Absorption Of Chemicals Research Articles

Cleaning protective apparel to reduce pesticide exposure.

Each year 1.04 billion kg of pesticides are used to control insects, weeds, fungi, and other pests in the United States (Wasserstrom and Wiles 1985). Human pesticide exposure continues to be a problem for those who use these chemical tools. The three routes of pesticide entry into the human body are respiratory, dermal, and oral. Dermal absorption has been shown to account for 87% of the total human pesticide exposure (Wolfe 1973; Gold et al. 1982; Maibach et al. 1971). Dermal exposure involves the absorption of toxic chemicals through the skin where they are disseminated throughout the body via the blood (Niles 1985).

Preventing percutaneous absorption of industrial chemicals: the "skin" denotation.

Percutaneous absorption has received comparatively little attention in occupational health, although this route of entry has repeatedly caused occupation-related intoxications. In practice, the evaluation of skin penetration rates is far from simple. Much evidence has been obtained from studies of chemicals used for cosmetics and topical therapeutics, but the information available on compounds encountered in occupational health is limited. The data obtained from experimental studies have confirmed that the concentration, type of vehicle, skin area, skin condition, and extent of occlusion are important factors in determining the degree of percutaneous absorption, but no general model has been developed. Also, too little is known about the basic chemical properties governing the rate of penetration. Thus, prediction is difficult and bound to be rather inaccurate. Current preventive practice follows the procedure used by ACGIH and is mainly based on a "skin" denotation in official listings of chemicals to which exposure limits have been allocated. The number of substances and groups of chemicals which have received skin denotation in 17 selected countries varies between 24 and 179 and a total of 275 are listed as a skin hazard in one or more countries; ACGIH lists 143. Thus, the denotation practice varies. As an unfortunate result of these discrepancies and the dichotomy of skin denotation, the absence of skin denotation may erroneously indicate that efforts to protect the skin are unnecessary. Thus, an evaluation of skin penetration potentials should be incorporated in occupational health practice as a supplement to the official denotations.

Skin penetration and metabolism of topically applied chemicals in six mammalian species, including man: An in vitro study with benzo[a]pyrene and testosterone

Percutaneous absorption of chemicals is generally considered a diffusional process, with the rate-limiting barrier being the nonviable stratum corneum. Because viable skin possesses enzyme activities, including those involved in the metabolism of xenobiotics, the extent to which cutaneous metabolism may influence the percutaneous fate of topically applied chemicals in the skin was examined in mammalian skin maintained as short-term organ cultures. Skin samples from mouse, rat, rabbit, guinea pig, marmoset, and man were examined. The results from studies with benzo[a]pyrene (BP) and testosterone showed that, in all species, metabolic viability was a major factor involved in the in vitro skin permeation of surface-applied chemicals. Permeation was accompanied by extensive cutaneous “first pass” metabolism; both parent compounds and a full spectrum of metabolites were found in the receptor fluid from viable skin preparations. However, in previously frozen nonviable skin preparations, essentially only unchanged parent compounds were detected in the receptor fluid. Permeation of BP and testosterone was highest in mouse skin, and significant species variations in the metabolite profiles were observed. Studies with mouse skin also demonstrated that induction of cutaneous drug-metabolizing enzymes can result in a two- to threefold increase in the in vitro permeation of topical BP, and a significant reduction in permeation was observed when KCN was added to the perfusion medium. These results indicate that diffusional and metabolic processes are intimately involved in the percutaneous fate of surface-applied chemicals. The relative importance of these processes is dependent upon the physicochemical properties of the compounds and the metabolic capabilities of the skin toward the compounds in question. Furthermore, these findings suggest that meaningful in vitro studies on skin absorption should consider both diffusion and cutaneous biotransformation of the applied compound.

