Environmental carrying capacity and ecological risk assessment of pesticides under different soil use types in the Central Plains Urban Agglomeration (CPUA), China

Soil environmental safety has received much attention during the past few decades due to its significance in agricultural production and human health. Special attention is required for soil pesticide residues and ecological risks. This study examined 197 soil samples from industrial, residential and agricultural areas for the presence of 12 organophosphorus pesticides (OPPs) and 8 synthetic pyrethroids (SYPs) in the 16 cities in Henan Province, and the center of CPUA, based on the Central Plains Urban Agglomeration (CPUA) concept proposed by China. The total average concentrations of ∑12OPPs in industrial, residential and agricultural soils were 194, 217, 267 ng/g dry weight, and those of ∑8SYPs were 26.8, 35.7, 25.5 ng/g dry weight, respectively. The two pollutants with the greatest concentrations in the soils were malathion and fenpropathrin, respectively, the dominant components of OPPs and SYPs. The soil environmental carrying capacity (SECC) analysis, representing the maximum residual load that can be supported, shows that acephate and cyhalothrin were overloaded, with a predicted period of over 500 years. Among the 16 cities of CPUA, a higher frequency of high ecological risk could be observed only in Shangqiu. The OPPs in children had total non-carcinogenic risk values of more than 1.0. Similarly, the non-carcinogenic risks of SYPs in adults and children in the residential areas were more than 1.0. The study provides knowledge on how to effectively manage soil safety in Henan Province, which is the center of the CPUA, with a large population and grain province to protect ecosystems and reduce the risks of soil pesticide residues in humans.

The protective effects of the Lactarius deliciosus and Agrocybe cylindracea mushrooms on histopathology of carbon tetrachloride induced oxidative stress in rats

We investigated the protective effects of L. deliciosus and A. cylindracea supplementation against carbon tetrachloride (CCI₄) induced oxidative stress by measuring levels of adenosine deaminase (ADA) and myeloperoxidase (MPO), and by observing histopathological changes in liver and kidney tissues of rats. We divided 36 rats into six groups: control, CCl₄, L. deliciosus, A. cylindracea, CCl₄ + L. deliciosus, and CCl₄ + A. cylindracea. We found that administration of CCI₄, A. cylindracea, and CCl₄ + A. cylindracea increased MPO and ADA levels. We observed severe hepato-renal degenerative and necrotic lesions in the CCI₄, A. cylindracea and CCl₄ + A. cylindracea groups. Severe lesions of the liver and kidney were not observed with A. cylindracea administration. CCI₄ induced hepato-renal lesions were ameliorated by L. deliciosus extract supplementation. L. deliciosus could be an important dietary antioxidant for preventing histologic lesions in liver and kidney due to CCI₄ induced oxidative stress in rats.

Comparative Toxicity of Two Different Dimethoate Formulations in the Common Toad (Rhinella arenarum) Tadpoles

Dimethoate (D) are among the most commonly used organophosphates insecticides in the world. To evaluate the toxicity of two D formulations were selected as test organisms tadpoles of Rhinella arenarum. This toad species has an extensive neotropical distribution and is easy to handle and acclimate to laboratory conditions. The tadpoles were exposed in an acute assay for 48 h to D soluble concentrates (DSC) and emulsifiable concentrates (DEC). The 48 h-LC₅₀ (95% confidence limits) value of DSC was 57.46 mg L^-1 (40.52-81.43) and to DEC was 12.76 mg L^-1 (10.39-15.68). These differences in toxicity were statistically significant (p < 0.05). In both formulations, acetylcholinesterase), carboxylesterase, and glutathione-S-transferases enzyme activities varied significantly respect to those of control group (p < 0.05). The DEC formulation was the most toxic. These results would allow the assessment and characterization of potential ecological risks following the application of those formulations.

