Nov 212011
 
Titanium dioxide nanofibers

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Clearly, more research is needed

 
Show of hands: who would like to see computers that are smaller and more powerful? Or a cancer therapy that precisely targets only cancer cells? Or foods with better nutritional value? Or packaging that keeps food fresher and bacteria free for longer?

Nanotechnology promises to do all this … and more!

Already in hundreds, if not thousands, of consumer products, nanomaterials provide UV protection in sunscreens and durability in automobile paints and surface coatings. In foods, they improve color, flavor and texture as well as enhance nutritional value.

Yet the health and environmental impact of these tiny particles is largely unknown.

Which begs the question: Have we become so mesmerized by the shiny gleam of nanotechnology that we have ignored safety, especially in our food?

Are they safe?

Questions of toxicity and the long-term effects of accumulation in the human body abound – especially when nanomaterials are introduced into the food we eat. Intentionally placed there or not, these tiny particles could have unexpected effects on our overall health as they pass through the digestive tract.

Take for example the food additive titanium dioxide (which is also used in sunscreens, cosmetics and toothpastes). In its non-nano form, this white substance has been approved for use in foods since 1966. It is what makes food such as cake icing “white.” It is also approved as a food contact substance, meaning it is deemed safe to incorporate into food packaging. The nano form of titanium dioxide is colorless making it ideal to use in clear plastic food wraps for UV protection. And because titanium dioxide has already been approved for food packaging, the nano form will not need special approval for use in those plastic wraps.

But are titanium dioxide nanoparticles safe?

Several research groups have shown they may have an impact on health.

When titanium dioxide nanoparticles were fed to mice, the nanoparticles traveled out of the digestive tract and into places such as the liver and kidney where signs of tissue injury were observed. And at certain doses, titanium dioxide nanoparticles given to pregnant mice led to birth defects.

In one study of the long-term effects of exposure, titanium dioxide nanoparticles were shown to interfere with egg production and embryo survival in zebrafish.

Clearly these studies hint that the use of nanomaterials (such as titanium dioxide) may warrant caution.

Just how small are nanomaterials?

Although scientists, industry, and governmental agencies do not entirely agree on how to define the size of nanomaterials, it is generally accepted that a nanomaterial measures between 1 and 100 nanometers in at least one dimension. To put their size into perspective, it would take 1600 trillion of the 100-nanometer particles to fill a one-inch cube. Or stated another way, if you stacked them end to end, it would take nine million to span a yard stick.

Many viruses, including the common cold virus, fall into this size range.

If small enough, nanoparticles can easily enter a human cell and accumulate there. One research study found that 45-nanometer sized gold nanoparticles were readily taken up by and accumulated in cultured human cells but not the larger 70-nanometer size. While gold nanoparticles are not typically used in food products, they are often used in scientific studies because they are easily traceable. Though gold is considered an inert metal, one animal study found that injecting rats with gold nanoparticles resulted in liver injury.

A confounding problem is that nanoparticles have considerably more surface area than their larger (and better-characterized) counterparts called “fine particles.” (Think glass marbles versus a basketball.) The increase in surface area of nanoparticles can have a remarkable effect on how they behave chemically and physically – behavior that may have unexpected outcomes.

But size isn’t everything. The shape and chemical composition of a nanoparticle can also affect how they interact within the body. Nanomaterials are made in various shapes including spheres, rods, and tubes. They can be made of a single material or a mixture of several materials, and they can be of organic or inorganic composition. Each of these characteristics must be considered when evaluating their food safety.

Regulating their use

Governmental agencies are not just having a tough time defining what constitutes a “nanomaterial” but also how to regulate it in consumer products like food.

Read more . . .
 
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