Organophosphate Insecticide (Famphur) Topically Applied to Cattle Kills Magpies and Hawks

A systematic field study of a black-billed magpie (Pica pica) population revealed that magpies and red-tailed hawks (Buteo jamaicensis) were killed by famphur (=famophos, Warbex?) used as a pouron to control cattle warbles (Hypoderma sp.). Magpie mortality began on treatment day and continued for more than 3 months (38 found dead); mortality peaked between Day 5 and Day 13. Estimates of magpie density (based on transects) decreased in both the control and treatment areas, but the decrease was greater in the treatment area. A red-tailed hawk found dead on Day 10 had eaten a famphur-contaminated magpie. Another red-tailed hawk was found alive but immobilized, and a third died outside the study area. Brain cholinesterase (ChE) activity was 70-92% depressed in all dead birds examined; famphur residues were detected in all 17 magpies and the 2 hawks analyzed. The amount of famphur obtained by the dead magpies was estimated at 5.2-6.1 mg/kg (based on residue concentrations in the gizzard), which was above the acute oral LD, for several bird species. The cow hair portion (12%) of the pooled gizzard contents from 13 other dead magpies produced extremely high famphur residues (4,600 ppm). The residues persisted on cattle hair for more than 90 days post-treatment. Magpie populations in the far western states declined between 1968 and 1979, which corresponds with widespread use of famphur, although other factors may be involved. J. WILDL. MANAGE. 49(3):648-658 Organophosphate (OP) insecticides are now used extensively in agriculture. The topical use of famphur (O,O-dimethyl O-[p-(dimethylsulfamoyl)phenyl] phosphorothioate) in the autumn as a systemic insecticide for control of warbles in cattle was recommended in 1970 (Every et al. 1970). Famphur can be administered to livestock dermally as a pour-on (the only method we observed), orally (mixed with feed), or by intramuscular injection (Ivey et al. 1976). The larvae are killed within the animal during the autumn before they develop into grubs the following year. Grubs emerging on the backs of untreated cattle during the spring may be eaten by magpies (Bishopp et al. 1926), but this is not an adequate control. Observations of magpies dying after famphur use on cattle were reported by ranchers as early as 1973 (unpubl. data, Oreg. Dep. Fish and Wildl., La Grande). Magpies and other species of birds were found dead after cattle were treated with famphur in the United Kingdom (Felton et al. 1981). Magpie brain ChE activity was severely depressed and famphur was identified in the gizzard contents. Another organophosphate (fenthion), also used as a pouron to control Hypoderma larvae in cattle, was implicated in magpie mortality in Canada (Hanson and Howell 1981). Despite relatively rapid degradation in the environment and tissues of homeotherms, some OP insecticides are highly toxic to wildlife for varying periods of time after application (Zinkl et al. 1978, White et al. 1979). The degree of exposure of nontarget wildlife species to OP insecticides can be assessed by measuring ChE activity in tissues and blood (Bunyan et al. 1968, Ludke et al. 1975, Hill and Fleming 1982). The depression of brain ChE activity by 20% or a decrease of 2 SD in wild birds (relative to species baseline data or concurrent controls) has been used as a co servative criterion to indicate absorption of OP chemicals. Depression of brain ChE activity by >50% and confirmation of suspected OP residues in tissues or ingesta are criteria for cause-effect diagnosis of death in birds exposed to anti-ChE chemicals. We studied a magpie population that lived on or near seven ranches where 535 cattle were treated with Warbex? (13.2% famphur). Warbex? was poured along the back line of the cattle at the recommended rate of 0.326 ml/kg body weight, not to exceed 118 ml/animal. The field study was prompted by: (1) reported magpie mortality in Oregon and the United Kingdom; (2) a magpie population decline in the far

The pulmonary uptake, accumulation, and metabolism of xenobiotics.

