Nanotechnology, the science of manipulating materials on an ultraminiscule scale, is used in a growing range of consumer products-from semi-conductors and solar cells to food, health products and cosmetics. Yet, according to the Royal Commission on Environmental Pollution (RCEP), this trend may represent a potential hazard to both human health and the environment.
Although it found no evidence of actual harm from nanomaterials, the report emphasizes that this is not because they have been proved safe, but because the research so far is inadequate. "Almost by definition, with novel materials and particularly nanomaterials, there are virtually no data on chronic, long-term effects on people, other organisms or the wider environment," the report says, while calling for urgent testing and tighter regulations to address gaps in the current knowledge.
What the report authors did find, however, on analyzing the laboratory data, was that some nanomaterials have properties that make them "potentially harmful" and a "case for concern".
Indeed, further reports have uncovered compelling evidence that manufactured nanomaterials can enter the body via inhalation, ingestion and skin absorption, and may cause biological damage. The adverse biological effects have common metabolic themes such as oxidative stress, interference with cell-to-cell transfer of molecules and mitochondrial damage (www.rcep.org. uk/novelmaterials.htm).
Given the more than 600 products containing nanomaterials currently available in the global marketplace, this information certainly deserves our attention.
The evidence so far
One particularly worrying nano-material is carbon nanotubes (CNTs), used to make strong, lightweight composites for everything from medical devices and bicycle frames to computer chips. They are the most commonly cited when it comes to
the effects of nanoparticles on health and the environment. The main problem is that they're similar in structure and size to asbestos, lead-ing many to question their long-term health and safety (Nightingale P et al. Nanomaterials Innovation Systems: Their Structure, Dynamics and Regulation, 2008; www.rcep.org.uk/novelmaterials.htm).
NASA scientists say that these tiny light nanoparticles "could pose an occupational inhalation exposure hazard". Their analysis of animal data shows that, once in the lungs, CNTs can lead to inflammation, epithelioid granulomas (microscopic nodules), biochemical/toxicological changes and fibrosis. Moreover, some CNTs are more toxic than quartz, a serious occupational health hazard when chronically inhaled (Crit Rev Toxicol, 2006; 36: 189-217).
Another worrying nanomaterial is nanosilver, used for its antimicrobial properties in clothing, wound dress-ings and personal-care products. It was found to damage the lungs of rats by causing 'oxidative stress' within cells. In fact, the smaller the particles, the worse the damage (J Phys Chem B, 2008; 112: 13608-19).
In the lab, nanosilover was toxic to rat liver and human brain cells (Toxicol In Vitro, 2005; 19: 975-83; Toxicol Sci, 2006; 92: 456-63), and was the most toxic to germline stem cells of all the tested nanomaterials. These effects can inhibit fertility and may adversely affect offspring, the scientists said (Toxicol Sci, 2005; 88: 412-9).
Yet another concern raised by Friends of the Earth (FOE) is that silver nanoparticles may interfere with the good bacteria in our bodies and in the environment, ultimately resulting in more virulent harmful bacteria (www.foe.org/pdf/nano_food.pdf).
These findings are all the more worrying in light of a new study which found that nanosilver can leach from fabric when washed, and escape through the waste water into the environment (Environ Sci Technol, 2008; 42: 4133-9).
Also on the list of nanomaterials to watch out for is titanium dioxide (TiO2), a widely used white pigment added to paints, coatings, plastics, inks, foods, medicines, toothpaste, cosmetics, sunscreens and other personal-care products.
Recently, scientists in China discovered that nano-sized TiO2 particles can travel from the nose to the brain, and cause damage to the brain cells of laboratory mice. They also observed significant changes in the cells of the olfactory bulb and hippocampus following a relatively low exposure dose and within a short period of time (Toxicology, 2008; 254: 82-90). These findings raise serious safety concerns not only for workers exposed to TiO2 nanoparticles, but also for consumers, who can inhale particles from cosmetics such as face powder.
However, we are much more likely to come into contact with TiO2 nanoparticles via the skin, probably through sunscreens and cosmetics, although several laboratory studies have demonstrated that nano-sized TiO2 particles do not penetrate the skin and, therefore, pose no risk to human health (Int J Cosmet Sci, 1999; 21: 399-411; Crit Rev Toxicol, 2007; 37: 251-77).
