Here a big list of studies and articles about the negative health effects of sunscreen:
Note: Article by a medical doctor on why most common sunscreens aren’t so healthy.
The Relation Between Sunscreen Layer Thickness and Vitamin D Production After Ultraviolet B Exposure: A Randomized Clinical Trial (2012)
Conclusion: 37 light-skinned people applied varying thicknesses of SPF 8 sunscreen to their upper body and were exposed to a standard dose of UVB irradiation four times over a two week period. Vitamin D levels were measured before and after. The study found that those who were applying the thickest application of the sunscreen (which is also the recommended dose) experienced an insignificant increase in their vitamin D levels. Thinner applications of sunscreen resulted in better vitamin D production, with vitamin D levels increasing exponentially for the lowest doses of applied sunscreen.
Note: Article by Medical Doctor Joseph Mercola on the dangers of many sunscreen products.
Liquid Chromatographic Assay for Common Sunscreen Agents: Application to In Vivo Assessment of Skin Penetration and Systemic Absorption in Human Volunteers. (2004)
Conclusion: Sunscreen chemicals get absorbed by your body and make their way into your bloodstream. “Results from the preliminary clinical study demonstrate significant penetration of all sunscreen agents into the skin.”
Active Ingredients in Sunscreens Act as Topical Penetration Enhancers for the Herbicide 2,4-Dichlorophenoxyacetic Acid. (2004)
Conclusion: Sunscreen chemicals have been proven with blood tests to be “dermal penetration enhancers,” causing an increased absorption by the body of other harmful chemicals such as herbicides, pesticides, and bug sprays.
Systemic Absorption of the Sunscreens Benzophenone-3, Octyl-Methoxycinnamate, and 3-(4-Methyl-Benzylidene) Camphor After Whole-Body Topical Application and Reproductive Hormone Levels in Humans. (2004)
Conclusion: Urine tests have found that sunscreen chemicals can be absorbed into the body, making their way into your bloodstream.
Effects of Active Sunscreen Ingredient Combinations on the Topical Penetration of the Herbicide 2,4-Dichlorophenoxyacetic Acid (2003)
Conclusion: “A number of commercially available [sunscreen] formulations have been shown to enhance the transdermal penetration of the herbicide 2,4-dichlorophenoxyacetic acid (2,4-D). Most of the active ingredients used in these compounds can individually act as penetration enhancers.” Sunscreens increase your absorption of other harmful chemicals you’re exposed to, such as bug sprays.
Conclusion: Having sunscreen on you increases absorption of harmful pesticides through your skin.
Sunscreens, Skin Photobiology, and Skin Cancer: The Need for UVA Protection and Evaluation of Efficacy (2000)
Conclusion: Sunscreens prevent burning to the surface of the skin, but they do not prevent damage to the inner, deeper layers of skin. For this reason, sunscreens might actually be causing more harm by allowing people to spend more time in the sun than they otherwise would which leads them to accumulate more damage to their inner layers of skin over time.
Note: Mother Jones article providing an overview of the evidence showing that common sunscreens do not typically provide the amount or type of sun protection we’re told they do, they actually cause more harm in the full analysis, and most of the medical experts urging us to use it are either paid off by the cosmeceutical-industrial-complex somehow or they’re just lazy and repeating talking points they haven’t actually investigated at all.
Chronic Sunscreen Use Decreases the Concentration of 25-Hydroxyvitamin D: A Preliminary Study (1998)
Conclusion: Vitamin D levels were measured in 20 long-term users of PABA-containing sunscreen and compared with the vitamin D levels of 20 age-matched controls who don’t use sunscreen. The average vitamin D level of the sunscreen group was a very poor 16 ng/ml, whereas the control group had a much better (and more than double) level of 36 ng/ml. The sunscreen group also had two cases of severe deficiency, but the control group had no cases of severe deficiency.
The Effect of Regular Sunscreen Use on Vitamin D Levels in an Australian Population. Results of a Randomized Controlled Trial (1995)
Conclusion: 113 people age 40 or older were given either an SPF 17 sunscreen or a placebo cream to use daily during an Australian summer. Vitamin D levels were measured before and after and both groups actually had the same vitamin D level increase. So maybe if you’re using a weaker sunscreen sparingly and still get a lot of time out in intense sunlight, you’re okay.
Note: New York Times article reporting on research findings showing sunscreen does not protect against melanoma skin cancer.
Note: Article arguing that sunscreens may actually increase the risk of melanoma skin cancer by allowing people to spend more time in the sun than they would without sunscreen and sunscreens blocking UVB (which gives you cancer-preventing vitamin D), but not UVA which causes deeper skin damage.
Conclusion: Sunscreens reduce vitamin D production.
Note: 1980 British Medical Journal article pointing out that many chemicals found in cosmetic and sunscreen products aren’t healthy.