Regulatory concern about "vapor intrusion" from soil or groundwater into the breathing space of buildings has expanded over the years to include radon, landfill gas, methane and hydrogen sulphide from oil deposits, oil field operations, or animal husbandry operations to petroleum products and chlorinated solvents. The field continues to evolve, with new theories, guidelines, models and mitigation and remediation requirements. Wactor & Wick attorneys have extensive experience evaluating and creating innovative solutions to the legal risks of acquiring, developing, financing, leasing, owning and selling sites with such issues.