LOS
ANGELES, Feb. 21 (Xinhua) -- Ozonolysis purifiers emit ozone at higher levels
with the goal of oxidizing volatile organic compounds in the air, but that
consequently can cause health problems as well, U.S. researchers said Wednesday.
High levels of airborne particles can aggravate
asthma and cardiovascular problems, and have been linked to high death and lung
cancer rates, said the researchers at the University of California in Irvine
(UCI).
Excess ozone can damage the lungs, causing chest
pain, coughing, shortness of breath and throat irritation, according to the
researchers.
They claimed that cleaning products containing
chemicals that produce a lemon smell can dirty the air when used with indoor air
purifiers that produce even a small amount of ozone.
Ozone from the purifiers react in the air with
unsaturated volatile organic compounds such as limonene -- a chemical added to
cleaning supplies that give them a lemon fragrance -- to create additional
microscopic particles, they said.
"The public needs to be aware that every air
purification approach has its limitation, and ionization air purifiers are no
exception," said Sergey Nizkorodov, an assistant professor of chemistry at UCI
and a co-author of the study.
"These air purifiers can not only elevate the level
of ozone, a formidable air pollutant in itself, but also increase the amount of
harmful particulate matter in indoor air," Nizkorodov said.
The research appeared online on Wednesday in
Environmental Science and Technology.
According to Nizkorodov, certain ionic purifiers emit
ozone as a byproduct of ionization that is used for charging airborne particles
and electrostatically attracting them to metal electrodes.
Nizkorodov and two of his students placed an
ozone-emitting air purifier in the middle of a sparsely furnished office, along
with a large fan to better mix the air.
At timed intervals, limonene vapor was injected in
the room, and samples were taken and analyzed for ozone and particulate matter
levels, Nizkorodov said.
The researchers tested two types of air purifiers, a
commercial ionic purifier that emits about 2 milligrams of ozone per hour, and
an ozonolysis purifier that emits about 100 milligrams of ozone per hour.
Continuous operation of the ionic purifier without
limonene resulted in a slight reduction in the average particle concentration,
while operation of the ozonolysis purifier resulted in no detectable effect on
the particle level.
However, when limonene was added, the particle
concentration shot up in both cases, on some occasions up to 100 times the
original level.
Adding limonene to the room when a purifier was not
operating made little change in the overall particle level, Nizkorodov said.
