WAC 296-62-07475
Appendix B. Medical Surveillance for
Methylene Chloride
I. Primary Route of Entry Inhalation.
II. Toxicology.
Methylene Chloride (MC) is primarily an inhalation hazard. The principal acute hazardous effects are the depressant
action on the central nervous system, possible cardiac
toxicity and possible liver toxicity. The range of CNS
effects are from decreased eye/hand coordination and decreased
performance in vigilance tasks to narcosis and even death of
individuals exposed at very high doses. Cardiac toxicity is
due to the metabolism of MC to carbon monoxide, and the
effects of carbon monoxide on heart tissue. Carbon monoxide
displaces oxygen in the blood, decreases the oxygen available
to heart tissue, increasing the risk of damage to the heart,
which may result in heart attacks in susceptible individuals. Susceptible individuals include persons with heart disease and
those with risk factors for heart disease. Elevated liver
enzymes and irritation to the respiratory passages and eyes
have also been reported for both humans and experimental
animals exposed to MC vapors.
MC is metabolized to carbon monoxide and carbon dioxide
via two separate pathways. Through the first pathway, MC is
metabolized to carbon monoxide as an end-product via the P-450
mixed function oxidase pathway located in the microsomal
fraction of the cell. This biotransformation of MC to carbon
monoxide occurs through the process of microsomal oxidative
dechlorination which takes place primarily in the liver. The
amount of conversion to carbon monoxide is significant as
measured by the concentration of carboxyhemoglobin, up to 12%
measured in the blood following occupational exposure of up to
610 ppm. Through the second pathway, MC is metabolized to
carbon dioxide as an end product (with formaldehyde and formic
acid as metabolic intermediates) via the glutathione dependent
enzyme found in the cytosolic fraction of the liver cell. Metabolites along this pathway are believed to be associated
with the carcinogenic activity of MC.
MC has been tested for carcinogenicity in several
laboratory rodents. These rodent studies indicate that there
is clear evidence that MC is carcinogenic to male and female
mice and female rats. Based on epidemiologic studies, OSHA
has concluded that there is suggestive evidence of increased
cancer risk in MC-related worker populations. The
epidemiological evidence is consistent with the finding of
excess cancer in the experimental animal studies. NIOSH
regards MC as a potential occupational carcinogen and the
International Agency for Research Cancer (IARC) classifies MC
as an animal carcinogen. OSHA considers MC as a suspected
human carcinogen.
III. Medical Signs and Symptoms of Acute Exposure Skin
exposure to liquid MC may cause irritation or skin burns. Liquid MC can also be irritating to the eyes. MC is also
absorbed through the skin and may contribute to the MC
exposure by inhalation. At high concentrations in air, MC may
cause nausea, vomiting, light-headedness, numbness of the
extremities, changes in blood enzyme levels, and breathing
problems, leading to bronchitis and pulmonary edema,
unconsciousness and even death.
At lower concentrations in air, MC may cause irritation
to the skin, eye, and respiratory tract and occasionally
headache and nausea. Perhaps the greatest problem from
exposure to low concentrations of MC is the CNS effects on
coordination and alertness that may cause unsafe operations of
machinery and equipment, leading to self-injury or accidents. Low levels and short duration exposures do not seem to produce
permanent disability, but chronic exposures to MC have been
demonstrated to produce liver toxicity in animals, and
therefore, the evidence is suggestive for liver toxicity in
humans after chronic exposure. Chronic exposure to MC may
also cause cancer.
IV. Surveillance and Preventive Considerations
As discussed above, MC is classified as a suspect or potential
human carcinogen. It is a central nervous system (CNS)
depressant and a skin, eye and respiratory tract irritant. At
extremely high concentrations, MC has caused liver damage in
animals. MC principally affects the CNS, where it acts as a
narcotic. The observation of the symptoms characteristic of
CNS depression, along with a physical examination, provides
the best detection of early neurological disorders. Since
exposure to MC also increases the carboxyhemoglobin level in
the blood, ambient carbon monoxide levels would have an
additive effect on that carboxyhemoglobin level. Based on
such information, a periodic post- shift carboxyhemoglobin
test as an index of the presence of carbon monoxide in the
blood is recommended, but not required, for medical
surveillance.
