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Phoenix's notorious haze is visible in a brown layer along the horizon. Ethylene oxide is invisible.EXPAND
Phoenix's notorious haze is visible in a brown layer along the horizon. Ethylene oxide is invisible.
Elizabeth Whitman

Where Do Such High Levels of Ethylene Oxide in Phoenix Come From?

Levels of ethylene oxide, a carcinogenic gas, are higher in the Phoenix metro area than in any other cities with monitoring sites across the country, preliminary federal data shows, but it's a mystery to local and state agencies as to where it's coming from.

In Maricopa County, just four facilities currently emit ethylene oxide, which they use primarily to sterilize medical equipment. In the past 25 years, a total of 23 facilities in the Valley have ever reported ethylene oxide emissions, according to data from the county's air quality department.

But those facilities don't explain it all.

“If you looked at the poundage that is coming from those facilities, and extrapolate out how much air there is, and the concentration, you’d find that there’s a very minuscule fraction coming from the facilities,” Richard Sumner, permitting chief for the county's air quality department, told Phoenix New Times.

In other words, the concentrations measured in Phoenix's air — 0.397 micrograms per cubic meter at one state monitor, and 0.345 at another — are too high to derive solely from hospitals and sterilizing companies.

"It's probably being chemically formed in some manner," Sumner suggested.

At some time in the near future, the Environmental Protection Agency is planning to add more monitors that can measure ethylene oxide, and the Arizona Department of Environmental Quality is working with Maricopa County "to identify potential sources," said Erin Jordan, an ADEQ spokesperson.

ADEQ is also reviewing statewide data "to determine if potential sources are located in other communities," Jordan added.

The EPA expects to offer grants "soon" to fund more monitors; once that announcement is made, ADEQ will review what it would take to apply for that funding, Jordan said. "ADEQ is committed to having a full understanding of these emissions," she said.

Air-quality permit data show that two of the current emitters are hospitals — Banner University Medical Center and the Mayo Clinic Hospital. The other two are the industrial sterilizers American Contract Systems, headquartered in Minneapolis, and Stryker Sustainability Solutions, based in Tempe.

Of the 23 facilities that have sent the reactive, flammable ethylene oxide into Valley air in the past quarter century, nearly all were hospitals and medical centers, although one IT company, Ensono, made the list, along with Medtronic, a medical technology company, and American Contract Systems.

Chronic exposure to the chemical is associated with the development of cancer and other serious health problems. Several facilities in the Valley have either phased out their use of the chemical or are in the process of doing so.

Last year was the final year that the Carl T. Hayden Veterans' Administration Medical Center used ethylene oxide, county data and a spokesperson for the facility confirmed show.

"While ethylene oxide sterilizers have been used by hospitals for decades, VA is working to find alternatives to ethylene oxide use nationwide," Cindy Dorfner, a spokesperson for the Phoenix VA hospital, told New Times via email. "That’s why in January 2019, Phoenix VAMC began using a safe alternative for sterilization of reusable medical equipment."

Instead of ethylene oxide, it is using a hydrogen peroxide base that sterilizes equipment in an hour, Dorfner said.

Banner University Medical Center, which has used decreasing amounts of the chemical since the early 2000s, plans to stop entirely by the end of 2019.

"While most of our sterilizers utilize steam, we do have two ethylene oxide machines at Banner – University Medical Center Phoenix that are required to sterilize certain medical instruments," said Nancy Neff, a spokesperson for Banner.

"Because these machines utilize an [ethylene oxide] abater, which captures 99.9 percent of emissions, only trace amounts — if any — are released in the atmosphere," she added. She did not address a question about why Banner was phasing out its use of the chemical.

Indeed, county data shows that Banner released 0.6 pounds of ethylene oxide into the atmosphere in 2018, the most recent year for which emissions data were available. 

That year, American Contract Systems emitted by far the most ethylene oxide — a whopping 2,908 pounds of it.

The other three facilities combined — Banner University Medical Center, the Carl Hayden VA center, and Stryker — emitted about 70 pounds.

In the last 15 years, just one of those facilities has violated air-quality rules, according to documents obtained through a public records request. It was Stryker, in 2014, and it received a notice of violation for missing a deadline to test an ethylene oxide scrubber. The Maricopa County Air Quality Department considered the problem "corrected" not long afterward, when the company scheduled the requisite test.

A spokesperson for Stryker did not respond to a question about the violation.

The Maricopa County Air Quality Department regulates ethylene oxide in accordance with Environmental Protection Agency rules. It is one of 187 hazard air pollutants, which the Clean Air Act requires the agency to regulate.

The current rules for facilities vary by amount of ethylene oxide used; businesses that use one ton or more are supposed to use a sterilization chamber vent to reduce ethylene oxide emissions to the atmosphere by 99 percent. EPA is now working on changing those rules.

"EPA is reviewing our regulations for facilities that emit ethylene oxide," agency spokesperson Enesta Jones told New Times. It is starting with regulations applicable to some chemical manufacturers, for which it issued a proposed rule on November 6, and regulations for commercial sterilizers.

For the latter rules, in the coming weeks EPA plans to lay out approaches it could take in those new rules, as well as technologies facilities could use to limit ethylene oxide emissions, Jones said.

The agency also plans to request information from "several" commercial sterilization companies, "including data on specific facility characteristics, control devices, work practices, and costs associated with installation and operation of emission reduction measures," she said in an email.

In mid-November, the EPA published preliminary data collected over six months from 18 monitoring sites in cities across the U.S. that are part of two networks for monitoring toxins in the air. Those networks — the National Air Toxics Trends Monitoring Stations and the Urban Air Toxics Monitoring Program — do not home in on industrial sources of pollutants, but instead are supposed to track declines in toxic substances in the air.

Those results indicated that the air in Phoenix, which was the only city to have a stations in each network, had the highest concentration of ethylene oxide out of all 18 stations. The EPA has maintained that six-month averages should not be compared with long-term health benchmarks, even though it admitted that the long-term health effects of those amounts are unknown.

This article has been updated to correct the number of years over which 23 facilities reported ethylene oxide emissions. It is 25 years, not 15.

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