Liquid chromatography-mass spectrometry method for evaluating the dissipation dynamics of cyromazine and its metabolite in Agaricus bisporus and dietary risk assessment

Dissipation, Bioconcentration and Dietary Risk Assessment of Thiamethoxam and Its Metabolites in Agaricus bisporus and Substrates under Different Application Methods

In order to acquire scientific evidence for the application of thiamethoxam (TMX) in Agaricus bisporus cultivation, residue and dissipation experiments for field trials were performed with the application of TMX in compost and casing soil, respectively. An effective QuEChERS method was established to analyze TMX and its two metabolites, clothianidin (CLO) and thiamethoxam-urea (TMX-urea), in compost, casing soil, and fruiting bodies. The results indicated that the TMX dissipation half-lives (t_1/2) at dosages of 10 and 50 mg kg^-1 were 19.74 d (day) and 28.87 d in compost and 33.54 d and 42.59 d in casing soil, individually. TMX, CLO, and TMX-urea were observed after TMX application in compost and casing soil. For TMX applied to the casing soil, only TMX residues were detected in fruiting bodies with bioconcentration factors (BCFs) of 0.0003~0.0009. In addition, both the chronic risk quotient (RQ) and acute risk quotient (HQ) values of TMX in fruiting bodies were far less than 1, which means the dietary health risks to humans were acceptable. However, in the TMX application to the compost, these analytes were not detected in the fruiting bodies. This suggested that the application of TMX in compost was safer than in casing soil during A. bisporus cultivation.

Isolation and characterization of cyromazine degrading Acinetobacter sp. ZX01 from a Chinese ginger cultivated soil

Cyromazine, a symmetrical triazine insecticide, is used to control dipteran larvae in chicken manure by feeding to the poultry, flies on animals, and leafminers in vegetables. Its extensive use has resulted in the widespread contamination in the environment. In the current study, a cyromazine degrading bacterium (designated strain ZX01) was isolated and characterized from a Chinese ginger cultivated soil by selective enrichment culture method. On the basis of morphological, biochemical characteristics, and 16S rRNA gene sequence, this bacterium showed strong similarity to the Pseudomonadales members and was closely related to the Acinetobacter baumannii group. Spectrophotometric and HPLC analyses revealed that strain ZX01 degraded cyromazine and utilized it as the sole carbon source for its growth. This process hydrolyzes cyromazine to melamine. Strain ZX01 degraded most of the cyromazine in 60 h. Besides, its substrate specificity against four symmetrical triazine herbicides, one triazinone herbicide, as well as 10 insecticides and its antibiotic sensitivity towards eight commercial antibiotics were also tested. At the concentration of 100 µg/mL for 60 h, it could effectively degrade a variety of different pesticides, including atrazine, prometon, simazine, prometryn, enitrothion, diazinon, cypermethrin, and acetamiprid, and the degradation was in the range of 71-87%. In particular, melamine, the main degradation product of cyromazine, was degraded by 47.3%. This microorganism was sensitive to chloramphenicol and tetracycline and intermediate to amoxicillin and trimethoprim. These results highlight that strain ZX01 can be used as a potential biological agent for the remediation of soil, water, or crop contaminated with cyromazine and other symmetrical triazine insecticides.

Imidacloprid dissipation, metabolism and accumulation in Agaricus bisporus fruits, casing soil and compost and dietary risk assessment

An improved understanding of imidacloprid (IMI) metabolism and accumulation in casing soil or compost-mushroom systems will help to optimise the safe use of IMI for agricultural pest control in Agaricus bisporus cultivation. In this study, the dissipation, metabolites and accumulation of IMI in casing soil or compost-A. bisporus systems were investigated. The results show that the IMI dissipation half-lives at doses of 10 and 50 mg kg^-1 were 65 d and 59 d in casing soil and 6.6 d and 6.2 d in compost, respectively during the cultivation period. Three IMI metabolites were observed in casing soil during cultivation of mushrooms. Urea-imidacloprid (IMI-urea) was a major metabolite, accounting for more than 59%. In compost, the main metabolite in the first 5 days was IMI-urea, from 5 to 10 days olefin-imidacloprid (IMI-ole) and 6-chloronicotinic acid (6-CNA) were both the most prominent compounds, and after 10 days 6-CNA alone. At 50 mg kg^-1 dose, IMI and the metabolites (IMI-urea, IMI-ole) were detected in the fruiting body with IMI applied to casing soil and only the metabolite 6-CNA was detected in fruiting body with IMI applied to compost. The bio concentration factors (BCFs) of IMI-ole and IMI-urea were higher than of IMI and 6-CNA, and the BCFs had no obvious relationship with log K_ow. Furthermore, the potential dietary risk of IMI in A. bisporus was acceptable when application rates in casing soil or compost was up to 50 mg kg^-1. Our study supports a safe use of IMI as agricultural pest control in A. bisporus cultivation.

