Toxic Equivalency Research Articles

Examining Bald Eagle Contaminant Exposure and Reproductive Risk Above and Below Dams on Great Lakes Tributaries.

Removing lowermost dams can reestablish fish passage on Great Lakes tributaries. This can increase the transfer of contaminants from anadromous fish to piscivorous wildlife upstream; however, concentrations of bioaccumulative contaminants in Great Lakes fish have decreased over the last several decades. We analyzed concentrations of PCBs and the toxic equivalence (TEQs) calculated from PCBs, DDTs, other organochlorine pesticides, and PBDEs in the plasma of bald eagle nestlings above and below lowermost dams on five river systems in Michigan from 1999 to 2013. We examined relationships between contaminants and metrics of reproductive success from 1997 to 2018, including the effects of year and location relative to the lowermost dam. Σ20PCB and p,p'-DDE were important in characterizing differences in contaminant mixtures above and below dams. Concentrations of contaminants were generally greater below dams than above. There were generally greater nest success and more nestlings per nest below dams, but nest location explained little variability (R2 values = 0.03-0.15). Neither Σ20PCB nor p,p'-DDE was a significant predictor of 5-year productivity means by river reach despite concentrations exceeding previously established effects thresholds for healthy bald eagle populations in the Great Lakes (≥ 1 nestling/nest). Our study indicates that dams may continue to reduce the upstream movement of contaminants to bald eagles, but at the measured concentrations, contaminants did not impair productivity and reproductive success as indicated by nestlings per nest. Additional information about population dynamics could clarify population-level effects of contaminants on bald eagles and to what degree these populations are self-sustaining throughout the Great Lakes.

Hypofractionated versus standard fractionation radiotherapy for merkel cell carcinoma

Purpose/Objective(s)Merkel cell carcinoma (MCC) radiation treatment has historically consisted of standard 1.8–2 Gy fractions treated daily over 4–6 weeks. Hypofractionated treatment regimens have demonstrated tumor control and toxicity equivalence to standard fractionation regimens for common cutaneous malignancies such as basal cell and squamous cell carcinomas. Herein we report the outcomes of hypofractionated versus standard fractionation radiotherapy for MCC at our institution.Materials/MethodsThe study involved a retrospective review of MCC patients treated with radiotherapy. Treatment characteristics and patient outcomes, including acute toxicities, disease recurrence and survival data were collected. The cumulative incidence of local and distant failures was estimated, with death as a competing risk.ResultsA total of 29 treatment courses for 24 patients were included, of which 13 involved standard fractionation with curative intent, 10 involved hypofractionated radiotherapy with curative intent, and 6 involved single fraction (8 Gy) palliative radiation. Half the patients were treated to a head/neck site. A subset of patients treated adjuvantly with curative intent included 8 standard fractionation and 8 hypofractionated radiotherapy patients. No statistically significant differences in local and/or distant failure or overall survival was observed between the patient groups.ConclusionHypofractionated radiotherapy for MCC was associated with similar treatment outcomes relative to standard fractionation. In our limited patient sample, hypofractionated radiation treatment achieved similar results with similar toxicity and fewer treatments. Further analysis of a larger patient population with longer follow up is needed to confirm treatment tolerability and efficacy.

Interactions between polycyclic aromatic hydrocarbons (PAHs) and phospholipids cause PAH migration into wet gums during the oil degumming process

The refining process can reduce PAH contamination levels in vegetable oils, but the safety of byproducts requires further attention. We hypothesize that interactions between PAHs and phospholipids could contribute to PAH migration into the wet gums and subsequently evaluated the distribution of PAHs during different degumming processes. Enzymatic degumming achieved over 99.90 % removal of phospholipids from soybean oil and sunflower seed oil and minimized the toxic equivalency quotient of PAHs in wet gums (approximately 0.05 μg/kg). Notably, greater PAH reduction was correlated with greater phospholipid removal in degummed soybean oil. Quantum chemical calculations indicated that van der Waals forces between PAHs and phospholipids could cause PAH migration, with higher phospholipid contents and PAH contamination in soybean oil providing more favourable conditions than in sunflower seed oil. This study will help to improve the quality of edible oils and provide information on the mechanisms underlying PAH migration.

