A New Occupational Exposure Limit for OPA?

The American Conference of Governmental Industrial Hygienists (ACGIH), well known for its threshold limit values (TLVs) for a wide range of chemicals, just released its list of chemicals under study. The ACGIH was one of the first organizations to issue occupational exposure limits for chemicals in the workplace and its TLVs underlie the legislated occupational exposure limits in many countries, including OSHA’s permissible exposure limits in the US.

The 69 chemicals on the list are under study by the ACGIH to determine if a TLV should be issued and one of those chemicals is o-phthalaldehyde, better known as OPA. This chemical is widely used as a high level disinfectant (HLD) for disinfection of endoscopes and other devices.  Glutaraldehyde, a related chemical (both dialdehydes) used to be the standard chemical for high level disinfection, but there were numerous reports of irritation and sensitization and occupational asthma. In the UK, glutaraldehyde has been banned on the basis of health effects and efficacy, and the predominant HLD for endoscopes is peracetic acid (PAA). In the US, glutaraldehyde is still used, but less than PAA and OPA.

While there is no OSHA PEL for PAA or glutaraldehyde, the ACGIH has TLVs for both of them, a ceiling limit of 0.2 ppm for glutaraldehyde and a short term exposure limit of 0.4 ppm for PAA. OPA has in some quarters been touted as the safe alternative to glutaraldehyde since there is no occupational exposure limit; though in practice it has also been found to be a skin irritant, sensitizer and cause occupational asthma. The fact is that any chemical used as a sterilant or HLD is obviously biologically active and so is potentially hazardous to anyone exposed to high concentrations. Employers have a duty to prevent their people being over exposed to chemicals in the workplace, but employer and employees need to know what constitutes a high concentration; and occupational exposure levels such as the ACGIH TLVs answer that question.

HLD chemicals are essential for infection control in healthcare, but it is important to ensure that they are used safely. If they are not used safely, then workers will be over exposed, suffer symptoms and injury and the chemicals may even be withdrawn. Having a TLV is an important step in promoting the safe use of OPA and we support the ACGIH in their efforts.