Less than one percent of all chemicals commercially used in the United States have an established occupational exposure limit such as a permissible exposure limit (PEL), threshold limit value (TLV), or recommend exposure limit (REL). What should we do when we discover chemicals in the workplace that lack such limits?

Carmen Wegener, an environmental health and safety colleague, faced this situation when she found 2-propyxyethanol in some screen inks used in her facility’s operations. She consulted with the lab where she normally sends industrial hygiene samples. “In some cases, they can measure the substance, but without a standard it will be up to you to interpret the result,” she says. “If they cannot measure, one option is to measure what does have a PEL (in this case, 2-butoxyethanol in the same ink) and assume that the non-PEL substance is present in the same proportion as it is in the source mixture (in this case, the ink).”

Carmen also consulted good current toxicology resources for possible toxicity trends of the non-PEL substance as compared to one in the same chemical family that does have a PEL.

Finally, she consulted the manufacturers of both the ink and the 2-butoxyethanol in the ink to see if they had an internal exposure standard. It turns out they did have such a standard (20 parts per million time-weighted average), and levels at Carmen’s facility were below it.

The “precautionary principle”

Carmen used the “precautionary principle” in this case: When an activity raises threats of harm to human health or the environment, precautionary measures should be taken, even if some cause-and-effect relationships are not fully established scientifically.

The U.S. signed and ratified the United Nations 1992 Rio Declaration, which commits the U.S. to applying precautionary principles. Christine Todd Whitman, the Bush administration’s pick to head the EPA, offered support for it during a speech at the National Academy of Sciences last year. You can learn more about the precautionary principle at http://www.biotech-info.net/precautionary.html.

Counter to this principle, chemicals in the U.S. are generally treated as innocent until proven guilty of producing substantial harm. This is one reason why there are embarrassingly few exposure limits for chemicals in the workplace. OSHA only explicitly regulates about 500 chemical substances out of more than 200,000 chemicals in common use. And many of the exposure limits set by OSHA are far out-of-date. In 1989, OSHA tried to update PELs, amending 212 substances to more protective levels and setting PELs for an additional 164 substances. But in June, 1992, the Eleventh Circuit Court of Appeals issued a rule vacating the 1989 OSHA PELs.

More recently, the American Conference of Governmental Industrial Hygienists was served with three separate unrelated lawsuits in December, 2000. Basically, businesses that manufacture and commonly use sodium sesquicarbonate, synthetic vitreous fibers, and vinyl chloride didn’t like ACGIH establishing TLVs for these substances and they sued. Among other things, the ACGIH is concerned that “…the nature of these complaints calls into question the freedom of any party to undertake independent scientific research and publish results.”

Chemical manufacturers will disclose on a case-by-case basis their “in-house” exposure limit for a chemical, if they have established a limit. But there’s almost always a universal disclaimer stating that, “Users should make their own investigations to determine the suitability of the information for their particular purposes.” They’re saying the “number may work for us, but we’re not sure about you.”

Guilty until proven innocent

Faced with a lack of responsible guidance and scientific uncertainty for most chemicals, employers have few options but to apply the precautionary principle for all chemicals that lack established exposure limits within the workplace. This means an employer should strictly control exposure until “safe” limits are established. To do nothing shows disregard for employees or make the erroneous assumption that the chemical is safe at any exposure amount.

When trying to determine guilt or innocence for chemicals, employers may make a big mistake by relying too much on information supplied, or not supplied, in a material safety data sheet from the chemical manufacturer or supplier. Besides being error prone and data weak, almost every MSDS now includes a disclaimer that places the burden of liability of its use back onto the user.

Evaluation methods

Many methods can be followed to evaluate chemicals and determine safe exposure limits. But the success of each method rests heavily on the experience, skills, qualifications and resources of the person(s) using the method. Every method involves some subjectivity. It’s best when your evaluation discovers a qualified third-party that establishes a safe exposure limit for the chemical in question.

For example, I used search tools at http://www.toxlaw.com. to scrutinize 2-propyxyethanol and found that the Netherlands has an occupational exposure limit (OEL) for the chemical of 10 ppm (TWA) with a skin notation. Now, should you follow the U.S. manufacturer’s internal standard for the chemical of 20 ppm or the Netherlands OEL at 10 ppm? (The Netherlands OEL was set after Carmen did her study, and was not available to her.) If you’re applying the full intent of the precautionary principle, you’ll likely choose the Netherlands OEL.

Give us a limit

If chemical manufacturers are critical of the precautionary principle, and if they initiate and back efforts to restrict regulators and organizations such as ACGIH from establishing limits, then they should publish a recommended occupational exposure limit for each chemical they manufacture. Employers then may decide how far below the limit to keep exposures in their own workplaces.

The whole issue seems to be about legal posturing to reduce liability. Why don’t the powers instead focus on reducing potential harm to people and the environment? It’s real simple: just give us an exposure limit for each chemical. We’ll take it from there.