Sunscreen is considered essential for skin health. It is scientifically proven to reduce the risk of some skin cancers and prevent premature aging. However, many people still ask the question: “Is sunscreen bad for you?”

Over the past few years, a number of media sources have reported some alleged risks of sunscreen use. These reports often come with shock-factor headlines, which are designed to make you want to read more.

However, considering that the majority of people only read headlines before sharing news articles on social media, these shock-factor headlines can lead us to believe that sunscreen does more harm than good.

So, what’s the truth? Is sunscreen bad for you?

To answer this question, it’s important to understand why we use sunscreen in the first place.

Ultraviolet Radiation (UV)

There are three types of UV rays; UVA, UVB, & UVC. UVA has the longest wavelength and UVC has the shortest.

Due to the short wavelength of UVC rays, they are absorbed by the atmosphere before they can reach the surface of the earth or your exposed skin ^[1][2][3].

UVB = UVBurning: These are the rays that cause sunburn. UVB rays penetrate the surface layer of the skin (the epidermis) and can cause damage to the cells there. This causes an inflammatory response that results in pain and redness ^[1][2].

In sunscreen, UVB protection is measured by Sun Protection Factor (SPF).

UVA = UVAging: These are the rays that are responsible for premature skin aging. UVA rays have the longest wavelength out of the three UV rays and can penetrate the deeper layer of the skin (the dermis).

The damage done here is not noticeable in the short-term (i.e. no sunburn). However, damage appears later on down the line as premature aging, pigmentation, and in some cases skin cancer ^[1][2].

At the moment, there isn’t a standardized measurement of UVA protection in sunscreens.

UV radiation, from both UVA and UVB rays, is one of the main risk factors for skin cancer ^[1][2][3]. UVA rays make up the majority of UV radiation and exposure to UVA is usually constant year-round. UVB exposure, however, occurs more during the summer months ^[4].

The Role Of Sunscreen

Sunscreens protect the skin by blocking, reflecting, or scattering UV rays. This reduces UV damage and makes skin more tolerable of UV radiation ^[5].

The active ingredients in sunscreen can be organic (chemical) or inorganic (physical/mineral).

Chemical sunscreens are designed to absorb high-energy UV rays, whereas physical sunscreens reflect and scatter UV light ^[6]. Although physical sunscreens do also absorb some UV rays.

Common active sunscreen filters include:

Chemical:

• Avobenzone
• Oxybenzone
• Octinoxate
• Octocrylene
• Homosalate
• Enzacamene

Physical:

• Zinc oxide
• Titanium dioxide

Chemical sunscreen agents absorb either UVA, UVB, or both UVA and UVB. Usually, this means that multiple active agents are used in chemical sunscreens to ensure protection from the whole UV spectrum ^[6].

Several common chemical sunscreen agents are also used in cosmetics and fragrances. This is particularly the case for oxybenzone. In fact, it is estimated that approximately 96.8% of people in the US are exposed to oxybenzone ^[7][8].

For this reason, oxybenzone is one of the most discussed sunscreen agents in medical literature.

So, Is Sunscreen Bad For You?

Various media sources report that sunscreen may have some undesirable effects. Allegations include that sunscreen speeds-up cancer development, messes with hormones, and causes vitamin D deficiency.

So is sunscreen bad for you? Let’s have a look at what the research says.

Sunscreen Speeds-up Cancer Development

So, it appears that this allegation isn’t based on sunscreen itself, but on an ingredient that is often added into sunscreens; retinyl palmitate (a derivative of vitamin A/retinol).

Retinyl palmitate has been investigated as a ‘photocarcinogen’, which basically means that it may speed up the development of skin tumours on sun-exposed skin ^[9].

This was demonstrated in a study that treated mice with small doses of retinyl palmitate in combination with ultraviolet light. The mice that were treated with retinyl palmitate developed skin tumours faster than untreated mice. Treated mice also ended up with a higher number of tumours than the untreated mice ^[9]. This finding was confirmed again a year later ^[10].

