Sun protection factors (SPF) measures UVB radiation which are the cause of sunburn. There is no standard for listing UVA blocking power. UVA radiation, penetrates deeper into the skin and causes premature aging. Both rays cause skin cancer.
An SPF 15 sunscreen protects against 93 percent of UVB rays, SPF 30 protects against 97 percent and SPF 50+ only protects against 98%. Clearly, there is only a marginal increase in protection in spite of the doubling in SPF ratings. SPF is a reference to roughly how long it takes for a person's skin to burn or turn red. In theory an SPF 15 should precent your skin from getting red for 15 times longer than if you didn't use sunscreen.
However sunscreen is rarely applied in real life as it is in lab-testing conditions, and it sweats and rubs off, so never assume you're safe for the entire period. Most people only use 1/4 or 1/2 of the required amount of sunscreen and often neglect to reapply it.
In spite of sun awareness campaigns and increased usage of sunscreen since the 1980s, melanoma is the third most commonly diagnosed cancer in males (after prostate and bowel cancer) and females (after breast and bowel cancer) In Australia. Incidence has increased by 151% in males and 46% in females between 1982 and 2007. In Australia,the age-standardized incidence rates for melanoma have increased from 26.7 per 100,00 in 1982 to 48.8 per 100,000 in 2014. These stats are from www.cancer.org.au. The data from the US reflects the same trend - the rates of melanoma are increasing. According to the skin cancer foundation in the US.....Of the seven most common cancers in the US, melanoma is the only one whose incidence is increasing.
To make matters worse, some of the chemicals in sunscreen have recently come under fire for possibly being carcinogenic and can promote DNA damage in the presence of sunlight. According to a report by the Environmental Working Group (EWG), Scientists found that oxybenzone; a chemical UV blocker, penetrates the skin and is present in urine long after sunscreen is applied. Almost all chemicals sunscreen blockers, perhaps counter-intuitively, breakdown in the presence of sunlight. In fact this is how they block UVB from penetrating the skin, like a castle wall protecting against cannonballs until the wall crumbles.
Sunscreen and SPF ratings are perhaps giving most people a very false sense of security. It encourages people to spend prolonged periods in the sun. Few people realise that although their skin hasn't burned, damage is still being done at a deeper level.
The safest option is to use sensible clothing, hat and sunglasses and keep out of the mid-day sun! It's also wise to use a zinc based sunscreen instead of a chemical sunscreen in view of the findings of recent studies. We have a more detailed story on the effect of chemicals in sunscreen in one of our earlier blogs.
Click here for to check out which organic zinc based sunscreen we love.