Francis A. Gunther

Translocation of the polychlorinated biphenyl Aroclor 1254 from soil into carrots under field conditions.

The extent and selectivity of transfer of the components of the polychlorinated biphenyl (PCB) Aroclor 1254 from a sandy loam soil into carrots under field conditions were studied. Five of the gas chromatographic peaks of this PCB, designated 1, 4, 5, 8, and 10 with increasing retention time, were quantitated. After 23 months the concentration of peak 10 in soil remained unchanged, but peak 1 decreased by 34±3%. Lesser chlorinated peak 1 was translocated from soil into carrots five to eight times more than highly chlorinated peak 10. The residues (in ppm) of peaks 1 and 10 in carrot root were 30 to 50% and 3 to 4%, respectively, of that of the soil: The degree of translocation for PCBs was of the same order of magnitude as for the persistent organochlorine insecticides. Carrot foliage contained 1 to 6% as much of the PCB residues (in ppm) as the soil. Since peak 1 was present in about 2.5 times greater amount than peak 10 in foliage, whereas it was present in about five to nine times greater amount in roots, direct foliar contamination by soil dust is suggested.

Uptake of a PCB (Aroclor 1254) from soil by carrots under field conditions

SummaryThe change in composition of Aroclor 1254 in soil was evident over an eleven-month period. Dissipation appeared to parallel the degree of chlorination. The lesser chlorinated biphenyls were slowly dissipated while the more highly chlorinated biphenyls were not appreciably affected. PCBs were absorbed by carrot roots; increasing translocation was associated with decreasing biphenyl chlorination. Since 97% of the residue was found in the peel, very little translocation occurred in the plant tissue.

Varying persistence of polychlorinated biphenyls in six California soils under laboratory conditions

Each fortified and control sample, moistened to 40~ saturation, was inoculated and kept in an enameled tray loosely covered with a glass plate to retard water evaporation, substrate volatilization, and photodecomposition. Thus, the substrates would be subject to possible microbial degradation, chemical degradation, and adsorption to soil colloids, but not losses due to leaching or soil transport. Properties of the soils used were determined by HERMANSON and RIBLE (1967) (See Table I).

Worker environment research: Dioxathion (delnav®) residues on and in orange fruits and leaves, in dislodgable particulate matter, and in the soil beneath sprayed trees

Deposits and residues of dioxathion disappear at similar rates on and in the rind of oranges and the leaves of orange trees; dislodgable residues on the leaves dissipate at the same rate as the penetrated residues. This fact is important in evaluating the potential hazard to workers in treated groves because their exposure to pesticide residues is principally through the dislodgable residues. Samples of vapor and particulate matter taken during violent shaking of the trees show that the exposure of workers is almost entirely through contact with, and inhalation of, particulate matter, dermal contact probably being the more important. In one experiment, pickers were used in trees sprayed with dust containing no toxicant to determine the actual weights of dust that are inhaled (using Unico air samplers) and that accumulate on their bare arms (by washing at ten-minute intervals). The data show that several times as much dust is contacted dermally than is inhaled. Washing the entire trees with a dilute detergent solution removes a significant part of the dislodgable residue; as much as 30 percent is removed 46 days after spraying. The data presented in this paper provide a guide for toxicologists to permit the design of tests required to evaluate hazards workers encounter in pesticide-citrus groves.

Pesticide applicator exposure to insecticides during treatment of citrus trees with oscillating boom and airblast units

To obtain relative exposure data for the spray rig driver applying insecticides to California citrus trees, parathion [O,O-diethylO-(4-nitrophenyl) phosphorothioate] and dimethoate [O,O dimethylS-(2-(methylamino)-2-oxoethyl) phosphorodithioate] were applied with oscillating boom and airblast spray units. Spraying conditions were varied to simulate commercial application practices. Test conditions were used which varied from providing no driver protection to that of providing charcoal-filtered air. Both singleand double-side delivery systems were employed. Gauze sponges pinned to the coveralls of the driver were used to indicate dermal exposure potential, and ethylene glycol-containing impinger type air samplers were used to indicate inhalation exposure potential. Urine samples were collected and analyzed for dialkylphosphate and thiophosphate levels.

