Health risks of nanos in food

Health risks of nanos in food

By the AVICENN team – Last modification November 2024

Reasons for concern regarding the ingestion of nanos

Studies have shown that nanomaterials can:

• cross the oral and intestinal barriers and diffuse into the body¹See for example:
  – Quantitative biokinetics of titanium dioxide nanoparticles after oral application in rats (Part 2), Kreyling WG et al, Nanotoxicology, 11(4):443-453, May 2017: the authors observed the passage of the gastrointestinal barrier for a small fraction of TiO2 in the rat (0.6% of the administered dose), which is found after 7 days accumulated in different organs, mainly, the liver, lungs, kidneys, brain, spleen, uterus and skeleton (cited by the HCSP in its report Review of knowledge on the effects of titanium dioxide (TiO2) nanoparticles on human health; characterization of population exposure and management measures, April 2018)
  – Food additive E171: the first results of oral exposure to titanium dioxide nanoparticles, INRA, press release, 20 January 2017 and E171: a hazard identified in rats, a risk to be assessed in humans, INRA Sciences & Impacts press release, 1 February 2017: Food-grade TiO2 impairs intestinal and systemic immune homeostasis, initiates preneoplastic lesions and promotes aberrant crypt development in the rat colon, Bettini S et al, Scientific Reports, 7:40373, published online January 20, 2017
  – Pharmaceutical/food grade titanium dioxide particles are absorbed into the bloodstream of human volunteers, Pele et al, Particle and Fibre Toxicology, 12:26, September 2015
  – Oral exposure to titanium dioxide (TiO2) nanoparticles: from crossing the oral and intestinal epithelium to fate and effects in the body, Bettini S and Houdeau E, Biology Today, September 2014
  – Titanium dioxide nanoparticle impact and translocation through ex vivo, in vivo and in vitro gut epithelia, Brun E et al, Particle and Fibre Toxicology, 11:13, 2014
  – Size and surface charge of gold nanoparticles determine absorption across intestinal barriers and accumulation in secondary target organs after oral administration, Schleh C. et al, Nanotoxicology, 6(1), 36-46, 2012
  – Nano- and microparticulate drug carriers for targeting of the inflamed intestinal mucosa, Collnot E.M. et al, J Control Release, 161, 235-46, 2012
  – Origin and fate of dietary nanoparticles and microparticles in the gastrointestinal tract, Powell J.J. et al, J Autoimmun, 34, 226-33, 2010 . Studies have also shown that silica or silver nanoparticles agglomerate in water or in acidic environments (such as the stomach) but disperse in the intestine where the pH is neutral: they can then cross the intestinal barrier more easily²See our info sheet The entry points, fate and behavior of nanomaterials in the human body, veillenanos.fr.

• accumulate in the organs³Nanotechnologies and nanoparticles in food and feed, Afssa (now ANSES), March 2009: the digestive tract, liver and spleen are the main target organs. After oral administration of 60 nm silver nanoparticles to rats for 28 days, silver was found in the stomach, kidneys, liver, lungs, testicles, brain and blood: cf. Kim, J.S. et al. Twenty-eight-day oral toxicity, genotoxicity, and gender-related tissue distribution of silver nanoparticles in Sprague-Dawley rats, Inhalation. Toxicol., 20(6), 2008 (digestive tract, liver, spleen but also stomach, kidneys, lungs, testicles, brain), in the blood and inside the cells

• cause disturbances or even harmful effects, particularly on the intestinal microbiota⁴See for example:
  – A systematic review on the effects of nanomaterials on gut microbiota, Utembe W et al, Current Research in Microbial Sciences, 3, 100118, 2022
  – Nanoparticles in the Food Industry and Their Impact on Human Gut Microbiome and Diseases, Ghebretatios, M et al., Int. J. Mol. Sci., 22(4) :1942, 2021
  – Impacts of foodborne inorganic nanoparticles on the gut microbiota-immune axis: potential consequences for host health, Lamas B et al, Particle and Fibre Toxicology, 17:19, 2020.

In addition to the health repercussions of nanoparticle ingestion, it should be noted that the environmental risks are also poorly understood and a cause for concern.

