Environmental health is a segment of public health, and according to the World Health Organization (WHO) environmental health, "addresses all the physical, chemical and biological factors external to a person and all the related factors impacting behaviors. It encompasses the assessment and control of those environmental factors that can potentially affect health. It is targeted towards preventing disease and creating health-supportive environments. This definition excludes behavior not related to environment as well as behavior related to the social and cultural environment and genetics." A child's developing organ system is highly susceptible to environmental stressors and is at a higher risk of exposure to toxic environmental substances. Children breathe more air and drink more water than adults, are physically closer to -- and spend more time on -- the ground and engage in more hand-to-mouth contact than adults. It is imperative that school nurses recognize and address the factors that impact health in the school environment and work to mitigate the potential adverse health effects. School nurses are advised to augment their knowledge of environmental health issues as they relate to the school setting and to develop a consciousness about a healthy school environment. Unhealthy school environments can affect children's health, attendance, concentration, and performance as well as lead to expensive, time-consuming cleanup and remediation activities. Schools in better physical condition report improved academic performance while schools with fewer janitorial personnel and higher maintenance backlogs report poorer academic performance. It is the position of the National Association of School Nurses (NASN) that the registered professional school nurse (hereinafter referred to as school nurse) is an important member of the team that mitigates the effects of environmental health hazards in the school setting. The school nurse utilizes the nursing process and key principles from the NASN's "Framework for 21st Century School Nursing™" including assessment, prevention, advocacy, collaboration, and education (NASN, 2016, 2017). [This position statement was adopted in January 2014 and revised in June 2018. For the 2014 statement, see ED558472.]