Formation and contamination of PCDD/Fs, PCBs, PeCBz, HxCBz and polychlorophenols in the production of 2,4-D products

2,4-D Herbicide-Induced Hepatotoxicity: Unveiling Disrupted Liver Functions and Associated Biomarkers

2,4-dichlorophenoxyacetic acid (2,4-D) is a widely used herbicide worldwide and is frequently found in water samples. This knowledge has prompted studies on its effects on non-target organisms, revealing significant alterations to liver structure and function. In this review, we evaluated the literature on the hepatotoxicity of 2,4-D, focusing on morphological damages, toxicity biomarkers and affected liver functions. Searches were conducted on PubMed, Web of Science and Scopus and 83 articles were selected after curation. Among these studies, 72% used in vivo models and 30% used in vitro models. Additionally, 48% used the active ingredient, and 35% used commercial formulations in exposure experiments. The most affected biomarkers were related to a decrease in antioxidant capacity through alterations in the activities of catalase, superoxide dismutase and the levels of malondialdehyde. Changes in energy metabolism, lipids, liver function, and xenobiotic metabolism were also identified. Furthermore, studies about the effects of 2,4-D in mixtures with other pesticides were found, as well as hepatoprotection trials. The reviewed data indicate the essential role of reduction in antioxidant capacity and oxidative stress in 2,4-D-induced hepatotoxicity. However, the mechanism of action of the herbicide is still not fully understood and further research in this area is necessary.

Occurrences and spatial distributions of dioxin-like polychlorinated biphenyls in chlorobenzene and chloroethylene manufacturing processes in China

As a group of pollutants listed in the Stockholm Convention, polychlorinated biphenyls (PCB) should be eliminated and their releases should be controlled. For this purpose, a complete PCB emission inventory is urgently required. Current unintentional releases of PCB were dominantly focused on waste incineration and non-ferrous metal production industries. The formation of PCB in chlorinated chemical manufacturing processes is poorly understood. In this study, occurrences and inventory of dioxin-like PCB (dl-PCB) in three typical chemical manufacturing processes, including chlorobenzene and chloroethylene production processes, were investigated. The bottom residues, which were high boiling point by-products after rectification tower, contained higher concentration of PCB than other stage samples in monochlorobenzene production and trichloroethylene production processes. The PCB concentrations were as high as 1.58 ng/mL and 152.87 ng/mL, respectively, which should be further concerned. The toxic equivalent quantities (TEQ) of dl-PCB in monochlorobenzene, trichloroethylene, and tetrachloroethylene products were 0.25 μg TEQ/t, 1.14 μg TEQ/t, and 5.23 μg TEQ/t, respectively. The mass concentration and TEQ of dl-PCB determined in this research can be used for the further development of dl-PCB emission inventory from these chemical manufacturing industries. In addition, temporal and spatial trends of PCB releases from typical chemical manufacturing processes from 1952 to 2018 in China were clarified. The releases increased rapidly in the latest two decades and presented an expansion tendency from the southeast coastal areas to northern and central areas. The continuing upward trend for the output and the high dl-PCB TEQ of chloroethylene indicated significant releases of PCB from chemical manufacturing processes and should receive more attention.

Greener Method for the Application of TiO2 Nanoparticles to Remove Herbicide in Water

TiO₂ nanoparticles have emerged as a great photocatalyst to degrade organic contaminants in water; however, the nanoparticles dispersed in water could be difficult to be recovered and potentially become contaminant. Herbicide like 2,4-dichlorophenoxyacetic acid (2,4-D) used in agriculture usually ends up with a large fraction remaining in water and sediment, which may cause potential risk to human health and the ecosystem. This study proposes a greener method to utilize TiO₂ as photocatalyst to remove 2,4-D from water. Accordingly, TiO₂ nanoparticles (10-45 nm) were synthesized and grafted on lightweight fired clay to generate a TiO₂-based floating photocatalyst. Experimental testing revealed that 60.2% of 2,4-D (0.1 mM) can be decomposed in 250 min under UV light with TiO₂-grafted lightweight fired clay floating on water. Degradation fits well into the pseudo-first-order kinetic model. The floating photocatalysts can degrade approximately 50% 2,4-D in 250 min under sunlight and the degradation efficiency is stable for cycles. The results revealed that the fabrication of floating photocatalyst could be a promising and greener way to remove herbicide contaminants in water using TiO₂.

