Bioavailability dermal absorption

Bioavailability from Environmental Media. Oral absorption of DIMP from water was found to be rapid in both the rats and minks (Bucci et al. 1992). Dermal absorption of DIMP in swine was reported to be between 3 and 7% through 7 days (Snodgrass and Metkler 1992). However, no studies were located regarding the bioavailability of diisopropyl methylphosphonate from other environmental media. Studies that investigate the bioavailability of diisopropyl methylphosphonate from soils would be useful in estimating exposure of persons who live near the RMA. 

Bioavailability from Environmental Media. Case reports of people who have experienced cresol poisoning following oral and dermal exposure indicate that all cresols can be absorbed by these routes (Cason 1959 Chan et al. 1971 Green 1975). However, no information is available regarding oral or dermal absorption of cresols located in water, soil, or plant material. Studies in animals have shown that cresols can be absorbed from contaminated air by inhalation but have not attempted to... 

Information on toxic effects of acute-duration exposure to PBBs by routes other than oral are limited to data on hepatic, renal, dermal, and ocular effects of inhalation and dermal exposure in rats or rabbits (Millischer et al. 1980 Needham et al. 1982 Norris et al. 1975a Waritz et al. 1977), but these data may not be reliable due to study limitations and possible delayed lethality. Quantitative data for inhalation and dermal absorption of PBBs are lacking. Studies of inhalation and dermal absorption following exposure to soil containing PBBs (i.e., bioavailability studies) would be useful for assessing risk at a hazardous waste... 

Bioavailability from Environmental Media. Inorganic tin is not well absorbed after inhalation, oral, and dermal exposure. Organotins are somewhat better absorbed by both the inhalation and oral routes, but dermal absorption is not considered important (Hiles 1974 Mori et al. 1984). The daily intakes of tin from air, food, and water are small (WHO 1980). Studies on the availability of tin compounds from soils would be useful in assessing human exposure from ingesting contaminated soils. Further study of human intake of organotin compounds from food and water would also be useful. 

TCDD (Koshakji et al. 1984). Also, limited information is available on the bioavailability from fly ash (Van den Berg et al. 1983, 1985). 2,3,7,8-TCDD can be adsorbed following dermal contact (Banks and Bimbaum 1991 Poiger and Schlatter 1980 Shu et al. 1988) however, dermal absorption of... 

When exposed to mixtures, chemicals in the exposure medium may affect each other s uptake by humans in a manner that is analogous to some of the bioavailability effects outlined here for environmental species. This was, for instance, shown for the neurotoxicity of EPN (O-ethyl-O-4-nitrophenyl phenylphosphono-thionate), which was enhanced by aliphatic hydrocarbons due in part to increased dermal absorption (Abou-Donia et al. 1985). It was also shown that dietary zinc inhibits some aspects of lead toxicity, which could in part be explained by decreasing dietary lead absorption (Cerklewski and Forbes 1976). Other examples of interactions of chemicals at the uptake phase in humans, which may in part be related to bioavailability interactions, are summarized in Table 1.3. 

This chapter provides an overview of factors affecting dermal absorption. Factors influencing absorption are among others related to the skin (e.g. anatomical site, difference between species, metabolism, etc.) and the exposure conditions (e.g. area dose, vehicle, occlusion and exposure duration). In order to provide relevant information for the risk assessment of pesticides, dermal absorption studies should take these aspects into account. With respect to the methods being used nowadays for the assessment of dermal absorption, it is important to realize that neither in vitro nor in vivo animal studies have been formally validated. Available data from various in vitro studies, however, indicate that the use of the total absorbed dose (i.e. the amount of test substance in the receptor medium plus amount in the skin) could be used in a quantitative manner in risk assessment. Tape stripping of the skin can be adequate to give a good indication of test chemical distribution, and hence its immediate bioavailability. 

Bioavailability from Environmentai Media. Occupational studies on the uptake of vanadium via the inhalation route exist however, data suggesting that this route is relevant with regard to hazardous waste sites are lacking. Dermal absorption data are limited, however it is likely that absorption via this route is low since vanadium, like other metals, has low solubility in lipids (WHO 1988). The primary concern regarding uptake of vanadium in the vicinity of contaminated waste sites is ingestion, particularly of contaminated food, soil, or water by children playing in the area (Byrne and Kosta 1978 Vouk 1979). However, sufficient animal data exist to indicate that absorption of vanadium via this route is limited (Conklin et al. 1982 Roshchin et al. 1980) Confirmation of this conclusion by human data would be helpful, especially since children may absorb more than adults. 

For occupational exposure to vapor, a respiratory rate of 1.3 m /hour and a bioavailability of 0.75 were assumed. For dermal absorption, a skin absorption rate of 0.2 mg/cnr/hour and a skin surface area of 1,000... 

