A wildfire is an unplanned fire that burns in a natural area such as a forest, grassland, or prairie. Humans are the primary cause of wildfires, responsible for more than 90% of forest fires around the world.

Some of the careless human activities that cause wildfires include unattended campfires, discarded cigarettes, and arson. Natural disasters cause roughly 10% of the world’s forest fires. The two primary natural causes of fires are volcanic eruptions and lighting, but the extent of the wildfire will depend on topography, vegetation type, and weather.

Wildfires or forest fires can have significant impact on mortality and morbidity depending on the size, speed and proximity to the fire, and whether the population has an advanced warning to evacuate.

Wildfire smoke is a mixture of air pollutants of which particulate matter is the principal public health threat.

Infants, young children, women who are pregnant, and older adults are more susceptible to health impacts from smoke and ash, which are important air pollutants. Smoke and ash from wildfires can greatly impact those with pre-existing respiratory diseases or heart disease. Firefighters and emergency response workers are also greatly impacted by injuries, burns, and smoke inhalation.

Beyond fatalities, wildfires, and the resulting smoke and ashes, can cause:

• Burns and injuries
• Eye, nose, throat, and lung irritation
• Decreased lung function, including coughing and wheezing
• Pulmonary inflammation, bronchitis, exacerbations of asthma, and other lung diseases
• Exacerbation of cardiovascular diseases, such as heart failure

Wildfires also release significant amounts of mercury into the air, which can lead to impairment of speech, hearing, and walking, muscle weakness, and vision problems for people of all ages.