Levels of Concern Guide

A Level of Concern (LOC) is a threshold value of a hazard (such as toxicity or flammabilityA substance's tendency to ignite or take flame. Flammability is closely related to the volatility of a substance (and is not its relative ability to burn in the presence of oxygen with the evolution of heat).); the LOC is usually the value above which a threat to people or property may exist. CAMEO 365betÓéÀÖ provides up to four types of toxicPoisonous; can injure or kill people or other organisms. LOCs* on each chemical datasheet.

A toxic LOC is a way to measure the toxicity of a gas or vaporThe gas given off by a substance that is liquid (or solid) at normal temperatures and pressures.: it tells you what level (threshold concentrationThe amount of a chemical present in a given weight or volume of air. Concentration of a gas in air may be expressed in units such as parts per million (by volume) or milligrams per cubic meter.) of exposure to a chemical could hurt people if they breathe it in for a defined length of time (exposure duration). Generally, the lower the toxic LOC value for a substance, the more toxic the substance is by inhalation. Toxic LOCs also may be referred to as exposure limits, exposure guidelines, or toxic endpoints.

Most toxic LOCs have two components: a threshold concentration and an exposure duration. When the threshold concentration is exceeded for longer than the exposure duration, exposed people might experience the symptoms represented by the LOC.

Each toxic LOC is designed to reflect the hazard to either the general public (public exposure guidelines) or adult workers (workplace exposure limits).

Public Exposure Guidelines in CAMEO 365betÓéÀÖ

  • AEGLs (Acute Exposure Guideline Levels)
  • ERPGs (Emergency Response Planning Guidelines)
  • PACs (Protective Action Criteria for 365betÓéÀÖ)
Note that TEELs (Temporary Emergency Exposure Limits) are no longer shown specifically in CAMEO 365betÓéÀÖ, but they are included in the PACs dataset.

Workplace Exposure Limits in CAMEO 365betÓéÀÖ

IDLHs (Immediately Dangerous to Life and Health limits) are the only workplace exposure limits included in CAMEO 365betÓéÀÖ. See the workplace exposure limits topic for more information on common limits, including TLVs, RELs, and PELs.

How do I...?

  • Find a chemical's toxic LOCsFind a chemical's toxic LOCs
    1. Search for the chemical. How do I search for a chemical?
    2. Open the chemical datasheet for the chemical. In the contents section, expand the Physical PropertiesÌý²õ±ð³¦³Ù¾±´Ç²Ô.

    The toxicPoisonous; can injure or kill people or other organisms. LOCLevel of Concern. Threshold concentration of an airborne pollutant, usually the concentration above which a hazard to people is believed to exist. values (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)., ERPGsEmergency Response Planning Guidelines are levels of concern representing the adverse health effects of a hazardous substance on members of the general public. ERPGs are developed by the ERPG committee of the American Industrial Hygiene Association (www.aiha.org)., PACsProtective Action Criteria for 365betÓéÀÖ. This dataset includes the three common public exposure guidelines (AEGLs, ERPGs, and TEELs). When a chemical has been defined under multiple guidelines, the PACs dataset uses a hierarchical system to present a single set of values for each chemical., and IDLHImmediately Dangerous to Life and Health limits, levels of concern for adult workers; estimate of the highest concentration in air from which escape is possible without permanent injury (if their respirators fail). IDLHs are established by the National Institute for Occupational Safety and Health (www.cdc.gov/niosh).) established for this chemical are listed at the bottom of the Physical Properties section, if available.

  • Choose and use a toxic LOCChoose and use a toxic LOC

    You need an LOCLevel of Concern. Threshold concentration of an airborne pollutant, usually the concentration above which a hazard to people is believed to exist. to estimate the area where a toxicPoisonous; can injure or kill people or other organisms. hazard to people might exist—that is, to determine whether the concentrationThe amount of a chemical present in a given weight or volume of air. Concentration of a gas in air may be expressed in units such as parts per million (by volume) or milligrams per cubic meter. of an airborne gas is high enough to be hazardous to people. For example, during an emergency response to a toxic gas release you might need to determine whether gas concentrations measured by portable sensors exceed an LOC for the chemical.

    You can use a gas dispersion model like ALOHA to estimate the area where the gas concentrations might exceed an LOC (that is, to find the area where a hazard to people might exist).

    Choose an LOC that is appropriate for the population you're concerned about (response workers or the general public) and that has an appropriate exposure duration for your situation. For instance, AEGLs are developed for five exposure periods: 10 minutes, 30 minutes, 60 minutes, 4 hours, and 8 hours.

Note: In most cases, the toxic LOCs available on the chemical datasheets will be concentration threshold values based on toxicity. However, for some flammableEasy to ignite and burns readily. chemicals, the LOCs may have been based on the Lower Explosive LimitAlso called lower flammability limit. Lowest concentration of a flammable vapor in air at which explosion or combustion can occur. (or some percentage of it). If you have questions about whether a particular LOC value is based on toxicity or flammability, you should refer to the documentation provided by the LOC developers. (For developer websites, see the AEGL, ERPG, PAC, and IDLH pages.)