VA Medical Center Medical Center Memorandum ( )

(LOCATION) (DATE)

Waste Anesthetic Gases and Vapors Hazard Control Program

1\. ***Purpose.*** The purpose of this policy is to briefly outline the
responsibilities for the various program elements of the medical
center's Waste Anesthetic Gas and Vapors Hazard Control Program.

2\. ***Background.*** Responding to the scientific literature indicating
there may be adverse health effects associated with exposure to waste
anesthetic gases and vapors, the medical center has established a
program to meet the recommendations of Occupational Health Advisory
Agencies (NIOSH and ASA) and to comply with JCAHO accreditation
criteria.

3\. ***Responsibilities.***

a\. *Engineering Service* will be responsible for preventive maintenance
of affected HVAC systems, scavenging systems, and anesthesia units.

b\. *Safety Specialist/Industrial Hygienist* will coordinate all
industrial hygiene monitoring and leak testing, review the training
programs conducted by the other services, keep records on air sampling,
notify exposed employees of the results of air sampling, and see that
exposure records are forwarded to Employee Health to be placed in
medical records.

c\. *Surgical, Nursing, Dental, and Research Services* will be
responsible for annual training and encouraging their staff in the use
of work practices designed to reduce ambient waste anesthetic gases
during the administration of anesthesia. They will keep records on the
training dates, topics, and attendees. These individual services will be
responsible for seeing that their exposed employees are identified for
baseline and annual medical surveillance through the Employee Health
Unit (NIOSH, ASA).

4\. ***Exposure Limits.*** Exposure limits have been recommended by the
American Conference of Governmental Industrial Hygienists (ACGIH) and
NIOSH. OSHA does not currently have Permissible Exposure Limits (PEL)
for anesthetic gases (other than chloroform and trichloroethylene, which
are not addressed here because it is believed they are not used as
anesthetics in VAMCs). See the attachment to this memorandum for a
summary of exposure limits. See paragraph 4.g. for recommendations for
VAMC exposure limits.

a\. All of the Agencies involved, ASA, NIOSH and ACGIH, admit that there
are not sufficient data to establish safe occupational exposure levels
for anesthetic gases, and that the recommended limits are merely based
on lowering the exposure to levels that are considered achievable with
current technology. All three groups stated that in Dental Operatories
it may not be possible to reduce exposure to nitrous oxide below 50
parts nitrous oxide per million parts air (ppm).

b\. NIOSH recommends an exposure limit of 25 ppm for nitrous oxide, as a
Time-Weighted Average (TWA) over the period when anesthesia is being
administered to the patient which should be the period of highest
exposure. This is calculated differently from an 8-hour TWA. An 8-hour
TWA takes into the calculation the exposure estimate of the entire
shift, several hours of which might be spent outside of the operating
room. NIOSH's exposure limits are expressed as TWA over the period of
anesthesia administration. This time period will vary depending on the
procedure from a few minutes to several hours.

c\. The NIOSH recommendation for halogenated agents is 2 ppm as sampled
during the administration period not to exceed one hour. NIOSH notes
that when administered with nitrous oxide, halogenated agents will be
below 0.5 ppm when the nitrous oxide is below 25 ppm.

d\. On the surface, it would appear that these exposure limits do not
cover employees working in the recovery room. An assumption in the NIOSH
limits is that there is good exposure control in every phase of the
anesthesia process, not just during administration. Given that scenario,
the period of highest exposure would be during gas and vapor
administration. Therefore, it is expected that exposures during periods
other than administration of the gas, such as afterward in the operating
and recovery rooms, dental operatories, and research rooms, should be
much lower than the limits recommended for anesthesia administration.
This will be achieved only when good equipment control, ventilation, and
work practices are utilized. A method for confirming good control is to
conduct air sampling during these nonadministration periods. As a rule
of thumb, exposure levels in these circumstances should be below 25 ppm
nitrous oxide.

e\. These exposure limits do not address exposure of operating room
personnel during the use of unventilated cryosurgical units which have
been known to leak large amounts of nitrous oxide.

f\. In 1987 ACGIH proposed a Threshold Limit Value - Time-Weighted
Average (TLV-TWA) for nitrous oxide of 50 ppm. In 1980 ACGIH proposed a
TLV-TWA for enflurane of 75 ppm. The TLV-TWA proposed in 1980 for
halothane is 50 ppm. All three proposed TLV-TWA levels are the current
values adopted by ACGIH as of 1993-1994. All TLV-TWA are calculated for
an 8-hour shift.

g\. Model Exposure Limits. Since no safe exposure level has been
established, a prudent Industrial Hygiene program will utilize the
lowest limits achievable; which, in this case, are recommended by NIOSH
(Nitrous oxide 25 ppm, halogenated agents 2 ppm).

