By Dr. Colin Michie of AUC Medical School
Dr. Colin Michie has worked as a paediatrician in the United Kingdom, Africa, the Caribbean and the Middle East. He is specialised in nutrition, haematology and infectious diseases. Now the Associate Academic Dean for the American University of the Caribbean Medical School in Sint Maarten, his enthusiasm is training medical students and healthcare teams to ensure they deliver better value health care.
Continued from previous edition…
UVA and UVB rays may be blocked from our skins in several ways. Avoiding sunshine, using hats and clothing and applying sunscreens are the main methods. Avoiding sunshine is recommended if possible: early and late in the day, levels of ultraviolet light are low.
So can you avoid the times when you go outdoors?
The reminder to “Slip, Slap, Slop and Wrap” is used to ensure we slip on clothes, slap on a hat, slop on sunscreen and wrap on sunglasses. Protection by clothes is measured in ultraviolet protection factor (UPF). Summer fabrics have a UPF in the region of six units, meaning that about 80% of ultraviolet will be blocked by them. More advanced fabrics with a UPF of 30 have been developed that are more effective blockers.
Hats often do not protect the nose well.
Sunscreens record their sun protection factor as SPF, a system developed in the 70s. The figure on the product indicates how much longer it will take for you to develop sunburn while using that product. So a product with an SPF of 2 will protect you for a shorter time than one with an SPF of 30.
Consumer reviews of sunscreens have found some embarrassing facts:
- Not all the products sold are equal: some are more effective than others. Sunscreen “pills” for instance are ineffective. It would be worth consulting a website to find out which are optimal. You should always use a product that blocks both UVB and UVA.
- Sunscreens need to be put on as directed – most of us tend to use too little.
- Almost all products need to be reapplied after several hours in order to maintain adequate protection, irrespective of their SPF, water resistance or other qualities.
So when venturing outside into the sunshine, a combination of measures is likely to be most effective. This is particularly important with children, for whom hats and clothing are not always effective. A good sunscreen used regularly will be needed on St. Maarten to ensure they are completely protected. When finding a sunscreen for yourself or your family, it is worth recalling that all creatures exposed to ultraviolet light have developed defensive mechanisms against it.
Those cells that multiply rapidly such as stem cells in particular are defended, often with pigments such as melanin. Corals themselves, for instance, employ a range of molecules made by the algae within them to protect themselves against this irradiation. Sunscreens use three main systems to limit ultraviolet light reaching the skin. Some of the creams on sale mix the three types.
First, inorganic atoms such as zinc or titanium can be used to physically reflect ultraviolet light (sun blocking). Compounds such as green coffee or lignins may be added to enhance their reflection. The use of small spherical particles, or turning the zinc or titanium into very small particles or nanoparticles can also make these products more efficient protectors.
The second group are organic molecules that make a film that can absorb ultraviolet wavelengths. These include benzophenones and cinnamates. Some of these compounds are absorbed through the skin and may then be found in urine. A number of chemical agents may be added to these to improve their activity.
A third system is an organic molecule that reflects, scatters and absorbs ultraviolet. The composition of sunscreens is evolving as more effective systems are developed to reduce skin penetration and prolong active blocking of these rays. Since the first use of synthetic sunscreen in 1928, there has been considerable evolution in these products.
In order to reduce ultraviolet-induced tissue damage, agents to block ultraviolet light have been added to a wide range of cosmetic products including moisturisers, lip balms, hair sprays, shampoos and other makeup compounds. It is important to observe that the same ultraviolet blocking compounds, both inorganic and organic, have many industrial applications, as they are used to protect many products such as plastics against degradation by sunlight. Studies in Swiss lakes and Chinese seas have all identified inorganic and organic UV blocking compounds in the water, the fish and the corals.
Scientists have reported that ultraviolet blocking compounds can contribute to coral bleaching and death. These are thought to include both organic films and inorganic reflectors. At a governmental level, some rapid responses have followed. In May, first Hawaii then our local Bonaire banned the sale of sunscreens containing the compounds oxybenzone and octinoxate. A number of coral “parks” such as those in Mexico have banned these compounds previously on the grounds that they do not biodegrade in the same way as the mineral or inorganic screens. There have been moves in other tourist areas with coral reefs, such as here in St. Maarten, led by Nature Foundation, to recommend safer alternative sunscreen compounds.
Corals around St. Maarten are currently threatened by warm water, acidification of the water by high carbon dioxide levels, changes in the nutrients in the sea, the impact of hurricanes and a shortage of oxygen. Possibly extra stresses from organic sunscreens may add to reef damage in the areas where we swim or dive, or where contaminated water flows into the sea. A study carried out by Nature Foundation here in St. Maarten reported in early September that there was new coral bleaching both inside and around the Man of War Shoal Marine Protected Area, so that every effort to save corals needs to be made now.
The issues with ultraviolet screens as environmental contaminants are clearly complex and we are learning more all the time. A coral-safe sunscreen applied properly will keep you looking younger. It will protect you and your family against cancer. It may improve life for marine creatures. What is not to like?
