Latest Research News on Chlorpyrifos: Dec 2020
Chlorpyrifos: Pharmacokinetics in human volunteers
The kinetics of chlorpyrifos, an organophosphorothioate insecticide, and its principal metabolite, 3,5,6-trichloro-2-pyridinol (3,5,6-TCP), were investigated in six healthy male volunteers given a single 0.5 mg/kg po and, 2 or more weeks later, a 0.5 or 5.0 mg/kg dermal dose of chlorpyrifos. No signs or symptoms of toxicity or changes in erythrocyte cholinesterase were observed. Plasma cholinesterase was depressed to 15% of predose levels by the 0.5 mg/kg po dose but was essentially unchanged following the 5.0 mg/kg dermal dose. Blood chlorpyrifos concentrations were extremely low (<30 ng/ml), and no unchanged chlorpyrifos was found in the urine following either route of administration. Mean blood 3,5,6-TCP concentrations peaked at 0.93 μg/ml 6 hr after ingestion of the oral dose and at 0.063 μg/ml 24 hr after the 5.0 mg/kg dermal dose. 3,5,6-TCP was cleared from the blood and eliminated in the urine with a half-life of 27 hr following both the po and dermal doses. An average of 70% of the po dose but less than 3% of the dermal dose was excreted in the urine as 3,5,6-TCP; thus only a small fraction of the dermally applied chlorpyrifos was absorbed. Chlorpyrifos and its principal metabolite were rapidly eliminated and therefore have a low potential to accumulate in man on repeated exposures. Based on these data, bood and/or urinary 3,5,6-TCP concentrations could be used to quantify the amount of chlorpyrifos absorbed under actual use conditions. 
Effects of Soil pH on the Biodegradation of Chlorpyrifos and Isolation of a Chlorpyrifos-Degrading Bacterium
We examined the role of microorganisms in the degradation of the organophosphate insecticide chlorpyrifos in soils from the United Kingdom and Australia. The kinetics of degradation in five United Kingdom soils varying in pH from 4.7 to 8.4 suggested that dissipation of chlorpyrifos was mediated by the cometabolic activities of the soil microorganisms. Repeated application of chlorpyrifos to these soils did not result in the development of a microbial population with an enhanced ability to degrade the pesticide. A robust bacterial population that utilized chlorpyrifos as a source of carbon was detected in an Australian soil. The enhanced ability to degrade chlorpyrifos in the Australian soil was successfully transferred to the five United Kingdom soils. Only soils with a pH of ≥6.7 were able to maintain this degrading ability 90 days after inoculation. Transfer and proliferation of degrading microorganisms from the Australian soil to the United Kingdom soils was monitored by molecular fingerprinting of bacterial 16S rRNA genes by PCR-denaturing gradient gel electrophoresis (DGGE). Two bands were found to be associated with enhanced degradation of chlorpyrifos. Band 1 had sequence similarity to enterics and their relatives, while band 2 had sequence similarity to strains of Pseudomonas. Liquid enrichment culture using the Australian soil as the source of the inoculum led to the isolation of a chlorpyrifos-degrading bacterium. This strain had a 16S rRNA gene with a sequence identical to that of band 1 in the DGGE profile of the Australian soil. DNA probing indicated that genes similar to known organophosphate-degrading (opd) genes were present in the United Kingdom soils. However, no DNA hybridization signal was detected for the Australian soil or the isolated degrader. This indicates that unrelated genes were present in both the Australian soil and the chlorpyrifos-degrading isolate. These results are consistent with our observations that degradation of chlorpyrifos in these systems was unusual, as it was growth linked and involved complete mineralization. As the 16S rRNA gene of the isolate matched a visible DGGE band from the Australian soil, the isolate is likely to be both prominent and involved in the degradation of chlorpyrifos in this soil. 
Ecotoxicology of Chlorpyrifos
The manufacture and use of organochlorine insecticides in the United States decreased dramatically during the 1970s, in part because of their adverse effects on fish and wildlife and the tendency of these compounds to bioaccumulate. Organochlorine insecticides used in agriculture were replaced by the organophosphorothioate and pyrethroid insecticides, which possessed a comparable spectrum of insecticidal activity but were far less persistent in terrestrial and aquatic environments. 
Effect of Dimethoate and Chlorpyrifos in Hepatic and Renal Function of People Belonging to Risk Groups in Iraklia Serres (N. Greece)
Aims: There is little evidence concerning the effects of organophosphates in the liver of healthy individuals, and the existing researches come to contradictive results. In this study, we evaluated the influence of organophosphates (Dimethoate, Chlorpyrifos) in liver and renal function of healthy exposed workers, not experiencing symptoms of serious intoxication.
Study Design: Measure serum activity of the liver function monitoring enzymes SGPT, SGOT, γ-GT and ALP and serum concentration of the renal function indicative biomarkers urea and creatinine.
Place and Duration of Study: Sample were collected in Health Care Greece of Iraklia Serres and analyzed in Department of Medical Laboratory Studies Alexander Technological Educational Institute of Thessaloniki.
