W. P. Cahill

Establishment of reentry intervals for organophosphate-treated cotton fields based on human data: I. Ethyl-and methyl parathion

In each of two studies, two human volunteers entered methyl- or methyl-ethyl parathion-treated cotton fields for 30-minute periods at 0, 12, 24, 48, and 72 hours after treatment; foliage residues, and skin, clothing, inhalation, and biomedical data were obtained. The hands are probably the greatest source of absorbed pesticide chemical while the respiratory system is an insignificant source. Trousers collect the largest amounts of residue but the residue on them does not necessarily undergo absorption by the skin. There is not any evidence of plasma- or red-cell cholinesterase depression or a detectable amount ofpara-nitrophenol, following one-day, single, 30-min exposure. It is estimated that an individual can absorb up to 6.0 milligrams of parathion from cotton 24 hours after treatment with parathion and up to 3.0 milligrams 48 hours after such treatment, during an actual 5-hour work day field exposure. Skin-, and clothing contamination data are inadequate bases for evaluating hazard of possible parathion poisoning. Far more useful are measurements of serum parathion, serum-, and cell cholinesterase activities, and urinary excretion ofpara-nitrophenol in exposed individuals.

Establishment of reentry intervals for organophosphate-treated cotton fields based on human data: III. 12 To 72 hours post-treatment exposure to monocrotophos, ethyl- and methyl parathion.

Five human volunteers entered methyl parathion, ethyl parathion, or monocrotophos treated cotton fields for five-hr exposure periods when the residues of the respective pesticides had aged 12 hr, 24 and 48 hr, and 48 and 72 hr. Foliage residues of methyl parathion disappeared fastest, those of monocrotophos slowest. Personal exposure to pesticide was evaluated from contamination of skin, clothing, and ambient air, while actual absorption of chemical was assessed from pesticide concentration in blood, urinary metabolite excretion, and effects on blood cholinesterase activities. There was good correspondence between magnitudes of foliar residue, estimates of personal contamination, and measures of chemical absorption. Field exposures caused no symptoms or clinical signs of organophosphate poisoning and depressed averaged blood cholinesterase activities by no more than 14% of pre-exposure levels.

Dislodgable leaf residues of insecticides on cotton

In a previous study (Ware et al. 1972) we attempted to show the relative degradation rates of selected organophosphate insecticides on cotton. However, the dislodgable nature of these residues was not taken into consideration, since they were expressed on a ppm basis after being extracted from macerated plant material. It was the purpose of this study to determine the dislodgable or easily removed surface residues of seven commonly used insecticides on cotton over a 4-day period following application. Such information is essential in establishing safe reentry times for personnel working in treated fields.

Water florae as indicators of irrigation water contamination by DDT.

Cer ta in c rops have been shown tO be good ind ica to rs of soil contaminat ion by chlor ina ted insec t ic ides . Lichtens te in and Schulz (1) found that the c a r r o t a b s o r b e d m o r e insec t ic ida l r e s i d u e s f r o m soil t r e a t ed with a ldr in and heptachlor than did potato, beet , le t tuce , r ad i sh , cucumber , turnip, cabbage, b rocco l i , c e l e r y or pa rsn ip . C a r r o t s (Daucus carota) , p a r t i c u l a r l y the White Belgium va r i e ty , w e r e shown by Lichtens te in e t al . (2) to have a high affinity for the cyclodiene group of o rganoch lor ine insec t ic ides . This va r i e t y ab so rbed m o r e alclrin, die ldr in , heptachlor and i ts epoxide than did four other v a r i e t i e s grown for two y e a r s in t r ea t ed soil . In explor ing DDT r e s i d u e s and buildup in the food web of a Long Is land e s tua ry , t r e a t ed 20 y e a r s for mosqui to control , Woodwe11 (4) found that DDT r e s i d u e s in the upper l aye r of mud r anged up to 32 pounds per a c r e . At the s a m e t ime he found m a r s h plant shoots to contain 0.33

A rapid on-column extraction-cleanup method for animal fat

Several methods of extraction and cleanup are currently in use for ECGC analysis of chlorinated insecticide residues in animal fat. Generally they include grinding with sand, sodium sulfate, or with a tissue homogenizer; extraction with petroleum ether, ethyl ether, hexane, or a mixture of polar and apolar solvents; partitioning into acetonitrile or dimethyl formamide; redissolving in an apolar solvent followed by Florisil column cleanup. All of these require much time, involve many pieces of glassware and consequently suffer surface adsorption losses in transferring from one container to another.

Differences in DDTR residues in green alfalfa, hay, and cubes from the same source

During the period 1964-68, when DDT use in Arizona was declining because of high residues found in forage, alfalfa hay buyers and growers alike were having residue analyses conducted on their products by commercial laboratories. In the process some of the more curious alfalfa growers submitted 2 samples for analysis, one hay and the other hay cubes collected at the same time from the same field. The analytical results usually indicated substantial differences between the two. Consequently we have frequently been asked, why the difference?

DDT Volatization from desert and cultivated soils

In a previous report (Ware et al. 1975) of simulated field studies we explained the need for information relative to DDT movement from soil in the vapor phase and referenced a rather complete set of studies relating to its volatility as well as that of DDE. This report expands that study to real field conditions of an uncultivated desert plot and an irrigated cotton field, for 52and ll-week degradation studies, respectively.