Exposure Assessment. An exposure assessment evaluates how much of a specific substance a receptor may ingest, inhale, or absorb through the skin over a specified time period. This section describes the potential receptors and exposure pathways selected for quantitative risk characterization. Exposure assumptions (or factors), equations used to estimate doses for the selected receptors, and methods used to derive exposure point concentrations (EPCs) are also described. The methodology for exposure point concentrations utilized in this risk assessment applies to both current and future land use. For purposes of this risk assessment, both current and future land use are described by the exposure parameters chosen in the following sections.
4.1 Exposure Setting and Land Use Xxxxxxx Field was operated as a NAS by the U.S. Military beginning on its date of commission in April 1933. The base was designated for closure as an active military base under the U.S. Department of Defense Base Realignment and Closure (BRAC) program. Currently, the building and facilities are used as described below (HLA, 2000a; Xxxxxxx ESE, 2001b,c): • Buildings are used by NASA and other federal agencies for administration, research support, storage, base support services, retail, motor pool operations, or are vacant. • Dormitories and administrative buildings associated with the Space Camp Operations are present in the western portion of the site; however, because of their location relative to the contamination, they are not included further in this HHRA. • Hangar 1 is used for special events, and houses a museum of the former NAS Xxxxxxx Field. The buildings immediately adjacent to Hangar 1 are vacant. • In the areas adjacent to the airfield, buildings are used for office operations, air traffic control, or are vacant. A large portion of these areas (Parcel 19) have been identified as a habitat area for burrowing owls, a California species of special concern, and will not be developed.
4.2 Identification of Receptors and Pathways Pathways of exposure are the means through which an individual may contact a chemical. Determinants of complete exposure pathways include environmental/geographic considerations, locations and activity patterns of the potentially exposed populations, and the potential for a chemical to migrate within a particular medium (e.g., air transport) or from one medium to another (e.g., release of particulates from soil to air). Each of the fo11owing components must be present for an expo...
Exposure Assessment. Task 2.1 will identify potential climate change effects on the Marin coast, using OCOF outputs to integrate wind, wave and surge conditions into an exposure assessment, including factors such as water levels, wave heights, flooding, and erosion. Specific OCOF assets that will be used include a seamless Digital Elevation Model derived from recent LIDAR and multibeam bathymetry, a suite of 40 dynamic coastal flooding projections in 25cm increments with four storm scenarios ranging from daily to 100-year return levels. OCOF’s interactive maps overlays and a user-friendly interface will be used to help convey the results to promote public understanding. Additionally, we will share our experience with the Coastal Storm Modeling System (CoSMoS) models used in the OCOF tool to assist those who are applying these models in other areas throughout the state. The Exposure Assessment will also explicitly address three additional aspects of sea level rise risk:
Exposure Assessment. DDE in Maternal and Cord Blood
Exposure Assessment. The exposure indicators must be representative of the population’s average exposure to air pollution. Therefore, a discussion with the people in charge of the measuring network in the city can help select the relevant monitoring stations. The hourly or daily data collected for each station must be averaged to give an estimate of global pollution. The indicator should be as close as possible to the one used in the epidemiological studies from which the CRFs are derived. Rarely are series of data complete, i.e., without any missing values. To substitute missing values we propose a method that works using the available data. . Finally, when performing an HIA simultaneously on different cities, the indicators should be calculated using the same protocol for all cities to be able to add the results for each city together and to compare results between cities.
Exposure Assessment. The objectives of an exposure assessment are to identify actual or potential exposure pathways, to characterize the potentially exposed populations, and to determine the extent of the exposure. Exposed populations may include industrial workers, residents, and subgroups that comprise a meaningful portion of the general population, including, but not limited to, infants, children, pregnant women, the elderly, individuals with a history of serious illness, or other subpopulations, that are identifiable as being at greater risk of adverse health effects due to exposure to hazardous materials than the general population.
