Vapor intrusion from legacy dry cleaner and industrial solvent sites is exposing residents to TCE and PCE inside their homes, but most states have no mandatory screening program

Trichloroethylene (TCE) and tetrachloroethylene (PCE) — chlorinated solvents used for decades in dry cleaning, metal degreasing, and electronics manufacturing — persist in groundwater plumes beneath thousands of U.S. neighborhoods. These volatile organic compounds migrate upward through soil as vapor, penetrate building foundations through cracks and utility conduits, and accumulate in indoor air at concentrations that cause cancer, liver damage, and neurological harm. The EPA estimates that approximately 20% of U.S. residents live in areas where vapor intrusion could potentially affect indoor air quality. In California alone, the Department of Toxic Substances Control identified 214 sites that are known or suspected vapor intrusion hotspots. In Los Angeles, the former Rocketdyne rocket engine plant in Canoga Park and an industrial dry cleaner called Welch's in Lincoln Heights (shuttered in the 1980s) are still generating groundwater plumes that threaten residential buildings more than 35 years later. The human cost is measurable. At Camp Lejeune, where TCE and PCE contaminated base water from the 1950s through 1987, a study found thyroid, esophageal, and breast cancer rates 20% higher among personnel stationed there, and Parkinson's disease rates 70% higher. The EPA banned all uses of TCE in December 2024, citing Camp Lejeune and other sites as evidence of harm. But banning future use does nothing about the millions of gallons of TCE and PCE already in the ground. Residents living above these plumes often have no idea they are being exposed — symptoms like headaches, dizziness, and fatigue are non-specific and easily attributed to other causes. By the time cancer clusters are identified, exposure has been ongoing for years or decades. This problem persists because vapor intrusion assessment is expensive, technically complex, and governed by an inconsistent patchwork of state regulations. A 2024 review found that state approaches to vapor intrusion vary enormously — some states have mandatory screening requirements, while others have none. There is no federal requirement for vapor intrusion assessment at non-Superfund sites. Many contaminated dry cleaner and industrial sites are regulated under state voluntary cleanup programs that lack the resources or authority to mandate indoor air testing in nearby residences. Property owners and landlords have no obligation in most jurisdictions to test for or disclose vapor intrusion risks. Local planning and building departments are not required to check contamination databases before issuing permits for new construction above known plumes.