Is Sunscreen Hazardous To Your Health?

Introduction

How do sunscreens work?

Sunscreens work to protect your skin from ultraviolet (UV) radiation, by blocking its absorption by your skin. To understand this better,we must first understand what ultraviolet radiation is, and what harm does it pose to you and your health?¹

UV radiation is light, which has a wavelength shorter than visible light (the light that is detected by the retina in your eyes).¹

So, how do sunscreens help? Sunscreens contain chemical and physical compounds which aid in filtering out the following types of ultraviolet radiation: UVA1, UVA2 and UVB radiation. UVA1 and UVA2 radiation can penetrate your skin more deeply than UVB radiation, and UVA radiation is responsible for the following effects:

• Skin damage, such as sunburn
• Photoaging
• Carcinogenesis

UVB radiation causes your skin to have a tan or burn, and is less associated with photoaging and carcinogenesis.¹

Types of sunscreens

Chemical sunscreens

What are the common active ingredients in chemical sunscreens?

• Oxybenzone
• Avobenzone
• Octocrylene
• Octinoxate^1,2

How do chemical sunscreens work?

Chemical sunscreens work by using chemical filters, such as those listed above (oxybenzone and avobenzone for example). These chemical filters absorb high intensity ultraviolet radiation and convert this radiation into heat (infrared radiation), which is then released from your body. Infrared radiation has a low energy wavelength and poses less harm to you than ultraviolet radiation.¹

Physical (mineral) sunscreens

What are the common ingredients in physical sunscreens?

The active ingredients in physical (mineral) sunscreens are:

• Titanium oxide
• Zinc oxide¹

How do physical sunscreens work?

Unlike chemical sunscreens, physical sunscreens do not typically absorb ultraviolet radiation, but act as a physical barrier, reflecting or refracting ultraviolet radiation away from your skin. However, there have been studies demonstrating that when the particles used in the sunscreen are very small, the mechanism of action is similar to that of chemical sunscreens, where ultraviolet radiation is absorbed and converted into heat energy. ¹

Potential health risks of chemical sunscreens

Hormonal, reproductive and neural disruption

Oxybenzone

Oxybenzone (Benzophenone-3), and Benzophenone-1, which is produced from the breakdown of oxybenzone, have been widely used as chemical sunscreen filters, to protect your skin from ultraviolet radiation. However, oxybenzone has been shown to have a number of differing effects on your hormone (endocrine) system, your reproductive system and central nervous system, which are listed below:

• Anti-androgenic activity: several studies have found oxybenzone to elicit anti-androgenic activity, meaning that this compound blocks the effects of androgens- male sex hormones, such as testosterone from eliciting effects on the human body
• Affects sperm cell motility, which in turn can impair a male’s fertility
• Thyroid hormone disruption: studies have found that oxybenzone can prevent the synthesis (production) of thyroid hormone, which may result in hypothyroidism. In addition, studies have found that oxybenzone can alter the expression of genes which are responsible for thyroid hormone production, which can result in either too much or too little thyroid hormone being produced
• Affects sperm development and follicular development: the effects of oxybenzone sunscreens has been studied in rats, demonstrating that this can affect sperm development and delay follicular development in females- how quickly the females eggs develop in the follicular phase before they are ready for fertilisation
• Delay in embryo development: in mice it has been demonstrated that oxybenzone can inhibit the development of an embryo up to the blastocyst stage (in humans this is the 5^th to 6^th day after conception where the embryo is a ball of rapidly dividing cells)
• Crossing the placental barrier: oxybenzone can cross the placenta if you are pregnant, resulting in babies assigned male at birth having an increased birth weight, and babies assigned female at birth having a decreased birth weight
• Neurotoxicity: oxybenzone has been demonstrated to be neurotoxic if it is absorbed into your bloodstream and crosses your blood brain barrier, where it has toxic effects on neuronal cells^3,4,5

Avobenzone and Octinoxate

Sadly, evidence of hormone disruption is not limited to the chemical filter that is oxybenzone. Other chemical filters- avobenzone and octinoxate- have been reported to cause a decrease in the production of thyroid hormone (known as thyroxine) in zebrafish larvae.

