1. There is no consensus on whether sunscreens prevent cancer. The fact is, after reviewing the scientific research, the National Cancer Institute concluded that there is no evidence that sunscreen reduces melanoma. “It is not known if protecting skin from sunlight and other UV radiation decreases the risk of skin cancer. It is not known if non-melanoma skin cancer risk is decreased by staying out of the sun, using sunscreens, or wearing long sleeve shirts, long pants, sun hats and sunglasses when outdoors” (NCI 2009) Skin cancer rates have actually gone up with increased use of sunscreen.
2. There’s some evidence that sunscreens might increase the risk of the deadliest form of skin cancer for some people. The fact is, studies have shown that people who regularly use sunscreen have reduced risk of squamous cell carcinoma, a slow growing tumor that is easily treatable, but studies have also shown that people who regularly use sunscreen have a significantly increased risk of melanoma, the deadliest form of skin cancer. It is theorized that the reason that regular sunscreen use actually increases your risk of melanoma is because it blocks your body's ability to produce vitamin D, which protects it.
3. There are more high SPF products than ever before, but no proof that they’re better. Studies have found that people using higher SPF sunscreens had even higher exposure to harmful UV rays, not less, so "The user is left with a burn and a significantly higher “body burden” of sunscreen chemicals."
4. Too little sun might be harmful, reducing the body’s vitamin D levels. Vitamin D deficiency is of epidemic proportions, and it has risen directly with increased usage of sunscreens, which inhibit the body's natural ability to produce it. According to the research, 7 in 10 children in the US are now vitamin D deficient. Among other things, D protects against a number of cancers.
5. The common sunscreen ingredient vitamin A may speed the development of cancer. According to an FDA study, vitamin A greatly speeds the development of skin cancer, and 41% of all commercially available sunscreens use it.
6. Free radicals and other skin-damaging byproducts of sunscreen. "Sunscreens can help reduce UV-related free radical damage by diverting the radiation from the skin, but the ingredients themselves can release their own free radicals in the process. When the sunscreen molecules absorb UV energy, diverting it from the skin, the molecules dispel this excess energy by releasing free radicals."
7. Pick your sunscreen: nanomaterials or potential hormone disruptors. The hormone disruptors in many commercially available sunscreens are a serious problem. Nanoparticles in mineral (titanium and zinc) can pose dangers as well, but according to the EWG, they are a much safer choice.
8. Europe’s better sunscreens. American commercial sunscreens are on the whole much worse at UVA protection.
9. The 33rd summer in a row without final U.S. sunscreen safety regulations. The FDA has been floundering on guidelines for decades. Laboratory studies indicate that some common sunscreen ingredients are seriously toxic, and even cause pre-cancerous cell damage. A study (Schlumpf 2008) found the presence of several toxic sunscreen ingredients (octylmethoxycinnamate, octrocrylene, oxybenzone, 4-MBC, and Padimate O) in women's breast milk, which raises serious concerns about toxicity to the gestating fetus and breast feeding baby.
Ultimately, you have to make the most informed decision that you feel is right for you and your family. I'm never one to tell folks what to do. I simply have examined the information available and come to my own conclusions about the safe use of sunscreen.