Which material is NOT listed as a potential source of lead exposure?

Child-friendly crayons are generally formulated to be safe for use by children and are designed to meet specific safety standards that limit harmful substances, including lead. Manufacturers of children’s products, especially those for art and play, are often required to ensure that their items do not contain lead paint or significant levels of lead in any components. Consequently, reputable makers of crayons target safety as a priority, making them a less likely source of lead exposure compared to the other materials listed.

In contrast, pool cue chalk and some bone meal supplements have been known to contain lead as a contaminant or additive. Some hair dyes also have been implicated in lead exposure due to certain formulations that may include lead or other heavy metals. Therefore, among the options provided, child-friendly crayons stand out as the material least likely to be a source of lead exposure.