What legal rights do I have for my son if he got sick from potential benzene exposure at a construction site nearby?

If you haven't already done so, you should certainly report this incident to the Environmental Protection Agency (EPA). The EPA government is a government organization that is responsible in monitoring and analyzing the environment, conduct research, and work closely with state and local governments to devise pollution control policies. If you suspect that the construction site may be the source of your son's benzene exposure, the EPA would be able to conduct an investigation to determine the source of the toxin.

If the construction site was the source of the benzene, you may seek civil action to gain compensation for the injury to your son. It is required by law for someone to act with the prudence that a reasonable person would exercise under the same circumstances.  In this case, this circumstance would possibly be using caution to prevent the airborne exposure of benzene.  Any violation of this would constitute negligence, which makes a party liable to pay for the damage caused to the injured party.  Your son may have been harmed due to the negligence of the construction company.  Moving forward, it would be best to consult with an Environmental Lawyer to determine the best course of action for your case.