Food Consumption Rates for Estimating Exposures to Chemicals in Food
A food consumption rate can be described as the amount of a food item consumed over a given period of time by an individual. When combined with data on the level of agents or substances (e.g., chemicals, nutrients, food additives, or other chemicals) in food, doses (i.e., the intake amount) of these agents or substances can be derived. The doses in turn can be compared to standards or reference values for that agent or substance to assess nutritional adequacy or health risks. There are many sources and types of food consumption data. The consumption rates needed for a particular risk or nutritional assessment greatly depend on factors related to the particular assessment. This chapter describes factors relevant to selecting appropriate food consumption rates and ways to derive or
collect appropriate data, when necessary, with a focus on chemicals in food, excluding biological contaminants. 27.1 Calculating the Dose of Chemicals in FoodFor chemicals in food, the exposure dose (i.e., the amount of chemical intake) is estimated by multiplying the amount of chemical per unit of food by the amount of food consumed per unit time (i.e., food consumption rate). Exposure to chemical via food = mg chemicalg food g fooddayÊËÁ ˆ¯˜ ¥ ÊËÁ ˆ¯˜ Food consumption rates are generally in units of days, both for consumption measured over just one day, as well as for long-term exposures when the amount consumed over a period of time is averaged over the time period to obtain an average daily food consumption rate. Exposure assessments generally use food consumption rates that have been normalized to body weight (g food/kg body weight/day). Normalizing to body weight reduced the variability in food consumption rates attributable to differences in body weight. Normalizing to body weight also provides a metric which is in units consistent with toxicity criteria values (e.g., reference dose values), which are typically expressed as milligrams per kilogram-day. Rates that have been normalized by dividing each person’s food consumption rate by his or her body weight are preferable to dividing consumption rates by an average body weight. This is because important interindividual body weight variability information is included in individually normalized rates. Hereafter, we will refer to the amount of chemical consumed per unit body weight per unit time as dose. In addition, it is noted that some exposure assessors may normalize to other body measures (e.g., body mass index) when such a metric is considered more appropriate to that particular assessment. The equation then becomes: Dose = mg chemicalg food g chemical foodkg-body weight per ÊËÁ ˆ¯˜ ¥ dayÊËÁ ˆ¯˜
27.2 Considerations for Selecting or Deriving Food Consumption Rates There are many factors to consider in selecting appropriate food consumption rate estimates for a particular risk or nutritional assessment. These factors can be related to the exposure (e.g., duration, subpopulation exposed) or to the chemical of concern (e.g., toxicokinetics). This chapter highlights these considerations in regards to the various types of dietary assessments that may be needed.