Industrial Hygiene

Contaminant Exposure Limits

While traveling this week, I read read through October’s Synergist magazine.  For those of you not familiar with The Synergist, it is a publication produced by the American Industrial Hygiene Association (AIHA).

This month’s edition had two excellent articles regarding exposure limits.  What are exposure limits?  Simply put, these are concentrations of contaminants to which people should not be exposed.  Some exposure limits are enforceable by law and others are mere recommendations.  Some exposure limits apply to the entire population, and others are for healthy workers in an occupational setting.  No two organizations promulgating exposure limits are the same.  Below are the most commonly quoted exposure limits in the US:

  • Occupational Safety and Health Administration (OSHA) → Permissible Exposure Limits (PELs)
  • American Conference of Governmental Industrial Hygienists (ACGIH®) → Threshold Limit Values (TLVs®)
  • National Institue for Occupational Safety and Health (NIOSH) → Recommended Exposure Limits (RELs)
  • American Industrial Hygiene Association (AIHA®) → Workplace Environmental Exposure Levels (WEELs)

I recommend you read the article in this month’s Synergist, “Beyond OELs: Industrial Hygienists Benefit from Broad Awareness of Published Exposure Limits”.  You will learn about exposure limits beyond the most common ones quoted above, including:

  • Environmental Protection Agency (EPA) → Reference Concentrations (RfCs) in the IRIS database
  • Agency for Toxic Substances and Disease Registry → Minimal Risk Levels (MRLs)
  • California EPA Office of Environmental Health Hazard Assessment (OEHHA) → Reference Exposure Levels (RELs)

The second article in this month’s Synergist related to exposure limits is titled, “Coming Soon: DNELs, How will REACH-mandated exposure limits affect IHs and labs?”  This article describes provisions in the European Union’s new regulation titled “Registration, Evaluation, Authorization and Restriction of Chemicals” (REACH).

The regulation affects large manufacturers and importers of chemicals, requiring them to calculate Derived No-Effect Levels (DNELs).  According to Annex 1 of the regulation, DNELs are the “level of exposure above which humans should not be exposed… In the risk characterisation, the exposure of each human population known to be or likely to be exposed is compared with the appropriate DNEL.  The risk to humans can be considered to be adequately controlled if the exposure levels estimated do not exceed the appropriate DNEL.”

So many of the chemicals in use worldwide have not been adequately studied.  The Synergist article states that this new EU regulation applies pressure on the US to develop its own similar regulation.  I’ll keep you posted with any new developments through my blog.

For free access to both of these interesting articles, follow this link: The Synergist: October 2010.

By Ian Cull

I'm I.A.N. the Indoor Air Nerd. I'm a speaker and consultant on indoor air quality issues. To learn more about me, click "about" at the top of this page.

One reply on “Contaminant Exposure Limits”

Some others I should have mentioned:
1. Deutsche Forschungsgemeinschaft (DFG) Maximum Concentration Values in the Workplace (MAKs)
2. EPA’s National Ambient Air Quality Standards (NAAQS) for criteria pollutants (not to mention Hazardous Air Pollutants)
3. World Health Organization
4. Health Canada
5. California EPA’s Toxic Air Contaminants
6. EPA’s Regional Screening Levels (RSLs)
7. Cancer Unit Risk Estimates (UREs) from multiple organizations
8. OEHHA’s No Significant Risk Level (NSRL)

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