Current Intelligence Bulletin (CIB): Derivation of Immediately Dangerous to Life and Health (IDLH) Values

In 1974, the National Institute for Occupational Safety and Health (NIOSH) and the Occupational Safety and Health Administration (OSHA) jointly initiated the Standards Completion Program (SCP). The intent of this program was to develop occupational health standards consistent the Occupational Safety and Health Act of 1970 for substances with then-existing OSHA permissible exposure limits (PELs). As part of the respirator selection process for each draft technical standard, Immediately Dangerous to Life and Health (IDLH) values were determined for each chemical. The purpose of deriving an IDLH value was to provide guidance on respirator selection and to establish a maximum exposure concentration at which workers, in the event of respiratory protection failure (e.g., contaminant breakthrough in a cartridge respirator or stoppage of air flow in a supplied-air respirator), could escape safely when the exposure was below the IDLH value.

Since the establishment of the original IDLH values in 1974, NIOSH has continued to review the available scientific data to improve the protocol used to derive the acute exposure guidelines, in addition to the chemical-specific IDLH values. This draft Current Intelligence Bulletin (CIB) entitled Derivation of Immediately Dangerous to Life and Health (IDLH) Values represents the most recent update of the scientific rationale and protocol used to derive IDLH values based on health effects considerations determined through a critical assessment of the toxicology and human health effects data.

The new protocol outlined in the draft CIB relies on a weight-of-evidence approach based on scientific judgment for establishing IDLH values that allows for the critical evaluation of the quality and consistency of the scientific data, and in extrapolation from the available data to the IDLH value. The weight-of-evidence approach refers to the critical examination of all the available data from diverse lines of evidence and the derivation of a scientific interpretation based on the collective body of data including its relevance, quality and reported results. Guidelines are presented to aid in the selection of the critical adverse effect, a point of departure (POD) or the point on the dose-response curve from which dose extrapolation is initiated, and applying default uncertainty factors (UFs) to derive the IDLH value. Conceptually, the derivation process presented in this CIB is similar to that used in other risk assessment applications including the process steps of:

Hazard characterization,
Identification of critical adverse effects,
Identification of a POD,
Application of an appropriate UF based on the study and POD, and
Determination of the final risk value.

NIOSH has determined this draft CIB to be an Influential Scientific Assessment (ISA) in accordance with the Office of Management and Budget (OMB) guidelines under the Federal Data Quality Act 2000 (Public Law 106-554, Section 1(a)(3)[515]). As part of the development of this document, NIOSH is submitting the draft CIB to the public for review and is requesting comments regarding its technical accuracy and usefulness. The draft CIB do not have the force and effect of law. The overall goal of the review is to enhance the quality and credibility of NIOSH recommendations by ensuring that the scientific and technical work underlying these recommendations receives appropriate review by independent scientific and technical experts.

Public Review

The external review of the draft CIB has been (1) developed in accordance with OMB guidelines, (2) is consistent with NIOSH peer review practice, and (3) is meant to ensure that credible and appropriate science is used in the derivation of IDLH values.

Draft Preliminary Public Comment Version:

Current Intelligence Bulletin (CIB): Derivation of Immediately Dangerous to Life and Health (IDLH) Values [PDF - 2,102 KB]

Public Comment Period

Written comments on the document will be accepted through March 15, 2011 in accordance with the instructions below. All material submitted to NIOSH should reference Docket Number NIOSH-156. All electronic comments should be formatted as Microsoft Word and make reference to docket number NIOSH-156.

Comments will be accepted until 5:00 p.m. EDT on March 15, 2011

To submit comments, please use one of these options:

Send NIOSH comments using this online form
Send comments by email.
Fax comments to the NIOSH Docket Office: 513-533-8285
Send by Mail to:
NIOSH Mailstop: C-34
Robert A. Taft Lab.
4676 Columbia Parkway
Cincinnati, Ohio 45226

A complete electronic docket containing all comments submitted will be available on the NIOSH docket home page, and comments will be available in writing by request. NIOSH includes all comments received without change in the docket, including any personal information provided.