Dietary exposures calculation¶

In probabilistic exposure assessment we consider a population of individuals. Exposure assessment with MCRA can address acute exposure or chronic exposure. Acute exposure is relevant when the short-term effect on individuals is relevant, chronic exposure when the long-term effects on the individuals matter. In MCRA short-term is operationalised as one day, so effectively acute exposure assessment is concerned with a population of person-days, whereas chronic exposure assessment is concerned with a population of persons.

The basic operation in exposure assessment is integrating consumptions and concentrations per food. With multiple foods, consumptions are typically correlated, therefore MCRA works with the multivariate distribution of a consumption vector, as represented by the consumption data of individuals in a consumption survey. In contrast, the distributions of concentration for each food are typically considered to be independent between foods. E.g., eating an apple with an accidentally high residue concentration does not predict that another food eaten on the same day will also have a high residue concentration. As a consequence of this assumption, concentrations of substances are modelled for each food independently.

For large assessment groups, the use of dietary exposures screening may be used to reduce the complexity of dietary exposures calculations and only focus calculations on the risk drivers. In this case, only detailed information is recorded for the risk drivers. With or without screening MCRA produces the same estimated cumulative exposure distribution summarized by percentiles and exceedance percentages, the same contributions of all substances and all modelled foods. After screening, contributions related to food-as-eaten are available for the risk drivers only.

In cumulative exposure calculations two simple approaches are used to identify and select mixtures contributing to the exposure of a target population:

qualitative approach: counting of co-exposure. To which combinations of substances are individuals exposed?

Co-exposure of substances is a qualitative approach where the number of combinations of substances to which an individual is exposed is recorded. There is no cut-off level, the only criterion is the presence of a substance in the simulated daily diet or not. For an acute or short term exposure assessment, a simulated individual day is the smallest entity to determine co-exposure. For a chronic or long term exposure assessment, co-exposures are summarized at the individual level, e.g. co-exposure is determined combining all consumption days of an individual. For more information see co-exposure of substances.
quantitative approach: maximum cumulative ratio (MCR). To what degree are mixtures more important than single substances?

A quantitative approach is available in the exposures mixtures module.

Model details