EO Gas: What Sterilizes Your Cartridges, and Who It Actually Harms
Almost every disposable tattoo cartridge you open was sterilized with a gas that is a known human carcinogen.
Ethylene oxide, or EO, lets manufacturers sterilize plastic equipment without destroying it. The biggest exposure concerns are around the sterilization facilities: the workers running them and the people living nearby. Opening a cartridge at the tattoo station is a different situation.
How we used to do it
I built my own needles before cartridges were standard. You soldered the grouping, cleaned the flux off thoroughly to neutralise it, and autoclaved them. Steam under pressure, in-house, done.
That worked because a soldered steel needle on a steel bar does not care about heat. Nothing in it deforms at 121 degrees Celsius and nothing in it breaks down.
A modern cartridge is a different object. It is a precision plastic housing with a membrane, a spring and moving parts, sealed in a plastic blister. Put that through an autoclave and you get a warped, useless cartridge that happens to be sterile.
That is the whole reason EO exists in this industry. It sterilizes at 25 to 55 degrees Celsius, which is low enough that the plastic survives, and it penetrates sealed packaging so the product never has to be opened afterwards.
What the process is
Ethylene oxide is a small, reactive gas. It kills by alkylation: it bonds to the DNA and proteins of any microorganism present and stops them functioning.
The same mechanism is why it is dangerous to people. There is nothing selective about alkylating DNA.
A sterilization cycle has three stages. Preconditioning brings the load to a set temperature and humidity. Gas exposure runs for several hours. Then aeration, which is the part nobody outside the industry knows about: the product is held, often for many hours, to let residual gas diffuse back out of the plastic.
The process is governed by ISO 11135, and the residues left behind by ISO 10993-7.
Who actually carries the risk
Sterilization facility workers. The best-known evidence is a NIOSH cohort of more than 18,000 workers across 14 commercial sterilization facilities, followed for decades. OSHA sets a permissible exposure limit of 1 part per million averaged over eight hours, with a short-term limit of 5 ppm over fifteen minutes.
People living near the plants. In 2016 the EPA reassessed ethylene oxide's cancer potency through its Integrated Risk Information System and concluded it was substantially more potent than previously believed. Subsequent air-toxics screening identified neighbourhoods near commercial sterilizers with elevated modelled cancer risk, which is how this became a national story.
At the tattoo station, opening a package can release whatever trace gas remains after aeration into the room. That exposure should be considered separately from working around sterilizer loads or living near ongoing emissions.
Those are three very different exposures, and conflating them is how the conversation goes wrong in both directions.
Cancer findings and the disagreement over risk
The occupational findings need to be read alongside their limits. The litigation has also produced different outcomes, so a verdict alone cannot settle the exposure question.
The NIOSH cohort found positive exposure-response trends for lymphohematopoietic cancer mortality, particularly in men, and raised breast cancer incidence among exposed women. EPA's reassessment gave EO substantially greater cancer potency than its earlier estimate. In litigation, a 2022 jury awarded 363 million dollars to a plaintiff with breast cancer who lived near Sterigenics in Willowbrook, Illinois. In January 2023, the company settled more than 870 claims for 408 million dollars without admitting liability.
The same NIOSH follow-up found little evidence of excess cancer mortality across the cohort as a whole. A separate study of 7,576 women in commercial sterilization work described inconsistent exposure-response trends and possible bias weakening the breast cancer association. Other researchers have questioned the historical exposure model behind EPA's estimate. Defense verdicts in Pennsylvania, Illinois and Colorado also show that the litigation hasn't produced one outcome.
EO is a recognized carcinogen, with exposure-response findings in some occupational analyses. The size of the risk is disputed, and the court outcomes have gone both ways.
Where it stands right now
In 2024 the EPA finalised a rule covering 88 commercial sterilization facilities, identifying 23 as posing high cancer risk to nearby communities and requiring emission reductions of over 90 percent.
On 13 March 2026 the EPA proposed repealing that rule.
The tension behind that is real and not a conspiracy. EO sterilizes a very large share of single-use medical devices in the United States, and there is no drop-in replacement at that scale. Radiation works for some products and not others. Closing facilities has previously threatened the supply of devices hospitals cannot do without.
That leaves a difficult balance between reducing emissions and keeping medical devices available. I don't think the findings in this article settle where that balance should land.
What reaches you, and what reaches the client
Residual ethylene oxide in the device, plus ethylene chlorohydrin, which forms when EO meets chloride. Both are limited by ISO 10993-7.
For limited-contact devices, meaning under 24 hours, the standard caps EO at 4 milligrams and ethylene chlorohydrin at 9 milligrams for the whole device. Aeration is what brings products under those caps, and it is validated rather than assumed.
EO is a gas. Whatever trace remains in the plastic after aeration leaves it as gas, into the air of your room. It does not meaningfully end up in the ink sitting in your cap, and it is not being carried into the client through the needle. If there is an exposure at the workstation at all, it is you breathing a trace amount at the moment the package opens, not the person in the chair.
The residual limits and aeration process are meant to control what remains when a device reaches the user. They don't provide a measurement for every cartridge at every tattoo station. I wouldn't equate opening a compliant package in a ventilated room with the sustained exposures studied at sterilization plants.
The framework matters more than the number anyway. Those residual limits were written for medical devices used on patients, which is the right standard to borrow. A tattoo cartridge is a limited-contact device by that definition, and it should be held to it.
What this means for you
Ask your supplier how the cartridges are sterilized and what validation supports that process. EO and radiation are both used. If a package is damaged or its seal is broken, discard it because the sterility claim depends on the package staying intact.
The occupational and neighborhood exposures still deserve attention. Using a sterilized cartridge doesn't make those emissions someone else's problem, but it also doesn't make the client's exposure equivalent to living beside a plant.
For the separate question of what the cartridge plastic itself might shed during use, see do tattoo supplies shed plastic? That is a particle question rather than a gas question, and the two should not be mixed up.
Sources
FDA: ethylene oxide sterilization for medical devices
US EPA: hazardous air pollutants, ethylene oxide
OSHA: ethylene oxide, occupational exposure limits
Litigation overview: ethylene oxide and medical device sterilization, including defence verdicts
Reporting on the 2024 EPA rule and the March 2026 proposed repeal
This article combines published research, regulatory documents and my own history building needles. The epidemiology is contested and I have tried to represent both directions rather than pick the version that makes a better headline. Nothing here is medical or legal advice.
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