Emergency Response Planning Guidelines – ERPGs
9/6/2021
The American Industrial Hygiene Association (AIHA) is the professional organization for those who are assigned to protect workers within occupational settings; particularly providing measures to ensure the health and wellbeing of those working with chemicals and other hazardous substances. Because emergency situations, such as chemical spills, have become a major concern, the Emergency Response Planning Committee, within the AIHA, developed health guidelines that specifically address one-time exposures to chemical agents, known as Emergency Response Planning Guidelines or ERPGs. ERPGs are air concentrations of chemicals that – through past events – have been identified as being the most likely substances to be involved with accidental spills. They are short term health limits designed to be included in accident prevention and emergency response plans, hazardous materials transportation programs, emergency planning, community emergency response plans, and incident prevention and mitigation.
ERPGs differ from the typical occupational exposure limits for airborne contaminant concentrations, such as OSHA permissible exposure limits (PELs) and ACGIH threshold limit values (TLVs). These values are designed to control inhalation exposures based on full shift (i.e. 8-hour periods) exposures, while ERPGs are focused on exposure concentrations during a single, short-term event. Thus, they estimate the concentrations at which most people will begin to experience health effects if they are exposed to a hazardous airborne chemical for 1 hour. At the same time, sensitive members of the public, such as the elderly, sick, or very young people, aren’t covered by these guidelines as they are more susceptible to experience adverse effects at concentrations well below these ERPG values.
A chemical may have up to three ERPG values; each of which corresponds to a specific tier of health effects. The three ERPG tiers are defined as follows:
- ERPG-3 is the maximum airborne concentration below which nearly all individuals could be exposed for up to 1 hour without experiencing or developing life-threatening health effects.
- ERPG-2 is the maximum airborne concentration below which nearly all individuals could be exposed for up to 1 hour without experiencing or developing irreversible or other serious health effects or symptoms which could impair an individual’s ability to take protective action.
- ERPG-1 is the maximum airborne concentration below which nearly all individuals could be exposed for up to 1 hour without experiencing more than mild, transient adverse health effects or without perceiving a clearly defined objectionable odor.
As an example, the ERPG-1 for chlorine gas – Cl2 – is 20 ppm, while the ERPG-2 ppm is 3 ppm and the ERPG-3 is 1 ppm. Obviously the greater the ERPG number, the more stringent (restrictive) the airborne concentration.
These guidelines were developed through research based on animal toxicology data, human experience, existing exposure guidelines, the rationale behind the selected value, and a list of references.
There are about 150 chemicals that have ERPGs and are published by the AIHA with annual updates, presented in the ERPG/WEEL Handbook (WEEL stands for Workplace Environmental Exposure Levels).
ERPGs estimate how the average person (except for sensitive individuals) would react to a release of a hazardous chemical. Therefore, they can assist local officials to identify areas where a hazard exists based on the concentration of a hazardous gas based on an exceedance value for a specified exposure duration. Thus, in areas with concentrations just above the ERPG-1, most people would experience temporary, non-disabling effects. On the other hand, in areas with concentrations just above the ERPG-2, most people would experience significant—but not life-threatening—health effects. These guidelines are focused on a single 1-hour period. Exposure in the field may be longer or shorter. However, the AIHA strongly advises against trying to extrapolate ERPG values to longer periods of time.
ERPGs shouldn’t be used as guidelines for workers who are routinely exposed to chemicals for longer durations, such as a full work shift. These types of exposures would typically be assessed through OSHA PELs and ACGIH TLVs. Another exception holds true for members of the general public who are exposed to background chemical releases for longer durations. In these types of air quality issues, values such as the Environmental Protection Agency (EPA), National Ambient Air Quality Standards (NAAQS) and World Health Organization guidelines should be used rather than emergency response guideline concentrations.
Because there are only about 150 chemicals listed in the ERPG/WEEL Handbook, there are many substances that are not listed (considering that world-wide industry handles more than 500,000 substances regularly), toxicologists and other public health professionals use online references, such as the National Oceanic Atmospheric Administration (NOAA) CAMEO (Computer-Aided Management of Emergency Operations) website to find response recommendations and chemical data. This information, while available to the general public, should only be used by those trained in public health assessments.
Don’t ever take a fence down until you know why it was put up.