Researchers now recognize that the lungs are a site for the uptake, accumula­ tion, and/or metabolism of numerous endogenous and exogenous, or xenobiot­ ic, chemicals and various aspects of these pulmonary processes have recently been reviewed 0-8). Much of the impetus for studying the uptake and metabo­ lism of xenobiotics by lungs is due to their intimate contact with both blood and the external environment and their sensitivity to many chemicals that selective­ ly cause pulmonary damage (9). The lungs have two important characteristics that facilitate the absorption of airborne or blood-borne chemicals. First, the venous drainage from virtually the entire body perfuses through the alveolar­ capillary unit, which has an extensive capillary endothelium. Second, the alveolar epithelial and endothelial layers are very thin to facilitate gas ex­ change. Such an architectural arrangement, which places the epithelial layers in close contact with the blood, allows rapid absorption of unionized lipophilic xenobiotics and metabolism and/or transfer to the circulation. One important function of lung is to regulate the systemic concentration of biologically active endogenous compounds by selective removal or metabo­ lism. Certain polypeptides (6), prostaglandins (7), and vasoactive amines (8) in venous blood are handled in this manner. Pulmonary endothelial cells are important in the regulation of circulating hormones (10), and consequently it is not surprising that certain xenobiotics, which have physicochemical properties

Four animal models for predicting percutaneous absorption of chemicals in man

Four animal models for predicting percutaneous absorption of chemicals in man

Review of Industrial Chemical Exposure: Guidelines for Biological Monitoring

Abstract Traditionally, industrial hygienists have sought to prevent excessive exposure to chemicals in industry by setting standards for concentrations of chemicals in ambient air. Standards for chemicals in air applied by the American Conference of Governmental Industrial Hygienists include: the maximum allowable concentration (MAC), the threshold limit value (TLV), and the emergency exposure limit (EEL). However, the monitoring of air concentrations only considers exposure by inhalation and is not indicative of the actual uptake or total body burden of chemicals by exposed workers. During the past 20 years numerous procedures have been developed for the analysis of industrial chemicals in biological specimens collected from workers. Such biological monitoring takes into consideration absorption of chemicals by all routes of absorption and differences in individual exposures. The goal of biological monitoring is to detect excessive exposure in workers before the occurrence of detectable adverse health effects.

In vitro penetration and absorption of chemicals into the ovine hoof

Techniques are described for testing the ability of chemicals to penetrate through ovine hoof horn. Most chemicals tested had penetration rates of less than 0.1 mm per hour and formalin, a chemical widely used for treatment of foot rot, penetrated very poorly (less than 0.02 mm per hour). Chloramphenicol in ethanol solution gave the highest penetration rate (0.21 to 2.38 mm per hour) and other penetrative chemicals were zinc sulphate (0.06 to 0.58 mm per hour), copper sulphate (less than 0.05 to 0.38 mm per hour) and sodium azide (less than 0.05 to 0.24 mm per hour) in aqueous solution. Inclusion of sodium lauryl sulphate in treatments enhanced the penetration rates of zinc and azide approximately sixfold. Ethanol and nickel ammonium hydroxide also improved the penetration of zinc and azide, particularly through the hard horn from the abaxial wall of the claw. Absorption of zinc from solutions containing 10 per cent zinc sulphate gave hoof tissue concentrations of zinc from 0.22 to 0.88 mg zinc ions per g tissue (10 to 20 times that found in normal hoof samples) and most of this zinc was retained after the horn was washed continuously in running water for 24 hours.

Absorption, biotransformation, and excretion of environmental chemicals.

Foreign chemicals are continually present in the environment of man and animals. Mammalian systems are in a constant state of balance-the intake compensated for by the outflow. The intake is largely determined by the route of exposure and the chemical characteristics of the environmental compound. Under normal conditions of exposure to small or moderate amounts of environmental chemicals, the system is capable of biotransforming and detoxifying such materials into compounds more easily handled by the mammalian system. These are largely converted to more water-soluble materials and excreted in the urine, bile, and less commonly through other excretory routes. In situations of massive exposure to foreign materials, or when repeated exposure to moderate amounts of chemicals results in accumulation in body systems, toxicoses may result. These are essentially an overwhelming of the biological mechanisms for detoxifying and excreting such materials. The hazard associated with environmental chemicals is greatly increased if a preexisting disease modifies the normal biological detoxification processes. Therapy to assist intoxicated individuals is largely aimed at increasing excretory processes and maintaining or restoring the physiological balance between the amount of environmental chemical absorbed and the level capable of being excreted.

