Overall, an estimated 80.7% (95% CI: 79.0–82.3) of U.S. adolescents aged 12–17 years reported thinking that air pollution could impact health (Table 1). This percentage ranged from 72.9% (95% CI: 69.2–76.6) in 2015 to 85.7% (95% CI: 82.9–88.5) in 2017 (Table A1) increased monotonically across categories of parental education level and was higher among respondents in metropolitan than nonmetropolitan areas (Table 2). More than half of U.S. adolescents aged 12–17 year reported thinking there were things they could do to limit their own or their family’s exposure to air pollution (51.5%; 95% CI: 49.6–53.5). This percentage was lowest in 2015 (44.4%; 95% CI: 40.4–48.5) and highest in 2018 (57.4%; 95% CI: 53.5–61.4) (Table A1), with a p_trend = .018 (Table A3), and increased with increasing parental educational level (Table 2).

For all survey years combined, an estimated 19.0% (95% CI: 17.5–20.4) of adolescents had ever heard or read about the AQI or air quality alerts where they live (Table 1). Percentages varied modestly by year (Table A1) and were higher among adolescents whose parent had a bachelor’s degree or higher (22.5%; 95% CI: 20.1–24.9) than among those whose parent completed high school or less (15.3%; 95% CI: 12.4–18.1; Table 2). Percentages of adolescents who thought or were informed that air quality was bad in the past 12 months are shown in Table 1 (for all years combined) and Table A1 (separately by year). Among those who thought or were informed air quality was bad in the past 12 months, 46.1% (95% CI: 40.0–52.1) did something differently (Table 1). Among those who did something differently, spending less time outdoors (82.1%; 95% CI: 76.0–88.1) and closing windows of the house (49.3%; 95% CI: 41.5–57.1) were reported most frequently. Overall, 18.5% (95% CI = 17.0–20.1) always or usually avoided busy roads when walking, biking, or exercising outdoors. Table A2 shows the percentages of adolescents that think air pollution can impact health, think they can limit their or their family’s exposure to air pollution, and are aware of air quality alerts where they live, by both demographic categories and across years. Broadly speaking, analyses both within demographic categories and by survey year were limited by small sample sizes for some strata; resulting estimates are imprecise.

Based on the results, awareness among adolescents that air pollution can impact health was relatively high during the 2015–2018 study period and was higher in 2018 than in 2015. Similarly, the percentage of U.S. adolescents who thought there were things they could do to limit their or their family’s exposure to air pollution increased from 2015 to 2018. In contrast, only 19% of U.S. adolescents were aware of the AQI or air quality alerts during the 2015–2018 study period, with little variation over time. Each of these metrics of air quality awareness and perceptions was highest among adolescents with parental educational levels of bachelor’s degrees or higher.

Few other data are available with which to compare our findings. One study of adolescents surveyed 13- to 17-year-olds in Mexico City and found that 75% of respondents thought air pollution affected health a lot and only 1% believed that it did not affect health at all [23]. Other qualitative studies found that adolescents identified air pollution as a main environmental concern [24,25]. Awareness of air quality alerts among U.S. adults has ranged from one-third in a 2005–2006 study of adults from Portland, Oregon, and Houston, Texas, to nearly half in a 2014–2016 study of adults from across the U.S. [18,19]. Among adults with children 4 years of age and older surveyed in Utah in 2003, 88% were aware of air quality alerts with higher awareness reported among parents of children with asthma than among parents of children without asthma [26]. These findings indicate considerably less awareness of air quality alerts among U.S. adolescents than among adults, suggesting an opportunity for educating adolescents about their use.

The percentage of adolescents who were aware of air quality alerts was lower than both the percentage who thought that air pollution could impact health and the percentage who thought that there were ways to limit exposure. Because knowing when to take action to reduce exposure may depend on accurate knowledge of the ambient air quality, increasing awareness of air quality alerts could be important for exposure reduction. Air quality alerts based on the AQI contain information about potential health effects of air pollution and ways to limit exposure [27], so learning about the AQI could provide a way to increase knowledge of these topics, too. One way adolescents might learn about the AQI is in school, including through educational materials [28,29] developed by the EPA. However, these study results raise questions about whether this information, in fact, reaches adolescents.

By age group, 12- to 13-year-olds showed the greatest and most consistent increases over time in both the percentage who thought that air pollution could impact health and the percentage who thought that they could limit exposure to air pollution. If there were increased coverage of the topic in schools or by the media or increased awareness among the public in general, this could, speculatively, have contributed to changes in knowledge over time. However, perceiving that there are ways to limit exposure to air pollution does not necessarily indicate accurate knowledge of the effective ways to reduce exposure. For 2015–2018 combined, approximately 29% fewer 12- to 17-year-olds thought there were things they could do to limit exposure than thought that air pollution could impact health. This difference could represent a lack of knowledge of ways to reduce exposures or an actual or perceived inability to implement those methods.

