Environmental Monitoring and Potential Health Risk Assessment from Pymetrozine Exposure among Communities in Typical Rice–Growing Areas of China

Pymetrozine is one of the most common insecticides used in China. This study was conducted to analyse Pymetrozine’s potential exposures through various environmental routes beyond the treatment area. The aim was to estimate the potential health risk for communities due to non-dietary exposure to Pymetrozine in soil and paddy water. Data on registration of pesticides in China, government reports, questionnaires, interviews, literature reviews as well as toxicological health investigations were evaluated to determine the hazard and dose-response characteristics of Pymetrozine. These were based on the US EPA exposure and human health risk assessment methods using exposure from soil and paddy water samples collected between 10 to 20 meters around the resident’s location.The potential exposures from dermal contact through soil and paddy water were estimated. The potential cancer risk from the following routes was evaluated: the ingestion through soil; dermal contact exposure through soil; dermal contact exposure through paddy water; and the potential total cancer risk for residents was less than 1*10− 6. These were within the acceptable risk levels. The potential hazard quotient (HQ) from acute and lifetime exposure by dermal contact through paddy water and soil; acute and lifetime exposure by soil ingestion for residents were less than 1, indicating an acceptable risk level, thus both potential cancer risk and hazard quotient (HQ) were relatively low. Potential human health risk assessment of Pymetrozine in soil and paddy water suggested that negligible cancer risk and non-cancer risk based on ingestion and dermal contact are the main potential routes of exposure to residents.

Off-site movement of quinclorac from rice fields

Highlights - Quinclorac persistence in paddy water is affected by its residues in entering waters. - Entering waters often contain quinclorac residues. - A water holding period of at least 10 days may limit the offsite movement of quinclorac residues from paddy fields. Abstract The off-site movement of quinclorac from rice paddies was studied in a district and field study during the 2014 and 2015 growing seasons. Quinclorac residues were monitored on in-field surface waters, and out-field water entering and leaving an irrigation district. The behavior of quinclorac residues in paddy water pointed out that the movement of herbicides from interconnected paddies is not negligible. This phenomenon was particularly evident in the days following the re-flooding of paddies after spraying. The water entering the uphill paddy fields have partially flushed quinclorac residues in the downhill paddy fields. Both the district and the field studies, showed the continuous presence of quinclorac residues in inlet waters. Even because of the continuous uploading of residues from inlet waters, traces of quinclorac in paddy water were detected up to 70 DAT. The presence of quinclorac in inlet water could be related to phenomena of drainage and drift during herbicide application in the paddies located upstream. The analysis carried out on waters leaving the district showed the presence of quinclorac residues in all the outlet floodgates, particularly from the end of May and late August. The results of this study suggest that appropriate management practices adopted at field scale may be required to lower the water contamination at irrigation district level. Considering that the highest losses of quinclorac occurred during the first 10-15 days after its application, to prevent these losses could be helpful avoiding water discharge from the treated fields for at least this period of time. In addition, a deep effort must be laid upon education and training of farmers on these environmental thematic throughout specific initiatives organized by public and private stakeholders.

Studies on Dissipations and Residues of Indoxacarb under Different Field and Environmental Conditions

Indoxacarb is a broad-spectrum insecticide and widely used in agriculture. The dissipations and residues of indoxacarb were researched at three different field sites in Beijing, Hunan, and Zhejiang provinces in China. Analytical methods for determining the residue of indoxacarb in paddy water, paddy soil, rice straw, rice hull, and brown rice were described. Indoxacarb residues were extracted from samples, cleaned up by solid phase extraction, and determined by high-performance liquid chromatography coupled with tandem mass spectrometry in the selected ion monitoring mode. The recoveries in paddy water, paddy soil, rice straw, rice hull, and brown rice matrices at three spiking levels ranged from 79.7% to 98.3%, respectively. The field and environmental conditions would affect the dissipations and residues of indoxacarb. The time to dissipate 50% of indoxacarb in paddy water, paddy soil, and rice straw was less than 9 days. The terminal residues obtained from Beijing at preharvest interval of 14 and 21 days were higher than the maximum limit of European Union. Therefore, a dosage of 24 g a. i. ha−1 at 28 days preharvest interval with 3 spraying times was recommended. Such accumulation of measured data is necessary to provide guidance for the proper and safe use of this pesticide.

Qualitative and Quantitative Analysis of the New Sulfone Bactericide 2-(4-Fluorophenyl)-5-(Methylsulfonyl)-1,3,4-Oxadiazole and Identification of Its Degradation Pathways in Paddy Water

Rapid and simple methods for the determination of Jiahuangxianjunzuo (JHXJZ) in paddy water, brown rice, soil and rice straw was developed and validated. This method involved the use of ultrahigh-performance liquid chromatography equipped with photodiode array detector. The most important factor was chromatographic conditions, as identified through an orthogonal experimental design. This method showed good recoveries and precisions, thereby indicating its suitability for monitoring of JHXJZ residues in paddy water, brown rice, soil and rice straw. Furthermore, hydrolysis experiment was conducted in the laboratory under pH = 7 buffer solutions, and its degradation product was identified as 2-(4-fluorophenyl)-5-methoxy-1,3,4-oxadiazole by high-resolution mass spectrometry. JHXJZ has a major degradation pathway in the water which the OH− nucleophilic attack the C5 of 1,3,4-oxadiazole ring. Then it leaves mesyl to form intermediate 5-(4-fluorophenyl)-1,3,4-oxadiazol-2-ol and the intermediate combined with methanol formed the degradation product 2-(4-fluorophenyl)-5-methoxy-1,3,4-oxadiazole by the loss of one H2O.The degradation pathways of JHXJZ under the present indoor simulation conditions were proposed.

Correction: Kamruzzaman, M., et al. Evaluating the Impact of Climate Change on Paddy Water Balance Using APEX-Paddy Model. Water 2020, 12, 852

The authors wish to make the following corrections to this paper [...]