Those might include bpa (which is found in many plastics), pesticide residue, and both legal and not-so-legal drugs.
Two weeks ago, Chicago became the first U.S. city to ban the use of bpa in baby bottles and sippy cups.
bpa, used in the lining of food cans, has been banned from some products in Canada.
Some manufacturers have removed bpa from consumer products such as baby bottles and water bottles.
bpa remains a common additive in both dental fillings and dental sealants, according to the American Dental Association.