Polychlorinated Biphenyl Levels and Associated Health Risks in Indoor Atmosphere of Beauty Salons

Exposure to high concentrations of Polychlorinated Biphenyl (PCBs) has negative impacts on human wellbeing and the climate. This study determined the concentration, sources and health risks of PCBs in selected beauty shops in Ilorin, Kwara state. Air samples from fourteen beauty salons were taken using Solvent-Impregnated Polyurethane Foam (SIP-PUF) passive samplers for 30 days. The concentration of PCBs was determined with Gas Chromatography-Mass Spectrometry (GC–MS) operated in a Selected Ionization Mode (SIM). The health risk assessment of the PCBs was estimated using the Toxicity Equivalence Quotient (TEQ), Incremental Life Cancer Risk (ILCR), and Hazard Quotient (HQ) prescribed by United State Environmental Protection Agency (USEPA). The Positive Matrix Factorization (PMF) method was used in the source apportionment study. The average concentration of the PCBs ranged from 0.11–3.32 µg/m3 . The average TEQs for the PCBs in the beauty salon ambient air ranged between 2.96 × 10−1 - 9.30 × 10−1 ng WHO-TEQ/m3 . ILCRs and HQs estimated for the beauty shops considered were lower than 10-6 and 1 (USEPA set limit) for both adults and children. Eight factors were identified to be associated with the PCB sources; the most predominant sources are combined paint and pigment and mixed sources, which accounted for 20.08 and 28.91% of the total PCBs, respectively.

Release of polychlorinated biphenyls (PCBs) and organochlorine pesticides (OCPs) from cigarette butts into the aquatic environment: Levels and ecotoxicity

Discarded cigarette waste may leach toxic elements and can contaminate different environments. In this study, the levels of organochlorine pesticides (OCPs) and polychlorinated biphenyls (PCBs) in cigarette butts (CBs) leachates were determined, and the release rate of these pollutants from three CBs types such as smoked CBs with and without tobacco (SCBs and SFs) and unsmoked filters (USFs) were examined. The mean concentration levels of PCBs compounds were <LOD-1.36, <LOD-1.02 and <LOD-0.86 μg/L in SCBs, SFs, and USFs leachates, respectively. The concentrations of OCPs in SCBs and SFs leachates were <LOD-0.14 and <LOD-0.10 μg/L, respectively. The toxic equivalent (TEQ) of the dioxin-like PCBs from the CBs leachate samples ranged from 2×10-6-1×10-4 ng/L. Notwithstanding the insignificant TEQ values in CBs leachates, continuous discharge and the toxicities of the PCBs in the aquatic environments could have harmfully impacts on the the water boddies and/or human health. Globally, considering all the littered CBs and their chemical contents, further efforts are needed to investigate address, and mitigate this type of contamination.

The burden of cancer attributable to dietary dioxins and dioxin-like compounds exposure in China, 2000–2020

Dioxin is a typical class of persistent organic pollutants (POPs) that could cause cancer. In China, the contribution of dietary dioxins to the cancer burden remains underexplored. This study evaluates the cancer risk and burden due to dietary dioxins and dioxin-like compounds among Chinese residents from 2000 to 2020. Based on adjustments in China’s dioxin policies, the study period was divided into three stages with split years of 2007 and 2014 to estimate the toxic equivalent (TEQ) of dioxins. Participants in dietary surveys conducted in 31 provinces were included. Dietary exposure to dioxins was estimated in a probability model and compared with the provisional tolerable monthly intake (PTMI). The risk was assessed using carcinogenic slope factors and expressed as the incremental lifetime cancer risk (ILCR). A two-stage model evaluated the burden of cancer attributable to dietary dioxins and dioxin-like compounds. Among all food categories, the highest concentration of dioxins and dioxin-like compounds was observed in aquatic foods at 0.15 pg TEQ/kg. Median dietary exposure to dioxins among Chinese residents decreased from 12.39 pg TEQ/kg/month to 8.72 pg TEQ/kg/month between 2000 and 2020. Consequently, the ILCR due to dietary dioxins declined from 6.44 × 10-5 to 4.53 × 10-5. The health risks were higher in younger groups and among residents of coastal areas (P < 0.001). The burden of cancer attributable to dietary intake of dioxins and dioxin-like compounds in the Chinese population in 2000–2007, 2008–2014, and 2015–2020 was 2.25 (2.09–2.42) per 100,000, 2.20 (2.06–2.35) per 100,000, and 1.68 (1.60–1.77) per 100,000, respectively. Furthermore, the disease burden was highest for prostate cancer in men and for breast cancer in women. The dioxin management policies has reduced the burden of cancer attributable to dietary exposure to dioxins and dioxin-like compounds in China. However, excess exposure in coastal areas and children remains a priority for attention.

