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4 | DISCUSSION
exposure windows and respiratory symptoms was almost universally positive but did not reach statistical significance ( Table 2 ).
In this school-based cohort of children screened for asthma morbidity and respiratory symptoms , we found short- and long-term radon exposure at schools were associated with an increased odds of having an asthma diagnosis and school absenteeism . We consistently found nonsignificant positive associations with radon exposure and report of noisy breathing , nighttime cough and nighttime difficulty breathing . These findings fit our hypothesized model that radon exposure is associated with asthma diagnosis and morbidity . Children were screened in the spring of the academic year in anticipation of recruitment into the research study for the following academic year . 6 We characterized our short-term exposures to capture the current academic year — 1 , 5 , and 7 months — as this was reflective of time the subjects had experienced school-based exposures for the majority of their days for over half a year at the time of completing the survey . The longer-term assessments — 12 and 24 months — may be less precise , as the possibility of not having the school as the primary source of exposure increases with longer periods of measurements , such as during vacations and weekends . Additionally , the children may not have attended the same school in the prior years ; however , we believe this is unlikely to materially affect our results since the average participant was 8-year-old ( approximately second grade ) and likely attended kindergarten and first grade in the same school as their exposure assessment .
Our previous work has identified significant contributions of school exposures to respiratory symptoms , 9 – 11 and it appears radon may have a similar effect . When evaluating our secondary outcomes , we found increased odds of reported respiratory symptoms with radon exposure ; however , this association was not statistically significant . It bears highlighting that the estimated radon levels in our study cohort were all lower than the actionable level of 4 pCi / L recommended by the U . S . Environmental Protection Agency ( EPA ) for radon mitigation . 12 Despite these low levels , we were able to find an association between radon exposure and asthma , suggesting that health effects of radon may be able to be felt at levels that would not trigger an intervention in public or private buildings . It is worth noting that the EPA has not determined a safe radon level of exposure , 12 and mitigation can decrease levels to less than 0.5 pCi / L . 13
While provocative , these findings are limited by the nature of the cross-sectional study design which assesses the outcome at one point in time , limiting confidence in causal inferences relating the exposure to outcome . Assessment of radon was modeled from local measured and geospatial constructs , and the outcome was determined by parental report , both of which may lead to imprecision in the actual exposure and outcome . However , the radon model used a two-step method which increases the accuracy of the estimated levels . 8 The prevalence of asthma in this study is also notably high , however not far from the range that may be seen in urban school districts in the United States . Nevertheless , some level of reporting bias may be present in the asthma outcome , though unlikely to have influenced the associative findings of radon on that outcome . Lastly , due to the brief nature of the screening survey , adjusting for potential confounders including participants ’ demographic ,
Pediatr Pulmonol . Author manuscript ; available in PMC 2022 December 01 .