Vapor Intrusion: The Invisible Threat Beneath 460 U.S. ZIP Codes
An independent data analysis of EPA Superfund records reveals that hundreds of neighborhoods sit directly above volatile organic compound (VOC) plumes — and most residents have never been told. Here is what the data shows, what it means for your home, and what you can do.
The Data: VOC Contamination by the Numbers
ToxIndex analyzed 42,354 U.S. ZIP codes against EPA Superfund and Facility Registry data. The results show a concentrated pattern of volatile organic compound contamination, driven primarily by legacy dry cleaning operations and industrial solvent use.
Data: EPA Superfund Enterprise Management System (SEMS), analyzed by ToxIndex. Updated May 2026.
What Is Vapor Intrusion?
Vapor intrusion is the migration of volatile chemical vapors from contaminated soil and groundwater into overlying buildings. Unlike water contamination, which requires you to drink affected water, vapor intrusion exposes residents through breathing indoor air — 24 hours a day, 365 days a year.
The most common sources are:
- Former dry cleaners — PCE (tetrachloroethylene) was the industry-standard solvent for decades. Spills, leaks, and routine disposal contaminated soil beneath thousands of strip malls and adjacent residential lots.
- Manufacturing facilities — TCE (trichloroethylene) was widely used as a metal degreaser. Plumes can migrate underground for miles from the original source.
- Gas stations and fuel storage — Benzene and other fuel-related VOCs can vaporize from contaminated groundwater into nearby structures.
The EPA estimates that vapor intrusion may affect tens of thousands of residential properties nationwide, many of which have never been assessed.
Highest-Risk ZIP Codes for VOC Contamination
These ZIP codes scored 10/10 on the ToxIndex hazard scale for volatile organic compounds. Each has at least one EPA-tracked contamination source within immediate proximity to residential areas.
| Location | ZIP | Score | Contaminant | |
|---|---|---|---|---|
| Berlin, MA | 01503 | 10.0/10 | PCE/PERC | View Report |
| Westborough, MA | 01581 | 10.0/10 | PCE/PERC | View Report |
| Worcester, MA | 01602 | 10.0/10 | PCE/PERC | View Report |
| Amesbury, MA | 01913 | 10.0/10 | PCE/PERC | View Report |
| E. Wareham, MA | 02538 | 10.0/10 | PCE/PERC | View Report |
| Manchester, NH | 03101 | 10.0/10 | VOCs | View Report |
| Nashua, NH | 03060 | 10.0/10 | TCE | View Report |
| Woburn, MA | 01801 | 10.0/10 | TCE | View Report |
Check Your ZIP Code
Enter your ZIP to see if volatile organic compounds have been detected near your home.
How VOCs Enter Your Home
Volatile organic compounds in soil and groundwater exist as dissolved chemicals. As groundwater moves beneath a building, these chemicals vaporize and rise through the soil column. They enter structures through:
- Foundation cracks — Even hairline cracks in concrete slabs or basement walls provide pathways
- Utility penetrations — Gaps around pipes, electrical conduits, and sewer lines
- Sump pits — Open or poorly sealed sump pits act as direct conduits
- Permeable concrete — Standard residential concrete is not gas-tight
Indoor concentrations can be 10 to 100 times higher than outdoor levels because buildings act as vapor collectors, trapping and concentrating chemicals that would otherwise dissipate in open air.
What Remediation Costs
If vapor intrusion is confirmed in your home, mitigation options range from simple to comprehensive:
Sub-slab depressurization (SSD) is the most common approach — identical in principle to radon mitigation systems. A fan creates negative pressure beneath the foundation, drawing vapors away before they enter the living space. These systems are effective, relatively affordable, and can be installed in 1-2 days.
Important: If your home is near an EPA Superfund site, the Potentially Responsible Party (PRP) or the EPA itself may be required to fund your mitigation. Contact your regional EPA office or a HUD housing counselor for assistance.
Disclosure Laws and Your Rights
Environmental disclosure requirements vary significantly by state, but several federal protections apply nationwide:
- CERCLA (Superfund Law) — Requires notification of residents within a defined radius of National Priorities List (NPL) sites
- RCRA — Requires facilities handling hazardous waste to report releases
- State disclosure laws — Most states require sellers to disclose known environmental hazards on the property, though enforcement varies
If you purchased a home near a contamination site and were not informed, you may have legal recourse. Document your discovery, request environmental records from your state agency, and consult a real estate attorney who specializes in environmental disclosure.
Frequently Asked Questions
Vapor intrusion occurs when volatile organic compounds (VOCs) from contaminated soil or groundwater migrate as gases into buildings through cracks in foundations, utility penetrations, and sump pits. For homeowners, this means toxic chemicals like trichloroethylene (TCE) and tetrachloroethylene (PCE) can accumulate in indoor air to concentrations that exceed EPA safety thresholds, often without any visible sign or odor.
Your home may be at risk if it is located within 1 mile of a current or former Superfund site, dry cleaner, gas station, or industrial facility that used chlorinated solvents. Use the ToxIndex ZIP code search above to check your area.
Residential mitigation typically costs between $3,000 and $30,000. Sub-slab depressurization systems average $3,000-$8,000. Full vapor barriers with active ventilation can reach $15,000-$30,000. Some state programs offer financial assistance for homes near Superfund sites.
Disclosure requirements vary by state. Most states require sellers to disclose known environmental hazards. However, many legacy contamination sites predate disclosure laws. If you suspect non-disclosure, contact your state environmental agency or a real estate attorney.
Both are chlorinated solvents (VOCs). PCE (perchloroethylene) was primarily used in dry cleaning. TCE (trichloroethylene) was used in metal degreasing. Both migrate through soil and groundwater and can enter homes through vapor intrusion.
Data Sources: U.S. Environmental Protection Agency (EPA), Superfund Enterprise Management System (SEMS). Facility data from EPA Facility Registry Service (FRS). Analyzed and structured by ToxIndex.
This analysis is based on publicly available government data and does not constitute medical, legal, or real estate advice. For site-specific assessments, contact your state environmental agency or visit EPA Vapor Intrusion.