Just how risky could nanoparticles in sunscreens be?

by Andrew Maynard on June 8, 2010

Following up from my previous post, here’s an open question to Friends of the Earth:

What is your worst case estimate of the human health risk from titanium dioxide and/or zinc oxide nanoparticles in sunscreens?

What I am interested in is a number – a probability of a specific human health impact being caused by using a given amount of nano-sunscreen over a certain amount of time.  Something like:

“In the worst case, it is estimated that using [number] grams per day of sunscreen comprising [percent] TiO2/ZnO nanoparticles over [number] days could lead to an [percent] risk of the user developing [disease].”

This can be based on an extrapolation of the current state of the science to a worst case scenario.  But it must be plausible.  And the calculations/sources to get to the end number must be transparent.

I’m asking because I am interested to see whether it is possible to place an upper bound on the safety of nanoparticle-based sunscreens, and whether this will be useful in moving the dialogue over nano-enabled sunscreens away from ungrounded speculation, towards evidence-based discussion.

So that’s the challenge.  I’m hoping my good friends at Friends of the Earth will rise to it.

1 Dr. Gregory Crocetti June 11, 2010 at 7:39 am

Hi Andrew,

I do not speak on behalf of Friends of the Earth in any way, but feel compelled to contribute a comment towards this dialogue.

Your approach here is rather peculiar and even a little playful – although not exactly fair. I’ll explain why I think this.

Friends of the Earth organisations around the world surely do not have the financial means to conduct their own research into the safety of nanoparticles. And from what I have seen, they primarily use their understanding of existing scientific data to simply raise questions regarding nanotechnology safety, in order to call for a significant increase in nanotech safety research and regulation as well as labelling of products containing nanoparticles.

These people generally work for little or no money, primarily in the interests of the wider public and our natural world. And while I may not agree with every single conclusion they may have collectively drawn from the existing data, I do agree with their goals to increase funding into safety research, as well as an increase regulation and labelling.

You accuse Friends of the Earth of speculation, rather than evidence-based discussion. Yet your question to FOE ignores the evidence relating to the risk of sunscreen nanoparticles working their way up the food chain (identified in the Daphnia-Zebrafish study).

As a trained microbial ecologist, I am acutely aware of the significance of disturbances to the base of food chains in our natural world….not to mention the well-known risks caused by bioaccumulation of metals within food chains.

Of all of the potential risks that Friends of the Earth highlighted from the existing sunscreen nanosafety research data, it’s quite troubling that your question disregards the potentially most significant and dangerous risk of all….

2 Andrew Maynard June 11, 2010 at 12:47 pm

Hi Gregory,

I’ll hold off responding in full until the folks at FoE have posted their response – they tried to post comments last night, but unfortunately weren’t successful (my fault, not theirs). Just a few quick responses though:

With the question, I was looking for a best-guess assessment based on the current state of the science, rather than expecting further research (that may not have been clear). Although FoE are resource-strapped, they do have access to experts who should be able to help with this.

For simplicity, I decided to focus on human health with this question. Agree with you though the potential environmental impact is an important – and possibly more complex – issue.

And despite my question here, I should note that I recognize and appreciate the role that FoE and other organizations like this play in asking tough questions, and getting people to think about the consequences of their actions.

Cheers – Andrew

3 Andrew Maynard June 15, 2010 at 8:35 am

Georgia Miller and Ian Illuminato of Friends of the Earth have kindly responded to this post – their response can be found here: http://2020science.org/2010/06/15/just-how-risky-can-nanoparticles-in-sunscreens-be-friends-of-the-earth-respond/

4 Sharron Clemons December 21, 2010 at 3:05 pm

[...] the Earth (FOE) guest bloggers’ (Georgia Miller and Ian Illuminato) response to his posting (Just how risky could nanoparticles in sunscreens be?) where he challenged them over some of the claims in their literature.  His reflections on the FOE [...]

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