FOR CONSULTANTS ; ETHICS
Industrial Hygienists Benefit from Broad Awareness
of Published Exposure Limits
BY DAVID KUDLINSKI AND TERI COPELAND
As career industrial hygienists (IHs), we are all familiar with the
annual ACGIH® Guide to Occupational Exposure Values and its
Threshold Limit Values (TLVs®), OSHA Permissible Exposure
Limits (PELs), NIOSH Recommended Exposure Limits (RELs),
Deutsche Forschungsgemeinschaft (DFG) Maximum Concentrations Values in the Workplace (MAKs), and AIHA® Workplace
Environmental Exposure Levels (WEELs).
It is certainly necessary for us to master the scope and limitations of these occupational exposure limits (OELs). Nonetheless,
IHs can face situations where knowledge of exposure limits beyond traditional OELs may be beneficial, or even necessary, to
evaluate particular chemical exposure scenarios involving workplaces or other public settings.
Indoor Air Quality
In indoor air quality (IAQ) investigations, it is prudent to refer-
ence the recommendations of the American Society of Heating,
Refrigerating, and Air-Conditioning Engineers, Inc. (ASHRAE®),
the leading standards organization for acceptable IAQ. The
ANSI/ASHRAE Standard 62.1-2010 “Ventilation for Acceptable
Indoor Air Quality” defines acceptable indoor air quality as “air
in which there are no known contaminants at harmful concen-
trations as determined by cognizant authorities and with which
a substantial majority (80 percent or more) of the people ex-
posed do not express dissatisfaction.” Cognizant authority is
defined as “an agency or organization that has the expertise
and jurisdiction to establish and regulate concentration limits
for airborne contaminants; or an agency or organization that is
recognized as authoritative and has the scope and expertise to
establish guidelines, limit values, or concentration limits for
The ANSI/ASHRAE ventilation standards establish minimum
acceptable ventilation rates for buildings, but do not provide
chemical-specific limits. Nevertheless, Appendix B of ANSI/
ASHRAE Standard 62.1-2010 presents an informative summary
of selected air quality guidelines. These guidelines are not re-
quired for conformance to the standard; however, air quality
guidelines beyond traditional OELs are helpful when evaluating
the environmental health, comfort, and satisfaction of building
Appendix B of the standard references numerous air quality
guidelines published by authorities including EPA’s National
Ambient Air Quality Standards (NAAQS); Agency for Toxic Substances and Disease Registry’s (ATSDR) Minimal Risk Levels
(MRLs); and California Environmental Protection Agency, Office
of Environmental Health Hazard Assessment’s (OEHHA) Reference Exposure Levels (RELs); as well as those from the World
Health Organization (WHO) for Europe and Health Canada.
All of these guidelines are applicable for the general public
and involve primarily long-term exposures, although short-term
exposure guidelines have been developed for many chemicals as
well. When referencing these public health guidelines, the user
should recognize that many IAQ exposure limits are based on
non-cancer health end points and do not address cancer risk.
Therefore, careful review of the guideline’s intent is warranted.
There are EPA Regional Screening Levels (RSLs) for residential
and industrial air based on the cancer end point for known and
potential carcinogens. EPA also provides RSLs for residential
soil, industrial soil, and tap water. Many states have developed
health-based screening concentrations similar to RSLs.
If very-low-concentration IAQ standards are desired, it is important to account for the effects of background interferences,
such as ambient air pollution, off-gassing from building materials and furniture, and use of employees’ personal items in the
workspace in preparation for air sampling.
Emergency Response (Airborne Contaminants)
Many industrial facilities store or manage hazardous chemicals.
IHs at these facilities should conduct an assessment of what the
exposure might be to employees and/or the public in the event
that a tank leak, pipe burst, process overflow, etc. leads to a
Furthermore, emergency responders need to know what measures will be needed to mitigate the chemical release and direct
evacuation. For example, which level of OSHA personal protective equipment (PPE) would the emergency require: Level A, for