The only UV filter to offer complete broad-spectrum protection to the whole spectrum of both UVA & UVB rays is the mineral filter Zinc Oxide.
UVA rays penetrate deep into the skin & while they are the reason we tan; they also cause skin aging & wrinkling & suppression of the immune system that can increase the incidence of cancer. UVB rays are the ones we feel the more immediate effect of as they are the cause of sunburn, but they also play a major role in skin cancer.
SPF is a measure of protection against UVB rays. So, while chemical filters can often offer excellent SPF, they are not usually that effective in broad-spectrum protection against both UVA & UVB radiation.
SAFETY PROFILE of CHEMICAL SUNSCREENS
Since chemical sunscreens are absorbed into the skin & have a lower photostability than mineral filters, they are more likely to trigger immune responses & cause allergic reactions & irritation. While some concerns have been raised about the safety of nano mineral UV filters, these are steadily being disproven & mineral sunscreens are generally considered to offer strong protection with few health concerns. Further to allergic reactions, there are more serious concerns with regards the safety of a number of chemical UV filters.
In the latest proposed rule by the FDA for sunscreen safety, 14 of the 16 UV filters have been removed from its GRASE (generally recognised as safe & effective) category. The only two UV filters still considered GRASE are the mineral filters Zinc Oxide (ZnO) & Titanium Dioxide (TiO2). Two chemical filters PABA & trolamine salicylate are now considered unsafe, while the remaining 12 require additional clinical & non-clinical data before they can be given a classification. PABA & trolamine salicylate are not currently in use in any sunscreens in the USA. In the EU the list of approved UV filters is more extensive as it contains 27 active ingredients.
A recent study by the FDA found that four common chemical UV filters in suncare products, oxybenzone, avobenzone, ecamsule & octocrylene, were absorbed into the bloodstream after just one day of use of sunscreens containing them. The fact that they were absorbed into the bloodstream does not mean they are inherently unsafe, but the chemicals were absorbed in concentrations that warranted further testing for their safety.
Animal studies of some chemical UV filters, including oxybenzone, parabens & phthalates have found they are suspected endocrine disruptors. Exposure to very high doses of phthalates has been found to disrupt the development of male genitals which could result in reduced sperm count or increased risk of testicular cancer. Phthalate use is widespread, not limited to sunscreens, however very high dose exposure would be required for these effects.
The Danish Environmental Protection Agency (EPA) also carried out a survey & health assessment of UV filters & concluded that there is insufficient information to establish the safety of most of them. For 16 of the 19 UV filters studied there was no information about their potential to cause cancer. It also concluded that while there are studies that suggest several chemical filters can interact with human sex & thyroid hormones, there isn’t enough information to determine endocrine disruption.
The most worrisome of the chemical UV filters seems to be oxybenzone as it is one of the most popular UV filters & is routinely detected in more than 96 percent of Americans. Various studies have suggested that oxybenzone can be an endocrine disruptor as it is a weak oestrogen & has potent anti-androgenic effects. One study found that adolescent boys with higher oxybenzone measurements had significantly lower total testosterone levels, while others found statistically significant relations between oxybenzone exposure & pregnancy & birth outcomes.
Oxybenzone, along with the chemical UV filter octinoxate, are also considered harmful to marine environments. Oxybenzone causes corals to bleach at lower temperatures making them more susceptible to climate change & in the presence of oxybenzone corals cannot recover or reproduce correctly. Both chemicals have been found to induce feminisation in adult male fish & increase reproductive diseases in a wide variety of marine creatures from echinoderms, to fish & mammals. They have also been attributed with some induced changes in neurological behaviours of fish. For these reasons, many places around the world, including Hawaii & Palau, have now banned sunscreens containing the chemical UV filters oxybenzone & octinoxate.
CHEMICAL SUNSCREEN FORMULATIONS
Sunscreens are very complex formulations & most chemical sunscreens do not contain a single UV filter. In most places around the world, sunscreens are now required to offer broad-spectrum protection. Sunscreen formulations usually contain one to six types of UV filters to offer varying degrees of UV protection across the spectrum.
Sunscreen formulations can contain a combination of only chemical filters or both chemical & mineral filters. A combination of UV filters can also be used to increase photostability. For example, octocrylene is often used in conjunction with the photo-unstable avobenzone to offer stability.
MicNo® & CHEMICAL UV FILTERS
Entekno Materials has designed & developed innovative MicNo® ZnO Particle Technology to allow sunscreen formulators to overcome the disadvantages associated with micron & nano size of mineral based sunscreen active ingredients. MicNo is a single novel ingredient with added value of,
|ZnO content in the sunscreen formulation||SPF||Critical Wavelength (nm)||UVA/UVB||SPF Boosting Effect|
High SPF boosting effect of MicNo® with chemical UV filter
The superior surface covering ability of MicNo & the low level of uncontrolled agglomeration it exhibits, make it an excellent ingredient to be used in conjunction with chemical UV filters. In-vitro testing by an independent lab of formulations containing 5% chemical UV filters & different concentrations of competitor ZnO & MicNo, showed that MicNo offers a high SPF boosting effect.
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