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QUALITATIVE AND QUANTITATIVE DETERMINATION OF POLY-AROMATIC HYDROCARBONS (PAH) IN FOG OIL OBSCURANT SMOKE

The constituents of most concern are PAHs due to their potential carcinogenicity and other harmful properties. The presence of these compounds has been deemed unacceptable by the US Army, which issued a fog oil specification in 1986 calling for PAH-free fog oil.

To test if the fog oil currently used by the US Army meets this specification, a sample of fog oil was obtained and analyzed in our laboratory. The oil has been subjected to severe hydro treatment to make it compatible with the 1986 specifications.

A qualitative and quantitative assessment of the PAH content of the fog oil was made both before and after aerosolization with a laboratory generator. The laboratory smoke generator is operated at the same temperature regimes used in the Army's smoke generators. The assessment of PAH content was facilitated by an extraction with dimethyl sulfoxide (DMSO) and a back extraction from DMSO.

These steps provided extracts which are largely devoid of aliphatic background, which otherwise severely limits the use of gas chromatography-mass spectrometry (GC-MS) for chemical characterization. The results showed that fog oil currently in use contains high concentrations (parts per thousands to percent levels) of PAHs.

The most prevalent species are alkylated naphthalenes and napthlated phenanthrenes. However, low concentrations of higher PAHs are also present in the oil. The results also showed that the concentration of PAHs remain unaffected by the aerosolization process.

Key words: obscurant smoke, PAH, fog oil, aerosolization