Chlorpyrifos applications

Clements, R.O., P.J. Murray, and C.J. Tyas. 1992. The short-term effects on wild goose behaviour of chlorpyrifos application to permanent pasture. Ann. Appl. Biol. 120 17-23. 

No data are available on platelet NTE activity in exposed subjects, and little data on lymphocyte NTE activity. In one reported case of suicidal poisoning with chlorpyrifos, inhibition of lymphocyte NTE was correlated with the enzyme inhibition in peripheral nerves (Osterloh et al., 1983). In another case of attempted suicide with the same compound, inhibition of NTE in peripheral lymphocytes was associated with the development of delayed neuropathy (Lotti, 1986). However, the threshold of NTE inhibition required for delayed neuropathy remains undetermined (Lotti, 1987). Observations in occupationally exposed subjects are limited in number, and more research is needed to investigate the applicability of NTE as a biomarker of exposure to OP pesticides. 

Urine samples were collected in 2-L polypropylene containers on the day prior to application of chlorpyrifos, on the day of application (or reentry), and for 4 days after application (or re-entry). 

Assume 100% respiratory absorption of chlorpyrifos except for mixer-loaders, applicators, and cleanup workers in California who wore respirators which blocked 100% of the respiratory exposure. 

Fit the amount of 3,5,6-TCP excreted in individual urine samples to a one-compartment pharmacokinetic model that describes the time course of 3,5,6-TCP in urine of volunteers following the application of chlorpyrifos to the forearm (72% of dose excreted).3... 

Table 3 Chlorpyrifos Mixer-Loader, Applicator Exposure Study Parameters...

Honeycutt, R.C. and DeGeare, M.A., Evaluation of the Potential Exposure to Chlorpyrifos During Mixing and Loading, Spray Application, Clean-Up Procedures During the Treatment of Citrus Groves with Lorsban 4E Insecticide, unpublished report, HERAC, Inc., January 18, 1994. 

Shurdut, B.A., Murphy, P.G., Nolan, R.J., and McNett, D.A., Lorsban 4E and 50W Insecticides Assessment of Chlorpyrifos Exposures to Applicators, Mix-er/Loaders, and Re-entry Personnel During and Following Application to Low Crops, DowElanco Laboratory Project DECO-HEH 2.1-1-182(118) and DECO-HEH2.1-1-182(124), September 27, 1993. 

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-... 

Table 1 Summary of Estimated Absorbed Doses from Mixer-Loader and Applicator Studies with Chlorpyrifos...

The MOE calculations for the various exposure scenarios with chlorpyrifos are presented in Table 3. Listed in this table are the calculated results for the workers involved with mixing and loading and the application of chlorpyrifos,... 

Table 4 Statistical (Probability) Analysis of Chlorpyrifos Biomonitoring Data for Mixer-Loaders and Applicators...

Means and standard deviations for these distributions were normalized to daily breathing rates (m3/day), and an acceptable range was defined. It was assumed that the "day" represents the duration of time within a working day that chlorpyrifos may be handled by an individual (0.25 to 6.0 hr). It was also assumed that exposures would be negligible for the remainder of the working day following application or other contact. Both the dermal and inhalation exposures were assumed to follow lognormal distributions, which is consistent with common practice for exposure data distributions (for example, in the Pesticide Handlers Exposure Database, PHED). 

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. 

Dermal application routes are also toxic. Some deaths were recorded in turkeys from dermal treatments of 15 to 20 mg chlorpyrifos/kg BW (Schlinke etal. 1969). Higher levels applied to feathers killed turkeys within 8 h (Marshall and Roberts 1978). Newborn piglets (Sus spp.) were especially more sensitive than those 30 to 36 h old to cutaneous applications of chlorpyrifos ... 

Single application of pelletized 10.6% chlorpyrifos to obtain theoretical water concentrations of 250 pg/L and higher... 

These chemicals, as noted previously, are likely far more dangerous to children (especially neurotoxins such as chlorpyrifos) than has been generally suggested to date. Family pesticide use, including lawn herbicide application, has been shown to be related to childhood brain cancer. Malignancies for children linked to pesticides in case reports or case-control studies include leukemia. 

Plant Although no products were identified, the half-life of chlorpyrifos in Bermuda grasses was 2.9 d (Leuck et al., 1975). The concentration and the formulation of application of chlorpyrifos will determine the rate of evaporation from leaf surfaces. Reported foliar half-lives on tomato, orange, and cotton leaves were 15-139, 1.4-96, and 5.5-57 h, respectively (Veierov et al., 1988). 

Veierov, D., Fenigstein, A., Melamed-Madjar, V., and Klein, M. Effects of concentration and application method on decay and residual activity of foliar chlorpyrifos, J. Econ. Entomol., 81(2) 621-627, 1988. 

Methyl parathion is used primarily on cotton. It was one of the first insecticides restricted under the 1996 Food Quality Protection Act (FQPA), which developed new safety standards for human health, especially that of children. It can no longer be used on many fruits and vegetables. Malathion and parathion are the broadest spectrum organophosphate insecticides. There are many other organophosphate insecticides in use in the U.S. today. Many are produced at the 1-5 million Ib/yr level for specific applications. Three other leading organophosphates besides those mentioned already are chlorpyrifos, terbufos, and phorate. 

In 2000 chlorpyrifos, the most commonly used household pesticide product, was outlawed for most household applications, though agricultural use will continue. It has caused unintentional poisoning and may affect brain development in unborn children. 

Currie KL, McDonald EC, Chung LTK, et al. 1990. Concentrations of diazinon, chlorpyrifos, and beniocarb after application in offices. American Industrial Hygiene Association 5 l(l) 23-27. 

The first "real-sample" application is given in Table IX, where chlorpyrifos was extracted from treated grass supplied by an outside collaborating laboratory. Two instruments were used for this application, extracting 11 samples on 4/26/89 and 8 samples on 10/13/90. The relative standard deviations were 3.9% and 1.7% respectively. The latter value is extraordinarily good since, in the work reported, precision due to the chromatographic analysis variability was between 1% and 3%. Further, the values of precision reported by the supplier for manual extraction of chlorpyrifos from similar matrices, leaves and roots, were 8% and 4% respectively. 

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