DENVER (KDVR) — An Ozone Action Alert Day has been issued by the the Colorado Department of Public Health and Environment and the Regional Air Quality Council for the Front Range effective 4 p.m. through 4 p.m. on Sunday.

Ozone levels and fine particulate matter concentrations are expected to be in the moderate to unhealthy for sensitive groups categories for about the next 24 hours. Smoke from wildfires in the West has moved into the state, combined with the ozone concentrations has created a haze in the Denver metro area and into the Foothills.

Denver has fluctuated throughout the day in rank as the worst city for air quality, competing with Santiago, Chile and Johannesburg, South Africa.

Officials warn people with heart or lung disease, older adults, and children should avoid extensive time outside and refrain from over exertion.

Public health recommendation during the alert is: “If smoke is thick or becomes thick in your neighborhood you may want to remain indoors. This is especially true for those with heart disease, respiratory illnesses, the very young, and the elderly. Consider limiting outdoor activity when moderate to heavy smoke is present. Consider relocating temporarily if smoke is present indoors and is making you ill. If visibility is less than 5 miles in smoke in your neighborhood, smoke has reached levels that are unhealthy.”