STANDARDS FOR EXPOSURE TO AIRBORNE CONTAMINANTS

1
STANDARDS FOR EXPOSURE TO
AIRBORNE CONTAMINANTS
Yves Alarie, Ph.D Professor Emeritus
University of Pittsburgh,USA
2
A. STANDARDS OR GUIDELINES A variety of standards
have been promulgated. Some are Federal
standards, while others are guidelines
promulgated by different groups. Table 18
provides a summary and the definition of the
most important. a) National Ambient Air Quality
Standards (NAAQS). Established by EPA, following
a review of the literature on a particular
substance. The review is published as an "Air
Quality Criteria Document" and readily available
in libraries. The current NAAQS are listed in
Table 19.
3
b) Threshold Limit Values (TLV) Biological
Exposure Indices (BEI). These are established by
the American Conference of Governmental
Industrial Hygienists (ACGIH) which was
established in 1938. It started issuing exposure
guidelines in 1946 for a small number of
industrial chemicals and there is a TLV for about
600 industrial chemicals. Each year it published
a booklet (1) listing those values. This booklet
is available from Executive Secretary ACGIH 6500
Glenway Avenue, Building D-7 Cincinnati, Ohio
45211-4438
4
More recently the ACGIH has introduced Biological
Exposure Indices (BEIs) as reference values
intended as guidelines for evaluation of
potential health hazards in the practice of
industrial hygiene. These, unlike TLVs which
refer to an air concentration, are for amount of
the chemical or its metabolite in blood, urine,
exhaled air, etc. There are 34 established
and/or proposed BEIs.
5

Both TLVs and BEIs are established after a
literature review, much more extensive for BEIs
than for TLVs and this review is published.66
In this publication you can find the basis for
establishing a TLV or BEI. Many TLVs have been
recently reviewed and much more extensive
documentation is now available. Also there have
been obvious changes over the years as to what
the committee members regard as an adverse
health effect and what "most workers" means.
Twenty years ago "most workers was about 85.
Now I don't know.
6

• It should be kept in mind that these values
  are guidelines, developed initially for Normal,
  Healthy, Adult, Male, not female and certainly
  not pregnant females.
• Before you can use these values you should
  read the "Preface" which is now 10 pages long in
  the booklet. Also you should read the
  Documentation for each substance that you are
  interested in.

7

• c) Permissible Exposure Limit ( PEL).
• These are established by the Occupational
  Safety and Health Administration (OSHA). They
  are THE LAW.
• In 1970, OSHA used the TLVs values published
  in 1968 by the ACGIH and made those values PELs.

8

• In 1989, OSHA revised its list of PEL by
  adopting the ACGIH 1987-88 TLVs with a few
  exceptions. You can obtain these from
• "NIOSH Pocket Guide to Chemical Hazards, June
  1990"67. This publication contains a variety of
  other information for all the listed chemicals
  and is very useful to have, or as reprinted68.
  However, this revision was challenged in court
  and reversed.
• See Table 18.

9

• d) Recommended Exposure Level (REL).
• The National Institute of Occupational Safety
  and Health (NIOSH) develop these for the
  workplace and transmits them to OSHA and the Mine
  Safety and Health Administration (MSHA) for use
  in promulgating legal standards i.e., PEL. For
  each chemical there is a "Criteria for a
  Recommended Standard" document. There are about
  120 of these documents available in libraries.
  They are a good source of information, not only
  on the toxicity of the chemical but also work
  practices, medical surveillance, protective
  equipment, etc. Unfortunately they are now out
  of date.

10

• e) Air Toxics.
• These are more recent and established by each
  State. They are ambient air criteria for the
  general population. A variety of approaches have
  been taken. A popular one is to take the PEL and
  divide it by some factor to take into account the
  fact that the general population would be exposed
  24 hrs/day and 7 days/week instead of the PEL or
  TLV which is for 8 hrs/day and 5 days/week. Then
  you can throw in some safety factors of 10 and
  another safety factor of 10 if there is any rumor
  that one rat somewhere got cancer. You end up
  with a number. Nonsense.

11

• B. ESTABLISHING A TLV OR PEL
• a) Types of Data.
• There is no established protocol to develop a
  TLV or PEL. The types of data assembled to
  arrive at a decision will include the following
• - Human exposures, laboratory
  experiments
• - Human exposures, on the job
• - Human exposures, accidental exposures
• - Animal exposures

12

• b) Types of Effect.
• i) Health Hazard
• Any type of toxicological effect can be
  considered to establish a TLV or PEL. A review
  of the Documentation for TLV and the Lecture
  Notes of Dr. H. F. Smyth Jr. of the University of
  Pittsburgh was undertaken by OSHA to get an idea
  of the major health hazard categories used to
  establish TLVs. These are given in the Table.
  As you can see there are large differences, from
  nauseating odor to cancer. Therefore, when you
  see that a TLV for X is 10 ppm and a TLV for Y is
  100 ppm don't conclude that X is 10 times more
  toxic than Y. This is the worst mistake you can
  make.

13

• ii) "Good Housekeeping"
• - No TLV above 10 mg/m3 for any aerosol,
  including "nuisance or inert dust
• - No TLV above 1,000 ppm for gases or vapors,
  except for CO2 (TLV 5,000 ppm) or for simple
  asphyxiants which are permitted up to 3
  (reduction of O2 content to 18) at sea level
  pressure (760 mmHg) or to an equivalent partial
  pressure of O2 of 135 mmHg.