PCBs, PCNs, and PCDD/Fs in Soil around an Industrial Park in Northwest China: Levels, Source Apportionment, and Human Health Risk

The concentrations of polychlorinated biphenyls (PCBs), polychlorinated naphthalenes (PCNs), and polychlorinated dibenzo-p-dioxins and dibenzofurans (PCDD/Fs) were determined in soil samples collected around an industrial park in Northwest China, to investigate the potential impacts of park emissions on the surrounding environment. The total concentration ranges of PCBs, PCNs, and PCDD/Fs in the soil samples were in 13.2-1240, 141-832, and 3.60-156 pg/g, respectively. The spatial distribution and congener patterns of PCBs, PCNs, and PCCD/Fs indicated that there might be multiple contamination sources in the study area, so source apportionments of PCBs, PCNs, and PCCD/Fs were performed by a positive matrix factorization model based on the concentrations of all target congeners together. The results revealed that these highly chlorinated congeners (CB-209, CN-75, and OCDF) might be derived from phthalocyanine pigments, the legacy of Halowax 1051 and 2,4-D products, which together contributed nearly half of the total concentration of target compounds (44.5%). In addition to highly chlorinated congeners, the local industrial thermal processes were mainly responsible for the contamination of PCBs, PCNs, and PCDD/Fs in the surrounding soil. The total carcinogenic risk of PCBs, PCNs, and PCDD/Fs in a few soil samples (0.22 × 10-6, 0.32 × 10-6, and 0.40 × 10-6) approached the threshold of potential carcinogenic risk (1.0 × 10-6). Since these pollutants can continuously accumulate in the soil, the contamination of PCBs, PCNs, and PCDD/Fs in surrounding soil deserves continuous attention.

Formation and Inventory of Polychlorinated Dibenzo-p-dioxins and Dibenzofurans and Other Byproducts along Manufacturing Processes of Chlorobenzene and Chloroethylene

Chlorinated organic chemicals are produced and used extensively worldwide, and their risks to the biology and environment are of increasing concern. However, chlorinated byproducts [e.g., polychlorinated dibenzo-p-dioxins and dibenzofurans (PCDD/Fs)] formed during the commercial manufacturing processes and present in organochlorine products are rarely reported. The knowledge on the occurrences and fate of unintentional persistent organic chemicals in the manufacturing of organochlorine chemical is necessary for accurate assessment of the risks of commercial chemicals and their production. Here, PCDD/Fs were tracked throughout chlorobenzene and chloroethylene production processes (from raw materials to final products) by target analysis. Other byproducts that can further transform into PCDD/Fs were also identified by performing non-target screening. As a result, the PCDD/F concentrations were mostly the highest in bottom residues, and the octachlorinated congeners were dominant. Alkali/water washing stages may cause the formation of oxygen-containing byproducts including PCDD/Fs and acyl-containing compounds, so more attention should be paid to these stages. PCDD/Fs were of 0.17 and 0.21-1.2 ng/mL in monochlorobenzene and chloroethylene products, respectively. Annual PCDD/F emissions (17 g toxic equivalent in 2018) during chlorobenzene and chloroethylene production were estimated using PCDD/F emission factors. The results can contribute to the improvement of PCDD/F inventories for the analyzed commercial chemicals.

Urinary 2,4-dichlorophenoxyacetic acid in Chinese pregnant women at three trimesters: Variability, exposure characteristics, and association with oxidative stress biomarkers

