Sunscreens were first regulated by the FDA in 1978¹, before strict regulations around topicals were in place. In recent decades, additional regulations were put in place by the FDA that requires manufacturers to do additional toxicological testing if their products could be absorbed into the body at levels about 0.5 ng/ml. These toxicological tests included testing for carcinogenic behaviour or negative reproductive effects in humans.
The problem is that since the sunscreens existed before the new regulations, they were grandfathered in, and no further testing was needed. The FDA had been urging sunscreen makers to do additional testing of their compounds for years, but to no avail, since the companies had no incentive to do so.
Eventually, the FDA took matters into their own hands and conducted a study 2019 that examined the blood concentrations of common sunscreen chemicals after topical application. They tested oxybenzone, avobenzone, octocrylene, and ecamsule in concentrations normally found in sunscreen.
They found that all the chemicals tested exceeded 0.5 ng/ml within 2 hours of application – and exceeded them by ~150 times. The substances accumulated as well – within 4 days of continuous application, the levels of oxybenzone exceeded 0.5 ng/ml by 450 times.
To summarize, there are chemicals in sunscreens that are known to enter the bloodstream in relatively high concentrations, and there hasn't been proper toxicological studies on them.
You probably don't want this in your bloodstream
Please take a look at some evidence for the harm of oxybenzone may cause, compiled from veteran toxicologist Joe DiNardo.³
If you will note the last evidence – oxybenzone is causing havoc in aquatic systems. Hawaii is now banning sunscreens containing oxybenzone starting in 2021, because the chemical is having deleterious effects on the coral reef.⁴
Another oft forgotten point is that most commercial sunscreens don't protect against UVA radiation.
The sun emits two types of ultraviolet light: UVA and UVB. Both of them do damage. UVB, which is about 5% of ambient sunlight, is what's responsible for you getting sunburn, redness, and also your production of Vitamin D. UVA, which is about 95% of ambient sunlight, travels deeper in the dermal layer than UVB. Because it travels so deep, it does not contribute to sunburn, but it is still responsible for skin aging. Both UVB and UVB will create Reactive Oxygen Species (ROS), which are unstable molecules that can cause damage to DNA.
The UVA rays are considered sun's silent killers because unlike UVB, you don't feel the effects of UVA damaging your skin. The only sunscreens which protect against UVB and UVA are called "broad spectrum" sunscreens.
The SPF rating sunscreens is only used to measure the "sun protection factor" against UVB radiation, but not UVA radiation. Unless you're using a broad spectrum sunscreen, you're preventing your body from producing the Vitamin D it needs, while still letting UVA rays penetrate the dermal layer.
This seems quite ineffective at best, and harmful at worst. Vitamin D deficiency is well known to contribute to a wide variety of chronic illness, infectious disease, and overall mortality. 40% of Americans have a Vitamin D deficiency.⁵
There's a reason why your skin turns red under the sun. It's a warning mechanism to find shade and get out of the sun. By only blocking UVB and not UVA with commercial sunscreen, you're depriving yourself of this warning mechanism.
If you want to stay safe in the sun, but don't want to use commercial sunscreens you have a few options.
1. Cautious Method: Zinc Oxide
Zinc Oxide has been around forever. It's deemed "Generally Recognized as Safe" (GRAS) by the FDA.⁶
It is broad spectrum and protects against both UVA and UVB rays.
You can easily find an SPF 30 sunscreen and reapply every 2 hours, as most dermatologists recommend. You don't really need an SPF 60 sunscreen, see the chart below.
2. Lubricious Method: Coconut Oil + Clothing
If you believe that sunlight is more beneficial than harmful in any quantity before redness, as I do, you can take the more libertine approach.
Coconut Oil has an SPF rating somewhere from 1 - 5. It helps a little in the protection of UV rays and moisturizes your skin. The vitamin E content should help prevent against Reactive Oxygen Species creation. Apply liberally before going out in sunlight. If you find you need to be outside longer than you skin can handle, clothe yourself.
A caucasian person needs only about 15-20 minutes of sunlight around midday for optimal vitamin D production. Make sure its midday, because UVB rays cannot penetrate the atmosphere if the sun is not high enough in the sky. This is why people living above 37 degrees latitude (Atlanta) get almost no UVB rays (and subsequently Vitamin D) in the wintertime.