Microsoft Word Toxicology and Exposure Guidelines doc

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tox exposure guidelines (1)

General Guidelines

EXPOSURE GUIDELINES
It is necessary, during response activities involving hazardous materials, to acknowledge and
plan for the possibility that response personnel will be exposed to the materials present at some
time and to some degree. Most materials have levels of exposure which can be tolerated without
adverse health effects. However, it is most important to identify the materials involved and then
determine (1) the exposure levels considered safe for each of these materials; (2) the type and
extent of exposure; and (3) possible health effects of overexposure.
Several reference sources are available that contain information about toxicological properties
and safe exposure limits for many different materials. These sources can be grouped into two
general categories: 1) sources that provide toxicological data and general health hazard
information and warnings and 2) sources that describe specific legal exposure limits or
recommended exposure guidelines.
Both types of sources, considered together, provide useful information that can be used to assess
the exposure hazards that might be present at a hazardous materials incident. In the following
discussion, these sources are described in greater detail.
General Guidelines
The effects of chemical exposure with the route and dosage required can be found in NIOSH's
Registry of Toxic Effects of Chemical Substances. However, because most of the data is for
animal exposures, there may be problems in trying to use the data for human exposure
guidelines.
Other sources give some general guides on chemical exposure. They may say that the chemical is
an irritant or corrosive, or they may give a warning like "AVOID CONTACT" or "AVOID
BREATHING VAPORS." This gives the user information about the possible route of exposure
and effects of the exposure. However, this does not give a safe exposure limit. One may question
whether the warning means to "AVOID ANY POSSIBLE CONTACT" or whether there is a
certain amount that a person can contact safely for a certain length of time.
Two sources of information go a little further and use a ranking system for exposure to
chemicals. Irving Sax, in Dangerous Properties of Industrial Materials, gives a Toxic Hazard
Rating (THR) for certain chemicals. These ratings are NONE, LOW, MODERATE, and HIGH.
The route of exposure is also given. For example, butylamine is listed as a HIGH toxic hazard
via oral and dermal routes and a MODERATE toxic hazard via inhalation. HIGH means that the
chemical is "capable of causing death or permanent injury due to the exposures of normal use;
incapacitating and poisonous; requires special handling."
In the book, Fire Protection Guide on Hazardous Materials, the National Fire Protection
Association (NFPA) also uses a ranking system to identify the toxic hazards of a chemical. These
numbers are part of the NFPA 704 M identification system. The numbers used range from 0 to 4
where 0 is for "materials which on exposure under fire conditions would offer no health hazard
beyond that of ordinary combustible material" and 4 is for materials where "a few whiffs of the

(Created 12/02)
UNL Environmental Health and Safety · (402) 472-4925 · http://ehs.unl.edu
gas or vapor could cause death; or the gas, vapor, or liquid could be fatal on penetrating the fire
fighters' normal full protective clothing which is designed for resistance to heat." The degree of
hazard is based upon the inherent properties of the chemical and the hazard that could exist under
fire or other emergency conditions. This rating is based on an exposure of "a few seconds to an
hour" and the possibility of large quantities of material being present. Thus it is not completely
applicable to long-term exposure to small quantities of chemicals. It is more useful for spills or
fires where a person could come in contact with a large amount of the chemical.
The Sax and NFPA sources provide information about the routes of exposures and some effects
along with a rating system which indicates which chemicals require extra precaution and special
protective equipment.

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