Standards Australia is planning to introduce a 50+ category for sunscreens with the publication of DR AS/NZS 2604 Sunscreen products—Evaluation and classification, but I think the idea is wrong. I have reviewed the new draft standard and strongly support the Cancer Council’s view that the SPF50+ rating will lead people to think that they will really get a lot more protection. I also have concerns that the protocol for water resistant claims is wildly optimistic as sitting in a spa of fresh warm water hardly emulates swimming in the surf on a summer day.
Public comment on the draft standard closes July 18 2011 It also address both the the UVA and UVB protection, which is good, as the action spectra for tanning and skin cancer are almost the same – the risk is much the same if you tan with UVA or UVB.
It is a pity that issues with nanoparticles in sunscreens is ignored. There is no onus on manufacturers to show their inclusion is safe, despite the difference in toxicity of many materials being very different at the nanoscale. This is wrong and flies in the face of the “Precautionary Principal” that is being applied to nanotechnology in Europe.
It is very difficult to apply a uniform layer of sunscreen – halve the thickness and the protection decreases by a factor of ten. As the average thickness is only 0.8 microns (0.0008 mm), it is impossible for a manually applied layer to give a consistent thickness.
Dr Don Robertson, one of my predecessors as University Radiation Officer at the University of Queensland set up a UV laboratory and did the seminal testing of hundreds of sunscreens. It was this work that lead to the SPF concept. He also developed the Robinson Berger UV Meter. We spent many hours discussing UV, its measurement and effects. His 0.8 micron deep cuvette for measuring sunscreens and the response of his UV meter to approximate the “action spectra” of skin (you need to convolve the response of the UV glass, green glass filter, phosphor and photo-detector) were great physics.
To understand the effect of thickness, imagine you are going to sell your car and are going to paint it – at midnight, using only your fingers to apply the paint. Only a severely deluded person would imagine they would do a good job and severely deluded person would see the solution as a better finger-paint.
In the workplace, the advice of the Cancer Council are often used – “Slip, Slop, Slap”, but this does not recognise the legislated “Hierarchy of Control” that must be used in the workplace. “Slip on a shirt, Slop on a hat and Slap on some sunscreen” are all forms of personal protective equipment and must be used as a last resort.
Avoidance: The ideal thing is to try to avoid sun exposure completely – any incidental exposures in Australia of a few minutes are enough to give the positive health effects.
Engineering Controls: If avoidance is not possible, then engineering shade should be tried – remembering that many shade material allow the penetration of some UV and some 70% of solar UV comes from the sky. Only deep shade is really effective.
Administrative controls like split shifts may not be practicable, but arranging work so that exposure in the middle of the day can be avoided is important. If your shadow is shorter than you are, then keep out of the sun. When the sun is overhead, then not only is the UV more intense, but the proportion of UV in the sunlight is greater. Sometimes it is possible to do maintenance work inside during the middle of the day, or schedule work on different sides of a building.
Personal Protective Equipment
- Eyes – one brand of sunglasses stopped visible light and was transparent in the UV. This actually increased UV exposure to the eye as the pupil tended to dilate. Use certified sunglasses. I have found that safety glasses are usually opaque to UV – good for tasks where good lighting in the presence of UV is important.
- Skin – some clothing is transparent to UV but not to visible light. If some materials are wet with sweat, they transmit more UV. Besides the issues with uniform coverage of sunscreens, if they do not bond with the horny layer of the skin, they tend to float off when you sweat. They need to be applied before the body sweats.
- Hats – broad brimmed hats are great and look good. Baseball caps and lifesavers caps give little protection to the face and ears.