Metabolism, Distribution, and Excretion of Ethanamizuril in Chickens

Ethanamizuril(N-{4-[4-(3,5-dioxo-4,5-dihydro-3H-[1,2,4]triazin-2-yl)-2-methyl-phenoxy]-phenyl}-acetamide, EZL) is a new anticoccidiosis compound and belongs to the class of triazines. In this study, the metabolism, distribution, and excretion of EZL were evaluated in chickens after administration of EZL at a single dosage. According to the relevant drug biotransformation rules, the exact molecular mass detection, the fragmentation characteristics, and the retention times, a total of five metabolites were identified in vivo in chickens, including two phase I metabolites and three phase II conjugated metabolites. The major metabolic pathways of EZL in chickens were deacetylation, hydroxylation, and glucuronidation. Regarding ¹⁴C-tissue residues after administration, kidney was considered to be the target tissue, as ¹⁴C-tissue residues could be detected at 240 h postdose. DeacetylEZL (M3) was the main metabolite, accounting for 68.65% and 25.62% of ¹⁴C in kidney at 6 and 24 h, respectively. In heart, muscle, skin+fat, and lung tissues, EZL was the main radioactive substance accounting for 94.88%, 97.32%, 96.23%, and 91.3% of ¹⁴C, respectively. In the liver, EZL and M3 were 20.76% and 54.65% of ¹⁴C, respectively. In chicken tissues the ratio of M5 was too low to be quantitated and it was mainly detected in chicken fecal and bile samples. In chicken excreta, EZL, M3, and glucuronidation of EZL (M5) accounted for 7.02%, 12.33%, and 10.32% of the dose, respectively and were eliminated primarily. This study presents the first detection of EZL metabolites, which is helpful for further understanding of the metabolic mechanism and in vivo intermediate processes of EZL. The results of this study will be good bases for better understanding EZL's anticoccidiosis mechanism and will serve as a helpful reference for assessing the risks to animals and humans.

An assessment of melamine exposure in Shanghai adults and its association with food consumption

Melamine is widely used to make household products including plates, cups, and large-scale industrial plastic products. Studies have shown the nephrotoxicity of melamine. However, little is known about urinary melamine concentration in adults and its association with the consumption of foods, other than milk products. In this study, we measured the urinary melamine concentration of 908 Shanghai adults and calculated the estimated daily intake (EDI) and hazard quotient accordingly. We also used a 24 h (24-hr) recall survey to identify possible risk foods associated with melamine exposure. Melamine was detectable in over 85% of the urine samples and had a median concentration of 2.524 μg/g. There were 22 participants who had EDIs exceeding the tolerable daily intake (TDI) of 3150 ng/kg bw/day, the strictest reference dose in administration by far. Melamine concentration in urine was positively associated with the 24-hr recall consumption of rice, fruits, beef, mutton, processed meats, and eggs, but no other food categories. Our study provides evidence-based data on the melamine exposure level in adults from Shanghai, China, and some possible associations with food intake.

Tailor-Made Specific Recognition of Cyromazine Pesticide Integrated in a Potentiometric Strip Cell for Environmental and Food Analysis

Screen-printed ion-selective electrodes were designed and characterized for the assessment of cyromazine (CYR) pesticide. A novel approach is to design tailor-made specific recognition sites in polymeric membranes using molecularly imprinted polymers for cyromazine (CR) determination (sensor I). Another sensor (sensor II) is the plasticized PVC membrane incorporating cyromazine/tetraphenyl borate ion association complex. The charge-transfer resistance and water layer reached its minimal by incorporating Polyaniline (PANI) solid-contact ISE. The designed electrodes demonstrated Nernstain response over a linear range 1.0 × 10-2-5.2 × 10-6 and 1.0 × 10-2-5.7 × 10-5 M with a detection limit 2.2 × 10-6 and 8.1 × 10-6 M for sensors I and II, respectively. The obtained slopes were 28.1 ± 2.1 (r2 = 0.9999) and 36.4 ± 1.6 (r2 = 0.9991) mV/decade, respectively. The results showed that the proposed electrodes have a fast and stable response, good reproducibility, and applicability for direct measurement of CYR content in commercial pesticide preparations and soil samples sprayed with CYR pesticide. The results obtained from the proposed method are fairly in accordance with those using the standard official method.