American Conference of Governmental
Industrial Hygienists (ACGIH). (1989).
Threshold Limit Values and Biological
Exposure Indices for 1989-1990.
Cincinnati, OH: Author. pp. 22, 25, 32.
Health Council of the Netherlands: Dutch
Expert Committee on Occupational
Standards (DECOS). Enflurane,
Isoflurane and Cyclopropane.
(1998) Den Haag: Health Council
of the Netherlands; publications no.
Health Service Advisory Committee
(HSC). Anaesthetic Agents: Controlling
Exposure Under COSHH. (1995) HSE
Books, Sheffield, UK. ISBN 0 7176
National Institute for Occupational Safety
and Health (NIOSH). NIOSH Criteria
Document 77-140 [-] Criteria for a
Recommended Standard of Exposure
to Waste Anesthetic Gases and Vapors.
(March 1977) www.cdc.gov/niosh/
National Institutes of Health, Office
of Research Services, Division of
Occupational Health and Safety
(DOHS). Waste Anesthetic Gas (WAG)
Surveillance Program. (November
Documents/Waste Anesthetic Gas
(WAG) Surveillance Program.pdf
Occupational Safety and Health
Administration (OSHA). Anesthetic
Gases: Guidelines for Workplace
Exposures. ( 18 May 2000) www.osha.
Brett Field graduated from from Rutgers
University and has obtained the ALAT
certification from AALAS. He joinedEu-thanex in 2005 and has been actively
involved in the design, manufacture
and maintenance of small laboratory
animal anesthesia systems. (610)882-
3800, firstname.lastname@example.org, www.
Want to read more about
regulations? Go to www.alnmag.
have worked to set acceptable exposure
limits (Table 1).
The UK standards, introduced in
1994, outline exposure limits of 10 ppm
halothane and 50 ppm isoflurane, highlighting a trend towards setting lower
limits for halothane than newer drugs.
The relative safety of isoflurane and
enflurane vs halothane is often used as
a gauge for setting limits, as seen in the
ACGIH report for enflurane.
Another notable European example
is that of the Dutch Expert Committee on Occupational Standards (
DECOS), which set an REL of 20 ppm for
isoflurane in 1998. Faced with a lack of
information, DECOS relied on the simi-larities between enflurane and isoflurane when determining this value. This
conjecture has been the justification for
several policies on isoflurane.
THE FUTURE OF REVISED
Though NIOSH has yet to publish a new
guideline for isoflurane, sevoflurane, and
desflurane, institutional polices are already changing in anticipation of revised
standards. In 2012, the NIH adopted the
ACGIH TLVs of 75 ppm enflurane and 50
ppm halothane as part of their Waste Anesthetic Gas (WAG) surveillance program.
This shows that the biomedical research
industry is moving
away from the original
NIOSH standard. A
cursory web search re-
veals other institutions
that have adopted
either the ACGIH TLVs,
abroad, or a combina-
tion thereof. Consider-
ing increasing evidence
and current trends it is
likely the industry will
continue to move away
from the two ppm
REL for isoflurane and
The need for strict
safety protocols when
using halogenated agents is without
question. In spite of any uncertainties
stemming from flawed research or inad-
equate information, the weight of evi-
dence for potential health risks dictates
that exposure to these agents should be
controlled to the lowest practical level.
It is tempting to reason that until a
100% definitive safe level of exposure
has been determined for isoflurane or
sevoflurane that RELs should remain very
low. However, there are negative costs
associated with a zero tolerance approach
to exposure that should be considered,
the most important being compliance.
With thorough training, good tech-
nique, and quality equipment, it is
possible to reduce user exposure to rea-
sonable levels, even when using a basic
tabletop anesthesia system, but it can
be costly and time consuming to reduce
exposure to near zero in many cases.
In laboratories with limited resources
or oversight this often results in an
apathetic attitude towards exposure. If
the RELs are perceived to be impracti-
cal or not based on reality then they are
easier to ignore.
Airgas. Oxidizing Gas Mixtures [Material
Safety Data Sheet] (April 2013). www.
UK TWA: 50
IRELAND TWA: 50
SWITZERLAND STEL: 80
NETHERLANDS TWA: 20
SWEDEN STEL: 20
FINLAND STEL: 20
NORWAY TWA: 2 TWA: 20
STEL: Short Term Exposure Limit, 15 minutes
TWA: Time Weighted Average, 8 hours
Table 1: Here is a small sample of current exposure limits for isoflurane
and sevoflurane in European countries.