Exposure Assessment. The EPA’s Wildlife Exposure Factors Handbook (EPA, 1993) was the primary source of exposure factors data. Table 24 lists the factors used for each receptor and the source of the data provided. BSAFs and BAFs used in the RI were reevaluated along with new values and final values are presented in Table 25. Bioaccumulation regression models from oak ridge national labatory (ORNL) and the ecological soil screening levels (EcoSSLs), which are available in Table 26, were used as appropriate. Other factors were reevaluated or refined as specified in Step 3 of the XXXX process under CERCLA. The exposure to upper trophic level organisms was assessed by quantifying the daily dose of ingested contaminated food items (that is, plant and animal) and ingested media. Exposure to receptors was estimated using chemical-specific Exposure Point Concentrations (EPCs), bioaccumulation data, and several other factors such as species-specific body weights, ingestion rates, home range data, and area use factors. Prey tissue concentrations were estimated using chemical-specific bioaccumulation factors and bioaccumulation regression models. Site-specific tissue data were not available. Instead, tissue concentrations were modeled using literature data. Benthic invertebrates were evaluated for direct toxicity to COPECs in sediment. EPCs were compared directly to media screening levels. Fish tissue concentrations used in modeling ingestion by piscivorous birds were modeled using biota sediment accumulation factors. It was assumed that the fish from which these BSAFs were developed were from the same trophic level as those expected in the diets of piscivorous birds feeding adjacent to the Site. Initial EPCs were established as maximum detected concentrations. 95% UCLs were only calculated for those COPECs for which risk estimates using maximum concentrations indicated risk. For those COPECs suggesting risk based on maximum detected concentrations, 95% UCLs were calculated using the most recent version of ProUCL. The final list of COPECs and EPCs used for the risk evaluation is presented in Tables 27 and 28 for soil and sediment, respectively. For a handful of COPECs, EPCs were further refined to mean concentrations when 95% UCLs indicated risk. Mean concentrations were considered a reasonable exposure point concentration because, assuming available food sources and cover are equal throughout the exposure area, receptors would not spend a greater percent of their foraging time at any on...
Exposure Assessment. 1. Dietary exposure from food and feed uses. In evaluating dietary exposure to triflusulfuron-methyl, EPA considered exposure under the petitioned-for tolerances as well as all existing triflusulfuron-methyl tolerances in 40 CFR 180.492. EPA assessed dietary exposures from triflusulfuron-methyl in food as follows:
i. Acute exposure. Quantitative acute dietary exposure and risk assessments are performed for a food-use pesticide, if a toxicological study has indicated the possibility of an effect of concern occurring as a result of a 1-day or single exposure. No such effects were identified in the toxicological studies for triflusulfuron-methyl; therefore, a quantitative acute dietary exposure assessment is unnecessary.
ii. Chronic exposure. In conducting the chronic dietary exposure assessment, EPA used the food consumption data from the USDA 1994– 1996 and 1998 Continuing Surveys of Food Intakes by Individuals (CSFII). As to residue levels in food, EPA utilized tolerance-level residues and 100 percent crop treated (PCT) for all commodities.
iii. Cancer. EPA determines whether quantitative cancer exposure and risk assessments are appropriate for a food- use pesticide based on the weight of the evidence from cancer studies and other relevant data. Cancer risk is quantified using a linear or nonlinear approach. If sufficient information on the carcinogenic mode of action is available, a threshold or non-linear approach is used and a cancer RfD is calculated based on an earlier noncancer key event. If carcinogenic mode of action data are not available, or if the mode of action data determines a mutagenic mode of action, a default linear cancer slope factor approach is utilized. Based on the data summarized in Unit III.A., EPA has concluded that the use of the chronic RfD is considered protective of potential carcinogenicity for risk assessment purposes.
iv. Anticipated residue and PCT information. EPA did not use anticipated residue and/or PCT information in the dietary assessment for triflusulfuron-methyl. Tolerance level residues and/or 100 PCT were assumed for all food commodities.
2. Dietary exposure from drinking water. The Agency used screening level water exposure models in the dietary exposure analysis and risk assessment for triflusulfuron-methyl in drinking water. These simulation models take into account data on the physical, chemical, and fate/transport characteristics of triflusulfuron-methyl. Further information regarding EPA drinking water model...
Exposure Assessment. The qualitative and/or quantitative evaluation of the likely intake of biological,chemical and physical agents via abalone.
Exposure Assessment. Exposure assessment describes the exposure pathway or pathways for a chemical hazard and estimates total intake. For some chemicals, intake may be associated with a single food. For others the residue may be present in multiple foods, as well as in drinking water, and sometimes in household products, such that food accounts for only a portion of total exposure. For chemicals, exposure assessment often uses values at certain points on the continuum of exposure, such as the mean. Such point estimates are referred to as deterministic models. Some exposure models are emerging, such as for intake of pesticide residues, that takes into account the distribution of food consumption by a population. These models, generally called probabilistic, provide more details on the distribution of exposed consumers, but are not inherently more accurate than deterministic models. If the level of exposure as determined by the exposure assessment is lower than the ADI or TDI, the chemical in foods is within safe limits.
Exposure Assessment. A food-chain exposure pathway model up to the point of consumption is developed for the hazard so that a human dose-response curve can be used to generate estimates of risk (Fig. 7.3). 4 Note that many natural toxins such as mycotoxins and marine toxins need insight into biology as well as chemistry for their risk assessment. 60 Farm Xxxxxxxxx and dressing Processing Retail Home