Based on the animal evidence and three epidemiologic
studies previously mentioned, OSHA concludes that MC is a
suspect human carcinogen. The medical surveillance program is
designed to observe exposed workers on a regular basis. While
the medical surveillance program cannot detect MC-induced
cancer at a preneoplastic stage, OSHA anticipates that, as in
the past, early detection and treatments of cancers leading to
enhanced survival rates will continue to evolve.
A. Medical and Occupational History:
The medical and occupational work history plays an
important role in the initial evaluation of workers exposed to
MC. It is therefore extremely important for the examining
physician or other licensed health care professional to
evaluate the MC-exposed worker carefully and completely and to
focus the examination on MC's potentially associated health
hazards. The medical evaluation must include an annual
detailed work and medical history with special emphasis on
cardiac history and neurological symptoms.
An important goal of the medical history is to elicit
information from the worker regarding potential signs or
symptoms associated with increased levels of carboxyhemoglobin
due to the presence of carbon monoxide in the blood. Physicians or other licensed health care professionals should
ensure that the smoking history of all MC exposed employees is
known. Exposure to MC may cause a significant increase in
carboxyhemoglobin level in all exposed persons. However,
smokers as well as workers with anemia or heart disease and
those concurrently exposed to carbon monoxide are at
especially high risk of toxic effects because of an already
reduced oxygen carrying capacity of the blood.
A comprehensive or interim medical and work history
should also include occurrence of headache, dizziness,
fatigue, chest pain, shortness of breath, pain in the limbs,
and irritation of the skin and eyes. In addition, it is
important for the physician or other licensed health care
professional to become familiar with the operating conditions
in which exposure to MC is likely to occur. The physician or
other licensed health care professional also must become
familiar with the signs and symptoms that may indicate that a
worker is receiving otherwise unrecognized and exceptionally
high exposure levels of MC.
An example of a medical and work history that would
satisfy the requirement for a comprehensive or interim work
history is represented by the following:
The following is a list of recommended questions and
issues for the self-administered questionnaire for methylene
chloride exposure.
Questionnaire For Methylene Chloride Exposure
1. Have you ever worked with methylene chloride,
dichloromethane, methylene dichloride, or CH2Cl2 (all are
different names for the same chemical)? Please list which on
the occupational history form if you have not already.
2. If you have worked in any of the following industries
and have not listed them on the occupational history form,
please do so.
3. If you have not listed hobbies or household projects
on the occupational history form, especially furniture
refinishing, spray painting, or paint stripping, please do so.
III. Medical History
A. General
1. Do you consider yourself to be in good health? If no,
state reason(s).
2. Do you or have you ever had:
a. Persistent thirst
b. Frequent urination (three times or more at night)
c. Dermatitis or irritated skin
d. Nonhealing wounds
3. What prescription or nonprescription medications do
you take, and for what reasons?
4. Are you allergic to any medications, and what type of
reaction do you have?
B. Respiratory
1. Do you have or have you ever had any chest illnesses
or diseases? Explain.
2. Do you have or have you ever had any of the following:
a. Asthma
b. Wheezing
c. Shortness of breath
3. Have you ever had an abnormal chest X ray? If so,
when, where, and what were the findings?
4. Have you ever had difficulty using a respirator or
breathing apparatus? Explain.
5. Do any chest or lung diseases run in your family?
Explain.
6. Have you ever smoked cigarettes, cigars, or a pipe?
Age started:
7. Do you now smoke?
8. If you have stopped smoking completely, how old were
you when you stopped?
9. On the average of the entire time you smoked, how many
packs of cigarettes, cigars, or bowls of tobacco did you smoke
per day?
C. Cardiovascular
1. Have you ever been diagnosed with any of the
following:
Which of the following apply to you now or did apply to
you at some time in the past, even if the problem is
controlled by medication? Please explain any yes answers
(i.e., when problem was diagnosed, length of time on
medication).
a. High cholesterol or triglyceride level
b. Hypertension (high blood pressure)
c. Diabetes
d. Family history of heart attack, stroke, or blocked
arteries
2. Have you ever had chest pain? If so, answer the next
five questions.
a. What was the quality of the pain (i.e., crushing,
stabbing, squeezing)?
b. Did the pain go anywhere (i.e., into jaw, left arm)?
c. What brought the pain out?
d. How long did it last?
e. What made the pain go away?