Light Reactivity of Vitamin A Products

Vitamin A products have long been known to make the skin more sensitive to sunlight. This is why people using vitamin A products (e.g. for reducing acne and wrinkles) are advised to apply them at night. It is also recommended to avoid sun exposure or to use a good broad-spectrum sunscreen during the day ^[11].

When vitamin A products react with UV light, they form harmful free radicals. These free radicals break down to form chemicals that are toxic to the skin ^[12]. This can lead to DNA damage and the appearance of skin lesions and/or tumours ^[9][13].

One study compared creams with 0.1%, 0.5%, 1%, or 2% retinyl palmitate or retinoic acid (levels typically found in cosmetics) to creams without retinol. All the retinol creams, as well as the non-retinol cream, contained a solvent called diisopropyl adipate.

The different creams were applied to genetically engineered mice (mice that were bred to be genetically similar to humans). Following this, the mice were exposed to various intensities of UV light.

While all mice experienced some level of skin damage, the level of damage was higher among the mice treated with retinol creams. The level of sun damage increased further when the concentration of vitamin A (%) in the cream was higher.

Interestingly, the study ended up identifying another potential skin-damage-causing ingredient: diisopropyl adipate. This was apparent due to the fact that the mice who had the control cream applied still suffered skin damage.

However, as there was no non-cream control group, it is hard to tell whether the damage may have been due to the cream rather than the UV exposure itself. Nevertheless, it’s worth being aware of this risk as many sunscreens contain both retinyl palmitate and diisopropyl adipate ^[14].

Human Use Of Retinyl Palmitate

So, that’s the research behind the claim that sunscreen can speed-up the development of skin cancer. However, these studies are based on how vitamin A products and UV radiation affects the skin of mice. So far, there aren’t any studies that have found similar results with humans.

In fact, oral vitamin A can actually reduce the rates of skin cancer in people who have a high risk of developing the disease ^[15]. For example, vitamin A is used to prevent skin cancer in transplant patients ^[16].

Furthermore, topical and oral retinoids have been regularly prescribed by dermatologists for conditions such as acne, psoriasis, and photoaging, for more than 40 years.

These patients are routinely monitored by dermatologists to ensure their skin condition is improving. Considering this, there are no documented records or published research to suggest that these retinoids increase the risk of skin cancers ^[17].

Sunscreen And Melanoma

Some evidence has suggested that sunscreen use may increase the risk of melanoma (a life-threatening skin cancer). Although, this appears to be due to inadequate protection and improper use of sunscreens, rather than due to sunscreen itself.

Sunscreens absorb the majority of UVB radiation, however, the amount of UVA radiation they can absorb is more variable. As UVB radiation causes sunburn, people often think they are adequately protected when their skin is not burning.

However, this provides a false sense of security and can lead to longer, intentional, exposure ^[18][19][20]. This is particularly the case with sunscreens that have a high SPF, as people overestimate how protected they are.

Furthermore, at the time these studies were conducted, people used lower SPF than is currently recommended and sunscreens had little to no UVA protection.

When sunscreen is used correctly, it can reduce the incidence of melanoma by 50-73% ^[21].

Sunscreen Messes With Your Hormones

Some research has suggested that a number of chemical UV filters may mimic human hormones. Two of the biggest alleged offenders are octinoxate and oxybenzone.

Octinoxate

Octinoxate is a UVB filter approved for use in cosmetics at concentrations of 7.5-10% ^[22]. In 2003 it was estimated that 80% of sunscreens contained octinoxate ^[23]. It is absorbed through the skin and has been detected in blood and urine at negligible amounts (0.002% of the applied dose) ^[24].

Studies using rats and mice have demonstrated that octinoxate interferes with the endocrine system ^[25], and can increase oestrogen levels ^[26]. It does appear, then, that octinoxate can interfere with hormones in rats and mice, but what about in humans?

Well, one study found small effects of octinoxate on testosterone and oestrogen levels in men, however, the authors report that the differences in hormone levels were not related to sunscreen exposure ^[24].

