Dosimetry, passive chlorpyrifos

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

Assessments of risks associated with the use of chlorpyrifos insecticide products for workers have been made. The assessments are based on the results of field studies conducted in citrus groves, a Christmas tree farm, cauliflower and tomato fields, and greenhouses that utilized both passive dosimetry and biomonitoring techniques to determine exposure. The biomonitoring results likely provide the best estimate of absorbed dose of chlorpyrifos, and these have been compared to the acute and chronic no observed effect levels (NOELs) for chlorpyrifos. Standard margin-of-exposure (MOE) calculations using the geometric mean of the data are performed however, probability (Student s f-test) and distributional (Monte Carlo simulation) analyses are deemed to provide more realistic evaluations of exposure and risk to the exposed population. 

The results from the several studies that have been conducted to measure exposures associated with the use of chlorpyrifos are summarized in Tables 1 and 2. Table 1 summarizes results from mixer-loader and applicator studies reported by Honeycutt et al.1 Listed for each work description are the number of replicates, the arithmetic mean, and the geometric mean for the replicates from both the passive dosimetry measurements and the biomonitoring tech-... 

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

The USEPA reviewed a number of registrant-submitted studies to assess exposure to handlers applying chlorpyrifos in agricultural and residential settings (USEPA, 2001). The biomonitoring studies measured urinary concentrations of the primary chlorpyrifos metabolite and back-calculated these to the absorbed dose of the parent. The passive dosimetry study results were corrected for 3 % dermal absorption from a human dosing study (Nolan et al 1984). The results of the studies are reported in Table 1.4 and demonstrate fairly close concordance between the two methodologies. 

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). 

Table 1.4 Comparison of concurrent biomonitoring and passive dosimetry data s from chlorpyrifos exposure studies (USEPA, 2001)...

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