At a glance
| Chemical family | A chlorinated volatile organic solvent (tetrachloroethylene); the close cousin of trichloroethylene |
| CAS number | 127-18-4 |
| Classification | IARC Group 2A — probably carcinogenic to humans (bladder cancer, multiple myeloma, non-Hodgkin lymphoma in human studies); EPA "likely carcinogenic"; DHHS "reasonably anticipated" |
| Where you encounter it | The solvent in conventional dry cleaning; freshly dry-cleaned clothes; vapor intrusion near dry cleaners or contaminated sites; contaminated tap water |
| Sleep micro-environment relevance | Dry-cleaned clothes off-gas PERC into the closet and bedroom air; near a dry cleaner it can also enter from the ground by vapor intrusion |
| Activated carbon capture | Adsorbable as a vapor; for clothes the fix is airing out, and for vapor intrusion it is sub-slab depressurization |
What it is
Perchloroethylene — PERC, PCE, or tetrachloroethylene — is a colorless, nonflammable chlorinated solvent that has been the workhorse of dry cleaning for decades, and is also used to degrease metal. Regulatory — ATSDR ToxFAQs, Tetrachloroethylene Most people can smell it at about one part per million in air — which is why a bag of fresh dry cleaning has that characteristic odor. Chemically and toxicologically it sits right beside trichloroethylene: both are volatile, both linger for years in groundwater, and both are classified as probable or known human carcinogens.
IARC places PERC in Group 2A, probably carcinogenic to humans, with human evidence pointing to bladder cancer, multiple myeloma and non-Hodgkin lymphoma; the EPA calls it likely carcinogenic by all routes. Regulatory — ATSDR ToxFAQs, Tetrachloroethylene
How it relates to the bedroom
The closet route: your dry-cleaned clothes
The most universal bedroom exposure to PERC is also the most overlooked. Health agencies state it directly: when you bring clothes home from the dry cleaner, they release small amounts of tetrachloroethylene into the air. Regulatory — ATSDR ToxFAQs, Tetrachloroethylene A suit or dress carries residual solvent in its fibers, and a closet holding several freshly cleaned garments becomes a slow, steady source venting into the bedroom you sleep in. The amount per garment is small, but the closet is a recurring, enclosed reservoir right next to the bed — which is exactly why airing clothes out before they go in makes a measurable difference. Inferred — residual PERC off-gasses from dry-cleaned fabric; airing reduces the reservoir
The vapor-intrusion route: living near a dry cleaner
The second pathway mirrors its cousin TCE. PERC is one of the most common groundwater contaminants — found at 949 of 1,854 EPA Superfund sites — and where it sits under a building it can rise as vapor through the foundation into indoor air. Regulatory — ATSDR ToxFAQs, Tetrachloroethylene Homes near or above dry cleaners are the classic case: in a community over a PERC plume, indoor air varied by an order of magnitude with weather and foundation type, and residential buildings with a co-located dry cleaner can carry substantially higher indoor PERC — a New York City study even tied that exposure to a specific congenital heart defect in children. Peer-reviewed — Johnston & Gibson 2014; Rhee et al. 2025
Reading the risk
Calibrated honestly: PERC is a probable carcinogen with real human cancer signals, plus neurological effects on mood, memory and attention at sustained low levels. Regulatory — ATSDR ToxFAQs, Tetrachloroethylene The dry-cleaned-clothes exposure for most people is modest and very reducible; living above a contaminated plume is the more serious scenario and the one worth testing for. The good news is that both routes have clear, proven responses. Inferred — risk scales with exposure; both pathways are addressable
What the research says
- IARC Group 2A carcinogen. Human signals for bladder cancer, multiple myeloma, non-Hodgkin lymphoma. Regulatory — ATSDR ToxFAQs
- Dry-cleaned clothes off-gas it. A recurring closet source venting into bedroom air. Regulatory — ATSDR ToxFAQs
- Vapor intrusion near dry cleaners. Residential indoor PERC elevated; tied to a childhood heart defect in one study. Peer-reviewed — Rhee et al. 2025
- Neurological effects too. Mood, memory, attention, reaction time and vision at sustained low levels. Regulatory — ATSDR ToxFAQs