Overall, the percentage of adolescents who reported that they talked to a health care professional about ways to limit air pollution exposure was low (3%) with minimal variation seen over the survey years (data not shown). This finding is consistent with a previous finding that only 3% of U.S. adults surveyed in 2014–2016 reported discussing ways to limit exposure with a health care professional [18]. Together, these findings suggest that health care professionals could be another channel to inform adolescents, as well as adults, about the health effects of air pollution and ways to limit exposure.

For years 2016–2018 combined, a little less than half of U.S. adolescents did something differently when they thought or were informed air quality was bad in the preceding 12 months. In another study, 10%–15% of respondents reported changing an activity during an air quality advisory; however, change was related to their perception of air quality, not the actual advisory [19]. In a study of young adult students in Singapore, attention to media, interpersonal discussion, knowledge, and risk perception were factors found to be associated with intention to take self-protective measures related to haze [30]. Behaviors may also be influenced by parents who might restrict certain activities during an episode of poor ambient air quality or take actions to reduce pollution [26]. Together, these findings suggest that addressing behavior change related to ambient air pollution exposure may involve more than just increasing awareness of ambient air quality, and there might exist other important barriers to exposure reduction.

Among U.S. adolescents who did something differently when they thought or were informed air quality was bad, the most frequently reported activities were spending less time outdoors and closing windows of the house. Although limiting outdoor activity is sometimes a recommendation to reduce exposure to air pollution [17], this assumes better indoor than outdoor air quality. Indoor air pollution is also associated with health effects such as respiratory effects among children with asthma [31]. In addition to sources that originated inside, indoor air pollution can contain outdoor pollution that penetrated the building envelope [32,33]. U.S. adolescents also reported exercising indoors instead of outdoors or on a different day or time and doing less strenuous activity when they thought or were informed air quality was bad. Ambient air quality has been found to influence outdoor activity [22] and overall levels of physical activity [21] in other studies of adults. Behaviors may be different for adolescents, though, and findings from studies of adults might not be applicable.

Our study described percentages of air quality awareness and perceptions by parental education level. Understanding air quality awareness and perceptions of adolescents by parental education level, an indicator of SES [34], is important because children of parents with lower levels of educational attainment may be at increased risk of asthma [35] and children with asthma are at risk of acute exacerbations from air pollution [11]. In addition, some studies, including a study of respiratory health among elementary school children in Canada, suggest that effect modification might exist between ambient air pollution exposure and health effects, by SES, with greater effects for those of lower SES [36,37]. Finally, differences in exposure to ambient air pollution based on SES have been found in parts of the U.S. [38]. These findings suggest that individuals of lower SES may be at increased risk of the health effects from ambient air pollution because of both greater exposure and susceptibility to air pollution. Increasing awareness related to ambient air pollution may not be sufficient if individuals do not have resources to avoid air pollution exposure, though, and this is a factor to consider when developing interventions.

One notable limitation of this study is the lack of data available on health status. In particular, respiratory health status, such as asthma, was not available for YouthStyles respondents. Another limitation is that we analyzed responses by only four regions. Differences in perceptions that might exist within regions are not captured by our analyses. In addition, although the aim of the survey was to focus on outdoor air pollution, the survey questions did not explicitly exclude indoor air pollution, and we could not assess the extent to which respondents may have been referring to indoor air quality in their responses. Furthermore, YouthStyles respondents were recruited via an adult survey respondent in the home, and while response rates for adults ranged from 67% in 2015 to 74% in 2017, YouthStyles survey response rates were lower than 50% each year. We cannot determine if the adult or adolescent nonresponders differed from adult or adolescent responders, respectively, in terms of unmeasured variables. For example, homeownership versus renter status was not reported in the YouthStyles survey and was not accounted for in our analyses; however, the weighting of the data take into account age and household income, and we do not anticipate that our results insufficiently represent any category of occupancy status. Also, participants were provided with Internet access and a web-based device, as needed. Although this could create an incentive to participate in the survey among people without Internet access or devices, and theoretically make the sample less representative of the U.S. population, the results are weighted by household income, and for 2015 and 2016, by Internet access, to make them representative by these variables.

A strength of this study is that we analyzed data from a survey that was weighted to make it representative of adolescents in the U.S. based on several demographic variables. This makes the results useful for considering awareness, perceptions, and behaviors of adolescents across the U.S. Other strengths of our analysis include the large sample of adolescents on which our results are based and the inclusion of identical survey questions over several years, which allowed us to pool survey responses for a robust description of U.S. adolescents’ awareness, perceptions, and behaviors related to ambient air quality.

In summary, U.S. adolescents were found in this study to have a relatively high awareness that air pollution could impact health, with increased percentages over time in both this awareness and the perception that there were things they could do to limit exposure. However, gaps were found between the awareness of the potential impacts and the perception that they could limit exposure, the engagement in behaviors to reduce exposure, and the awareness of air quality alerts. Furthermore, differences by some demographic variables were seen. These results can be used to inform interventions to increase awareness related to ambient air quality and engagement in behaviors aimed at reducing air pollution exposures among U.S. adolescents.