Widespread exposure to herbicide 2,4-dichlorophenoxyacetic acid (2,4-D) could have potential adverse health effects on pregnant women. However, related data are scarce. This study aimed to characterize 2,4-D exposure among three trimesters of pregnancy and to explore the relationship of 2,4-D with oxidative stress biomarkers [i.e., 8-hydroxy-2'-deoxyguanosine (8-OHdG), 8-hydroxy guanosine (8-OHG), and 4-hydroxy nonenal mercapturic acid (HNEMA)] in urine. The present study analyzed 3675 urine samples of 1225 women (across the three trimesters of pregnancy) in Wuhan, central China. 2,4-D was detectable in 97.4% of the urine samples. The median unadjusted concentration of 2,4-D was 0.12 ng/mL, and the corresponding concentration adjusted by urinary specific gravity (SG-adjusted) was 0.13 ng/mL. The intraclass correlation coefficient of 2,4-D (SG-adjusted concentrations) was 0.07 across the three trimesters. Significantly higher urinary levels of 2,4-D were found in samples from younger pregnant women/samples collected during winter. In addition, significantly positive association between urinary concentrations of oxidative stress biomarkers and 2,4-D were found in repeated analysis; an interquartile range increase in 2,4-D was significantly (p < 0.001) associated with a 20.8% increase in 8-OHG, a 26.7% increase in 8-OHdG, and a 30.7% increase in HNEMA, respectively. Such associations were also found in trimester-specific analyses. This is the first time to quantify the urinary 2,4-D of pregnant women in China, and this study found significantly positive associations of 2,4-D with oxidative stress biomarkers. Further studies are needed to verify such associations and explore other potential adverse effects of 2,4-D exposure.

The Association Between 2, 4-Dichlorophenoxyacetic Acid and Erectile Dysfunction

Background

2, 4-dichlorophenoxyacetic acid (2,4-D) is one of the most frequently used herbicides in the world, and it has been linked with low testosterone; however, studies regarding its effect on erectile function are limited. The current study aimed to determine the association between the 2,4-D exposure and erectile dysfunction (ED) in men from the National Health and Nutrition Examination Survey (NHANES).

Methods

We analyzed data for urinary 2,4-D levels from 1,311 men (>20 years of age) in the NHANES 2001–2004. ED was assessed by a single, validated survey question. Multivariable logistic regression analysis utilizing sampling weights was performed to determine the relationship between 2,4-D exposure and ED.

Results

Multivariable logistic regression models demonstrated no statistically significant association between 2,4-D exposure and ED after full adjustment [odds ratio (OR) 1.02; 95% CI 0.77–1.36; P = 0.882)]. Men in the 2,4-D quartile 4 groups were not associated with an increased risk of ED (OR 1.13; 95% CI 0.74–1.75; P for trend = 0.481). Furthermore, the association between urinary 2,4-D level and ED was not significant in the subgroup analysis stratified by age, BMI, cardiovascular disease, hypertension, diabetes, and high cholesterol.

Conclusion

We demonstrated that there was no association between 2,4-D exposure and ED. Further studies are warranted to corroborate our results.

A field study of dioxins during co-processing of hazardous waste in multicomponent slurry gasifier

A field test was conducted to study the emission and distribution characteristics of dioxins during co-processing of hazardous waste in a multicomponent slurry gasifier (MCSG). The toxicity equivalent concentrations of polychlorinated dibenzo-p-dioxins (PCDDs) and polychlorinated dibenzofurans (PCDFs) in all exhaust gas, waste water, and solid waste under both blank condition (i.e., feedstock was normal coal-water slurry) and test condition (i.e., feedstock mixed with hazardous waste and labeling reagents) were analyzed. Results showed that organic matter was fully degraded in the MCSG. The dioxin amount in the black water flash steam increased with the addition of hazardous waste and chlorine in the feedstock, and octachlorodibenzo-p-dioxins (OCDD) with the largest increase is the most easily formed monomer in dioxins. The dioxin amount in all samples was far below the standard limit in China and other countries. This indicates the low environmental risk from dioxins during the co-processing process. The dioxin distribution trend in solid, liquid, and gas phase during co-processing did not change: 86.63%-94.18%, 0.02%-0.13%, and 5.8%-13.23% of PCDDs were distributed in the exhaust gas, waste water, and solid waste, respectively, while 6.10%-22.95%, 0.59%-0.80%, and 76.45%-93.10% of PCDFs were distributed in the exhaust gas, waste water, and solid waste, respectively.

