1. OELs vs. DNELS – Why Are They (Not) the Same?
Tracy A. Kimmel, Ph.D., DABT
SafeBridge Consultants, Inc.
AIHA Webinar
15 June 2011

2. OEL Methodology OEL = Reference level (UF1,2,3 x SF x MF x A x V)
UF1,2,3 = composite uncertainty factors
SF = safety factor (severity and confidence)
MF = modifying factor (bioaccum., sens., etc.)
A = Absorption (bioavailability) correction factor
V = Volume of air inhaled in 8-hr shift (10 m3)

3. DNEL Derivation
DNEL (Worker-Inhalation-Long-Term) = x mg/m3

4. What’s The Concern? Over 150,000 substances exist in commerce
Of these, only about 1,500 substances (~1%) have OELs anywhere around the world
Every substance in commerce in the EU will have a DNEL
“Safe” level required for risk management

5. OEL Development Timeframe
Prioritization of substances needing OELs
Diversity of committee membership
Expertise & Experience required
Availability of data
Perception of committee setting OELs
Resources: time, data, and finance
“Harmonization” of OELs

6. DNELs and Health-Based OELs
Both can generally be seen as quantitative estimates of “safe” levels of exposure to chemicals
Health-based OELs  for workers only (inhalation exposure)
DNELs  for workers and consumers (general population) by inhalation, dermal and oral routes of exposure

7. DNELs and Health-Based OELs (cont’d)
Processes for derivation show some similarities but also significant differences
Starting dose descriptor; SF/AF differences; peer-review
Have different intended purposes

8. How They Differ OELs (Health-Based) DNELs (Not Health-Based)
Levels of acceptable risk for workers based on NOAELs and LOAELs with SF (AF)
Developed by EHS professionals, governmental agencies, from published data
Utilize professional judgment and ‘weight of evidence’ with peer review by experts who draw comparative analogy between animal and human toxicology parameters
Target 10 – 50% of the OEL for compliance
Threshold-based non-cancer endpoints considered to be “No Effect Levels” for humans based on NOELs and AFs
Developed by manufacturers and importers
Worker DNELs are calculated from Population DNELs
Prescriptive & conservative – not based on judgment
May be derived from proprietary data

9. How They Differ (Cont’d)
OELs (Health-Based)
DNELs (Not Health-Based)
Single value, calculated from Point of Departure = effect considered to be most serious/relevant
Multiple calculations for each endpoint and each relevant exposure route; the lowest value is selected as the Leading Effect and used as the final DNEL

10. More Confusion
“When applying the REACH guidance (ECHA, 2008),…the summarizing tables and figures only present default values for different AFs. Moreover, these defaults are often the lowest values of a selected range, whereas higher AFs are described as needed for exceptional cases.”
Schenk and Johanson
Toxicol Sci 121(2):408-16, 2011

11. More Confusion (Cont’d)
“For instance, the default AF for issues related to the reliability of the dose-response relationship, including extrapolation from LOAEL to NOAEL, is 1…Meanwhile, the body test reads ‘it is suggested to use an AF between 3 (as minimum/majority of cases) and 10 (as maximum exceptional cases) Thus one assessor, reading only the table, might apply an AF of 1, whereas another assessor, reading also the text, might apply an AF of 3, or perhaps even 10…”
Schenk and Johanson
Toxicol Sci 121(2):408-16, 2011

12. DNEL = OEL (Sometimes)
Registrants can use health-based IOELVs as DNELs, under certain conditions
OELs established by regulatory agency cannot be used as DNELs
DNEL = OEL? (sort of)

13. OELs, DNELs: eSDS Sect. 8.1
All DNELs (including DMELs) calculated for the relevant human exposure pathways, as well as applicable Member State1, health-based OELs are required to appear on REACH-compliant eSDSs2
May have multiple DNELs listed (i.e. for inhalation and dermal exposure for long and acute durations of exposure for both workers and consumers ….)
Potential source of “confusion” for the eSDS user
1Where the eSDS is to be provided
2Commission Regulation (EU) No. 453/2010 amending Regulation
(EC) No. 1907/2006 (REACH) – effective 12/1/2010

14. EU CAD
The…regulation is clear that REACH “…should apply without prejudice to Community workplace and environment legislation.”
In particular, the text of the REACH regulation goes on to say that the “Regulation shall apply without prejudice to a number of Directives including: “… Directive 98/24/EC….” [the EU Chemical Agents Directive; CAD]
CAD obligates employers to protect the heath and safety of workers from risks of hazardous chemicals
CAD defines “OEL”