5\. ***Exposure Control Strategies.***

a\. Use of scavenging systems.

b\. Routine leak detection.

1\) High pressure system - quarterly.

2\) Low pressure system - daily.

c\. Regular equipment maintenance.

d\. Efficient low leakage anesthesia administration techniques.

e\. Air monitoring - quarterly.

f\. Periodic evaluation of the ventilation system.

g\. Proper venting of the scavenging system.

6\. ***Exposure Control Methods.***

a\. General. Strategies for exposure control including engineering
control methods and work practices have been recommended by NIOSH and
ASA and are summarized below:

1\) The implementation of exposure control strategies should be included
in the training conducted for exposed personnel. Biomedical equipment
repair personnel and those who operate the anesthesia equipment and
Cryosurgical Units should be especially familiar with these methods.

2\) Exposure control methods that are built-in the equipment include gas
scavenging devices, patient face masks or tubes that reduce leakage, and
quick disconnect hoses. Room ventilation can also contribute to exposure
control.

3\) Work practices of those who operate the anesthesia equipment can be
a source for reducing the exposure for themselves and others in the
room.

b\. Delivery System of Medical Gases. Medical gases such as nitrous
oxide may be delivered to the anesthesia unit from a bulk storage
facility. Usually, this consists of a cylinder duplex manifold system.
VA Master Specification H-08-1, Section 15315, details specific
requirements for such a system. In addition, 29 CFR 1910.105 requires
that transfer and distribution of nitrous oxide shall be designed,
installed, maintained, and operated in accordance with Compressed Gas
Association G-8.1-1964. Compressed gas cylinders may also be used to
deliver medical gases to the anesthesia unit. All personnel must be
provided with appropriate job training in the handling of compressed gas
cylinders.

c\. How Anesthesia is Administered.

1\) Two kinds of substances are administered for general anesthesia:

a\) Nitrous Oxide is a gas at room temperature and is a nonflammable,
colorless, sweet-tasting gas that is heavier than air.

b\) Halogenated anesthetic materials are liquids at room temperature.
When vaporized they are 5 to 7 times heavier than air. Enflurance
(ethrane) and halothane (fluothane) are nonflammable liquids which
vaporize easily. Halothane is colorless and has a sweet odor.
Methoxyflurane (penthrane) is a combustible colorless liquid with a
fruity odor.

2\) The most commonly used method for administering anesthesia in the OR
is through a high-flow, semiclosed rebreathing system with a carbon
dioxide absorber. The carbon dioxide absorber unit is equipped with a
pop-off valve (expiration or pressure relief valve) which may be the
chief source of gas leakage.

3\) The anesthesia unit is usually equipped with a vaporizer designed to
convert a volatile liquid anesthetic agent into a vapor and to
administer a controlled volume or concentration. This vapor is mixed
with other gases and then delivered to the patient but in a greater
volume than the patient's metabolic requirements. Excess vapor is vented
out of the breathing system through the pop-off valve in order to
prevent overfilling.

d\. Scavenging is the collection and disposal of waste gases and vapors
from the breathing systems at the site of overflow. Scavenging assists
in the prevention of anesthetic dispersion into the room air, and is a
form of local exhaust ventilation.

1\) Most scavenging systems consist of two components: a collection
device (or scavenging adapter) to collect waste gases, and a disposal
route to carry them out of the room. In the absence of scavenging, the
air in any given operatory may contain WAG from an adjacent suite where
it is used. WAG may also enter an operatory from adjacent rooms via
window, door, and air conditioning inlets, or from the dental suction
unit when the exhaust is not vented to a site outside the building.

2\) The disposal route should vent these gases away from personnel and
away from the hospital ventilation intake. The scavenging system may be
part of a nonrecirculating air conditioning system, a central room
suction, or separate duct system used solely for waste gas disposal.

