How well do sunscreens protect you?

How well do sunscreens protect you?

As summer holidays begin for many people in the Northern Hemisphere, increasing column inches are given to the subject of sunscreens, such as do they work, especially given the fact that the incidence of melanoma, the most deadly form of skin cancer, is growing faster than that of any other cancer.

The European Commission (EC) is expected this week to announce measures to restrict the use of the word "sunblock" and "100 per cent sun protection" on sunscreen products, says Times Online.

Meglena Kuneva, the Consumer Affairs Commissioner for Europe said that consumers need to be made aware that no product can offer total protection against the sun's damaging ultraviolet (UV) rays.

The EC is expected to announce that all sunscreen products will have to state whether they offer low, medium, high or very protection, and must not only give their Sun Protection Factor (SPF) rating for UV-B rays but also show what protection they offer against UV-A rays.

In a New Scientist article titled "Beware the A-ray", published on 30th June 2007, science writer Jessica Marshall explained the difference between UV-A and UV-B, and suggested that use of high SPF sunscreen may have given people a false sense of security because it is only the more recent products that offer some protection against damaging UV-A rays.

Apparently lawyers in the US are taking out claims against sunscreen manufacturers because they used the word "sunblock" to mislead consumers into thinking they were getting total protection against all the sun's damaging rays: both UV-B and UV-A.

While sunburn is a result of UV-B, more and more studies are linking UV-A to malignant melanomas. UV-A has a slightly longer wavelength that UV-B and the sun's rays carry between 10 and 100 times more UV-A than UV-B, depending on global position, the time of day and how thick the ozone layer is.

For many years scientists thought UV-B caused melanomas because it causes sunburn, but more recently it has been discovered that UV-A penetrates the skin more deeply, down to the layers that contains the melanocytes, the cells that produce the pigment.

Melanoma, which accounts for under 5 per cent of all skin cancers, is the abnormal growth of melanocytes. Most melanocytes are in the skin, but they also exist in other parts of the body like the eyes, ears, and digestive tract. The sooner a melanoma is detected, the higher the chances of treatment being effective and survival.

The development of melonoma is down to a number of risk factors, including: fair complexion, too much sun exposure in childhood (especially sunburn that led to blisters), increase in common and abnormal moles, a family history of melanoma, having a mole or lesion that changes or grows on the skin, and the most important one, old age.

Nobody fully understands how melonomas develop, but according to an article in e-Medicine (part of WebMD) by Dr Susan M Swetter, the process most likely follows a sequence of genetic mutations that (1) changes the way cells multiply, differentiate and die, and (2) affect the skin's sensitivity to the cancer causing effects of UV radiation.

Our understanding is further complicated by the fact that while some melanomas arise from existing moles and lesions, some studies show that over 60 per cent of them do not arise from a pre-existing pigmented mole or lesion.

Scientists believe there are a number of pathways to the development of melanoma, for instance there is a difference between melanomas that arise in people who are sun-protected, have a high number of benign moles and birthmarks, and are exposed to UV only intermittently, and those that arise in people who are not sun-protected, have a low number of moles and birthmarks but are exposed to the sun's UV rays all the time.

Trying to work out whether UV-A or UV-B is more dangerous is extremely difficult since it's virtually impossible to establish how much of each type a person is exposed to in a lifetime, which rules out epidemiological studies.

However, according to the New Scientist article, one clue can help: UV-A levels do not decrease at higher latitudes as much as UV-B levels do, and this same pattern is reflected in the incidence of melanomas compared to other skin cancers.

The Environmental Working Group (EWG) in the United Stated, who investigated 786 name-brand sunscreens and found that many of them are not safe and effective, said that as many as one in eight sunscreen products do not protect against UV-A. They have listed 131 products that they say offer very good sun protection with ingredients that have minimal health risks.

Among its advice to consumers, the EWG warns that many sunscreens break down in the sun and this lets in the damaging UV rays. They found 54 per cent of the products on the market fell into this category. They are alarmed that the US Food and Drug Administration (FDA), which is due to issue a ruling on sunscreen labelling soon, is not proposing to cover sunscreen stability.

Click here for first few paragraphs of New Scientist Article "Beware the A-Ray".

Click here for EWG page on "Which sunscreens are safest".


Why do we have to wear sunscreen? - Kevin P. Boyd (Video Medical And Professional 2020).

Section Issues On Medicine: Disease