You might consider leveraging the data science component to help target the testing. For example, based on location, house age, construction type (basement/slab/etc.), run the numbers and balance the risk of exposure against the cost of a test. Then recommend "For your house, lead in the ground soil and asbestos in the shingles are the highest risk."

See, for example, this (unfortunately now defunct) radon risk website: http://www.columbia.edu/cu/pr/00/01/radon.html

Data science might also help you recommend where to sample.

Trouble with all this, of course, is collecting enough data to start making useful recommendations.