Experts warn those with respiratory difficulties as well as active adults and children should remain inside until air quality improves
Chicago residents have recently observed vibrant, reddish sunsets and hazy skies enveloping the city. These intriguing phenomena can be attributed to a combination of factors, including particulate matter and smoke from Canadian wildfires, as well as pollutants contributing to ground-level ozone.
The outpouring of smoke from the ongoing wildfires in Canada has played a significant role in creating the hazy conditions witnessed in Chicago. According to NASA, over150 wildfires are currently burning in Quebec, with many remaining uncontrolled, causing widespread smoke across several states. Additionally, a wildfire near Grayling, Michigan, has contributed some smoke to the Chicago region.
Lee Carlaw, a meteorologist with the National Weather Service, explains that while the smoke blown into the area is primarily high in the atmosphere, it has led to milky and hazy conditions throughout the Chicago region. However, the poor air quality at ground level on Monday was more directly associated with elevated ozone levels. Ground-level ozone is formed when nitrogen oxide and volatile organic compounds interact with sunlight. The presence of high levels of particulates in the atmosphere, combined with light winds, has further contributed to the lingering haze.
The Illinois EPA declared an Air Pollution Action Day on Monday due to the low air quality. Action days are typically designated when the Air Quality Index (AQI) reaches unhealthy levels. Different air pollution control agencies establish their own thresholds for calling action days.
In certain areas like Chicago, action days are announced when the AQI is forecasted to be "Unhealthy for Sensitive Groups" or Code Orange. In such cases, individuals who are sensitive to pollutants should reduce their exposure by minimizing prolonged or intense physical activity outdoors. For ozone, this includes children, active adults, and individuals with lung diseases like asthma. For particle pollution, sensitive groups comprise individuals with heart or lung diseases, older adults, and children. Occasionally, an action day may be declared even when the AQI is "Moderate" or Code Yellow if the levels are expected to approach Code Orange levels.
Today's AQI for Chicago remains poor, due to particulate matter and small particulate matter, however ground level ozone today is ranked as fair. The associated warning states, "The air has reached a high level of pollution and is unhealthy for sensitive groups. Reduce time spent outside if you are feeling symptoms such as difficulty breathing or throat irritation."