SUN CARE Melanomas UK
25 20 15 10 5 0
1981-85 4-Year Periods 2016-20 200
Basal and Squamous Cell Poland Males ■ Females ■
41
150
100
50 2003 2005 2007 2009 2011 2013 2015 2017 2019
Figure 1: Incidence rates in men and women of all ages of melanomas in UK (left) and non-melanoma skin cancers in Poland (right) during the years indicated Hudson et al found that both infrared and
use was associated with a 30% lower risk in the latter, and a 60% higher risk in the former. The authors speculated that efficacy may vary according skin type and/or the local UVA/UVB ratio.
The intensity of UVA reaching the earth’s
surface greatly exceeds that of UVB, and although both decrease with increasing latitude, the A/B ratio rises - on a typical summer day, from 25 at the equator to 45 at 60°N (e.g. Oslo).23
How UV radiation causes damage UV radiation damages DNA in several ways. In the case of UVB, which penetrates only into the epidermis, direct damage resulting from absorption of the radiation by DNA predominates, causing molecular rearrangements known as pyrimidine dimers.24 In the case of UVA, which penetrates into the
dermis, interactions with molecules generates reactive oxygen species (ROS), which damage not only DNA, but also DNA repair enzymes.24,25 ROS also convert unsaturated lipids in skin to lipid peroxides, in turning yielding reactive aldehydes, such as 4-hydroxynonenal (4-HNE) and malondialdehyde (MDA), which also attack both DNA and its repair enzymes.26-28
SPF values The SPF number is a measure of protection only against erythema (inflammation) not skin cancer, the original purpose of UV screens having been to prevent sunburn, and is measured using a wavelength similar to midday near the equator. The fact that we now know that erythema is caused mostly by UVB, but the carcinogenic effects, mostly by UVA,13
has
heightened concerns, expressed 30 years ago that high SPF labelling may increase exposure to UVA by encouraging sunbathing.29 When Andrews et al measured the UV
absorption spectra of 51 broad spectrum sunscreens, the SPF numbers averaged only 59%, and UVA attenuation only 24%, of the labelled SPF numbers.30
Furthermore, UVA
appears not to be the only wavelength against which current sunscreens provide insufficient protection.
www.personalcaremagazine.com
visible radiation increased ROS and damaged DNA in cultured fibroblasts and keratinocytes.31 Hoffmann-Dörr et al observed similar effects in cultured melanoma cells.32
Darvin et al
observed that infrared radiation increased free radicals in pig ears ex vivo, and reduced beta- carotene and lycopene (indicative of increased ROS) in human skin in vivo.33
Concordant
effects were observed by Lawrence et al in skin biopsies taken from volunteers after UV/visible borderline irradiation.34 Another potential source of ROS has been highlighted by Serpone,13
of UV screens following application. When a molecule absorbs radiation, either the energy is then dissipated as heat or radiative decay, or the molecule decomposes. All current UV filters undergo a degree
of photo-decomposition, generating other molecules that can include ROS. Hanson et al found that the ROS in an epidermal skin model exposed to simulated solar radiation decreased by 90% immediately after the application of any one of three UV screens.35 However, 60 minutes later it exceeded the
value in untreated irradiated skin on average by twofold. Though photo-decomposition of UV screens can be reduced by antioxidants, these also undergo photo-decomposition.36,37
Added
to these concerns is the separate body of evidence that many UV screens have hormone disruptive activity,38,39
the blood with lengthy elimination rates.40, 41
Environmental concerns Aside from the issue of efficacy and off-target effects, ongoing concerns about the effects of UV screens on the environment and climate warrant consideration. It has been estimated that more than 10,000 tons of UV screens enter the sea each year. Seawater off the Canary Islands contained measurable amounts of seven out of eight UV screens tested.42 Atlantic seawater near a populated Spanish
