Insecticide

Summary

Insecticides are pesticides used to kill insects. They include ovicides and larvicides used against insect eggs and larvae, respectively. Insecticides are used in agriculture, medicine, industry and by consumers. Insecticides are claimed to be a major factor behind the increase in the 20th-century's agricultural productivity. Nearly all insecticides have the potential to significantly alter ecosystems; many are toxic to humans and/or animals; some become concentrated as they spread along the food chain. Insecticides can be classified into two major groups: systemic insecticides, which have residual or long-term activity; and contact insecticides, which have no residual activity. The mode of action describes how the pesticide kills or inactivates a pest. It provides another way of classifying insecticides. Mode of action can be important in understanding whether an insecticide will be toxic to unrelated species, such as fish, birds and mammals. Insecticides may be repellent or non

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https://en.wikipedia.org/wiki/Insecticide

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In order to protect conifer logs against attacks from the striped ambrosia beetle (Trypodendron lineatum ) during spring in Swiss forests, logs are treated with the insecticide cypermethrin. Rainfall can cause the insecticide to leach into the ground, potentially threatening the groundwater quality. Forest groundwater is widely used for drinking water, which means that any contaminants within it should be avoided. This study assesses the risk of groundwater contamination in field conditions. The two study areas are located on unconsolidated sediments (Censie

res, or CS) and on karstic rocks (Grand Bochat, or GB). An analytical method was developed to determine the concentration of cypermethrin and its degradation products 3-PBA and DCVA in water samples. Intensive rainfall was simulated in order to mimic a situation that threatens groundwater. The study’s results show that, when treated according to the manufacturer’s instructions, a certain amount of insecticide was leached during the first rainfall event (2.2 g or 4.4 % of the applied cypermethrin). This leaching threatens groundwater quality, but can be avoided by decreasing the pesticide amount applied while maintaining a satisfactory protection. The insecticide amount that reached the groundwater was very low and was related to simulated rainfall, not natural rainfall. In Censie

res, only one groundwater sample presented a cypermethrin concentration (4 l g/l). In Grand Bochat, after a simulated rainfall of 36 mm, 3.3 % of the insecticide (5 g) was leached and 0.05 % of the total applied insecticide amount (corresponding to 1.5 % of the leached insecticide) reached the groundwater under the epikarst layer.

Springer2015

Biochemistry of Microbial Degradation of Hexachlorocyclohexane and Prospects for Bioremediation

Christof Holliger, Vishakha Raina

Lindane, the gamma-isomer of hexachlorocyclohexane (HCH), is a potent insecticide. Purified lindane or unpurified mixtures of this and alpha-, beta-, and gamma- isomers of HCH were widely used as commercial insecticides in the last half of the 20th century. Large dumps of unused HCH isomers now constitute a major hazard because of their long residence times in soil and high nontarget toxicities. The major pathway for the aerobic degradation of HCH isomers in soil is the Lin pathway, and variants of this pathway will degrade all four of the HCH isomers although only slowly. Sequence differences in the primary LinA and LinB enzymes in the pathway play a key role in determining their ability to degrade the different isomers. LinA is a dehydrochlorinase, but little is known of its biochemistry. LinB is a hydrolytic dechlorinase that has been heterologously expressed and crystallized, and there is some understanding of the sequence-structure-function relationships underlying its substrate specificity and kinetics, although there are also some significant anomalies. The kinetics of some LinB variants are reported to be slow even for their preferred isomers. It is important to develop a better understanding of the biochemistries of the LinA and LinB variants and to use that knowledge to build better variants, because field trials of some bioremediation strategies based on the Lin pathway have yielded promising results but would not yet achieve economic levels of remediation

2010

Picogram per liter detections of pyrethroids and organophosphates in surface waters using passive sampling

Juliane Hollender

Pyrethroids and organophosphates are among the most toxic insecticides for aquatic organisms, leading to annual-average environmental quality standards (AA-EQS) in the picogram per liter range in surface waters. For monitoring purposes, it is therefore crucial to develop very sensitive analytical methods. Until now, it is very difficult to reach detection limits at or below given AA-EQSs. Here, we present a passive sampling method using silicone rubber (SR) sheets for the sampling of ten pyrethroids and two organophosphates in surface waters. An analytical method was developed, optimized and validated for the extraction of the insecticides from the SR sheets by accelerated solvent extraction followed by clean-up on C18 and silica gel and detection with GC-MS/MS in positive ionization mode. Good precision (50%) was observed for all substances, accuracy was between 66% and 139%. Limits of detection between 6 and 200 pg/L were achieved for all substances in surface waters using average sampling rates for PCBs and PAHs. The lack of substance-specific sampling rates and missing performance reference compounds led to an uncertainty in the concentration estimation of factor three in both directions. In a large field study, comprising 40 environmental samples from nine Swiss rivers, eight out of 12 substances were detected (most frequently: chlorpyrifos, cypermethrin). Most of the estimated organophosphate concentrations were between 0.1 and 1 ng/L, most pyrethroid detections below 0.1 ng/L. Four substances (chlorpyrifos-methyl, cypermethrin, deltamethrin and lambda-cyhalothrin) showed exceedances of their respective AA-EQS in multiple samples, also when the uncertainties in the concentration estimation were considered. As pyrethroid and organophosphate detection by SR passive sampling is very practicable and allows sensitive analysis, it has the potential to become a new tool in the monitoring of non-polar pesticides. (C) 2014 Elsevier Ltd. All rights reserved.

Elsevier2014

Picogram per liter detections of pyrethroids and organophosphates in surface waters using passive sampling

Juliane Hollender

Elsevier2014