You could do some searching and see if there are any state or gov maps on various possible toxins or pollutants in your loaction. Then you would have a better idea as to what might be in your area and worth testing for.


Here is one for Radon- some larger cities might have a more detailed map for it.
Red is highest amounts
Orange is moderate
Yellow is low
http://www.epa.gov/radon/pdfs/zonemapcolor.pdf

I'm sure other countries have something similar listed under the governmental environment section.