[From 2020Science] The Environmental Working Group
(EWG) – a US-based non-profit organization committed to using public
information to protect public health and the environment – has just
released what is probably the most comprehensive evaluation to date of
the safety and effectiveness of using titanium dioxide and zinc oxide nanoparticles in sunscreens. And their conclusion?
On balance, EWG researchers found that
zinc and titanium-based formulations are among the safest, most
effective sunscreens on the market based on available evidence.
In other words, not only are zinc oxide
and titanium oxide nanoparticle-based sunscreens OK, but they are safer
and more effective than many non nanotechnology-enabled sunscreens.
What makes this statement so startling
is that EWG is not known for treating regulators and industry with kid
gloves. This is how the organization describes it’s way of working:
Our research brings to light unsettling
facts that you have a right to know. It shames and shakes up polluters
and their lobbyists. It rattles politicians and shapes policy. It
persuades bureaucracies to rethink science and strengthen regulation.
EWG is about as far as you can get from
a bunch of industry lackeys. Yet here they are endorsing one of the
more controversial products of nanotechnology.
For the past few years, the safety of
using nanometer-scale particles in sunscreens has been hotly debated.
As manufacturers have turned increasingly to nanoscale mineral
UV-blocking agents in place of more conventional chemicals, speculative
questions over whether the nanometer-scale particles of titanium
dioxide or zinc oxide being used could penetrate through the skin and
harm people have been asked. In the absence of conclusive
safety-focused research, some groups have suggested that
nanoparticle-based sunscreens should be avoided in favor of more
conventional products, where there we have a clearer idea of the
possible risks. In 2007, Friends of the Earth published “A consumer guide for avoiding nano-sunscreens,” kicking off with:
Sun worshippers beware. While
slathering up with sunscreens to block dangerous ultra-violet (UV) rays
you may be exposing yourself to a new danger. Sunscreen manufacturers
are adding nanoparticles to sunscreens to make sun-blocking ingredients
like titanium dioxide and zinc oxide rub on clear instead of white.
These nanoparticles are being added without appropriate labeling or
reliable safety information.
Even EWG admit that their researchers
were skeptical about the use of nanoparticles in sunscreens, and
thought the organization would end up advising against their use.
Over the past few years, there has been
a growing body of published data addressing the effectiveness and
safety of nanoparticle-containing sunscreens. EWG researchers ploughed
through nearly 400 studies in their quest to assess what the upsides
and downsides might be for consumers. Importantly, they also compared
these data to what is known about conventional UV-blocking agents like
octinoxate and oxybenzone.
The result is a comprehensive, robust
analysis that wouldn’t be out of place in a peer reviewed scientific
journal. The conclusions are highly relevant to consumers concerned
over which sunscreens to use, companies paranoid over how they present
their products, and governments wondering how to regulate
nanotech-enabled sunscreens. The report states:
Our study shows that consumers who use
sunscreens without zinc and titanium are likely exposed to more UV
radiation and greater numbers of hazardous ingredients than consumers
relying on zinc and titanium products for sun protection. We found that
consumers using sunscreens without zinc and titanium would be exposed
to an average of 20% more UVA radiation — with increased risks for
UVA-induced skin damage, premature aging, wrinkling, and UV-induced
immune system damage - than consumers using zinc- and titanium-based
products. Sunscreens without zinc or titanium contain an average of 4
times as many high hazard ingredients known or strongly suspected to
cause cancer or birth defects, to disrupt human reproduction or damage
the growing brain of a child. They also contain more toxins on average
in every major category of health harm considered: cancer (10% more),
birth defects and reproductive harm (40% more), neurotoxins (20% more),
endocrine system disruptors (70% more), and chemicals that can damage
the immune system (70% more) (EWG 2007).
We also reviewed 16 peer-reviewed
studies on skin absorption, nearly all showing no absorption of
small-scale zinc and titanium sunscreen ingredients through healthy
skin. In a 2007 assessment the European Union found no evidence of
nano-scale particles absorbing through pig skin, healthy human skin, or
the skin of patients suffering from skin disorders (NanoDerm 2007).
Overall, we found few available studies on the absorption of nano-scale
ingredients through damaged skin, but nearly all other sunscreen
chemicals approved for use in the U.S. also lack these studies.
In contrast to zinc and titanium, the
common sunscreens octinoxate and oxybenzone absorb into healthy skin -
in large amounts according to some studies. These 2 sunscreens can
cause allergic reactions, can lead to hormone-driven uterine damage,
and can act like estrogen in the body, raising potential concerns for
*** cancer.
On balance, EWG researchers found that
zinc and titanium-based formulations are among the safest, most
effective sunscreens on the market based on available evidence. The
easy way out of the nano debate would be to steer people clear of zinc
and titanium sunscreens with a call for more data. In the process such
a position would implicitly recommend sunscreen ingredients that don’t
work, that break down soon after they are applied, that offer only
marginal UVA protection, or that absorb through the skin.
EWG acknowledge that more research is
still needed, alongside effective oversight, to ensure that
nanotech-enabled sunscreens are as safe as possible. But the key
message is that the current balance of evidence supports their use as a
safe and effective alternative to more conventional sunscreens.
I cannot emphasize enough how important
this report is. The analysis is credible and the conclusions drawn are
supported by the current state of the science. It should reduce
consumer concerns over using nanoparticle-based sunscreens, and allow
them to make informed decisions that will result in better UV
protection. It should also encourage companies developing and selling
nanoparticle-enabled sunscreens to stop obscuring the fact – either by
avoiding any mention of nanoparticles, hiding behind silly euphamisms
alike “micronized,” or coming up with elaborate explanations of why
their product doesn’t actually contain any nanoparticles. These are
good products using an effective technology, and companies shouldn’t be
shy to let people know!
That said, there is still work to be
done. There are gaps in our understanding of how titanium dioxide and
zinc oxide nanoparticles behave on the skin and in the environment that
it would be good to fill. Approaches to testing these materials need
to be fully evaluated. And regulators need to clarify the rules
concerning the safe use of these materials.
Given what still isn’t known, EWG
cautioned against the use of nanoparticles in cosmetics at the moment,
where they are not being used to protect the wearer’s health. But when
it comes to protecting the skin the organization was clear –
nanoparticle-based sunscreens.
End Notes
The full EWG report on “Nanotechnology & Sunscreens” can be read here.
This is part of a larger review of sunscreens, which is accessible here.
Something not covered in the EWG
report is nanoparticle agglomeration. Some companies have claimed
that, while the basic size of titanium dioxide and zinc oxide particles
they use is in the range of 1 – 100 nm, they form much larger
agglomerates in the products and should therefore not be considered
“nanoparticles.” While this may be the case for some products, it
isn’t universal, and there are still questions over whether large
agglomerates could disaggregate when applied to the skin. However,
given the EWG’s findings and conclusions, the question of agglomeration
doesn’t seem to be that important from a consumer’s perspective.
One concern over the use of
titanium dioxide and zinc oxide nanoparticles in sunscreens is that
these materials are photoactive, and could become more harmful when
exposed to sunlight. As the EWG report notes, most manufaturers treat
the nanoparticles to supress their photoactivity. Howere, there is some evidence
that products containing photoactive particles could still be entering
the market. Whether this is important from a health perspective is
unknown, although the indications are that it probably isn’t a
significant concern when the particle-containing sunscreens are
appolied to healthy skin.