Exposure limits for airborne chemicals are undergoing change. New limits such as the DNEL are being developed and current limits such as the TLV® face an uncertain future. Now is the time to reexamine how your organization will apply exposure limits for airborne chemicals.

Occupational exposure limits

Occupational exposure limits (OELs) such as the regulatory-based OSHA PEL or health-based ACGIH® TLV® are established as a risk management tool to help EHS pros determine if chemical exposure to workers is acceptable. The future of these OELs, however, is bleak.

Together, the number of PELs, TLVs®, AIHA WEELs, and NIOSH RELs account for only about one percent of the 80,000 chemicals in U.S. commerce. Most PELs are based upon 1968 TLVs®. OSHA developed fewer than 20 new PELs in 40 years – a pattern unlikely to change. TLV® development is no longer sustainable under ACGIH®’s current budget. It costs ACGIH® about $50,000 to develop or revise a single TLV®. Primarily because of legal costs to defend the TLV® process, ACGIH® experienced operating losses of about $600,000 through 2006-2008.1 Adding salt to wounds, as currently written, OSHA’s proposed rule to align hazard communication with GHS (Globally Harmonized System of Classification and Labeling of Chemicals) will delete the TLV® reference from safety data sheets (SDS).

What is a DNEL?

Most EHS pros now realize that the European Union's (EU) REACH (Registration, Evaluation, Authorization, and Restriction of Chemicals) legislation impacts chemical management in the U.S. REACH requires manufacturers and importers of chemicals into Europe to determine and communicate a “Derived No Effect Level” (DNEL). A DNEL is defined as “the level of exposure above which humans should not be exposed.”

There may be several DNELs, depending upon mode of effect, for a single chemical. The way DNELs are determined means they will usually be lower, sometimes significantly lower, than an OEL. Also, be aware that REACH requires other exposure limits besides the DNEL that this article does not discuss.

A DNEL is required for all regulated chemicals in production volumes over 10 tons per year. As REACH evolves, the DNEL will become the most prominent exposure level for chemicals. DNELs will begin to appear in public lists and SDS in 2010. EHS pros in the U.S. will encounter DNELs as GHS evolves.

Additional information on DNEL (including how it is derived and used) can be found at http://guidance. echa.europa.eu/docs/guidance_document/information_ requirements_r8_en.pdf?vers=20_08_08.

How will you apply the DNEL?

Scenario A:Assume workers at your organization are exposed to the hypothetical chemical Cyclohygiene at 50 ppm with a DNEL at 5 ppm. Cyclohygiene has no PEL, TLV or other OEL. Is worker health protected in this example? Recall that the definition of a DNEL is “the level of exposure above which humans should not be exposed.” If all you go on is this definition, then worker health may be at risk and urgent risk treatment would likely include various controls to reduce employee exposure to Cyclohygiene to less than 5 ppm.

Scenario B:Assume workers at your organization are exposed to Cyclohexane at 50 ppm. Cyclohexane has a PEL at 300 ppm (based upon 1968 TLV® list) and a current TLV® (updated in 1991) at 100 ppm. Is worker health protected in this example? Now add a twist, for purposes of this article only, assume the DNEL for Cyclohexane is established at 5 ppm. Is worker health protected in this example?

Although health risk may be similar in scenarios A and B, there may be a higher comfort level for management, with less urgency to apply risk treatment, in scenario B. In scenario B, management has some relief by knowing they comply with OSHA and are below the current TLV®. But how should the conflict with a much lower DNEL resolved?

Prepare yourself

DNELs are on their way and your organization may face the concepts in scenarios A and B at anytime.

What should you do?

First, gain further understanding of EU REACH. At a minimum, reviewing the information on DNELs at the link mentioned is important. And begin to have a working knowledge of GHS now. Regardless of what OSHA does or doesn’t do with its proposed rule to align hazard communication with GHS, just like the DNEL, GHS is coming to your worksite.

Risk management

Ignoring a DNEL is not wise. Applying the DNEL in all cases may not be wise either. Now may be a good time to apply the concepts of ISO 31000:2009 Risk Management – Principles and Guidelines; and, its companion document, ISO 31010:2009 Risk Management – Risk Assessment Techniques. ISO 31000 may be applied to a singular risk, such as how to apply a DNEL, or can be expanded to cover a broader risk such as how an organization should ensure worker health and safety.

ISO 31000 will help your organization to consider:
  • Key drivers and trends;
  • Relationships with, and perceptions and values of external and internal stakeholders;
  • Form and extent of contractual relationships; and,
  • Communication and consultation with stakeholders.
Key drivers and trends must be considered regarding the DNEL. If your organization does not appreciate why DNELs were created, it won’t fully understand how chemical exposure risk should be managed in a global society and it may not be prepared to argue why OELs should be supported or abandoned.

Chemical risk

Chemical management in the U.S. is now being heavily influenced by EU REACH. Be alert to proposed legislation to modernize the U.S. Toxic Substance Control Act (TSCA). When you hear about the bill, check to see how TSCA will address issues such as the DNEL. I suspect we may also hear some chatter from OSHA how a PEL may relate to the DNEL.


1 FW: 12/10/09 email (Sharon Sperber) The State of ACGIH - Jimmy L. Perkins, PhD, CIH ACGIH Chair.