Conventional guidance to avoid unprotected sun exposure at all costs has likely done public health a great disservice. The American Academy of Dermatology, for example, stresses daily use of sunscreen to prevent skin cancer, regardless of weather conditions or skin pigmentation — two factors that simply cannot be overlooked when weighing the risks and benefits of sun exposure and sunscreen use.
A direct result of this blanket recommendation is widespread vitamin D deficiency, which we now know is a risk factor for a wide variety of cancers and many other chronic diseases. Your vitamin D level even influences your risk of skin cancer.
For example, a 2010 study found elderly men with the highest quintile of vitamin D had a 47% lower risk of non-melanoma skin cancer compared to those with the lowest levels. Research has also shown vitamin D deficiency worsens your prognosis if you have metastatic melanoma.
The science is not cut and dry, however. You can certainly find studies to make an argument for both sides of the issue, i.e., that sun exposure can increase your risk of skin cancer, or lower it. A key argument that tends to get lost in the discussion, though, is the importance of vitamin D for overall health and disease prevention.
Your Body Absorbs Toxins From Sunscreens
In 2019, the U.S. Food and Drug Administration published a pilot study showing four commonly used active ingredients in sunscreen — avobenzone, oxybenzone, octocrylene and ecamsule — are absorbed into your blood at levels that could potentially pose health risks.
Twenty-four participants were asked to apply 2 milligrams (mg) of sunscreen per square centimeter over 75% of their body, using either one of two sprays, a lotion or a cream. This amount equates to the maximum recommended dose recommended by most makers of sunscreen.
A total of 30 blood samples were collected from each participant over seven days of application. The geometric mean maximum plasma concentrations were as follows for each of the chemicals:
- Oxybenzone — 209.6 nanograms per milliliter (ng/mL) for spray No. 1; 194.9 ng/mL for spray No. 2, and 169.3 ng/mL for lotion
- Avobenzone — 4 ng/mL for spray No.1; 3.4 ng/mL for spray No. 2; 4.3 ng/mL for lotion and 1.8 ng/mL for the cream
- Octocrylene, — 2.9 ng/mL for spray No. 1; 7.8 ng/mL for spray No. 2; 5.7 ng/mL for lotion, and 5.7 ng/mL for cream
- Ecamsule — 1.5 ng/mL for cream
As noted by the authors, systemic concentrations for all four products were greater than 0.5 ng/mL after four applications on the first day. Below this threshold of 0.5 ng/mL, the FDA will typically waive nonclinical toxicology studies for sunscreens. Since all four chemicals exceeded the safety threshold, the agency determined that additional toxicology assessment would be required.
Now, it bears mentioning that the safety threshold of 0.5 ng/mL is based on the FDA’s regulation of food packaging substances, not chemicals that are absorbed through your skin.
Chemicals that migrate from packaging into food are ingested, whereas sunscreen chemicals are absorbed through your skin directly into your bloodstream, bypassing your digestive tract, which has the ability to filter out some of the toxins. In short, there’s no telling whether the 0.5 ng/mL threshold is actually safe and appropriate for these (and other) sunscreen chemicals.
Follow-Up Research Confirms Previous Finding
January 21, 2020, the FDA research team published a follow-up study on 48 adults using an expanded lineup of active sunscreen ingredients. This time, they looked at avobenzone, oxybenzone, octocrylene, homosalate, octisalate and octinoxate in lotion; aerosol spray; nonaerosol spray; and pump spray form.
Participants applied 2 mg of sunscreen per square centimeter over 75% of their body at two-hour intervals at baseline and on days 2, 3 and 4. Blood samples were collected over 21 days. Geometric mean maximum plasma concentrations for the various ingredients and products were as follows (listed from highest to lowest concentrations):
Oxybenzone: Lotion – 258.1 ng/mL Aerosol Spray – 180.1ng/mL
Homosalate: Aerosol Spray – 23.1ng/mL Non Aerosol Spray – 17.9ng/mL Pump spray – 13.9ng/mL
Octinoxate: Non Aerosol Spray – 7.9ng/mL Pump Spray – 5.2ng/mL
Octocrylene: Lotion – 7.8ng/mL Aerosol Spray – 6.6ng/mL Non Aerosol Spray – 6.6ng/mL
Avobenzone: Lotion – 7.1ng/mL Aerosol Spray – 3.5ng/mL Non Aerosol Spray – 3.5ng/mL Pump Spray – 3.3ng/mL
Octisalate: Aerosol Spray – 5.1 ng/mL Non Aerosol Spray – 5.8ng/mL Pump Spray – 4.6ng/mL
As in the first study, oxybenzone concentrations were about 400 to 500 times higher than the presumed safety threshold after just a couple of days’ use. Despite that, the FDA continues to urge Americans to use sunscreen.