Temporal variations in airborne PCDD/F and dl-PCB concentrations surrounding the dioxin-remediated areas in Da Nang, Vietnam, and health risk assessments.

The air pollution levels from polychlorodibenzo-p-dioxins/polychlorodibenzofurans (PCDD/Fs) and dioxin-like polychlorobiphenyls (dl-PCBs) in three residential areas located north, west, and south of the Da Nang airport were determined by using passive air samplers containing polyurethane foam (PUF) discs with 3-month sampling intervals from 2017 to 2020. The total toxic equivalents (∑TEQs) of the PCDD/Fs and dl-PCBs, using WHO2005-TEFs, were highest north of the airport (134 to 10610fg WHO-TEQ/PUF day, with an average of 1108fg WHO-TEQ/PUF day). The ∑TEQs were lower west of the airport, between 159 and 381fg WHO-TEQ/PUF day and averaged 230fg WHO-TEQ/PUF day. The lowest ∑TEQs occurred south of the airport, with ranges of 76 and 331fg WHO-TEQ/PUF day and an average of 152fg WHO-TEQ/PUF day. Construction activities, including excavation and transportation of dioxin-contaminated soil north of the airport, have increased airborne PCDD/F and dl-PCB contamination and health risks. The average daily doses of PCDD/Fs and dl-PCBs through inhalation (ADDA) for residents located north of the airport were the highest (10.9 to 3434fg WHO-TEQ/kg BW/day and average: 597fg WHO-TEQ/kg BW/day). Residents located west of the airport faced lower health risks (13-123fg WHO-TEQ/kg BW/day and average: 39fg WHO-TEQ/kg BW/day). Residents south of the airport were exposed to a minimum of 6.2-107fg WHO-TEQ/kg BW/day, with an average of 28fg WHO-TEQ/kg BW/day. The maximum and average ADDA values for residents north of the airport exceeded 10% of the tolerable daily intake (TDI) recommended by the WHO (100-400fg WHO-TEQ/kg BW/day). In comparison, all the ADDA values for residents located west and south of the airport were less than and within 10% of the TDI.

Comprehensive model for predicting toxic equivalents (TEQ) reduction due to dechlorination of polychlorinated dibenzo-p-dioxin and dibenzofurans (PCDD/F congeners)

Remediation-focused predictive tools for polychlorinated dibenzo-p-dioxins (PCDD) and polychlorinated dibenzofurans (PCDF) rely on transformation models to evaluate the reduction in total contaminant load and toxic equivalency (TEQ). In this study, a comprehensive model predicting the profiles of PCDD/F congeners and the associated TEQs was developed. The model employs first-order kinetics to describe the transformation of 256 reactions for 75 PCDD congeners and 421 reactions for 135 PCDF congeners. It integrates the growth of anaerobic microbial guilds using Monod kinetics on hydrogen release compounds and stoichiometric growth for Dehalococcoides sp. The effects of temperature, salinity, pH, and availability of vitamin B12 (a cofactor) were also integrated. The PCDD/F congeners model was used to extract the first-order dechlorination rate constants from a number of pure culture and mixed microbial microcosm studies. Simulations for the transformation of PCDD/F congeners at concentrations representative of the Tittabawassee or Saginaw Rivers and watershed in MI, USA were carried out. For a starting TEQ of 5000 ng per kg dry sediment (ppt), the model predicted a decrease in the overall TEQ to below 2000 ppt after 2.6 years and below 250 ppt after ∼21 years. The developed model may be used for extracting rates from microcosm studies and to evaluate the effect of engineering interventions on TEQ reduction.

Uptake, Elimination and Metabolism of Brominated Dibenzofurans in Mice.

