Children face special risks from air pollution because their lungs are growing and because they are so active and breathe in a great deal of air.
Just like the arms and legs, the largest portion of a child's lungs will grow long after he or she is born. Eighty percent of their tiny air sacs develop after birth. Those sacs, called the alveoli, are where the life-sustaining transfer of oxygen to the blood takes place. The lungs and their alveoli aren't fully grown until children become adults.1 In addition, the body's defenses that help adults fight off infections are still developing in young bodies.2 Children have more respiratory infections than adults, which also seems to increase their susceptibility to air pollution.3
Furthermore, children don't behave like adults, and their behavior also affects their vulnerability. They are outside for longer periods and are usually more active when outdoors. Consequently, they inhale more polluted outdoor air than adults typically do.4
Air Pollution Affects Children Before They Are Born
Several studies have found air pollution linked to harm to children while they are still in the womb. A large study in California found that higher particle-pollution levels increased the risk of preterm birth.5 Pregnant women exposed to even low levels of particle pollution had higher risk for preterm birth in a Boston study.6 Preterm births occurred more frequently when particle pollution spiked, as an Australian study found, even when the researchers controlled for other risk factors.7
Air Pollution Limits Lung Growth in Children
The Southern California Children's Health study looked at the long-term effects of air pollution on children and teenagers. Tracking 1,759 children who were between ages 10 and 18 from 1993 to 2001, researchers found that those who grew up in more polluted areas face increased risk of reduced lung growth, which may never recover to the full capacity. The average drop in lung function was similar to the impact of growing up in a home with parents who smoked.5
Community health studies are pointing to less obvious, but serious effects from year-round exposure to ozone, especially for children. Scientists followed 500 Yale University students and determined that living just four years in a region with high levels of ozone and related co-pollutants was associated with diminished lung function and frequent reports of respiratory symptoms.6 Another earlier Children’s Health Study of 3,300 school children in Southern California found reduced lung function in girls with asthma and boys who spent more time outdoors in areas with high levels of ozone. 7
Cleaning Up Pollution Can Reduce Risk to Children
There is also real-world evidence that reducing air pollution can help protect children. A 2015 follow-up to the Southern California Children's Health study showed that reducing pollution could improve children's health. Researchers compared the children who had been part of their earlier studies to a new group of 863 children living in the same area, but growing up between 2007 and 2011, when the air in Southern California was much cleaner. Children growing up in the cleaner air had much greater lung function, a benefit that may help them throughout their lives. As the researchers noted, their study suggested that "all children have the potential to benefit from improvements in air quality.” 8
Further evidence that cleaner air provides real benefits to children's health came in a 2016 report from the same study exploring changes to 4,602 children's respiratory symptoms such as coughing, congestion and phlegm. The study looked at the changes in these symptoms in three groups of children living in Southern California over different periods of time when air quality also differed (1993-2001, 1996-2004, and 2003-2012). As air quality improved, the children in the study suffered fewer bronchial symptoms whether they had asthma or not. In communities where the air quality improved the most, the children experienced even fewer symptoms. 9
So, does cleaning up the air really improve children's health? In 2017 researchers reviewed these long-term studies of children in Southern California and the impact of improvements in air quality on their health. They concluded that the 20 years of collected data provided strong evidence of the potential to improve children's health by reducing some of the most common outdoor air pollutants. 10
The U.S. is not alone in this finding. In Switzerland, particle pollution dropped during a period in the 1990s. Researchers there tracked 9,000 children over a nine-year period, following their respiratory symptoms. After taking other factors such as family characteristics and indoor air pollution into account, the researchers noted that during the years with less pollution, the children had fewer episodes of chronic cough, bronchitis, common cold, and conjunctivitis symptoms. 11
Dietert RR, Etzel RA, Chen D, et al. Workshop to Identify Critical Windows of Exposure for Children's Health: immune and respiratory systems workgroup summary. Environ Health Perspect. 2000; 108 (supp 3); 483-490.
World Health Organization: The Effects of Air Pollution on Children's Health and Development: a review of the evidence E86575. 2005. Available at http://www.euro.who.int/document/E86575.pdf .
American Academy of Pediatrics Committee on Environmental Health, Ambient Air Pollution: health hazards to children. Pediatrics. 2004; 114: 1699-1707. Statement was reaffirmed in 2010.
Laurent O, Hu J, Li L, et al. A statewide nested case-control study of preterm birth and air pollution by source and composition: California, 2001-2008. Environ Health Perspect. 2016. 124:1479-1486. doi: 10.1289/ehp.1510133.
Nach RM, Mao G, Zhang X, et al. Intrauterine inflammation and maternal exposure to ambient PM2.5 during preconception and specific periods of pregnancy: the Boston Birth Cohort. Environ Health Perspect. 2016; 124:1608-1615; http://dx.doi.org/10.1289/EHP243.
Li S, Guo Y, Williams G. Acute impact of hourly ambient air pollution on preterm birth. Environ Health Perspect. 2016; 124:1623–1629; http://dx.doi.org/10.1289/EHP200.
Gauderman WJ, Avol E, Gilliland F, Vora H, Thomas D, Berhane K, McConnell R, Kuenzli N, Lurmann F, Rappaport E, Margolis H, Bates D, Peters J. The effect of air pollution on lung development from 10 to 18 years of age. N Engl J Med. 2004; 351: 1057-1067; Gauderman WJ, Urman R, Avol E, Berhane K, McConnell R, Rapport E, Chang R, Lurmann F and Gilliland F. Association of Improved Air Quality with Lung Development in Children. N Eng J Med. 2015; 372: 905-913.
Berhane K,Chang C-C, McConnell R, Gauderman JW, et al. Association of Changes in Air Quality with Bronchiatic Symptoms in Children in California, 1993-2012. JAMA. 2016; 315: 1491-1501.
Gilliland F, Avol E, McConnell R, Berhane K, Gauderman WJ, Lurmann FW, et al. 2017. The Effects of Policy-Driven Air Quality Improvements on Children’s Respiratory Health. Research Report 190. Boston, MA:Health Effects Institute.
Bayer-Oglesby L, Grize L, Gassner M, Takken-Sahli K, Sennhauser FH, Neu U, Schindler C, Braun-Fahrländer C. Decline of Ambient Air Pollution Levels and Improved Respiratory Health in Swiss Children. Environ Health Perspect. 2005; 113:1632-1637.
Page last updated: February 12, 2020