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Ethylene oxide risks rising in hospitals
Exposure also linked to breast cancer
Long-term exposure to ethylene oxide (EtO), even at permissible levels, may be putting hospital workers at increased risk for breast cancer, recent studies suggest.
While other hazards — from severe acute respiratory syndrome (SARS) to smallpox — have taken the spotlight in recent years, the risk from EtO appears to be rising slowly.
It doesn’t take much daily exposure to cause a concern, particularly since 90% of the central processing workers are women. Workers who are exposed to just 1 part per million (ppm) during a daily work shift for 13 or more years show an increased risk of breast cancer.1
"This underscores the importance of monitoring employee exposure," says lead author Kyle Steenland, PhD, professor of environmental and occupational health at the Rollins School of Public Health at Emory University in Atlanta.
Even more troubling, an analysis of that monitoring shows a gradual increase in noncompliance with the short-term exposure limit at hospitals around the country.
In 2001, about 12% of hospitals had exceeded the short-term limit of 5 ppm in a 15-minute period, according to a study of more than 130,000 personal breathing zone samples collected from 1984 to 2001.2
The gradual increase in exposures coincided with a decline in Occupational Safety and Health Administration (OSHA) enforcement, says Anthony D. LaMontagne, ScD, MA, MEd, associate professor at the Centre for the Study of Health & Society at the University of Melbourne in Australia.
In fiscal year 2002, OSHA issued 10 citations related to EtO stemming from four inspections. In 1989, OSHA issued 250 citations from 70 inspections, LaMontagne found. The EtO standard became effective in 1985, requiring monitoring and medical surveillance of workers.
"In the first decade [after the standard was implemented], exposures went down very nicely," LaMontagne says. "Since ’96, short-term exposures are increasing. That is coincident with a steep drop off of OSHA fines, inspections, and enforcement of the ethylene oxide standard.
"We’re backsliding, and people are getting overexposed again," he says. "My evidence suggests that we need to be vigilant in order to protect the gains made in the first decade following the standard."
Rich Fairfax , CIH, OSHA’s director of enforcement, says he was not aware of any decline in enforcement of the EtO standard.
"If that’s the case, it’s something I definitely want to look into," he adds. "In the last several years, we’ve focused in health care on bloodborne pathogens and back and shoulder injuries from resident and patient handling. I’m not aware of us backing off on looking at other hazards in hospitals when we’re in there."
EtO a danger to life and health’
EtO, an ether-like gas, is used to sterilize heat- and moisture-sensitive items. At small concentrations, it is virtually odorless. The National Institute for Occupational Safety and Health (NIOSH) has identified EtO as a substance "immediately dangerous to life or health" and as a "known human carcinogen."
Acute exposures can cause eye pain, shortness of breath, lung irritation, dizziness, nausea, and headaches. It previously has been linked to leukemia, lymphoma, genetic damage, nerve damage, spontaneous abortions, and muscle weakness.
Steenland’s NIOSH-sponsored study was the largest ever to investigate the association between EtO and breast cancer.
Using interviews as well as death certificates, cancer registries, and a review of medical records, researchers tracked breast cancer incidence in 7,576 women who had been employed for at least one year in a commercial medical equipment sterilizing facility. On average, they were exposed to EtO for 10.7 years.
The risk of breast cancer increased with greater cumulative exposure. "The study found a 27% increased risk of breast cancer for those women in the study with the highest level of cumulative exposure to EtO compared to women in the [nonexposed population] data," says co-author Elizabeth Whelan, PhD, chief of the epidemiology section in NIOSH’s Industrywide Studies Branch.
Researchers used SEER (Surveillance, Epidemiology, and End Results) data, a cancer registry compiled by the National Cancer Institute, as a comparison.
"No single study can answer the question about EtO exposure and the risk of breast cancer. The results of this study do suggest, however, that EtO at the highest exposure levels is associated with breast cancer," Whelan adds.
Researchers were unable to locate many of the women who had worked in the facilities, and interviewed 5,139 (68%) of the women included in the study. They also relied on state cancer registries and death certificates, but acknowledge that the lack of a higher response rate was a limitation of the study.
