Public Exposure Guidelines

Public exposure guidelines are intended to predict how members of the general public would be affected (that is, the severity of the hazard) if they are exposed to a particular hazardous chemical in an emergency response situation.

The most common public exposure guidelines are:

  • AEGLs (Acute Exposure Guideline Levels)
  • ERPGs (Emergency Response Planning Guidelines)
  • TEELs (Temporary Emergency Exposure Limits)

General Definition

Each of these guidelines has three tiers of exposure values (e.g., AEGL-1, AEGL-2, and AEGL-3) for each covered chemical. There are some key differences between the exposure guidelines; however, at a very general level, the tiers are similar:

  • The first tier (e.g., ERPG-1) is a temporary, non-disabling effects threshold.
  • The second tier is a disabling (escape impairment) threshold.
  • The third tier is a life-threatening effects threshold.

Competing Guidelines

A particular chemical may have values in any—or all—of these systems. As a result, you may want to select your values based on a hierarchy of available public exposure guidelines (for instance, using AEGLsAcute Exposure Guideline Levels are levels of concern representing the adverse health effects of a hazardous substance on members of the general public. AEGL values were developed by the National Advisory Committee on AEGLs. As of November 2011, ongoing AEGL development will be done by a National Academy of Sciences subcommittee (www.epa.gov/aegl). preferentially over TEELsTemporary Emergency Exposure Limits are levels of concern representing the adverse health effects of a hazardous substance on members of the general public. TEELs are defined by the U.S. Department of Energy for use when ERPGs or AEGLs aren't available. if both systems define values for a chemical). The PACs dataset combines all three public exposure guidelines and implements a hierarchy-based system for you.

If public exposure guidelines aren't available for a chemicalIf public exposure guidelines aren't available for a chemical

Most common chemicals will be defined under one or more of the public exposure guidelines; however, you may occasionally be faced with a chemical for which no public guideline exists. No clear rules describe what you should do if you're in this situation and your goal is to assess the hazard to the general public posed by a release of that chemical.

One option is to use a workplace exposure limit. These are usually defined for healthy adult workers, and typically incorporate safety factors to ensure that workers won't be overexposed to hazardous chemicals in the workplace.

However, if you're considering this option, be aware that:

  • These limits were designed to protect workers, not for use in assessing hazards to people exposed during an accidental release.
  • Because age, health, and exertion influence how susceptible people will be to a pollutant, it's possible that some workplace limits may underestimate risk to the sensitive portions of the general population (such as those who are old, young, or sick).

Common workplace exposure limits include:

  • IDLHs (Immediately Dangerous to Life and Health limits)
  • TLVs (Threshold Limit Values)
  • RELs (Recommended Exposure Limits)
  • PELs (Permissible Exposure Limits)