Bioaccumulation and human health risk assessment of DDT and its metabolites (DDTs) in yellowfin tuna (Thunnus albacares) and their prey from the South China Sea

Distribution, sources and health risk assessment of DDT and its metabolites in agricultural soils in Zhejiang Province, China

Dichlorodiphenyltrichloroethane (DDT) is well known for its harmful effects and has been officially banned as a pesticide around the world. However, DDT pollution still exists in natural environments in China because DDT degrade very slowly. In this study, 60 soil samples were collected from Cixi, Zhejiang Province, and the levels of DDTs and its metabolites in soil and health risks were investigated. The results showed that the detection rate of DDT in soil samples were 100%, and the total DDTs residue in soil ranged from 0.007 to 1.208 mg/kg, with an average of 0. 113±0. 035 mg/kg, which exceeded the second-level Chinese soil environmental quality standard for farmland soil. The average residuals of p,p'-DDT, p,p'-DDE (dichlorodiphenyldichloroethylene), p,p'-DDD (dichlorodiphenyldichloroethane) and o,p'-DDT accounted for 34.8%, 50.9%, 8.0% and 6.3% of the total DDTs, respectively. The DDD/DDE ratios indicated a dehydrochlorination of DDT to DDE under aerobic conditions at most sampling sites. The ratios of (p,p'-DDE+p,p'-DDD)/p,p'-DDT and o,p'-DDT/p,p'-DDT indicating the DDT in the field were mainly introduced via industrial DDT and dicofol, including historical residue and fresh input. The health risk assessment showed that DDT-contaminated sites do not pose a non-carcinogenic risk to humans, and pose a very low risk of cancer to children and a low risk of cancer to adults. Overall, this study helps to understand the distribution, sources and health risks of DDT in typical soils.

Mechanisms of Digestive Enzyme Response to Acute Salinity Stress in Juvenile Yellowfin Tuna (Thunnus albacares)

This study investigates the effect of a sudden change in salinity for 48 h on the digestive enzyme activity of juvenile yellowfin tuna. The treatment included a control salinity of 32‱ in natural seawater and an experimental salinity of 29‱. Acute stress experiments were carried out on 72 juvenile yellowfin tuna (646.52 ± 66.32 g) for 48 h to determine changes in digestive enzyme activity in different intestinal sections over time (0 h, 12 h, 24 h, 48 h). The activities of pepsin, trypsin, α-amylase, lipase, and chymotrypsin in the digestive organs (stomach, foregut, and pyloric ceca) of juvenile yellowfin tuna were measured. Pepsin and pancreatic protease in the experimental group were significantly lower than in the control group (p < 0.05). α-amylase showed a fluctuating trend of decreasing and then increasing, and its activity trend was pyloric ceca > foregut > stomach. The lipase activity of gastric tissues decreased at the beginning and then increased, reaching a minimum at 24 h (2.74 ± 1.99 U·g protein-1). The change of lipase in the pyloric ceca and foregut was increasing and then decreasing. The lipase activity trend was pyloric ceca > foregut > stomach. The chymotrypsin showed a decreasing and increasing trend and then stabilized at 48 h with a pattern of pyloric ceca > foregut > stomach. Similarly, the gut villi morphology was not significantly altered in the acutely salinity-stressed compared to the non-salinity-stressed. This study suggests that salinity may change the digestive function of juvenile yellowfin tuna, thereby affecting fish feeding, growth, and development. On the contrary, yellowfin tuna is highly adapted to 29‱ salinity. However, excessive stress may negatively affect digestive enzyme activity and reduce fish digestibility. This study may provide a scientific basis for a coastal aquaculture water environment for yellowfin tuna farming, which may guide the development and cultivation of aquaculture.

An insights of organochlorine pesticides categories, properties, eco-toxicity and new developments in bioremediation process

Organochlorine pesticides (OCPs) have been used in agriculture, increasing crop yields and representing a serious and persistent global contaminant that is harmful to the environment and human health. OCPs are typically bioaccumulative and persistent chemicals that can spread over long distances. The challenge is to reduce the impacts caused by OCPs, which can be achieved by treating OCPs in an appropriate soil and water environment. Therefore, this report summarizes the process of bioremediation with commercially available OCPs, considering their types, impacts, and characteristics in soil and water sources. The methods explained in this report were considered to be an effective and environmentally friendly technique because they result in the complete transformation of OCPs into a non-toxic end product. This report suggests that the bioremediation process can overcome the challenges and limitations of physical and chemical treatment for OCP removal. Advanced methods such as biosurfactants and genetically modified strains can be used to promote bioremediation of OCPs.

