Summary Report: NA/317

PERFLUOROBUTANE

3M Australia Pty Ltd of 2-74 Dunheved Circuit, St Marys, NSW 2760 has applied for an Assessment Certificate for the importation of the chemical, perfluorobutane, under section 23 of the Act. Perfluorobutane is intended to be used as a clean extinguishing agent for fire and explosion protection in certain applications involving public safety and national security that require a total flooding agent. The estimated quantity of perfluorobutane to be imported into Australia is 1-10 tonnes/year for the first 5 years.

Physical and Chemical Properties

Perfluorobutane is a colourless gas at ambient temperature and pressure with the following physico-chemical properties: boiling point, -2^oC; melting point, -128^oC; gas density, 9.935 kg/m³ at 25^oC and 1 atm; vapour pressure, 3.26 atm; partition co-efficient (n-octanol/water) log P_ow, > 3.93.

The water solubility is estimated to be 1.5 mg/L (at 1 atm perfluorobutane) by measurement of headspace pressure. The submission also includes a QSAR estimate of more than 100 mg/L. The solubility of the gas is estimated to be approximately 320 mg/L using Irmann's equation. The low measured solubility may reflect difficulties in retaining perfluorobutane in solution: the study reports a very low vapour to water partition coefficient of 0.00034 (nearly 3000 times as much perfluorobutane will exist in the vapour phase for equal volumes of vapour and water).

Perfluorobutane has no functionalities normally considered to be hydrolysable, significant sorption to soil is not expected. It is a gas and it does not contain any readily dissociable groups.

Assessment of Toxicological Data

The acute inhalational toxicity of perfluorobutane in rats was low. Oral, dermal and irritation studies were not provided as these tests are not applicable to gases. Nevertheless, ophthalmoscopic observations performed during the 90 day chronic inhalation study did not provide evidence of eye irritation. During the inhalation studies the entire body of the rat was exposed to the notified substance. Perfluorobutane did not cause cardiac sensitisation. Rats repeatedly exposed to perfluorobutane for up to 90 days via the inhalational route showed only marginal effects on some white blood cell parameters. These effects were not consistent between the sexes. Perfluorobutane did not induce gene mutation in Salmonella typhimurium or Escherichia coli. There was no increased frequency of chromosomal aberrations in vitro in Chinese hamster lung cells exposed to perfluorobutane. Based on the studies presented perfluorobutane is not genotoxic.

Perfluorobutane would not be classified as hazardous according to Worksafe Australia's Approved Criteria for Classifying Hazardous Substances in relation to acute lethal effects (inhalation) or severe effects after repeated or prolonged exposure (inhalational route).

Assessment of Public and Occupational Exposure and Health and Safety Effects

Perfluorobutane is expected to exhibit low acute and chronic inhalational toxicity and is not likely to be genotoxic. It is also not likely to exhibit cardiac sensitisation.

Exposure to perfluorobutane during repacking into smaller gas bottles and during fire system installation is expected to be minimal given the stringent procedures employed and the systems being designed to minimise unintended release.

Exposure to perfluorobutane is likely to be significant when there is a fire and total flooding occurs. As fires are expected to be infrequent events, exposure to perfluorobutane is expected to be low and the gas would be expected to disperse relatively rapidly after release.

The risk of adverse occupational and public health effects resulting from transport, storage, use and disposal of perfluorobutane is expected to be low given the low hazard and likely low or infrequent exposure. However, there is an occupational health risk of frostbite from exposure to sudden release of the compressed gas and there is a public health risk of asphyxiation if total flooding occurs in an enclosed area with limited means of egress.

Assessment of Environmental Fate

Given its high volatility, any perfluorobutane released to the environment will partition rapidly and almost entirely to the atmosphere. Perfluorobutane is resistant to biodegradation, but will not persist in water because of its volatility and will not bioconcentrate. The main degradation pathway in the environment is photochemical degradation upon exposure to short wavelength radiation (< 200 nm) in the upper stratosphere. No intermediate breakdown products are expected to enter the biosphere as the stratosphere is a high energy environment where breakdown products will not persist. The estimated atmospheric lifetime is at least 2600 years.

Assessment of Environmental Effects

No specific data were provided, with the omission justified by the lack of significant aquatic exposure to this volatile and sparingly soluble gas. Perfluorocarbons are stable substances that do not exhibit significant biological activity. Testing on perfluorohexane indicated an absence of toxicity to fish.

Volatile halocarbons can affect the atmosphere. The principal concern is ozone depletion. Perfluorobutane contains neither chlorine nor bromine, and thus will not act as a source of ozone depleting halogen radicals in the stratosphere.

As with other halocarbons, emissions of perfluorobutane will increase the global warming potential of the atmosphere. The notifer estimates a global warming potential of 5500 relative to carbon dioxide over a 100 year time horizon, intermediate between those for CFC-11 (3400) and CFC-12 (7100). However, projected import volumes are relatively low and not expected to increase significantly as the high cost of the agent and the product stewardship measures in place are expected to restrict its use to specialised applications.

Assessment of Environmental Hazard

Perfluorobutane is not expected to exert a direct effect on living organisms as it belongs to a class of compound, the perfluorocarbons, with negligible biological activity. The high volatility should ensure minimal exposure of aquatic and terrestrial compartments, and therefore minimal hazard to organisms inhabiting them.

Hazard to the atmosphere will be reduced when perfluorobutane replaces the strongly ozone depleting Halon 1301, as the replacement refrigerant has negligible potential to destroy ozone. However, the replacement retains significant global warming potential and is expected to persist in the atmosphere for millennia.

In order to minimise environmental exposure, 3M Australia operates a product stewardship program that includes assisting customers in determining whether perfluorobutane is the appropriate agent for a particular application, and returning all unused and recovered agent to the US for recycling.

Recommendations

To minimise occupational and environmental exposure to perfluorobutane the following guidelines and precautions should be observed:

• If engineering controls and work practices are insufficient to reduce exposure to perfluorobutane to a safe level, then personal protective devices which conform to and are used in accordance with Australian or Australian/New Zealand Standards (AS or AS/NZS) for respiratory protection (AS/NZS 1715, AS/NZS 1716) , eye protection (AS 1336, AS/NZS 1337), impermeable gloves (AS 2161) and protective clothing (AS 2919) should be worn;
• Emissions of perfluorobutane should be minimised by only using the agent in accordance with the Code of Practice for the Design, Installation, Inspection and Testing of Gaseous Fire Suppression Systems Utilising Ozone Depleting Substances (this requirement should appear on the Material Safety Data Sheet). Perfluorobutane should only be used where no alternative is technically feasible due to performance or safety requirements.
• Perfluorobutane should be recovered from maintenance and decommissioning of systems that contain it for recycling, storage or destruction; and
• The Material Safety Data Sheet (MSDS) should be updated when a plasma arc facility becomes available in Australia to indicate that this is the preferred method of disposal where recovery for recycling is not practical.
• A copy of the MSDS should be easily accessible to employees.

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