Evaluation of an acute oral gavage method for assessment of pesticide toxicity in terrestrial amphibians

Development of an acute oral toxicity test with a terrestrial-phase amphibian was considered necessary to remove the uncertainty within the field of agrochemical risk assessments. The bullfrog (Lithobates catesbeianus) was selected for use as it is a representative of the family Ranidae and historically this species has been used as an amphibian test model species. Prior to definitive study, oral gavage methods were developed with fenthion and tetraethyl pyrophosphate. Dimethoate and malathion were subsequently tested with both male and female juvenile bullfrogs in comprehensive acute oral median lethal dose (LD50) studies. Juvenile bullfrogs were administered a single dose of the test article via oral gavage of a single gelatin capsule of dimethoate technical (dimethoate) or neat liquid Fyfanon^® Technical (synonym malathion), returned to their respective aquaria, and monitored for survival for 14 d. The primary endpoint was mortality, whereas behavioral responses, food consumption, body weight, and snout-vent length (SVL) were used to evaluate indications of sublethal toxicity (secondary endpoints). Acute oral LD50 values (95% fiducial interval) for dimethoate were 1459 (1176-1810, males) and 1528 (1275-1831, females), and for malathion they were 1829 (1480-2259, males) and 1672 (1280-2183, females) mg active substance/kg body weight, respectively. Based on the results of these studies, the methodology for the acute oral gavage administration of test items to terrestrial-phase amphibians was demonstrated as being a practical method of providing data for risk assessments. Environ Toxicol Chem 2018;37:436-450. © 2017 SETAC.

The effect of long-term corticosterone treatment on blood cell differentials and function in laboratory and wild-caught amphibian models

The effect of long-term stress on amphibian immunity is not well understood. We modeled a long-term endocrine stress scenario by elevating plasma corticosterone in two species of amphibians and examined effects on white blood cell differentials and innate immune activity. Plasma corticosterone was elevated in American bullfrogs (Lithobates catesbeianus) by surgically implanting corticosterone capsules and in African clawed frogs (Xenopus laevis) by immersion in corticosterone-treated water. To provide a context for our results within endogenous corticosterone fluctuations, diurnal plasma corticosterone cycles were determined. A daily low of corticosterone was observed in X. laevis at 12:00, while a significant pattern was not observed in L. catesbeianus. Elevated plasma corticosterone levels increased the ratio of peripheral neutrophils to lymphocytes, in both species, and decreased eosinophil concentrations in L. catesbeianus over a long-term period. Whole blood oxidative burst generally correlated with neutrophil concentrations, and thus was increased with corticosterone treatment, significantly in L. catesbeianus. In L. catesbeianus, an endogenous response of eosinophils and lymphocytes to implanted empty (sham) capsules was observed, but this effect was attenuated by corticosterone. Peripheral monocyte and basophil concentrations were not significantly altered by corticosterone treatment in either species. Our results show that long-term stress can alter amphibian immune parameters for extended periods and may play a role in susceptibility to disease.

Acute effects of fenthion on certain oxidative stress biomarkers in various tissues of frogs (Rana ridibunda)

This study was aimed mainly to assess the effects of fenthion on certain oxidative stress biomarkers in various tissues of frogs ( Rana ridibunda). Biomarkers selected for stress monitoring were malondialdehyde (MDA) and antioxidant defense system (ADS) such as reduced glutathione (GSH) level, glutathione peroxidase (GSH-Px), glutathione- S-transferase (GST), and superoxide dismutase (SOD) activities in the liver, kidney, heart, and brain of frogs exposed to 10 and 20 ppm dosages of fenthion for 24, 48, 72, and 96 h. The results demonstrate an increase in MDA levels in selected tissues following exposure to both concentrations of fenthion. The ADS, GSH-Px, GST, SOD activities and GSH levels also fluctuated after 24, 48, 72, and 96 h in all the treatment groups compared with controls. From the evidence obtained here, it is concluded that the exposure of frogs to fenthion induced an increase in MDA combined with fluctuated ADS. This may reflect the potential role of these parameters as useful biomarkers for oxidative stress in amphibian species.