Comparative in vitro and in silico study on the estrogenic effects of 2,2-bis(4-chlorophenyl)ethanol, 4,4'-dichlorobenzophenone and DDT analogs

DDT and its transformation products (DDTs) are frequently detected in environmental and biological media. Research suggests that DDT and its primary metabolites (DDD and DDE) could induce estrogenic effects by disturbing estrogen receptor (ER) pathways. However, the estrogenic effects of DDT high-order transformation products, and the exact mechanisms underlying the differences of responses in DDT and its metabolites (or transformation products) still remain unknown. Here, besides DDT, DDD and DDE, we selected two DDT high-order transformation products, 2,2-bis(4-chlorophenyl) ethanol (p,p'-DDOH) and 4,4'-dichlorobenzophenone (p,p'-DCBP). We aim to explore and reveal the relation between DDTs activity and their estrogenic effects by receptor binding, transcriptional activity, and ER-mediated pathways. Fluorescence assays showed that the tested 8 DDTs bound to the two isoforms (ERα and ERβ) of ER directly. Among them, p,p'-DDOH exhibited the highest binding affinity, with IC₅₀ values of 0.43 μM and 0.97 μM to ERα and ERβ, respectively. Eight DDTs showed different agonistic activity toward ER pathways, with p,p'-DDOH exhibiting the strongest potency. In silico studies revealed that the eight DDTs bound to either ERα or ERβ in a similar manner to 17β-estradiol, in which specific polar and non-polar interactions and water-mediated hydrogen bonds were involved. Furthermore, we found that 8 DDTs (0.0008-5 μM) showed distinct pro-proliferative effects on MCF-7 cells in an ER-dependent manner. Overall, our results revealed not only for the first time the estrogenic effects of two DDT high-order transformation products by acting on ER-mediated pathways, but also the molecular basis for differential activity of 8 DDTs.

Status, sources, and human health risk assessment of DDT pesticide residues in river sediments in a highly developed agricultural region in the upper Yangtze River in China

The concentrations of DDT and its metabolites in 19 sediment samples from a highly developed agricultural region in the upper reaches of the Yangtze River were measured. Non-carcinogenic hazard quotient for different age groups was evaluated using reference doses provided by the USEPA, and the excess lifetime cancer risk due to eating fish was assessed based on the local eating habits. The results showed that this region had a high level of residual DDT (12.84 ± 8.97 ng/g), which mainly came from the historically used technical DDT in agriculture. The non-carcinogenic risk was just acceptable in the region, but 11 of the 19 sites showed an unacceptable carcinogenic risk. Although DDT has been banned for decades, there were still notable health risks, especially for children. Special attention should be given to the potential health risks in historically developed agricultural regions.

Organophosphate esters (OPEs) in a coral reef food web of the Xisha Islands, South China Sea: Occurrence, trophodynamic, and exposure risk

Despite organophosphate esters (OPEs) are widely prevalent in the environment, however, limited information is available regarding their occurrence, trophodynamics, and exposure risks in coral reef ecosystems. In this study, 11 OPEs were investigated in a tropical marine food web (7 fish species and 9 benthos species) from the Xisha (XS) Islands, South China Sea (SCS). The ∑₁₁OPEs were 1.52 ± 0.33 ng/L, 2227 ± 2062 ng/g lipid weight (lw), 1024 ± 606 ng/g lw, and 1800 ± 1344 ng/g lw in seawater, fish, molluscs, and corals, respectively. Tris (2-chloroisopropyl) phosphate (TCIPPs) were the dominant OPEs in seawater, fish, and molluscs, while tris (2-butoxyethyl) phosphate (TBOEP) predominated in coral tissues. Abiotic and biotic factors jointly affect the OPEs enrichment in marine organisms. Trophic magnification factors (TMFs) (range: 1.31-39.2) indicated the biomagnification potency of OPEs. A dietary exposure risk assessment indicated that OPEs at current levels in coral reef fish posed a low risk to human health but were not negligible. Overall, this study contributes to a further understanding of the environmental behaviors of OPEs in coral reef ecosystems.