Many scientific uncertainties

Much is still unknown today about the impact that ingestion of nanomaterials can have on human health. Oral toxicity studies of nanoparticles are rare and many may have had methodological weaknesses that make their results difficult to use . Experimental conditions still poorly reflect how consumers are actually exposed. The nanomaterials considered are often synthesized in the laboratory and thus different from the nanomaterials (and nanomaterial residues) that consumers actually ingest. In addition, the physicochemical characteristics of the tested nanoparticles and their interactions with the food matrix are insufficiently documented. Nevertheless, progress has recently been made, thanks to improvements in researchers’ practices, tools and protocols.

The complexity of assessing the risks associated with the ingestion of nanomaterials

One of the problems that is likely to remain, however, is the great complexity of assessing the risks associated with the ingestion of nanomaterials: the toxicity of nanoparticles differs according to their physicochemical characteristics (size, shape, degree of agglomeration, etc.). However, these characteristics vary greatly from one nanomaterial to another and can change throughout their life cycle:

• depending on the conditions under which the nanomaterials are synthesized, stored, and possibly coated
• by the transformations they undergo during cooking and preparation of dishes or in the digestive system¹⁸Mammalian gastrointestinal tract parameters modulating the integrity, surface properties, and absorption of food-relevant nanomaterials, Bellmann S et al, WIREs Nanomed Nanobiotechnol, 2015 (e.g. contact with the acidic environment of the stomach, etc.)
• during interactions with packaging and/or with other ingredients and chemical substances with which nanomaterials are mixed (before and during ingestion and digestion); for example, a “cocktail effect” with certain other synthetic molecules could occur¹⁹Could nanomaterials, combined with other substances, become (more) dangerous? Toxicologists often work by isolating substances, which does not allow them to establish the interaction effects of a plurality of substances entering the body.

In addition, the risk assessment should consider:

• individual susceptibility (stress increases for example intestinal permeability to xenobiotics)²⁰See also E. Houdeau (INRA), “Nanoparticles and the intestinal barrier: understanding the crossing mechanisms” : Diaporama, Crossroads of agronomic innovation (CIAG), November 2012 ; Academic article, Innovations Agronomiques, 24, 105-112, 2012 ;
• the duration and period of exposure²¹Susceptibility of Young and Adult Rats to the Oral Toxicity of Titanium Dioxide Nanoparticles, Small, 9(9/10), 2013. According to a 2012 study, children could consume two to four times more titanium than adults through sweets with high levels of titanium dioxide nanoparticles²²Titanium Dioxide Nanoparticles in Food and Personal Care Products, Weir A. et al., About. Sci. Technol., 46 (4), pp 2242-2250, 2012.

Since 2009, there has been a broad consensus on the need to strengthen research on the risks associated with ingested nanos

In 2009, the Food and Agriculture Organization of the United Nations (FAO) and the World Health Organization (WHO) convened an expert meeting on the food safety implications of nanotechnology: the report which was published in 2011, lists the research needed to better assess risks in this field.

Since 2009, ANSES has been calling for improved knowledge about the hazards and consumer exposure to nanomaterials. In October 2016, ANSES was asked by its supervisory ministries to study the risks associated with nanoparticles in food, and more specifically:

• to carry out a detailed study of the agri-food sector with regard to the use of nanos in food
• to prioritize the substances and/or end products of interest according to relevant criteria determined during the expertise
• to review the available data (toxicological effects and exposure data)
• and depending on availability, to study the feasibility of a health risk assessment for certain products.

A “working group” (“WG nano food”) composed of independent experts was set up during 2017. The first results of the expertise, initially expected by the end of 2017²³Response to question No. 85181 by Deputy Yves Daniel, Ministry of Social Affairs, Health and Women’s Rights, October 2016; see also. Anses calls for applications from scientific experts to form a working group (WG) “Nanos & Food”, ANSES, January 2017, was published mid-2020 in a report identifying food products that contain (or may contain) nanomaterials²⁴Cf. ANSES, Nanomaterials in food products; collective expertise report, May 2020.
In 2021, ANSES published a second report: a specific guide to assess the health risks of nanomaterials in food that complements the report on the same subject published a few months earlier by EFSA.

At the end of 2022, Anses published its opinion and report on the risk assessment of the nanometric fraction of the food additive E171 which points out the lack of toxicological data available to perform a complete assessment of the additive E171 and recommends limiting the uses and exposures of workers and consumers to nanomaterials, “by promoting the use of safe products, free of manufactured nanomaterials, and by limiting these uses to those considered in fine as duly justified and subject to a documented demonstration of risk acceptability”.

Notwithstanding the broad consensus on the need to strengthen research on the risks of ingested nanomaterials, research is still limited.