Persistence of parathion in six California soils under laboratory conditions

Persistence curves obtained for parathion in six California soils are partially dependent on soil type. The possibility that long-term, low-level parathion soil residues can exist is confirmed. Each soil was fortified at 20 ppm, kept in an enameled tray, and maintained at 30°C with a soil moisture level of approximately 40 percent of saturation. The parathion residue in Laveen loamy sand drops rapidly to about 0.2 ppm in 30 days. In Mocho silt loam, Linne clay, and Madera sandy loam, it drops to between one and two ppm in 30 days and gradually decreases to about 0.2 ppm in 130 days. The rapid parathion residue decline is attributed to microbial degradation. In Windy loam, the residue after eight months remains above three ppm. In two experiments differing slightly in soil moisture, the residue in Santa Lucia silt loam is about 1.5 ppm after eight months in one experiment and about 0.5 ppm after six months in the other. The latter two soil types give linear semi-logarithmic persistence curves, suggestive of degradation by hydrolysis.Aminoparathion, above the detectable level of one ppm, is not found in Madera sandy loam after fortification with parathion at 200 ppm. However, a sharp decline of the parathion residue after ten days suggests microbial degradation. Three ppm aminoparathion were recovered after seven days when Madera sandy loam was fortified at 20 ppm with parathion and submerged under water. In contrast, the degradation of parathion remaining in Windy loam (3.2 ppm) and Santa Lucia silt loam (2.2 ppm) 7.7 months after fortification is not greatly accelerated when flooded with water.

The oxidation of parathion to paraoxon. II. By use of ozone

ConclusionsParathion in low concentrations in aqueous solutions can be readily converted to paraoxon in high yield by use of ozone. However, the reaction is not a general one for the production of other oxons from their corresponding organothiophosphorus analogs.

Reentry Problems Involving the Use of Dialifor on Grapes in the San Joaquin Valley of California

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/cm2 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/cm2 were encountered by workers at the time of entry with most residues being in the range of 0.11 to 0.45 ug/cm2. 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/cm2 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/cm2, a period of at least 65 days is required before a possibly safe level of something less than 0.06 ug/cm2 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.

Expanded utility of the Beilstein flame test for organically bound halogens as a sensitive and specific flame photometric detector in the gas chromatographic determination of R-X compounds as illustrated with organochlorine pesticides

In 1962 we published (9) a brief note on the utility of the Beilstein flame test for organohalogen compounds as an adjunct (split stream) glc detector to signal their appearance in the emergent gas stream for facilitating their collection as organohalogen fractions for any purpose. We reported that about 0.17 ~g. of organically bound chlorine/second was visually detectable with the conditions and apparatus used at that time. We further stated that enhanced minimum detectability could be achieved by filter

CURRENT STATUS OF PESTICIDE RESIDUE METHODOLOGY

Analyses for pesticide residues have been conducted at least since the introduction and widespread use of sulfur dioxide as a food preservative, and perhaps earlier with lead, arsenic, sulfur, and tars, although these efforts must have been sporadic and cursory. The intent undoubtedly was to minimize off flavors rather than to protect the public health, with the possible exceptions of arsenic and tars (Gunther, 1966) . By today’s standards and requirements, these analyses were crude estimations, indeed. Systematic residue evaluations were undertaken about 1925, but usually only to relate residues in plant parts with biological efficacy of formulation rather than to prevent possible residue-caused mishaps among consumers. Surprisingly, at least ten different major pesticides were involved during that decade, almost all of them insecticides and half of them organic compounds. Most of the residue assays were of surface “deposits” on plants, and little attention was paid to water, meat and other animal products, and soils, except to speculate about the already apparent arsenic poisoning of soils in apple and pear orchards. The residue analytical procedure in those early days was to extract the sample, concentrate the extract, remove at least major interfering coextractives, and analyze the resultant product. This classic sequence of operations is the one we still use today, except that today’s techniques are more versatile, elaborate, selective, and aseptic with respect to outside contamination. Today we seek to distinguish among a great variety of compounds; in fact, there are more than 400 pesticide chemicals in permitted use. We seek them in various admixtures, sometimes in fractional parts per million in hundreds of crops and crop products, air, soil, water, aquatic species, birds, animals, and man himself, along with numerous toxic metabolic products at levels that are usually much lower. Modern residue techniques are therefore considered to be sophisticated, but the degree of sophistication of the final residue data depends entirely upon the imagination, enterprise, and skill of the analyst. Many types of organic pesticides are available today; some are short-lived and some are long-lived in the environment, but they are all eventually degraded by metabolic, photochemical, oxidative, or hydrolytic processes. Because these alteration products in the environment can often be as pharmacologically significant as the parent compounds, their total fates in the environment have become important, a conception new within the past few years. I t means that so-called residue chemists, formerly by choice a distinct group, and pesticide toxicologists, also a distinct group, must now coordinate their efforts to make optimum contributions to the understanding and thus to the continuing safe use of pesticides in a complex. dynamic environment. In this sense, residue chemistry has been defined (Gunther, 1962) as “ . . . a body of techniques and knowledge biological, chemical, and physical used to determine the residue composition and content of any foodstuff, where a ‘residue’ is an original or any derived residuum from a nonfood chemical added to [introduced into] the foodstuff during any stage of its production.”