Oxybenzone

Oxybenzone is a broad spectrum UV filter which means that it absorbs both UVA and UVB rays. It is present in 60% of sunscreens ^[23] at a maximum concentration of 6% ^[22]. As mentioned before, 96.8% of people in the US are exposed to oxybenzone as it is used in a wide variety of cosmetics. As well as being detected in blood and urine, oxybenzone has also been found in human breast milk ^[27].

In fact, one study identified a correlation between the level of oxybenzone present in the urine of pregnant women and the weight and head circumference of the baby ^[28]. Basically, the higher the level of oxybenzone in the urine samples, the larger the weight and head circumference of the baby. This could suggest a risk of prenatal exposure that may lead to foetal developmental issues.

Oral Oxybenzone

When consumed orally, oxybenzone mimics oestrogen and can cause a 23% increase in uterine weight in rats. However, the dose that was used to cause a significant increase in uterine weight was incredibly high. Additionally, even at this incredibly high dose, no toxic effects were identified ^[29].

While studies in mice and rats provide useful insights into potential toxic effects of drugs, it is hard to say how reflective rodent models are of humans. Furthermore, I don’t know about you, but I don’t tend to eat my sunscreen. So is this evidence really relevant to humans or day to day life?

Although some studies have looked at the effects of oxybenzone in humans, there is not a huge amount of research in this area.

Topical Oxybenzone

One study had men and women applying a topical cream containing a 10% concentration of oxybenzone at a dose of 2mg/cm² (the recommended dose of sunscreen to achieve the stated SPF protection) daily.

Lower levels of testosterone and estradiol were observed in men within four hours of applying the cream and lower levels of testosterone were observed in women within 24 hours of application.

However, after four days of daily application of the cream there appeared to be no differences in hormone levels between the individuals that applied the oxybenzone cream and those that applied a control cream. This led the authors to conclude that the observed hormone differences were not due to oxybenzone ^[24].

Hormone-Disrupting Chemicals and Breast Cancer

Some organisations have reported that hormone-disrupting sunscreen ingredients can increase the risk of breast cancer by blocking or mimicking oestrogen. Particularly as oestrogen exposure is known to be a risk factor for breast cancer ^[30].

The fact that both octinoxate and oxybenzone, as well as enzacamene and homosalate, have been found in human breast milk led researchers to believe that they may also be present in human breast tissue ^[31][32].

Breast tissue was obtained from women who had undergone a mastectomy (surgical removal of one or both breasts) and was analysed for the presence of these 4 UV filters. One or more of the UV filters was present in 84% of tissue samples.

Oxybenzone was present in 69%, octinoxate in 74%, and enzacamene in 13% of the breast tissue samples. Furthermore, oxybenzone levels were significantly higher at breast tumour sites.

It is important to note that there is no way of identifying the source of the chemicals, or knowing whether they were absorbed through the skin. There is also no comparison to healthy breast tissue. Considering that approximately 96.8% of people in the US are exposed to oxybenzone ^[7][8], it is highly likely that healthy breast tissue also contains varying levels of these chemicals.

Overall, this research has led to chemical sunscreens receiving a bad reputation, with people increasingly turning toward physical sunscreens as their sun protection of choice.

However, physical sunscreens are not immune to negative media coverage.

Mineral Nanoparticles

Mineral sunscreens have several advantages over chemical sunscreens. For example, they are more stable upon UV exposure and less likely to cause an allergic reaction. Originally, both titanium dioxide and zinc oxide sunscreens were formulated with large particles.

However, the larger particles caused a heavy ‘white cast’ on the skin which led to many people avoiding mineral sunscreens. This encouraged manufacturers to produce smaller mineral particles or ‘nanoparticles’ ^[33].

Nanoparticles are most often defined as particles with a diameter less than 100 nanometers (nm). Mineral nanoparticles have raised concern due to changes in the way they react to light when they have diameters of 30nm or less ^[34].

