The last page of any safety data sheet (SDS) always contains legalese that, in short, states that users of the product may not rely on the information in the SDS alone to make decisions. If there’s no occupational exposure limit (OEL) listed for a chemical ingredient or byproduct in a SDS, you can conduct an online search for the chemical by CAS number and include the qualifier DNEL — derived no effect levels. CAS is required on an SDS, DNEL is not.

The CAS RegistrySM contains more than 139 million unique organic and inorganic chemicals. OSHA contends that there are about 880,000 of these CAS chemicals that are considered hazardous and used at U.S. workplaces1.

DNELs are the “level of exposure above which humans should not be exposed.” There were more than 5,000 DNELs at the end of 2017 and growth continues by hundreds each year2. By comparison, there’s only about 600 total PELs, TLVs®, and RELs (NIOSH’s Recommended Exposure Limit) – and only a few (mostly TLVs®) of these are developed/revised annually. This is one reason why searches for DNELs are a necessity today.

OEL use in the U.S.

Consideration of DNELs has grown since GHS adoption by OSHA in 2012. For example, the preamble to OSHA’s 2017 beryllium standard considered the DNEL at 0.14 ug/m3 before setting the agency’s PEL at 0.2 ug/m3. NIOSH’s February 2018 Health Hazard Evaluation “Evaluation of Metalworking Fluid Exposure, Dermatitis, Respiratory Symptoms, and Psychosocial Factors in an Engine Machining Plant” addressed dicyclohexylamine’s DNEL at 0.353 mg/m3 when there was no other OEL to apply3.

Risk management decisions are necessary to apply the DNEL or any other OEL. Consider, for example, data in Table I. Which OELs should your organization apply?

OSHA may apply an OEL lower than the PEL under the “general duty clause” in cases where medical evidence demonstrates that PEL is not protective. I always apply the DNEL at 20 ppm for pregnant workers, to prevent “damage to the unborn child” (OSHA term). But that’s me; other OHS pros may choose a different risk management decision. In every case, however, application of any OEL, and particularly DNELs, should be carefully considered.

Chemical Exposure graph


User qualifications

OELs alone may not be protective. Psychosocial and other factors must be considered, such as pregnancy, worker use of medications and concurrent illness/disease. ACGIH® advises that only people trained in industrial hygiene (IH) may apply a TLV®. See “Special Important Note Regarding ACGIH TLV” at OSHA’s Annotated PELs website4.

What IH qualifications must a person have to properly apply a TLV® or other OEL? What’s the risk if they don’t have good qualifications? The CIH® credential may be acceptable in most, but not all, cases. Again, an employer’s risk management practices should define minimum qualifications for personnel to interpret OELs and other factors that impact worker health from chemical exposures.

Best practices

The following eight key concepts should be part of your chemical risk management practices:

  1. ISO Standards. ISO 31000:2018 Risk Management and ISO 45001:2018 OHSMS, used together, are the best means to develop risk management practices for occupational chemical exposures. Particularly, “context of the organization” clauses will help establish risk decisions.
  2. Hierarchy of controls. Eliminate or substitute (replace) chemicals, such as carcinogens, mutagens and toxic to reproduction that may not conform to the organization’s risk tolerance. All chemical exposures should be contained by an engineering control such as enclosure, exhaust or dilution ventilation. PPE (such as a respirator) should be considered last. 
  3. OELs. Always compare worker chemical exposure to an OEL. Create OELs as necessary. Grouping multiple chemical exposures into a single OEL is acceptable in some cases, such as a metalworking fluid (MWF) REL at 0.5 mg/m3 total mist. A CIH® may help develop an in-house OEL for total hydrocarbons, for example. Be aware that there is no such thing as zero exposure to workplace chemicals. A physician should never specify an occupational patient to have “no” exposure to a chemical. Airborne chemicals may be measured in extremely tiny amounts.
  4. IH qualification. IH is an art as much, or perhaps more, than it is a science. Current IH art is best described in Ilise Feitshans 2018 book, “Global Health Impacts of Nanotechnology Law: A Tool for Stakeholder Engagement”5. Ilise, international legal scholar (and ASSE member), uses plain-language to explain complex topics. IH science is best achieved by structured and formal training, preferably at an accredited university. The CIH® credential represents the highest achievement of IH competency.
  5. Exposure assessment. Early OSHA health standards such as asbestos and lead required “exposure monitoring” to determine PEL compliance. Recent health standards (hexavalent chrome, silica and beryllium) establish there’s more than just pump hanging to determine compliance. New health standards precede monitoring with “exposure assessment” that encourages use of “objective data” to determine PEL compliance. An initial and periodic exposure assessment that includes use of objective data should be available for every workplace chemical.
  6. Worker involvement. Involve workers as much as practical to help resolve chemical exposure concerns. Communicate IH in plain-language. Don’t underestimate a worker’s understanding of chemical exposure concerns.
  7. Medical monitoring. Include medical monitoring, as necessary, to help determine acceptable chemical exposures. OSHA generally requires medical monitoring above “action limits” (usually one-half of the PEL). Apply similar strategy for OELs. See NIOSH HHE for MWF (ref. 3) as an example of generic medical monitoring.
  8. Health priority.  Injuries receive priority because of their immediacy. Health priority should equal injuries even though Illnesses/diseases from chemical exposures are often long-term events.