What’s new about nanoparticles, as far as risk is concerned, is that many of them are chemically inert as ordinary ions or as larger particles (and hence never had to go through regulatory approval before the nanoparticles were used); but as soon as the particle size reaches nanometre dimensions, they acquire novel physicochemical properties, causing oxidative stress and breaking DNA, and they can get access to every part of the body including the brain, via inhalation and the olfactory nerve.
A comprehensive review by Cristina Buzea and colleagues at Queen’s University, Kingston, Ontario, in Canada, pointed out that human beings have been exposed to natural nanoparticles since the origin of our species, in the form of viruses, dusts from terrestrial and extraterrestrial dust storms, volcanic eruptions, forest fires, and sea salt aerosols (which are largely beneficial).
“More than 1,000 products on the market are nanotechnology-based products,” said Mengshi Lin, associate professor of food science in the MU College of Agriculture, Food and Natural Resources. “This is a concern because we do not know the toxicity of the nanoparticles. Our goal is to detect, identify and quantify these nanoparticles in food and food products and study their toxicity as soon as possible.”
Silver Nanoparticles in Pesticides
Lin and his colleagues, including MU scientists Azlin Mustapha and Bongkosh Vardhanabhuti, studied the residue and penetration of silver nanoparticles on pear skin. First, the scientists immersed the pears in a silver nanoparticle solution similar to pesticide application. The pears were then washed and rinsed repeatedly. Results showed that four days after the treatment and rinsing, silver nanoparticles were still attached to the skin, and the smaller particles were able to penetrate the skin and reach the pear pulp.
The study was published in the Journal of Agricultural and Food Chemistry.
“The penetration of silver nanoparticles is dangerous to consumers because they have the ability to relocate in the human body after digestion,” Lin said. “Therefore, smaller nanoparticles may be more harmful to consumers than larger counterparts.”
When ingested, nanoparticles pass into the blood and lymph system, circulate through the body and reach potentially sensitive sites such as the spleen, brain, liver and heart.
The growing trend to use other types of nanoparticles has revolutionized the food industry by enhancing flavors, improving supplement delivery, keeping food fresh longer and brightening the colors of food. However, researchers worry that the use of silver nanoparticles could harm the human body.
According to lead author of the article, Gretchen Mahler, assistant professor of bioengineering at Binghamton University, much of the existing research on the safety of nanoparticles has been on the direct health effects.
"What we found was that for brief exposures, iron absorption dropped by about 50 percent," said Mahler. "But when we extended that period of time, absorption actually increased by about 200 percent. It was very clear -- nanoparticles definitely affects iron uptake and transport."
While acute oral exposure caused disruptions to intestinal iron transport, chronic exposure caused a remodeling of the intestinal villi -- the tiny, finger-like projections that are vital to the intestine's ability to absorb nutrients -- making them larger and broader, thus allowing iron to enter the bloodstream much faster.
“This study provides a promising approach for detecting the contamination of silver nanoparticles in food crops or other agricultural products,” Lin said.
Engineering Nanomaterials Is A Confirmed Hazard
The research on two of the most common types of engineered nanomaterials is published online in Environmental Health Perspectives (EHP), the journal of the National Institute of Environmental Health Sciences (NIEHS). It is the first multi-institutional study examining the health effects of engineering nanomaterials to replicate and compare findings from different labs across the country.
The study is critical, the researchers said, because of the large quantities of nanomaterials being used in industry, electronics and medicine. Earlier studies had found when nanomaterials are taken into the lungs they can cause inflammation and fibrosis. The unique contribution of the current study is that all members of the consortium were able to show similar findings when similiar concentrations of the materials were introduced into the respiratory system
Titanium dioxide (TiO2) nanoparticles found in sunscreen and cosmetics have already been found to cause systemic genetic damage in mice, according to an earlier comprehensive study conducted by researchers at UCLA's Jonsson Comprehensive Cancer Center.
The TiO2 nanoparticles induced single- and double-strand DNA breaks and also caused chromosomal damage as well as inflammation, all of which increase the risk for cancer.
University of Plymouth researchers subjected rainbow trout to titanium oxide nanoparticles which are currently being considered for the food industry. They found that the particles caused vacuoles (holes) to form in parts of the brain and for nerve cells in the brain to die. Although some effects of nanoparticles have been shown previously in cell cultures and other in vitro systems this is the first time it has been confirmed in a live vertebrate.
Diseases associated with inhaled nanoparticles include asthma, bronchitis, emphysema, lung cancer, and neurodegenerative diseases, such as Parkinson's and Alzheimer's diseases. Nanoparticles in the gastrointestinal tract have been linked to Crohn's disease and colon cancer. Nanoparticles that enter the circulatory system are implicated in arteriosclerosis, blood clots, arrhythmia, heart diseases, and ultimately death from heart disease. Nanoparticles entering other organs, such as liver, spleen, etc., may lead to diseases of these organs. Some nanoparticles are associated with autoimmune diseases, such as systemic lupus erythematosus, scleroderma, and rheumatoid arthritis.
There is clearly an urgent need not only to stem but also to reverse the unregulated tide of nanoparticles that are released onto the market. In view of the existing evidence, the following actions should be taken.
Engineered nano-ingredients in food, cosmetics and baby products for which toxicity data already exist (e.g., silver, titanium oxide, fullerenes, etc.) should be withdrawn immediately.
A moratorium should be imposed on the commercialization of nano-products until they are demonstrated safe.
All consumer products containing nanotechnology should be clearly labelled. If you see non-Nano, that's a good sign.
A robust regulatory programme on nanotechnology - including characterisation and standardisation of manufacture - should be implemented as soon as possible.
There should be earmarked funding for research into the hazards of nanotechnology.
Marco Torres is a research specialist, writer and consumer advocate for healthy lifestyles. He holds degrees in Public Health and Environmental Science and is a professional speaker on topics such as disease prevention, environmental toxins and health policy.