It was also thought that smaller particles would penetrate the skin with more ease. However, this appears not to be the case.

Are Nanoparticles Absorbed By The Skin?

Multiple studies, using both animal and human skin have shown that zinc oxide and titanium dioxide nanoparticles only penetrate the outer most layers of the skin. In other words, the nanoparticles are unable to enter the bloodstream through the skin ^[35][36].

Furthermore, nanoparticles tend to cluster together in sunscreens and these clusters likely exceed 100nm. So they aren’t really ‘nanoparticles’ by definition when they are used as ingredients in sunscreen ^[33].

However, there is evidence that mineral nanoparticles may produce free radicals that cause damage to DNA when exposed to UV radiation ^[37]. This has been observed for both titanium dioxide ^[38] and zinc oxide ^[39].

In these studies, however, nanoparticles and UV radiation were applied to tissue and cell samples rather than intact skin. Therefore, as nanoparticles are unable to penetrate the skin, these findings may not be applicable to sunscreens or cosmetics that nanoparticles.

Furthermore, it is common practice for sunscreen manufacturers to use a surface coating on mineral particles. This stabilises the particles and reduces their UV reactivity by up to 99% ^[40].

Additionally, UV reactivity might not be a concern for human skin as it has a certain amount of natural antioxidant protection ^[40].

Titanium Dioxide Inhalation

Titanium dioxide received a particularly bad rep when the National Institute for Occupational Safety and Health (NIOSH) categorised sub-micron-sized titanium dioxide as a ‘potential occupational carcinogen’. The International Agency for Research on Cancer (IARC) took a similar stance and classified titanium dioxide as ‘possibly carcinogenic to humans’.

This was due to several reports of health issues in factory workers who were exposed to titanium dioxide through their job. In addition to this, titanium dioxide particles have been found in the lungs of workers who are exposed to the mineral ^[41].

While it has been demonstrated that titanium dioxide nanoparticles can cause lung cancer in rats ^[42], an increase in lung cancer has not been observed in humans who are regularly exposed to the mineral ^[43][44].

One study looked at pre-existing data from 6 European countries that included titanium dioxide workers. When compared to the general population, there did seem to be a small, but significant, increase in lung cancer among the men who worked with titanium dioxide. 

However, the data did not suggest that this increase was due to titanium dioxide exposure as the rates of lung cancer did not increase with duration of employment or duration of exposure to the mineral ^[45].

Nevertheless, as mineral sunscreens are often available in a spray form, it is important to be aware of the potential risks of inhaling mineral nanoparticles. This is also the case for powdered cosmetics that contain titanium dioxide.

Sunscreen Use Causes Vitamin D Deficiency

Vitamin D is one of the essential vitamins for the development and maintenance of healthy bones and muscles. It is mainly acquired when the skin is exposed to UVB radiation ^[46][47][48]. As sunscreen is designed to block or absorb UVB (as well as UVA), concerns have arisen as to whether regular sunscreen use can cause a vitamin D deficiency.

Multiple studies have demonstrated that sunscreen use reduces the skins ability to absorb vitamin D ^[49][50][51]. In fact, sunscreen use is associated with reductions in vitamin D levels by more than 50% ^[50]. However, this may be due to sun exposure behaviours rather than sunscreen itself.

One study found that an SPF 15 sunscreen completely blocked the production of vitamin D from UVB exposure when applied to the whole body ^[51]. However, other studies have found no difference in vitamin D levels between sunscreen users and non-sunscreen users when observed in a real-life setting ^[52]. Furthermore, some studies have even reported an increased level of vitamin D in sunscreen users ^[53].

However, again, this is likely due to behavioural differences.

For example, sunscreen users may expose themselves to UV radiation more often and/or for longer. In other words, if someone is planning on spending the day sunbathing, they are likely to use sunscreen.

While it should seem obvious that sunscreen would reduce vitamin D levels, this does not appear to be the case. The fact that people rarely apply the recommended amount of sunscreen and/or reapply sunscreen frequently enough, likely explains this discrepancy.

