Occupational exposure to agricultural chemicals: effect on the activities of some enzymes in the blood of farm workers.

OBJECTIVE: To determine the effect of different durations of exposure to agricultural chemicals on the activities of the blood enzymes delta-aminolevulinic acid dehydratase (ALAD), superoxide dismutase (SOD), and cholinesterase (ChE) in tobacco field workers. METHODS: For this preliminary investigation, 8 volunteers (all smoked tobacco) who were working on a small tobacco farm were monitored over a period of 2 years along with a comparable urban unexposed group (n = 4). During the growing season between 1994 and 1996, dermal and respiratory exposure were determined and blood samples were drawn after the following durations of field work: (1) preexposure (0 DAY); (2) after 1 day of field work (1 DAY) - workers reentered fields at 24 h after spraying of acephate and maleic hydrazide; (3) after 30 days of field work (postspraying; 30 DAYS); and (4) Postexposure - no tobacco production. Standard analytical methods were used. RESULTS: Activity of ALAD was depressed by 30% after 1 DAY and there was no further decrease in ALAD activity after 30 DAYS of field work. SOD activity, in contrast, declined by 29% and 50% after 1 DAY and 30 DAYS, respectively, as compared with 0-DAY activity and that of the urban control, which was similar to 0-DAY activity (P< or =0.05). Plasma ChE activity declined by 19% after both 1 and 30 DAYS of exposure/field work. The activities of all three enzymes were restored to urban control or preexposure levels during postexposure. Plasma Cd levels were high in the samples taken after 30 DAYS as compared with the preexposure levels. Respiratory nicotine exposure was highest after 30 DAYS of field work. CONCLUSION: This preliminary study suggests that erythrocyte SOD is a sensitive indicator of exposure to agricultural chemicals in tobacco field workers.

Residue levels of pyrethrins and piperonyl butoxide in soil and runoff water.

Simultaneous analysis of pyrethrins (Py-I and Py-II) and piperonyl butoxide (PBO) in soil and runoff water samples following field application of a new pyrethrum formulation containing pyrethrins (Py's) and PBO is described. Residues of total Py's and PBO were extracted from soil samples using hexane-acetone (9:1). A solid phase extraction (SPE) column containing C18-octadecyl bonded silica was used to separate Py's and PBO residues from runoff water. Residues in soil and water were quantitated by high performance liquid chromatography (HPLC) equipped with C18-column and a UV detector. Concentration of Py-II in soil was 100 times higher than that of Py-I 1 h following treatment and 9.6 times higher than Py-I in runoff surface water 11 days following treatment. Results indicated that Py's are non-persistent in soil (even though lipophillic) and water when applied at the recommended rate of 6 lbs (5.31 g A.I.) per acre. There was a consistent decrease in total Py's residues as time after spraying increased. Py's residues in soil decreased from 0.91 to 0.11 ppm 4 days following treatment and one month after treatment only 0.002 ppm were detected. The highest concentration of Py's in runoff water was 36.09 ng/liter following the first rainfall (11 days following treatment). PBO initial residues detected in soil samples were low (0.84 microgram/g soil) while no residues of PBO were detected in runoff water.

Comparative inhibition of enzymes of human erythrocytes and plasma in vitro by agricultural chemicals.

Farm workers generally are exposed to a combination of synthetic agricultural chemicals and natural products while working in the fields. These biologically active compounds control infestation of tobacco by insects, and plant growth. We have investigated, in vitro, the effects of acephate (AP), cadmium (Cd), methamidophos (MAP), maleic hydrazide (MH), and nicotine (NI) on the activities of the erythrocyte enzymes delta-aminolevulinic acid dehydratase (ALAD), superoxide dismutase (SOD), and plasma cholinesterase (CHE). ALAD, SOD, and plasma CHE were assayed, using aminolevulinic acid, pyrogallol, or butyryl thiocholine as substrates, respectively. Different concentrations of the above chemicals were used to obtain minimum and maximum inhibition of the enzymes, and for the development of inhibition dose response curves. These curves were used to determine the concentration of each chemical required to inhibit 50% of enzyme activity (I50). The I50 concentrations of various chemicals for each enzyme were determined in mM for ALAD: AP=95.5, Cd=1.4x10(-3), MH=2.8, MAP=7.1, NI=60.8; for SOD: AP=1.2, Cd=0.8x10(-7), MH=0.04, MAP=0.42, NI=0.81; for CHE: AP=5.6, Cd=18. 8x10(-5), MAP=18.4x10(-4); CHE was not inhibited by MH and NI. Our data indicate that AP inhibited both SOD and CHE to a maximum of 91 and 87%, while MH inhibited both SOD and ALAD to a maximum 78 and 90%. However, SOD was the enzyme that was most sensitive to all the agricultural-chemicals tested in this study. The inhibition of these enzymes will enable the development of a sensitive biomarker and the assessment of long term health risks in farm workers.

Volatile compounds from crabapple (Malus spp.) cultivars differing in susceptibility to the Japanese beetle (Popillia japonica Newman).

The volatile compounds emitted by leaves of four crabapple cultivars susceptible to damage by Japanese beetles and four relatively resistant cultivars were examined. Twelve compounds, mostly terpene hydrocarbons, were identified from intact leaves. The terpenes (E)-ß-ocimene, caryophylene, germacrene D and (E,E)-α-farnesene occurred in significantly higher levels in susceptible cultivars, whereas resistant cultivars produced greater amounts of (E)-4,8-dimethyl 1,3,7-nonatriene and linalool. The relative attractiveness of the cultivars as determined in a pitfall bioassay, however, was not related to their susceptibility to the Japanese beetle as previously determined by defoliation sustained in the field. The attractiveness of individual cultivars was found to be positiviely correlated with linalool as a percent of the total volatile blend emitted by leaves. This study and previous work suggest that variation in susceptibility of crabapple cultivars to defoliation by Japanese beetles is not due to the attractiveness of the individual cultivars but rather to nonvolatile components of susceptibility and/or resistance. A scenario for host location by the Japanese beetle is presented.

Field worker exposure to selected insecticides applied to corn via center-pivot irrigation.

Field workers were monitored for dermal and respiratory exposure to chlorpyrifos (with and without crop oil), carbaryl, and permethrin at reentry intervals of 2, 4, 8, 24, and 48 h after application. Insecticides were applied to R3 stage corn through an overhead center-pivot irrigation system. Dermal exposure was measured by analyzing 18 gauze pads attached to the clothing of workers to represent human body regions. Hand exposure was determined using cotton gloves. Respiratory exposure was determined using portable air samplers equipped with polyurethane foam plugs to trap ambient insecticide residues. Gas liquid chromatography was used to quantify residues of chlorpyrifos and permethrin in gauze pads, gloves, and foam plugs. Carbaryl residues in pads, gloves, and foam plugs were analyzed using high-performance liquid chromatography. Highest dermal and respiratory exposures were found at the 2-h reentry interval. Exposures decreased as reentry interval increased. Dermal exposure was primarily confined to the hands. Residues detected by air samplers ranged from 0 to 0.03 micrograms/liter. Based on the estimated percentages of acute toxic dose (all less than 0.00038%), the risk of acute toxicity to workers at the intervals studied was low.