Effects of Air Quality & Wildfire Smoke Inhalation on Horses
Updated December 15, 2023 | By: Carolyn Hammer, DVM, PhD
The Growing Threat of Wildfires
In the two-year period 2021-2022, the National Interagency Fire Center reported over 127,000 wildfires that consumed more than 14.7 million acres in the US. Across the border, there have been record-breaking wildfires burning in Canada with over 27 million acres burned so far this year.
These wildfires not only affect the health of horses in the immediate area, but wildfire smoke can drift and affect air quality hundreds of miles away. The widespread nature of these fires and resulting smoke pollution has greatly increased horse owner awareness of air quality and concerns for their horse’s health.
Importance of Air Quality for Horses
The Air Quality Index (AQI) is used to measure the quality of air and is reported on a scale of 0 - 500. The AQI indicates how clean or polluted the air is, and is based on five major air pollutants:
- Ground-level ozone
- Carbon monoxide
- Sulfur dioxide
- Nitrogen dioxide
- Airborne particles (particulate matter)
The two pollutants posing the greatest risk to respiratory health are ground-level ozone and airborne particles. Ground-level ozone is created when sunlight reacts with certain chemicals, such as those emitted from car exhaust or power plants. Airborne particles are small particles suspended in the air, like those that come from wildfire smoke, dust, and volcanic ash.
The AQI is designed for people; however, the classifications have been extrapolated for use in horses.
Equine Respiratory Health
A horse’s respiratory system includes the nasal cavity, trachea, and lungs and is the main body system affected by air pollution.
The respiratory system’s defense mechanisms are responsible for filtering out particles found within the air. Large particles are filtered out in the horse’s upper respiratory tract (the nasal passages and trachea). Smaller particles, however, can enter deep into the lungs and become lodged there, causing irritation and damage.
Additionally, particulate matter and chemicals from air pollution can alter the immune system, which is the body’s natural defense system against damage and disease. When a horse’s immune system is compromised, the lungs are more susceptible to damage from bacteria, pollen, and other foreign materials.
Horses with respiratory health conditions, such as equine asthma, recurrent airway obstruction (heaves), or allergies, are more vulnerable to the effects of air pollution. These horses have an increased risk of lung damage and secondary complications, such as bronchitis or pneumonia, as their airways’ natural defense mechanisms are less effective.
Effects of Smoke Inhalation from Air Pollution in Horses
Smoke is composed of chemicals and particulate matter. Different types of wood, vegetation, houses or buildings, plastics, and other combustible materials all affect the composition of smoke. Many toxic chemicals are produced, some of which can be fatal in high doses and when inhaled over long periods.
The particulate matter found in smoke tends to be very small in size, which allows it to penetrate deep into the lung tissues. For this reason, smoke tends to be more harmful than some other airborne particles, like the dust generated from riding arenas or roads.
Horses that are exposed to wildfire smoke can suffer various degrees of injury ranging from mild irritation to severe lung tissue damage. Owners should carefully observe their horses for any signs of respiratory distress, which include:
- Respiratory rate consistently over 30 breaths per minute at rest (not during or right after exercise)
- Labored breathing (increased effort from the abdomen/rib cage)
- Flared nostrils
- Deep or repetitive coughing
- Nasal discharge that is yellow/white in color
If you notice signs of respiratory distress in your horse, contact your veterinarian as soon as possible.
The symptoms of respiratory distress are notable and most commonly experienced by horses in close proximity to wildfires. But what is less obvious and more common is continued and repeated exposure to air pollution caused by drifting smoke. It is not yet well known how this might affect horses’ athletic performance and long-term health. The best recommendations at this time are to minimize work intensity (and therefore the amount of air pollution inhaled) depending on the AQI.
What Owners Can Do to Protect Their Horses
Should I keep my horse in the barn or outdoors?
While our intentions as owners are good, moving a horse indoors when the air quality outside is poor is not always a healthier option. Most barns are not equipped with air-filtration systems, so the harmful pollutants in the outside air will be found inside as well.
Dust within barns can contribute to high particulate matter and further decrease air quality. The combined effects of dust and poor air quality are further intensified when barns are closed up or ventilation is poor.
Finally, horses that are not accustomed to spending long hours in the barn can become anxious when kept in a stall. They might display behaviors such as weaving, pacing, or pawing to cope with the stress, and they may not eat or drink well. Any nervous activity that increases the respiration rate can lead to increased inhalation of smoke and pollutants.
To determine the safest option, horse owners must consider their facility (and its ventilation system), what their individual horse is used to and his behavior, along with recommendations from their vet.
Is it okay to ride my horse when there’s wildfire smoke?
Activities that elevate a horse’s respiration rate will increase the airflow in and out of the lungs, therefore increasing the number of particles that can penetrate the deeper airways. If the AQI is between 100-150, exercise for horses without existing respiratory issues should be restricted to light work. If the AQI is above 150, skip your ride no matter how healthy your horse may seem. Guidelines for horse shows and competitions suggest canceling if the AQI is above 150.
What should I feed my horse during times of poor air quality?
In general, owners do not need to change their horses’ diet that they are feeding if air quality is poor. Make sure your horse always has access to fresh, clean water. Keeping your horse hydrated will help keep his airways moist and at their best to filter out particles. Consider soaking the hay to reduce dust and pollen which can further irritate airways.
Supplements that may support respiratory health
Along with proper nutrition and hydration, specific ingredients can help support the health and function of the lungs and tissues of the respiratory system. Equine respiratory supplements are formulated specifically to soothe and maintain the health of your horse’s airways and are especially helpful for horses already combatting respiratory issues, like seasonal allergies.
Ingredients such as MSM, bromelain, and quercetin help support a normal inflammatory response. The omega-3 fatty acid DHA (found in fish oil and algae) is shown to have an anti-inflammatory effect on the lungs and therefore may be beneficial for horses with airway syndromes [1]. Spirulina from fresh water blue green algae contains vitamins, minerals, and fatty acids to help support immune function and overall health.
Antioxidants, like vitamin C, N-acetyl cysteine, grape seed extract, and super oxide dismutase, help to maintain respiratory cell health. Specifically, N-acetyl cysteine has been shown to reduce and thin excess mucus production to support healthy respiratory tract function [2]. The herb jiaogulan, with its roots stemming from traditional Chinese medicine, has properties that promote optimal circulation throughout the body and help combat oxidative stress.
Horse Owner Resources
- Get information on the air quality where you live at AirNow.gov.
- Stay up-to-date on wildfires in your area and across the country by visiting the National Interagency Fire Center.
- Share this air quality index for horses with your trainer and barn friends.
Evidence-Based References
- Nogradi, N., Couetil, L. L., Messick, J., Stochelski, M. A., & Burgess, J. R. (2015). Omega-3 fatty acid supplementation provides an additional benefit to a low-dust diet in the management of horses with chronic lower airway inflammatory disease. Journal of veterinary internal medicine, 29(1), 299–306.
- Committee for Veterinary Medicinal Products - European Medicines Agency. (n.d.). Acetyl Cysteine Summary Report. https://www.ema.europa.eu/en/documents/mrl-report/acetyl-cysteine-summary-report-committee-veterinary-medicinal-products_en.pdf