Body surface area exposure

Elevated trichloroethylene levels in expired air were measured in subjects who immersed one hand in an unspecified concentration of trichloroethylene for 30 minutes (Sato and Nakajima 1978). Guinea pigs, exposed to dilute concentrations of aqueous trichloroethylene (-0.020 to 0.110 ppm) over a majority of their body surface area for 70 minutes, excreted 59% of the administered dose in the urine and feces 95% of the metabolized dose was excreted in 8.6 days (Bogen et al. 1992). No other studies were located for humans or animals regarding excretion after dermal exposure to trichloroethylene. 

Dermal (skin) contact with sulfur mustard agents causes erythema and lesions (blistering), while contact with vapor may result in first and second degree burns contact with liquid typically produces second and third degree chemical burns. Any burn area covering 25 percent or more of the body surface area may be fatal. Respiratory contact is a dose-related factor in the sense that inflammatory reactions in the upper and lower airway begin to develop several hours after exposure and progress over several days. 

The National Research Council (NRC) published a report, Science and Judgment in Risk Assessment, that critiqued the current approaches to characterizing human cancer risks from exposure to chemicals. One issue raised in the report relates to the use of default options for assessing of cancer risks. These general guidelines can be used for risk assessment when specific information about a chemical is absent. Research on 1,3-butadiene indicates that two default options may no longer be tenable Humans are as sensitive as the most sensitive animal species and the rate of metabolism is a function of body surface area rather than inherent species differences in metabolic capacity. 

Treatment of psoriasis should be limited to once-daily application not to exceed 20% of total body surface area. Adverse local effects include a burning or stinging sensation (sensory irritation) and peeling, erythema, and localized edema of the skin (irritant dermatitis). Potentiation of photosensitizing medication may occur, and patients should be cautioned to minimize sunlight exposure and to use sunscreens and protective clothing. 

The Department considers the protocols used in the Durham and Wolfe (6) study as quite useful guides however, the percentage of the body reported as exposed in that study is considered as underreported unless impervious clothing is worn. The Department usually considers the skin on the entire body to be subject to some exposure. We use data from two articles as references for determining total body surface area one by Berkow and Amboy ( 7), and another by DuBois and Dubois (j6). ... 

Because of differences in physiology, behaviours, body weight, and body surface area, the exposure levels in children may be different from and often higher than exposures in adults. Furthermore, in terms of risk, children may also be more susceptible to environmental pollutants because of differences in absorption, metabolism, and excretion. More information is needed about the behavioural and cultural factors that will influence the exposure to chemicals in children. Such factors may modify both the levels of exposure to chemicals and the nature and severity of health risks. Future studies must include in their analysis consideration of factors such as occupation, smoking, socioeconomic status, and nutritional conditions. 

Physiological factors Those factors that are key to deriving expressions of exposure, such as standard reference values for body weights, body surface areas, life expectancy, working lifetime and inhalation rates (Norman, Ch. 10). 

When using animal inhalation e.xpcrimcnts to estimate lifetime human risks for partially soluble vapors or gases, the air concentration (ppm) is generally considered to be the equivalent dose between species based on cqui alcnt exposure times (measured as fractions of a lifetime). For inhalation of particulates or completely absorbed gases, the amount absorbed per unit of body surface area is considered to be the equivalent dose between species. 

The skin and eyes are especially sensitive to the toxic effects of sulfur mustard. When applied to human skin, about 80% of the dose evaporates and 20% is absorbed (Vogt et al., 1984). About 12% of the amount absorbed remains at the site and the remainder is distributed systemically (Renshaw, 1946). Doses up to 50 pg/ cm cause erythema, edema, and sometimes small vesicles. Doses of 50-150 pg/cm cause bullous-type vesicles, and larger doses cause necrosis and ulceration with peripheral vesication. Droplets of liquid sulfur mustard containing as little as 0.0025 mg may cause erythema (Ward et al., 1966). Eczematous sensitization reactions were reported in several early studies and may occur at concentrations below those causing direct primary irritation (Rosenblatt et al., 1975). In humans, the LCtso (estimated concentration x exposure period lethal to 50% of exposed individuals) for skin exposures is 10,000 mg-min/m (DA, 1974) (for masked personnel however, the amount of body surface area exposed was not reported). The ICt 50 (estimated concentration x exposure period incapacitating to 50% of exposed individuals) for skin exposures is 2000 mg-min/m at 70-80°F in a humid enviromnent and 1000 mg-min/m at 90°F in a dry enviromnent (DA, 1974, 1992). The ICtso for contact with the eyes is 200 mg-min/m (DA, 1974, 1992). The LDl for skin exposure is 64 mg/kg and the LD50 is estimated to be about 100 mg/kg (DA, 1974,1992). 

When data are insufficient to determine the relative susceptibility of animals in comparison to humans, a UF of 10 has been used by EPA, ATSDR, Health Canada, WHO, the International Programme on Chemical Safety (IPCS), and Rijksinstituut voor Volksgesondheid en Milieu (RIVM) when developing the equivalent reference doses for chronic exposure to chemicals (Dourson et al 1996). When extrapolations are made from animals to humans based on milligrams per kilogram of body weight, the factor of 10-fold is usually adequate to account for differences in response. Dourson and Stara (1983) found that a factor of 10 accounted for many of the animal-to-human differences observed when the dose was adjusted for differences between human and animal body weights and body-surface areas. 

Hakkinen PJ, Kelling CK, and Callender JC (1991) Exposure assessment of consumer products Human body weights and total body surface areas to use, and sources of data for specific products. Veterinary and Human Toxicology 33 61-65. 

MCA poisoning by ingestion, inhalation or exposure of more than 5% of the body surface area is frequently lethal. The symptoms of poisoning are not immediate they can appear between 1 and 4 hours after exposure. The non-corrosive sodium salt does not penetrate the skin and is not toxic by skin contact (unlike MCA, which passes through the skin very easily). It is, on the other hand, highly toxic by the oral route. There are no data available on the parenteral administration of MCA in humans. In laboratory animals. 

In 1990, urine samples from an accidental laboratory exposure to sulfur mustard were obtained (Jakubowski et al., 2000). The erythematous and vesication areas of the individual were estimated to be less than 5% and 1%, respectively, of the total body surface area. The assay measured both free and conjugated TDG using GC-MS (Jakubowski et al., 1990). The maximum TDG urinary excretion rate was 20 (pg/day on day 3. TDG concentrations of 10 ng/mL or greater were observed in some samples for up to a week after the exposure. A first-order elimination was calculated from days 4 through 10 and found to be 1.2 days. A great deal of intraday variability was noted for the TDG urine concentrations. Attempts were made to estimate the total amount of sulfur mustard on the skin of the patient. The estimate was based on two assumptions (1) that the assay for the free and conjugated TDG represents approximately 5% of the total amount of sulfur mustard related products in the blood, and (2) that the bioavailability factor from skin to blood is 10. A total of 0.243 mg of TDG was recovered over a 2 week period. This would represent 4.86 mg in the blood or 48.6 mg on the skin. 

The drying here is achieved by means of exposing the product to the surface area of the jacketed vessel. The jacket is a shell of metal (usually carbon steel) welded onto a stainless steel vessel body. This design can include a heated shaft for increased surface area exposure. The heat transfer medium used here is generally steam, hot oil, or hot water. Ports must be provided so as to vent the evaporated vapors being removed from the product. 

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