3\) Scavenging systems themselves may be a source of leakage through
failure of connections, tubing defects, or inadequate design.

e\. Ventilation. The following are VA minimum air change rates:

1\) Operating Rooms - 15 room air changes/hour.

2\) Recovery Rooms - 8 room air changes/hour.

3\) Animal Research - 15 room air changes/hour.

f\. Maintenance and Leakage. An ongoing preventive maintenance program
is absolutely essential to assure proper functioning of the anesthesia
unit and scavenging system. The main problem with an anesthesia unit
from an industrial hygiene standpoint is gas leakage.

1\) Leakage from OR equipment may originate with high pressure or low
pressure systems. The high pressure system carries the gas from the tank
to the anesthesia unit, while the low pressure system carries gas from
the anesthesia unit to the patient.

2\) The components of high and mid-pressure systems (located between
high pressure nitrous oxide source and the flowmeters) may release
gases. Leaky wall connectors, loose high-pressure hose connections, or
deformed compression fittings may provide an escape route for waste
gases.

3\) The components of the low pressure systems (located between the
flowmeters and the patients) are also potential leak points. There are
multiple sites at which leakage can occur: at loose or defective gaskets
and seals, at worn-out or defective bags and breathing hoses, at loose
flowmeter tubes, and at inadequately sealed oxygen absorption units. The
anesthetic machine may be a leakage source.

4\) Another possible source of leakage in the OR is the diffusion of
anesthetic gases through rubber and plastic material (breathing tubes,
bags, scavenger lines).

5\) Recommended Leak Checks. NIOSH and ASA recommend that high pressure
systems be leak tested quarterly and low pressure systems be tested with
each use.

g\. Anesthetic Techniques. An important factor contributing to the
levels of waste anesthetic gases in the OR is the work practices of the
Anesthetist. The failure to properly connect and utilize scavenging
equipment, the use of poorly fitted face masks and endotracheal tubes,
or leaving the gases on when the anesthesia unit is disconnected from
the patient may contribute greatly to gas concentrations in the air.

h\. Dental Operatories. Anesthesia in the dental laboratory is delivered
at a much higher flow rate than in the OR. Nonbreathing circuits are
primarily used. Gases may leak into the room through the exhalation
valve, around the nasal mask, and through the patient's mouth. When
dental operations are in progress in more than one operatory at once,
nitrous oxide cross contamination can be a substantial problem. The air
conditioning system can distribute the nitrous oxide from one suite to
another.

i\. Animal Research Facilities. Nitrous oxide, halothane, and
methoxyflurane are the anesthetics most frequently used in veterinary
anesthesia. Animal researchers may use closed systems, semi-closed, and
rebreathing systems for anesthesia. Significant exposures may occur to
research personnel due to problems of good fit with nose and face masks,
and the frequent use of the T-tube for smaller animals. Animal
operatories converted from storage space, frequently have recirculating
systems as opposed to the nonrecirculating ventilation systems in
hospital operating rooms. In addition, there is frequently an absence of
scavenging systems for removal of waste gases.

7\. ***Exposure Monitoring.***

a\. Air Sampling*.* Both NIOSH and ASA recommend quarterly equipment
leak tests and breathing zone air sampling. Additional air sampling may
be needed when equipment or techniques are modified. Air sampling may be
performed by the facility IH/Safety staff or an Industrial Hygiene
Consulting Firm. If a Miran IR Analyzer is not available at the medical
center, plans should be made to purchase one. In the meantime, one may
be borrowed from the VISN Office, provided safe transportation and
prompt return can be assured.

1\) All exposure limits mentioned above are based on personal sampling;
that is, air sampling conducted in the breathing zone of the exposed
employees. Typically, the results from several air measurements with the
Miran in the breathing zones of the anesthesiologist, surgeon, and
nurses are averaged (for each person) to estimate a TWA for each person
for the anesthesia administration period. Passive dosimeters are worn to
confirm the results or to measure other agents.

