Foot Transfer of Lawn-Applied Pesticides from Turf to Carpet: Comparison of Semivolatile Chlorpyrifos with Nonvolatile Chlorothalonil
2002
Nishioka, M. G. | Lewis, R. G. | Brinkman, M. C. | Burkholder, H. M.
Many homeowners use herbicides, insecticides and fungicides for turf grass treatment. These pesticides span a broad spectrum of chemical and physical properties, ranging from nonvolatile to semivolatile and somewhat water soluble to essentially insoluble. Residues of pesticides are found on lawns after direct applications or as a result of drift from applications to ornamentals, gardens, or perimeters of buildings. These residues dissipate by volatilization, transport to soil by rainfall or watering, photochemical and microbial degradation, and other mechanisms. The lifetimes of pesticide residues on turf are generally short relative to those on indoor surfaces. Rainfall, sunlight, volatilization, erosion, microbial degradation, and removal of grass clippings reduce or eliminate most residues in a matter of days or a few weeks. Post-emergence acid herbicides such as 2,4-dichlorophenoxyacetic acid (2,4-D) and dicamba (3,6-dichloro-2-methoxybenzoic acid) are typically applied in the form of amine salts, which have very low vapor pressures, but they have relatively high water solubilities and are rapidly depleted by irrigation or rainfall (Hurto and Prinster 1992; Nishioka et al. 1996). Organophosphate insecticides, such as diazinon and chlorpyrifos (recently withdrawn from residential use), tend to vaporize rather quickly from treated turf grass (Kuhr and Tashiro 1978; Goh et al. 1986; Hurto and Prinster 1992). While pesticide formulations contain adjuvants to increase adhesion to the plant surface, some portion of the residues remaining on the leaves of the grass are dislodgeable and may be transferred to the skin or transported into the home on shoes, clothing and pets. Many of the pesticides identified in house dust and indoor air obviously have outdoor sources (Lewis et a. 1994, 1999; Whitmore et al. 1994, Simeox et al. 1995, Colt 1998). The presence in house dust of pesticides such as 2,4-D, chlorothalonil, carbaryl and bendiocarb, which are typically used on the lawn or garden, suggest track-in of turf and soil residues.The study described here examined the temporal behaviors of dislodgeable turf residues of two pesticides that have been commonly used on lawns and estimated the extent to which they may be tracked into a home by normal foot traffic. This study is similar to an earlier study that evaluated track-in of 2,4-D and dicamba (Nishioka et al. 1996), and was carried out to compare dislodgeable turf residue levels and track-in rates for dissimilar pesticides, application methods, and application rates. The applicability of this test design, and comparison of chemical factors such as volatility and water solubility to significantly different pesticides were evaluated here with the insecticide chlorpyrifos in both emulsifiable concentrate (EC) spray and granular (G) applications and the fungicide chlorothalonil in an EC formulation.
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