Recent Advances in the Synthesis, Characterization, and Application of Carbon Nanomaterials for the Removal of Endocrine-Disrupting Chemicals: A Review

The large-scale production and frequent use of endocrine-disrupting chemicals (EDCs) have led to the continuous release and wide distribution of these pollutions in the natural environment. At low levels, EDC exposure may cause metabolic disorders, sexual development, and reproductive disorders in aquatic animals and humans. Adsorption treatment, particularly using nanocomposites, may represent a promising and sustainable method for EDC removal from wastewater. EDCs could be effectively removed from wastewater using various carbon-based nanomaterials, such as carbon nanofiber, carbon nanotubes, graphene, magnetic carbon nanomaterials, carbon membranes, carbon dots, carbon sponges, etc. Important applications of carbon nanocomposites for the removal of different kinds of EDCs and the theory of adsorption are discussed, as well as recent advances in carbon nanocomposite synthesis technology and characterization technology. Furthermore, the factors affecting the use of carbon nanocomposites and comparisons with other adsorbents for EDC removal are reviewed. This review is significant because it helps to promote the development of nanocomposites for the decontamination of wastewater.

Spatial Variation in Contaminant Occurrence in Marine Fishes and Prawns from Coastal Tanzania

There are limited data on organic contaminants in marine biota from coastal Tanzania, especially on the occurrence of industrial-use contaminants such as polychlorinated biphenyls (PCBs) and polybrominated diphenyl ethers (PBDEs). The present study, performed in 2018-2019 in coastal Tanzania and Zanzibar Island, aimed at assessing spatial variation in the occurrence of PCBs; brominated flame retardants (BFRs), including PBDEs; and organochlorine pesticides, including dichlorodiphenyltrichloroethane (DDT), among three locations that differ in degree of anthropogenic activity. Analyzed samples included edible tissues of marine fishes and prawns representing different trophic levels and habitats. The results indicate a mainland-island difference, with fishes and prawns collected on Zanzibar having significantly lower PCB and DDT concentrations but higher concentrations of hexachlorobenzene compared to the two mainland locations. The highest contaminant concentrations were found in fishes and prawns collected around central Dar es Salaam harbor, with median ΣPCBs ranging from 22.3 to 577 ng/g lipid weight and ΣDDTs from 22.7 to 501 ng/g lipid weight, suggesting local sources. Concentrations of PBDEs were similar among locations, suggesting more diffuse sources. None of the "newer-type" BFRs, including compounds introduced as replacements for PBDEs, were detected in the present study. Stable isotope values of carbon (δ¹³ C) and nitrogen (δ¹⁵ N) varied among locations, and the relationship between contaminants and δ¹⁵ N varied among locations and habitat (pelagic/demersal). Concentrations measured in the present study are below European guidelines for human consumption of fishes and prawns. However, industrial-use contaminants should be monitored in developing countries because they are contaminants of emerging concern as a result of increasing industrialization and global trade of used products and wastes. Environ Toxicol Chem 2022;41:321-333. © 2021 The Authors. Environmental Toxicology and Chemistry published by Wiley Periodicals LLC on behalf of SETAC.

Monitoring of pesticides in surface water, pesticides removal efficiency in drinking water treatment plant and potential health risk to consumers using Monte Carlo simulation in Behbahan City, Iran

Excessive application of pesticides to control pests and weeds leads to contaminating bodies of water and health problems for consumers. The present study was designed to investigate the concentration of pesticides in raw water originated from the Marun River as well as the treated water of the drinking water treatment plant in Behbahan City. The efficiency of each treatment process was evaluated. Moreover, the health risks caused by detectable pesticides for consumers of treated water were assessed. The target pollutants were extracted using droplet liquid-liquid microextraction and detected by a gas chromatograph-mass spectrophotometer. The results showed relatively high mean concentrations of organophosphate pesticides ranging from 0.87 to 3.229 μg/L in the river water and low concentrations of organochlorine pesticides, except for 1,3-dichloropropene with the concentration of 3.58 μg/L. Alachlor had a rather high concentration (2.44 μg/L) in the river water. The concentration of pesticides in the drinking water had been reduced to an acceptable amount. The major part of pesticides removal occurred in coagulation-flocculation and rapid sand filtration units (87 %) due to the hydrophobic nature of pesticides and the use of GAC in the filtration unit. Based on the risk assessment estimates, the total hazard quotient (THQ) for all the pesticides was much less than one. The value of THQ was higher in younger individuals and children for all the given pesticides. The highest value of THQ in children was 0.2 which was attributed to aldrin. Similarly, the carcinogenic risk (CR) of aldrin for children and teenagers was in the unsafe range (more than 10^-4) while the CR for other target compounds in all the age groups was negligible (10^-4-10^-6 or less). The high concentration of pesticides in the river water might be concerning and therefore selling and using pesticides, especially the banned ones, should be more regulated.