Polybrominated dibenzofurans (PBDFs) are major brominated dioxins in the environment, but information on their bioaccumulation potential and toxicokinetics is limited. This study conducted oral exposure experiments with C57BL/6J mice to investigate the uptake ratios, distribution in the liver, plasma and brain, metabolism, and elimination kinetics of four bromine/chlorine-substituted dibenzofurans (TrBDF: 2,3,8-tribromo, TeBDF: 2,3,7,8-tetrabromo, PeBDF: 1,2,3,7,8-pentabromo, TrBCDF: 2,3,7-tribromo-8-chloro) in comparison with 2,3,7,8-tetrachlorodibenzo-p-dioxin (TCDD). The hepatic uptake ratios of 2,3,7,8-substituted dibenzofurans were lower than that of TCDD (up to 84% of the administered doses) and decreased with the number of Br substitutions (42%, 33%, and 29% for TrBCDF, TeBDF, and PeBDF, respectively). The brain uptake ratios of these dibenzofurans were less than 0.05%, and the plasma-to-brain transfer ratio also decreased with the Br number. All 2,3,7,8-substituted compounds were eliminated from the liver following first-order kinetics, with half-times in the order of TrBCDF (5.6 days) < TeBDF (8.8 days) ≈ TCDD (8.7 days) < PeBDF (13 days). The non-2,3,7,8-substituted TrBDF was poorly retained in the liver (<0.01% of the dose at 1 day) and rapidly eliminated following two-phase kinetics. All dibenzofurans were metabolised into monohydroxylated products in the liver, but the contribution of this metabolic pathway to hepatic elimination was only significant for TrBDF. As the toxic effects of dioxin-like compounds are influenced by their biological persistence, the slow elimination of TrBCDF, TeBDF, and PeBDF observed in this study suggests that exposure risk of brominated dibenzofurans may be underestimated using the toxic equivalency factors of the less persistent chlorinated analogues.

Temporal, spatial, and seasonal variations in airborne PCDD/F and dl-PCB concentrations around Bien Hoa hot spot, Vietnam, and health risk assessments

Passive air samplers were used to monitor polychlorodibenzo-p-dioxins and dibenzofurans (PCDD/Fs) and dioxin-like polychlorobiphenyls (dl-PCBs) between 2020 and 2022 in four residential areas around Bien Hoa hot spot (BHS) including Trung Dung (TD), Tan Phong (TP), Quang Vinh (QV), and Buu Long (BL). The total toxic equivalents of PCDD/Fs and dl-PCBs (∑TEQs) were highest in the TD area, from 284 to 642 fg TEQ/PUF day. Next was the QV area, where ∑TEQs ranged from 229 to 569 fg TEQ/PUF day. Then, ∑TEQs varied from 205 to 503 fg TEQ/PUF day in the TP area. The lowest ∑TEQs were between 179 and 385 fg TEQ/PUF day in the BL area. The temporal, spatial, and seasonal variations in concentrations of PCDD/Fs and dl-PCBs were related to the prevailing wind direction and the distance from each area to the dioxin hot spot. The average ∑TEQs for all four areas surrounding BHS in the dry season (423 fg TEQ/PUF day) were 1.4 times higher than in the rainy season (303 fg TEQ/PUF day). Health risk assessments from airborne dioxin exposure were estimated using the average daily doses through inhalation (ADDI). The ADDI for residents surrounding BHS ranged from 14.6 to 208 fg TEQ/kg BW/day. The ADDI values by areas were as follows: 23.2–208 fg TEQ/kg BW/day in the TD, 18.7–184 fg TEQ/kg BW/day in the QV, 16.7–163 fg TEQ/kg BW/day in the TP, and 14.6–125 fg TEQ/kg BW/day in the BL. These ADDI values remained within and below the 10% threshold of the WHO-recommended tolerable daily intake (100–400 fg TEQ/kg BW/day). It is necessary to control the excavation activities inside the BHS and cover the temporary storage sites of dioxin-contaminated materials to minimize the emissions of PCDD/Fs and dl-PCB into the ambient air.

Sediment organic matter predicts polycyclic aromatic hydrocarbon distribution in port sediments

We evaluated the influence of organic matter in polycyclic aromatic hydrocarbons (PAHs) in port sediments using multiple linear regression (MLR) and prediction models. Total sediment PAHs ranged between 45 and 3230 ng/g dw (average: 557 ± 962 ng/g dw), with PAHs primarily originating from river inputs, confined to areas near the estuaries. Coal/biomaterial combustion and petroleum mainly contribute to the presence of PAHs along estuaries, with medium-high to high ecological risks. MLR TPAHs prediction model included variables, namely, the marine-derived total organic carbon (TOCmar), terrestrial fraction of organic matter (Fterr), and carbon-to‑nitrogen ratio (CNR). Results indicate that mainly marine- followed by terrestrially-derived organic matter influenced sediment PAH distribution. Total organic nitrogen and CNR were variables in the toxic equivalent (TEQ) prediction model, demonstrating that terrestrial pollution sources primarily influenced TEQ. The study analyzes and predicts the impact of organic matter and its sources on the fate and transport of PAHs in port sediments.

