Contaminant vulnerability in the critical zones like groundwater (GW)-seawater (SW) continuum along the entire Gujarat coast was investigated for the first time through an extensive water monitoring survey. The prime focus of the study was to evaluate whether or not: i) seawater intrusion induced metal load translates to toxicity; ii) in the coastal groundwater, metal distribution follows the pattern of other geogenic and anthropogenic contaminants like NO₃- and F-; and iii) what future lies ahead pertaining to metal fate in association with saturation conditions of the coastal aquifers. The spatial distribution of contaminants depicts that the Gulf of Khambhat area is highly contaminated. Ecological risk assessment (ERA) indicates that the Gujarat coast is experiencing a high ecological risk compared to the southeast coast of India. Investigation results revealed that metals, pH, NO₃, and CO₃ are more vulnerable at the SW-GW mixing interface. An increase in pH is reflected in fewer ionic species of metals in the GW. Salinity ingress due to seawater intrusion (SWI) reduces the toxicities of all trace metals except Cu, attributed to the increase of Ca in GW, leading to dissociation of CuCO₃. Reactive species are dominant for Zn and Cd; and M-CO₃ ligands are dominant for Cu and Pb owing to the undersaturation of dolomite and calcite in the aquifer system. SWI tends to increase the metal load but the toxicity of metals varies with the density of industries, anthropogenic activities, changes in the mixing-induced saturation conditions, and intensive salt production across the coast. Multivariate analysis confirmed that the hydrogeochemical processes change due to GW-SW mixing and dictates over natural weathering. The ecological risk index (ERI) for the Arabian sea is experiencing moderate (300 ≥ ERI>150) to high ecological risk (ERI >600). Children population is likely to encounter a high health risk through ingestion and dermal exposure than adults. Overall, the study emphasizes the complexity of toxicity-related health impacts on coastal communities and suggests the dire need for frequent water monitoring along the coastal areas for quick realization of sustainable development goals.

To better evaluate the potential risks of aquatic polycyclic aromatic compounds (PACs), multiple approaches have been implemented in this study to assess the human health and ecological risks of parent, nitrated and oxygenated polycyclic aromatic hydrocarbons (PAHs, NPAHs and OPAHs) in the surface water of Jialing and Yangtze Rivers in downtown Chongqing in southwestern China. The concentrations of ∑PAHs (334 ± 125 ng L⁻¹) were much higher than those of ∑OPAHs (20.2 ± 7.49 ng L⁻¹) in the two rivers, while NPAHs were barely detected. Concentrations of detected PACs were higher in wet season than dry season, probably resulted from the elevated particle input due to heavy rainfall in wet season. Concentrations of PAHs were higher in the particulate phase than dissolved phase, while OPAHs levels showed a reverse pattern. The partition coefficients (Kₚ) of PACs in the water-SPM (suspended particulate matter) system were mainly affected by SPM concentrations and octanol/water partition coefficients of specific PACs. Human health risks calculated from non-probabilistic risk assessment model and probabilistic risk assessment model based on Monte Carlo simulation showed similar data pattern with slight difference in absolute values. Both models revealed potential or even severe human health risks contributed mainly by dermal exposure to aquatic PACs in this study. Furthermore, these models also manifested that infant stage was highly sensitive for PAC exposure. Sensitivity analysis indicated that health risk results was most sensitive to Benzo[a]pyrene equivalent toxic concentration (BaPₑq), followed by showering time and daily water intake volume. Levels of ecological risks and contributions of individual PACs differed from models based on different quality values. The adequacy of toxicity data was crucial for the reliability of ecological risk assessment.

The application of exogenous biodegradation strains in pesticide-polluted soils encounters the challenges of migration and persistence of inoculants. In this study, the degradation characteristics, vertical migration capacity, and microbial ecological risk assessment of an enhanced green fluorescent protein (EGFP)-tagged 2-Methyl-4-chlorophenoxyacetic acid (MCPA)-degrading strain Cupriavidus gilardii T1 (EGFP) were investigated in the laboratory and field soils. The optimum remediation conditions for T1 (EGFP) was characterized in soils. Meanwhile, leaching experiments showed that T1 (EGFP) migrated vertically downwards in soil and contribute to the degradation of MCPA at different depths. After inoculation with T1 (EGFP), a high expression levels of EGFP gene was observed at 28 d in the laboratory soil and at 45 d in the field soil. The degradation rates of MCPA were ≥ 60% in the laboratory soil and ≥ 48% in the field soil, indicating that T1 (EGFP) can efficiently and continuously remove MCPA in both laboratory and field conditions. In addition, the inoculation of T1 (EGFP) not only showed no significant impact on the soil microbial community structure but also can alleviate the negative effects induced by MCPA to some extent. Overall, our findings suggested that T1 (EGFP) strain is an ecologically safe resource for the in situ bioremediation of MCPA-contaminated soils.

