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Is it time to act?
... However, this approach may be limited by differences in the concentration of various isomers of tricresyl phosphate in engine oils. Concern also exists about other components of pyrolyzed engine oils [Anderson, 2014;Michaelis, 2014]. Nonetheless, fully validated biomarkers of exposure to tricresyl phosphate and other components of pyrolyzed engine oil and hydraulic fluids that could be used in future epidemiologic studies may allow investigators to more accurately evaluate the association of neurodegenerative diseases with exposure to tricresyl phosphate or other exposures from air contamination events among aircrew. ...
Background:
Concern exists about the potential chronic neurological effects among aircrew of exposure to chemical contaminants from engine oil in aircraft cabin air. We evaluated mortality from neurodegenerative diseases among 11,311 former US flight attendants.
Methods:
Vital status was ascertained through 2007, and life table analyses were conducted to obtain standardized mortality ratios (SMRs).
Results:
Amyotrophic lateral sclerosis (ALS) mortality was over twice as high in the cohort as in the US general population, based on nine observed ALS deaths. There was no clear pattern in risk when SMRs for ALS were stratified by exposure duration. Mortality from other neurodegenerative diseases was not elevated.
Conclusions:
Our findings are limited due to small numbers of observed deaths and reliance on mortality data, but suggest that flight attendants may have an increased risk of ALS. Additional research is needed. Am. J. Ind. Med. Published 2016. This article is a U.S. Government work and is in the public domain in the USA.
This thesis examines the six-decade use of unfiltered aircraft bleed air, taken from jet engines
to supply breathing air in the flight decks and passenger cabins of commercial and military
transport aircraft. During this time, numerous flight safety issues and adverse effects from
exposure to contaminated bleed air have been reported. The research undertaken in this
thesis examined previous investigations into these matters and the consequences of using
bleed air on flight safety and crew and passenger health. This research examined: (a) health
issues reported by aircrew as a consequence of exposure to contaminated bleed air whilst
flying by way of several descriptive surveys; (b) various aviation air monitoring studies
previously undertaken were reviewed to assess the knowledge base of the chemicals present
during contaminated air events; (c) air sampling data were evaluated for their usefulness in
determining any potential adverse health effects; (d) a review was undertaken of the
frequency of contaminated bleed air events; (e) a review was undertaken of some of the
information known by the aviation industry and others about contaminated bleed air. Analysis
of the evidence that bleed air, contaminated by synthetic jet engine oils and hydraulic fluids,
is a regular and normal occurrence and far more common than previously accepted and is a
consequence of the current bleed air system design. There are significant short and longterm
health effects being reported as a direct result of documented exposure events that
validate claims of adverse health effects in exposed individuals. The thesis argues that the
precautionary principle, occupational health and safety guidelines and aviation regulations
are being ignored by the aviation industry, who continue to claim that cabin air is safe. The
systemic misuse of available data is widespread, secondary to commercial objectives, and
places passenger and crew health and flight safety at serious risk. The thesis concludes that
the use of bleed air on commercial aircraft with no form of contaminated air detection or
filtration system present should be discontinued. The risk to health and flight safety is no
longer acceptable: http://handle.unsw.edu.au/1959.4/50342
A broad overview of the subject is presented, covering all salient aspects including the technical history, a discussion of the compounds involved in the contamination, the frequency of occurrence, a survey of attempts to measure the contamination, safety considerations, health considerations, and possible technical solutions to the problem of contamination.
Pyrolysed engine oil sometimes contaminates the ventilation supply air on commercial aircraft, exposing crew members and passengers to oil fumes. Aircraft occupants have documented both acute and chronic symptoms, largely neurological and respiratory, during and after such exposures. However, aviation regulators do not require airlines to either clean or monitor the ventilation supply air for oil-based contaminants and there is no central reporting system for either crew members or passengers. This paper presents the debate over whether existing evidence of ill health and compromised flight safety warrants engineering and administrative controls to protect crew members in particular. It also describes the regulatory frameworks for aviation workplace safety/health and air supply system design/maintenance in the US. The authors recommend a combination of engineering and administrative controls to prevent exposure to oil fumes on aircraft.