Chapters 4, 5, and 6 cover human exposure to arsenic ingestion, inhalation, and dermal absorption. Metabolism of arsenic in the body depends on the chemical species of arsenic absorbed. Association of arsenic in human urine is the most suitable biomarker to assess exposure to arsenic. Risk characterization and bioavailability of arsenic upon soil ingestion is critically evaluated. Arsenic occurrence in the United States is compared to that in Taiwan for health implications. Factors that may interfere with arsenic removal during water treatment, as well as significant diurnal and seasonal variations in arsenic concentration in U.S. surface water supplies, are thoroughly discussed. 

Both of these approaches allow for assessment of systemic absorption by not conducting complete mass balance studies (e.g., expired air to catch absorbed compound metabolized to COj or HjO expired end products). In vivo dermal absorption studies not taking into account other routes of excretion must be interpreted with caution. One extension of this mass balance excretory analysis is to assess dermal absorption by only monitoring the primary excretory route for the compound studied. Dermal bioavailability has been assessed in exhaled breath using real-time ion trap mass spectrometry to track the uptake and ehmination of compounds (e.g., trichloroethylene) from dermal exposure in humans and rats (Poet et al., 2000). A physiologically based pharmacokinetic model can be used to estimate the total bioavailability of compoimds. The same approach was extended to determine the dermal uptake of volatile chemicals imder non-steady-state conditions using real-time breath analysis in rats, monkeys, and humans (Thrall et al., 2000). 

Klienfeld and Tabershaw 1954 Prout et al. 1985 Stephens 1945 Stevens et al. 1992 Templin et al. 1993 Withey et al. 1983), or dermal (Bogen et al. 1992 Jakobson et al. 1982 McCormick and Abdul-Rahman 1991 Sato and Nakajima 1978 Steward and Dodd 1964 Tsuruta 1978) exposure. All these routes of exposure may be of concern to humans because of the potential for trichloroethylene to contaminate the air, drinking water, food, and soil. More information on the absorption of trichloroethylene following ingestion of contaminated soil and plants grown in contaminated soil near hazardous waste sites are needed to determine bioavailability of the compound in these media. 

Bioavailability from Environmental Media. Additional information on absorption following dermal contact with, or ingestion of, contaminated soil and water would also be helpful in determining the importance of this route of exposure for populations of concern. 

Bioavailability from Environmental Media. Inhalation studies of humans indicate that -hcxane is bioavailable from the atmosphere. Although -hexane in water or soil is likely to undergo transport to the air because of its volatility (although this would not necessarily be the case with -hexanc in groundwater), pharmacokinetic absorption studies using the oral and dermal routes of exposure would help clarify the bioavailability of -hexane from water, soil, plant material, and other environmental media. 

Bioavailability from Environmental Media. No information was found regarding the absorption of di- -octylphthalate by humans or laboratory animals following inhalation or dermal exposures. No information is available about absorption following oral exposure in humans. However, indirect evidence from animal studies suggests that the compound is readily absorbed by this route (Albro and Moore 1974 Oishi 1990). Additional information is needed on the absorption of di- -octylphthalate as a result of inhalation of contaminated air, ingestion of contaminated food and water, and dermal contact with contaminated soils and sediments. 

Bioavailability from Environmental Media. Available information regarding the rate of disulfoton absorption following inhalation, oral, or dermal contact has been discussed in the Toxicokinetics section (see Section 2.3). Although no data on disulfoton s bioavailability from contaminated air are available, the bioavailability from inhalation exposure is expected to be high because disulfoton is likely to be present in the vapor phase (Eisenreich et al. 1981) and not in the particulate phase in the adsorbed state. Similarly, no data on the bioavailability of disulfoton from water and soil or plant material are available however, disulfoton adsorbs rather strongly to soil (Harris 1969 Helling et al. 1974 Wauchope et al. 1992). Since the part that remains adsorbed to soil or sediments may, at most, be partially bioavailable, disulfoton is expected to have reduced bioavailability from soil and water. Data on the bioavailability of disulfoton from actual environmental media need further development. 

Bioavailability from Environmental Media. Information on absorption by humans and other animal species indicates that it is well absorbed via the oral and dermal routes (DiVincenzo et al. 1977, 1978). 2-Hexanone has also been demonstrated to be well absorbed by humans and animals following inhalation exposure (DiVincenzo et al. 1978). Information on its bioavailability from contaminated soils would be useful in assessing the risk from exposure to this medium by populations in the vicinity of hazardous waste sites. 

Bioavailability from Environmental Media. Carbon tetrachloride can be absorbed following inhalation, oral, or dermal exposure. No data were located regarding the potential effects of environmental media (air, water, soil) on the absorption of carbon tetrachloride. Flowever, since soil adsorption is considered to be relatively low for carbon tetrachloride, it seems unlikely that soil would have a significant effect on its bioavailability. Additional studies are needed to determine the extent of bioavailability from contaminated air, drinking water, and soil at hazardous waste sites. 

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