NIOSH to study safety of ortho-phthalaldehyde

Substitutes not always better

Glutaraldehyde Use Survey (PDF)

The dangers of glutaraldehyde are well known and well studied — from skin irritation to occupational asthma. Switching to another substance would seem to be the best way to protect workers.

But experts in chemical hazards are cautioning health and safety officials to maintain a high level of protective measures with the substitute, ortho-phthalaldehyde (OPA). The National Institute for Occupational Safety and Health (NIOSH) has launched a two-year, multihospital study to investigate the potential hazards associated with OPA.

"On the surface, it seems fairly simple. Substitute a chemical with another chemical," says Jim Boiano, MS, CIH, industrial hygienist in the NIOSH surveillance branch in Cincinnati and assistant coordinator for the health care and social assistance sector for NIOSH's National Occupational Research Agenda. "With glutaraldehyde and OPA, there are a number of factors that come into play."

OPA has a low vapor pressure, which means health care workers may have less exposure to the aerosolized substance. It also is used in lower concentrations than glutaraldehyde (0.55% compared to 1% to 50% solutions).

Yet OPA and glutaraldehyde have similar structural and reactive properties,1 according to an analysis by Karen Rideout, who was then a master's student at the University of British Columbia. Little research has been conducted on the potential occupational hazards of OPA, Boiano says. (OPA is marketed as Cidex OPA by Advanced Sterilization Products, a division of Johnson and Johnson of New Brunswick, NJ.)

NIOSH cannot make recommendations on the use of a chemical without data, says Mark Toraason, PhD, toxicologist and senior service fellow with NIOSH's Division of Applied Research and Technology in Cincinnati and principal investigator of the OPA study.

The study will include health hazard evaluations at hospitals that use OPA. Researchers will conduct wipe tests of surfaces, air sampling, and will look for biomarkers in the urine and blood of workers. They will note workplace characteristics and work practices.

Meanwhile, health care workers should exercise caution, says Toraason. "No one has come up with a [disinfecting] solution that's so selective that is harmful to bacteria but totally safe for humans," he says. "This is a material that has to be handled with caution."

In fact, hospitals should learn a lesson from other industries in which substitutes later were found to present a new set of hazards, says

"If we don't look at hazards with substitution products, we run into the same old problems," says Mark Catlin, industrial hygienist with the Service Employees International Union in Washington, DC. "It's not clear that substitutes are safe substitutes."

When Kaiser Permanente, based in Oakland, CA, switched to OPA, the health system used the "precautionary principle," says Erica Stewart, CIH, HEM, project manager with Kaiser Permanente National Environmental Health and Safety.

"We don't know what the health effects are, so we're going to treat it as if it's as irritating as glutaraldehyde," she says. "We require the same ventilation controls in areas that use OPA."

The equipment processing rooms have negative-pressure, nonrecirculating exhaust and 12 air exchanges per hour, she says.

Stewart cites the report of anaphylaxis in nine patients who had undergone repeated cystoscopies with instruments that had been disinfected with OPA. In 2004, Advanced Sterilization Products issued an alert and advised that OPA should not be used on instruments for patients with a history of bladder cancer:

"In rare instances, CIDEX OPA Solution has been associated with anaphylaxis-like reactions in bladder cancer patients undergoing repeated cystoscopies. Therefore, ASP is contraindicating the use of CIDEX OPA Solution for the reprocessing of any urological instruments to be used on patients with a history of bladder cancer. Additionally, we received reports that, in rare instances, health care workers experienced an irritation or possible allergic reaction that may be associated with exposure to CIDEX OPA Solution. It appears that in most of these cases, the health care workers were not using the product in a manner consistent with the Instructions for Use." (

There also was a 2006 case report of occupational asthma and dermatitis of a nurse in an endoscopy unit in Japan that was linked to exposure to OPA. "This case indicates that OPA itself can be a powerful sensitizer, suggesting that widespread use of OPA as a substitute for GA [glutaraldehyde] may result in serious health risks for workers," the authors concluded.3

Chemical safety experts offer the following advice to ensure worker safety:

  • Look beyond the MSDS. Employers are required to make the Material Data Safety Sheets available to employees, including information on hazards, safe handling practices and spill response. But the quality of information on the MSDS may vary significantly. When a new chemical is introduced into the hospital, Stewart conducts a literature search and looks for other sources of information. She also compares the chemical structure to current chemicals with known properties. "Just because there isn't any [occupational hazard] information shown on an MSDS doesn't mean it's completely safe," she says.
  • Conduct a hazard analysis. Employers are required to assess the workplace for hazards as part of the Personal Protective Equipment standard of the U.S. Occupational Safety and Health Administration, notes Boiano. That would encompass any areas in which potentially hazardous chemicals are used.
  • Encourage employees to report symptoms that may be related to occupational exposure. If employees develop a rash after cleaning a spill or if they notice that they have trouble breathing at work but never at home or on the weekends, you want to know, says Boiano. Employee health and safety professionals can request a health hazard evaluation from NIOSH if they have specific concerns.
  • Follow the strictest recommended measures. If you don't know much about the hazards of a substitute, maintain the same protections that were in place for the original chemical, advises Toraason. For example, with OPA, "you should follow the practices that are put forward for glutaraldehyde and expect that it's comparable," he says. OSHA has not updated its permissible exposure limits (PELs) on most chemicals in decades, so you should also look at the NIOSH recommended exposure limits (RELs) and the voluntary threshold limit values for chemical substances (TLVs) of the American Conference of Governmental Industrial Hygienists. The European Union also has adopted stricter standards for workplace chemicals.
  • When possible, use an enclosed system. Enclosed systems for instrument reprocessing can minimize or even eliminate worker exposures, Stewart says.

(Editor's note: Information about safe use of glutaraldehyde is available from the 2006 OSHA document, "Best Practices for the Safe Use of Glutaraldehyde in HealthCare" at


1. Rideout K, Teschke K, Dimich-Ward H, et al. Considering risks to healthcare workers from glutaraldehyde alternatives in high-level disinfection. J Hosp Infect 2005; 59(1):4-11.

2. Sokol WN. Nine episodes of anaphylaxis following cystoscopy caused by Cidex OPA (ortho-phthalaldehyde) high-level disinfectant in 4 patients after cystoscopy. J Allergy Clin Immunol 2004; 114:392-397.

3. Fujita H, Ogawa M, Endo Y. A case of occupational bronchial asthma and contact dermatitis caused by ortho-phthalaldehyde exposure in a medical worker. J Occ Health 2006; 48:413-416.