In fact, the number of breast cancers in the EtO-exposed group was likely an undercount, Steenland says. "In the whole cohort [of exposed workers], we know we don’t have all the breast cancers because we couldn’t find everybody."
Still, the study provides enough information to add to health concerns related to EtO. "[Breast cancer] is a much more common disease than leukemia and lymphoma, things that have been implicated before, so that’s worrisome," he says.
Hospitals monitor more than required
OSHA requires employers to monitor the workplace for EtO exposure, but those monitoring rules are somewhat lax, LaMontagne says. The standard requires only initial monitoring. If hospitals find exposures to be less than half the permissible exposure limit (the so-called action level of 0.5 ppm) and below the short-term excursion limit of 5 ppm in a 15-minute period, then they are not required to monitor again unless there are changes in personnel or processes.
Most hospitals monitor employee exposure much more frequently than required — many times in a given year, he says.
LaMontagne recommends monitoring at least quarterly. Analysis of a national database of those monitoring measurements shows that the more frequent monitoring is warranted.
He obtained exposure data from a nationwide commercial vendor and processor of EtO passive dosimeters and analyzed 87,582 work shift and 46,097 short-term personal breathing zone samples from 2,265 U.S. hospitals from 1984 to 2001.
The increase in hospitals exceeding the short-term exposure limit began in 1996, reversing a long decline over the preceding eight years, LaMontagne adds.
The type of sterilizer used and its working order may impact the exposures, he says. For example, in a previous study, he found that sterilizers operating under positive pressure using EtO gas mixtures were associated with accidental releases and exceeding the short-term exposure limit. The increase in exposures occurred in short-term exposures, or those of 5 ppm or more within 15 minutes, LaMontagne explains. Negative-pressure sterilizers using 100% EtO cartridges are associated with less leakage. Combined sterilizer-aerators also have far better safety records in this regard. This type of machine eliminates the need to transfer the sterilized devices to a separate aerator.3
Previous studies also showed that high-exposure accidental releases also occur widely and are rarely picked up in routine exposure monitoring.
In a study of 92 Massachusetts hospitals, LaMontagne found that about one-third had an accidental EtO release and exposure of one or more workers from 1990 to 1992.
Monitoring was being conducted in only one case at the time of the accident — a maintenance worker who had a mishap in changing an EtO cylinder had a measured short-term exposure of 85 ppm. 4
"Seeing an increase in short-term excursions suggests that unmeasured accidental exposures might be going up, too," he cautions.
In addition to regular monitoring, there are a number of steps hospitals can take to protect workers, LaMontagne says:
• Keep your machines in the best possible working order.
• Isolate the machines. "There’s no reason to have workers folding laundry and packing surgical kits beside an EtO sterilizer," he says.
• Reduce your use as much as possible.
• Install an EtO alarm to detect leaks and accidental releases.
• Conduct medical surveillance. OSHA requires the surveillance if workers are exposed above the short-term or work shift action levels. Based on the recent NIOSH-sponsored study, breast cancer screenings should be considered for inclusion in EtO medical surveillance, advises LaMontagne.
1. Steenland K, Whelan E, Deddens J, et al. Ethylene oxide and breast cancer incidence in a cohort study of 7,576 women. Cancer Causes Control 2003; 14:531-539.
2. LaMontagne AD, Oakes JM, Turley RNL. (In press, January 2004.) Long-term ethylene oxide exposure trends in U.S. hospitals: Intervention needed to preserve gains made following 1984 OSHA standard. Am J Public Health 2004; 94.
3. LaMontagne AD, Kelsey KT. Evaluating OSHA’s ethylene oxide standard: Exposure determinants in Massachusetts hospitals. Am J Public Health 2001; 91:412-417.
4. LaMontagne AD, Kelsey KT. Evaluating OSHA’s ethylene oxide standard: Employer exposure monitoring activities in Massachusetts hospitals from 1985 through 1993. Am J Public Health 1997; 87:1,119-1,125.