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I strongly support the efforts of the CARB to regulate emissions of
ozone from indoor air cleaning devices.

At one level, it defies logic that we should invest such
remarkable effort as a society to control ozone in urban air (an
effort that is well justified, given the health effects evidence)
and at the same time allow sale of devices that generate
substantial levels of this same pollutant in indoor environments. 


Less well understood, but likely of comparable importance is that
ozone reacts with indoor materials to produce harmful byproducts. 
Among these are formaldehyde and ultrafine particles.  Product
yields are such that the reaction tradeoff is generally bad news
for human health.  

Consider, for example, formaldehyde.  Health-based guidelines are
about 50-100 ppb for ozone.  For formaldehyde, we are concerned
with concentrations that are at least an order of magnitude lower,
i.e. 2-10 ppb.  Ozone reactions on indoor surfaces might typically
produce 3 ppb of volatile byproducts, such as formaldehyde, for
every 10 ppb of ozone consumed.  An indoor concentration of 50 ppb
of ozone typically means that 100 ppb worth of ozone would also
have reacted on indoor surfaces, producing about 30 ppb of
volatile byproducts, including several ppb of formaldehyde.  The
best way to control the problem of exposure to ozone byproducts --
and growing evidence suggests that it is a real problem -- is to
limit or avoid introducing ozone into occupied spaces.

I have been involved in a related study recently, investigating
ozone in aircraft cabins and the health of passengers and crew. 
In one investigation, we exposed passengers (healthy young adult
women) to varying air quality conditions in a simulated cabin
during 4-h periods.  Ozone levels of 60-75 ppb were strongly
correlated with adverse symptoms typical of "sick-building
syndrome."  A research article focusing on the symptoms is
attached; it is "in press" in the Journal of Exposure Science and
Environmental Epidemiology (P Strom-Tejsen et al.).  Another
article that focuses on the reactive chemistry of ozone in the
cabin environment has just been published in Environmental Science
& Technology (CJ Weschler et al., Ozone-initiated chemistry in an
occupied simulated aircraft cabin, ES&T 41, 6177, 2007.)

Simply put, the existing health evidence about the adverse effects
of ozone and the emerging evidence about the adverse effects of
ozone byproducts combine to provide compelling arguments that
ozone should not be emitted in substantial quantities into indoor
air.  I know of no scientifically defensible countervailing
argument.