Occurrence, profiles, and control of unintentional POPs in the steelmaking industry: A review

The steelmaking industry is an important source of unintentionally produced persistent organic pollutants (UP-POPs). This review summarizes the emission levels, characteristics, and formation mechanisms of UP-POPs, including halogenated dioxins, polychlorinated biphenyls, polychlorinated naphthalenes, and penta- and hexa- chlorobenzenes in the steelmaking industry to improve our understanding of the emissions of UP-POPs from the steelmaking industry. The factors influencing UP-POP formation during the iron ore sintering (IOS) process are also reviewed. The raw materials and temperature during the steelmaking process are important factors influencing UP-POP generation. Raw materials containing plastics, paints, cutting oil, rubber, and iron from electronic waste recycling can contribute to high emissions of UP-POPs during steelmaking processes. Electrostatic precipitator dust contains chlorine, carbon, and metals, which are usually recycled as a component of the raw material, and could also promote dioxin formation and emissions from IOS. Polychlorinated dibenzo-p-dioxins and dibenzofurans (PCDD/Fs) are easily formed in high concentrations at temperatures in the range of 200 °C-650 °C. This review also provides a comprehensive summary of the UP-POP emission limits in the steel industry worldwide and the best available techniques and environmental practices for UP-POP emission reduction. The information in this review will be useful for the reduction of UP-POPs in the steelmaking process.

Polychlorinated Biphenyl Emissions from Steelmaking Electric Arc Furnaces

Electric arc furnaces (EAFs) in steelmaking plants are a major source of dioxins. Preheating of steelmaking raw materials is widely used in EAFs to reduce energy consumption. Few studies have investigated emissions of dioxin-like polychlorinated biphenyls (PCBs) from EAFs, and the PCB emission levels and characteristics during preheating are unknown. In this study, PCB concentrations and distributions in stack gases emitted during EAF preheating were determined. The average dioxin-like PCB concentrations in stack gases emitted during preheating of three EAFs were 1236.1, 81,664.4, and 669.8 pg/Nm³, respectively. These values were greatly influenced by the composition of the steelmaking raw materials. The PCB profiles in all samples were dominated by less-chlorinated homologs. PCB emission factor for preheating in the EAFs is 0.58 µg WHO-TEQ/ton averagely, indicating significant emissions of PCBs from preheating process. The data will be useful for developing approaches for preventing and controlling PCB emissions from EAFs.

Congener patterns of polychlorinated dibenzo-p-dioxins, dibenzofurans and biphenyls as a useful aid to source identification during a contamination incident in the food chain

Polychlorinated dibenzo-p-dioxins (PCDDs), dibenzofurans (PCDFs) and biphenyls (PCBs) are still considered among the most important groups of contaminants in the food chain. Self-control by food producers and official control by authorities are important activities that allow contaminant sources to be traced and promote further reduction in food and feed levels. Strict but feasible maximum levels were set by the EU Commission for food and feed to support this strategy, as well as action levels and thresholds. When products exceed these levels, it is important to trace the source of contamination and take measures to remove it. Congener patterns of PCDD/Fs and PCBs differ between sources and are important tools for source identification. Therefore, patterns associated with different sources and incidents relating to various feed matrices and certain agricultural chemicals were collated from published scientific papers, with additional ones available from some laboratories. The collection was evaluated for completeness by presentations at workshops and conferences. Primary sources appear to derive from 5 categories, i) by-products from production of organochlorine chemicals (e.g. PCBs, chlorophenols, chlorinated pesticides, polyvinyl chloride (PVC)), ii) the result of combustion of certain materials and accidental fires, iii) the use of inorganic chlorine, iv) recycling/production of certain minerals, and v) certain naturally occurring clays (ball clay, kaolinite). A decision tree was developed to assist in the identification of the source.

Genotoxicity of mixtures of glyphosate with 2,4-dichlorophenoxyacetic acid chemical forms towards Cnesterodon decemmaculatus (Pisces, Poeciliidae)

Acute genotoxicity of commercial glyphosate (GLY) (Credit®)-, 2,4-D-acid (2,4-D) (Dedalo Elite)-, 2,4-D-amine (2,4-D DMA) (Weedar Full®)- and 2,4-D-ester (2,4-D BE) (Herbifen Super®)-based herbicide formulations alone and their combinations were analysed in Cnesterodon decemmaculatus. Mortality was evaluated as a lethal end-point and the single cell gel electrophoresis (SCGE) bioassay was used as a sublethal end-point. LC5096h values for Dedalo Elite was 0.46 mg/L and Herbifen Super® was 2.67 mg/L based on 2,4-D and 2,4-D BE, respectively. Results reveal a higher toxicity exerted on C. decemmaculatus after exposure to 2,4-D- rather than 2,4-D BE-based herbicide formulations. Overall, results demonstrated an enhancement in the genetic damage index committed to an enhancement of damaged erythrocytes of C. decemmaculatus when exposed to Credit®, Dedalo Elite, Weedar Full® and Herbifen Super® at 5% and 10% of LC5096h values alone as well as in their combinations. Overall, the combination of GLY plus 2,4-D or GLY plus 2,4-D DMA showed a synergistic pattern whereas the combination of GLY plus 2,4-D BE was antagonic. Furthermore, this research is pioneer in the assessment of lethality and genotoxicity induced by 2,4-D-, 2,4-D DMA- and 2,4-D BE-based formulations when combined with GLY-based formulated herbicides in fish after they are acutely exposed.