1,1,1-trichloro-2,2-bis (p-chlorophenyl)-ethane (DDT) and 1,1-Dichloro-2,2-bis (p, p'-chlorophenyl) ethylene (DDE) as endocrine disruptors in human and wildlife: A possible implication of mitochondria

1,1,1-trichloro-2,2-bis (p-chlorophenyl)-ethane (DDT) and its main metabolite 1,1-Dichloro-2,2-bis (p, p'-chlorophenyl) ethylene (DDE) act as endocrine disruptors in humans and wildlife. Immunomodulatory functions have also been attributed to both xenobiotics. DDT was banned in the 1970s due to its toxicity, but it is still produced and used for indoor residual spraying with disease vector control purposes. Due to their persistence and lipophilic properties, DDT and DDE can bioaccumulate through the food chain, being stored in organisms' adipose depots. Their endocrine disruptor function is mediated by agonist or antagonist interaction with nuclear receptors. Present review aimed to provide an overview of how DDT and DDE exposure impacts reproductive and immune systems with estrogen-disrupting action in humans and wildlife. Studies showing DDT and DDE impact on mitochondrial function and apoptosis pathway will also be reviewed, suggesting the hypothesis of direct action on mitochondrial steroid receptors.

Persistent organic pollutants in sea bird eggs from the Indian Ocean's Mascarene Basin

We report the concentrations of persistent organic pollutants (POPs) in seabird eggs from St. Brandon's Atoll, a tropical island system in the western Indian Ocean. Ten eggs each of sooty terns (Onychoprion fuscatus), fairy terns (Gygis alba), and common noddies (Anous stolidus) were collected from the atoll. For a terrestrial reference, we analysed three feral chicken (Gallus gallus domesticus) eggs from the same location. Sooty tern eggs contained the highest mean concentrations of three chemical classes: ƩCHL₃ (0.21 ng/g wm; wet mass), ƩPCB₁₀ (1.5 ng/g wm), and ƩPBDE₆ (1.1 ng/g wm). Fairy tern eggs contained the highest mean concentrations of HCB (0.68 ng/g wm) and ƩCHB₅ (0.83 ng/g wm). The chicken eggs contained the highest mean concentrations of ƩDDT₃ (2.6 ng/g wm), while common noddy eggs contained the highest mean concentrations of ƩHCH₂ (0.5 ng/g wm). We surmise that the differences in chemical composition between species reflect different pollutant compositions in prey from the bird's different foraging ranges. The sooty terns foraging offshore contained higher POPs concentrations than the nearshore-foraging common noddies. Fairy tern eggs contained intermediate concentrations, commensurate with their intermediate foraging. Inter-island differences in contaminant concentrations were seen between eggs of the common noddies from St. Brandon's Atoll and Rodrigues Island, 520 km to the south-east. Concentrations of contaminants found in this study were lower than values quantified by other studies, making St. Brandon's Atoll an ideal reference site to monitor background concentrations of POPs in the tropical Indian Ocean.

Combined effect of microplastics and DDT on microbial growth: A bacteriological and metabolomics investigation in Escherichia coli

Microplastics (MPs) can adsorb toxic chemicals in biological or environmental matrixes and thus influence their behavior and availability. In order to investigate how the combined pollution of MPs and toxic organic chemical influence microbial growth and metabolism, Escherichia coli (E. coli) was grown in a complex, well-defined media and treated with polystyrene microplastics (PS MPs) and dichloro-diphenyl-tricgloroethane (DDT) at human relevant concentration levels. In vivo metabolites captured by a novel solid phase microextraction (SPME) probe, were used to reflect the metabolic dysregulation of E. coli under different pollution stresses. Results showed that the toxic effect of DDT displayed a distinct dose-dependent phenomenon while the existence of PS decreased the growth and metabolic interference effect of DDT on E. coli. Adsorption results revealed a mechanism that PS weakened the adverse impact of DDT by decreasing its free concentration in the treated culture media. Tricarboxylic acid (TCA) cycle related enzymes activities and antioxidant defense related substances of E. coli also proved the mechanism. The current study is believed to broaden our understanding of the ecotoxicity of MPs with toxic organic chemicals on microorganism.