2021 was a record-breaking year for wildfires. In the United States and Canada alone more than fifteen million acres of land were affected. In the preceding year Australia experienced an unprecedented wildfire season in which forty-six million acres burned. Wildfires are expected to become increasingly frequent in this century due to the effects of human-caused global climate change.
In 2021 a large international team of researchers reported their discovery of a potential link between smoke from wildfires and ozone pollution in urban areas. The researchers were working as part of a joint project between NASA and the National Oceanic and Atmospheric Administration. The chemistry of wildfire smoke is difficult to study from the ground or a satellite by remote sensing. So, the researchers monitored the composition and complex chemistry of wildfire smoke plumes by flying directly through them with a NASA jet outfitted with an array of analytic instruments.
The researchers found that wildfire plumes contain the chemical nitrous acid. When nitrous acid is exposed to sunlight, it breaks down into nitric oxide and hydroxyl. These substances react with airborne organic compounds, also produced by the fire, to make ozone.Ozone production may get even worse when wildfire smoke reaches urban areas. Here, the air is already rich in reactive nitrogen oxides produced by the burning of fossil fuels by sources such as cars and trucks. By the same chemical pathways, these substances may lead to the production of more ozone when they mix with airborne organic compounds from the fire. Ozone pollution is a serious urban problem since ozone irritates the lungs, and can aggravate asthma and other lung diseases.