J Anaesthesiol Clin Pharmacol. 2011 Oct-Dec; 27(4): 435–437.
doi: 10.4103/0970-9185.86565
PMCID: PMC3214544
Anesthesia : Contributing to pollution?
Rakhee Goyal and Mukul Chandra Kapoor1
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This article has been cited by other articles in PMC.
Protecting the environment is a matter for concern for all. Any report on intrusion
of the environment by mankind attracts public glare. A recent article by Sulbaek
Anderson et al.[1] on climatic effects of inhalational anesthetics raked up the issue
of environmental pollution by anesthetic gases in contemporary media. Although
global climate changes are primarily attributed to emissions of carbon dioxide, the
reactions of the media on pollution by anesthetic gas emission were possibly not
unfounded.
Impact on Environment
Emission of infrared radiation into space is an important mechanism by which the
earth loses heat and cools down. Atmospheric pollution by molecules that hinder
the escape of the infrared radiation affects the temperature regulatory mechanisms
of the earth and thus affects the climate.
Anesthetic gases from anesthesia machines leaks, scavenging and from breathing
out by recovering patients, find their way to atmosphere. All waste anesthetic
gases (WAGs) particularly, halothane, enflurane, and isoflurane contain chlorine
and are believed to have significant ozone-depleting potential. The stability of the
molecules of halogenated inhalational anesthetics permits their passage to the
stratosphere, where solar ultraviolet radiation dissociates these molecules to
liberate free chlorine, which acts as a catalyst in the breakdown of ozone and
destruction of the ozone layer.[2]
Halogenated inhalational anesthetics strongly absorb the reflected infrared
spectrum of the outgoing terrestrial radiation. Their present contribution to climate
change is negligible in comparison to that attributable to carbon dioxide as their
atmospheric concentrations are negligible. However, as they are stable
compounds, their cumulative impact will possibly become significant enough to
force climate change.
Global warming potential (GWP — a metric adopted by the Kyoto Protocol to the
United Nations Framework Convention on Climate Change) is a relative measure
of the amount of heat a greenhouse gas traps in the atmosphere. Long time
measure of GWP is possibly more appropriate for long-lived gases, such as the
inhalational anesthetics. 100 year GWP is a time-integrated impact measure of
cumulative concentration of the greenhouse gas.
Assuming that about 200 million anesthetic procedures are performed annually in
the world, Sulbaek Anderson et al. estimated that the global emissions of inhaled
anesthetics will be equivalent to 4.4 million tonnes of carbon dioxide, i.e.,
equivalent to emissions (measured by 100 year GWP) from approximately 1
million passenger cars.[1] Emissions of nitrous oxide have been constant for a few
decades, and it is estimated that atmospheric concentration would be around 0.5
parts per billion, several times higher than the effect of emissions of halogenated
anesthetics. Although, the current climate effects of anesthetics are small and
clinical decisions about the effectiveness of different compounds should take
priority, there is a need to monitor their climate impact.[3]
Anesthesiologists, surgeons, scrub nurses, and operating room technicians spend
considerable time in the operation theater (OT). The pollution inside this closed
space may not be measurable but the long term effect of WAG in the environment
has always been a concern. Health and the safety of service providers are of
paramount importance to any health system. The increasing popularity of “Lowflow Anesthesia” has possibly reduced the pollution in this closed space but in the
absence of effective scavenging systems, there is a need to relook into the impact
of WAG. A large number of OTs in our country still do not use closed anesthesia
circuits, as is evident from the manuscripts received by our journal describing
delivery of anesthetic mixtures using Bain's circuit. Of the centers which use
closed circuits, a large number do not administer true “Low-flow Anesthesia.”
Nitrous oxide has been implicated to cause several general and systemic
dysfunctions.[4–6] It can lower the neuropsychological performance and cause
generalized symptoms such as fatigue, headaches, dizziness, nervousness, nausea,
concentration impairment, and lack of fitness. Peripheral neuropathy and
medullary depression with megaloblastic anemia, leucopenia, reduction in number
of B-lymphocytes, and thrombocytopenia may also occasionally occur. The use of
nitrous oxide has been discontinued in large part of the world but it continues to be
used in the Indian subcontinent. There have been several reports on unfavorable
effects on fertility and progress of pregnancy in the form of spontaneous abortions
and fetal anomalies due to nitrous oxide. This has been the major concern among
the female health personnel over the years and it has been studied extensively by
various authors.[7,8] Although, Spence et al.[9,10] showed that the incidence of
spontaneous abortion among those surveyed and congenital abnormalities among
their offspring were unrelated to the occupation of the mother, however, because
of long hours of exposure to the OT environment and nonavailability of
scavenging equipment, the scare still remains. Concern has been raised about the
carcinogenicity and mutagenicity of nitrous oxide and halogenated anesthetic
agents; however, studies on carcinogenicity have shown negative results.[11]
Animal studies, on long-term carcinogenicity, assessed organ toxicity after chronic
exposure to inhaled anesthetics and found no significant clinical or pathological
damage to the kidneys, liver, gonads, or other organs with maximum tolerated
doses of nitrous oxide, isoflurane, or halothane.[12] Sevoflurane and desflurane
have not been tested for carcinogenicity but have been tested for teratogenicity and
were found to be without reproductive toxicity.[13] In animal studies, only nitrous
oxide in high concentrations has been consistently shown to be teratogenic.
