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Fine Particulate Matter and Emergency Room Visits for Respiratory Illness. Effect Modification by Oxidative Potential
Scott A Weichenthal1,2, Eric Lavigne1, Greg J Evans3
11 Health Canada, Ottawa, Ontario, Canada.
Rationale:
Fine particulate air pollution (PM2.5; particulate matter 2.5 μm or less in diameter) is thought to contribute to acute respiratory morbidity in part through oxidative stress.
Objectives:
To examine the association between PM2.5 oxidative burden and emergency room visits for respiratory illnesses.
Methods:
We conducted a case-crossover study in Ontario, Canada between 2004 and 2011, including 127,836 cases of asthma, 298,751 cases of chronic obstructive pulmonary disease, and more than 1.1 million cases of all respiratory illnesses. Daily air pollution data were collected from ground monitors, and city-level PM2.5 oxidative potential was measured on the basis of a synthetic respiratory tract lining fluid containing the antioxidants glutathione and ascorbate. Conditional logistic regression was used to estimate associations between air pollution concentrations and emergency room visits, adjusting for time-varying covariates.
Measurements And Main Results:
Three-day mean PM2.5 concentrations were consistently associated with emergency room visits for all respiratory illnesses. Among children (<9 yr), each interquartile change (5.92 μg/m(3)) in 3-day mean PM2.5 was associated with a 7.2% (95% confidence interval, 4.2-10) increased risk of emergency room visits for asthma. Glutathione-related oxidative potential modified the impact of PM2.5 on emergency room visits for respiratory illnesses (P = 0.001) but only at low concentrations (≤10 μg/m(3)). Between-city differences in ascorbate-related oxidative potential did not modify the impact of PM2.5 on respiratory outcomes.
Conclusions:
Between-city differences in glutathione-related oxidative potential may modify the impact of PM2.5 on acute respiratory illnesses at low PM2.5 concentrations. This may explain in part how small changes in ambient PM2.5 mass concentrations can contribute to acute respiratory morbidity in low-pollution environments.
Insights
Fine particulate matter (PM2.5) air pollution increases respiratory emergency room visits, especially in children. Glutathione
Area of Science:
- Environmental Health
- Respiratory Medicine
- Toxicology
Background:
- Fine particulate air pollution, specifically PM2.5 (particulate matter 2.5 μm or less in diameter), is a suspected contributor to acute respiratory illnesses, potentially via oxidative stress.
- Understanding the link between PM2.5 oxidative burden and respiratory emergency room visits is crucial for public health.
Purpose of the Study:
- To investigate the association between the oxidative potential of PM2.5 and emergency room visits for respiratory conditions.
- To explore whether oxidative potential modifies the impact of PM2.5 on respiratory morbidity.
Main Methods:
- A case-crossover study was conducted in Ontario, Canada (2004-2011) analyzing over 1.1 million respiratory emergency room visits.
- Daily air pollution data and city-level PM2.5 oxidative potential (using glutathione and ascorbate in synthetic fluid) were collected.
- Conditional logistic regression models estimated the associations between PM2.5 and respiratory emergency visits, controlling for covariates.
Main Results:
- A consistent association was found between 3-day mean PM2.5 concentrations and respiratory emergency room visits.
- In children under 9, an interquartile increase in PM2.5 (5.92 μg/m³) correlated with a 7.2% higher risk of asthma-related emergency visits.
- Glutathione-related oxidative potential modified PM2.5's impact on respiratory visits, particularly at low PM2.5 concentrations (≤10 μg/m³).
Conclusions:
- Differences in glutathione-related oxidative potential may influence the effect of PM2.5 on acute respiratory illnesses, especially in low-pollution settings.
- This suggests that even low levels of PM2.5 can contribute to respiratory morbidity, with oxidative potential playing a key role.
- Ascorbate-related oxidative potential did not show a similar modifying effect on PM2.5's impact on respiratory outcomes.
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