What helps reduce it
Air out dry cleaning before it goes in the closet. Remove the plastic and hang garments outdoors, in a garage or a ventilated room for a day before bringing them to the bedroom. Inferred — off-gassing residual PERC outside the closet lowers the bedroom source
Choose PERC-free cleaning. "Professional wet cleaning" and liquid-CO₂ cleaners avoid PERC entirely. Regulatory — ATSDR ToxFAQs
Address vapor intrusion if you're near a source. Test indoor air and, if needed, install sub-slab depressurization — the same fix as for TCE and radon. Peer-reviewed — Johnston & Gibson 2014
What does NOT help
- Leaving cleaning in the plastic bag in the closet. That traps the solvent against the fabric and slows its escape into a space you keep closed. Inferred
- A "low-VOC" mattress. PERC comes from clothes and the ground, not the bed; mattress choice is irrelevant to it. Inferred
Open research questions
- How much a closet of dry-cleaned clothes actually raises bedroom-air PERC over a night, and how fast airing reduces it. Speculation
- The significance of the childhood cardiac-defect signal from residential dry-cleaner proximity. Speculation
Citations
- ATSDR Toxicological Profile / ToxFAQs for Tetrachloroethylene (PERC; CAS 127-18-4), 2019/2020. Dry-cleaning/degreasing solvent; dry-cleaned clothes release PERC into air; IARC Group 2A (EPA likely, DHHS anticipated); bladder cancer / myeloma / NHL signals; neuro effects; 949/1,854 Superfund sites. ATSDR Regulatory
- Rhee J, et al. (2025). Early-life residential tetrachloroethylene exposure and childhood cancer and birth defects. Environment International. Buildings with co-located dry cleaners had higher indoor PERC; association with aortic valve stenosis with exposure-response. Via Consensus. Reference record Peer-reviewed
- Johnston JE, Gibson JM (2014). Spatiotemporal variability of tetrachloroethylene in residential indoor air due to vapor intrusion. J. Expo. Sci. Environ. Epidemiol.. Order-of-magnitude indoor variability over a PERC plume; rises with pressure drops, humidity, slab-on-grade. Via Consensus. Reference record Peer-reviewed
Frequently asked questions
What is perchloroethylene?
Perchloroethylene — PERC, PCE, or tetrachloroethylene — is the colorless solvent used in most conventional dry cleaning and in metal degreasing. It is the chemical behind the distinctive smell of freshly dry-cleaned clothes. It is a close chemical cousin of trichloroethylene, and like TCE it is volatile, persistent in groundwater, and classified as a probable human carcinogen.
How does it get into my bedroom?
Two ways. The everyday route is your closet: freshly dry-cleaned clothes release PERC into the air as they sit, and a closet full of them off-gasses into the bedroom you sleep in — this is stated plainly by health agencies. The second route is vapor intrusion: if you live near or above a dry cleaner or a PERC-contaminated site, the solvent can rise from the ground into your home's air, just as TCE does.
How harmful is it?
PERC is classified by IARC as probably carcinogenic to humans (Group 2A); human studies link it to bladder cancer, multiple myeloma and non-Hodgkin lymphoma, and U.S. agencies treat it as a likely or anticipated human carcinogen. Beyond cancer, longer low-level exposure can affect mood, memory, attention, reaction time and vision. As always, dose matters: the per-garment amount from dry cleaning is small, but it is a recurring source in a closet, and living above a contaminated plume is a more serious exposure.
What should I do about it?
For dry cleaning, the simple habit is to remove the plastic and air out cleaned clothes — ideally outdoors, in a garage, or in a ventilated room — before hanging them in the bedroom closet, and to consider 'wet cleaning' or liquid-CO2 cleaners that don't use PERC. If you live near or above a dry cleaner or contaminated site, indoor-air testing and, if needed, sub-slab depressurization (the same fix used for TCE and radon) address vapor intrusion.
Related compounds
Embr is a sleep environment company researching and addressing the chemistry of the bedroom. Research and product development in progress.
Last reviewed 2026-06-27. If you find a factual error, contact us.