Analysis of global trends and gaps for studies about 2,4-D herbicide toxicity: A scientometric review

2,4-dichlorophenoxyacetic acid (2,4-D) is a herbicide that is used worldwide in agricultural and urban activities to control pests, reaching natural environments directly or indirectly. The research on 2,4-D toxicology and mutagenicity has advanced rapidly, and for this reason, this review summarizes the available data in Web of Science (WoS) to provide insights into the specific characteristics of 2,4-D toxicity and mutagenicity. Contrary to traditional reviews, this study uses a new method to quantitatively visualize and summarize information about the development of this field. Among all countries, the USA was the most active contributor with the largest publication and centrality, followed by Canada and China. The WoS categories 'Toxicology' and 'Biochemical and Molecular Biology' were the areas of greatest influence. 2,4-D research was strongly related to the keywords glyphosate, atrazine, water and gene expression. The studies trended to be focused on occupational risk, neurotoxicity, resistance or tolerance to herbicides, and to non-target species (especially aquatic ones) and molecular imprinting. In general, the authors have worked collaboratively, with concentrated efforts, allowing important advances in this field. Future research on 2,4-D toxicology and mutagenicity should probably focus on molecular biology, especially gene expression, assessment of exposure in human or other vertebrate bioindicators, and pesticide degradation studies. In summary, this scientometric analysis allowed us to make inferences about global trends in 2,4-D toxicology and mutagenicity, in order to identify tendencies and gaps and thus contribute to future research efforts.

Occurrence and characteristics of PCDD/Fs formed from Chlorobenzenes production in China

China had a large production capacity of chlorobenzenes. An extensive investigation was conducted to understand the occurrence and characteristics of PCDD/Fs from four chlorobenzene production plants. The concentrations of PCDD/Fs in mono-CB production and in a new di-CB production routine were revealed. Concentrations of PCDD/Fs in residues, byproducts, products and wastewater varied between 8.4*10³-4.0*10⁶ ng TEQ/kg, 1.5-5.0*10⁴ ng TEQ/kg, ND∼0.12 ng TEQ/kg and 6.0*10⁴-9.1*10⁴ pg TEQ/L, respectively. OCDF, 2,3,4,7,8-PeCDF, 1,2,3,4,7,8-HxCDF, and 2,3,7,8-TeCDF were the most abundant congeners of the 17 2,3,7,8-substituted PCDD/Fs. In most samples, PCDFs contributed more than 99% of the total TEQs of PCDD/Fs, in which 2,3,4,7,8-PeCDF was the dominating contributor. It is inferred PCDFs were mainly formed in the chlorination reactions. The emission factors were suggested and the amount of PCDD/Fs formed in CB production was estimated to be 450 g TEQ in 2012. Residue, byproduct and wastewater were potentially the main pathways of PCDD/Fs to the environmental releases.

Reassessment and update of emission factors for unintentional dioxin-like polychlorinated biphenyls

