Friday, July 6, 2012

Exposure Badges Do Not Provide Adequate Protection Against Toxic Gases

Toxic gases are found in many workplaces across many industries ranging from carbon monoxide in coal mines, hydrogen sulfide in waste water treatment and chlorine in paper mills. Typically, the workplace is designed to minimize worker exposure to these gases through work practices, process design, PPE & engineering controls etc. However, it is widely recognized that despite the best efforts of the design engineers, exposures to toxic gases can still occur and so most facilities using toxic gases employ fixed and/or portable instruments that continuously monitor the atmosphere and provide a warning to people working there in the event of a leak.

Employers provide continuous monitors because in part because they want to protect their workers and in part because they are required to provide a safe work environment. The Occupation Health and Safety Act of 1970 requires an employer to "furnish to each of his employees employment and a place of employment which are free from recognized hazards that are causing or are likely to cause death or serious physical harm to his employees". This statute provides a general legal duty, and OSHA's standards, which provide more specific legal requirements, such as maximum permissible exposure limits (PELs) for toxic gases. However, OSHA recognizes that each workplace is different and so OSHA leaves determining the best means to achieve these levels to the employer.

Prior to the development of continuous monitors, several chemical methods were developed for determining workplace exposures of toxic gases. Three common methods are:

1) Drawing a known volume of air through an impinger (bubbler) containing a reagent that reacts with the target gas, and the resulting product is then analyzed by laboratory.

(2) Gas exposure badges, in which the target gas reacts with a reagent impregnated on the surface of the badge and the product is again analyzed by a laboratory and

(3) Gas detection tubes in which the target reacts reacts with a reagent on a solid support giving a color change such that the extent of the color change along a graduated scale provides an indication of the gas concentration.

For routine monitoring, these methods have largely been replaced by continuous monitors. Impingers are still used today since many standard test methods call for them, and impingers and badges have some value for those 'exotic gases' for which continuous monitors are not available. The primary drawback of impingers and badges is that they do not provide any warning of what the worker is currently being exposed to, but only report what he or she has already been exposed to. For someone inhaling a toxic gas, now is important, two weeks time, or however long it takes for the lab reports to come back is not adequate. If a person protected by a continuous monitor is exposed to a high concentration of the toxic gas or vapor, a continuous monitor will alarm before the gas concentration reaches dangerous levels and so prevent that person from being exposed. Prevention is always better than an apology!

For this reason, one almost never sees exposure badges being used in general industry. They don't use exposure badges in water treatment plants, or chemical plants or other industries for gases for which continuous monitors are available. There is however one exception, the health care industry. The health care industry uses many toxic chemicals such as drugs for angioplasty, anesthetic gases and sterilization/high level disinfection. The high level disinfectants in particular included gases and vapors such as ethylene oxide (OSHA PEL 1 ppm, NIOSH IDLH 800 ppm) and hydrogen peroxide (OSHA PEL 1 ppm, NIOSH IDLH 75 ppm) are well known to be toxic (otherwise they would not work as disinfectants and sterilants).

The argument has been made that these compounds are normally completely contained within the sterilizers, devices designed to retain these gases/vapors and so leaks are unlikely; but it is unclear how this situation is different from a cold food storage facility using ammonia based refrigeration (OSHA PEL = 50 ppm, NIOSH IDLH = 300 ppm). In both cases, the equipment is designed to keep the the gas inside, but the sterilizer door must be opened on a regular basis to load and unload the items being sterilized. I have never seen a food storage facility or similar establishment using ammonia exposure badges to protect its employees, but it is not unusual to find hospitals that monitor their employees exposure to ethylene oxide or hydrogen peroxide with exposure badges. Continuous monitors are commercially available for ethylene oxide, hydrogen peroxide, ozone, peracetic acid etc, in many cases from several suppliers. The question therefore is why do many hospitals insist on using badges to monitor worker exposure instead of continuous gas monitors.

The National Occupation Research Agenda's (NORA's) Report on workplace safety in healthcare offers an answer: "a key barrier to addressing them [chemical hazards] is the misconception that HCSA [Heathcare sector] work is safer than other work involving exposure to chemical and physical hazards." However a recent Bureau of Labor Statistics report however refutes this assumption.

The same NORA report later comments that "For instance, several authors have pointed out that for many healthcare personnel (HCPs), patient-care issues (i.e., patient health, well-being, and safety) take precedence over personal safety [DeJoy et al. 1995]. There is also a concern that, at least in some settings, a culture and climate of risk acceptance may be the norm; some workers may come to expect that the risk of exposure or injury is simply part of the job."

We often see two versions of this story. The first is an unwillingness to accept the risks posed by the use of the disinfectant and sterilant chemicals in healthcare. This version is easier to understand. The overall risk is a function of the hazard presented by exposure (these are sterilant and disinfectant chemicals after all) and the probability of exposure. If the employer believes, after reasonable investigation, that the risk of exposure is negligible, then the employer can at least argue for not monitoring.

If however, the employer acknowledges that there is risk of exposure, that equipment and engineering controls can sometimes fail and that therefore some kind of monitoring of these gases and vapors is needed then why use an exposure badge, a technology that become obsolete in the 1980s? If an organization uses hazardous chemicals that present a significant risk of exposure, that risk is recognized, and continuous monitors are readily available, then is resorting to badges really meeting the expected standard of care for workplace safety for those employees using these chemicals?

Legal issues aside, the main question for managers who need to decide what type of protection from toxic gases is whether to use continuous monitors, equipment that is widely accepted across many industries to provide good protection for their people or to use exposure badges that have since fallen from main stream use because they don't provide the level of protection needed to keep their workforce safe.

It is dangerous and unfair to paint an industry with too broad a brush and many hospitals have excellent safety records and ensure that their staff are well trained and have modern safety equipment. These facilities should be applauded for setting the standard in healthcare that others would do well to follow.


  1. Great thoughts you got there, believe I may possibly try just some of it throughout my daily life...

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  2. These toxic gases should be handled properly because this is so dangerous to the health of everyone. Building/establishments should have proper ventilation to prevent more hazardous illnesses.