MicroCare markets the Bromothane™ family of solvent cleaners. The key ingredient in the Bromothane™ family is the brominated molecule known as nPB (also called n-Propyl Bromide, 1-Bromopropane or CAS # 106-94-6). This nonflammable fluid is a powerful cleaner with a low global warming potential. It is used as an alternative to CFC-113, methyl chloroform, hydrochlorofluorocarbons (HCFCs) and perfluorocarbons (PFCs) in many critical cleaning, drying, carrier fluid and other high-value specialty uses where reliability is paramount.

Based upon toxicological research, MicroCare agrees with ACGIH that the Acceptable Exposure Limit (AEL) is 0.1 parts per million (ppm), using the 8- time weighted average (TWA) methodology. This means Bromothane™ products (or ANY product containing nPB) cannot be safely used in an uncontrolled environment, such as an aerosol dispenser. The fluids can be used safely in high-quality, tight, modern vapor degreasing equipment.

Despite this research, many customers are skeptical of the safety and toxicity claims made by any company. Let’s take a look at the details. (And, just for the record, the following comments are equally applicable to any brand or source of

The Hazards Associated with nPB

In simple terms, the hazards associated with n-propyl bromide can be viewed with regards to short and long term exposure. Like other solvents, short-term over-exposure can lead to skin irritation and dizziness. Early on, the U.S. National Toxicology Program has recommended a No Observable Adverse Effect Level (NOAEL) for nPB of 100 ppm, which, with a sensible ten-fold safety factor, led MicroCare and other companies to recommend a 10 ppm exposure limit.


But now there is new research which suggests there are significant toxicity worries. From a long-term viewpoint, tests in animals have shown long-term overexposure to nPB may lead to multiple adverse affects in the body likely including fertility problems for both males and females. Governmental agencies in the E.U., the U.S., Canada and elsewhere around the world have been moving to restrict its use. Recent health studies have found nPB damages the nervous system, alters human DNA, impairs fertility and there is a risk of cancer.

Based on these reports, the European Chemicals Agency (ECHA) listed nPB as a ‘Substance of Very High Concern’ in December 2012. The government of Ontario, Canada also has become concerned about the long-term toxicity of nPB and in July 2017 the Ministry of Labour enacted new worker-safety rules which restrict the deployment of this widely-used chemical. Over in the US, several government agencies recommended 10 ppm as the proper exposure limit. Separately, California adopted a 5 ppm limit and an independent safety agency, the American Conference of Governmental Industrial Hygienists (ACGIH), lowered their recommended exposure rating to just 0.1 ppm. At these exposure levels, there is no way to safely use nPB in an aerosol package, but it can be used safely in a modern, tight vapor degreaser.

There are other companies who dispute these toxicity ratings, and claim safety factors to be 10 or 100 times higher. MicroCare believes these claims are bogus and self-serving. MicroCare suggests the savvy engineer study the real research and evaluate the manner in which the solvent will be used to determine if and when nPB can be used safely in your factory.

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