EPA-Expo-Box (A Toolbox for Exposure Assessors)
Data on ingestion rates are available in EPA’s Exposure Factors Handbook: 2011 Edition as indicated below. Exposure factors related to ingestion exposures are also described in the Food, Aquatic Biota, Water and Sediment, Soil and Dust, and Consumer Products Modules in the Media Tool Set of EPA-Expo-Box.
- Chapter 3 — Ingestion of Water and Other Liquids
- Chapter 4 — Non-Dietary Ingestion Factors
- Chapter 5 — Ingestion of Soil and Dust
- Chapters 9 through 15 — provide information on food intake, including intakes of fruits and vegetables; fish and shellfish; meats, dairy products, and fats; grain products; home-produced foods; total food; and human milk.
Water and food intake rates are typically estimated from dietary intake surveys. Water ingestion rates and food ingestion rates in Chapters 3 and 9–13 of the Handbook are provided as per capita and/or consumer-only data. Per capita rates include all survey participants whether or not they reported intake during the survey period. Consumer-only rates exclude individuals who did not ingest the water or food from the source during the survey period. Per capita intake, therefore, represents an average across the entire population of interest, but does so at the expense of underestimating consumption for the subset of the population that consumed the water or food in question.
The Exposure Factors Tab of the Indirect Estimation Module provides links to data on ingestion rates.
Food and water ingestion rates can vary by type of food, source of food or water, and receptor (U.S. EPA, 2011).
- Type of food – Intake rates can be defined by individual food types, such as beef, fish, carrots, and apples, or by categories of foods, such as total vegetables, total fruits, above ground produce, or root vegetables. Another potential type of food is human milk, relevant for only one lifestage.
- Source of food – Intake can vary by the source of food. For example, the Handbook provides different intake rates for fruits and vegetables for the general population versus individuals who produce their own fruits, vegetables, and meats. Similarly, fish intake rates are presented for the general population, recreational anglers, and Native American populations. Consumption of home-grown fruits or vegetables by people who garden is another exposure scenario commonly evaluated. These scenarios could involve different types of food and different rates of consumption depending upon seasonal availability so it could be important to consider quantities of foods consumed on a seasonal basis.
- Source of water – Consumption rates of drinking water are needed if the exposure scenario, for example, involves ingesting water from community water sources or a well with contaminated groundwater. The consumption of drinking water from surface water sources might also be of concern unless treatment of the water mitigates contamination.
- Receptor – Intake rates might differ across different populations. For this reason, EPA presents intake rates for different age groups, races, and ethnic groups. It is important to select exposure values that are appropriate for the particular population of concern. For example, the general population of the United States may be of interest in some assessments, but others may focus on certain subsets of the population (e.g., farmers, recreational anglers).
Mouthing behavior and soil/dust ingestions rates account for inadvertent soil/dust ingestion, particularly in children, as a result of “hand-to-mouth” or “object-to-mouth” activities in which objects (including fingers) are touched by or put into the mouth resulting in incidental exposure. Adults may also be exposed by ingesting soil that adheres to food or objects that have been handled. Exposure factor data for this category include separate values for adults and children (U.S. EPA, 2011).
- Source – Ingestion rates may differ depending upon the source (e.g., indoor dust, outdoor soil).
- Soil-pica and geophagy – Inadvertent ingestion of soil should be differentiated from soil-pica and geophagy. Soil-pica is the recurrent ingestion of unusually high amounts of soil. Geophagy is the intentional ingestion of earths and may be associated with cultural practices. Central tendency estimates for soil ingestion for individuals 1 year of age and older are 50 mg/day. It is estimated that soil-pica behavior can result in ingestion of 1,000 mg/day, and geophagy behavior can result in ingestion of 50,000 mg/day. Soil-pica and geophagy are considered uncommon events and represent the high end of exposures.
Ingestion rates should be selected to represent the age, lifestage (e.g., pregnant and lactating women), gender (if appropriate), and population group (e.g., per capita, consumers only) for the exposure scenario of interest. Other exposure factors that might be needed for assessing dietary or non-dietary ingestion exposures include:
- Body weight (Chapter 8)
- Activity-specific factors (Chapter 16)
- Consumer product use information (Chapter 17)
- Life expectancy values, specifically when evaluating cancer risk (Chapter 18)
The Exposure Factors Tab of the Indirect Estimation Module provides links to data on other factors.