Chlorpyrifos formulations

Wet wipe sampling is generally not recommended for carpet, upholstery and other fabric-covered or soft surfaces because the solvent may be absorbed into the surface being sampled. Wipes of soft surfaces also are less likely than wipes of hard surfaces to reflect the dermal exposure potential (Ness, 1994). However, Lu and Fenske (1999) recently reported the use of cotton gauze wetted by misting with distilled water to wipe carpets freshly treated with a chlorpyrifos formulation (Dursban L.O.) and found it to be 23 to 24 times more efficient than transfer to dry palm presses. 

Koehler, P.G. and H.A. Moye (1995b). Chlorpyrifos formulation effect on airborne residues following broadcast application for cat flea (siphonaptera pulicidae) control, J. Econ. Entomol, 88, 918-923. 

Vacarro, J.R. (1993). Risks associated with exposure to chlorpyrifos and chlorpyrifos formulation components, in Pesticides in Urban Environments, K.D. Racke and A.R. Leslie (Eds), ACS Symposium Series 522, American Chemical Society, Washington, DC, USA, pp. 297-306. 

Field fortifications were prepared to check the field/storage stability of the dermal dosimeters, handwashes, and air filters. The field fortifications were prepared using the formulated product undiluted for "high" level spikes and diluted with water (-1 pg/mL chlorpyrifos) for the "low" level field spikes. Field fortification solutions for urine were prepared from a 3,5,6-TCP standard in acetonitrile utilizing an 1.2-pg/mL solution for the "high" field fortifications and an -0.01-ug/mL solution for the "low" level fortifications. 

When the data in Table 4 were given full evaluation, it was recommended that the 50W formulation of chlorpyrifos no longer be marketed in bags that allowed significant exposure for mixer-loaders of this product. This product was removed from the marketplace and was replaced with one in which the wettable powder (WP) is in water-dissolvable packets. Exposure data on other active ingredients have clearly demonstrated reduced exposure with this type of packaging. The other uses were deemed to present a minimal hazard to users, and only minor protective measures have been recommended to workers. 

Formulations of chlorpyrifos include emulsifiable concentrates, wettable powders, granules, pellets, microencapsulates, and impregnated materials. Suggested diluents for concentrates include water and petroleum distillates, such as kerosene and diesel oil. Carrier compounds include synthetic clays with alkyl/aryl sulfonates as wetting agents (Table 14.1). Little information is available to assess the influence of various use formulations on toxicity, dispersal, decomposition, and bioavailability. Chemical and other properties of chlorpyrifos are summarized in Table 14.2 and Figure 14.1. 

Nelson, J.H. and E.S. Evans, Jr. 1973. Field evaluations of the larvicidal effectiveness. Effects on Non-target Species and Environmental Residues of a Slow-Release Polymer Formulation of Chlorpyrifos. U.S. Army Environ. Hygiene Agen. Rep. No. 44-022-73/75. Aberdeen Proving Ground, Maryland. 15 pp. 

Nelson, J.H., D.L. Stonebumer, E.S. Evans, Jr., N.E. Pennington, and M.V. Meisch. 1976. Diatom diversity as a function of insecticidal treatment with a controlled-release formulation of chlorpyrifos. Bull. Environ. Contam. Toxicol. 15 630-634. 

Enthusiasm for chemicals by the industry and the public, however, went largely unabated, and indeed the number and range of available and recommended chemicals began to multiply in this period, with specialized formulations targeted at specific weed and insect problems. Aldrin, carbaryl, diazinon, Dicamba, meta-chlorophenylpiperazine (MCPP), chlorpyrifos, Carbaryl, Pyrethrum, and Dacthal (DCPA) all found their way to consumer markets in the next few years, capped by the arrival of glyphosate (known most commonly by its trade name Roundup ). Despite setbacks (as in the case of DDT), the chemical approach to lawn care has become normal and widespread, with more households using these chemicals every year. 

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). 

Chapman, R.A. and Chapman, P.C. Persistence of granular and ec formulations of chlorpyrifos in a mineral and organic soil incubated in open and closed containers, J. Environ. Sci Health, B21(6) 447-456, 1986. 

Biocides most often found in the indoor environment are chlorinated hydrocarbons like chlordane, DDT, dieldrin, lindane, heptachlor and methoxychlor, pyrethroids like cyfluthrin, cypermethrin, and permethrin, organophosphates like chlorpyrifos, diazinon, dichlorvos, isofenfos, and malathion, carbamates like ben-diocarb, carbaryl and propoxur and chlorophenols like pentachlorophenol (PCP), chlorocresol (4-chloro-3-methylphenol) and o-phenylphenol. Residues formed in house dust may vary in different countries (Butte, 2003), but biocides like chlorpyrifos, DDT, methoxychlor, permethrin, pentchlorophenol and propoxur seem to be the active compounds in biocide formulations even in different continents, as they are found equally in house dust samples form Germany and the USA (Becker et al., 2002 Butte, 2003 Camann, Colt and Zuniga, 2002). Concentrations of biocides in house dust are mostly in the milligram per kilogram range, they seldom exceed a microgram per cubic meter in indoor air. 

Patterson, 1991). Indoor air levels of chlorpyrifos applied as a microencapsulated formulation were measured at 3.1p,g/m 0-2 h after broadcast spraying and 5.2 p,g/m after 24h, compared to 30 and 15 p.g/m, respectively, for the emulsi-liable concentrate (Koehler and Moye, 1995a). After 48 h, levels were still about double for the emulsifiable concentrate application (8.5 p-g/m versus 4.0 pg/m ). 

Unfortunately, it is not possible to accurately predict rates of volatilization or project air concenpations based on vapor pressures. Even when ambient conditions, substtates and formulations are similar, emission rates for pesticides will depend on other factors such as the concenttation and molecular structure of the active ingredient. Jackson and Lewis (1981) compared emission rates from three kinds of pest conttol sttips in the same room under constant conditions of temperature (21 1 °C) and humidity (50 20 %) and found that room air concentta-tions over a period of 30d were much higher for diazinon than for chlorpyrifos, but similar to those for propoxur [2-(l-methylethoxy)phenylmethylcarbamate]. On Day 2 , room air levels were 0.76 pg/m for diazinon, 0.14 pg/m for chlorpyrifos and 0.79 pg/m for propoxur. After 30 d, the air concenttations were 1.21, 0.16 and 0.70 pg/m, respectively. The vapor pressure of diazinon is nearly 100 times higher than that of chlorpyrifos and nearly 1000 times lower than that of propoxur (4 x 10 kPa at 20 °C). 

Somewhat water-soluble pesticides such as acid herbicides will be washed from foliar surfaces and into subsurface soils by rainfall. For example, dislodge-able turf residues of 2,4-D after a 2.54-cm rainfall have been reported to be only 1-5% of those found at 4-8 h after application (Nishioka et al., 1996 USEPA, 1997c). However, dew or rain on aged turf residues may increase their dislodgeability (Nishioka et al, 1996). OP insecticides are semivolatile and will vaporize from surfaces after applications. Chlorpyrifos vaporizes rapidly from lawns if applied in aqueous formulations. Diazinon, which is used on lawns as well as indoors, dissipates even more rapidly. However, the persistence of OP... 

Koehler, P.G. and R.S. Patterson (1991). Residual effectiveness of chlorpyrifos and diazi-non formulations for German cockroach (orthoptera blattellidae) on panels placed in commercial food preparation areas, J. Entomol ScL, 26, 59-63. 

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