Environmental Engineering Reference
In-Depth Information
as well as maternal VOC exposures during pregnancy are responsible for
increased risks of childhood leukemia. A significant increase in the risk of
childhood leukemia has been associated with paternal exposure to chlori-
nated solvents, methylethyl-ketone, spray paint, dyes and pigments, and
cutting oils. Infant VOC exposures or maternal exposures during pregnancy
may result from passive transport on clothing or body surfaces from the work
environment. As such, this reflects a “toxics brought home” phenomenon.
G. Indoor air chemistry
The dose-response relationship with “lost” VOCs and symptom prevalence
and an increase in HCHO levels suggest that health complaints in buildings
may be associated with exposures to new VOCs/aldehydes that are pro-
duced as a consequence of chemical reactions between airborne substances,
most notably VOCs.
There is increasing evidence that chemical reactions between ozone (O
3
)
and unsaturated hydrocarbons, such as d-limonene,
-terpene,
styrene, isoprene, etc., at levels commonly found in indoor air can produce
aldehydes that may affect air quality and human health. This may be asso-
ciated with reaction pathways involving hydroxyl (OH
-
) or nitrate (NO
3
)
radicals produced as a result of O
3
-initiated reactions.
Simple aldehydes such as HCHO, hexanal, nononal, and decanal, and
aromatic aldehydes such as benzaldehyde and tolualdehyde may be pro-
duced by such reactions. Other reaction products may include one or more
carbonyls, or a carbonyl with a double bond (e.g., 2-nonenal). Reactions
involving O
3
, isoprene, and OH
-
can result in the production of methacrolein
(CH
2
=C(CH
2
)CHO). Isoprene is emitted by plants and humans. Ozone reac-
tions with building furnishings such as carpeting have been observed to
produce measurable levels of 2-nonenal,
n
-nonenal, and C
1
-C
3
and C
6
-C
8
aldehydes.
Aldehydes produced by indoor chemical reactions also participate in
other chemical reactions. Aldehyde reactions with NO
3
radicals can produce
peroxy nitrates. The formation of peroxyacyl nitrate (PAN) begins with the
reaction of either NO
3
or OH
-
with acetaldehyde to form the acetyl radical
(CH
3
CO), which reacts with nitrogen dioxide (NO
2
) to form PAN
(CH
3
C(O)NO
2
). Hydroxyl radical reactions with propionaldehyde and ben-
zaldehyde produce peroxy propionyl nitrate (PPN) and peroxy benzoyl
nitrate (PBN), respectively.
Peroxyacyl nitrate, PPN, and PBN are all potent eye irritants, causing
symptoms at relatively low concentrations (circa 20 ppbv). Aldehydes pro-
duced as a result of indoor chemical reactions have lower odor thresholds
and may cause more sensory irritation than their precursors. Odor thresholds
are reported as 1.9 pptv for
cis
-2-nonenal and
trans
-6-nonenal, 17 pptv for
8-nonenal, and 24 pptv for
trans
-3-nonenal and
cis
-3-nonenal.
Indoor chemistry involving production of aldehydes, and aldehydes as
reactants, has only recently emerged as a potential explanation for IAQ
α
-pinene,
α