3. Have you ever had heart disease, a heart attack,
stroke, aneurysm, or blocked arteries anywhere in your body? Explain (when, treatment).
4. Have you ever had bypass surgery for blocked arteries
in your heart or anywhere else? Explain.
5. Have you ever had any other procedures done to open up
a blocked artery (balloon angioplasty, carotid endarterectomy,
clot-dissolving drug)?
6. Do you have or have you ever had (explain each):
a. Heart murmur
b. Irregular heartbeat
c. Shortness of breath while lying flat
d. Congestive heart failure
e. Ankle swelling
f. Recurrent pain anywhere below the waist while walking
7. Have you ever had an electrocardiogram (EKG)? When?
8. Have you ever had an abnormal EKG? If so, when,
where, and what were the findings?
9. Do any heart diseases, high blood pressure, diabetes,
high cholesterol, or high triglycerides run in your family?
Explain.
3. Do you have or have you ever had (explain each):
a. Hepatitis (infectious, autoimmune, drug-induced, or
chemical)
b. Jaundice
c. Elevated liver enzymes or elevated bilirubin
d. Liver disease or cancer
E. Central Nervous System
1. Do you or have you ever had (explain each):
a. Headache
b. Dizziness
c. Fainting
d. Loss of consciousness
e. Garbled speech
f. Lack of balance
g. Mental/psychiatric illness
h. Forgetfulness
F. Hematologic
1. Do you have, or have you ever had (explain each):
a. Anemia
b. Sickle cell disease or trait
c. Glucose-6-phosphate dehydrogenase deficiency
d. Bleeding tendency disorder
2. If not already mentioned previously, have you ever had
a reaction to sulfa drugs or to drugs used to prevent or treat
malaria? What was the drug? Describe the reaction.
B. Physical Examination
The complete physical examination, when coupled with the
medical and occupational history, assists the physician or
other licensed health care professional in detecting
preexisting conditions that might place the employee at
increased risk, and establishes a baseline for future health
monitoring. These examinations should include:
1. Clinical impressions of the nervous system,
cardiovascular function and pulmonary function, with
additional tests conducted where indicated or determined by
the examining physician or other licensed health care
professional to be necessary.
2. An evaluation of the advisability of the worker using
a respirator, because the use of certain respirators places an
additional burden on the cardiopulmonary system. It is
necessary for the attending physician or other licensed health
care professional to evaluate the cardiopulmonary function of
these workers, in order to inform the employer in a written
medical opinion of the worker's ability or fitness to work in
an area requiring the use of certain types of respiratory
protective equipment. The presence of facial hair or scars
that might interfere with the worker's ability to wear certain
types of respirators should also be noted during the
examination and in the written medical opinion.
Because of the importance of lung function to workers
required to wear certain types of respirators to protect
themselves from MC exposure, these workers must receive an
assessment of pulmonary function before they begin to wear a
negative pressure respirator and at least annually thereafter.
The recommended pulmonary function tests include measurement
of the employee's forced vital capacity (FVC), forced
expiratory volume at one second (FEV1), as well as calculation
of the ratios of FEV1 to FVC, and the ratios of measured FVC
and measured FEV1 to expected respective values corrected for
variation due to age, sex, race, and height. Pulmonary
function evaluation must be conducted by a physician or other
licensed health care professional experienced in pulmonary
function tests.
The following is a summary of the elements of a physical
exam which would fulfill the requirements under the MC
standard:
Physical Exam
I. Skin and appendages
1. Irritated or broken skin 2. Jaundice 3. Clubbing
cyanosis, edema 4. Capillary refill time 5. Pallor
II. Head
1. Facial deformities 2. Scars 3. Hair growth
III. Eyes
1. Scleral icterus 2. Corneal arcus 3. Pupillary size and
response 4. Fundoscopic exam
IV. Chest
1. Standard exam
V. Heart
1. Standard exam 2. Jugular vein distension 3. Peripheral
pulses
VI. Abdomen
1. Liver span
VII. Nervous System
1. Complete standard neurologic exam
VIII. Laboratory
1. Hemoglobin and hematocrit 2. Alanine aminotransferase
(ALT, SGPT) 3. Post-shift carboxyhemoglobin
I. Studies
1. Pulmonary function testing
2. Electrocardiogram
An evaluation of the oxygen carrying capacity of the
blood of employees (for example by measured red blood cell
volume) is considered useful, especially for workers acutely
exposed to MC. It is also recommended, but not required, that
end of shift carboxyhemoglobin levels be determined
periodically, and any level above 3% for nonsmokers and above
10% for smokers should prompt an investigation of the worker
and his workplace. This test is recommended because MC is
metabolized to CO, which combines strongly with hemoglobin,
resulting in a reduced capacity of the blood to transport
oxygen in the body. This is of particular concern for
cigarette smokers because they already have a diminished
hemoglobin capacity due to the presence of CO in cigarette
smoke.
