County

Ozone scores

2014-2016

2015-2017

2016-2018

Cook

9.8

14.0

19.2

DuPage

3.7

3.7

5.0

Kane

3.0

3.0

4.7

Lake

5.3

6.0

8.0

McHenry

3.3

3.3

5.7