Colorado health authorities issued an advisory on Monday for unhealthy levels of ozone pollution in the Front Range urban corridor along the eastern flank of the Rocky Mountains.

Ozone levels were expected to reach levels that could cause respiratory problems in sensitive individuals, the Colorado Department of Public Health said.

Active children and adults and people with asthma and other lung diseases were advised to reduce prolonged or heavy outdoor exertion through Monday.

EPA TO DESIGNATE 'FOREVER CHEMICALS' AS HAZARDOUS SUBSTANCES

High ozone concentrations were most likely in southern and western parts of metro Denver, including Golden and Highlands Ranch.