2\) NIOSH identifies direct infrared analysis (the Miran) as the most
desirable method and the measurement of nitrous oxide as a good
indicator of the levels of halogenated agents when they are mixed with
it. Sampling studies show that when levels of nitrous oxide are below
the target 25 ppm, levels of halogenated agents are around 0.5 ppm.

b\. Leak Tests are conducted, using direct reading instruments (Miran)
for the purpose of detecting where gas is escaping from the anesthesia
system. As a follow-up to leak tests, immediate repair or adjustment of
the equipment is essential to the exposure control program. Equipment
leak tests may be conducted when the anesthetic equipment is not in use;
that is, when anesthetic procedures are not in progress. It may be
useful to have the equipment operator (anesthesiologist, dentist,
research investigator, or nurse anesthetist) and the biomedical repair
person in attendance.

c\. Breathing Zone Sampling*.* Breathing zone air samples should be
conducted during normal use of the equipment; that is, during surgical,
dental or laboratory animal procedures. When using the Miran to obtain
instantaneous measurements which then need to be averaged to estimate
the time-weighted average; if an automatic recorder is not used, it is
important to write down the sample beginning and ending times and as
many different measurements as possible for later averaging. Passive
dosimeters for organic vapor monitoring can be used to estimate
time-weighted average exposures to enflurane and halothane. They should
be worn during the entire anesthesia procedure period of one day and
then sent for analysis. Passive dosimeters for nitrous oxide are
available and are more precisely compared to recommended exposure limits
when they are sent for analysis after a one day, rather than a one week,
exposure period.

d\. Sampling Tips. The following are suggestions to consider when
initiating air sampling. These are most appropriate for air sampling in
the operating room, but many can be applied to sampling in the dental
operatory or research laboratory.

1\) Brief anesthesiology and OR staff well in advance on what you are
going to do.

2\) Try to schedule sampling during prolonged procedures such as hip
replacements.

3\) Check with surgery early in the morning of your scheduled sampling
day to confirm that you may proceed.

4\) Calibrate the Miran before you enter the OR. Note that the clean air
(charcoal) filter used to zero the Miran does not adsorb nitrous oxide.
Therefore, the instrument should be "zeroed" in air free of nitrous
oxide.

5\) Allow yourself sufficient time to gown-up and transport your
sampling devices to the OR.

6\) Once inside the OR keep well away from sterile fields, usually
identified by blue drapes.

7\) Observe that scavenging systems are used.

8\) Sample the air around connectors and fittings on the anesthesia
unit.

9\) Begin by sampling the breathing zone level at the anesthetist's
position; then, as the opportunity arises, sample for other personnel.

10\) False high measurements have been identified when air sampling with
the Miran in atmospheres with significant concentrations of formalin,
isopropyl alcohol, ethyl alcohol, carbon dioxide, and water vapor
\[NIOSH\].

e\. Model Sampling Program. The model program includes quarterly leak
checks (with immediate repairs or adjustment), and quarterly breathing
zone sampling during typical OR, dental, or research procedures. The
leak check and breathing zone sampling should be done with a Miran. It
is advisable to also include passive dosimetry (for enflurane and
halothane, and perhaps nitrous oxide) to confirm breathing zone samples
on an annual basis.

8\. ***Employee Training.*** In 1977 NIOSH recommended initial (upon
assignment) and annual training of exposed employees. Although
anesthetic gases are regulated by the Food and Drug Administration, and
are thereby exempt from the requirements of the Hazard Communication
Standard; an Information and Training Program similar to the Hazard
Community Program is appropriate and consistent with NIOSH's
recommendation and JCAHO accreditation criteria. The training topics
should include: health hazards of WAG; exposure control strategies
(engineering and work practices); the purpose, benefits, results, and
schedule for air sampling; and the purpose of medical surveillance.

9\. ***Product Label and Work Site Posting.*** NIOSH recommends specific
warning label language for anesthetic gases to appear on the product and
posted where exposure is likely. They are much less comprehensive than
the label requirements of Hazard Communication Standard from which these
gases and vapors are exempt.