C. Additional Examinations and Referrals
1. Examination by a Specialist
When a worker examination reveals unexplained symptoms or
signs (i.e. in the physical examination or in the laboratory
tests), follow-up medical examinations are necessary to assure
that MC exposure is not adversely affecting the worker's
health. When the examining physician or other licensed health
care professional finds it necessary, additional tests should
be included to determine the nature of the medical problem and
the underlying cause. Where relevant, the worker should be
sent to a specialist for further testing and treatment as
deemed necessary. The final rule requires additional
investigations to be covered and it also permits physicians or
other licensed health care professionals to add appropriate or
necessary tests to improve the diagnosis of disease should
such tests become available in the future.
2. Emergencies
The examination of workers exposed to MC in an emergency
should be directed at the organ systems most likely to be
affected. If the worker has received a severe acute exposure,
hospitalization may be required to assure proper medical
intervention. It is not possible to precisely define
"severe," but the physician or other licensed health care
professional's judgment should not merely rest on
hospitalization. If the worker has suffered significant
conjunctival, oral, or nasal irritation, respiratory distress,
or discomfort, the physician or other licensed health care
professional should instigate appropriate follow-up
procedures. These include attention to the eyes, lungs and
the neurological system. The frequency of follow-up
examinations should be determined by the attending physician
or other licensed health care professional. This testing
permits the early identification essential to proper medical
management of such workers.
D. Employer Obligations
The employer is required to provide the responsible physician
or other licensed health care professional and any specialists
involved in a diagnosis with the following information: a
copy of the MC standard including relevant appendices, a
description of the affected employee's duties as they relate
to his or her exposure to MC; an estimate of the employee's
exposure including duration (e.g., 15hr/wk, three 8-hour
shifts/wk, full time); a description of any personal
protective equipment used by the employee, including
respirators; and the results of any previous medical
determinations for the affected employee related to MC
exposure to the extent that this information is within the
employer's control.
E. Physicians' or Other Licensed Health Care
Professionals' Obligations
The standard requires the employer to ensure that the
physician or other licensed health care professional provides
a written statement to the employee and the employer. This
statement should contain the physician's or licensed health
care professional's opinion as to whether the employee has any
medical condition placing him or her at increased risk of
impaired health from exposure to MC or use of respirators, as
appropriate. The physician or other licensed health care
professional should also state his or her opinion regarding
any restrictions that should be placed on the employee's
exposure to MC or upon the use of protective clothing or
equipment such as respirators. If the employee wears a
respirator as a result of his or her exposure to MC, the
physician or other licensed health care professional's opinion
should also contain a statement regarding the suitability of
the employee to wear the type of respirator assigned.
Furthermore, the employee should be informed by the
physician or other licensed health care professional about the
cancer risk of MC and about risk factors for heart disease,
and the potential for exacerbation of underlying heart disease
by exposure to MC through its metabolism to carbon monoxide. Finally, the physician or other licensed health care
professional should inform the employer that the employee has
been told the results of the medical examination and of any
medical conditions which require further explanation or
treatment. This written opinion must not contain any
information on specific findings or diagnosis unrelated to
employee's occupational exposures.
The purpose in requiring the examining physician or other
licensed health care professional to supply the employer with
a written opinion is to provide the employer with a medical
basis to assist the employer in placing employees initially,
in assuring that their health is not being impaired by
exposure to MC, and to assess the employee's ability to use
any required protective equipment.
[Statutory Authority: RCW 49.17.040, [49.17].050 and[49.17].060
. 97-18-062, § 296-62-07475, filed 9/2/97,
effective 12/1/97.]