Both residential and recreational areas are likely to provide access for exposure. Contaminated soil can be brought into homes on the feet of family members and pets.
Suspended soil particulates in outdoor air can also enter a house through indoor-outdoor air exchange. A young child playing on the floor will have the maximum opportunity both for ingestion and for dermal exposure to soil and dust accumulated on the floor. Exhibit 5 illustrates how exposure doses via ingestion of soil can be estimated and provides some default soil intake rates for various age groups. Assume the person is on site 5 days per week, 50 weeks per year, for 30 years. First calculate the exposure factor:.
As a health assessor, you must acknowledge the potential for exposure by dermal absorption of chemicals from contaminated soil 5. Dermal absorption of contaminants from soil or dust depends on the area of contact, the duration of contact, the chemical and physical attraction between the contaminant and the soil, and the ability of the contaminant to penetrate the skin.
Chemical-specific factors, such as lipophilicity, polarity, volatility, molecular weight, and solubility also affect dermal absorption. For most exposure scenarios, ATSDR generally considers dermal exposure to be a minor contributor to the overall exposure dose relative to contributors from ingestion and inhalation.
Many organic chemicals bind to organic matter in soil, and are therefore not readily available for absorption by the skin.
In addition, only the fraction of the contaminant that is in direct contact with the skin is amenable to absorption. Therefore, the ability of a soil contaminant to be dermally absorbed depends on the diffusion of the contaminant through the soil matrix. A soil-specific factor involved in dermal absorption is adherence. Many uncertainties exist for estimating the amount of soil that will adhere to the skin, making it very difficult to recommend a default value.
Adherence depends on soil properties, the part of the body exposed to the soil, and the type of activity being performed during soil contact EPA Site- and exposure-specific conditions should therefore be considered where possible. Default soil adherence values may be found in the following text box. Young children 2. Young children would have an increased exposure frequency because they tend to retain soil on their skin after coming indoors.
Adults would have a decreased exposure frequency because they tend to have less time to be exposed to outdoor soil EPA Exhibit 6 illustrates how soil dermal absorbed doses can be estimated and provides default dermal exposure values. As the health assessor, you should also consider the inhalation of dusts from contaminated soils. In both children and adults, the dose of a soil contaminant that results from oral ingestion is likely to exceed the dose resulting from dust inhalation Hawley However, for contaminated dusts, chemicals that have specific toxic effects on the respiratory tract e.
When there is a special concern about a contaminant in dust, the air inhalation Exposure Dose Equation Exhibit 7 in Section 3. Inhalation is an important pathway for human exposure to contaminants that exist as atmospheric gases or are adsorbed to airborne particles or fibers. Inhalation exposure to contaminants from hazardous waste sites can occur as a result of direct release of gases and particles from an on-site facility, volatilization of gases from contaminated soils or water bodies, or resuspension of dust and particles from contaminated soil surfaces.
When assessing exposure to atmospheric gases, generally, the estimation of inhaled dose is not necessary. The doses in the toxicological literature are reported as concentrations that can be directly compared to concentrations measured at a site. Inhalation rates are taken into account when studying dose-response relationships and in developing the screening values. Exhibit 7 illustrates how inhalation exposure doses can be estimated and provides default air intake rates.
Dermal exposure to some air contaminants could also result in absorption through the skin. However, data are not likely to be available to quantitatively estimate exposures from this pathway. Nevertheless, you should acknowledge potential exposure pathway for air contaminants that can be readily absorbed through the skin.
Assessment of the human health risk from ingestion of contaminated food requires information on the quantities of contaminated foodstuffs consumed and the extent of contamination present in foodstuffs. The most reliable method of assessing the extent of human exposure to contaminants in food is direct measurement of concentrations in foodstuffs. Such measurements should be conducted on foodstuffs prepared for consumption or portions of contaminated plants and animals that are representative of those portions used as food.
If the food chain appears to be a significant pathway for human exposure and the appropriate information on contaminant levels is not available, that lack of information should be explicitly identified in the public health assessment and a recommendation should be made that the appropriate information be obtained. Estimation of exposure dose through food chains requires knowledge of the consumption rate of specific food items in the human diet. You should be aware that consumption rates of the population in the vicinity of a hazardous waste site may differ considerably from national average consumption rates.
For example, regional consumption rates of beef may vary widely from national averages. Consumption rates of subpopulations within the contaminated area may also vary significantly from the national averages. For example, people such as American Indian or Alaska Natives who subsist on fish from a primary source would likely have an increased consumption rate. When local consumption patterns are available and are different from national averages, they should be used in the calculations to determine exposure doses.
Most commonly, as a health assessor, you are concerned about exposures from consuming fish that have bioaccumulated a substance found in surface water or sediment. Typically, you will assume that all fish consumed are caught from one contaminated water body. Exhibit 8 illustrates how fish ingestion exposure doses can be estimated. If the exposed population is consuming fish from multiple sources, however, the equation presented in Exhibit 9 should be used.
As a conservative estimate, this example does not consider contaminant reduction due to cooking. Cooking fish prior to eating can reduce the levels of some substances.
You can review scientific literature to identify how cooking may affect the substance under evaluation. The fish intake rate is a daily average, so the exposure factor is equal to 1.