Taking aircraft out of service for even one day to correct fume-in-cabin
events can cost the industry roughly $630 million per year in lost
revenue. The quantitative correlation study investigated quantitative
relationships between measured concentrations of contaminants in bleed
air and probability of odor detectability. Data were collected from 94
aircraft engine and auxiliary power unit (APU) bleed air tests from an
archival data set between 1997 and 2011, and no relationships were
found. Pearson correlation was followed by regression analysis for
individual contaminants. Significant relationships of concentrations of
compounds in bleed air to probability of odor detectability were found
(p<0.05), as well as between compound concentration and probability
of sensory irritancy detectability. Study results may be useful to
establish early warning levels. Predictive trend monitoring, a method to
identify potential pending failure modes within a mechanical system, may
influence scheduled down-time for maintenance as a planned event, rather
than repair after a mechanical failure and thereby reduce operational
costs associated with odor-in-cabin events. Twenty compounds
(independent variables) were found statistically significant as related
to probability of odor detectability (dependent variable 1). Seventeen
compounds (independent variables) were found statistically significant
as related to probability of sensory irritancy detectability (dependent
variable 2). Additional research was recommended to further investigate
relationships between concentrations of contaminants and probability of
odor detectability or probability of sensory irritancy detectability for
all turbine oil brands. Further research on implementation of predictive
trend monitoring may be warranted to demonstrate how the monitoring
process might be applied to in-flight application.
Individuals aboard jet aircraft may be exposed to potentially toxic triaryl organophosphate anti-wear lubricant additives (TAPs) that are converted by cytochromes P450 into toxic metabolites. Consequences of exposure could be reduced by using less toxic TAPs. Our goal was to determine whether an in vitro assay for inhibition of butyrylcholinesterase (BChE) by bioactivated TAPs would be predictive of inhibition of serine active-site enzymes in vivo. The in vitro assay involved TAP bioactivation with liver microsomes and NADPH, followed by incubation with human BChE and measurement of BChE activity. Of 19 TAPs tested, tert-butylated isomers produced the least BChE inhibition. To determine the relevance of these results in vivo, mice were exposed to Durad 125 (D125; a commercial mixture of TAP esters) or to TAPs demonstrating low or no BChE inhibition when assayed in vitro. Inhibition of BChE by bioactivated TAPs in vitro correlated well with inhibition of other serine active-site enzymes in vivo, with the exception of brain acetylcholinesterase and neuropathy target esterase (NTE), which were not inhibited by any TAP tested following single exposures. A recombinant catalytic domain of NTE (rNEST) exhibited classical kinetic properties of NTE. The metabolite of tri-(o-cresyl) phosphate (ToCP), 2-(o-cresyl)-4H-1,3,2-benzodioxaphosphoran-2-one (CBDP), inhibited rNEST in vitro, but with an IC(50) value almost 6-times higher than for inhibition of BChE. Physiologically-relevant concentrations of the flavonoid, naringenin, dramatically reduced D125 bioconversion in vitro. The in vitro assay should provide a valuable tool for prescreening candidate TAP anti-wear additives, identifying safer additives and reducing the number of animals required for in vivo toxicity testing.
Three decades ago, cabin air quality was seemingly not an issue in commercial aviation and the incidence of disease through air borne vectors or toxic fumes was uncommon among passengers and crew. However, it is claimed that modern day jet airliners generally carry the threat of disease through the ventilator systems of these aircraft which are designed for optimum efficiency, leaving them exposed to lapses in the recycling of clean air and blocking fumes from engine exhausts of the jets from entering the inhabited parts of the aircraft. It has been claimed that aerotoxic fumes are most common in the cockpit, and that the technical crew are the most susceptible to the aerotoxic syndrome.