One of the latest trends in manufacturing for today's consumer products is the use of engineered nano-particles (ENP's), yet, most people have no idea that they are consuming and absorbing ENP's. Research is discovering that certain ENP's may be toxic and extremely harmful to human health, causing cell and DNA damage, potentially leading to the development of cancers.
Nano-particles are microscopically sized particles with at least one dimension less than 100 nano-meters (nm). To put this in perspective, a sheet of paper is about 100,000 nm thick, and a strand of human DNA is about 2.5 nm thick. A current trend in research and development, ENP's are generating widespread interest for their potential to enhance consumer materials and food products, and for their potential applications in the electronic, optical and biomedical fields. "Nanoparticles are of great scientific interest as they are effectively a bridge between bulk materials and atomic or molecular structures." 
In the marketplace, nano-particles can be found in sunscreens, toys, clothing, food, drugs, candy, cosmetics, ceramics, paints, and many other common products, and are already an ubiquitous part of our toxic consumer environment. Some food activists have already called attention to the dangers of the commonly used nano-particle titanium dioxide, noting that the "form of the common 'whitening' agent known as titanium dioxide is capable of inducing "tumor-like" changes in exposed human cells."  Nanotitanium is found in products produced by Jello, Nestlé, M&M's, Mother's, Mentos, Albertson's, Hostess and Kool Aid.  Previous concerns have largely been focused on cell damage in the human body, however, a new study from MIT and the Harvard School of Public Health (HSPH) indicates that certain ENP's may in fact directly damage human DNA, a concern that should have manufacturers and regulators immediately halting the use of nano-particles in consumer products. The researchers found that zinc oxide nanoparticles, often used in sunscreen to block ultraviolet rays, significantly damage DNA. Nanoscale silver, which has been added to toys, toothpaste, clothing, and other products for its antimicrobial properties, also produces substantial DNA damage, they found.  As worldwide cancer rates continue to rise, these results are extremely alarming, especially in light of the World Health Organization's (WHO) recent prediction that human cancer rates will rise a staggering 57% in just the next 20 years. 
The MIT And HSPH study zeroed in on just five commonly used nano-particles, shedding some light on how these particles cause disruption and mutations to human DNA: The researchers focused on five types of engineered nanoparticles - silver, zinc oxide, iron oxide, cerium oxide, and silicon dioxide (also known as amorphous silica) - that are used industrially. Some of these nanomaterials can produce free radicals called reactive oxygen species, which can alter DNA. Once these particles get into the body, they may accumulate in tissues, causing more damage.  The study noted that the zinc oxide, used most often in sunscreens, and nano-silver produced the greatest DNA damage: ...the MIT and HSPH researchers tested the nanoparticles' effects on two types of cells that are commonly used for toxicity studies: a type of human blood cells called lymphoblastoids, and an immortalized line of Chinese hamster ovary cells. Zinc oxide and silver produced the greatest DNA damage in both cell lines. At a concentration of 10 micrograms per milliliter - a dose not high enough to kill all of the cells - these generated a large number of single-stranded DNA breaks. Silicon dioxide, which is commonly added during food and drug production, generated very low levels of DNA damage. Iron oxide and cerium oxide also showed low genotoxicity.  This study adds a new dimension to the growing concerns over the use of nano-particles because most prior research has been focused on cell damage, not on the effects that these particles have on DNA. Until now, most studies of nanoparticle toxicity have focused on cell survival after exposure. Very few have examined genotoxicity, or the ability to damage DNA - a phenomenon that may not necessarily kill a cell, but one that can lead to cancerous mutations if the damage is not repaired.  Conclusion
Some researchers, including the author of the MIT/HSPH study paper, are exhibiting concern over the potential of toxic, unregulated nano-particles: "It's essential to monitor and evaluate the toxicity or the hazards that these materials may possess. There are so many variations of these materials, in different sizes and shapes, and they're being incorporated into so many products," says Christa Watson, a postdoc at HSPH and the paper's lead author.  Since nano-particles are already being deployed in many common foods, drugs and other products, and we now know that they cause damage to DNA, is simply monitoring and evaluating their toxicity a responsible way to approach this?
Just as with genetically engineered foods, which are already being consumed worldwide, researchers have determined that they can be damaging to human health, yet the status quo for bringing products to market and for removing products from market permits their widespread consumption even in the face of credible research that indicates their dangers. According to Tom Philpot, writing for Grist in 2010, 'As with GMOs, the strategy seems to be: release into the food supply en masse first; assess risks later (if ever).'  Sources