Melanoma and non-melanoma skin cancer are the most common types of cancer in light-skinned populations. In 2010, melanoma incidence and mortality rates were 39.8 per 100,000 and 5.8 per 100,000 people in New Zealand respectively. These rates, both incidence and mortality are the highest in the world. They directly relate to New Zealand having high levels of ambient ultraviolet radiation (UV). The main modifiable risk factor for non-melanoma and melanoma skin cancers is exposure of the skin to UV radiation. Recent research suggests that sun exposure in early life and adulthood is predictive of basal cell carcinoma (BCC) and squamous cell carcinoma (SCC) risks, whereas melanoma risk is mainly associated with sun exposure in early life. The number of blistering sunburns beween ages 15 and 20 years is strongly associated with increased melanoma risk. Given the risks associated with sunlight exposure during early life, regular sunscreen use as an adjunct to other forms of sun protection, especially protective clothing and hats are important. UV exposure in adult life is still relevant to melanoma mortality.
The energy of UV light as it passes through the skin is absorbed by the DNA, lipids and proteins, which result in direct and indirect damage to cellular structures. Cellular damage caused by UV results in sunburn, hyper pigmentation (freckles and brown sunspots), premature ageing (thickened and coarsened skin) and photocarcinogenesis (skin cancer caused by exposure to UV radiation). The temporary protection against UV provided by sunscreens is due to their active ingredients, which are classified into organic or inorganic UV filters. Organic filters (cinnamates and salicylates) absorb UV: inorganic filters (zinc oxide, titanium dioxide) reflect and scatter UV. Regular sunscreen use prevents the development of solar keratosis, squamous cell carcinoma, melanoma and photo-ageing due to UV exposure. However, these benefits are only realised if people appley sunscreen adequately, addition to practising other sun protection measures. Unfortunately, sunscreen is often applies inadequately, compromising effectiveness. Correct application of sunscreen is essential. Insufficient amounts, missing areas and exposure of the skin prior to sunscreen application are all factors that undermine the protective efficacy of sunscreens in real life. Applying sunscreen throughly and evenly before sun exposure and reapplying it every 90 – 120 minutes are simple strategies to employ. Consumer preference of sunscreen is an important aspect to consider. Sunscreens are available in cream, milk, gel and spray formulations. A sunscreen does not have to be thick and greasy to be effective, so choose the product that is right for you.
Despite the well-established benefits of UV protection, controversy has arisen regarding the safety and efficiency of sunscreens, in particular sunscreen being a cause of Vitamin D deficiency. NZ researchers have demonstrated that exposure of just the hands, face and neck (10% of skin surface area) for about 3 minutes a day in the Auckland summer through to about 60 minutes per day in the Invercargill winter is sufficient to maintain normal Vitamin D levels.
- Seek shade and minimise sun exposure, especially when the UV level is 3 or higher.
- Wear protective clothing: wide-brimmed hat, long-sleeved shirt, pants and sunglasses.
- Use a broad-spectrum SPF30+ sunscreen every day.
- Apply sunscreen liberally 15 to 20 minutes before going outdoors.
- When outdoors, reapply sunscreen every 2 hours or immediately after swimming or excessive sweating.
- Sunscreen should not be used to increase the amount of time spent outdoors.
- Solariums or sun-beds should be avoided.
- The only safe tan is a fake tan.