In sunny summer days use of sunscreen is
common for protection from UV rays of sun. From many years nanoparticles
are used in sunscreens. Excess use sunscreen raises some health related issues
in past few years too. Largest number of case of skin cancer (Melanoma and
Non-melanoma) reported in Australia.
How
sunscreen works on our skin, what is the role of nanoparticles in sunscreen,
are really they hazardous for our skin? What
our scientific research reports explain let’s discuss.
How sunscreen works on our skin
Two type ingredients are used in sunscreens.
First one is chemical absorbent which absorb UV rays and protect the skin, but
it can be allergic. Second one is nano
size physical blocker as Zinc oxide and Titanium dioxide. They are more effective
as compare to absorbent and have no any adverse effect on skin.
Nanoparticles
Nanoparticles are too small in size their
dimension in range of 1-100nm (one nanometer is one billionth part of the meter).
Depending of dimensions nanoparticle categorizes as zero-dimension eg. Cluster,
one-dimension (1D) eg. Nanotube,
two-dimension (2D) eg. Film, three-dimension (3D) eg. Polycrystal. Smaller in size and higher in surface area to
volume ratio, nano particle shows better chemical and physical properties than
their bulkier one. Nanopaticles have several potential applications in field of
medicine, biomedical, drug delivery, electronics, optics and as catalyst.
Health related concern arise because of
skin cell penetration power of nanoparticles and still unknown of the effect of
their interaction with internal biological systems.
Are nanopaticles hazardous for skin?
Therapeutic Goods Administration (TGA) is
an Australian Government body which regulate all issues related to sunscreen
ingredients and their formula. In 2013 TGA conducted a review of all
scientific reports, article related to use and effect of nanoparticle in
sunscreen. Their report suggest that Zinc oxide and Titanium dioxide do not
reach to the viable cells of skin, rather stay on the upper surface of the skin
which is not composed of viable cells.
Some more survey has been done recently in
Australia. In 2014 the Cancer
Council of Australia study and reported that human immune cells
(macrophages) when exposed in Zinc oxide nanoparticle; macrophages absorbed nanoparticles and broken down them.
So these nanoparticles did not reach in human blood. If in any case they
reached in the blood our immune system make them ineffective. So it can conclude that
presence of nanoparticles in sunscreen does not create any health risk in
human. Their regular use is safe.
These nanoparticles tend to aggregate and form
agglomerates. Agglomerates are bundle of nanoparticles. These agglomerates are
big in size but they remain their nanoparticle properties. These agglomerates
can break easily but require some energy which would not come from normal use
of sunscreens. Some laboratory tested
their own sunscreen which initially contains nanoparticles but they aggregate due
to agglomeration.
Manufacturers view:
Manufacturers suggest that agglomerates above
100 nm not call nanoparticle while other aruge on that and suggest while they
aggregates but they retain their identity and nanoparticle properties. Some manufacturers use coating agents to
avoid the agglomeration because coated naoparticles cannot agglomerates. Coated nanoparticles are less reactive than
non-coated nanoparticle, so it they could not penetrated the skin and damage
the skin.
Scientific view:
According to scientific view nanoparticle
can penetrate the outer dead layer of skin while they cannot damage the inner
layer of skin. Another Australian study report that no any damage have been
occur when nanoparticles mechanically penetrated (by broken skin cause by acne,
wound etc) inside inner layer of skin. It was still unclear that penetrated zinc
oxide is actually nanoparticle or Zn ion which had dissolved. As we know Zn ion
is essential content of human body and cannot harm. It is possible that if
nanoparticle penetrates inner layer of skin, due to their insufficient amount
not show any adverse impact on human body.Study of TGA and cancer council of
Australia also show that presence of nanoparticle in sunscreen does not show
any adverse effect on skin. While still not very clear idea about any adverse
effect of nanoparticle Australian “Nano-suncreen” brand has decides to change
their sunscreen formulation to make them nano free.
It is an interesting topic of further
research for scientists. Further research is required on What is the effect of
nanoparticle on dermal adsorption at different natural conditions?, effect of
their size on it, what is the exposure time limit etc. At present CSIRO and
Macquarie University of Australia are intensely involved in this program. Until
any clear result come out, regulatory authorities should required making it mandatory
for manufacturer to show warning disclosure on packet of product. Special disclosure
should be for use over cuts, acne and mainly for children.