Furthermore, even if there was enough evidence to suggest that sunscreen use causes vitamin D deficiency, vitamin D can be obtained through diet or supplements.

So, Is Sunscreen Bad For You?

The short answer is no, sunscreen is not bad for you. In fact, it is pretty much essential for skin health.

The longer answer, however, is that sunscreen itself is not bad for you, but some ingredients that are commonly used in sunscreens may be. There isn’t enough research to support the claims that sunscreen speeds up cancer, or that sunscreen interferes with hormones, or even that sunscreen can cause vitamin D deficiency.

The majority of the research that is behind these claims relies on how sunscreen ingredients affect rodents. There is hardly any evidence to suggest that these findings translate to humans.

Oxybenzone, Octinoxate, and Enzacamene have been found in both breast milk and breast tissue. There is no evidence that the presence of these chemicals in breast tissue or breast milk causes harm. However, further research is needed before we can be sure of this.

Therefore, while it would be unreasonable to avoid sunscreen altogether, it is entirely reasonable (although perhaps unnecessary) to avoid the concerning ingredients.

You can still use sunscreen on a daily basis without the potential risks mentioned in this article by:

• Avoiding sunscreens and cosmetics that contain Oxybenzone and Octinoxate.
• Opting for sunscreens that are free from Retinyl Palmitate.
• Staying clear of spray sunscreens that contain titanium dioxide.
• Sticking to zinc oxide based sunscreens, which are considered the safest and least irritating.
• Making sure you are getting enough vitamin D in your diet.

It is important that you still wear sunscreen daily. As many dermatologists and aestheticians will tell you…

In addition to oxybenzone and octinoxate having potentially harmful-to-health side-effects, they may also be bad for the environment. In fact, as of January 2021, Hawaii are banning the sale and distribution of sunscreens containing oxybenzone and/or octinoxate. This is in order to prevent coral reef bleaching and protect marine ecosystems.

Whether you are concerned about the health risks or the environmental impact of these chemicals, there are plenty of oxybenzone and octinoxate free sunscreens available to choose from.