Understanding the potential risks of WAG in the OT environment has had a
historic evolution. In 1967, Vaisman reported that nitrous oxide, diethyl ether, and
halothane may be responsible for adverse reproductive and general systemic
effects.[14] In the same year, Fink et al. reported similar effects on reproductive
system by nitrous oxide and added the possibility of cancer, long term damage to
liver, kidneys and genetic mutation.[15] Similar adverse effects were reported by a
large study by the American Society of Anesthesiologists on the effects of trace
levels of WAG in 1974.[16] However, it was later realized that this study had
several limitations and biases and could not be relied upon. A group of
epidemiologists and statisticians conducted a study to bring out the facts. Buring et
al. reported an increased incidence of spontaneous abortions, congenital anomalies
and risk of liver and kidney damage.[17] Rowland et al. reported that scavenging
can prevent adverse reproductive outcomes following the use of nitrous oxide by
female dentists.[18] Other human epidemiological studies too detected adverse
effects with WAG, but admitted that the risks involved were small and well within
the range and might be due to confounding variables and bias.[17,19–21] These
studies had a number of weaknesses and did not recommend setting up of
exposure limits to WAG. In fact, these studies directed our focus on the other
reasons contributing to OT pollution like the stress of working in high risk milieu
of life and near death and to some extent, radiation exposure.
Inhaled anesthetic gases leak from anesthesia machine systems, as no system is
totally leak-free. The source of the leakage may be from both the high-pressure
and low-pressure systems of the anesthesia machine.[22] Moreover, lack of good
workplace practices such as leaving gas flow control valves open and vaporizers
on after use, spillage of liquid inhaled anesthetics, and poorly fitting face masks or
improperly inflated tracheal tube and laryngeal mask airway cuffs add to the
escape of WAG into the OT atmosphere. Machine leaks should be identified and
corrected before the system is used. OT pollution can be minimized by use of
scavenging systems, installation of more effective ventilation systems, and
increased attention to equipment maintenance and leak detection. An effective
scavenging system removes excess anesthetic gas at the point of origin and
reduces the amount of WAG significantly. Apart from the OTs other areas such as
recovery rooms also have WAG from the exhaled gases of the recovering patients.
It is advisable to place an exhaust in such an area so that WAGs are not
reintroduced in the workplace. The OT complex should have 15 air changes per
hour when in use and at least 3 air changes per hour at all times.[23] Periodic
monitoring of trace levels of WAG and that of personal exposure to health
personnel is also recommended.[24] The National Institute for Occupational
Safety and Health (NIOSH) USA recommended exposure limit (REL) for WAG at
25 parts per million (ppm) measured as a time-weighted average (TWA) during
the period of anesthetic administration for nitrous oxide, when used as the sole
inhaled anesthetic agent. There are no NIOSH REL's for the most common
anesthetics—isoflurane, desflurane, and sevoflurane.[23] European countries such
as Britain, Netherlands, Switzerland, France, and Germany have different
recommended standards and have REL for nitrous oxide and halogenated agents in
the range of 25–100 and 10–50 ppm, respectively, measured as TWA for 8 h.[25–
27]
There is insufficient evidence of undesired health problems due to WAG and
routine monitoring of trace levels of these gases is not required; however, lowflow anesthesia should be practiced by all to reduce pollution and also for
economic reasons. Scavenging of gases is strongly recommended along with
effective dilution ventilation. Good workplace practices and proper maintenance
of equipment to prevent leaks are required. Although evidence on environmental
pollution by anesthetic gases is presently viewed with skepticism, but we all
should be aware of such a possibility. Emission of WAG should be minimized by
good anesthetic practice and better OT management. All anesthesiologists must
endeavor to use only Low-flow anesthesia and ensure effective scavenging of
WAG. Effective education programs for the service providers and periodic
environmental monitoring, to check the effectiveness of the overall system, can
reduce WAG and their associated ill effects. Periodic training is essential in hazard
awareness, prevention, and control of exposure to WAG.
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