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Methylene Chloride: Regulatory,
Health and Safety Facts
The Occupational Safety and Health Administration
(OSHA) has promulgated a standard that lowers the limit
on employee exposure to methylene chloride (dichloromethane)
to 25 part per million (ppm), a 20-fold decrease from
the 500 ppm limit set 25 years ago.
Why Is Methylene Chloride A Concern?
Methylene chloride is a widely used non-flammable
industrial solvent. When the body metabolizes methylene
chloride, it can form toxic formaldehyde and carbon
monoxide. Methylene chloride does not have good warning
properties. Many people are unable to detect the odor
of methylene chloride until vapor concentrations are
as much as 300 ppm [12 times greater than the 8-hour
time-weighted average (TWA) permissible exposure limit
(PEL) of 25 ppm]. Also, olfactory senses can become
fatigued, further reducing ability to detect methylene
chloride by odor.
OSHA considers methylene chloride to be a suspected
occupational carcinogen. Experimental studies have confirmed
that chronic long-term exposure causes cancer in laboratory
animals, while short-term exposure to high levels of
methylene chloride can cause dizziness, decreased attention
span, headaches, a lack of coordination, and irritation
of the skin, eyes and mucous membranes.
Exposure to methylene chloride occurs mainly through
inhaling its vapors. Additional routes of exposure are
through skin absorption or by ingestion. Methylene chloride
can be absorbed through the skin if personal protective
equipment is not worn or if the solvent gets on the
body or clothes. Employees can also swallow small amounts
of methylene chloride if they do not wash their hands
before eating, or if they eat in contaminated work areas.
Where Is Methylene Chloride Found?
Employees are typically exposed to the solvent during
construction, remodeling, degreasing work, paint and
furniture stripping, and use of ink solvents. Affected
industries include construction, upholstery, printing,
polyurethane foam manufacturing, and furniture refinishing.
How Does It Affect Employees?
According to OSHA, the methylene chloride revised
standard will prevent an estimated 31 cancer, cardiovascular
and central nervous system deaths per year. The Consumer
Product Safety Commission requires health-warning labels
on methylene chloride-based consumer products. EPA is
driving industry for maximum achievable control technology
(MACT) on methylene chloride, along with a host of other
compounds considered hazardous air pollutants under
the Clean Air Act Amendments of 1990.
What Does The OSHA Standard Require?
OSHA’s Methylene Chloride Standard (29 CFR 1910.1052)
applies to all employment in general industry, shipyards
and construction. It reduces the permissible exposure
limit (PEL) from 500 to 25 ppm as an eight-hour time-weighted
average (TWA). In addition, the short-term exposure
limit (STEL) is reduced from 1000 to 125 ppm. The standard
includes an Action Level (AL) of 12.5 ppm. The AL was
established as an exposure indicator and triggers a
set of provisions for exposure control. These provisions
include personal protective equipment, employee exposure
monitoring, training, medical surveillance, hazard communication,
regulated areas and recordkeeping. The standard requires
the following:
- Employers must determine whether methylene chloride
is used in the workplace.
- If methylene chloride is present and product substitution
is not possible, employers are required to perform
personal air sampling to determine employee exposure
and develop programs to ensure that the 8-hour TWA
and 15-minute STEL are not exceeded.
- If it is determined that employees are exposed
over the AL, TWA or STEL, initial medical surveillance,
periodic monitoring, and training programs for exposed
employees must be implemented.
- Lastly, engineering controls to effectively reduce
employee exposures must be provided.
Specific monitoring requirements and dates by which
employers have to implement these provisions are dependent
on the exposure scenario and the size of the facility.
What Should Employers Do For Their Employees?
In many facilities, simply altering work practices
and housekeeping procedures can greatly reduce exposure
to methylene chloride. However, the following recommendations
may reduce employee exposure to methylene chloride:
- Keep vapors contained. Contain vapors by keeping
doors to mixing/storage areas closed at all times
and covering dip and reservoir tanks when not in use.
To help capture methylene chloride vapors, proper
engineering controls, such as local exhaust ventilation,
are in place and functioning properly. In addition,
properly label methylene chloride containers to indicate
their contents, hazards, and proper use, storage and
disposal.
- Personal protective equipment. Employees should
wear appropriate gloves, aprons, and boots or shoe
covers to prevent methylene chloride from getting
on the skin or clothes. A face shield and goggles
are recommended for eye and face protection.
- Supplied-air respirators. If engineering controls
and work practices do not reduce methylene chloride
exposures to an acceptable level, employees must wear
supplied-air respirators (SAR). SARs are used in place
of cartridge respirators because methylene chloride
readily passes through cartridges, leaving respirator
wearers unprotected. While SARs can reduce methylene
chloride exposure concentrations to below OSHA limits,
it is important for employers to bear in mind that
respirators are not a substitute for good engineering
and administrative controls.
- Minimize the chance of spills and leaks that develop.
Follow procedures for detecting methylene chloride
leaks from process equipment, holding tanks and spill
control devices. Frequently inspect process equipment,
holding tanks and spill control devices for cracks,
loose parts and other possible sources of leaks.
XL Environmental • Risk Control Division •
520 Eagleview Boulevard, PO Box 636, Exton, PA 19341
• Phone: 800-327-1414 • Fax: 610-458-7285
• xlenvironmental.com
XL Environmental is a division of XL Specialty Insurance
Company.
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