Dermal toxicology

Health and Safety. The dermal toxicology of alkaline solutions of thioglycolic acid has been reviewed extensively (63—65). The reagent has been found harmless to normal skin when used under conditions adopted for cold waving. Some irritation is observed on abraded skin but this appears to be associated with the alkaline component of the waving solution (65). Hand protection is recommended for the professional hairdressers who routinely handle these products. 

The skin is the primary organ of contact between the organism and its environment. There is extensive commercial interest in dermal toxicology and safety screening because of the many different products used topically for therapeutic and cosmetic purposes. Similar comments can be made about ocular products. 

Toxicology. The acute oral and dermal toxicity of naphthalene is low with LD q values for rats from 1780—2500 mg/kg orally (41) and greater than 2000 mg/kg dermally. The inhalation of naphthalene vapors may cause headache, nausea, confusion, and profuse perspiration, and if exposure is severe, vomiting, optic neuritis, and hematuria may occur (28). Chronic exposure studies conducted by the NTP ia mice for two years showed that naphthalene caused irritation to the nasal passages, but no other overt toxicity was noted. Rabbits that received 1—2 g/d of naphthalene either orally or hypodermically developed changes ia the lens of the eye after a few days, foUowed by definite opacity of the lens after several days (41). Rare cases of such corneal epithelium damage ia humans have been reported (28). Naphthalene can be irritating to the skin, and hypersensitivity does occur. 

Toxicology. The nitroparaffins have minimal effects by way of actual contact. There were neither systemic effects nor irritation in dermal studies in rabbits. Human exposure of a prolonged or often-repeated nature has led to low grade irritation attributable to removal of oil from the skin, an effect produced by most organic solvents. Eye irritation potential of all four nitroparaffins has been deterrnined in rabbits. Other than a transient slight redness and some lachrymation, no effects were noted. The average Draize score was 0.0. The acute oral toxicity, LD q, of all four nitroparaffins has been deterrnined in the rat (Table 8). 

Toxicological Information. The toxicity of the higher olefins is considered to be virtually the same as that of the homologous paraffin compounds. Based on this analogy, the suggested maximum allowable concentration in air is 500 ppm. Animal toxicity studies for hexene, octene, decene, and dodecene have shown Httle or no toxic effect except under severe inhalation conditions. The inhalation LD q for 1-hexene is 33,400 ppm for these olefins both LD q (oral) and LD q (dermal) are >10 g/kg. 

Toxicology. Isoquinoline is a poison when ingested or injected intraperitoneally. Even in cases of skin contact it is moderately toxic. As in the case of quinoline, its vapors are irritating to the eyes, nose, and throat. Exposure causes headaches, dizziness, and nausea. Rapid absorption through the skin makes it a dangerous chemical. Its toxicity is oral LD q (i t)> mg/kg, and dermal LD q (rabbit), 590 mg/kg (65,66,182,183). 

The dermal adsorption of DEBT in humans has been studied in the Netherlands by appHcation of DEBT as undiluted technical material or as 15% solutions in alcohol. Labeled material was recovered from the skin, and absorption of DEBT was indicated by the appearance of label in urine after two hours of skin exposure. About 5—8% of the appHed treatments was recovered as metaboHtes from urine, and excretion of metaboHtes in the urine came to an end four hours after exposure ended. DEBT did not accumulate in the skin, and only a small (less than 0.08%) amount ended up in feces. Curiously, less has been absorbed through skin from 100% DEBT appHcation (3—8%, mean of 5.6%) than from 15% alcohol appHcation (4—14%, mean of 8.4%). These results have been described as consistent with previous absorption/metaboHsm studies using guinea pigs, rats, and hairless dogs. Other pubHcations on DEBT toxicology have been cited (92). 

Physicochemical properties requked include melting/boiling point, vapor pressure, solubiUty, and flammabiUty/explosion characteristics. The toxicological studies include acute toxicity tests, oral, inhalation, and dermal skin and eye kritation skin sensiti2ation subacute toxicity, oral, inhalation, and dermal and mutagenicity tests. In vitro reverse mutation assay (Ames test) on Salmonella typhimurium and/or E.scherichia coli and mammalian cytogenic test. In vivo mouse micronucleus test. 

Indicators of toxicity hazards include LD50, LC50, plus a wide range of in vitro and in vivo techniques for assessment of skin and eye indtation, skin sensitization, mutagenicity, acute and chronic dermal and inhalation toxicity, reproductive toxicology, carcinogenicity etc. 

A study of the dermal toxicokinetics of methyl parathion in female rats, sponsored by ATSDR, is being conducted at the University of Mississippi Medical Center. The principal investigator is Dr. Ing K. Ho, Department of Pharmacology and Toxicology, 500 North State Street, Jackson, Mississippi 39216-4505. 

Palmer JS. 1978. Toxicologic evaluation of a microencapsulated formulation of methyl parathion applied dermally to cattle. Am J Vet Res 39 429-431. 

EPA. 1990a. Endosulfan Review of four toxicology studies and three dermal absorption studies. Memorandum. Washington, DC U.S. Environmental Protection Agency, Office of Pesticides and Toxic Substances. Document no. 007937. 

Much toxicological data are available on this red pigment acute oral toxicity in mice, 90-day subchronic toxicological study, acute dermal irritation and corrosion, acute eye irritation and corrosion, anti-tumor effectiveness, micronucleus test in mice, AMES test Salmonella typhimurium reverse mutation assay), estimation of antibiotic activity, and results of estimation of five mycotoxins. A new patent on Arpink Red was filed in 2001 with claims of anti-cancer effects of the anthraquinone derivatives and apphcations in the food and pharmaceutical fields. 

Prah, J., Ashley, D., Blount, B., Case, M., Leavens, T., Pleil, J., and Cardinali, F., Dermal, oral, and inhalation pharmacokinetics of methyl tertiary butyl ether (MTBE) in human volunteers, Toxicological Sciences, 77, 195-205, 2004. 

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