This decrease in thyroxine production has been shown to be detrimental to the zebrafish larvae’s survival, and impacts their development. However, further research is needed to investigate how these chemical filters impact your health, human health in terms of endocrine (hormone) disruption.^2,3

Octocrylene

Many studies have investigated how much endocrine disruption chemical filters cause. However, in comparison to chemical filters such as oxybenzone, octocrylene has been demonstrated to be safe and effective in protecting your skin from ultraviolet radiation, according to certain studies.⁵

Skin reactions

Allergic reactions

Oxybenzone has been demonstrated to cause allergic contact dermatitis, which causes an itchy rash to develop on the skin in response to oxybenzone. Oxybenzone has been reported as one of the top 3 allergens that is found in your sunscreens, with 70% of allergic reactions to sunscreen being attributed to oxybenzone.³ Other chemical filters also have reported cases of allergic contact dermatitis after use, including the following:

• Avobenzone
• Octocrylene
• Octinoxate⁶

In comparison to chemical filters, physical filters, such as zinc oxide and titanium oxide have demonstrated no reports of causing allergic contact dermatitis, highlighting that physical sunscreens may be the best alternative for those who have an allergy to the active compounds in chemical sunscreens.⁶

Potential health risks of physical sunscreens

In comparison to chemical sunscreens, physical screens do not cause skin sensitization, and do not penetrate your skin as much. However, with zinc oxide and titanium oxide filters, they have poor particle dispersion due to the zinc oxide and titanium particles being too large in size.

This means that they are difficult to apply to your skin as sunscreen. However, this is where nanotechnology comes into the scene. Nanoparticles are particles with a size of less than 100 nm, which is smaller than the original size of these particles.

Nanoparticles of titanium oxide and zinc oxide are smaller, and therefore easier to apply in a transparent layer onto your skin, rather than leaving a visible layer of sunscreen. However, there are some changes to the properties of these particles when they become smaller in size, which can have undesirable effects. These effects will be discussed below.⁷

Inhalation of nanoparticles

Mineral sunscreen sprays pose a risk of releasing titanium oxide and zinc oxide nanoparticles into the air.⁸

Zinc Oxide

If zinc oxide nanoparticles are inhaled, studies have shown that this can increase the number of inflammatory cells that are present in your lungs. In addition, studies have observed that inhalation of these nanoparticles can cause the breakdown of DNA strands in your lung cells. The effects of this are still being investigated in ongoing studies.⁸

Titanium Oxide

Similar to when zinc oxide nanoparticles are inhaled, titanium oxide nanoparticles can cause an inflammatory response in the lungs when inhaled. Additionally, titanium oxide nanoparticles also cause changes in how the smooth muscle functions in your lungs. Scientific research has suggested that over time this may result in air movement in and out of the lungs becoming impeded. Consequently, this may result in chronic pulmonary obstructive disease or pulmonary fibrosis. However, more research is needed to confirm this hypothesis.⁸

Skin absorption

Zinc oxide and titanium oxide

Both mineral sunscreens containing zinc oxide and titanium oxide nanoparticles have been demonstrated to show both photo cytotoxicity and genotoxicity in your skin layers. Photo Cytotoxicity affects your body on a cellular level, causing the plasma membrane of your cells (which contains the contents of your cells) to be disrupted, releasing the intracellular contents to the external environment, which can result in cell death. Genotoxicity can cause damage to the DNA and genetic information within your cells, which can cause mutations, and potentially result in cancer.⁹

Regulatory perspectives

FDA guidelines and regulations

The FDA has not banned any sunscreen active ingredients. However, they have raised concerns, and require evidence about the safety of the following active ingredients found in sunscreen:

• Oxybenzone
• Avobenzone
• Octocrylene
• Dioxybenzone
• Cinoxate
• Octinoxate
• Ensulizole
• Homoslate
• Meradimate
• Padimate O
• Sulisobenzone
• Octisalate¹⁰

Balancing benefits and risks

Benefits of sun protection

Despite the negatives, sunscreen does have benefits to you and your health, including the following:

• Protecting you against UVA rays, which are responsible for skin cancer, and photoaging of your skin
• Protecting you against UVB rays, which can cause damage to your skin via sun burn¹

Recommendations for safer use

Choosing appropriate sunscreens

For day to day use you should use a sunscreen that has an SPF of at least 30 to protect you. You should also use a sunscreen that has at least a 4-star UVA protection too.

Complementary sun protection methods

The following can help provide protection from the sun:

• Sunglasses to protect the eyes
• A hat with a wide brim to protect your face and neck
• Long sleeve top, trousers and long skirts that do not allow sunlight to penetrate

Summary

• Sunscreen has many benefits, protecting you from UVB and UVA radiation
• Sunscreen can prevent cancer, photoaging and sunburn
• Sunscreens are either chemical or physical (mineral)
• Evidence suggests that certain active compounds in chemical sunscreens can result in hormone disruption, and can cause reproductive issues
• Evidence suggest that zinc oxide and titanium oxide in physical sunscreens can cause inflammation of the lung, if they are inhaled as nanoparticles, and they may cause DNA damage