To calculate the exposure dose:. In the case of residential soil contamination, the consumption rate of homegrown foods and local wild plants is also of interest. To estimate the total daily intake of a particular contaminant that may bioaccumulate in multiple foodstuff, daily intakes of contaminants from all affected foodstuffs should be considered.
Exhibit 9 illustrates how food ingestion exposure doses can be estimated. The following example illustrates the calculation of the food ingestion exposure dose for cadmium through garden crop contamination. Thus, the daily human exposure dose of cadmium from contaminated garden produce in this example is estimated to be 0. Estimates should be confirmed, as necessary, by a local consumption survey.
Andelman JB. Inhalation exposure in the home to volatile organic contaminants of drinking water. Science of the Total Environment Dec; June , Atlanta, Georgia. Code of Federal Regulations Much of the chemical characteristics information contained in the database for radionuclides is similar to that for chemicals. Therefore, this discussion focuses on the sources and definitions of the radionuclide toxicity values.
In the radionuclide portion of the database, toxicity values for ingestion, inhalation, and external exposure are presented. In all cases, the only values presented are those for carcinogenesis i. If a RfD for a radionuclide is needed, the user should access the RfD for the inorganic chemical in the nonradionuclide portion of the database.
For example, the radionuclide portion of the database contains ingestion, inhalation, and external exposure slope factors for each uranium isotope e. This value is contained in the nonradionuclide portion of the database.
These values were derived by ORIA using methods for estimating radiogenic cancer risks. For some radionuclides, two sets of slope factors are presented. It should be noted that a slope factor for dermal contact is not included in the radionuclide portion of the database.
These have not included because they are not available, and EPA has concluded that dermal uptake is generally not an important route of uptake for radionuclides RAGS, The only additional chemical-specific parameter contained in the radionuclide portion of the database that is not contained in the nonradionuclide portion of the database is radioactive half-life T R. This value is provided to assist the risk assessor determine the importance of radioactive decay and daughter ingrowth in the risk evaluation.
The Risk Assessment Information System. Toxicity Values 1. Introduction 2. Chemical Information 2. Radionuclide Information 1. The database contains two levels of organization these are: Nonradionuclides--defined in this database as chemicals that do not undergo nuclear decay and emit ionizing radiation.
For example, the inorganic chemicals calcium, carbon, manganese, and iron are nonradionuclides. In addition, the organic compounds trichloroethene, carbon tetrachloride, etc. The nonradionuclide information provided in the database is discussed in Section 2. Radionuclides--defined in this database as chemicals that do undergo nuclear decay and emit ionizing radiation.
For example, the isotopes of uranium, uranium U , uranium U , and uranium U are radionuclides. Radionuclide information provided in the database is discussed in Section 3. These categories are: Inorganic chemicals--defined as chemicals or compounds that do not contain a carbon skeleton. For example, manganese, mercury, and iron are inorganic chemicals.
Organic compounds--defined as chemicals or compounds that do contain a carbon skeleton. For example, trichloroethene, benzo a pyrene, and acetone are organic compounds. Toxicity information that is available in the database includes: Chemical name--the common name of the chemical or compound. Synonyms are not included in the database. Cancer slope factor --for those chemicals which are carcinogens, the oral slope factor, inhalation slope factor, and dermal slope factor are provided.
Date withdrawn --the date which a toxicity value was withdrawn by EPA, if applicable. For withdrawn values, the most recent value prior to withdrawal is included in the database. Other chemical-specific information that is available in the database includes: Volatilization factor VF --an estimate of the rate at which a chemical is emitted from soil as a vapor. Soil saturation concentration C sat --an estimate of the maximum concentration of a chemical that may exist in soil before free product is present.
Gastrointestinal absorption factor GIAF --an estimate of the rate at which a chemical or compound is absorbed from the gastrointestinal tract of a human. Dermal absorption factor ABS --an estimate of the rate at which a chemical is partitioned between the skin and a solid medium such as soil.
Permeability constant K p --an estimate of the rate at which a chemical is partitioned between the skin and water. Henry's Law Constant H --an estimate of the extent of chemical partitioning between air and water and equilibrium. A larger value indicates that the chemical is more likely to volatilize. Molecular weight MW --the weight of the chemical.
Organic carbon partition coefficient Koc --an estimate of the extent of chemical partitioning between organic carbon and water at equilibrium. A larger value indicates that the chemical is more likely to remain bound to soil or sediment.
Octanol-water partition coefficient Kow --an estimate of the extent of chemical partitioning between water and octanol at equilibrium. A larger value indicates that the chemical is more likely to partition to octanol and, by analogy, more likely to be bioconcentrated in aquatic organisms.
Oral chronic RfD--the RfD used with administered oral doses under chronic exposures i. Oral subchronic RfD--the RfD used with administered oral doses under subchronic exposures i. Inhalation chronic RfD--the RfD used with inhalation doses under chronic exposures to estimate the potential of a systemic toxic effect. Hayley Australian. Natasha Australian. Veena Indian. Priya Indian.
Neerja Indian. Zira US English. Oliver British. Wendy British. Fred US English. Tessa South African. How to say mgkg in sign language? Select another language:.
Please enter your email address: Subscribe. Discuss these mgkg definitions with the community: 0 Comments. Notify me of new comments via email.
0コメント