Korea, Taiwan, Hong Kong and coastal China.

Toxicokinetics of PCDD, PCDF, and coplanar PCB congeners in Baikal seals, Pusa sibirica: age-related accumulation, maternal transfer, and hepatic sequestration.

To assess the toxicokinetic behavior and potential toxicity of polychlorinated dibenzo-p-dioxins (PCDDs), polychlorinated dibenzofurans (PCDFs), and coplanar polychlorinated biphenyls (PCBs) in Baikal seals, congener-specific levels and tissue distribution were evaluated in the liver and blubber, and the effects of biological factors including sex and growth were assessed. Total 2,3,7,8-TCDD toxic equivalents (TEQs) were in the range of 210-920 pgTEQ/g fat wt (180-800 pgTEQ/g wet wt) in the blubber and 290-7800 pgTEQ/g fat wt (10-570 pgTEQ/wet wt) in the liver. Non-ortho coplanar PCB126 was the most TEQ-contributed congener accounting for 37-59% of the total TEQs in the liver. From the unique congener profiles, weak metabolic properties of Baikal seals for 2,3,7,8-TCDF and 1,2,3,7,8-P5CDF are suggested. Concentrations of most congeners linearly increased with age in male seals, whereas in adult females the levels revealed an age-related decline. The increasing and declining rates were congener-specific. Maternal transfer rates of 5 representative congeners from adult female to pup through lactation, which was estimated from male-female differences in the body burden, was 1.1 ngTEQ/kg/day for the first pup and decreased with every lactational epoch. The liver-blubber distribution of 1,2,3,4,7,8-H6CDD, 1,2,3,6,7,8-H6CDD, PCB81, PCB126, and PCB169 was dependent on the hepatic total TEQ, indicating hepatic sequestration by induced cytochrome P450 (CYP). These results indicate that congener profile in Baikal seals is governed by complex factors including sex, tissue concentration, binding to CYP, and rates of absorption and metabolism/excretion.

Occurrence of PCBs, organochlorine insecticides, tris(4-chlorophenyl)methane, and tris(4-chlorophenyl)methanol in human breast milk collected from Cambodia.

The present study determined the concentrations of persistent organochlorines (OCs) such as DDT and its metabolites (DDTs), polychlorinated biphenyls (PCBs), hexachlorocyclohexane isomers (HCHs), hexachlorobenzene (HCB), chlordane compounds (CHLs), tris(4-chlorophenyl)methane (TCPMe), and tris(4-chlorophenyl)methanol (TCPMOH) in human breast milk from Cambodia. DDTs, PCBs, HCHs, HCB, CHLs, and TCPMe were detected in almost all the human breast milk samples analyzed, and the concentrations ranged from 310 to 11,000, 6.0 to 87, <0.12 to 21, <0.12 to 8.1, <0.12 to 5.3, and 2.9 to 70 ng/g lipid wt, respectively. TCPMOH was detected in only 10 among 36 samples. Concentrations of DDTs in human breast milk from Cambodia were notably higher than those from developed countries and comparable to those from other developing countries, where usage of DDT for agricultural and public health purposes has been suspected to be continuing still, implying the recent usage of DDT in Cambodia. On the other hand, concentrations of PCBs, HCHs, HCB, and CHLs in human breast milk from Cambodia were 1-2 orders of magnitude less than those from other countries, indicating that Cambodia is one of the less contaminated countries by these OCs. Significant correlation between concentrations of TCPMe and DDTs in human breast milk suggested that exposure to DDT is the source of TCPMe in Cambodian residents. Concentrations of OCs in human breast milk tended to decrease with an increase in the number of children, implying that the first infant would be exposed to higher levels of OCs from breast milk and might be at higher risk by these contaminants, especially DDTs in Cambodia. To our knowledge, this is the first comprehensive study on the residue levels of OCs in human breast milk from Cambodia.