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Superfund Risk Assessment: Human Health: Acute Hazards

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As used here, Acute Threats are defined as: conditions that create the potential for injury or damage to occur to humans or environmental receptors as a result of an instantaneous or short duration exposure to the effects of an accidental release. These conditions may be either chemical or physical in nature and may include toxic, flammable, reactive, explosive, or radioactive hazards.

The EPA evaluates the severity of acutely toxic chemicals by measuring the concentration or dose level that could cause death or serious irreversible health effects after a short exposure. For physical hazards, EPA focuses on other types of effects, such as blast waves from vapor cloud explosions from a flammable substance, as the most serious hazard.

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EPA Links

  1. EPA’s Office of Resource Conservation and Recovery's combustion risk Assessment guidance provides a methodology for calculating an acute inhalation hazard quotient (HQ) in Table C-4-1 of the attached guidance.

  2. National Advisory Committee for Acute Exposure Guideline Levels (NAC).
    EPA’s Office of Prevention, Pesticides and Toxic Substances established the NAC in 1995 to develop Acute Exposure Guideline Levels (AEGLs) and supplementary information on hazardous substances for federal, state, and local agencies and organizations in the private sector concerned with emergency planning, prevention, and response. The NAC is a discretionary Federal advisory committee that combines the efforts of stakeholders from the public and private sectors to promote efficiency and utilize sound science.

    Since it began AEGL development with an initial priority list of 85 chemicals in May 1997, the NAC has produced AEGLs for 146 substances (available on EPA's website at http://www.epa.gov/oppt/aegl/). The AEGLs for a substance take the form of a matrix, with separate levels for mild (AEGL-1), moderate (AEGL-2), and severe (AEGL-3) effects. Each of the effect levels are provided for as many as five different exposure periods, typically 10 and 30 minutes and 1, 4, and 8 hours. Table 2 provides the 1-and 8-hour concentrations for the AEGL-1 and -2, with a superscript that identifies whether the value is final, interim, or proposed.

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External Links

  1. The U.S. Agency for Toxic Substances and Disease Registry (ATSDR)
    Developes chronic, intermediate and acute minimal risk levels (MRLs) for some contaminants. An acute MRL is considered an acute Human Health Toxicity value.

  2. California Environmental Protection Agency (CalEPA).
    CalEPA has developed acute dose-response assessments for many substances, expressing the results as acute inhalation reference exposure levels (RELs). As with its chronic RELs, CalEPA defines the acute REL as a concentration level at (or below) which no health effects are anticipated. CalEPA's acute RELs are available on-line.

  3. American Industrial Hygiene Association (AIHA).
    AIHA has developed emergency response planning guidelines (ERPGs) for acute exposures at three different levels of severity. The AIHA emergency response planning guidelines Link to EPA's External Link Disclaimer are available on-line through the US Department of Energy, represent concentrations for exposure of the general population for up to 1 hour associated with effects expected to be mild or transient (ERPG-1), irreversible or serious (ERPG-2), and potentially life-threatening (ERPG-3). Table 2 provides the ERPG-1 and -2 values.

  4. National Institute for Occupational Safety and Health (NIOSH).
    As part of its mission to study and protect worker health, NIOSH determines concentrations of substances that are immediately dangerous to life or health (IDLHs). IDLHs were originally determined for 387 substances in the mid-1970's as part of the Standards Completion Program (SCP), a joint project by NIOSH and the Occupational Safety and Health Administration (OSHA), for use in assigning respiratory protection equipment. NIOSH is currently evaluating the scientific adequacy of the criteria and procedures used during the SCP for establishing IDLHs. In the interim, the IDLHs have been reviewed and revised. NIOSH maintains an on-line database of IDLHs, including the basis and references for both the current and original IDLH values (as paraphrased from the SCP draft technical standards). Table 2 provides IDLH values divided by 10 to more closely match the mild-effect levels developed by other sources, consistent with methodology used to develop levels of concern under Title III of the Superfund Amendments and Reauthorization Act, and their use in the accidental release prevention requirements under section 112(r) of the Clean Air Act.

  5. U.S. Department of Energy (DOE).
    DOE has defined Temporary Emergency Exposure Limits (TEELs) Link to EPA's External Link Disclaimer, which are temporary levels of concern (LOCs) derived according to a tiered, formula-like methodology (described at METHODOLOGY FOR DERIVING TEMPORARY EMERGENCY EXPOSURE LIMITS (PDF) (41 pp, 130K, About PDF). DOE describes TEELs as "approximations of potential values" and "subject to change." The EPA’s emergency planning program (section 112(r)) does not generally rely on them, and they are provided in Table 2 purely to inform situations in which no other acute values are available. For example, a finding of an acute exposure near a TEEL may indicate the need for a more in-depth investigation into the health effects literature. TEELs are not recommended as the basis of regulatory decision-making. Like ERPGs, TEELs are multiple-tiered, representing concentrations associated with no effects (TEEL-0), mild, transient effects (TEEL-1), irreversible or serious effects (TEEL-2), and potentially life-threatening (TEEL-3). Consistent with DOE's intent, Table 2 provides the TEEL-0 and -1 concentrations for substances that lack acute values from other sources.

  6. National Library of Medicine (NLM) Hazardous Substances Data Bank
    Broad scope in human and animal toxicity, safety and handling, environmental fate, and more. Scientifically peer-reviewed.

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