One of the major goals of the Stockholm Convention on Persistent Organic Pollutants is to continuously reduce the releases of unintentional persistent organic pollutants (POPs) such as polychlorinated dibenzo-para-dioxins and dibenzofurans (PCDD/PCDF) or polychlorinated biphenyls (PCB) from anthropogenic sources. Until now, most efforts have focused on the releases of PCDD/PCDF and to a lesser extent on unintentionally generated PCB, and therefore, release inventories reported as toxic equivalents (TEQ) do not include the twelve dioxin-like PCB (dl-PCB). In order to facilitate the development of national release inventories for the total TEQ - consisting of PCDD, PCDF and PCB - this study collected and summarized published emission factors (EFs) of unintentional dl-PCB or calculated them from measured data for the sources listed in the UNEP Toolkit. In total, 286 EFs for dl-PCB were found (or could be calculated) whereby 233 described release to air, 23 EFs addressed to residue, 25 EFs to product; and only 5 EFs addressed releases to land. Taking into account performance criteria such as the facility type and scale or abatement technologies, the EFs were grouped and assigned to the source categories and/or classes used in the UNEP Toolkit. With these newly added data and EFs of dl-PCB, the already existing EFs in the Toolkit can be improved and amended. In addition, a statistically significant correlation between the EF_Air of dl-PCB proposed in this study and EF_Air of PCDD/PCDF recommended in the Toolkit was observed.

Influence of long-range atmospheric transportation (LRAT) on mono-to octa-chlorinated PCDD/Fs levels and distributions in soil around Qinghai Lake, China

Long-range atmospheric transportation (LRAT) of persistent organic pollutants followed by their deposition in cold, arid regions is of wide concern. This problem occurs at Qinghai Lake in the northeastern Tibetan Plateau, a sparsely populated area with extreme weather conditions and little current or historical anthropogenic pollution. The concentrations and distribution patterns of the mono-to octa-chlorinated dibenzo-p-dioxin and dibenzofuran (PCDD/F) congeners in surface soil samples collected from around Qinghai Lake were quantified. Concentration differences between low-(mono-to tri-) chlorinated PCDD/Fs and high-(tetra-to octa-) chlorinated PCDD/Fs were measured. High PCDD/F levels were detected, with total concentrations of 15,108 ± 6323 pg/g for the 27 PCDD/F congeners and 15,104 ± 6324 pg/g for the low-chlorinated PCDD/Fs. The concentrations of 17 2,3,7,8-substituted PCDD/Fs were only 3.1 ± 4.4 pg/g and the corresponding international toxicity equivalency (I-TEQ) was 0.11 ± 0.22 pg I-TEQ/g. Given their higher vapor pressures and lower boiling points, low-chlorinated PCDD/Fs, were predominantly gaseous, whereas high-chlorinated PCDD/Fs were predominantly solid, indicating that there is a higher potential for long-range transport of low-chlorinated PCDD/Fs. Overall, because of their high LRAT potential, low-chlorinated PCDD/Fs may pose a greater risk to local ecosystems in cold, remote areas than high-chlorinated PCDD/Fs.

Perspective on polychlorinated dibenzo-p-dioxin and dibenzofuran emissions during chemical production in China: an overlooked source of contemporary relevance

Polychlorinated dibenzo-p-dioxins/dibenzofurans (PCDDs/DFs) are pollutants of significant global concern, and China with its large size and industries is one of the main dioxin-emitting countries in the world. PCDDs/DFs may be formed during the manufacture of chemicals and can either remain in the products as impurities or be emitted into the environment or residues disposed to landfills. The uncertainties in the environmental emissions of PCDDs/DFs from the chemical production industry in China are large because of the complex nature of the industry and variability in the technologies used and limited monitoring conducted. In the current study, we used the PCDD/DF emission factor from the updated United Nations Environment Programme (UNEP) toolkit 2013, information from otherwise published data, and the chemical production data in 2010 to estimate PCDD/DF emissions from the chemical productions in China. Based on these data, it was estimated that there is 1480 g toxic equivalent (TEQ) from the chemical production industry in China, which is much higher than the value that was estimated and used in the national implementation plans (NIPs) for China (102.4 g TEQ in 2004). These results indicate that current PCDD/DF emissions from the chemical production industry in China may be overlooked. Therefore, we suggest that attention should be paid to PCDD/DF emissions from the chemical production industry in future updates of the Chinese NIP and that appropriate measures to decrease PCDD/DF emissions should be taken by better monitoring of products and processes in chemical production industry.

