For the average consumer, a sunscreen product is a cream or lotion used to reduce the skin’s exposure to the sun’s ultraviolet radiation. It is a means of passive external photo protection, working as an ultraviolet filter. There are many types of sunscreen products on the market, as well as day creams, foundations, lip sticks and hair products that contain UV filters.

For a specialist, a sun product is generally in the form of an emulsion that contains the following species

Overexposure to the sun

The use of sunscreens protects against UVB and also starts to filter UVA. But they have a perverse effect: people who use sunscreens believe they are protected from the sun and tend to expose themselves longer to the sun. The application of a product with a sufficient protection factor is recommended in case of unavoidable sun exposure. The application should be done before exposure and renewed regularly if exposure persists.

This type of product is to be used in addition to other existing methods. Such as: wearing clothes, sunglasses and a hat, not being exposed to the sun between 12 noon and 4 p.m. in France in the summer (because UVB radiation is at its highest intensity) and limiting the duration of exposure.

Chemical filters that are harmful to our hormones

Our skin is not an impenetrable barrier. Once the sunscreen is applied, the filters penetrate our body and end up in our blood. Some of them have even been detected in breast milk! These are the conclusions of a Swiss study conducted on 52 women from the maternity hospital in Basel. The participants were asked about their use of cosmetic products through a questionnaire. The milk samples were then analyzed for a wide range of chemicals, including UV filters. The researchers found traces of UV filters in 85% of the breast milk samples! They also found that there was a link between the application of sunscreens during pregnancy and the presence of two chemical compounds: 4-Methylbenzylidene camphor (4-MBC) and octocrylene (OC).

Once introduced into the body, these chemical filters can affect human health, but also animal health. One study looked at the potential endocrine disrupting effects of sunscreens. Among the 9 filters studied, 8 mimicked the effect of estrogen; 2 showed antiandrogenic properties, i.e. they are likely to be feminizing. Finally, 6 caused an increase in the weight of the uterus of female rats. The study also showed that exposure of animals to certain filters before and after birth affected hormonal development and modified the expression of genes regulated by female hormones. Congenital malformations, delayed puberty in males and changes in reproductive organs were observed. According to the study, exposure to these UV filters during pregnancy could pose the same risk to fetuses.

Mineral filters wih nanoparticles 

Given the danger of these chemical filters, it is often recommended to use sunscreens containing only mineral filters. These are generally titanium dioxides and zinc oxides. Mineral filters (in so-called “organic” creams) are hypoallergenic and photostable (which makes them the recommended sun product for allergic subjects and children). They are also effective as soon as they are applied. However, they are less appreciated by vacationers because they are more difficult to spread and give users an unattractive whitish tint. To improve the cosmetic aspect, laboratories have formulated products with filters in the form of nanoparticles. The small size of these materials allows sunscreens to have a better fluidity and a good hold.
But nanoparticles can also present health risks. In 2006, a study showed that their passage through the cells of the body and then to the bloodstream and internal organs is facilitated by their small size. Also, it has been suggested that titanium dioxide can induce DNA damage, thus promoting the development of cancer.

In addition, titanium oxide particles are less effective than zinc particles at UVA level. They react to light (photo degradation) by creating free radicals. But this phenomenon can be reduced by adding zinc oxide, which is why it is widely used.
Despite what the sellers may specify “without nano particles”, we will find zinc or titanium in this form, because zinc oxides are 30 to 200 nm, and 10 to 100nm for titanium.

Finally, the use of nanoparticles in spray or powder formulas exposes nanoparticles to inhalation, which can penetrate very deeply into the respiratory system and pass into the blood via the pulmonary alveoli. Apart from this particular situation, it has not yet been possible to reach a definitive conclusion on the danger of nanoparticles. The French National Agency for the Safety of Medicines (ANSM) nevertheless recommends not to use cosmetics – in particular sun creams – containing titanium dioxide nanoparticles on injured skin or on sunburns because of the potential risks for human health.

The effects of sunscreens do not only concern our body. For some years now, the chemical filters used in sun creams have been accused of causing significant water pollution. The filters can indeed be found in the water directly when swimming, or via the wastewater treatment plants when the filters are evacuated during showers, baths or laundry.

The effects of sunscreens on corals 

Among the effects of sunscreens on the environment, it has been shown a critical effect on corals. It was in 2008 that the first study. This study, conducted in several tropical regions, showed that extremely low concentrations of sunscreens caused viral infections on microalgae located in the corals and functioning in symbiosis with them. These infections were responsible for coral bleaching and death within 48 hours. In 2015, a study conducted in Hawaii and the Virgin Islands implicated a sunscreen, oxybenzone, which can cause significant deformities in coral larvae and death.

It is estimated that 4,000 to 6,000 tons of sunscreen are released each year in tropical reef areas by the 78 million tourists who visit them. Thus, 10% of the world’s coral reefs would be threatened by sunscreens! The consequences are serious because corals represent a habitat for many marine species, but they are also a precious food resource for the neighboring populations; finally, they protect the coasts by forming a very effective barrier against the elements of the open sea.

The consequences on marine animals

Corals are not the only species threatened by the components of sunscreen products. One study has also suggested significant effects on certain planktonic species. One study showed that some sunscreens released into the water promote the appearance of hydrogen peroxide (hydrogen peroxide, H2O2), a powerful oxidant that can affect the growth and development of plankton. It has also been shown that organic sunscreens accumulate in marine filter feeders such as mussels.

After all its controversies, a first ban on the marketing of sunscreen products was voted in Hawaii in May 2018. This measure will concern all products containing the following organic filters: oxybenzone and octinoxate. They will only be provided in case of exceptional medical prescription. This new law will come into force in the summer of 2021.

In the European Union, this type of law has not yet been addressed, but a first step was taken in 2006 in favor of consumers. The project aimed to guarantee equal or superior protection to UVA compared to UVB. Thus, as we have seen above, the consumer is protected from the most harmful radiation.

The impact of sunscreen products on consumers and on the environment is no longer to be demonstrated. However, the legislation does not seem to want to change the habits of consumers. Today, as a chemist, formulator and manufacturer, PolymerExpert offers a solution to reduce the impact of sunscreen products.

A few years ago, PolymerExpert developed ExpertGel®. This water-soluble polymer is an innovative gelling agent; its viscosity increases with temperature. In solution in water, the product behaves like a liquid and then becomes a thick gel when the temperature increases. The gelling temperature is easily adjustable.
This property is due to the nature of the polymer. It is poloxamer, a hyperbranched copolymer composed of (B) PEO/PPO/PEO blocks linked by organic bonds of urethane and/or urea type (U).