Chlorpyrifos monitoring

Richardson RJ, Moore TB, Kayyali US, et al. 1993. Chlorpyrifos Assessment of potential for delayed neurotoxicity by repeated dosing in adult hens with monitoring of brain acetylcholinesterase, brain and lymphocyte neurotoxic esterase, and plasma butyrylcholinesterase activities. Fundam Appl Toxicol 21 89-96. 

The absorbed dose or body burden of chlorpyrifos can be estimated using urinary monitoring data as follows 3... 

Comparison of exposure levels — total absorbed dose of chlorpyrifos (passive dosimetry vs. urinary monitoring)... 

Table 7 Comparison of Exposure Estimated Levels (Total Absorbed Dose of Chlorpyrifos) Dosimetry vs. Urine Monitoring...

Honeycutt, R.C., Day, Jr., E.W., Shurdut, B.A., and Vaccaro, J.R., Use of simultaneous biological monitoring and dermal dosimetry techniques to determine the exposure of chlorpyrifos to applicators and re-entry workers, in Worker Exposure to Agrochemicals Methods for Monitoring and Assessment, Honeycutt, R.C. and Day, E.W., Jr., Eds., Lewis Publishers, Boca Raton, FL, 2000, chap. 2. 

To monitor the absorbed chlorpyrifos doses in human volunteers, urine was collected before and following a 4-hr activity period on the treated grass surface(re-entry). The urine was analyzed for 3,5,6-trichloropyridinol (3,5,6-TCP), the urinary metabolite of chlorpyrifos, and creatinine, which was determined to verify completeness of urine collection by each volunteer. 

Quantitative data for the 3,5,6-TCP and 13C2-3,5,6-TCP were obtained by selected ion monitoring of the dichloropyridinol fragment ions (m/z 161 to 165 0.1 sec/scan). The amount of TCP found in the urine was used to calculate the amount of chlorpyrifos represented by that amount of TCP based on molecular weight differences. 

Table 1 Liquid Turf Study Adult Inhalation Dose of Chlorpyrifos Based on Air Monitoring Data...

The WBDs retained an average potential dermal exposure (PDE) of 13,757 pg chlorpyrifos. If clothing penetration is assumed to be 10% and dermal absorption 9.6% per 24 hr, then the absorbed dose would be 132 pg, and the absorbed dosage would be about 1.9 pg/kg. Biological monitoring of the 13 volunteers wearing cotton dosimeters indicated that the absorbed daily dose that penetrated the WBD and was absorbed was 2 pg chlorpyrifos equivalents/kg (Table 2). 

Historically, OP insecticides have not been frequently detected in surface waters of the USA [79]. However, occurrence of several OP insecticides in US tributaries to Lake Erie has been reported [60]. Several of the sites monitored included urban storm-water inputs, which might explain the increased presence of diazinon and chlorpyrifos in these tributaries. Diazinon had been measured on numerous occasions in urban tributaries to Lakes Ontario and Erie [68]. Struger [67] also reported frequent detections of azinphos-methyl (guthion), chlorpyrifos, and diazinon in two small streams draining the Niagara fruit belt region of Lake Ontario. 

Chlorpyrifos provides an example of the utility of human pharmacokinetic models to estimate daily dose from biomonitoring data for a rapidly cleared pesticide. The urinary metabolite trichloro-2-pyridinol (TCP) is used in the NHANES study to monitor population exposure to chlorpyrifos (CDC 2005). Several epidemiologic studies have linked chlorpyrifos exposure to adverse birth outcomes through associations between urinary and blood biomarkers and have demonstrated maternal exposure and physiologic measurements in the neonate (Berkowitz et al. 2003, 2004 Whyatt et al. 2004 Needham 2005). 

Urinary Metabolite Monitoring 28 Salivary Monitoring 29 VALIDATION OF PASSIVE DOSIMETRY 30 Atrazine 30 Chlorpyrifos 31... 

Another study monitored exposure to five workers using both passive dosimetry and biomonitoring during the application of chlorpyrifos as a termiticide. The mean absorbed chlorpyrifos dose of 4.27 mg/kg/d from the biomonitoring study was comparable to that measured in the passive dosimetry study (3.24 mg/kg/d). 

A novel device was designed to estimate the dislodgeability of dust-associated pesticide residues by skin contact (Edwards and Lioy, 1999). Called the EL Sampler , the device consists of a spring-loaded assembly that permits the sampling medium to be pressed lightly (12g/cm or 1160 Pa) onto the surface to be monitored. A 10-cm x 15-cm Empore C-18 extraction membrane was used for the sampling medium. The material was chosen after controlled experiments on particle adhesion showed it to pick up the same distribution of test dust particle sizes as the human hand. In studies in which the EL sampler was pressed onto polyethylene surfaces coated with house dust and then sprayed with a solution of pesticides in 2-propanol, the device was found to collect 35%, 31 %, 32% and 18 %, respectively, of chlorpyrifos, diazinon (0,0-diethyl 0-[6-methyl-2-(l-methylethyl)-4-pyrimidinyl] phosphorothioate), malathion and atrazine (6-chloro-A -ethyl-A -isopropyl-l,3,5-triazine-2,4-diamine). Parallel studies with human hand presses (full hand at 6.8 kg = ca. 6900 Pa) yielded collection efficiencies of 42 %, 29 %, 43 % and 21 %, respectively. 

Fenske, R.A. and K.P. Elkner (1990). Multi-route exposure assessment and biological monitoring of urban pesticide applicators during structural control treatments with chlorpyrifos, Toxicol. Ind. Health, 6, 349-371. 

Reports of other pesticide residues are less frequent. Propanil was present in 42% of the soil samples analyzed as well as ethyl parathion in 29%, methyl parathion in 17% and chlorpyrifos in 45% of the samples [14]. The concentrations of all three individual compounds were low (0.5-14 pg-kg ). Residues of 2,4-D were found only in a few samples but MCPB was present in the 60% of the sanq les, the levels of these two compounds varied between < 0.01 to 0.12 mg kg". In El Salvador, where paraquat is extensively used, different regions of the country were monitored. Residues in Sonsonate soil samples averaged 7.14 mg-kg, while in Ahuachapan, one sample contained as much as 16.47 mg-kg" paraquat [15]. Tatui soils from Sao Paulo State, Brazil, contained triflu-raline residues of 1.2 mg-kg" six weeks after application also methyl parathion residues up to 2 mg-kg" [16]. Reports on residues of newer pesticides in soil are rare. 

---