What factor increases the vulnerability of young children to lead exposure?

Young children are particularly vulnerable to lead exposure for several reasons, among which the higher rates of hand-to-mouth activities play a significant role. Children often explore their environment by putting objects in their mouths, which can include toys, household items, or contaminated soil. If these items contain lead, children are at a much greater risk of ingesting harmful substances.

In addition to their exploratory behavior, children's smaller body weight means that they can be more heavily affected by smaller amounts of lead compared to adults. However, the act of regular hand-to-mouth activity substantially increases the likelihood of lead ingestion, which is a critical factor in understanding the risks associated with lead exposure in environments where lead contamination is present.

The other options do not increase vulnerability in the same way: access to educational materials might promote awareness and safety, while greater outdoor air exposure is generally more related to environmental factors than personal behavior regarding lead ingestion. Thus, focusing on hand-to-mouth activities highlights a direct behavioral aspect that contributes to the heightened vulnerability of young children to lead exposure.