Identify one environmental factor that causes ill health

Answer 1

Second-hand smoke
Asbestos
Air pollution

And more --

http://www.creatinghealth.co.za/index.php?option=com_content&view=article&id=32:causes-of-ill-health&catid=36:caues-of-ill-health&Itemid=38

Answer 2

Pollusion cause ill health within communities