Health-related exposure assessment

diagram presenting oral, dermal and inhalativ exposure to manClick to enlarge
Exposure - pathes of environmental impact
Source: Umweltbundesamt

People are exposed to a wide range of environmental influences, such as noise or pollutants in air and water. These stressors may cause acute or chronic health effects.

Human exposure

Exposure is defined as contact of an organism with chemical, biological or physical influences. This contact can occur via mouth (e. g. by food), the respiratory system or skin. These routes of entry from the environment into the organism are called exposure pathways

It is nearly impossible to measure the entire human exposure completely and precisely. Consequently, estimation by means of mathematical models is necessary. Usually only the combination of measurements and estimations may reflect reality appropriately.

A lot of information is needed for estimating human exposure. To estimate human exposure to lead, for example, lead concentrations in different environmental media (soil, water, air) and foods have to be known. The degree of exposure is also determined by the individual’s behaviour (e. g. the drinking water consumption). Such pieces of information are called "exposure factors".

Particularly unfavourable exposure factors are used for "conservative" (in terms of avoidance of health risks) exposure estimations. In this case a value leading to a very high exposure level is assumed for each factor: For example, the exposure is estimated by combining a comparatively high drinking water consumption with a high concentration of lead in drinking water and in foods as well as increased lead concentration in the ambient air.

The advantage of this method is its simple and fast application. Its main limitation is the lack of information on the variation of the exposure within the population. The exposure is estimated by a single value only reflecting a very unfavourable – often unrealistic – exposure situation.

Hence, the application of distribution-based (probabilistic) exposure estimation has gained momentum in the scientific community. In addition to the average exposure the probabilistic approach provides knowledge on the variation of the exposure within the population of interest.

The “Xprob” project

Researchers from the Universities of Bielefeld and Bremen, the University Clinic Hamburg-Eppendorf, the Institute of Public Health of North-Rhine Westphalia (lögd), the Governmental Institute of Public Health of Lower Saxony and the German Federal Environment Agency (UBA) cooperated in the field of distribution-based exposure assessment from 2002 to 2006 in the project "Evaluation of Standards and Models for Probabilistic Exposure Estimation - Xprob".

The Xprob consortium developed guidelines for the application of distribution-based exposure estimation. Moreover, current and representative German data on exposure factors was gathered and evaluated in a uniform way.