Rising ozone levels through the rest of Wednesday could result in air that’s unhealthy for sensitive groups.

The Louisville Metro Air Pollution Control District has issued an Air Quality Alert for ozone, saying the air pollution could affect young children, the elderly and people with respiratory ailments like asthma and COPD.

This is the year’s first official Air Quality Alert—where residents are given advance warning—though ozone levels were also unexpectedly high on Monday.

This year marks the first ozone season where Louisville will be subject to stricter federal ozone standards, and subject to a limit of 70 parts per billion. The previous standard was 75 parts per billion.