The justification for this recommendation, as noted by Drs. Adewole S. Adamson and Kanade Shinkai in an accompanying editorial, is the “absence of clear data demonstrating harm.” Alas, oxybenzone in particular has been linked to a variety of potential health problems, including allergies, hormone disruption and cell damage.
Oxybenzone Is Far From Harmless
Importantly, research shows oxybenzone and several other active ingredients in sunscreens enhance the ability of other chemicals to penetrate your skin, including toxic herbicides, pesticides and insect repellants.
According to a study published in 2004, oxybenzone, octyl methoxycinnamate, homosalate, octyl salicylate, padimate-o and sulisobenzone all significantly increased absorption of the herbicide 2,4-D, which can be a significant concern for agricultural workers in particular.
Oxybenzone (as well as at least eight other sunscreen ingredients) also acts as an endocrine disrupter, and research published in 2018 warned it can induce changes in the breasts when used during pregnancy and lactation. According to the authors:
“These data suggest that oxybenzone, at doses relevant to human exposures, produces long-lasting alterations to mammary gland morphology and function. Further studies are needed to determine if exposure to this chemical during pregnancy and lactation will interfere with the known protection that pregnancy provides against breast cancer.”
Other studies have shown oxybenzone:
- Is a phototoxicant, which means its adverse effects, and its ability to form harmful free radicals, are magnified when exposed to light
- Which, of course, is the primary use of the product
- Is Neurotoxic (Toxic to your brain)
- Can “significantly lower” testosterone in adolescent boys
- Reduces sperm count in men
- Alters hormone levels in men, specifically testosterone, estradiol and inhibin B
- Is linked to endometrosis in women
- Increases male infertilty by affecting calcium signaling in sperm, in part by exerting a progesterone-like effect.
- Can result in lower male birth weight and decreased gestational age
- Is lethal to certain sea creatures and offspring, and poses a serious threat to coral reefs and sea life
Considering the endocrine disrupting and neurotoxic effects of oxybenzone, its high absorbability, and the availability of safe sunscreens (those containing non-nanosized zinc oxide and titanium dioxide), it seems rather irrational to continue using oxybenzone-containing sunscreen to protect yourself against skin cancer.
Research by the U.S. Centers for Disease Control and Prevention published in 2008 found 96.8% of the 2,517 urine samples collected as part of the 2003-2004 National Health and Nutrition Examination Survey had detectable levels of oxybenzone, which is a testament to just how much sunscreen people are using. And this data is 15 years old. It is likely far worse now.
Safer Sunscreens Are Available
When selecting a sunscreen, it’s important to realize there are only two known safe sunscreen ingredients — zinc oxide and titanium dioxide — and they must not be nanosized, as nanoscale zinc oxide37 and titanium dioxide have their own health risks.
Your safest choice is a lotion or cream with non-nanoscale zinc oxide, as it is stable in sunlight and provides the best protection from UVA rays. Your next best option is non-nanoscale titanium dioxide.
Also keep in mind that the sun protection factor (SPF) only tells you the level of protection you get from UVB rays (the rays within the ultraviolet spectrum that allow your skin to produce vitamin D), not UVA (which penetrate deeper and are responsible for much of the skin damage associated with excessive sun exposure.
So, make sure the product you select is labeled “broad spectrum SPF,” which indicates the product protects against both UVA and UVB. As a general rule, avoid sunscreens with an SPF above 50. While not intrinsically harmful, the higher SPF tends to provide a false sense of security, encouraging you to stay in the sun longer than you should.
Moreover, higher SPF typically does not provide much greater protection. In fact, research suggests people using high-SPF sunscreens get the same or similar exposure to UV rays as those using lower-SPF products. What’s more, an analysis by Consumer Reports found many sunscreens are far less effective than claimed on the label; 32 of the 82 products evaluated for 2019 offered less than half the protection promised by their stated SPF. Consumer Reports said they’d seen “a similar pattern in previous years’ sunscreen tests.