Ruth A. Etzel, MD, PhD, FAAP is an internationally recognized pediatrician, environmental epidemiologist, and preventive medicine specialist. She performed the first study to document that children with secondhand exposure to tobacco smoke had measurable exposure to nicotine. Her pioneering work led to nationwide efforts to reduce indoor exposure to tobacco, including the ban on smoking in US airliners. She also produced the first research to show that exposure to toxigenic molds in the home could be dangerous to infants' health. She served on the AAP Committee on Environmental Health from 1986 to 1995 and chaired it from 1995 to 1999. From 2009-2012 she led the World Health Organization's activities to protect children from environmental hazards. She is the co-editor of the Textbook of Children's Environmental Health. Sophie J. Balk, MD, FAAP is a general pediatrician at the Children's Hospital at Montefiore and Professor of Pediatrics at the Albert Einstein College of Medicine in Bronx, NY. Her academic work focuses on educating clinicians about pediatric environmental health. She is a past member and chairperson of the AAP Council on Environmental Health, and a past member of the AAP Section on Tobacco Control Executive Committee. She has served as Associate Editor of the 4 editions of Pediatric Environmental Health. Dr. Balk has published and lectured on skin cancer prevention, tobacco issues, and other environmental health issues relevant to pediatric practice.