Studies of pesticide residues in tomatoes and cucumbers from Kazakhstan and the associated health risks

The aim of the present study was to assess the level of pesticide residues in vegetables in the Almaty Region of Kazakhstan and to determine the potential health risks associated with the exposures to these pesticides. A total of 82 samples of cucumbers and tomatoes from top agro-based market and greenhouses were analysed using a gas chromatography-micro electron capture detector/nitrogen-phosphorous detector (GC-μECD/NPD), a multiresidue method to analyse 184 different pesticide types. The results indicated that more than half of samples (59 %) contained 29 pesticides, in which 10 are not registered in Kazakhstan, ranging from 0.01 to 0.88 mg kg(-1), and 28 % contained pesticide residues above maximum residue levels (MRLs). The estimated daily intakes (EDIs) ranged from 0.01 % of the acceptable daily intake (ADI) for pyrimethanil to 12.05 % of the ADI for lambda-cyhalothrin. The most critical commodity is triazophos and flusilazole in tomatoes, contributing 70.8 and 42.5 % to the acute hazard index (aHI). The results provided important information on the current pesticide contamination status of two commonly consumed vegetables and pointed an urgent need to control the use of plant protection products applied, especially potentially persistent pesticides, such as endosulfan and dicofol. These results also show that the detected pesticides may be considered a public health problem.

Formation of Polychlorinated Biphenyls on Secondary Copper Production Fly Ash: Mechanistic Aspects and Correlation to Other Persistent Organic Pollutants

Emission of unintentionally formed polychlorinated biphenyls (PCBs) from industrial thermal processes is a global issue. Because the production and use of technical PCB mixtures has been banned, industrial thermal processes have become increasingly important sources of PCBs. Among these processes, secondary copper smelting is an important PCB source in China. In the present study, the potential for fly ash-mediated formation of PCBs in the secondary copper industry, and the mechanisms involved, were studied in laboratory thermochemical experiments. The total PCB concentrations were 37-70 times higher than the initial concentrations. Thermochemical reactions on the fly ash amplified the potential toxic equivalents of PCBs. The formation of PCBs over time and the effect of temperature were investigated. Based on analyses of PCB homologue profiles with different reaction conditions, a chlorination mechanism was proposed for forming PCBs in addition to a de novo synthesis mechanism. The chlorination pathway was supported by close correlations between each pair of adjacent homologue groups. Formation of PCBs and multiple persistent organic pollutants, including polychlorinated dibenzo-p-dioxins, polychlorinated dibenzofurans and polychlorinated naphthalenes, occurred during the tests, indicating that these compounds may share similar formation mechanisms.

Formation Pathways of Mono- to Octa-Chlorinated Dibenzo-p-dioxins and Dibenzofurans in Main Organochemical Industries

The concentrations and formation pathways of mono- to octa-chlorinated dibenzo-p-dioxins (PCDDs) and dibenzofurans (PCDFs) were investigated in main organochemical industries. High levels of PCDDs and PCDFs were detected. The total concentrations of 27 PCDD/F congeners in chloranil, 2,4-D, and 1,4-dichlorobenzene were 5302397 ± 8944449, 20963 ± 15908, and 242 ± 67 pg g(-1), respectively, and the less-chlorinated PCDD/F levels were 12006 ± 20155, 9536 ± 5594, and 195 ± 94 pg g(-1), respectively. The distribution trends of less and more chlorinated PCDD/Fs were similar in different chemical plants because of their similar formation pathways, which may also be related to the degree of chlorination of chemical products and purification processes. 1,2,3,4-TeCDF and 2,4,8-TrCDF were selected as model molecules to calculate the bond dissociation energy, showing that 2-MCDF, 3-MCDF, and 2,8-DCDF are more easily formatted as shown by the analytical results. The formation pathways of less to more chlorinated PCDFs are proposed to explain why 2-MoCDF, 2,8-DiCDF, 2,4,8-TrCDF, and 2,3,4,7,8-PeCDF are the dominant congeners and to explain why 2,3,4,7,8-PeCDF is the largest contributor of I-TEQs in most studies.

Quantum chemical investigation on the mechanism and kinetics of OH radical-initiated atmospheric oxidation of PCB-47

The OH radical-initiated atmospheric oxidation degradation of 2,2',4,4'-tetrachlorobiphenyl (PCB-47) was investigated by using quantum chemical calculations. All possible pathways involved in the oxidation process were discussed. Potential barriers and reaction heats have been obtained to assess the energetically favorable reaction pathways and the relatively stable products. The study shows that the OH radicals are more likely to attack the C3 and C5 atom of the aromatic ring in the PCB-47 molecule to form PCB-OH adducts. Subsequent reactions are the addition of O2 or NO2 molecule to the PCB-OH adducts at the ortho position of the OH group. Water molecule plays an important role during the whole degradation process. The individual and overall rate constants were calculated by using the Rice-Ramsperger-Kassel-Marcus (RRKM) theory over the temperature range of 180-370K. At 298K, the atmospheric lifetime of PCB-47 determined by OH radicals is about 9.1d. The computational results are crucial to risk assessment and pollution prevention of PCBs.

