Spatio-temporal distribution of perchlorate and its toxicity in Hydrilla verticillata

Proposing Effective Ecotoxicity Test Species for Chemical Safety Assessment in East Asia: A Review

East Asia leads the global chemical industry, but environmental chemical risk in these countries is an emerging concern. Despite this, only a few native species that are representative of East Asian environments are listed as test species in international guidelines compared with those native to Europe and America. This review suggests that Zacco platypus, Misgurnus anguillicaudatus, Hydrilla verticillata, Neocaridina denticulata spp., and Scenedesmus obliquus, all resident to East Asia, are promising test species for ecotoxicity tests. The utility of these five species in environmental risk assessment (ERA) varies depending on their individual traits and the state of ecotoxicity research, indicating a need for different applications of each species according to ERA objectives. Furthermore, the traits of these five species can complement each other when assessing chemical effects under diverse exposure scenarios, suggesting they can form a versatile battery for ERA. This review also analyzes recent trends in ecotoxicity studies and proposes emerging research issues, such as the application of alternative test methods, comparative studies using model species, the identification of specific markers for test species, and performance of toxicity tests under environmentally relevant conditions. The information provided on the utility of the five species and alternative issues in toxicity tests could assist in selecting test species suited to study objectives for more effective ERA.

Combined effects of perchlorate and hexavalent chromium on the survival, growth and reproduction of Daphnia carinata

Perchlorate and hexavalent chromium (Cr(VI)) are common cocontaminants in aquatic environments due to their high water solubility, stability, mobility, and some coapplications. However, few studies have investigated their combined toxicity to organisms. In this work, we studied the acute and chronic toxicities of perchlorate and Cr(VI), alone and in combination, with survival, growth, and reproduction as endpoints using Daphnia carinata as a model organism. For a single contaminant, Cr(VI) was found to be more toxic than perchlorate to D. carinata not only in terms of survival but also in terms of growth and reproduction. In regard to the combined pattern, the interactive effects on survival, growth, and reproduction were mainly additivity, antagonism, and synergism, respectively, suggesting that the interactive response of perchlorate and Cr(VI) is endpoint-specific. Due to significant synergism, over 21 days of observation, the inhibition of 0.1 mg/L perchlorate and 0.2 mg/L Cr(VI) on cumulative offspring per female in the first seven broods reached 63.9 ± 3.6%, suggesting that long-term exposure to perchlorate and Cr(VI) at environmentally relevant concentrations may affect D. carinata reproduction in the natural environment. Our results will be significant for understanding the complicated combined toxicity of perchlorate and Cr to aquatic organisms.

One-step sample processing method for the determination of perchlorate in human urine, whole blood and breast milk using liquid chromatography tandem mass spectrometry

A one-step sample processing was developed to determine the levels of perchlorate in human urine, whole blood and breast milk by using liquid chromatography tandem mass spectrometry (LC-MS/MS). Athena C18-WP column was used to separate and analyze perchlorate. Perchlorate and isotope-labeled perchlorate (Cl¹⁸O₄^-) internal standards were spiked in the sample matrix through vortex mixing, centrifugation, and filtration. The filtrate was collected and subjected to LC analysis. The developed method was validated for its reproducibility, linearity, trueness, and recovery. Satisfactory recovery of perchlorate ranged from 81% to 117% with intraday relative standard deviations (RSDs) (n = 3) and inter-day RSDs (n = 9) of 5-18% and of 5-16%, respectively. Good linearity (R² ≥ 0.99) was observed. Limits of detection and quantification for perchlorate ranged from 0.06 µg/L to 0.3 µg/L and from 0.2 µg/L to 1 µg/L, respectively. Perchlorate concentrations were found in human urine (n = 38) and whole blood (n = 8) samples with the range of 6.5-288.6 µg/L and 0.3-2.8 µg/L, respectively. These results indicate the applicability of our developed method in determining perchlorate level in real samples. Moreover, this method is also highly reliable, sensitive and selective in detecting perchlorate in human urine, whole blood and breast milk samples and may be applicable to other matrixes i.e. saliva, serum, plasma, milk powder and dairy milk.

Toxicity evaluation and environmental risk assessment of 2-methyl-4-chlorophenoxy acetic acid (MCPA) on non-target aquatic macrophyte Hydrilla verticillata

Aquatic plants in agricultural landscapes play a vital role in maintaining the ecological integrity within the aquatic systems while facing an array of disturbances. Among them, information on herbicide exposure on non-target aquatic plants is scarce. The present study was designed to fill this information gap by detecting the impacts of 2-methyl-4-chlorophenoxyacetic acid (MCPA) on Hydrilla verticillata using morpho-anatomical and physiological biomarkers and assessing the environmental risk of MCPA to the non-target environment. H. verticillata was exposed to different MCPA concentrations (10, 100, 500, 1000 μg/L) and control (0 μg/L) for 7 days. At the end of the experiment, plant growth, pigments, H₂O₂ content, peroxidase activity (POD) and plant anatomy were compared. The environmental risk was assessed using predicted environmental concentration/predicted no effect concentration (PEC:PNEC) ratio, hazard quotient (HQ) and hazard index (HI). Control plants exhibited the highest growth, and a growth decline was noted in parallel to MCPA exposure, where a similar trend was detected for the plant pigment contents. MCPA induced chlorosis and oxidative stress in H. verticillata. Risk analysis detected high values for PEC:PNEC ratios (3-9), HQ (1.92-5.79) and HI (28.15). MCPA-exposed H. verticillata could recover once those plants received natural conditions. Overall, present findings showed the negative impacts of MCPA on non-target aquatic plant H. verticillata. These findings will be useful to clarify the interaction between agrochemicals and non-target aquatic plants. Such information would benefit to decide the criteria in aquatic ecosystem management.