References

1. Laurent-Applegate, L. & Schwarzkopf, S. (2001). ‘Photooxidative stress in skin and regulation of gene expression’. In Environmental Stressors in Health and
   Disease, Fuchs & L. Packer Eds. Marcel Dekker: New York, NY, USA.
2. Halliwell, B. & Gutteridge, J. (2007). Free Radicals in Biology and Medicine. Oxford University Press: New York, NY, USA, 4^th
3. Battie, C., Jitsukawa, S., Bernerd, F., Del Bino, S., Marionnet, C. & Verschoore, M. (2014). ‘New insights in photoaging, UVA induced damage and skin types’. Experimental Dermatology, 23(1), https://doi.org/10.1111/exd.12388
4. DeBuys, H., Levy, S., Murray, J., Madey, D. & Pinnell, S. (2000). ‘Modern approaches to photoprotection’. Dermatol Clin, 18, 577-590.
5. Yuan, C., Wang, X., Tan, Y., Yang, L., Lin, Y. & Wu, P. (2010). ‘Effects of sunscreen on human skin’s ultraviolet radiation tolerance’. Journal of Cosmetic Dermatology, 9(4), 297-301.
6. Lademann, J., Scanzer, S., Jacobi, U., Schaefer, H., Pflucker, F., Driller, H., Beck, J., Meinke, M., Roggan, A. & Sterry, W. (2005). ‘Synergy effects between organic and inorganic UV filters in sunscreens’. Journal of Biomedical Opt., 10(1), 14008.
7. Calafat, A., Wong, L., Ye, X., Reidy, J. & Needham, L. (2008). ‘Concentrations of the sunscreen agent benzophenone-3 in residents of the United States: National Health and Nutrition Examination Survey 2003-2004. Environmental Health Perspective, 116(7), 893-897.
8. Wang, S., Burnett, M. & Lim, H. (2011). ‘Safety of oxybenzone: putting numbers into perspective’. Arch Dermatol., 147(7), 865-866.
9. NTP (National Toxicology Program). (2010). ‘Draft Technical Report on the Photococarcinogenesis Study of Retinoic Acid and Retinyl Palmitate [CAS Nos. 302-79-4 (All-Trans-Retinoic Acid) and 79-81-2 (All-Trans-Retinyl Palmitate)] in SKH-1 Mice (Simulated Solar Light And Topical Application Study)’. Scheduled Peer Review Date: January 26, 2011. NTP TR 568. NIH Publication No. 11-5910. Available: http://ntp.niehs.nih.gov/index.cfm?objectid=A73F2BD6-F1F6-975E-789930D86…
10. National Toxicology Program (NTP). (2011). ‘Findings of NTP Board of Scientific Counselors on Retinoic Acid and Retinyl Palmitate – TR 568’. Meeting, January 26, 2011. Research Triangle, North Carolina. Available: http://ntp.niehs.nih.gov/INDEX6D67.HTM
11. Levin, J., Del Rosso, JQ. & Momin, S. (2010). ‘How Much Do We Really Know About Our Favorite Cosmeceutical Ingredients?’ J Clinical Aesthetic Derm 3(2), 22-41.
12. Tolleson, W., Cherng, S., Xia, Q., Boudreau, M., Yin, J., Wamer, W., et al. (2005). ‘Photodecomposition and phototoxicity of natural retinoids’. Int J Environ Res Public Health 2(1), 147-55.
13. Xia, Q., Yin, J., Wamer, W., Cherng, S., Boudreau, M., Howard, P., Yu, H. & Fu, P. (2006). ‘Photoirradiation of retinyl palmitate in ethanol with ultraviolet light–formation of photodecomposition products, reactive oxygen species, and lipid peroxides’. Int J Environ Res Public Health. 3(2), pp. 185-90.
14. Environmental Working Group (EWG). (2011). Products containing diisopropyl adipate. Available: https://www.ewg.org/skindeep/ingredient/products/701990/DIISOPROPYL_ADIPATE/
15. Moon, T., Levine, N., Cartmel, B., Bangert, J., Rodney, S., Dong, Q., Peng, Y. & Alberts, D. (1997). ‘Effect of retinol in preventing squamous cell skin cancer in moderate-risk subjects: a randomized, double-blind, controlled trial. Southwest Skin Cancer Prevention Study Group’. Cancer Epidemiol Biomarkers Prev, 6(11), 949-956.
16. McKenna, D. & Murphy, G. (1999). ‘Skin cancer chemoprophylaxis in renal transplant recipients: 5 years of experience using low-dose acitretin’. British Journal of Dermatology, 140, 656-660.
17. Wang, S., Dusza, S. & Lim, H. (2010). ‘Safety of retinyl palmitate in sunscreens: A critical analysis’. Journal of the American Academy of Dermatology, 63(5), 903-906.