10\. ***Medical Surveillance.*** NIOSH recommends employers collect
medical histories with emphasis on the outcome of pregnancies (for
exposed women and wives of exposed men) and exposure histories for
exposed male and female employees. The following is extracted from the
NIOSH Standard: Medical surveillance, as outlined below, shall be made
available to all employees subject to occupational exposure to waste
anesthetic gases.

a Comprehensive preplacement medical and occupational histories shall be
obtained and maintained in the employees' medical records with special
attention given to the outcome of pregnancies of the employee or spouse;
and to the hepatic, renal, and hematopoietic systems which may be
affected by agents used as anesthetic gases. This information should be
updated at least yearly and at any other time considered appropriate by
the responsible physician.

b Preplacement and annual physical examinations of employees exposed to
anesthetic gases are recommended and, when performed, the results shall
be maintained in the employees' permanent medical records.

c\) Employees shall be advised of the potential undesirable effects of
exposure to waste anesthetic gases; such as spontaneous abortions,
congenital abnormalities in their children, and effects on the liver and
kidneys.

d\) Any abnormal outcome of the pregnancies of employees or of the
spouses of employees exposed to anesthetic gases shall be documented as
part of the employees' medical records, and the records shall be
maintained for the period of employment plus 20 years \[5 CFR 293.511(b)
requires 30 year retention\].

11\. ***Recordkeeping.*** Although NIOSH recommends keeping records of
air sampling, leak tests and medical surveillance for at least 20 years,
Federal Regulation requires them to be "maintained for the duration of
employment; plus 30 years, or for as long as the Official Personnel
Folder is maintained, whichever is longer.\"

a\. The same Federal Regulation requires relevant exposure records to be
kept in the medical records of exposed employees. Therefore, the reports
of quarterly equipment leak tests and breathing zone air sampling should
be copied and put in the medical records. In addition, it may be wise to
post these reports where employees are likely to see them.

b\. Training records, kept by each service, should include training
topics, dates and names of attendees.

12\. ***References.***

13\. ***Review/Rescission Date:***

(NAME)

Medical Center Director

Attachment

Permissible Levels of Exposure

Attachment

**Permissible Levels of Exposure to Anesthetic Gases**

**Proposed by Various Authorities**

*(Expressed in PPM)*

  -------------------- ----------------- ----------------- ---------------
  **Gas/Vapor**        **NIOSH**         **ACGIH**         **OSHA**

  -------------------- ----------------- ----------------- ---------------

+-----------------+-----------------+-----------------+---------------+
| Nitrous Oxide   | 25              | 50              | **\--**       |
|                 |                 |                 |               |
|                 | TWA for the     | TWA for 8 hrs.  |               |
|                 |                 | (Proposed)      |               |
|                 | Admin. Period   |                 |               |
+-----------------+-----------------+-----------------+---------------+
|                 |                 |                 |               |
+-----------------+-----------------+-----------------+---------------+
| Enflurance      | 2               | 75              | **\--**       |
|                 |                 |                 |               |
|                 | TWA for the     | TWA for 8 hrs.  |               |
|                 |                 |                 |               |
|                 | Admin. Period   |                 |               |
|                 | but not more    |                 |               |
|                 | than 1 hour.    |                 |               |
+-----------------+-----------------+-----------------+---------------+
|                 |                 |                 |               |
+-----------------+-----------------+-----------------+---------------+
| Halothane       | 2               | 50              | **\--**       |
|                 |                 |                 |               |
|                 | TWA for the     | TWA for 8 hrs.  |               |
|                 |                 |                 |               |
|                 | Admin. Period   |                 |               |
|                 | but not 1 hour. |                 |               |
+-----------------+-----------------+-----------------+---------------+
|                 |                 |                 |               |
+-----------------+-----------------+-----------------+---------------+
| Methoxyflurane  | 2               | **\--**         | **\--**       |
|                 |                 |                 |               |
|                 | TWA for the     |                 |               |
|                 |                 |                 |               |
|                 | Admin. Period   |                 |               |
|                 | but not more    |                 |               |
|                 | than 1 hour.    |                 |               |
+-----------------+-----------------+-----------------+---------------+
|                 |                 |                 |               |
+-----------------+-----------------+-----------------+---------------+
| Fluoroxene      | 2               | **\--**         | **\--**       |
|                 |                 |                 |               |
|                 | TWA for the     |                 |               |
|                 |                 |                 |               |
|                 | Admin. Period   |                 |               |
|                 | but not more    |                 |               |
|                 | than 1 hour.    |                 |               |
+-----------------+-----------------+-----------------+---------------+