Environmental remediation typically adheres to risk standards based on adverse health effects observed in toxicological studies. These can range from immediately dangerous to life and health (IDLH), to burns, to difficulty breathing, and cancer risk factors. The symptoms people are encountering can be a mix of a few different things. Either they may be particularly sensitive (i.e. outside the standard deviations of the toxilogical study) or they may have had an acute exposure when the accident occurred. Current levels show that current exposure to air and groundwater is not a concern. I would say that surface water and soil near the site should be avoided.