Because of the location of the three places as people pass through-out and added a lot of symptoms that are toxic or quality surveys are harmful to people in these places?
Because the three locations as a people through - out and entered service a lot. The quality survey may be toxic or dangerous to come to these places or not.
Because the place is the source of the three places people passed through. , and into service a lot. The quality survey of symptoms that toxic or harmful for people in these places, or not.