Environmental Engineering Reference
In-Depth Information
the neurotoxic tricresyl phosphates (TCPs) was conirmed in the bulk oils and in the
volatiles, but trimethyl propane phosphate (TMPP) was not found in these experi-
ments. The absence of TCPs in cabin air possibly resulted from localized condensa-
tion in the ventilation ducts and ilters, and in the air-conditioning packs. The
possibility of the release of pyrolysis products from localized condensates could not
be ruled out, particularly when cabin heat demand is high (van Netten and Leung
2001
).
The quality of cabin air associated with a contamination of cabin air supply con-
taminated with the degradation products of oils and luids was addressed in a UK
study (CAA
2004
). In this study, two contaminated cabin air supply ducts were
examined and analyzed for the presence of chemical constituents and degradation
products of engine oils, hydraulic luids, and lubricants. The inner surface of the
ducts was found to be coated with black carbonaceous particulate material, which
could be easily dislodged by gentle pressure. Therefore, the material could poten-
tially have become airborne and emitted as solid aerosols in the cabin and light deck
environment. The material was found to contain aluminum, silicon, sulfur, and phos-
phorus. Gas chromatographic-mass spectrometric analyses of air samples from the
contaminated ducts disclosed the presence of short-chain irritants (carboxylic acids,
aldehydes, and ketones). Analyses of the solvent extracts of the black duct material
further indicated the presence of high molecular weight compounds such as TCPs,
TMPP, trimethylolpropane phosphates, and associated esters, suggesting that these
compounds may have been tightly bound to the black material. These indings sug-
gest that not all of the chemicals adsorbed onto the material could be desorbed by
airlow (for further discussion of this event also see: Chaturvedi
2009, 2010a
).
The absence of the solvent extractable chemicals in duct airlow does not mean
that those chemicals present in the airlow are the only chemicals responsible for
toxicological effects, because other compounds adsorbed onto the duct's material
may be released as particulates and may contribute to the toxicity. Since the parti-
cles can easily be dislodged, they could easily enter the aircraft interior when the
temperature in the cabin is high, and/or when physical disturbances occur during
lights (e.g., takeoffs and landings). If the cabin and light deck occupants inhale
those particles, they would be exposed to any chemical present in the duct airlow,
including airborne particulates emitted from solid deposits. Such exposure is likely
to cause adverse effects, including ocular and upper respiratory irritation, nausea,
vomiting, dizziness, and pulmonary toxicity. Because some of the neurotoxicants
involved have delayed effects, some toxic symptoms may not appear in exposed
individuals for some time.
Although the toxicity of the substances in the black carbonaceous particulate
material found in the ducts is described and discussed with suficient relevant scien-
tiic references in the UK study (CAA
2004
), the toxicity of this solid carbonaceous
material, as a whole entity, is not given in detail. The chemicals comprising the
carbonaceous material may not necessarily be individually toxic at the concentra-
tions found, but if they are mixed together at those concentrations, the mixture may
be highly toxic (Eaton and Klaassen
1996
). Because of the dificulty of dealing with
complex chemical mixtures, including pyrolysis products, the best approach to
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