“Perc” most commonly refers to perchloroethylene, a colorless liquid solvent used primarily in dry cleaning, metal degreasing, and chemical manufacturing. The term is also street slang for Percocet, a prescription painkiller. This article covers both meanings, starting with the industrial chemical.
Perchloroethylene: The Dry Cleaning Solvent
Perchloroethylene (also called PCE, tetrachloroethylene, or simply perc) is a powerful solvent that dissolves grease, oil, and wax without using water. Its largest industrial use is producing fluorinated compounds, including refrigerants. Beyond that, it shows up across a surprisingly wide range of applications: dry cleaning garments, degreasing metal parts in manufacturing, cleaning tanker vessels, and serving as an ingredient in brake cleaners, adhesives, sealants, and lubricants. Petroleum refineries use it as a processing aid during catalyst regeneration, and aerospace manufacturers use it in chemical milling.
Dry cleaning is the use most people encounter. Perc strips oils and stains from fabrics that would shrink or bleed in water, making it especially effective on wool, silk, and rayon. For decades it was the industry standard, handling virtually every type of garment and stain.
Why Perc Is Being Phased Out
The EPA classifies perchloroethylene as “likely to be carcinogenic to humans by all routes of exposure,” based on strong evidence from animal studies and suggestive evidence in people. Exposure has been linked to liver tumors, brain gliomas, kidney cancer, and testicular cancer. It is also a confirmed neurotoxicant.
These findings have driven regulatory action. California banned perc in dry cleaning operations entirely as of January 1, 2023. A federal rule finalized in late 2024 under the Toxic Substances Control Act imposes new restrictions nationwide, targeting both commercial dry cleaners and industrial users. The direction is clear: perc’s role in everyday commerce is shrinking.
Health Effects of Exposure
Perc targets four systems in the body: the brain and nervous system, the liver, the kidneys, and the reproductive system. Short-term and long-term exposures produce different patterns of harm.
Acute (Short-Term) Effects
Breathing perc at concentrations of 100 to 200 parts per million causes irritation of the skin, eyes, and airways, along with nausea, vomiting, and diarrhea. Nervous system effects begin at even lower levels. At 50 to 300 ppm, people experience dizziness, lightheadedness, headaches, impaired concentration, and difficulty with coordination. At higher concentrations, loss of consciousness can occur.
Chronic (Long-Term) Effects
Workers with prolonged perc exposure, particularly in dry cleaning, show measurable organ damage. Vision and cognitive function are the neurological areas most commonly affected. Liver damage appears as cell injury and organ enlargement. Kidney effects show up as signs of tubular damage, meaning the tiny structures that filter waste begin leaking proteins they normally retain. Cross-sectional studies of dry cleaning workers have consistently found higher rates of these changes compared to people not exposed to chemical solvents.
How People Are Exposed
Most perc released into the air comes from the dry cleaning industry. The average outdoor concentration across the United States is typically below 1 microgram per cubic meter, a very low level. But the picture changes dramatically for people who live or work in specific settings.
Residents of apartments located above dry cleaning shops can breathe significantly elevated levels of perc in their indoor air. Perc also contaminates groundwater and soil at sites where it has been spilled or improperly disposed of. From contaminated soil or groundwater, it can migrate upward as vapor and seep into homes through cracks in foundations, a process called vapor intrusion. Even freshly dry-cleaned clothing releases small amounts of perc into the air of your closet and home.
If you suspect exposure, biological monitoring can detect perc in blood and exhaled breath, and a breakdown product called trichloroacetic acid appears in urine. These markers drop noticeably after just two days without exposure, so the timing of testing matters.
Safer Alternatives to Perc in Dry Cleaning
Three main alternatives have emerged as the industry moves away from perc, each with trade-offs.
- Professional wet cleaning uses water with specialized detergents and computer-controlled machines. It eliminates air pollution and soil contamination and costs roughly the same as perc cleaning. The downsides: wools, silks, and rayons are more prone to shrinkage or color bleeding, and greases and waxes are harder to remove. It is also more labor-intensive and requires highly skilled operators.
- Petroleum-based solvents are generally less toxic than perc, with lower vapor levels because they evaporate more slowly. They handle all garment types effectively. The major drawback is flammability, which perc does not pose. Drying times are longer, and the solvents can support bacterial growth that causes odors.
- Liquid carbon dioxide cleaning uses pressurized CO2 as a solvent. It eliminates soil contamination and air pollution, offers shorter cycle times, and works well on suede and leather. However, the equipment is expensive, operates under high pressure (creating safety considerations), and may struggle with protein-based stains like grass or lipstick.
No single alternative matches perc’s versatility across every fabric and stain type, which is one reason the transition has taken decades. But the combination of these methods now covers the vast majority of what perc once handled alone.
Perc as Slang for Percocet
In a completely different context, “perc” is slang for Percocet, a prescription painkiller that combines oxycodone (a potent opioid) with acetaminophen. It is prescribed for moderate to severe pain, typically after surgery, injury, or for conditions where non-opioid painkillers are not effective enough.
Oxycodone works by binding to opioid receptors in the brain and spinal cord, reducing the perception of pain. The immediate-release form is FDA-approved for both acute and chronic pain. An extended-release version exists for patients who need around-the-clock pain management when no other options are adequate. An abuse-deterrent formulation has also been approved, designed to resist crushing or dissolving for misuse. Oxycodone carries significant risks of dependence and is a controlled substance.