Nevertheless, according to the UK consumer-interest group Which?, there are concerns as to the safety of TiO2 nanoparticles when used on damaged skin, such as skin that is sunburnt. "Although there seems to be a reasonable amount of agree-ment by experts that these nano-particles would not be able to get through healthy skin because they would still be too big to squeeze through the gaps in the barrier that the skin presents, it isn't clear whether they could pass through the skin if it is damaged," says the group (see which.co.uk for more details).
Clearly, more research is needed on this nanomaterial to ascertain its safety.
Although test-tube and animal data on nanomaterials may not apply to humans in a real-life setting, the early warning signals surrounding nanotoxicity certainly warrant a precautionary approach to this new technology. Indeed, some public-interest groups, such as FOE, have called for a moratorium on the development and manufacture of nanomaterials until adequate regulations are in place.
In the meantime, the nanotech revolution is set to continue unrelentingly and, once again, scant labelling requirements put the onus on the consumer.
One way to protect ourselves is to stick to natural, organic products whenever possible and to look for companies that declare that they don't use nanotechnology. Alterna-tively, finding out which companies are the ones that use nanotechnology can help us make educated decisions about what to spend our money on. One useful resource is The Project on Emerging Nanotechnologies, whose website (www.nanotechproject.org) lists hundreds of nanomaterial-containing products along with their manufacturers.
So, staying informed may be the best way to stay safe.
Nanotechnology can be defined as dealing with materials, systems and processes that operate at a scale of 100 nanometres (nm) or less. One nanometre (nm) is one-thousandth of a micrometre (mcm), one-millionth of a millimetre (mm) and one-billionth of a metre (m). To put this into context: a strand of DNA is 2.5 nm wide, while a protein molecule is 5 nm, a red blood cell is 7000 nm and a human hair is 80,000 nm in diameter.
Nanoparticle risks: what we know
Much of what is known of the hazards posed by nanoparticles is derived from studies of unintentionally produced and released nanosized particles such as from fossil-fuel combustion. Collectively, these studies show that:
- when inhaled, nanoparticles are highly likely to be deposited in all regions of the respiratory tract
- nanoparticles can evade specific defence mechanisms
- when in contact with skin, they can penetrate to the dermis and then via the lymphatics to the lymph nodes
- their small size facilitates uptake into cells and into the blood and lymph circulation to reach sensitive target sites such as bone marrow, lymph nodes, the spleen and heart
- unlike larger particles, nanoparticles can pass via nerve axons into the brain
- they have a greater potential for inflammatory and oxidative stress than larger particles
- particles with no specific toxicity, such as carbon black and titanium dioxide, can cause fibrosis, neoplasms and lung tumours in laboratory animals.
From Nightingale P et al. Nanomaterials Innovation Systems:
Their Structure, Dynamics and Regulation ( www.rcep.org.uk )
Nanomaterials in food and cosmetics
Nanomaterials are used in a wide variety of consumer goods, but the biggest potential threat to our health is most likely to come from the food and cosmetics industries.
A study by environmental group Friends of the Earth (FOE) found that nanomaterials are now in processed foods, food packaging and food-contact materials such as storage containers, cutlery and chopping boards. They are used to make more potent food colourings, flavourings and nutritional additives, and are added as antibacterial agents. When they enter the body via the gut, they accumulate over time. Eventually, this may result in 'nanopathologies' such as granulomas, lesions (areas of damaged cells or tissue), cancer or blood clots.
FOE identified over 100 nanomaterial-containing food products currently on sale worldwide (including diet-replacement milkshakes, cooking oil, tea and fortified fruit juice). But, as many food manufacturers may be unwilling to advertise the nanomaterial content of their products, FOE believes that this is only a small fraction of the total number of nano-containing products actually out there (www.foe.org/pdf/nano_food.pdf).
Nanomaterials in cosmetics are even more worrying. A 2006 survey by the US non-profit Environmental Working Group identified nearly 9800 products using nano-scale ingredients, including 256 that contained one or more of 57 different nanoscale or 'micronized' ingredients, and an additional 9509 products containing ingredients that come in nano sizes. Yet, nearly all of these products offered no information regarding particle size on their labels (www.ewg.org/node/21738).Considering the lack of safety data for these materials, such widespread use is disturbing. Fortunately, though, the EWG has compiled a list of potentially hazardous cosmetics (including lipsticks, moisturizers, antiageing serums, sunscreens, body creams, cleansers and acne treatments), so that consumers can avoid them if they so wish (go to www.ewg.org/node/26564).