Short-term respiratory effects of photochemical oxidant exposure in exercising children

The Acute Effects of Exercising in Air Pollution: A Systematic Review of Randomized Controlled Trials

BACKGROUND

The acute effects of air pollution (AP) exposure during physical activity have been studied. However, comprehensive systematic reviews are lacking, particularly regarding moderate-to-vigorous physical activity (MVPA).

OBJECTIVE

Our objective was to determine the acute health- and exercise-related effects of AP exposure during a bout of MVPA in healthy individuals.

METHODS

We searched for randomized controlled trials in MEDLINE, Embase, Cochrane CENTRAL, SPORTDiscus, Agricultural and Environmental Science Database, ClinicalTrials.gov, International Standard Randomised Controlled Trial Number Registry, and the World Health Organization (WHO) International Clinical Trials Registry Platform up to July 2020 without language or date restrictions. Studies including healthy subjects engaging in a bout of MVPA while exposed to one or more of the following air pollutants were eligible: particulate matter, black carbon, carbon monoxide, nitrogen dioxide, ozone, diesel exhaust, and traffic-related air pollution (TRAP). Main outcome measures were markers of pulmonary function, symptoms, cardiovascular function, cognitive function, systemic inflammation, and exercise response. The evidence was synthesized by vote counting based on direction of effect.

RESULTS

In total, 53 studies were included in the systematic review. Studies employed a heterogeneous mix of exercise protocols, AP interventions, and measured outcomes. Pooled results suggest ozone exposure during MVPA has an adverse effect on pulmonary function (100% [95% confidence interval (CI) 88-100], p < 0.001; high-certainty evidence) and reported symptoms (88% [95% CI 69-96], p < 0.001; low-certainty evidence). The effect of exposure to carbon monoxide, nitrogen dioxide, small engine exhaust, or diesel exhaust during MVPA on health- and exercise-related outcomes is uncertain because of insufficient evidence and the low to very low certainty of available evidence.

DISCUSSION

The evidence is strongest for ozone, exposure to which generally induced a reduction in pulmonary function and increased symptoms during MVPA. The research related to other outcome domains remains inconclusive. Although long-term exposure to AP is proven to be hazardous, the evidence for healthy individuals to forgo MVPA during periods of high (non-ozone) pollution remains weak.

TRIAL REGISTRATION

Retrospectively registered in PROSPERO (CRD42020188280) on 10 July 2020.

The health effects of exercising in air pollution

The health benefits of exercise are well known. Many of the most accessible forms of exercise, such as walking, cycling, and running often occur outdoors. This means that exercising outdoors may increase exposure to urban air pollution. Regular exercise plays a key role in improving some of the physiologic mechanisms and health outcomes that air pollution exposure may exacerbate. This problem presents an interesting challenge of balancing the beneficial effects of exercise along with the detrimental effects of air pollution upon health. This article summarizes the pulmonary, cardiovascular, cognitive, and systemic health effects of exposure to particulate matter, ozone, and carbon monoxide during exercise. It also summarizes how air pollution exposure affects maximal oxygen consumption and exercise performance. This article highlights ways in which exercisers could mitigate the adverse health effects of air pollution exposure during exercise and draws attention to the potential importance of land use planning in selecting exercise facilities.

Lung function growth in children with long-term exposure to air pollutants in Mexico City

RATIONALE

Although short-term exposure to air pollution has been associated with acute, reversible lung function decrements, the impact of long-term exposure has not been well established.

OBJECTIVES

To evaluate the association between long-term exposure to ozone (O(3)), particulate matter less than 10 mum in diameter (PM(10)), and nitrogen dioxide (NO(2)) and lung function growth in Mexico City schoolchildren.

METHODS

A dynamic cohort of 3,170 children aged 8 years at baseline was followed from April 23, 1996, through May 19, 1999. The children attended 39 randomly selected elementary schools located near 10 air quality monitoring stations and were visited every 6 months. Statistical analyses were performed using general linear mixed models.

MEASUREMENTS AND MAIN RESULTS

After adjusting for acute exposure and other potential confounding factors, deficits in FVC and FEV(1) growth over the 3-year follow-up period were significantly associated with exposure to O(3), PM(10), and NO(2). In multipollutant models, an interquartile range (IQR) increase in mean O(3) concentration (IQR, 11.3 ppb) was associated with an annual deficit in FEV(1) of 12 ml in girls and 4 ml in boys, an IQR range (IQR, 36.4 microg/m(3)) increase in PM(10) with an annual deficit in FEV(1) of 11 ml in girls and 15 ml in boys, and an IQR range (IQR, 12.0 ppb) increase in NO(2) with an annual deficit in FEV(1) of 30 ml in girls and 25 ml in boys.

CONCLUSIONS

We conclude that long-term exposure to O(3), PM(10), and NO(2) is associated with a deficit in FVC and FEV(1) growth among schoolchildren living in Mexico City.

Effects of ambient ozone exposures during the spring and summer of 1994 on pulmonary function of schoolchildren

To investigate the effect of natural exposure to ambient ozone over time, a follow-up study of school-aged children was performed in two small towns in southwestern Germany (Freudenstadt and Villingen) between March and October of 1994. Ozone half-hour mean concentrations were measured continuously and pulmonary function was tested in each child on four occasions (April, June, August, and September). To obtain an average short-term ozone effect, we first analyzed the data from the four time points separately and then constructed a model that included all information. During the study period the median (5th to 95th percentile) of all half-hour values of the ozone concentration was 101 micrograms/m3 or 50.6 ppb (45-179 micrograms/m3 or 22.5-89.8 ppb) in Freudenstadt and 64 micrograms/m3 or 32.1 ppb (1 to 140 micrograms/m3 or 0.5-70.1 ppb) in Villingen. To assess the effects of an individual ozone exposure we related the highest ozone concentration in the respective 24 hours before lung function testing to the results of the subconcentration in the respective 24 hours before lung function testing to the results of the subsequent pulmonary function tests. In the lung function test following the highest ozone exposure, the results of our cross-sectional linear regression analysis showed a significant negative correlation (P = 0.0181) between ozone exposure and forced vital capacity (FVC). In the longitudinal linear regression model we observed a negative statistical correlation between ozone exposure and lung function for the subpopulation living in the town with the high ozone levels (Freudenstadt). The association was more pronounced in boys than girls. For the children in Freudenstadt the decrement of FVC was -12.31 ml/10 micrograms/m3 ozone and the decrease in the forced expiratory volume in 1 second (FEV1) was -11.29 ml/10 micrograms/m3 ozone.