At a presentation delivered during the New England Regional Turfgrass Conference and Show here March 19, Dr. John Clark outlined the results of the three-year, $250,000 study. The work was sponsored by the USGA, the New England Regional Turfgrass Foundation, the United States Department of Agriculture, Dow AgroSciences and Bayer.
“The EPA didn’t ask us to do it [the study],” said Clark. “The driving issue is they are in the process of reregistering through FQPA and as the industry looks at this, if you don’t have numbers to show what a chemical’s input is into the EPA’s risk cup, then they just make the numbers up. Once the risk cup is full, they have to drop uses and the first ones to get dropped would be turf and other home uses.”
However, the research did more than just quantify critical risk values for the EPA. Clark’s study also demonstrated ways superintendents can minimize exposure risks. Further research will develop data that covers the physical chemistry of compounds allowing exposure rates and allowable daily intake (ADI) figures to be calculated for an individual active ingredient without any additional study.
In this first phase, Clark studied chlorpyrifos (Dursban Pro), carbaryl (Sevin) and cyfluthrin (Tempo). The three compounds were chosen because of their differing levels of toxicity, volatility and water solubility.
At this point, full results are only available for chlorpyrifos, but the results are encouraging. Under the previously allowed four pound per acre rate of chlorpyrifos, the ADI was right at the one microgram per kilogram a day limit. However, under the new EPA allowable rate of one pound per acre, the ADI falls to .25, well below the limit. While ADI for the other compounds is not currently available, Clark said the initial figures are favorable.
CALCULATING RISK
In order to calculate pesticide exposure to golfers, Clark constructed a 110-meter by 20-meter “golf course” on a bentgrass field. With greens and tees on both ends of the field, Clark’s two foursomes played a simulated 6,800-yard golf course, which took an average of four hours to finish.
The first foursome, the dosimetry group, had to wear special solvent extractive cotton shirts, hats, gloves and pants and air samplers. After a round of golf, these suits were analyzed to see how much pesticide matter golfers come into contact with. The results found that the greatest exposure occurred in this order: lower legs, hands, lower arms and face.
The second foursome, the biomonitoring group, wore shorts and golf shirts instead of white suits, but they were subjected to urinary metabolite tests. These tests use existing toxicokentic data to measure the amount of the compound that is excreted in urine and calculate the amount of pesticide absorbed by each individual.
The third part of the study involved environmental sampling that collected residue data from areas on the treated plots and in areas surrounding the treated plots to determine the spread of the compounds.
REDUCING EXPOSURE RISKS
While the research has shown the current rate for chlorpyrifos to be below the ADI, Clark also confirmed the usefulness of several cultural practices that further reduce exposure risks.
Clark obtained the ADI figures by irrigating with a quarter- to a half-inch of water following an application and waiting one full hour before re-entry into the treated area. Irrigating with this amount reduced residues by 90 percent, and the exposure risk was reduced by 50 percent by waiting an hour before re-entry. By applying chlorpyrifos to just tees and greens, Clark lowered the ADI from .25 to .2.
“You can further reduce risks by only applying pesticides to six holes at a time or by following the last group off the course at night, giving the materials overnight to dissipate,” said Clark.
Going forward, Clark will be completing the extensive testing on carbaryl and cyfluthrin in addition to several other compounds that cover other physical chemistries.
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