Our results suggest that ambient levels of PM2.5 and ozone can reduce the high-frequency component of heart rate variability in elderly subjects living in Mexico City and that subjects with underlying hypertension are particularly susceptible to this effect.
In a panel study of Mexican children (5-13 y of age) with mild asthma, the authors studied the relationship between ozone exposure and the course of childhood asthma. Decrements in peak expiratory flow rate were associated with ozone, and respiratory symptoms were associated with both ozone level and ambient particulate matter (< 10 microm) level. After the authors adjusted for minimum temperature and autocorrelation in the data, they determined that an increase of 50 ppb in a daily ozone 1-h maximum was related to an 8% increase in cough (95% confidence interval = 2, 15); a 24% increase in phlegm (95% confidence interval = 13, 35); and an 11% increase in low respiratory symptoms index (95% confidence interval = 5, 19). The authors concluded that children with mild asthma who resided in the south of Mexico City were affected adversely by the high ozone ambient levels observed in this area.
To determine the acute effects of ozone exposure, the authors conducted a short follow-up study of respiratory illness in a population of 111 preschool children frequently exposed to ozone levels that regularly exceed 0.120 parts per million (ppm). The children attended a private kindergarten in the southwestern part of Mexico City. Parents completed a questionnaire on demographic data, medical history, and potential sources of indoor air pollution. To determine the relation of ozone and respiratory-related school absenteeism, the authors used a logistic regression model for longitudinal data. During the 3-month follow-up, 50% of the children had at least one respiratory-related absenteeism period, and 11.7% had two or more. Children exposed for 2 consecutive days to high ozone levels (> or = 0.13 ppm) had a 20% increment in the risk of respiratory illness. For children exposed for 2 consecutive days to a high ozone level and the previous day to low temperature (< or = 5.1 degrees C), the risk reached 40% (odds ratio = 1.44, 95% confidence interval 1.37-1.52). This study suggests that ozone exposure might be positively associated with the risk of respiratory illness in children and that it may have an interactive effect with low temperature exposure.
scite is a Brooklyn-based organization that helps researchers better discover and understand research articles through Smart Citations–citations that display the context of the citation and describe whether the article provides supporting or contrasting evidence. scite is used by students and researchers from around the world and is funded in part by the National Science Foundation and the National Institute on Drug Abuse of the National Institutes of Health.