Due to severe wildfires in recent years—including the devastating L.A. wildfires this past January—both people and animals have been exposed to unhealthy air containing wildfire smoke and its hazardous particulates. At less than one micron in diameter, these particulates are extremely small, which allows them to reach and settle in the lung’s deepest airways. And because horses have such massive lungs compared to other mammals, these minute particulates can pose greater health concerns for our equine athletes than their coarser counterparts in arena or road dust.
In the wake of the increasing number and severity of wildfires in the U.S., University of California-Davis equine specialists explain why smoke poses a danger to equines, how to assess and treat smoke inhalation and provide measures you can take to protect your horse.
What Makes Wildfire Smoke Dangerous
Smoke is composed of carbon dioxide, carbon monoxide, particulate matter (the mixture of solid particles and liquid droplets found in the air), soot, hydrocarbons and other organic substances, including nitrogen oxides and trace minerals. In general, particulate matter is the major pollutant of concern in wildfire smoke.
The composition of smoke also depends on the burned material. Different types of wood, vegetation, plastics, house materials and other combustibles all produce unique compounds when burned. Carbon monoxide—a colorless, odorless gas—is produced in the greatest quantity during a fire’s smoldering stages and can be fatal in high doses.
How Smoke Affects Horses
Horses exposed to fire smoke can suffer respiratory injury of varying degrees, ranging from mild irritation to severe smoke inhalation-induced airway or lung damage. The dangerous particulates can cause burning eyes, a runny nose and illnesses such as bronchitis. They can also aggravate heart and lung diseases such as congestive heart failure, chronic obstructive pulmonary disease, emphysema and asthma.
Additionally, smoke irritates the respiratory tract, reduces lung function and can aggravate conditions like heaves (recurrent airway obstruction). High concentrations of particulates can cause persistent cough, increased nasal discharge, wheezing and increased physical effort in breathing. Particulates can also alter the immune system and reduce the lungs’ ability to remove foreign materials like pollen and bacteria.
Assess and Treat Smoke Inhalation in Horses
Knowing what’s normal in your horse’s respiratory health versus what’s cause for concern can help you determine whether your veterinarian needs to evaluate your horse. Respiratory rate in horses at rest should be between 12 and 24 breaths per minute.
Horses should be examined by a veterinarian if any of the following are noted:
- Respiratory rate is consistently greater than 30 breaths per minute at rest
- Nostrils have obvious flaring
- Horse shows obvious increased breathing effort in the abdomen and rib cage
- Repetitive or deep coughing
- Abnormal nasal discharge
- Horses should also be monitored for skin and tissue injury, especially for the first few days after exposure.
Protect Your Horse from Air Pollution
- Limit exercise when smoke is visible. Horses should not engage in activities that increase airflow in and out of the lungs. This can trigger bronchoconstriction (narrowing of the small airways in the lungs).
- Provide plenty of fresh water close to where your horse eats. Horses drink most of their water within two hours of eating hay, so having water close to his feeder will help increase water consumption. Water keeps airways moist to allow the windpipe and large and small airways to clear inhaled particulate matter from smoke. When airways are dry, the particulate matter remains in the lung and air passages.
- Limit dust exposure by feeding dust-free hay or soak it before feeding. This reduces mold, fungi, pollens and bacteria in the dust that can be difficult for the lungs to clear.
- If your horse is coughing or having difficulty breathing, contact your veterinarian. She can determine the difference between a reactive airway from smoke and dust versus a bacterial infection, bronchitis or pneumonia. If he has a history of heaves or recurrent airway problems, he’s at risk of secondary problems like bacterial pneumonia.
- Contact your veterinarian if your horse has primary or secondary problems with smoke-induced respiratory injury. She can determine if he needs intravenous fluids, bronchodilator drugs or nebulization to facilitate hydration of the airway passages. Your veterinarian may also recommend tests to determine whether your horse has a secondary bacterial infection that could be contributing to his current respiratory problem.
Additional Considerations
- Always have an emergency evacuation plan for your horses, as wildfires can spread so rapidly there’s often little time to prepare.
- Give your horse ample time to recover from smoke-induced airway insult. Airway damage resulting from wildfire smoke can take four to six weeks to heal. Ideally, plan on giving your horse at least that amount of time off after all smoke has cleared and the air quality has returned to normal. Attempting exercise before then could aggravate the condition, delay healing and compromise your horse’s performance for weeks or months. Like people and other animals, horses experience irritation from smoke particulates, but should recover from the effects over time.
- Air quality index (AQI) is used to gauge exercise event recommendations for human athletes. It may be reasonable for equine athletes as well. The National Collegiate Athletic Association lists the following recommendations on their website: “Specifically, schools should consider removing sensitive athletes from outdoor practice or competition venues at an AQI over 100. At AQIs over 150, athletes should be closely monitored. All athletes should be removed from outdoor practice or competition venues at AQIs of 200 or above.”
About Kent Pinkerton, PhD
Kent Pinkerton, PhD, is a professor in both the medical and veterinary medical schools at the University of California-Davis. His research is focused on the health effects of inhaled environmental air pollutants that can alter respiratory, cardiovascular and neurological structure and function.
