Friends of the Earth (Australia) has recently completed a surveillance project on nanoparticles in food1. Results showed that 14 types of food products commonly sold in Australia were found to contain nanoparticles of titanium dioxide and silica. Food Standards Australia New Zealand has issued a statement in response – at present, there has been no evidence indicating that those nanoparticles will cause any adverse health effect of people after oral ingestion.
1 Friend of the Earth, 2015 http://emergingtech.foe.org.au/independent-testing-finds-potentially-harmful-nanoparticles-in-common-food-products/
Toxicity of nanoparticles is always controversial and the variety of nanomaterials available in the market is growing. Many countries have expressed their concerns over the safety of “Nanofood” and shall conduct risk assessment if necessary.
Photo Source：Food & Water Watch, 2009 http://www.foodandwaterwatch.org/reports/unseen-hazards-from-nanotechnology-to-nanotoxicity/
What is “Nanofood” ?
First, we should know “nanometer” (nm) is a unit of length, and 1 nm equal to one billionth of a metre. In this connection, the size of a nanomaterial is extremely small while its specific surface area is very large. This gives nanoparticles some unique properties (e.g. adsorption and dispersion) and different from materials of normal size. Since the properties of nanoparticles / nanomaterials are so amazing, nanotechnology has been widely applied in different sectors, including food industry.
Generally speaking, “Nanofood” refers to food with ingredients being modified into structures sized between approximately 1 and 100 nm. In addition, some peoples think that food packed with packaging materials made up of nanomaterials, can also be considered as “Nanofood”.
Presence of Nanoparticles in “Non- Nanofood” ?
For those foods without any nano-modified ingredients, migration of nanoparticles from food packaging materials to food may still occur. Moreover, food may be “contaminated” during primary production at farm level or food processing. For example, spraying pesticides with nanomaterials can contaminate crops. Other agricultural chemicals (e.g. veterinary drugs), environment (water, soil and air) and tools use for food production can also be potential sources of nanoparticle pollution.
Is Nanofood Toxic?
In order to judge whether a nanomaterial is toxic or not, countries usually conduct toxicological risk assessment. Simply speaking, absorption, distribution, metabolism and excretion of nanomaterials in experimental animal will be studied first. In addition, the response / situation of experimental animal after ingestion of the nanoparticle for a certain period of time will be assessed. This helps to predict the impact of the nanoparticle on human health.
In animal studies, several nanoparticles have been found to be toxic. For example, it is reported that titanium dioxide could be detrimental to different mammalian cells (neural cells, cardiac muscle cell, liver cell, intestinal cell, germ cell, etc.) e.g. lowering cell activity and leading to cell death; moreover, in a study feeding mice with titanium dioxide repeatedly, severe damages to liver and heart were observed in young mice while liver and kidney of adult mice showed minor damages only. 2
However, at present there is no tenable evidence that nanoparticles of titanium dioxide (and other nanomaterials) will lead to adverse health effect of human who ingest the nanoparticles. Therefore, toxicity of nanoparticles is still controversial.
Regarding the safety of nanofood (and food contact materials incorporated with nanoparticles), no general conclusion can be made. This is because toxicological assessment methods used by different countries are not always the same, and there are uncertainty factors about the evaluation made (e.g. lack of health assessment concerning chronic exposure to nanoparticles). More scientific data and assessment are needed for further safety evaluation of nanofood.