The presence of contaminants of emerging concern in the aquatic environment directly impacts water-living organisms and can alter their living functions. These compounds are often metabolized and excreted, but they can also be accumulated and spread through the food chain. The metabolized contaminants can also lead to the formation of new compounds with unknown toxicity and bioaccumulation potential. In this work, we have studied the occurrence, bioconcentration, and biotransformation of CECs in glass eels (Anguilla anguilla) using UHPLC-HRMS. To select the target CECs, we first carried out an environmental risk assessment of the WWTP effluent that releases directly into the Adour estuary (Bayonne, Basque Country, France). The risk quotients of every detected contaminant were calculated and three ecotoxicologically relevant contaminants were chosen to perform the exposure experiment: propranolol, diazepam, and irbesartan. An experiment of 14 days consisting of 7 days of exposure and 7 days of depuration was carried out to measure the bioconcentration of the chosen compounds. The quantitative results of the concentrations in glass eel showed that diazepam and irbesartan reached BCF ≈10 on day 7, but both compounds were eliminated after 7 days of depuration. On the other hand, propranolol's concentration remains constant all along with the experiment, and its presence can be detected even in the non-exposed control group, which might suggest environmental contamination. Two additional suspect screening strategies were used to identify metabolization products of the target compounds and other xenobiotics already present in wild glass eels. Only one metabolite was identified, nordiazepam, a well-known diazepam metabolite, probably due to the low metabolic rate of glass eels at this stage. The xenobiotic screening confirmed the presence of more xenobiotics in wild glass eels, prominent among them, the pharmaceuticals exemestane, primidone, iloprost, and norethandrolone.

The use of reclaimed water in agriculture represents a promising alternative to relieve pressure on freshwater supplies, especially in arid or semiarid regions facing water scarcity. However, this implies introducing micropollutants such as pharmaceutical residues into the environment. The fate and the ecotoxicological impact of valsartan, an antihypertensive drug frequently detected in wastewater effluents, were evaluated in soil-earthworm microcosms. Valsartan dissipation in the soil was concomitant with valsartan acid formation. Although both valsartan and valsartan acid accumulated in earthworms, no effect was observed on biomarkers of exposure (acetylcholinesterase, glutathione S-transferase and carboxylesterase activities). The geometric mean index of soil enzyme activity increased in the soils containing earthworms, regardless of the presence of valsartan. Therefore, earthworms increased soil carboxylesterase, dehydrogenase, alkaline phosphatase, β-glucosidase, urease and protease activities. Although bacterial richness significantly decreased following valsartan exposure, this trend was enhanced in the presence of earthworms with a significant impact on both alpha and beta microbial diversity. The operational taxonomic units involved in these changes were related to four (Proteobacteria, Bacteroidetes, Actinobacteria and Firmicutes) of the eight most abundant phyla. Their relative abundances significantly increased in the valsartan-treated soils containing earthworms, suggesting the presence of potential valsartan degraders. The ecotoxicological effect of valsartan on microbes was strongly altered in the earthworm-added soils, hence the importance of considering synergistic effects of different soil organisms in the environmental risk assessment of pharmaceutical active compounds.

Toluene is a highly flammable and commonly used industrial chemical with severe health consequences on humans upon exposure and ingestion. In this study, multispecies bioassays were conducted using a species sensitivity distribution approach to determine acute and chronic hazardous concentrations of toluene in soil. Acute and chronic toluene toxicity tests were conducted with seven soil species from four taxonomic groups. The results from the toxicity tests were used to estimate the acute and chronic HC₅ (hazardous concentration for 5 % of species) of toluene in the terrestrial environment at 58.9 (5.4–639.6) mg kg⁻¹ and 2.2 (0.2–19.8) mg kg⁻¹, respectively. To the best of our knowledge, this is the first study to estimate the hazardous concentration of toluene in soil by conducting a battery of bioassays. These values can be used as references for the environmental risk assessment of chemical accidents involving toluene and estimating its impact on soil to protect the terrestrial environment.

Evaluation of the toxicity of pesticide residues on non-target organisms in the ecosystem is an important part of pesticide environmental risk assessment. Flupyradifurone is a new type of butenolide insecticide produced by Bayer, who claims it to be “low toxic” to non-target organisms in the environment. However, there is little evidence in the literature to show how flupyradifurone affects aquatic organism development. In the current study, zebrafish embryos were treated with 0.1, 0.15, and 0.2 mg/mL of flupyradifurone within 6.0–72 h past fertilization (hpf). We found that the half-lethal concentration (LC₅₀) of flupyradifurone for zebrafish embryos at 96 hpf was 0.21 mg/mL. Flupyradifurone decreases the heart rate, survival rate, and body length of zebrafish embryos. The flupyradifurone treatment also led to the failure of heart looping, and pericardial edema. Moreover, flupyradifurone increased the level of reactive oxygen species (ROS) and decreased the enzymatic catalysis of catalase (CAT) and superoxide dismutase (SOD). Alterations were induced in the transcription of apoptosis-related genes (bcl-2, bax, bax/bcl-2, p53 and caspase-9) and the heart development-related genes (gata4, myh6, nkx2.5, nppa, tbx2b, tbx5 and vmhc). In the current study, new evidences have been provided regarding the toxic effects of flupyradifurone and the risk of its residues in agricultural products and the environment.