Intestinal Absorption and Metabolism of Xenobiotics

There are five possible processes of intestinal absorption of xenobiotics. These are active transport, passive diffusions, pinocytosis, filtration through “pores,” and lymphatic absorption. The passive diffusion is major process for transport of foreign chemicals across the intestine. Though the lymphatic absorption of drugs is not of any major therapeutic significance, the uptake of toxic chemicals such as 3-MC, benzpyrene, and DDT through lymphatics may enhance their toxicity, since they are distributed to other organ systems in the body without being metabolized by liver. A number of factors such as diet, motility of intestine, interference with gastrointestinal flora, changes in the rate of gastric emptying, age of the animal, and dissolution rate of xenobiotic can alter the rate of absorption of chemicals. Liver is the major site of metabolism of xenobiotics, but the contribution of intestinal metabolism of xenobiotic can influence the overall bioavailability of chemicals. The xenobiotic metabolizing enzymes located in endoplasmic reticulum of intestine possess biochemical characteristics similar to that of liver. In general, the rate of metabolism of xenobiotics by intestinal microsomal preparation is lower than that observed with similar hepatic microsomal preparations. The in vitro intestinal metabolism of xenobiotics is affected by several factors including age, sex, diurnal variations, species, and nutritional status of the animal. The intestinal xenobiotic metabolizing enzymes are stimulated by the pretreatment of animals with foreign chemicals, but this depends on the route of administration of chemicals, drug substrate and the animal species used. Rabbit intestinal drug metabolizing enzymes seem to be resistant to induction by foreign chemicals.

Use of high-performance liquid chromatography to separate very small quantities of radio-labelled metabolites from biological tissue

In order to study the absorption, metabolism and tissue distribution of chemicals in cattle ticks Amblyomma variegatum, a method of separating and recovering metabolites in picogram quantities was required. A high-performance liquid chromatographic system has been investigated for this purpose, using tritium-labelled amitraz and some potential metabolites. Separation was carried out on Nucleosil 5 μm NO 2 bonded phase. Interchangeable pre-columns were used to extend the range of compounds which could be separated in one run and to keep the main column free of radioactive contamination. Amitraz, 2,4-dimethylaniline and 2,4-dimethylformanilide were eluted from the column quantitatively without the addition of unlabelled carrier, down to quantities of 0.75 pg, 0.78 pg and 1.60 pg, respectively. Apparatus for automated collection of the column eluate in scintillation vials and a method for data processing are described.

Composition and Ultrastructure of Leaf Cuticles From Fruit Trees, Relative to Differential Foliar Absorption

Differential foliar absorption of chemicals by peach, apple and orange was related to cuticle thickness, weight, surface wax and embedded wax content and to surface wax wettability, ultrastructure and composition. Surface wax concentration, especially on abaxial leaf surfaces, correlated well with resistance to foliar absorption. The abaxial surface wax on peach leaves was built up in layers around and over the guard cells (which are preferred paths of spray entry into leaves) whereas apple and orange guard cells were relatively wax-free. Peach surface waxes were more difficult to wet than orange waxes and, although more polar than orange waxes, may be more resistant to water penetration as they were rich in hydrocarbons and triterpenoids. Enhancement of foliar absorption may require improved partitioning of sprays through the surface waxes or the bypassing of the waxes via stomatal penetration.

Effects of High Humidity on Translocation of Foliar-applied Labeled Compounds in Plants. II. Translocation from Starved Leaves

Absorption and translocation of chemicals by cotton leaves are greatly increased under conditions of high humidity. This enhanced movement consists of increased phloem transport and induced uptake into and transport via the xylem. Studies with starved and normal leaves prove that phloem transport is greatly reduced in leaves depleted of carbohydrate reserves; starvation has no effect upon the xylem transport induced by high humidity. The relation of high humidity to herbicide usage is discussed. 15 references, 6 figures.