Polycyclic aromatic hydrocarbons in fish from four lakes in central and eastern China: Bioaccumulation, pollution characteristics, sources, and health risk assessment

Polycyclic aromatic hydrocarbons (PAHs) are highly concerning environmental pollutants due to their toxicity, persistence, and bioaccumulation. In this paper, concentrations and compositions of 16 United States Environmental Protection Agency (USEPA) priority control PAHs in the fish collected from four lakes in central and eastern China were analyzed. 18 species of fish were collected from four typical lakes, namely Taihu Lake, Danjiangkou Reservoir, Yuncheng Salt Lake, and Nansi Lake. Quantitative analysis of PAHs were carried out with gas chromatograph/mass spectrometer, and 13 out of 16 PAHs were identified, with the main components being pyrene, chrysene, naphthalene, and benzo(b)fluoranthene. The accumulation of PAHs in fish from Taihu Lake, Danjiangkou Reservoir, Yuncheng Salt Lake, and Nansi Lake was 28.75–47.27, 26.60–31.93, 33.56–39.30, and 27.22–43.01 ng·g−1, respectively. The toxic equivalents of high-cyclic PAHs in fish of the four lakes were significantly higher than those of low-cyclic and middle-cyclic PAHs (P < 0.05). In Taihu Lake, Danjiangkou Reservoir, and Nansi Lake, the toxicity equivalents were predominantly contributed by benzo[a] pyrene (BaP), while in Yuncheng Salt Lake, dibenzo(a,h) anthracene (DahA) was the main contributor. The residents in central and eastern China exposed to PAHs had a negligible non-cancer risk (non-carcinogenic risk values <1) and a potential low cancer risk. It was noteworthy that the Pleuronichthys cornutus and Lateolabrax japonicus from Yuncheng Salt Lake could pose carcinogenic risks (>10−4) to humans, with benzo[b]fluoranthene (BbF) having the highest risk contribution rate. Source analysis indicated that the main source of PAHs in fish was combustion sources. BaP, DahA, and BbF could become potential pollutants of concern in the field of ecotoxicology. The results of this study on PAHs bioaccumulation, pollution characteristics, sources and health risks in fish from four lakes would provide a scientific basis for local governments to formulate targeted environmental management policies, pollution control measures, and public health strategies.

Insight into the inhibition mechanisms of Ca-, N-, S-containing compounds on persistent organic pollutant formation from the thermal reaction of anthracene on copper chloride

Four inhibitors (CaO, CaS, CH4N2S, and (NH4)2SO4) were employed to inhibit the formation of multiple unintentional persistent organic pollutants (POPs) and environmentally persistent free radicals (EPFRs) using anthracene as a precursor, with CuCl2 serving as both a transition metal catalyst and chlorine source. The inhibition mechanisms were elucidated in terms of chlorine immobilization, catalyst deactivation, and free radical regulation. The inhibition efficiency of the four inhibitors on polychlorinated dibenzo-p-dioxins and dibenzofurans (PCDD/Fs), polychlorinated biphenyls (PCBs), and polychlorinated naphthalenes (PCNs) ranged from 64.7 % to 98.4 %, with the corresponding inhibition rates on toxic equivalency quantity ranging from 86.3 % to 99.7 %. The distribution of homologs shifted towards less chlorinated species, indicating effective suppression of chlorination. Calcium- and nitrogen-containing compounds consumed chlorine sources by forming CaCl2, CaClOH, and NH4Cl, while sulfur-containing compounds deactivated catalysts by forming CuSO4. EPFRs derived from anthracene were identified as carbon-centered anthracene-type and anthraquinone-type radicals. Positive correlations were observed between POPs and EPFRs concentrations, suggesting the pivotal role of organic free radicals as intermediates in POPs formation. Anthraquinones derived from anthracene underwent decomposition, recombination and chlorination, leading to the formation of PCDD/Fs and PCBs. The addition of inhibitors reduced EPFRs concentrations by 74.2–95.1 %. Sulfur- and nitrogen-containing inhibitors generated radicals that attacked POPs precursors and intermediates, forming heteroatomic compounds and inhibiting POPs formation. These findings enhanced the understanding of the source control mechanisms of POPs and provided theoretical and technical support for the synergistic inhibition of POPs and EPFRs in industrial thermal processes.

