Many people are unaware of it, but nanoparticles (particles that range from 1 to 100 nanometers) are already all around us, and plans are being made to have them be even more ubiquitous.
Nano-sized particles are nothing new in nature. They are created through processes such as combustion, food milling, and homogenization, and occur naturally in smoke, air, and seaspray. What is new is the introduction of man-made particles of this size. These manufactured particles come in many varieties, including nanowires, fullerenes, quantum dots, and nanotubes.
Nanoparticles are almost too small to be conceptualized. For instance, a double strand of DNA is 2 nanometers, which is actually larger than some of the man-made nanoparticles. This small size gives these particles certain desirable thermal, physical, biological, and optical properties. In recent years, manufacturers have begun to use such materials in the manufacture of things such as sunscreen, clothing, cosmetics, dietary supplements, and electronics. As of 2007, the National Science Foundation estimated that up to $70 billion products using nanotechnology were sold in the United States on an annual basis. In fact, there is increasing interest in using nanoparticles in the food industry in order to improve flavor, texture, nutrition, and shelf life. The question then arises - how safe are these nanoparticles? What is the risk to human health? Environmental health? What research is being done to determine potential health effects?
The answer, unfortunately, is that no one really knows. The field of nanotechnology is so new that scientific research has not kept up with industry use. Also, toxicological studies can be problematic, as the small size of the particles makes it extremely challenging to trace them through the body. Further, the sizes and shapes of nanoparticles even within a single man-made batch can vary widely from one particle to the next. A change in shape or mass can greatly alter how the particle moves and behaves in the body. Also, manufacturers are creating new types of materials at an almost dizzying pace. Changes in coatings, functionalizations, surface charges, and manufacturing processes can greatly impact how particles behave in the body.
What is feared by some is that the tiny size of these particles would allow them to be taken up more readily in bodily tissue. More alarmingly perhaps is the possibility that they could pass across the placenta and breech the blood/brain barrier. Also of concern is the potential for these particles to be absorbed through the skin. It is likely that, once ingested or absorbed, these nanoparticles would have an unusual ability to travel throughout the body - including cells and cell nuclei.
Studies involving animals have shown that mice that ingested nanoparticles in drinking water for five days were found to have DNA and chromosomal damage and inflammation. Animal studies have also shown that the offspring of exposed animals can be affected. In one study, the male offspring of titanium dioxide-exposed mice experienced genital deformities, neurologic damage, and changes in gene expression in the brain. Materials such as silver nanoparticles, which are used in clothing for their antimicrobial properties, have been shown to release in the washing machine and enter the wastewater stream. These particles have known to harm mammals by damaging a variety of cell tissue, crossing of the blood-brain barrier, and causing neurotoxicity.
The environmental impact of nanoparticles is also unknown. Even if it is safe for consumers to apply nanoparticle containing products to their skin, those particles may present problems when they are washed off, or when small amounts are worn off of more solid products. There is evidence that nanoparticles such as zinc oxide and titanium oxide can cause harm to organisms such as water fleas, algae, and frogs, and can travel up the food chain to cause as-yet unknown potential problems.
An additional concern is exposure of workers involved in the manufacture of materials containing nanoparticles. Because the toxicological aspects of these materials are as yet largely unknown, there exist no regulatory exposure limits. Even if there were such limits, performing an industrial hygiene assessment for these exposures would present its own challenges, as the equipment necessary for such an endeavor is extremely expensive. In the absence of straightforward exposure limits, the National Institute for Occupational Safety and Health (NIOSH) has performed its own research into the field of nanoparticle exposure and has released several publications related to working safely in the nanotechnology field.
Because manufacturers are not required to disclose the presence of nano-sized particles in products, the public is in many cases simply unaware of their presence. Some groups are attempting to change this. For instance, the National Organic Standards Board recommended in 2010 that engineered nanomaterials (ENMs) not be allowed to be used in foods that bear the "organic" label offered by the U.S. Department of Agriculture. Other consumer advocacy groups think that the presence of these materials should be listed in any product, whether or not it is ingestible. But, as things stand now, the public remains largely unaware of the growing presence of these materials, the toxicity and environmental impact of which are not yet remotely understood.
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