Aerospace Toxicology Overview: Aerial Application and Cabin Air Quality - Reviews of Environmental Contamination and Toxicology - page 27

in aircraft cabins is further demonstrated to be a factor for the mucosal irritation
experienced by travelers and light attendants (Lindgren and Norback 2002 ; Nagda
and Hodgson 2001 ; Uva Ade 2002 ), and tobacco-smoking onboard may contribute
to signiicant pollution from respirable dust (Lindgren and Norback 2002 ; Lindgren
et al. 2000 ; Wieslander et al. 2000 ). Lindgren et al. ( 2007 ) investigated the inluence
of air humidiication during intercontinental lights on the perception of cabin air
quality among airline crew. These authors concluded that relative humidity can be
slightly increased by using a ceramic evaporation humidiier, without showing any
measurable increase of microorganisms (Lindgren et al. 2007 ). Their evaluation of
the optimum balance between fresh air supply and humidity, involving 7-h expo-
sures in a simulated aircraft cabin, indicated that increasing the relative humidity to
28% by reducing outside low to 1.4 L/s per person did not reduce the intensity of
the symptoms that are typical of the aircraft cabin environment. However, this
adjustment intensiied complaints of headache, dizziness, and claustrophobia that
resulted from the increased level of contaminants (Strom-Tejsen et al. 2007 ).
The contribution of secondhand tobacco smoke to aircraft cabin air pollution was
assessed for light attendants, and compared to results from the general population;
results indicated that ventilation systems massively failed to control secondhand
smoke air pollution in cabins (Repace 2004 ). However, smoking is now prohibited
by most airlines, and the pollution caused by smoking is no longer a relevant issue.
The authors of another study emphasized that the relative air humidity of cabin air
was very low on intercontinental lights, and particle levels were high on lights with
passive smoking (Lindgren and Norback 2005 ). These indings suggested the need
for improving cabin air quality by better controlling cabin temperature, air humidi-
ication, and air iltration (HEPA ilters), and having a suficient air exchange rate on
all aircraft types.

3.3 Possible Toxicants in Space Vehicle Cabin Air

Astronauts work, sleep, and live in space vehicles (Patterson and Rayman 1996 ), and
there is a strong potential for a slow and insidious buildup of toxic substances - such
as refrigerants, CO, hydrogen cyanide (HCN), CO 2 , ammonia, and other organic
compounds - in the space-vehicle cabin atmosphere. Also, high concentrations of
toxic substances may be rapidly released from onboard ires. The deaths of the three
Apollo 1 crew members in the 1967 ire accident resulted from their exposure to
toxic combustion products (US National Aeronautics and Space Administration
1967 ). Moreover, the involvement of ire has been acknowledged in the 23 February
1997 accident on the Mir aerospace station (Welch and Navias 1997 ), wherein the
ire burned for approximately 90 s and the crew was exposed to heavy smoke for
5-7 min.
In addition to the combustion gases (e.g., CO and HCN) originating from ire
(Chaturvedi 1995 ; Chaturvedi and Sanders 1995, 1996 ; Sanders and Chaturvedi
1994 ), sources of toxic substances in cabin air can result from off-gassing of space