Chemical exposures and chemical hazards are often discussed in isolation—workers are exposed to lead or to methylene chloride or to hydrogen sulfide. But in the real world, workers are often exposed to multiple chemicals, and those combined exposures can pose hazards that were not anticipated based on the properties of the individual chemicals.
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The National Institute for Occupational Safety and Health (NIOSH) recently published a health hazard evaluation on a one-step disinfectant cleaner that is used in more than 500 hospitals. The disinfectant combines three different chemicals. According to its safety data sheet (SDS) and the package directions, users need not wear any personal protective equipment when using the disinfectant if it is diluted with water prior to use.
Here’s what NIOSH found and how it might apply in your workplace.
Numbers Don’t Tell the Full Story
In January 2015, NIOSH was asked to evaluate exposures to a new surface cleaning product being used at a hospital in Pennsylvania. The product is an Environmental Protection Agency-registered nonbleach sporicide (kills spores), virucide (destroys viruses), and deodorizer, advertised as a one-step disinfectant cleaner. It contains three different active ingredients: hydrogen peroxide, peroxyacetic acid, and acetic acid.
Air sampling at the facility revealed that airborne concentrations of hydrogen peroxide and acetic acid were well below the Occupational Safety and Health Administration permissible exposure limits (PELs) of 1000 parts per billion (ppb) and 10,000 ppb, respectively. Concentrations of hydrogen peroxide ranged from 6 ppb to 511 ppb, and concentrations of acetic acid were measured between 7 ppb and 530 ppb during use. There is no PEL for peroxyacetic acid, but concentrations of that chemical were measured between 1 ppb and 48 ppb. In short, based on air sampling during use, the concentrations of each component chemical in air were well below established protective limits.
Despite this, hospital staff who used the cleaner reported symptoms that included burning eyes, nose, and throat; cough; headache; increased asthma symptoms; and skin burns. Clearly, the numbers weren’t telling the full story.
Lessons in Worker Protection
Industrial hygienists have long known that when chemicals are combined, their effects can be different from when those chemicals are encountered in isolation. The combined effect of chemical exposures can be difficult to predict. Sometimes, two chemicals can have an antagonistic effect, inhibiting each other’s actions so that the combined effect is less than would be expected with either chemical alone. Sometimes, the effect is either additive, meaning the effect of the chemicals together is equivalent to the effects of each individual chemical added up, or synergistic, meaning the effect of the chemicals together is greater than the effects that would be expected from the sums of the effects of any individual chemical.
No amount of sampling and chemical exposure number-crunching will give you all of those answers. Instead, when workers are exposed to multiple chemicals, employers must pay attention to what workers are saying about their symptoms. NIOSH recommends that employers:
- Establish a reporting system. This way, workers can make management aware of their symptoms. The reporting system should offer an option for reporting anonymously.
- Take steps to control exposures. Even if exposure sampling doesn’t reveal a measurable problem, the complexity of the interactions of multiple chemicals means that symptom reports should not be discounted. If workers are reporting symptoms, employers should take steps to reduce exposures, including engineering controls (for example, ventilation) and administrative controls (such as job rotation or substitution of less hazardous chemicals wherever practical).
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