Sunscreens: are they all created equal?

Summer is upon us. With nicer weather comes the opportunity to spend more time outside- to enjoy having a drink on an outdoor patio, trips to the beach, and long walks to nowhere- all under the warmth of the sun. And all of this means that for many, it’s time to start regularly slathering oneself with sunscreen.

When we enjoy a bright and sunny day, we really are only recognizing a small part of the solar radiation reaching us. In actuality, these solar rays span a wide spectrum of which visible light only accounts for a small part, sandwiched between infrared and ultraviolet (UV-A and UV-B) radiation. While new research shows that infrared, visible, and ultraviolet rays all cause damage to skin, ultraviolet radiation is the main culprit to be avoided. If these three types of solar radiation could be compared to a group of teens up to no good, ultraviolet would be the ringleader instigating all the trouble-making, whereas visible and infrared would be basically harmless by themselves. It is UV-A and UV-B radiation that are largely responsible for damage to human eyes and skin, with the consequences of repeated exposure including rapid ageing, vision loss, and skin cancer. Luckily, polarized sunglasses are effective at protecting the eyes, while sunscreen helps avoid negative effects to the skin, meaning we aren’t doomed to hide ourselves away from beautiful weather.

Solar radiation is like a rainbow, with two invisible bookends. Visible light accounts for the the colours that the human eye can detect, while ultraviolet is to the left, next to visible violet, and infrared can be found to the right, next to visible red.

Sunscreens can generally be classified into two categories: mineral and chemical. Mineral sunscreens are formulated with solid inorganic particles, the most common of which are zinc oxide or titanium dioxide. These minerals are white in colour and reflect the sun’s rays in the same way a white t-shirt reflects light and helps keep you cool. Because of this, they can be pictured as a physical barrier to sun damage. Mineral ingredients are generally less irritating to sensitive skin and offer better protection for a wider range of solar radiation (otherwise known as broad spectrum UV-A and UV-B protection), but many formulations have become notorious for the characteristic white cast that they leave on skin. Zinc oxide has also been signaled for environmental damage and titanium dioxide has been shown to be unsafe to inhale, so should be avoided in sunscreen sprays.

The white colour of this sunscreen is likely due to zinc oxide or titanium dioxide, two of the most common ingredients in mineral sunscreen.

Chemical sunscreens are made with organic molecules, which means that they have a carbon-based skeleton (not that they are made without pesticides, as is the case with organic food). These ingredients do not occur naturally and are produced by chemists in a lab setting. Because they are man-made there is a wider variety of these ingredients available in commercial products, and they can have other interesting desirable  properties such as no visible colour. The most common molecules used in chemical sunscreens are oxybenzone, avobenzone, octinoxate, and ecamsule, which absorb harmful solar radiation and convert it into heat, therefore protecting against damage. However, due to their synthetic nature they have been reported to be irritating to some, aren’t recommended to be used on children as they absorb into the skin, and some of these molecules also have some environmental concerns.

To simplify, let’s discuss each of these aforementioned ingredients. Zinc oxide is great for sensitive skin, has antibacterial properties, is highly stable, and effectively prevents against sun damage. However, it poses acute and chronic hazards to the aquatic environment and may not actually prevent sunburns. Titanium dioxide is another broad-spectrum mineral agent, great for sensitive skin and approved for use on children, but is suspected of causing cancer when inhaled, so it should be avoided in sunscreen sprays. As for chemical ingredients, oxybenzone has recently been banned in many areas due to its extremely toxic nature towards aquatic life, especially coral reefs. However, it is highly effective against sun damage and burns. Avobenzone lacks stability and has been signaled to potentially harm aquatic life, but is effective against burns and sun damage when combined with other ingredients. The same can be said of octinoxate, and for this it has been recently banned in Hawaii. Ecamsule (otherwise known as Mexoryl SX) is classed as not hazardous to human or environmental well-being, but is only effective against UV-A rays and shouldn’t be used alone.

As a final piece to the puzzle, we have to talk about the sun protection factor of sunscreens, or SPF. Simply put, SPF indicates how much more time it will take for skin to be damaged or burned when using that product when compared to using nothing at all. For example, if your bare skin burns after 10 minutes and you apply a sunscreen that boasts SPF 15, it will take 15 times longer for your skin to be damaged or burned, or 150 minutes. Although some products claim to provide SPF 60, the SPF rating system has only proven to be reliable up to SPF 50. These ratings are dependent on the ingredients used and their concentrations in the formula, how stable the product is, and how well it stays on your skin throughout various activities.

All in all, it’s pretty evident that a lot of factors need to be considered when buying a sunscreen. Broad spectrum formulations that provide protection against UV-A and UV-B rays are best, just as SPF 50 will likely provide better protection than SPF 15. When it comes to ingredients, consider if the product is in cream or spray form, if it will be used on adults or children, and the sensitivity of your skin. Finally, whenever possible, avoid ingredients known for their negative effects on marine life, such as zinc oxide, oxybenzone, and octinoxate. It might take a bit of work to find the products that strike this balance- but once you do, your skin and the environment will thank you.

Advice to consumers:

  • Look for broad spectrum sunscreens that provide UV-A and UV-B protection
  • Try to avoid zinc oxide, oxybenzone, and octinoxate-based formulations because of their known toxicity towards aquatic ecosystems
  • Avoid using chemical sunscreens on children
  • Avoid titanium oxide in sunscreen sprays
  • No matter the formulation, use more than you think is necessary and reapply often!

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