Polychlorinated dibenzo-p-dioxin and dibenzofuran contamination of free-range eggs: estimation of the laying hen’s soil ingestion based on a toxicokinetic model, and human consumption recommendations

Polychlorinated dibenzo-p-dioxins and dibenzofurans (PCDD/Fs) are ubiquitous in the environment. The main route of human exposure is through food consumption. Soil contamination can be problematic for sanitary safety depending on the usage of the soil, such as farming. In case of environmental soil contamination with PCDD/Fs, hen’s eggs may be contaminated due to soil ingestion by hens. For this reason, it is important to understand the parameters that influence eggs’ contamination when hens are raised in contaminated areas. After the discovery of a contaminated area in Lausanne (Switzerland), we collected hens’ eggs from ten domestic-produced eggs and one farm. Based on PCDD/F measurements of eggs and soil, and a toxicokinetic model, we estimated individual hen’s soil intake levels and highlighted appropriate parameters to predict the dose ingested. Recommended weekly consumption for home-produced eggs was calculated based on the tolerable weekly intake proposed by EFSA in 2018. The most important parameter to assess the soil ingestion does not seem to be the soil coverage by vegetation but rather the hen’s pecking behaviour, the latter being difficult to estimate objectively. For this reason, we recommend using a realistic soil ingestion interval to assess the distribution of egg PCDD/F concentration from free-range hens reared on contaminated soil. The addition of soil contamination in the toxicokinetic model can then be used to recommend to the general population weekly consumption of eggs. The consumption by adults of free-range eggs produced on land with soil containing >90 ng toxic-equivalent (TEQ)/kg dry soil should be avoided. Even with a low level of soil contamination (1–5 ng TEQ/kg dry soil), we would recommend consuming not more than 5 eggs per week for adults and no more than 2 eggs for children below 4 years old.

Toxicity Equivalency Factors for Tetrodotoxin Analogues Determined with Automated Patch Clamp on Voltage-Gated Sodium Channels in Neuro-2a Cells.

Tetrodotoxin (TTX) is a potent marine neurotoxin, responsible for numerous poisoning incidents and some human fatalities. To date, more than 30 TTX analogues have been identified, but their individual toxicities and roles in poisoning remain largely unknown. In this work, the toxicity equivalency factors (TEFs) of five TTX analogues were determined by assessing the blockade of voltage-gated sodium channels in Neuro-2a cells using automated patch clamp (APC). All TTX analogues were less toxic than TTX. The derived TEFs were applied to the individual TTX analogues concentrations measured in pufferfish samples, using liquid chromatography coupled to tandem mass spectrometry (LC-MS/MS). A comparison of these results with those obtained from APC analysis demonstrated that TEFs can be effectively used to translate LC-MS/MS analytical data into meaningful toxicological information. This is the first study to utilize APC device for the toxicological assessment of TTX analogues, highlighting its potential as a bioanalytical tool for seafood safety management and human health protection.

A Quantitative Adverse Outcome Pathway for Embryonic Activation of the Aryl Hydrocarbon Receptor of Fishes by Polycyclic Aromatic Hydrocarbons Leading to Decreased Fecundity at Adulthood.

Quantitative adverse outcome pathways (qAOPs) describe the response-response relationships that link the magnitude and/or duration of chemical interaction with a specific molecular target to the probability and/or severity of the resulting apical-level toxicity of regulatory relevance. The present study developed the first qAOP for latent toxicities showing that early life exposure adversely affects health at adulthood. Specifically, a qAOP for embryonic activation of the aryl hydrocarbon receptor 2 (AHR2) of fishes by polycyclic aromatic hydrocarbons (PAHs) leading to decreased fecundity of females at adulthood was developed by building on existing qAOPs for (1) activation of the AHR leading to early life mortality in birds and fishes, and (2) inhibition of cytochrome P450 aromatase activity leading to decreased fecundity in fishes. Using zebrafish (Danio rerio) as a model species and benzo[a]pyrene as a model PAH, three linked quantitative relationships were developed: (1) plasma estrogen in adult females as a function of embryonic exposure, (2) plasma vitellogenin in adult females as a function of plasma estrogen, and (3) fecundity of adult females as a function of plasma vitellogenin. A fourth quantitative relationship was developed for early life mortality as a function of sensitivity to activation of the AHR2 in a standardized in vitro AHR transactivation assay to integrate toxic equivalence calculations that would allow prediction of effects of exposure to untested PAHs. The accuracy of the predictions from the resulting qAOP were evaluated using experimental data from zebrafish exposed as embryos to another PAH, benzo[k]fluoranthene. The qAOP developed in the present study demonstrates the potential of the AOP framework in enabling consideration of latent toxicities in quantitative ecological risk assessments and regulatory decision-making. Environ Toxicol Chem 2024;43:2145-2156. © 2024 SETAC.

