Brushing our teeth, applying lip gloss, or taking a dietary supplement — nowadays, any of these activities might expose us to a very peculiar form of matter.

Steffen Foss Hansen, at the Technical University of Denmark, has compiled an online database of more than 2,500 consumer products containing engineered nanoparticles.

The substances found in some of these products are called nanoparticles: particles with at least one dimension smaller than 100 nanometers, which is about one-thousandth the width of a human hair. Nanoparticles confer special properties — strength, lightness, chemical reactivity — that make them useful in a wide array of settings, from cosmetics and clothing to printer and photocopier toner to products for home, garden, and car maintenance. Yet much remains to be learned about how “nano-enhanced” materials affect humans, animals, and the environment. And for the most part, the public is in the dark.

Until a few years ago, American consumers could at least consult a smartphone app called findNano and get a list of products with basic information about the presumed content of nanoparticles, but with no explicit reference to potential risks. (The list came from the Nanotechnology Consumer Products Inventory, launched in 2005 by the Project on Emerging Nanotechnologies at the Woodrow Wilson International Center for Scholars.) But the app was discontinued, and the inventory is now being overseen by an independent group of researchers.

So Steffen Foss Hansen, an associate professor of Nanotechnology and the Environment, and Environmental Management and Ethics, at the Technical University of Denmark, decided to launch a similar online database, now listing more than 2,500 consumer products containing engineered nanoparticles. In his enriched version, each product is described by color-coded dots to indicate the degree of potential exposure and potential harm to humans and the environment.

For this installment of the Undark Five, we asked him about the uncertainties surrounding nanoparticles and their long-term safety for human health and the environment. Questions and answers have been edited for length and clarity.

“It seems that the more resources we set aside to maintain the database, the more products with ‘nanoclaims’ we find.”

UNDARK — Why and when did you create this database?

STEFFEN FOSS HANSEN — We created the database back in 2012 after years of frustration with the lack of overview of nanoproducts on the European market. Our intended user is primarily the informed consumer who wishes to know more about nanomaterials in their products and what is known about the exposure and hazards. We have 2,558 products in our database and we could easily add 10 to 20 a week. We only have products where producers [or] retailers make specific “nanoclaims.” Furthermore, it seems that the more resources we set aside to maintain the database, the more products with nanoclaims we find.

UD — A similar inventory of consumer products was launched a few years ago in the U.S., and more recently France set up a compulsory registry for all uses of nanoparticles that other countries appear to be willing to adopt. Are these efforts coherent?

SFH — The inventory maintained by Woodrow Wilson in the U.S. was very pioneering when it was set up back in the day, but was very focused on products on the market in the U.S. and maybe Asia. Many products that we knew of in the E.U. were not included. Only summary data is made available by the French authorities, and the data submitted by industry is not publicly available, which is in stark contrast to our database.

UD — In your database, each consumer product is accompanied by a series of indicators related to possible exposure and possible harm. Describe them.

SFH — Each product is described by five dots. The first three dots refer to potential for exposure (to professional end users, consumers, and the environment) and the remaining two dots to the hazard potential, for humans and for the environment. The colors signify whether the indications of exposures or effects, each considered independently, are high (red), medium (yellow), low (green), or unknown (gray). All details about the methodology are provided in our website. Currently we list 556 products that are either red or yellow for consumer exposure potential and also have a high harm potential for humans.

UD — Should consumers and policymakers be worried by the wide availability of the many products with a yellow or red light, both for potential exposure and potential harm?

SFH — Yes, I think so. If you combine the information that we provide in the database, one can see that the nanomaterials that we know are associated with human and environmental harm are also the nanomaterials for which human and environmental exposure is to be expected. Furthermore, we find it worrying that there are so many products available to consumers where the producers/retailers make “nanoclaims” but where the identity of the nanomaterial is not provided — even when they are obliged to do so according to the E.U. legislation on cosmetics and biocidal products and treated articles. Over all we list 1,479 products for which we do not know which nanomaterial is used (nor if any is used at all, since some companies use “nano” as a marketing tool) and hence we cannot determine whether potential harm for that product is red, yellow, or green. Of course we would need to know the identity of the nanomaterial used in order to do any kind of safety evaluation [or] risk assessment.

UD — The European Commission decided last spring not to establish a mandatory E.U.-wide registry for nanotechnology that proponents said would make it simpler to detect possible long-term negative effects and track them back to specific causes. What do you think of this decision?

SFH — I think it was a mistake. Without this information, we cannot make any kind of meaningful safety evaluation [or] risk assessment. I would still argue that the E.U. has been more progressive when it comes to regulation of nanomaterials: Legislation on cosmetics, biocides, and food has been amended requiring industry to take “nanospecific elements” into account. These are not very specific on how this should be done, but nevertheless.

Most of these amendments were due to the European Parliament and not the European Commission, which seems to be in internal conflict about how best to regulate nanomaterials. I think we need to ask the fundamental questions of whether this or that nanoproduct is useful and whether nanomaterials are necessary for that specific application. If it is found to be necessary, we can then start discussing the exposure and hazard potential, and whether it is possible to eliminate exposure altogether or whether we need to implement measures to minimize the risks.

Fabio Turone, a 2016-17 Knight Science Journalism fellow, is a science writer and editor based in Milan, Italy. He launched and currently heads the professional association Science Writers in Italy, with the aim of promoting international exchanges and collaboration.