Science Magazine  [Printer-friendly version]
June 15, 2006

NEW NANO-HEADACHE?

[Rachel's introduction: "A study of ultrafine particles of titanium
dioxide (TiO2) -- used in manufacturing, personal care and food
products, and as drug carriers -- indicates that even low
concentrations can produce harmful 'free radicals' in brain cells.
The findings underscore the need to learn more about how such tiny
particles interact with living tissues, the researchers say." Heeding
early warnings is an essential part of precautionary action.]

Hundreds of tons of engineered, microscopic particles enter the
environment every year, yet little is known of their biological
effects. Now, a study of ultrafine particles of titanium dioxide
(TiO2)--used in manufacturing, personal care and food products, and as
drug carriers--indicates that even low concentrations can produce
harmful "free radicals" in brain cells. The findings underscore the
need to learn more about how such tiny particles interact with living
tissues, the researchers say.

Previous studies have revealed that many nontoxic materials become
harmful at particle sizes of less than 100 nanometers. Specifically,
they can trigger the production of biologically reactive, oxygen-
containing molecules such as free radicals. In addition, some types of
particulate matter can enter the brain once they get into the
bloodstream. Little is known about the biological effects of TiO2, but
its widespread use and distribution means that humans and other
animals could be widely exposed.

To investigate the biological effects of TiO2, Bellina Veronesi, a
neurotoxicologist with the U.S. Environmental Protection Agency in
Research Triangle Park, North Carolina, and her colleagues exposed
mouse microglia--cells that protect the brain from invaders such as
viruses and foreign chemicals--to a solution containing minute
concentrations of TiO2. The microglia engulfed the particles and
released bursts of reactive oxygen molecules for 2 hours. This didn't
damage the microglia, but Veronesi says prolonged exposure to these
compounds can damage neurons. In fact, a similar mechanism is thought
to underlie some cardiovascular and neurodegenerative diseases,
including Parkinson's and Alzheimer's, the researchers note in their
report, published online 7 June in Environmental Science & Technology.

Environmental toxicologist Gunter Oberdorster of the University of
Rochester in New York says the research is a "good proof of
principle," but without further studies it would be premature to
conclude that TiO2 damages the brain. "The general message is that we
should take these results seriously and be very careful with
nanoparticles," he says.

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