Pending conclusive evaluations, marketing of food products containing nanoparticles continues

In the meantime, consumers continue to ingest nanoparticles of titanium dioxide, silica, silver, etc., most often without knowing it, due to the lack of enforcement of the labeling obligation by the industry.

In presenting its risk assessment guide for nanos in food (2021) as well as its opinion and report on the risk assessment of the nanometric fraction of the food additive E171 (2022), Anses reiterated “the need to limit the exposure of workers, consumers and the environment to nanomaterials” and recommended “to favor safe products, free of these substances”.

Certainly, the additive E171 containing nanoparticles of titanium dioxide has been banned in food in France in 2020 and in the European Union in 2022, but it remains authorized for the moment in medicines and cosmetics (despite the fact that in toothpastes or lipsticks and balms for example, it is likely to be ingested).

In the light of these dangers, calls for caution and the precautionary principle

Recommendations of public authorities on nanos in food

Faced with the numerous uncertainties concerning the risks of nanos in food, many public or para-public organizations have issued recommendations concerning the use of nanomaterials or nanotechnologies in the food sector²⁵See in particular the numerous government reports listed in our bibliography. Among the most comprehensive reports is theOpinion on the ethical issues of nanotechnologies in the agri-food sector of the Commission de l’éthique en science et en technologie du Québec published as early as 2011, with nine concrete recommendations that provide a good overview of recommendations issued by various actors in other settings, with the advantage of being relatively well articulated and almost exhaustive here..

These recommendations can be summarized as follows:

• to carry out a scientific and technological watch on nanotechnological applications in the agri-food industry and the associated risks;
• to carry out further research on risks
• to inform the public
• to consult the population
• to develop an interdepartmental exchange of information on the state of scientific knowledge on risks
• to allow public evaluation of the safety and legal framework of the products concerned
• to demand transparency from manufacturers and labeling of the products concerned.

NGOs have been calling for a moratorium on nanos in food for years

Among the NGOs that have spoken out against the use of nanomaterials in everyday consumer products²⁶See among the 51 stakeholder papers from organizations that took a position during the 2009-2010 national public debate on nanotechnology., various NGOs²⁷See in particular the NGO reports listed in our bibliography have specifically called for a moratorium on the use of nanomaterials in food, including:

• at the international level, ETC Group since 2004 in Canada, then Which? in the United Kingdom, Friends of the Earth Australia and USA, As You Sow in the USA
• then in France, from 2009 France Nature Environnement²⁸See the Cahier d’acteur of France Nature Environnement (FNE) entitled “The urgent need to control the risks associated with nanoparticles and nanomaterials!“and produced for the 2009-2010 national public debate on nanotechnology FNE explicitly requested a “partial moratorium on nano-objects for non-medical use and in contact, in their normal, general public use, with the human body” (including food products and packaging). or Friends of the Earth, and more recently, from 2016, Agir pour l’Environnement and then AFOC in 2017.

Consumers unwilling to be guinea pigs

In a general context where consumers are increasingly suspicious of industrial food²⁹See for example Alimentation : face aux doutes, les internautes s’organisent, Le Monde, April 15, 2013, the reluctance and distrust of consumers towards nanoparticles in food are growing. In general, consumers expect more transparency and do not want to be “guinea pigs” for nano-food³⁰“Nanotechnologies: all guinea pigs of nano-food?“, Basta!, January 14, 2010. However, they are already, unwillingly, since our food already contains nanomaterials – and not only “virtual” nano objects like those used at INRA for the above-mentioned study conducted in 2011.

Since 2016, the petition “Stop nanoparticles on our plates!” launched by Agir pour l’Environnement, demanding a moratorium on nanoparticles in common food products, has gathered more than 52,000 signatures.

In 2011, INRA researchers concluded that “in situations of uncertainty and controversy, decision-makers should pay particular attention to participatory or deliberative modes of communication”. In this respect, the association Sciences Citoyennes has been campaigning for several years for the setting up of citizens’ conventions whose recommendations should be taken into account by the authorities.

The INRA researchers add that “this communication must be accompanied by a strong policy guaranteeing the safety of nanofoods in a context of mistrust among European consumers“. It remains to be seen who should bear the cost of such a safety policy aimed at reassuring the population about applications whose advantages have yet to be proven and from which the agri-food industry and certain research laboratories seem to be the main beneficiaries: should taxpayers pay or should it be companies hoping to profit from their sales ?