In many countries, including Morocco, groundwater contamination with pesticides such as globally banned organochlorides (e.g., dichlorodiphenyltrichloroethane (DDT)) and some accredited organophosphates and pyrethroids poses ecological and human health risks. To assess these risks, we herein monitored pesticides in Saïss plain groundwater (Morocco) during the summer of 2017 and the winter of 2018 using polar organic chemical integrative samplers. The two types of passive samplers were deployed in 22 traditional wells for 14–20 days and subjected to solid-phase extraction. The extracts were analyzed by gas chromatography-mass spectrometry and liquid chromatography-tandem mass spectrometry using a multiresidue method, and 27 pesticides were detected in total. In the summer campaign, 22 pesticides with individual concentrations ranging from <limit of quantitation (LOQ) to 243.1 ng L⁻¹ were identified, whereas 17 compounds with concentrations ranging from <LOQ to 53.8 ng L⁻¹ were detected in the winter campaign. In the summer period, the maximum individual concentrations of chlorothalonil, DDT, and α-hexachlorocyclohexane (α-HCH) equaled 111.7, 36.1, and 22.3 ng L⁻¹, respectively, with the respective values for the winter period equaling 18.14, 16.62, and 22.2 ng L⁻¹. Health risk assessment indicated that the carcinogenic α-HCH, β-HCH, DDT, and dichlorodiphenyldichloroethylene present in groundwater may also contaminate drinking water and thus pose a threat to human health, particularly to that of infants and children. Further analysis revealed that the Saïss aquifer presents a high ecological risk. Thus, the monitoring of pesticides in groundwater by passive sampling was effective and could be combined with human health and ecological risk assessment to develop ways of reducing human and environmental exposure to pesticides.

A large number of toxicity studies report abnormalities in early life-stage (ELS) fish that are described here as a sublethal toxicity syndrome (TxSnFELS) and generally include a reduced heart rate, edemas (yolk sac and cardiac), and a variety of morphological abnormalities. The TxSnFELS is very common and not diagnostic for any chemical or class of chemicals. This sublethal toxicity syndrome is mostly observed at high exposure concentrations and appears to be a baseline, non-specific toxicity response; however, it can also occur at low doses by specific action. Toxicity metrics for this syndrome generally occur at concentrations just below those causing mortality and have been reported for a large number of diverse chemicals. Predictions based on tissue concentrations or quantitative-structure activity relationship (QSAR) models support the designation of baseline toxicity for many of the tested chemicals, which is confirmed by observed values. Given the sheer number of disparate chemicals causing the TxSnFELS and correlation with QSAR derived partitioning; the only logical conclusion for these high-dose responses is baseline toxicity by nonspecific action and not a lock and key type receptor response. It is important to recognize that many chemicals can act both as baseline toxicants and specific acting toxicants likely via receptor interaction and it is not possible to predict those threshold doses from baseline toxicity. We should search out these specific low-dose responses for ecological risk assessment and not rely on high-concentration toxicity responses to guide environmental protection. The goal for toxicity assessment should not be to characterize toxic responses at baseline toxicity concentrations, but to evaluate chemicals for their most toxic potential. Additional aspects of this review evaluated the fish ELS teratogenic responses in relation to mammalian oral LD50s and explored potential key events responsible for baseline toxicity.

A monitoring network was established in streams within a catchment near the Costa Rican Pacific coast (2008–2011) to estimate the impact of pesticides in surface water (84 samples) and sediments (84 samples) in areas under the influence of melon and watermelon production. A total of 66 (water) and 47 (sediment) pesticides were analyzed, and an environmental risk assessment (ERA) was performed for four taxa (algae, Daphnia magna, fish and Chironomus riparius). One fungicide and seven insecticides were detected in water and/or sediment; the fungicide azoxystrobin (water) and the insecticide cypermethrin (sediments) were the most frequently detected pesticides. The insecticides endosulfan (5.76 μg/L) and cypermethrin (301 μg/kg) presented the highest concentrations in water and sediment, respectively. The ERA revealed acute risk in half of the sampling points of the melon-influenced area and in every sampling point from the watermelon-influenced area. Safety levels were exceeded within and around the crop fields, suggesting that agrochemical contamination was distributed along the catchment, with potential influence of nearby crops. Acute risk was caused by the insecticides chlorpyrifos, cypermethrin and endosulfan to D. magna, fish and C. riparius; the latter was the organism with the overall highest/continuous risk. High chronic risk was determined in all but one sampling point, and revealed a higher number of pesticides of concern. Cypermethrin was the only pesticide to pose chronic risk for all benchmark organisms. The results provide new information on the risk that tropical crops pose to aquatic ecosystems, and highlight the importance of including the analysis of sediment concentrations and chronic exposure in ERA.