18. Gorham, E., Mohr, S., Garland, C., Chaplin, G. & Garland, F. (2007). ‘Do sunscreens increase risk of melanoma in populations residing at higher latitudes?’. Ann Epidemiol, 17(12), 956-963. DOI: 10.1016/j.annepidem.2007.06.008.
19. Autier, P. (2009). ‘Sunscreen abuse for intentional sun exposure’. British Journal of Dermatology, 161, 40-45.
20. Autier, P., Boniol, M. & Dore, J. (2007). ‘Sunscreen use and increased duration of intentional sun exposure: Still a burning issue.’ International Journal of Cancer, 121, 1-5.
21. Green, A., Williams, G., Logan, V. & Strutton, G. (2011). ‘Reduced melanoma after regular sunscreen use: randomized trial follow-up’. Journal of Clinical Oncology, 29(3), 257-263.
22. Krause, M., Kilt, A., Blomberg Jensen, M., Soeborg, T., Frederiksen, H., Schlumpf, M., Lichtensteiger, W., Skakkebaek, N. & Drzewiecki, K. (2012). ‘Sunscreens: are they beneficial for health? An overview of endocrine disrupting properties of UV-filters’. Int J, Androl., 35, 424-436.
23. Nash, J., Tanner, P., Grosick, T. & Zimnawoda, M. (2004). ‘Sunscreen market analysis: the evolution and use of UVA-1 actives’. Journal of the American Academy of Dermatology, 50, 34.
24. Janjua, N., Mogensen, B., Andersson, A., Petersen, J., Henriksen, M., Skakkebaek, N. & Wulf, H. (2004). ‘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’. Invest. Dermatol., 123, pp. 57-61.
25. Klammer, H., Schlecht, C., Wuttke, W., Schmutzler, C., Gotthardt, I., Kohrle, J. & Jarry, H. (2007). ‘Effects of a 5-day treatment with the UV-filter octyl-methoxycinnamate (OMC) on the function of the hypothalamo-pituitary-thyroid function in rats’. Toxicology, 238, 192-199.
26. Klammer, H., Schlecht, C., Wuttke, W. & Jarry, H. (2005). ‘Multi-organic risk assessment of estrogenic properties of octyl-methoxycinnamate in vivo: A 5-day sub-acute pharmacodynamics study with ovariectomized rats’. Toxicology, 215, 90-96.
27. Schlumpf, M., Kypke, K., Wittassek, M., Angerer, J., Mascher, H., Mascher, D., Vokt, C., Birchler, M. & Lichtensteiger, W. (2010). ‘Exposure patterns of UV filters, fragrances, parabens, phthalates, organochlor pesticides, PBDEs, and PCBs in human milk: correlation of UV filters with use of cosmetics’. Chemosphere, 81, 1171-1183.
28. Philippat, C., Mortamis, M., Chevrier, C., Petit, C., Calafat, A., Silva, M., Brambilla, C., Pin, I., Charles, M., Cordier, S. & Slama, R. (2012). ‘Exposure to phthalates and phenols during pregnancy and offspring size at birth’. Health Perspect., 120, pp. 464-470.
29. Schlumpf, M., Cotton, B., Conscience, M., Haller, V., Steinmann, B. & Lichtensteiger, W. (2001). ‘In vitro and in vivo estrogenicity of UV screens’. Environmental Health Perspectives, 109(3), 239-244.
30. Miller, W. (1996). Estrogen and breast cancer. Chapman and Hall.
31. Alamer, M. & Darbre, P. (2018). ‘Effects of exposure to six chemical ultraviolet filters commonly used in personal care products on motility of MCF-7 and MDA-MB-231 human breast cancer cells in vitro’. Journal of Applied Toxicology, 38(2), 148-159. Available at: https://www.ncbi.nlm.nih.gov/pubmed/28990245
32. Barr, L., Alamer, M. & Darbre, P. (2018). ‘Measurement of concentrations of four chemical ultraviolet filters in human breast tissue at serial locations across the breast’. Journal of Applied Toxicology, 38(8), Available at: https://onlinelibrary.wiley.com/doi/full/10.1002/jat.3621
33. Burnett, M. & Wang, S. (2011). ‘Current sunscreen controversies: a critical review’. Photodermatology, Photoimmunology & Photomedicine, 27(2), Available at: https://doi.org/10.1111/j.1600-0781.2011.00557.x