Human exposure to PCDD/Fs and PCBs through consumption of fish and seafood in Catalonia (Spain): Temporal trend

The concentrations of PCDD/Fs and 18 PCBs (DL- and NDL-) were analyzed in 16 fish and seafood species widely consumed in Catalonia (Spain). The exposure of these pollutants was subsequently estimated according to various groups of population. The concentrations of PCDD/Fs and PCBs showed an important decrease in relation to the baseline study (2000) and our last survey (2008). Sardine and red mullet were the species showing the highest pollutant concentrations, while canned tuna and cuttlefish presented the lowest levels. Sardine was the main contributor to the exposure of PCDD/Fs and PCBs. In contrast, swordfish was the species with the lowest contribution to the exposure of PCDD/Fs, DL-PCBs, and PCDD/Fs+DL-PCBs, while clam was the minor contributor for NDL-PCBs and total PCBs. For all groups of population, the current intakes of PCDD/Fs and PCBs were lower than the TDI (1-4 pg WHO-TEQ/kg body weight/day), being children the group with the highest exposure. However, this exposure should not mean a health risk for this group of population. The current intake of PCDD/Fs and PCBs through fish and seafood consumption was similar or even lower than most values reported in recent studies all over the world.

Historical emissions of octachlorodibenzodioxin in a watershed in Queensland, Australia: estimation from field data and an environmental fate model

An octachlorodibenzodioxin (OCDD)-dominated contamination is present along the coast of Queensland, Australia. Several findings indicate that this contamination originates from pesticide use, although due to limited information on OCDD levels in the pesticides used, estimating past and current emissions of OCDD solely from pesticide use data is unfeasible. We used all the qualitative and quantitative information available on OCDD in pesticides together with a previously validated chemical fate model for a catchment in the Queensland Wet Tropics to back-calculate the emissions of OCDD from measured soil concentrations. We estimate that under different emission scenarios an average of 2,500 kg of OCDD was emitted within the modelled 1,685 km2 (Tully river) catchment between 1950 and 2010. Because this catchment represents only approximately 0.85% of the whole coast of Queensland under a similar contamination, the total amount of OCDD released in this region is considerably larger. For all emission scenarios, we could show that the OCDD currently present in agricultural soil is a result of historical emissions, and current-day emissions are less important in comparison to past emissions. Overall 18% was lost by degradation and 62% was buried below the agricultural surface soil, as a result of facilitated transport.

The release of persistent organic pollutants from a closed system dicofol production process

High concentrations of polychlorinated dibenzo-p-dioxins and dibenzofurans (PCDD/Fs) have been found to be produced in chemical processes in which chlorine is a raw material. Samples of workshop air, waste water, waste acid, and the dicofol product were collected from a pesticide factory in China that uses a closed-system dicofol production process, and were analyzed for PCDD/Fs and ΣDDTs. The ΣDDTs concentrations were 1.88-17.53 μg m(-3) in the workshop air samples, 4.85-456 μg kg(-1) in the waste water and waste acid samples, and 4.74 g kg(-1) in the dicofol product. The total estimated daily intakes of ΣDDTs for workers by inhalation in the workplace were in the range of 0.38-3.51 μg kg(-1)bwd(-1) for moderate activities. The annual amounts of ΣDDTs and p,p'-DDT directly released to the environment via the use of dicofol were 9,480 kg and 1,080 kg, respectively. The PCDD/F toxicity equivalent values (I-TEQs) in the waste water and waste acid samples ranged from 1.5 to 122 pg I-TEQ kg(-1) and 86.3 ng I-TEQ kg(-1) in the dicofol sample. The annual amount of PCDD/Fs released to the environment was 0.17 g I-TEQ. From the PCDD/F distribution patterns, it is suggested that the major pathway for PCDD/F formation involves precursor synthesis during the production of dicofol in the closed-system process.