Is Bromothane™ Ozone-Safe?

Well, this is an interesting question and the answer is not yet resolved. But in short, the Bromothane™ solvents are slight -- VERY slight -- ozone-depleting solvents.

• Bromothane Is Not Listed in the Montreal Protocol • 

You see, in the 1980's a group of experts were tabulating all of the world's ozone-depleting solvents and classified them into two groups: the "Class I" ozone-depleters were the really bad actors, and the "Class II" materials had an impact but to a much, much lesser degree. These lists became the heart of the Montreal Protocol, the first international treaty to protect the ozone layer.

But the Bromothane™ solvents and other nPB-based cleaners never made it on to the list. This is because nobody was using nPB as a solvent. It sort of just fell through the cracks.

So while it may sound like some people are splitting hairs, it is technically correct to say that nPB is not listed as an ozone-depleting solvent ("O.D.S.") and it is not a "Class II" ozone-depleting material.

But the more precise truth is to report that while nPB is not a Class II O.D.S., it does have a slight ozone-depletion potential. The EPA rates the ODP of nPB to be similar to that of HCFC-141b. According to the EPA:

"At the latitude of the US, nPB has an ozone depletion potential (ODP) of 0.013 to 0.018. At tropical latitudes, nPB has an ODP of 0.071 to 0.100, close to that of methyl chloroform and HCFC-141b. EPA is basing its proposed decision on the ODP in the US. nPB may contribute to smog and is regulated as a volatile organic compound.

 "Although nPB is not currently regulated as a hazardous waste, EPA recommends that you dispose of it as any other halogenated solvents to avoid impacts on aquatic life (The LC50, the concentration at which 50% of test animals die, is 67 mg/L for fathead minnows). nPB has a low tendency to concentrate in living organisms with a bioconcentration factor of 23. It is moderately mobile in soil with a Koc value of 330. nPB tends to volatilize and breaks down easily in water, with a hydrolysis half-life of 26 days."

Source: http://www.epa.gov/ozone/snap/solvents/2007nPBRegsQA.html

The INIST-CNRS in France reports:

"A number of the compounds proposed as replacements for substances controlled under the Montreal Protocol have extremely short atmospheric lifetimes, on the order of days to a few months. An important example is n-propyl bromide (also referred to as 1-bromopropane, CH2BrCH2CH3 or simplified as 1-C3H7Br or nPB). This compound, useful as a solvent, has an atmospheric lifetime of less than 20 days due to its reaction with hydroxyl.

 

"Because nPB contains bromine, any amount reaching the stratosphere has the potential to affect concentrations of stratospheric ozone. The definition of Ozone Depletion Potentials (ODP) needs to be modified for such short-lived compounds to account for the location and timing of emissions. It is not adequate to treat these chemicals as if they were uniformly emitted at all latitudes and longitudes as normally done for longer-lived gases. Thus, for short-lived compounds, policymakers will need a table of ODP values instead of the single value generally provided in past studies.

 

"The degradation of nPB produces a significant quantity of bromoacetone which increases the amount of bromine transported to the stratosphere due to nPB. However, much of that effect is not due to bromoacetone itself, but instead to inorganic bromine which is produced from tropospheric oxidation of nPB, bromoacetone, and other degradation products and is transported above the dry and wet deposition processes of the model. The MOZART2 nPB [model] indicates a minimal correction of the two-dimensional results in order to derive our final results: an nPB chemical lifetime of 19 days and an Ozone Depletion Potential range of 0.033 to 0.040 for assumed global emissions over landmasses, 19 days and 0.021 to 0.028, respectively, for assumed emissions in the industrialized regions of the Northern Hemisphere, and 9 days and 0.087 to 0.105, respectively, for assumed emission in tropical Southeast Asia."

And here's some more good info:

The Montreal Protocol specifies the phase-out of ozone-depleting substances. The general phase-out schedules were defined years ago. This effort was based on research by the British in the 1960s which detected changes in the ozone layer in the Antarctic. It took almost another decade to figure out the cause, and it was Mario Molina, a lowly post-graduate researcher in California, who first realized that man-made chemicals such as CFCs were damaging the ozone layer. Fortunately his mentor, Sherwood Rowland, took his findings seriously and the pair went on to publish an article in 1974 in which they spelled out the dangers of continued use of CFCs. In the 1980s, in response to the depletion of the ozone layer, more than 100 nations worked together on a treaty called the Montreal Protocol. This treaty set the rules for eliminating ozone-depleting substances around the globe.   For more details about the ozone depletion issue, global warming and VOCs, you can visit the United Nations web site, the Earthwatch web site, the GreenPeace web site, and a new location in the UK with some very good info without the polemics found on GreenPeace.)

So here's the punchline today: the Bromothane™ solvents are the ideal replacements for the listed ozone-depleting solvents in precision cleaning applications. They are "drop-in" replacements for old-style solvents such as CFC-113, 1,1,1-trichloroethane, HCFC-141b and HCFC-225, as well as high-global-warming solvents such as perfluorocarbons (PFCs).

Updated: Feb. 4 2009
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