Lead: Young children are most commonly exposed to lead in consumer products from the direct mouthing of objects, or from handling such objects and subsequent hand-to-mouth activity. Adverse health effects of lead poisoning in children are well-documented and may have long-lasting or permanent consequences. Effects include neurological damage, delayed mental and physical development, attention and learning deficiencies, and hearing problems. Because lead accumulates in the body, even exposures to small amounts can contribute to the overall level of lead in the blood and to the subsequent risk of adverse health effects. Therefore, any un-necessary exposure of children to lead should be avoided.
Source: CPSC http://www.cpsc.gov/businfo/leadguid.html

Plastics: “Some petroleum-based plastics may leach harmful chemicals into foods and drinks, especially when plastic comes in contact with oily or fatty foods, during heating, as a result of harsh cleaners, and when exposed to excessive moisture.”

-Select safe plastics that use polyethylene (#1, #2, and #4) and polypropylene (#5), which require the use of less toxic additives. They also are non-chlorinated.

- Avoid choosing products that use polycarbonate (#3) and polystyrene (#6), which often are found in baby bottles or sippy cups.”

Source: HealthyChild.org http://healthychild.org/5steps/5_steps_5/#what_to_do