This picture shows the many different pathways by which a child can be exposed to
environmental chemicals, in this case lead. Building exposure models based upon ambient
monitoring requires making many assumptions about routes of exposure including
quantitative importance of each route of exposure and rates of absorption into the body from
each route. This is difficult for adults, but even more complex for children who are constantly
growing and changing, have changing behavior patterns and live in changing living zones
based upon size and activity. Exposure modeling for children requires utilization of a multilifestage
approach and has multiple sources of potential error and uncertainty. Regulatory
agencies and researchers are continuously revising and improving upon complex and
extensive exposure models but there is always both uncertainty and error attached to
exposure estimates generated with models.