Zinc oxide found toxic - study

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By Jimmy Downs

Saturday Nov 24, 2012 (foodconsumer.org) -- Health conscious consumers may have noticed this.  Dietary supplements store vitacost.com has stopped using titanium dioxide, a type of nanoparticles in dietary supplements because many consumers do not like to see it in their dietary supplements.  But it is common that many food and dietary supplements manufacturers use nanoparticles like titanium dioxide, silicon dioxide and zinc oxide in foods and dietary supplements.

Titanium dioxide is not the only nanomaterial that is toxic.  Because the toxicity of nanoparticles is largely caused by the particles' sizes, the toxicity observed with  titanium dioxide can also be applicable to other nanoparticles like zinc oxide and silicon dioxide.

A study recently published in Nanotoxicology shows that zinc oxide (ZnO) nanoparticles may be even more toxic than titanium dioxide (TiO(2)).

I. De Angelis at Department of Environment and Primary Prevention, Istituto Superiore di Sanità in Roma , Italy and colleagues compared the toxicity induced by zinc oxide and titanium dioxide nanoparticles on Caco-2 cells and found zinc oxide was more toxic than titanium dioxide.

Titanium dioxide when inhaled is recognized as a cancer causing agent by the World Health Organization.  But nanoparticles ingested can travel to various organs and they may cause the damage to various types of tissue/cells.  Previous studies show nanoparticle can enter cells and disrupt DNA, leading potentially to mutagenesis and carcinogenesis.

In the current study, the researchers found only zinc oxide produced significant cytotoxicity, compared with titanium dioxide.  Both titanium dioxide nanoparticles increased intracellular amounts of reactive oxygen species (ROS) six hours after treatment.

However, only zinc oxide nanoparticles were found to increase reactive oxygen species and induced IL-8 release both after six and 24 hours.

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