34. Auffan, M., Rose, J., Bottero, J., Lowry, G., Jolivet, J. & Wiesner, M. (2009). ‘Towards a definition of inorganic nanoparticles from an environmental, health and safety perspective’. Natural Nanotechnology, 4, 634-641.
35. Landsdown, A. & Taylor, A. (1997). ‘Zinc and titanium oxides: promising UV-absorbers but what influence do they have on the intact skin?’, International Journal of Cosmetic Science, 19, 167-172.
36. Dussert, A., Gooris, E. & Hemmerle, J. (1997). ‘Characterisation of the mineral content of a physical sunscreen emulsion and its distribution onto human stratum corneum’. International Journal of Cosmetic Science, 19, 119-129.
37. Wamer, W., Yin, J. & Wei, R. (1997). ‘Oxidative damage to nucleic acids photosensitized by titanium dioxide. Free Rad Biol Med, 23, 851-858.
38. Nakagawa, Y., Wakuri, S., Sakamoto, K. & Tanaka, N. (1997). ‘The photogenotoxicity of titanium dioxide particles’. Mutat Res, 394, 125-132.
39. Hidaka, H., Kobayashi, H., Koike, T., Sato, T. & Serpone, N. (2006). ‘DNA Damage Photoinduced by Cosmetic Pigments and Sunscreen Agents under Solar Exposure and Artificial UV Illumination’. Journal of Oleo Science, 55(5), 249-261.
40. Environmental Working Group (EWG). (2018). Nanoparticles in Sunscreens. Available at: https://www.ewg.org/sunscreen/report/nanoparticles-in-sunscreen/#.W5bnwBNiegQ
41. National Institute for Occupational Safety and Health (NIOSH). (2011). Occupational Exposure to Titanium Dioxide. Department of Health and Human Services, Centers for Disease Control and Prevention.
42. Heinrich, U., Fuhst, R., Rittinghausen, S., Creutzenberg, O., Bellman, B., Koch, W. et al. (1995). ‘Chronic inhalation exposure of Wistar rats and 2 different strains of mice to diesel-engine exhaust, carbon-black, and titanium-dioxide’. Inhal Toxicol. 74, 533-556.
43. Fryzek, J., Chadda, B., Marano, D., White, K., Schweitzer, S., McLaughlin, J. et al. (2003). ‘A cohort mortality study among titanium dioxide manufacturing workers in the United States’. J Occup Environ Med. 45, pp 400-409.
44. Chen, J. & Fayerweather, W. (1988). ‘Epidemiologic-study of workers exposed to titanium-dioxide’. J Occup Environ Med. 30, 937-942.
45. Boffeta, P., Soutar, A., Cherrie, J., Granath, F., Andersen, A., Antilla, A., Blettner, M., Gaborieau, V., Klug, S., Langard, S. et al. (2004). ‘Mortality among workers employed in the titanium dioxide production industry in Europe’. Cancer Causes Control. 15(7), 697-706.
46. Wagner, C. & Greer, F. (2008). ‘Prevention of rickets and vitamin D deficiency in infants, children, and adolescents’. Pediatrics, 122, 1142-1152.
47. American Academy of Dermatology (AAD). (2009). Position Statement on Vitamin D. Available at: http://www.aad.org/forms/policies/uploads/ps/ps-vitamin%20d.pdf
48. Dawson-Hughes, B., Mithal, A., Bonjour, J., Boonen, S., Burckhardt, P., Fuleihan, G., Josse, R., Lips, P., Morales-Torres, J. & Yoshimura, N. (2010). ‘IOF position statement: Vitamin D recommendations for older adults’. Osteoporosis International, 21(7), 1151-1154.
49. Matsuoka, L. et al. (1987). ‘Sunscreens suppress cutaneous vitamin D3 synthesis’, J Clin Endocrinol Metab. 64, 1165-1168.
50. Matsuoka, L. et al. (1988). ‘Chronic sunscreen use decreases circulating concentrations of 25-hydroxyvitamin D. A preliminary study’. Arch Dermatol. 124, 1802-1804.
51. Matsuoka, L., Wortsman, J., Hollis, B. (1990). ‘Use of topical sunscreen for the evaluation of regional synthesis of vitamin D3’. J Am Acad Dermatol, 22(Part 1), 772-775.
52. Marks, R. et al. (1995). ‘The effect of regular sunscreen use on vitamin D levels in an Australian population. Results of a randomized trial’. Arch Dermatol, 131, 415-421.
53. Kligman, E. et al. (1989). ‘The impact of lifestyle factors on serum 25-hydroxy vitamin D levels in older adults: a preliminary study’, Fam Pract Res J, 9, 11-19.