Some recent scientific studies show the unexpectedly complex medical effects of using sun screen. Carcinogenic ingredients are just one reason to study these products carefully.

1. Medical Science is difficult and messy
Dave Shafer

2. It can be hard to distinguish
cause and effect from constant
conjunction. A rooster that
crows every morning at dawn
may think that he makes the
sun come up, since they always
happen together. There is
much in medicine that is like
that. Assumed cases of cause
and effect may turn out to be
nothing of the kind.

3. I have a sort of medical science joke – that sun
screen lotion causes skin cancer. After all, since I
was a kid the incidence of skin cancer is way up now
and so, also, is the use of sun screen. I assumed until
recently that this was a rooster/sunrise kind of joke.

4. Then I read something
interesting recently – that
cycling head injuries are
way up and so also is the
use of bike helmets. There
are several reasons for this
connection but one is that
people wearing a helmet
feel more safe and hence
engage in more risky
cycling. So there is a sense
in which bike helmets
cause head injuries.

5. In the old days, like when I was young, people
would have enough sense at the beach to get out
of the sun after a while. Now, with super-duper
sunscreen blockage being advertised, people
assume that they are safe and spend much more
time than they should in the sun. The coverage
can be incomplete, may wear off, may need to be
renewed, etc.
Who among
us is going
to be this
thorough?

6. So, just as the increased use of bike helmets has partly
caused more cycling head injuries by making people feel
safer, the increased use of sun block lotion has increased
the incidence of skin cancer. People stay out in the sun
much too long, and are careless with incomplete coverage.
Then I found out that it is more complicated than this
and that there are ingredients in most sun block brands that
may actually cause cancer. One is retinyl palmitate, which
has been shown to cause tumors in mice. See this 2013
report here from the NIH.
http://ntp.niehs.nih.gov/ntp/htdocs/lt_rpts/tr568_508.pdf
Some early ingredients of sunscreen have now been banned
but retinyl palmitate is still common. New ingredients like
nanoparticles of titanium dioxide are possibly carcinogenic
and spray sunscreen uses a gas that is most definitely
carcinogenic if breathed. The FDA does not regulate these
products at all.
Other chemicals used have been
shown to be hormone disrupters
and should probably not be used
on children.

7. Even a very low level of sun screen rating blocks almost all of the sun’s vitamin D producing
ability. There are many bad consequences of a vitamin D deficiency and unless you are big on
fish oil the easiest way to get your daily dose of vitamin D is some time in the sun. Many kids
today have vitamin D deficiency, partly due to parents having a phobia about any sun exposure.
A study by the American Cancer Society showed that decreased exposure to the sun results in increased
cancers – just the opposite of conventional wisdom. Here is the conclusion of one report.
CONCLUSIONS:
The results of the current study demonstrate that much of the geographic variation in cancer mortality rates in the U.S. can be
attributed to variations in solar UV-B radiation exposure. Thus, many lives could be extended through increased careful
exposure to solar UV-B radiation and more safely, vitamin D3 supplementation, especially in nonsummer months.
Copyright 2002 American Cancer Society.

8. •© 2008 American Society for Clinical Nutrition
Vitamin D deficiency: a worldwide problem with health consequences1,2,3,4
1.Michael F Holick and
2.Tai C Chen
+ Author Affiliations
1.1From the Department of Medicine; Section of Endocrinology, Nutrition, and Diabetes; Vitamin D, Skin and Bone Research
Laboratory; Boston University Medical Center, Boston, MA
Next Section
Abstract
Vitamin D deficiency is now recognized as a pandemic. The major cause of vitamin D deficiency is
the lack of appreciation that sun exposure in moderation is the major source of vitamin D for most
humans. Very few foods naturally contain vitamin D, and foods that are fortified with vitamin D are
often inadequate to satisfy either a child's or an adult's vitamin D requirement. Vitamin D deficiency
causes rickets in children and will precipitate and exacerbate osteopenia, osteoporosis, and fractures
in adults. Vitamin D deficiency has been associated with increased risk of common cancers,
autoimmune diseases, hypertension, and infectious diseases. A circulating level of 25-hydroxyvitamin
D of >75 nmol/L, or 30 ng/mL, is required to maximize vitamin D's beneficial effects for health. In
the absence of adequate sun exposure, at least 800–1000 IU vitamin D3/d may be needed to achieve
this in children and adults. Vitamin D2 may be equally effective for maintaining circulating
concentrations of 25-hydroxyvitamin D when given in physiologic concentrations.

9. The conclusion here is that even with something
as simple as using sunscreen lotion it is very
difficult to unravel what is cause and effect, what
are the risks and benefits, and what data and
advice can be trusted. Sunscreen products are a
huge market and advertising is certainly not
going to give you accurate information about
risks.
The current controversy about vaccines is
even more complex to unravel. What is certain is
that good hard science is needed to bring into the
light all the risks and benefits of medical
procedures so that both doctors and the public
can make informed decisions. Unfortunately it is
very expensive to do the kinds of controlled
studies that are needed and so they are rarely
done. The result is that huge numbers of people
use sun screen (just one example) and get
vaccines for years before good science is done.

10. Suppose there was a pill that you
could take that reduced your
chances of being hit by lightning by
50% (admittedly a ridiculous idea).
And suppose that there were some
rare bad side effects of that pill.
Would you take the pill after you
realize that the chances of your
getting hit by lightning are
extremely low, so that a 50%
reduction in your risk is hardly
worth it? Especially if the rare bad
side effects are more common than
people being hit by lightning? That
is the situation with some, but not
all, vaccines. It is important to have
this data in order to make informed
decisions.
In today’s world more people are injured by polio vaccine
than are injured by polio. This is one extreme of the efficiency
spectrum and both situations are extremely rare.

11. The main take-away message here is
that we as consumers need to look out for
our own health – the FDA and big
pharmaceutical companies are not going
to do it for us. Europe has banned some
components of medicines that are
common here in the US. Russia has
kitchen microwave appliance microwave
radiation emission standards that are very
much tighter than what is required here.
You do not have to be paranoid to feel
that it is good to be skeptical about how
much science is behind claims about
health, nutrition, exercise, etc.