Reentry problems involving the use of dialifor on grapes in the San Joaquin Valley of California

Abstract

Abstract. An investigation was made into an illness episode characterized by cholinesterase depression and cholinergic symptoms reported among 118 field workers harvesting grapes treated with Torak | (dialifor) and Zolone | (phosalone) in a vineyard near Madera, California. Dialifor had been applied at the rate of 1.0 pound per acre in 30 gallons of water between 15 and 40 days earlier using a Kinkelder air blast sprayer. Dissipation studies in an earlier study in Soledad, California, using concentrated spray resulted in initial dislodgeable residues of 2.1 ug/cm 2 with a half-life of 14 to 15 days. A similar level of dislodgeable residue resulted at the time of application in the vineyard at Madera. Dislodgeable residues as high as 0.7 ug/cm 2 were encountered by workers at the time of entry with most residues being in the range of 0.11 to 0.45 ug/cm 2. Residue of dialifor on the foliage in 36 other grape vineyards in the San Joaquin Valley were determined at the time of harvest and were shown to be 0.13 ug/cm 2 or less. In four of the 36 vineyards, blood was obtained from workers harvesting grapes. None of the field workers had blood cholinesterase values outside control values.The investigation indicated that with initial dislodgeable residues of dialifor as high as 2.3 ug/cm 2, a period of at least 65 days is required before a possibly safe level of something less than 0.06 ug/cm 2 is reached. The analysis of the residues in the 36 other vineyards indicated that the initial deposits and/ or the half-life of dialifor varied considerably throughout the San Joaquin Valley. Because of this variation, the use of reentry intervals for dialifor may require replacement by on-site residue tests prior to entry. The results indicated that phosalone residues were not responsible for the illness in the field workers.

Blood Cholinesterases as Human Biomarkers of Organophosphorus Pesticide Exposure

“…Phosalone residues of 0. 7 J..Lg/cm 2 and phosalone oxon of 2.2 ppm total did not depress RBC AChE of workers (Knaak et al 1978c). Knaak et al (1978a) also studied workers reentering a citrus grove treated with phosalone 21 d earlier and another grove treated with phosalone 14 d earlier.…”

“…Worker exposure to OPs resulting in illnesses causes a shift in the mean (AChE values) to lower values and a corresponding shift in the minimum and maximum values closer to the mean value. Knaak et al (1978c) investigated an illness episode involving 118 workers exposed to dialifor (Torak®) and phosalone reentering grape vineyards. Workers were exposed to dislodgeable foliar residues of dialifor of 0.54 J..Lg/cm 2 on Aug. 30 and to 0.14-0.16 J..Lg/cm 2 on Sept. 7-9, just before reporting ill. RBC AChE and plasma BChE were depressed to about 45% (RBC) and 50% (plasma) of control with dislodgeable residues estimated to have been 2.2 J..Lg/cm 2 .…”

Environmental fate of dialifor and formation of its oxygen analog following application on grape vines in the San Joaquin Valley, California [USA]

“…The study reported in this communcation resulted from an investigation involving a reported illness episode among 118 fieldworkers harvesting grapes in the San Joaquin Valley of California (Knaak et al, 1978). Dialifor (Torak) and phosalone (Zolone) residues were found on the foliage where the workers had been working.…”

“…Little is known about the toxicity of the oxygen analogue of dialifor, but if one could assume the analogue to be several times more toxic, as is true with many other organophosphate insecticides, the levels found, though much lower, may have contributed to the poisoning episode. Knaak et al (1978) further re-Department of Environmental Toxicology, University of California, Davis, Davis, California 95616. 0021-8561/80/1428-1078$01.00/0 ported a dissipation study of dialifor on grapes conducted in the Coastal Range of California.…”

“…He reported that a 1.0 lb 100 gal"1 acre"1 application applied with a modified speed sprayer gave an initial dislodgeable residue of 0.41 Mg/cm2 which is ~20% the amount found in the Coastal Range study. Knaak et al (1978) attributed this difference in initial deposits and dissipation with different kinds of spray equipment and dust to the foliage or "inert" material in formulations. Reported studies with parathion by Gunther et al (1977) and others would support the latter concept.…”