Caution! MC is dangerous! See the articles below before you use MC.  It's
not worth the little extra elbow grease of sanding. On 12/29/03  Antonio
Minichilli, suffered a heart attack while using a methylene chloride
stripping solution in Massachusetts.


Jabe Luttrell


See the OSHA article:

. Part Number:1910
. Part Title:Occupational Safety and Health Standards
. Subpart:Z
. Subpart Title:Toxic and Hazardous Substances
. Standard Number:1910.1052 App B
. Title: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.

See the article from EPA:

METHYLENE CHLORIDE
Methylene chloride, known also as methylene dichloride and dichloromethane,
is a colorless, volatile liquid with an ether-like odor. It is commonly
found
in septic tank cleaners, paint and varnish removers, degreasers, pesticides,
aerosols, and Christmas bubble lights.  Methylene chloride irritates skin
that
comes in contact. When inhaled, it mimics carbon monoxide toxicity. Memory
loss
and liver and kidney damage are reported with chronic exposure. Methylene
chloride
is a known animal carcinogen and a suspected human carcinogen. When heated,
methylene chloride emits a highly toxic phosgene gas (nerve gas). The use of
products containing methylene chloride by people with heart conditions has
resulted
in fatal heart attacks.