beach contained total concentrations as high as 97 mg/L.43
Owing to their high lipid-solubility and poor biodegradability, bioaccumulation of and can be absorbed into
are the effects on corals. At concentrations of only 200 ppb, benzophenone-2 caused tissue necrosis and bleaching of coral larvae, and DNA lesions in corals.45
The LC50 concentrations
of oxybenzone for some coral larvae were one tenth of those in water off the US Virgin Islands.46 In mature corals studied in situ,, four
namely decomposition
out of seven UV screens activated latent viruses and led to expulsion of the symbiotic zooxanthellae.47
have disappeared since the 1950s,48
More than half of coral reefs and
although there is still uncertainty about whether they are carbon negative or positive, there is none about their importance for the viability of seagrass meadows, which capture up to 100 Tg of carbon per year at a rate many times faster than rainforests.49 Seagrasses are also accumulating UV
screens, inhibiting chlorophyll production and nitrogen fixation.50,51
carbon.53
New technologies needed? The combined data from clinical, chemical, experimental, and environmental studies make a persuasive case for the development of new technologies. Might it be possible, for example, to boost the skin’s natural defence mechanisms against sunlight? The principal pigment that protects skin, melanin, is an aggregate of eumelanin and pheomelanin.24 The former is darker and much more efficient
as a radiation filter. It absorbs UVB, UVA, visible, and near infra-red wavelengths, dissipating the absorbed energy as heat, and is also a scavenger of free radicals. It is synthesised from the amino acid tyrosine in melanocytes, which lie at the junction of the dermis and basal layer of the epidermis. Sunlight stimulates keratinocytes to secrete a 13-amino acid polypeptide, α-MSH, which
April 2024 PERSONAL CARE The total biomass of
seagrass is diminishing by one per cent each year,52
in the process releasing up to 300 Tg of
organic UV screens has been documented in corals, fish, dolphins, molluscs, crustaceans, and algae.44 Of particular concern for climate change
Cases per 100,000 per year
Page 1 |
Page 2 |
Page 3 |
Page 4 |
Page 5 |
Page 6 |
Page 7 |
Page 8 |
Page 9 |
Page 10 |
Page 11 |
Page 12 |
Page 13 |
Page 14 |
Page 15 |
Page 16 |
Page 17 |
Page 18 |
Page 19 |
Page 20 |
Page 21 |
Page 22 |
Page 23 |
Page 24 |
Page 25 |
Page 26 |
Page 27 |
Page 28 |
Page 29 |
Page 30 |
Page 31 |
Page 32 |
Page 33 |
Page 34 |
Page 35 |
Page 36 |
Page 37 |
Page 38 |
Page 39 |
Page 40 |
Page 41 |
Page 42 |
Page 43 |
Page 44 |
Page 45 |
Page 46 |
Page 47 |
Page 48 |
Page 49 |
Page 50 |
Page 51 |
Page 52 |
Page 53 |
Page 54 |
Page 55 |
Page 56 |
Page 57 |
Page 58 |
Page 59 |
Page 60 |
Page 61 |
Page 62 |
Page 63 |
Page 64 |
Page 65 |
Page 66 |
Page 67 |
Page 68 |
Page 69 |
Page 70 |
Page 71 |
Page 72 |
Page 73 |
Page 74 |
Page 75 |
Page 76 |
Page 77 |
Page 78 |
Page 79 |
Page 80 |
Page 81 |
Page 82 |
Page 83 |
Page 84 |
Page 85 |
Page 86 |
Page 87 |
Page 88 |
Page 89 |
Page 90 |
Page 91 |
Page 92 |
Page 93 |
Page 94 |
Page 95 |
Page 96 |
Page 97 |
Page 98 |
Page 99 |
Page 100 |
Page 101 |
Page 102 |
Page 103 |
Page 104 |
Page 105 |
Page 106 |
Page 107 |
Page 108 |
Page 109 |
Page 110 |
Page 111 |
Page 112 |
Page 113 |
Page 114 |
Page 115 |
Page 116 |
Page 117 |
Page 118 |
Page 119 |
Page 120 |
Page 121 |
Page 122 |
Page 123 |
Page 124 |
Page 125 |
Page 126 |
Page 127 |
Page 128 |
Page 129 |
Page 130 |
Page 131 |
Page 132 |
Page 133 |
Page 134 |
Page 135 |
Page 136 |
Page 137 |
Page 138 |
Page 139 |
Page 140 |
Page 141 |
Page 142 |
Page 143 |
Page 144 |
Page 145 |
Page 146 |
Page 147 |
Page 148 |
Page 149 |
Page 150 |
Page 151 |
Page 152 |
Page 153 |
Page 154
