Assessment of Circadian Rhythmicity of Respiratory Determinants Related to Diurnal Activities of Children and Adolescents: A Case Study in the City of Isfahan

Background: Diurnal sequences of activities conducted at several locations visited by individuals have an impact on population exposure to air pollution. However, data on individual's movement with a fine time resolution is rare. Methods: In the current study, 399 children and adolescents (aged 11–18 years) from Isfahan city were asked to recall their 24-hour diary during winter and spring 2014-2015. Daily ventilation rates for individuals were calculated using Consolidated Human Activity Database (CHAD) and were subject to cosinor analysis. Results: There was a significant circadian rhythm in inhalation rate, outdoor time-spent and ambient NO2 pollution. The ANOVA of rhythm parameters showed a significant difference (P < 0.05) between gender groups and day types, whereas the difference between age groups and seasons was not significant. Analysis of results showed that increased NO2 pollution was concurrent with increased inhalation rate and outdoor time-spent. Inhalation rates obtained for population groups were 9.3, 11.6, 9.0 and 11.3 L/min for high school girls, high school boys, elementary girls and elementary boys, respectively. Elementary boys were at higher risk of exposure to air pollution. Boys spent more time outdoors and in traffic than girls. Respondents spent 89% of their time inside and 82% of their inside time at home. They also spent 10% of their time during a year in school. Respondents were exposed to cooking generated pollutants 11 times a week. Among them, 30% were exposed to second-hand smoke, and 86.3% reported in very good health. Conclusion: We concluded that actual exposure levels may be underestimated when the simple risk assessment method is implemented without the survey of fine time resolution spatiotemporal activity data.