Paraquat absorption

Despite a 3-fold range in follicle area in the marmoset, no differences in absorption rates of paraquat, mannitol, water, and ethanol were observed between different body sites (Scoll et al., 1991). However, among the different species examined in this study, there was an 80-fold range in follicle area, which correlated with observed differences in the rate of mannitol and paraquat absorption. The authors concluded that this correlation was only possible with relatively slowly ab.sorbed le.st penetrants, such as paraquat and mannitol. Further work is needed to determine to what extent unique anatomical features at different body sites play a role in absorption and penetration of both lipophilic and hydrophilic pesticides. 

Newhouse M, McEvoy D, Rosenthal D (1978) Percutaneous paraquat absorption. An association with cutaneous lesions and respiratory failure. Arch Dermatol 114 1516-1519 Gamier R, Chataigner D, Efthymiou ML, Moraillon I, Bramary F (1994) Paraquat poisoning by skin absorption report of two cases. Vet Human Toxicol 36 313-315 Nishioka K, Asagami C, Kurata M, Fujita H (1983) Sensitivity to the weed killer DNA-nitralin and cross-sensitivity to dinitrochlorobenzene. Arch Dermatol 119 304-306 English JS, Rycroft RJ, Calnan CD (1986) Allergic contact dermatitis from aminotriazole. Contact Dermatitis 14 255-256... 

Diquat and paraquat are quaternary ammonium compounds largely used as contact herbicides and crop desiccants. When systemic absorption occurs, paraquat and diquat are rapidly distributed into the body. Paraquat primarily accumulates in the lungs and kidneys, while the highest diquat concentrations have been found in the gastrointestinal tract, liver, and kidneys (WHO, 1984). Urine is the principal route of excretion for both diquat and paraquat, which are primarily eliminated as unmodified compounds. Occupationally exposed workers can be monitored by measuring paraquat and diquat concentrations in urine samples (Table 6). Blood concentrations are useful to monitor acute poisoning cases. 

In terrestrial plants, paraquat s action is at the point of local absorption (Anonymous 1963). Characteristic damage signs to susceptible species include wilting and general collapse in herbaceous plants. Regrowth may occur in some perennial plants, but in resistant species temporary scorch may be the most marked effect (Anonymous 1963). In sugarcane (Saccharum officinarum), paraquat... 

Smith, J.G. 1988a. Paraquat poisoning by skin absorption a review. Human Toxicol. 7 15-19. 

Tanaka, R., S. Fujisawa, and K. Nakai. 1981. Study on the absorption and protein binding of carbaryl, dieldrin and paraquat in rats fed on protein diet. Jour. Toxicol. Sci. 6 1-11. 

Holmstedt (1959) and Brown and Muir (1971) have reviewed perocular absorption of pesticides. More recently, Sinow and Wei (1973) have shown that the quartemary herbicide paraquat can be lethal to rabbits if applied directly to the surface of the eyes. Parathion, in particular, is exceedingly toxic when administered via the eye, a concern that must be kept in mind for the protection of pesticide applicators. 

Several studies indicate the special nature of the dodecyl chain in interactions with a variety of biomembranes Zaslavsky s (7 ) data on the haemolysis caused by alkyl ethers, our own data (10 ) on the absorption of paraquat by gastric mucosa,... 

PARAQUAT AND DIQUAT Granular preparations usually contain 2.5% of paraquat md 2.5% of diquafi liquid preparations may contain 20% wA of p aquat only. Treatment consists of reducing p aquat absorption by administering copious noimts of file adsorbents Fuller s Earth or bentonite, with cathartics. Active elimination techniques (forced diuresis, haemodialysis, charcoal haemoperfusion) may also be applied. 

It is clear that under in vitro assay conditions, anthocyanins can function as antioxidants. However, in vivo, anthocyanin absorption appears to be low. In animal models, dietary anthocyanins at relatively high doses (1 to 2 mg/kg diet) are protective against oxidative stress induced in a number of models, including ischemia reperfusion, paraquat, CCL4, and t-BHP. In humans, anthocyanins appear to have some vasopro-tective effects, but whether these are the result of antioxidant mechanisms is not clear. It appears that in most of the studies reviewed, the dose of anthocyanins was well above that which might be normally consumed in the diet with natural foods, except for perhaps one study in which 1 cup of blueberries was consumed for 30 days and small increases in plasma antioxidant capacity were observed." ... 

Gorsline, J. Okerholm, R.A. Rolf, C.N. Moos, C.D. Hwang, S.S. Comparison of plasma nicotine concentrations after application of nicoderm (nicotine transdermal system) to different skin sites. J. Clin. Pharmacol. 1992,32, 576-581. Wester, R.C. Maibach, H.I. Bucks, D.A.W. In vivo percutaneous absorption of paraquat from hand, leg and forearm of humans. J. Toxicol. Environ. Health 1984, 14, 759-762. Taskovich, L. Shaw, J.E. Regional differences in the morphology of human skin correlation with variations in drug permeability. J. Invest. Dermatol. 1978, 70, 111. Roberts, M.S. Eavretto, W.A. Meyer, A. Reckmann, M. Wongseelashote, T. Topical bioavailability of methyl sahcy-late. Aust. N.Z. J. Med. 1982, 12, 303-305. 

Figure 7. Ultraviolet absorption spectra of pyridine, nicotine (in ethanol), paraquat, ana diquat (in water)...

Paraquat has low but rapid gastrointestinal absorption (5-10%) and low skin absorption. Peak plasma concentrations occur in less than 2 h following ingestion. Generally, paraquat is not metabolized to any large extent. In animal studies, metabolites have been detected in urine, possibly resulting from the action of intestinal microflora. Paraquat is actively... 

Pesticide uses Exemplars Paraquat and Diquat Absorption Human toxicity respiratory system Herbicides Atrazine, cyanazine Inhalation, ingestion, dermal, occular Skin, eyes, cornea, liver, kidneys, respiratory system, gastrointestinal tract... 

Figure 10.20. The wavelength range for light absorption by dissolved and clay-sorbed paraquat, compared with the wavelength "window" of the atmosphere. The shaded area denotes overlap of these two ranges, and gauges the potential for photodecomposition.

This list may be lengthened when the effects of adsorption are considered, because a molecule bound on a surface may be activated for photodegradation even if the reaction is not favorable for the same molecule dissolved in solution. For example, paraquat apparently photodecomposes more rapidly when adsorbed on layer silicate minerals than when in solution (Helling et al., 1971). This phenomenon may be related to the fact that adsorption on clay shifts the UV absorption band of paraquat to longer wavelength (256 - 275 nm) and closer to the atmospheric window for UV light (see Figure 10.20). In other words, adsorption on clay increases the probability that paraquat will absorb UV radiation and thereby decompose. 

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