Assessment of polycyclic aromatic hydrocarbon (PAH) profiles in heat-processed meat and fish: a study on health risk evaluation

The profiles of polycyclic aromatic hydrocarbons (PAHs) in selected heat-processed meat and fish were evaluated to determine the potential health risk associated with consumption. The samples were analysed using a gas Chromatography-Mass spectrometer. Different concentrations of individual PAHs were detected in the samples, with the smoked samples having the highest concentrations. The total PAHs (mg/kg) in smoked samples were 2.763 ± 0.185 (game meat), 1.618 ± 0.102 (mackerel fish), and 1.718 ± 0.129 (catfish), whereas levels (mg/kg) in grilled samples were 0.771 ± 0.049 (chicken) and 0.911 ± 0.053 (fish). The total carcinogenic PAH (PAH7) concentrations (mg/kg) in grilled chicken and fish and smoked (game meat, mackerel fish, and catfish) samples were 0.231, 0.294, 0.440, 0.309, and 0.332, while their total PAH8 concentrations were 0.356, 0.371, 0.537, 0.465, and 0.476 respectively. The non-carcinogenic PAH risk estimations, both individually (hazard quotient) and cumulatively (hazard index), were below 1 in all the samples. The mean concentrations of PAH markers B[a]P and the PAH4 were above the EU limits in both the smoked and the grilled samples tested. This implies that exposure to high levels of these PAHs through regular consumption of these products may increase the risk of developing certain types of cancer and other health issues. The smoked fishes has the lowest MOE values for the PAH8 compared to the other samples. The margin of exposures (MOEs), carcinogenic toxic equivalent (TEQ), and excess cancer risk (ECR) also indicated that frequent consumption of smoked fish (mackerel or catfish) by an adult of 70 kg body weight above the reported intake rate of 0.0019 kg/AME/day for a prolonged period may have higher cancer risks than in other samples. Smoked game meat had the highest PAH16 level, but indicated a relatively lower risk level, possibly because of its relatively low intake rate (0.0004 kg/AME/day).

Unveiling respiratory health risks: PCDD/Fs adhering to particulate matter (PM10 and PM2.5) in Bien Hoa City, Dong Nai, Vietnam

This study investigates the concentrations of atmospheric aerosol particles (PM, including PM2.5 and PM10), as well as the presence and distribution of polychlorinated dibenzo-p-dioxins and dibenzofurans (PCDD/Fs) in ambient air in Bien Hoa City (Dong Nai province, Vietnam) during the dry and rainy seasons in 2023. The concentrations of 7 PCDDs and 10 PCDFs congeners in PM10 or PM2.5 were determined using gas chromatography-mass spectrometry (GC-MS). The results show that the concentration of PM10 and PM2.5 were 54.7 ± 9.4 µg/m3, 65.3 ± 7.6 µg/m3, and 39.6 ± 7.9 µg/m3, 58.9 ± 12.6 µg/m3, in the rainy season and dry season, respectively. This reveals that while only PM2.5 concentration levels in the dry seasonexceed national ambient air quality standards, but all of PM2.5 concentration levels consistently exceeded WHO guidelines. The study highlights the dominance of PM2.5 and its adverse health implications, as evidenced by the PM2.5/PM10 ratio (0.74 and 0.85 for the rainy and dry seasons, respectively) and its association with worse air quality. Analysis of PCDD/Fs concentrations in PM samples demonstrates their comparable levels in both seasons, with OCDD being the most abundant species. Furthermore, the study estimates the toxic equivalency (TEQ) of PCDD/Fs and assesses health risks, revealing a potentially high cancer risk from exposure to these pollutants, particularly PM2.5 under WHO2005-TEQ. Several PCDD/Fs- WHO2005-TEQ congeners exhibit higher concentration levels in PM2.5 compared to PM10, suggesting differential particulate matter dynamics and potential environmental implications. These findings underscore the urgent need for mitigation strategies to alleviate air pollution and reduce associated health risks in the dioxin hotspot of Vietnam.