Epidermal and Dermal Reactions in a Case of Sensitivity to Nickel

For many years I have supported the assumption of a dual sensitivity in contact dermatitis, namely, the existence, in principle, of an “epidermal” vesicular and of a “dermal” papular type of sensitivity. This concept is based mainly on the observations that in some instances of contact dermatitis, as well as in patch tests, the pathological changes are predominantly in the epidermis and in others mostly in the dermis. The concept of a dual sensitivity originated with Rocksted (1), Sulzberger (2), Haxthausen (3), and others; it has been supported by Miescher (4), W. Jadassohn (5), and Darabos (6). Such an interpretation is oversimplified. Some investigators, notably Wm. Epstein and Kligman (7) and Inderbitzin (8), have strong objections. It is not clear what role the epidermis plays in contact sensitivity. Contact sensitivity apparently originates in the lymph nodes (Frey and Wenk (9)), and is transferred to the skin by lymphocytes. The skin is assumed to be the site of the formation of the complete antigen (hapten-pro-tein complex), but this is not definitely proven. Even if this is the case, some authors believe that the preponderance of epidermal or dermal changes is mainly due to differences of absorption and penetration of various chemicals.

A Study of the Absorption and Translocation of Several Chemicals in Johnson Grass, and an Evaluation of Their Effectiveness for Its Control under Field Conditions

A Study of the Absorption and Translocation of Several Chemicals in Johnson Grass, and an Evaluation of Their Effectiveness for Its Control under Field Conditions

Preliminary Study of the Penetration of Sodium Arsenite and Sodium Monochloroacetate Solutions into Trunks of Yellow Birch and Red Spruce

1. A study was made of the penetration of sodium arsenite and sodium monochloroacetate solutions through the exposed surface of the sapwood into the trunks of yellow birch (Betula lutea Michx. f.) and red spruce (Picea rubens Sarg.) trees. 2. The absorption of either chemical into spruce tended to decrease with time toward an equilibrium value which occurred in about 5 days. In addition, there was a diurnal fluctuation, with a slower rate occurring during the late-evening and early-morning hours. 3. Both chemicals showed an inverse relation between absorption into spruce and concentration. The tested concentrations of sodium arsenite penetrated more slowly than corresponding concentrations of sodium monochloroacetate. 4. Acid solutions of sodium monochloroacetate were taken up by red spruce faster than alkaline solutions. 5. A seasonal variation in absorption rate was observed for both chemicals in spruce. There was a sharp maximum in absorption on June 4, followed by a rapid decrease from mid-June through mid-July, followed by another peak in late July and early August. 6. No absorption of either solution was observed for yellow birch until after the cessation of bleeding, which occurred abruptly on May 26, when the leaves were half expanded. 7. The absorption of chemicals did not occur so readily in yellow birch as in red spruce. High concentrations of treating chemicals resulted in a net outward movement of water from the birch tree into the reservoirs.

Effect of topical agents on planter sweating.

THE SWEAT gland of the sole is uniquely protected from external forces. A relatively immense keratinous barrier cushions physical and chemical trauma, and the absence of the pilosebaceous apparatus insures minimal absorption of chemicals and drugs. Because of these exceptional anatomic considerations, it is impossible to include the plantar sweat gland in any generalization regarding the dermatology therapeutic effect of topical agents or measures. Relatively little experimental data have appeared in the literature regarding the effects of topical measures and medicaments on the normal sweat gland of the soles in man. 1 Accordingly, the present study was initiated to obtain further information on this point.

Deaths from poisoning, Massachusetts, 1938-1948.

A CONSIDERABLE number of deaths are caused annually by poisoning — absorption of gaseous, liquid or soluble chemicals. The mortality of deaths from poisoning exceeds, at present, that of all infect...

Selective absorption of sulphur-35 by fungus-infected leaves.

IT has been shown that fungi and higher plants absorb and accumulate fungicidal substances to a high degree1–3; but, so far as we are aware, no quantitative demonstration of selective absorption of therapeutic chemicals by parasitized tissues of plants or animals has been reported. The successful therapeutic use of sulphur vapours against external powdery mildews and internal rusts4 suggested that these infections would be suitable for the study of selective absorption of a fungicide.

Absorption of Tri-brom Ethanol through the Skin

IN connexion with a study on absorption of various drugs and chemicals through the intact skin of different animals, an interesting observation was made in this laboratory. It was found that tri-brom ethanol readily penetrates the intact skin of such small animals as rats and mice and produces its characteristic narcotic effects.