Methodology: Blood samples were collected from 112 individuals, randomly selected from villagers of N. Greece. 42 of them were organophosphates (OP) applicators aged less than 50 years old (mean age 37 years old) and 42 were OP applicators older than 50 years old (mean age 58 years old); while 28 individuals (13 of them were less than 50 years old and 15 older than 50 years) were not OP applicators and used as control groups.
Results: A remarkable and statistically significant increase (P < 0.05) in the main liver-function monitoring enzymes (SGOT, SGPT, γ-GT) was observed in exposed people compared to the control group. Increase in ALP values compared to not exposed individuals was not observed. Concerning the kidneys, data analysis shows that there is not any significant effect on their operation by the use of OP.
Conclusion: The age of OP applicators and the time past between the application and the measure of blood serum seems to play an important role in the values of hepatic enzymes. While the renal indicators seemed not so much affected, as organophosphates are rapidly metabolized in human organism. 
Histopathological Changes Associated with Exposure of Male Mice to Profenofos and Chlorpyrifos
Aims: The histopathological effects of Profenofos, and Chlorpyrifos, as synthetic organophosphorus pesticides, on the liver, kidney, brain and spleen tissues in mice (Mus musculus) were determined by light microscopy. Recently the toxic effects of pesticides have been of public interest. The usage of pesticides is still the most effective and accepted means to protect plants from the pests and to increases productivity. The misuse of pesticides is connected with serious problems of pollution and health hazards. Profenofos and Chlorpyrifos is used widely in Egypt and they play a vital role in controlling Lepidopteron pests of cotton and vegetables .
Study Design: Mice were treated with Profenofos, and Chlorpyrifos sub-lethal concentrations (1/10, 1/40 and ADI LD50) orally to twice a week for 30, 60, and 90 consecutive days.
Place and Duration of Study: Department of chemistry Faculty of Agriculture, Cairo University, Egypt, between June 2012 and January 2013.
Results: Histopathological examination revealed various abnormalities in liver tissues, such as congestion of blood vessels, vacuolar degeneration of hepatic cells, focal infiltration and mononuclear cells, Moreover, all central veins and other hepatic blood vessels were dilated, some hepatic cells showed necrosis, disorganization with the formation of a denoid structure and some areas showed hepatocytomegaly with the increase of the number of cells showing double nuclei. Pathological finding in kidney showed perivascular edema with congestion of renal blood vessels, infiltration of mononuclear cells and around some of glomerular tubules, edema of Bowman’s capsule and some renal tubules showed coagulation necrosis. Pathological finding in spleen showed disorganization of lymphocytes in lymphoid follicles and in white pulp, depletion of lymphocyts with sub capsular edema, and other cases showed increasing the number of megaterocytes with hemorrhages and haemosiderosis. Pathological finding in Brain showed menengial hemorrhages and congestion of blood vessels, with neuronophagia and satelletosis and sub meningial encephalomalacia, with neuronal degeneration of purkinjie cells were noticed and lesions, there was lyses of some neurons with demylenation of nerve fibers and privascular and pricellular edema. This investigation proves the toxic effects of Profenofos, and Chlorpyrifos at organ level.
Conclusion: The histopathological data showed that profenofos exhibited histopathological changes in liver, kidney, spleen and brain. Liver showed hepatic cell damage with degenerative changes. Kidney showed heamorrhages, edema, necrosis and glomeruli shrinkage. The spleen showed slight deplesion of the lymphocytes of the white pulp. The brain showed interstitial edema and severe necrosis. From these results we concluded that liver is the most sensitive organ and profenofos damage the structure of liver cells more severely than chlorpyrifos on albino mice. 
 Nolan, R.J., Rick, D.L., Freshour, N.L. and Saunders, J.H., 1984. Chlorpyrifos: pharmacokinetics in human volunteers. Toxicology and applied pharmacology, 73(1), pp.8-15.
 Singh, B.K., Walker, A., Morgan, J.A.W. and Wright, D.J., 2003. Effects of soil pH on the biodegradation of chlorpyrifos and isolation of a chlorpyrifos-degrading bacterium. Applied and environmental microbiology, 69(9), pp.5198-5206.
 Barron, M.G. and Woodburn, K.B., 1995. Ecotoxicology of chlorpyrifos. In Reviews of environmental contamination and toxicology (pp. 1-93). Springer, New York, NY.
 Andreadis, G., Albanis, T., Andreadou, E., Mitka, S., Eleftheriou, F., Lampropoulou, D., Avramidis, N. and Patoucheas, D. (2013) “Effect of Dimethoate and Chlorpyrifos in Hepatic and Renal Function of People Belonging to Risk Groups in Iraklia Serres (N. Greece)”, Journal of Advances in Medicine and Medical Research, 4(4), pp. 949-956. doi: 10.9734/BJMMR/2014/5828.
 El-bendary, H. M., Shaker, M. H., Saleh, A. A., Negm, S. E., Khadey, M. E. and Eldeen, F. A. (2013) “Histopathological Changes Associated with Exposure of Male Mice to Profenofos and Chlorpyrifos”, Annual Research & Review in Biology, 4(5), pp. 766-777. doi: 10.9734/ARRB/2014/4924.