Quantifying and normalizing the combined phytotoxicity of mixed-valence chromium in soil integrated by toxicity equivalence

When Cr(VI) and Cr(III) coexist, the reasonable assessment of the combined toxicity of chromium in soil and its ecological risk is still not well resolved. In the present study, exogenous mixed concentration combinations were set up to determine the interaction and combined toxicity of Cr(VI) and Cr(III), which were quantified as measured total and resin extractable forms for dose-response experiments with barley root elongation. The concept of toxicity equivalence "α" (the ratio of toxicity intensity coefficient between Cr(VI) and Cr(III), which can be expressed as the relative toxic strength of Cr(VI) to Cr(III)) was proposed for the toxicity assessment of mixed-valence chromium in soil. The results showed that the dose-response relationship was determined more precisely by the extended independent action model (e-IA) than traditional models (e.g., concentration addition model), and the mutual antagonism for resin extractable form (Resin-Cr) was stronger than the measured total form (T-Cr). The values of toxicity equivalence (α) between coexisting Cr(VI) and Cr(III) as Resin-Cr and T-Cr were 0.74 and 160, respectively, which indicated Resin-Cr(III) had relatively stronger toxicity than Resin-Cr(VI), while T-Cr(III) was much less than T-Cr(VI). The α values between Cr(VI) and Cr(III) decreased with their more active forms (decreased to about 0.5% of the original), even as total concentration and activity in solutions, making a dialectical view of the toxicity of both in different forms necessary. Finally, the log-logistic models were developed, enabling mixed-valence Cr toxicity to be assessed from a unilateral perspective using the Cr(III) equivalence concentration (Cr(III)-eq). This work provided innovative ideas for ecological threshold studies for mixed-valence metals in soils.

Đánh giá mức độ phát thải của các chất polyclodibenzo-p-dioxin và polyclodibenzofuran phát sinh không chủ định từ lò đốt rác chất thải sinh hoạt và rác thải công nghiệp ở Việt Nam

Polychlorinated dibenzo-p-dioxins (PCDD) and polychlorinated dibenzofurans (PCDF) are the most toxic substances among the group of unintentional persistent organic pollutants (U - POP) generated from many sources, in which domestic and industrial waste incinerators are the highest emission risk. Assessment of pollution potential and dioxin/furan emissions from incinerators in developing countries, including Vietnam, is still limited; especially in-depth studies on the content and characteristics of PCDD/PCDF emitted into the atmosphere. Therefore, the research team evaluated the emission potential and characteristics of 07 PCDD and 10 PCDF, those are considered to be the most toxic isomers and congeners, from stack gas samples collected from incinerators at 33 facilities in 11 provinces in Vietnam. The total concentration of PCDD/PCDF in the industrial incinerators’ emission ranged from 37.3 to 3348.6 pg TEQs/m3 and domestic waste incinerators had lower total concentrations and fluctuated within about 37.3-1323.8 pg TEQs/m3. The characteristic of incinerator emissions is that the proportion of 2,3,7,8- TCDD accounts for 2.9 to 9.04%. The highest contributing concentrations were congeners 1,2,3,7,8-PeCDD, with its contributing percentage from 22.95-32.42%. The second largest contributor is congeners 2,3,4,7,8- PeCDF, accounting for 20.94- 21.50% of the total toxic congeners of PCDD/PCDF in both types of incinerators. However, in terms of toxic equivalency (TEQ), the concentration of industrial waste incinerators is much higher than that of domestic waste incinerators. The results of stack gas samples showed that the PCDD/PCDF content for domestic waste incinerators has 5/17 establishments that exceeded the permissible standard threshold: 0.6 ng/Nm3, according to QCVN 61-MT:2016/BTNMT. Industrial waste incinerators have 5/16 establishments that exceeded the permissible standard threshold: 0.6ng/Nm3 for furnaces with a capacity of 300kg/hour according to QCVN 30:2012/BTNMT.