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Methylene chloride exposure risk and mitigation

March 2, 2012

Is the US Occupational Safety & Health Administration (OSHA) has released a report on dangers of methylene chloride in bathtub refinishing.  There are many dangers of (and risk mitigation tools for) methylene chloride exposure, maybe now is the time to review them.methylene chloride - stripping and coating risk

The news  Investigators have identified more than a dozen deaths in the last 12 years associated with the use of methylene chloride in bathtub refinishing.  (It's likely that there are more than this, such as unreported and contract workers, etc.)  Each death occurred in a residential bathroom with inadequate ventilation. The new report is based on an investigation driven by OSHA, the National Institute for Occupational Safety and Health (NIOSH) and Michigan's Fatality Assessment and Control Evaluation (FACE) program assessing the hazards of using methylene chloride-based stripping products in bathtub refinishing.

Private and industry risk  Six of the ten products in the investigation were marketed for use in the aircraft industry, the rest for use on wood, metal, glass, and masonry.

An article in Federal Computer Week discusses how the Environmental Protection Agency (EPA) uses MSDS Vault software to help protect workers from hazardous methylene chloride exposure scenarios.  But not every agency or business has such risk management measures in place.

Ten different products were associated with the deaths.  The percentage of methylene chloride in the products ranged from 60% to 100%.  None of the product labels mentioned bathtub refinishing. 

Manufacturers, trade organizations, public health agencies and worker safety agencies should clearly communicate the extreme hazard posed by using methylene chloride–based stripping products in bathtub refinishing. If workers use methylene chloride-based products, OSHA's Methylene Chloride standard (29 CFR 1910.1052) requires employers to protect and train workers exposed to these hazards. 

Methylene chloride vapor has been previously recognized as potentially fatal to furniture strippers and factory workers, but the threat in the bathtup stripping context is new. Cal OSHA published a clear, useful document on the subject.

The public risk  Methylene chloride risk extends to the general public.  Industrious types may decide to do their own bathtub refinishing. A review of the OSHA IMIS system, the Internet, and hardware stores, found 42 stripping products, 26 (62%) of which are readily available on the Internet or at local hardware stores. Many of these stripping products contain 60%–90% methylene chloride.

Many Internet sites promote do-it-yourself bathtub stripping, and no state or federal restrictions exist on the use of methylene chloride stripping agents.  Widespread availability of such products and their effectiveness puts both professional bathtub refinishers and do-it-yourselfers at risk.

Short-term exposures to high levels can cause headaches, fatigue, dizziness and lack of coordination. Methylene chloride is metabolized in the body to carbon monoxide, which may lead to irregular heart rhythms, heart attacks and sudden death.

Alert workers about methylene chloride  Worker safety agencies, public health agencies, methylene chloride–based stripper manufacturers, and trade organizations should communicate the extreme hazards of using methylene chloride–based stripping products in bathtub refinishing to employers, workers, and consumers.  Employers choosing to use methylene chloride–based stripping products must comply with OSHA's standard to limit methylene chloride exposures to safe levels.

Case study  In March 2010, the co-owner of a Michigan-based bathtub refinishing company, aged 52 years, was refinishing a bathtub in an apartment bathroom that was approximately 5 feet by 8 feet (1.5 meters by 2.4 meters) with an 8-foot (2.4-meter) ceiling. He was using an aircraft paint stripper product that contained 60%–100% methylene chloride. The bathroom ceiling had a 50 cubic feet per minute (1.4 cubic meters per minute) ventilation fan; however, the fan was off. The man wore latex gloves and did not wear respiratory protection or use engineering controls (e.g., a local exhaust ventilation system) to vent the methylene chloride vapor.

Approximately 90 minutes after the man began working on the tub, he did not answer a call to his cellular telephone. An apartment maintenance man entered the apartment to look for the man and found him behind the closed bathroom door, unresponsive, and slumped over the tub. The maintenance man telephoned 911 and then a second maintenance man. The two maintenance men pulled the man off of the tub. The second maintenance man, a certified emergency medical technician, began cardiopulmonary resuscitation. When emergency responders arrived an estimated 2 minutes later, they moved the victim to another part of the apartment and continued resuscitation before transporting him to a local hospital. The man was declared dead at the hospital.

The decedent had a history of hyperlipidemia, and his autopsy revealed mild coronary atherosclerosis and mucus plugging of bronchi and bronchioles. His blood methylene chloride level at autopsy was 50 mg/L. All other toxicology test results from the autopsy, including COHb, were reported as negative. The death certificate listed the cause of death as "sudden cardiorespiratory arrest due to or as a consequence of inhalation of toxic fumes."  (source: OSHA)

Methylene chloride in bathtubs and beyond  To use products containing methylene chloride safely, work areas must be well-ventilated, and when levels of methylene chloride exceed exposure limits even after implementation of engineering and work practice controls, workers must use respiratory protective equipment, such as tight-fitting, full-face, supplied-air respirators. OSHA's standard for methylene chloride, which was promulgated in 1997, covers all occupational exposures to the chemical (e.g., general industry, shipyard employment, and construction). The standard mandates that air monitoring, medical surveillance, hazard communication, and personal protective equipment be in place where methylene chloride is used.

Methylene chloride is metabolized to formaldehyde and carbon monoxide and is categorized as a carcinogen.

Good Cal Osha document on the subject: http://www.cdph.ca.gov/programs/hesis/Documents/methylenechloride.pdf




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