Authors: Brankston Gabrielle, Greer Amy L, Marshall Quinn, Lang Brittany, Moore Kai, Hodgins Douglas, Hennessey John T G, Beeler-Marfisi Janet
Journal: Frontiers in veterinary science
Summary
# Editorial Summary Equine respiratory disease is multifactorial, but the role of ambient air quality in triggering lower airway inflammation has received little attention in veterinary literature. Researchers in Ontario retrieved bronchoalveolar lavage fluid (BALF) cytology samples from 154 horses (2007–2017) and identified elevated inflammatory markers—neutrophils, eosinophils, or mast cells—in 78 cases, then compared these findings against regional air quality measurements (fine particulate matter, nitrogen dioxide, ozone) and temperature data from the 4 weeks preceding presentation. A 2–3 week lag analysis revealed that each single-unit increase in PM₂.₅ and NO₂ levels raised the risk of detecting elevated lower airway granulocytes by 11% and 24% respectively, suggesting a genuine temporal relationship between pollutant exposure and airway inflammation. For practitioners managing horses with inflammatory airway disease or recurrent respiratory signs, these findings indicate that air quality advisories warrant consideration as environmental risk factors—particularly in regions with moderate industrial or vehicular pollution—and may justify modifications to work schedules or stable management during high-pollution episodes. Further investigation into region-specific thresholds and individual horse susceptibility would refine clinical recommendations for at-risk populations.
Read the full abstract on PubMed
Practical Takeaways
- •Monitor horses with respiratory sensitivity during high air pollution days; respiratory signs may appear 2-3 weeks after pollution exposure peaks
- •Use local Air Quality Health Index (AQHI) data to anticipate increased airway inflammation risk and adjust training/outdoor exposure accordingly for susceptible horses
- •Consider environmental air quality as a modifiable risk factor in managing horses with inflammatory airway disease alongside traditional management strategies
Key Findings
- •Single unit increases in 2-3 week lagged PM2.5 were associated with 11% greater risk of increased lower airway granulocytes (p=0.04)
- •Single unit increases in 2-3 week lagged NO2 were associated with 24% greater risk of increased lower airway granulocytes (p=0.03)
- •Ambient air pollution exposure shows a 0-3 week time lag before increased lower airway inflammatory cells appear on BALF cytology
- •78 of 154 horses examined showed increased proportions of neutrophils, eosinophils, and/or mast cells in bronchoalveolar lavage fluid