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The State of California recently issued a "hazard alert" following an occupationally-related death from methylene chloride poisoning. The worker was alone, using the solvent methylene chloride to strip paint on the inside of a semi-enclosed tank (http://www.cdph.ca.gov/programs/ohb-face/Documents/paintstripper.pdf). This is a task that should never be done without sufficient protections in place, which includes using a "buddy system" for safety watch. Though it's restricted in Europe, this chemical is still widely used industrially in the U.S. Methylene chloride is also commonplace is a number of consumer products available for use in the home. There is no buddy system for that.
Methylene chloride is a surprisingly common chemical solvent which also goes by the name dichloromethane. It is a simple molecule made up of one carbon atom linked to two atoms of chlorine and two of hydrogen. It is the chemical kissing cousin of chloroform (aka trichloromethane, with one more chlorine atom). Chloroform is a best known from its use as an early anesthetic drug, an application later abandoned because of toxicity. Methylene chloride acts similarly. The over-inhalation of its volatile fumes can rapidly lead to loss of consciousness and potentially fatal coma with depressed breathing.
Another complication of such chlorine-containing central nervous system depressants is their tendency to make the heart over-sensitized to "fright and flight" stimulation by the native adrenaline response. This can lead to deadly electrical arrhythmia, mimicking the effect of an acute heart attack. Stopping the heart and breathing is not unique to this chemical—a number of chlorine-containing solvents can act this way, some of which are also far more toxic to the liver (carbon tetrachloride, for example, which is basically methylene chloride with two additional chlorine atoms) and many of which are also suspect carcinogens based on animal studies. Methylene chloride, however, has one special attribute that sets it apart. In the human body, methylene chloride is broken down to yield carbon monoxide. Since it is efficiently created right on site, it is never out in the air for a household carbon monoxide detector alarm to detect.
All of this may be very nifty for some Agatha Christie wannabe plotting out the fiction of a body found in a bathroom with the door locked from the inside (was it a heart attack? a sudden coma? carbon monoxide poisoning?), yet the reality is not a mystery, but rather an avoidable tragedy. According to the California Department of Public Health, over the past decade at least 13 bathtub refinishers have died while using methylene chloride.
Reference: http://www.cdph.ca.gov/programs/hesis/Documents/MethyleneChlorideAlert.pdf)
Perhaps this is not surprising: in many ways, a bathroom at home may not be too different from the classic sort of confined space typically found in industry, like the semi-enclosed tank in which the other worker noted above recently died. Bathrooms are often small, poorly ventilated, and prone to trap fumes and vapors.
Methylene chloride has physical properties which promote its ability to be absorbed through the skin and vaporized into the air, but if that weren't enough, one of the ways in which it is marketed for consumer use is as a spray can aerosol. The U.S. National Institutes of Health National Library of Medicine identifies more than a score of various consumer products currently available that contain methylene chloride, including paint strippers, auto products, and various brands classified for home maintenance use. Some are made up of 80% or more of the solvent.
These products remain on the market because they have never been restricted by the U.S. Consumer Product Safety Commission (CPSC), which some time ago abandoned "rule-making" to address this, choosing instead to issue a "policy statement" on the topic. Their mainstay of advice is: "Use paint strippers and other products containing methylene chloride outdoors." CPSC policy-makers, realizing perhaps that carrying the bathtub to the backyard is not always feasible, also allow that, "If a product containing methylene chloride must be used indoors, even in a garage; open all windows and doors and use a fan to exhaust the air outside during application and drying." Forget Agatha Christie, with a watchdog agency as effective as the CPSC, this is fodder for a TV "docufiction" episode in the genre of 1000 Ways to Die.
