Long Live Science: Sunscreen’s Invisible Chemistry
With summer fast approaching, there’s no better time to discuss sunscreen.
Americans for the most part understand that sun exposure is a major risk factor for skin cancers, the most common form of cancer. But do we truly appreciate the strength of sunscreen prevention?
According to a study published in the Journal of the American Academy of Dermatology, only 14.3 percent of men and 29.9 percent of women reported regularly wearing sunscreen when in the sun for more than an hour.
That sounds like a fail grade to me. Maybe it’s time we had a science lesson to appreciate the chemistry and function of sunscreen. How does it protect our skin from ultra violet (UV) radiation?
What are we up against?
The average temperature of the sun is 5,778 Kelvin, which equates to approximately 9,941 degrees Fahrenheit. That’s much hotter than any beach day I know. Yet the small bottle we forget to pack can trump the sun’s immense strength.
UV radiation can be divided into three categories: UVC, UVA and UVB. UVC rays are not a threat because they are absorbed by ozone in the atmosphere before they reach Earth’s surface. UVA and UVB on the other hand, can readily cause skin damage.
UVA rays are responsible for approximately 95 percent of UV radiation from the sun. The radiation penetrates deep into the skin causing wrinkling and premature aging. The strength of UVA radiation can also generate reactive oxygen species, cumulatively known as oxidative stress, a known risk factor for skin cancer.
UVB radiation is responsible for the remaining five percent of the UV radiation reaching Earth. It causes your skin to produce melanin – the pathway that creates a tan. However, UVB also generates sunburn and direct DNA damage. UVB rays have historically been considered dangerous and most early sunscreens were formulated to protect solely against them.
Thankfully, through science, we now understand the harm of UVA and UVB rays. We have also successfully engineered chemical solutions that shield our skin against the UV spectrum.
What are the solutions?
So how does sunscreen chemically work? Inorganic compounds, including titanium dioxide and zinc oxide, form a physical barrier that reflects and scatters UV radiation.
Organic compounds are able to absorb photons of UV light and dissipate the energy in the form of heat. The variation in structure leads to absorption of different UV wavelengths to ensure comprehensive protection.
The chemical breakdown of sunscreen also explains why it has to be reapplied. Some organic chemicals are photostable, which means they will not break down when exposed to UV light. However, they will slowly break down as they absorb more and more UV radiation. Other chemicals can help delay the breakdown, but reapplication is inevitable.
The more obvious reason for reapplication is that even sunscreens that claim to be water resistant will eventually be washed off, sweated away, or licked off by the dog. To protect consumers, regulations now require sunscreens to specify how long they are water resistant.
Slap on the science
If the chemical-talk has you concerned, don’t worry. Each sunscreen undergoes a rigorous testing product to ensure the chemicals are not harmful. This means there is no reason to not apply this magic alchemy barrier. We need to be willing to say goodbye to the bronze god(dess) look and take care of our body’s largest organ. It doesn’t matter if it’s a beach day or a rainy day, protect your skin and wear sunscreen.