Testing soil for herbicides
In general soil testing labs do not test for herbicides. It is expensive to test for this. For specific testing you will have to contact private labs. Google search for "Environmental Testing Services in MD' and/or "Analytical Services in MD" to find some of these labs and talk to them about testing.
You did not mention the herbicides used. At this point, contact your lawn service and find out the active ingredient and name of the herbicides used. Once you have this information contact the National Pesticide Information Center for toxicity http://npic.orst.edu/