Exposure, routes

The toxicity of common acryhc monomers has been characterized in animal studies using a variety of exposure routes. Toxicity varies with level, frequency, duration, and route of exposure. The simple higher esters of acryhc acid are usually less absorbed and less toxic than lower esters. In general, acrylates are more toxic than methacrylates. Data appear in Table 5. 

Ha2ard is the likelihood that the known toxicity of a material will be exhibited under specific conditions of use. It follows that the toxicity of a material, ie, its potential to produce injury, is but one of many considerations to be taken into account in assessment procedures with respect to defining ha2ard. The following are equally important factors that need to be considered physicochemical properties of the material use pattern of the material and characteristics of the environment where the material is handled source of exposure, normal and accidental control measures used to regulate exposure the duration, magnitude, and frequency of exposure route of exposure and physical nature of exposure conditions, eg, gas, aerosol, or Hquid population exposed and variabiUty in exposure conditions and experience with exposed human populations. 

Contains the health hazards and risks, toxicological data, and first aid procedures Exposure routes and limits signs and symptoms target organs and medical conditions aggravated by exposure. 

Aetual or potential hazards Possible exposure routes... 

Skin is also important as an occupational exposure route. Lipid-soluble solvents often penetrate the skin, especially as a liquid. Not only solvents, but also many pesticides are, in fact, preferentially absorbed into the body through the skin. The ease of penetration depends on the molecular size of the compound, and the characteristics of the skin, in addition to the lipid solubility and polarity of the compounds. Absorption of chemicals is especially effective in such areas of the skin as the face and scrotum. Even though solid materials do not usually readily penetrate the skin, there are exceptions (e.g., benzo(Lt)pyrene and chlorophenols) to this rule. 

Many of the factors that influence the c.xtcnt of contamination are site specific, cither climatic or hydrogeological. Other factors that influence the extent of contamintition relate to land surface features such as topography or dcNclopmcnt, which determine exposure routes. Additional important... 

To determine acceptable contaminant levels in soils, two primary exposure routes are usually considered (1) inlialation of gases, vapors, or airborne particulate emanating from the site, and (2) ingestion of contamimtted drinking water. Other routes that can contribute to e.xposure include absorption of pollutants tluough direct skin contact and uptake of wtiter or soil contantinants by plants that are part of the food chain. 

The exceeded value for children via the environment from exposure to dioctyltin (356% of the TDI) relates to the consumption of local produce close to a PVC processing plant and largely derives from default values on release to the environment. Further refinement of this exposure assessment is currently under way. Until this is clarified, dioctyltin remains a compound of concern via this exposure route for children. 

Absorption, Distribution, Metabolism, and Excretion. Evidence of absorption comes from the occurrence of toxic effects following exposure to methyl parathion by all three routes (Fazekas 1971 Miyamoto et al. 1963b Nemec et al. 1968 Skiimer and Kilgore 1982b). These data indicate that the compound is absorbed by both humans and animals. No information is available to assess the relative rates and extent of absorption following inhalation and dermal exposure in humans or inhalation in animals. A dermal study in rats indicates that methyl parathion is rapidly absorbed through the skin (Abu-Qare et al. 2000). Additional data further indicate that methyl parathion is absorbed extensively and rapidly in humans and animals via oral and dermal routes of exposure (Braeckman et al. 1983 Flollingworth et al. 1967 Ware et al. 1973). However, additional toxicokinetic studies are needed to elucidate or further examine the efficiency and kinetics of absorption by all three exposure routes. 

Other additional studies or pertinent information that lend sunnort to this MRL Methyl parathion affects the nervous system by inhibiting acetylcholinesterase activity. Cholinesterase inhibition and neurological effects have been observed in humans and animals, for all exposure routes and durations (for example. Dean et al. 1984 Desi et al. 1998 EPA 1978e Gupta et al. 1985 Nemec et al. 1968 Suba 1984). 

Intravenous administration of endosulfan (7 3 ratio of a- and P-isomers) in rabbits produced slower elimination of the a-isomer (Gupta and Ehrnebo 1979). Excretion of the two isomers occurred primarily via the urine (29%) with much less excreted via the feces (2%). Given the earlier evidence in rats and mice describing the principal route of elimination of endosulfan and its metabolite to be via the feces, the differences in the excretion pattern in this study may be attributable to differences in exposure routes, to species differences, or to both. Nevertheless, studies in laboratory animals suggest that both renal and hepatic excretory routes are important in eliminating endosulfan from the body. Elimination of small doses is essentially complete within a few days. 

Bioavailability from Environmental Media. Endosulfan can be absorbed following inhalation of contaminated workplace air and ingestion of insecticide-contaminated food (Ely et al. 1967). Dermal contact with or ingestion of endosulfan that is tightly bound to soil particles is an exposure route of... 

Route Dependent Toxicity. The toxicity of trichloroethylene does not seem to be heavily dependent upon its route of entry. Inhalation and ingestion are the primary exposure routes, and the liver, heart, and central nervous system are the primary targets for both routes (Candura and Faustman 1991). Renal toxicity results principally from oral exposure, and dermal exposure generally confines its toxic effects to the skin, although broad systemic effects can be induced imder conditions of high exposure (Bauer and Rabens 1974). Attributing such effects solely to dermal exposure, however, is difficult because inhalation exposure is often a factor in these cases as well. 

To derive an MRL, ATSDR generally selects the most sensitive endpoint which, in its best judgement, represents the most sensitive human health effect for a given exposure route and duration. ATSDR cannot make this judgement or derive an MRL unless information (quantitative or qualitative) is available for all... 

Peech Cherewyk K. 2002. Methyhnercury bioaccumulation in zooplankton an assessment of exposure routes and accumulation in newly flooded reservoirs. MS thesis. University of Manitoba, Winnipeg, Canada, 90 p. 

Data should show pesticide occurrence and dissipation in important matrices during the study period (Figure 1). This has been extensively covered in other articles and will not be elaborated here. Exposure routes should be characterized well enough to quantify the dosages that are experienced by nontarget organisms. This is often... 

Exposure routes would be ingestion and inhalation of dust. Even so, the dose rates that would be received by these pathways are very low (Murray and Avogadro 1979). 

Exposure route Clinical diagnostic tests and treatment... 

Mineral Oil Hydraulic Fluids. Studies regarding cancer in humans or animals after inhalation exposure to mineral oil hydraulic fluids were limited to a single case-control study that examined associations between subjectively reported occupational exposure to petroleum-derived liquids and cancer at particular sites among 3,726 male cancer patients (Siemiatycki et al. 1987a). The study found no convincing associations between occupational exposure to hydraulic fluids and cancer at any site. This study is discussed in more detail in Section 2.2.3.8, because, while inhalation exposure was probable for the subject occupations, the authors reported that the exposure route was more often dermal contact. 

Exposure route Area residents Site visitors Terrestrial Aquatic... 

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