15. EU CAD (Cont’d)
Obligation under the EU CAD to monitor for compliance with the National (Member State) OEL
DO NOT monitor to the DNEL
No regulatory (or any other) obligation whatsoever to do this
Not a ‘default” limit for exposure control
Not what DN(M)ELs are intended to be used for DNELs do not displace OELs

16. Margins of Safety
Comparison between margins of safety used by SCOEL (IOELVs) and those used to derive worker-DNELs by strict adherence to REACH guidance
Composite safety factors used by SCOEL are generally lower than those used by REACH for worker-DNEL development
Worker-DNELs would generally be lower than health-based OELs
Worker-DNELs ≠ OELs
Schenk and Johanson
Toxicol Sci 121(2):408-16, 2011

17. Margins of Safety (Cont’d)
Schenk and Johanson
Toxicol Sci 121(2):408-16, 2011

18. OEL vs. DNEL: N-Hexane SCOEL REACH Point of Departure
Peripheral neuropathy by inhalation (LOAEL)
Dose
70 ppm
Uncertainty Factor
3.5 (AF of 2 + rounding convention of 1.75) 15
IOELV/DNEL
20 ppm
~5 ppm

19. OEL vs. DNEL: DMF SCOEL REACH Point of Departure
Liver effects in mice by inhalation (LOAEL)
Dose
7.8 ppm/6 hr
3.9 ppm/8 hr (adjusted value)
Uncertainty Factor 1
12.5
IOELV/DNEL
5 ppm
0.32 ppm

20. OELs vs. DNELs EU Working Party on Chemicals (2010):
“… unanimously agreed that there was no simple relationship between DNELs and OELs, and that the real issue for employers was how to respond to additional duties imposed by REACH as well as the continuing requirements under occupational health and safety legislation.”

21. OEL vs. DNELs (Cont’d)
Both OELs and DNELs are useful in establishing “adequate” control of exposure(s)
Especially for inhalation exposures in the workplace
DNELs also set for dermal exposures  lead to controls

22. Sharing The Sandbox Co-existence (EU Working Party, 2010):
“Where both a national OEL and a DNEL … have been derived for a substance, and the risk management measures in the safety data sheet are significantly more restrictive, employers are responsible for the protection of their employees, and should seek to resolve the situation with their suppliers and, as appropriate, with the relevant authorities.”
Need to be familiar with the purpose of each as part of worker protection

23. Sharing The Sandbox (Cont’d)
DNELs and OELs will need to (and do) co-exist…
Already co-exist on REACH eSDSs (Section 8.1)
Co-exist where IOELVs are used as DNELs
1See Schenk and Johanson, in Toxicological Sciences (advanced online publication: 3/9/2011)

24. Sharing The Sandbox (Cont’d)
…However, “differences” between them will undoubtedly create confusion in terms of legal compliance, risk management and risk communication1
Will be important for EU and National authorities to “…clearly communicate the relation between OELs and worker-DNELs and give guidance on how to handle potential conflicts between different OEL values.”1
1See Schenk and Johanson, inxicological Sciences (advanced online publication: 3/9/2011)

25. Challenging the OEL
Although DNELs are not required on MSDSs in USA, they will be available on the internet SDSs
Worker DNELs could become ‘de facto’ OELs for some companies and possibly some countries
Questions the validity of our historic TLVs, MAKs, WEELs, and other health-based guideline values
Creates opportunity for litigation against employers and the OEL-setting bodies (= $$$$$$$$$$$)

26. Concerns About DNELs and Health-Based OELs
Most chemicals do not have PELs, TLVs, or a unified, codified exposure limit
Can regulators use DNELs to demonstrate non-compliance?
Will EU member-states abandon their current OEL processes and default to the DNELs?
Will the EU grab hold of the DNELs and turn them into IOELVs?
Will manufacturers derive overly conservative DNELs to shield themselves from liability?

27. Concerns About DNELs and Health-Based OELs (Cont’d)
Will manufacturers “adjust” their DNELs to achieve a favorable RCR?
Will we see multiple DNELs for the same substance when manufacturers can’t agree?
Will manufacturers derive overly conservative DNELs to shield themselves from liability?
Will manufacturers “adjust” their DNELs to achieve a favorable Risk Characterization Ratio?

28. Resolution? Adjust DNELs for use as OELs
That risk typically not quantified, led to conservatism in IH practice
Along with statistical conservatism if exposures > 50% OEL
Also embodied in the < 1/2 to 1/10 OEL concept to prove compliance

29. Possible Path Forward
One obstacle for OEL development was lack of data
REACH will greatly expand the dataset on substances and there will probably be subsequent testing and development of more data
May become an opportunity for advancement of OELs