miércoles, 6 de febrero de 2013

CDC - NIOSH Science Blog – Dangers of Bathtub Refinishing

CDC - NIOSH Science Blog – Dangers of Bathtub Refinishing

Dangers of Bathtub Refinishing

Categories: Chemicals, Exposure
Nitrile-gloved hands refinishing a bathtubAt least 14 workers have died since 2000 as a result of using stripping agents containing methylene chloride during bathtub refinishing.  Many stripping products (including those that may also be available to consumers) contain high percentages of methylene chloride. Methylene chloride is extremely dangerous when not used properly.  Alternative products and processes exist for bathtub refinishing.  Products containing methylene chloride should be avoided when possible.  Earlier this week NIOSH and OSHA released a joint Hazard Alert titled Methylene Chloride Hazards for Bathtub Refinishers
Bathtub refinishing is the process of restoring the surface of an old bathtub to improve the bathtub’s appearance and repair surface damage.  It is a less costly alternative to replacing a bathtub; however, the process often involves the use of hazardous chemicals including methylene chloride, acids, and isocyanates.
Methylene chloride, a chlorinated solvent, is a volatile, colorless liquid with a sweet-smelling odor. It is often referred to as dichloromethane and has many industrial uses, such as paint stripping, metal cleaning, and degreasing. Workers are exposed to methylene chloride by breathing it in and by absorbing it through their skin. Methylene chloride cannot be smelled until the level in the air is higher than OSHA’s permissible exposure limits (PELs).  So, once workers can smell methylene chloride they are already being overexposed.  However, the human body can quickly become desensitized to the smell and a worker may be overexposed even if he or she can no longer smell it.
Using methylene chloride products in a bathroom is extremely dangerous as bathrooms are often small, enclosed spaces with little or no ventilation. Workers often spray or pour a bathtub stripping product into the basin of the bathtub and then brush the product onto the tub surface. Since methylene chloride is a volatile organic compound that will evaporate faster when sprayed, brushed, or poured, the chemical vapors can quickly build up in small spaces. Moreover, because methylene chloride evaporates quickly (it has a high vapor pressure), vapors can collect in the bottom of a bathtub and in the worker’s breathing zone when working in the bathtub. This situation creates dangerously high concentrations of methylene chloride and even replaces the breathable air. Exposure to as little as six ounces of methylene chloride-based material has been enough to cause death. 
In February 2012, a worker using a product containing methylene chloride to refinish a bathtub was found dead, slumped over a bathtub in an unventilated bathroom.
In September 2011, a worker using a product containing methylene chloride to strip the glaze from a bathtub collapsed in the bathtub and later died.

Health Effects

When methylene chloride enters the human body, it affects brain function, such as concentration. At high enough levels, it can stop breathing. Methylene chloride exposure may cause dizziness, fatigue, headaches, nausea, a “feeling of intoxication,” and eye, nose, and throat irritation.  Prolonged skin contact may cause irritation and even chemical burns.
The specific effects of methylene chloride exposure will vary depending on several factors, such as the amount of methylene chloride the worker is exposed to, how long the exposure lasts, and whether the worker has a higher susceptibility (for example, having a preexisting heart condition).  In workers with heart disease, an increase in carbon monoxide may lead to early onset heart attacks and arrhythmias (irregular heartbeats). Heart attacks may occur even before any other symptoms of methylene chloride exposure occur.  As exposure increases so do the health effects, with a potential for suffocation, loss of consciousness, coma, and sudden death.  Long-term exposure may cause cancer in humans. Animal studies have shown that exposure to methylene chloride may lead to liver and lung cancer, as well as tumors in the breast and salivary glands. Lowering exposures, even below the PEL, is considered to be good industrial hygiene practice.  Like many cancer-causing agents, any level of exposure, even concentrations below applicable occupational exposure limits, may pose a residual cancer risk.

Protecting Workers

  • Avoid use of methylene chloride or minimize the amount of methylene chloride used at each site. Keep in mind that alternative products and other stripping agents may pose additional risks.
  • Avoid or minimize spraying methylene chloride.
  • If methylene chloride is used, ensure that the room is adequately ventilated during the entire refinishing process.  Bathroom fans or open windows do NOT provide adequate ventilation.
  • Provide local exhaust ventilation (LEV) and fresh makeup air to exhaust vapors released from the stripping agents in the bathtub. Specifically, typical mobile LEV units have a fan, flexible ductwork, and a hood near the tub that exhausts hazardous vapors to the outdoors.
  • Follow all applicable OSHA standards, including the Methylene Chloride standard (29 CFR 1910.1052External Web Site Icon), as well as other applicable safety and health standards and codes during stripping.
  • Use a qualified occupational safety and health specialist to assist in the design and installation of local exhaust ventilation (LEV) to effectively control vapors to below applicable PELs.
  • Follow good housekeeping measures, including spill and leak control and appropriate personal hygiene practices (such as making skin washing areas available to workers).
  • Use long-handled tools (e.g., scrapers, brushes) to avoid leaning into the bathtub.
  • Leave the room immediately after applying the methylene chloride-based stripping agent to limit exposure to methylene chloride vapors. Use full-face air-supplied respirators, protective gloves, and other appropriate personal protective equipment (PPE) that is resistant to methylene chloride during the entire refinishing process
Consult the OSHA/NIOSH Hazard Alert for specific information regarding engineering controls, exposure levels and air monitoring, personal protective equipment, worker training and medical surveillance. 
We would appreciate your assistance in circulating the information in this blog and the Hazard Alert to those involved in bathtub refinishing.  While NIOSH research and prevention efforts typically focus on workers, worker representatives and employers, the readers of this blog may be able to help us reach the ‘do-it-yourself’ community who can  face the same risks.  We also welcome your input on the prevention practices mentioned above.   

Ronald M. Hall, CDR, USPHS, MS, CIH, CSP

CDR Hall is the Deputy Branch Chief of the Engineering and Physical Hazards Branch in the NIOSH Division of Applied Research and Technology  

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