title: Concurrent beneficial (vitamin D production) and hazardous (cutaneous DNA damage) impact of repeated low-level summer sunlight exposures.
abstract: BACKGROUND
  The concurrent impact of repeated low-level summer sunlight exposures on vitamin D production and cutaneous DNA damage, potentially leading to mutagenesis and skin cancer, is unknown.
  
  
  OBJECTIVE
  This is an experimental study (i) to determine the dual impact of repeated low-level sunlight exposures on vitamin D status and DNA damage/repair (via both skin and urinary biomarkers) in light-skinned adults; and (ii) to compare outcomes following the same exposures in brown-skinned adults.
  
  
  METHODS
  Ten white (phototype II) and six South Asian volunteers (phototype V), aged 23-59 years, received 6 weeks' simulated summer sunlight exposures (95% ultraviolet A/5% ultraviolet B, 1·3 standard erythemal doses three times weekly) wearing summer clothing exposing ~35% body surface area. Assessments made were circulating 25-hydroxyvitamin D [25(OH)D], immunohistochemistry for cyclobutane pyrimidine dimer (CPD)-positive nuclei and urinary biomarkers of direct and oxidative (8-oxo-deoxyguanosine) DNA damage.
  
  
  RESULTS
  Serum 25(OH)D rose from mean 36·5 ± 13·0 to 54·3 ± 10·5 nmol L-1(14·6 ± 5·2 to 21·7 ± 4·2 ng mL-1) in phototype II vs. 17·2 ± 6·3 to 25·5 ± 9·5 nmol L-1(6·9 ± 2·5 to 10·2 ± 3·8 ng mL-1) in phototype V (P < 0·05). Phototype II skin showed CPD-positive nuclei immediately postcourse, mean 44% (range 27-84) cleared after 24 h, contrasting with minimal DNA damage and full clearance in phototype V (P < 0·001). The findings did not differ from those following single ultraviolet radiation (UVR) exposure. Urinary CPDs remained below the detection threshold in both groups; 8-oxo-deoxyguanosine was higher in phototype II than V (P = 0·002), but was unaffected by UVR.
  
  
  CONCLUSIONS
  Low-dose summer sunlight exposures confer vitamin D sufficiency in light-skinned people concurrently with low-level, nonaccumulating DNA damage. The same exposures produce minimal DNA damage but less vitamin D in brown-skinned people. This informs tailoring of sun-exposure policies.
authors.affiliation: Dermatology Research Centre, Institute of Inflammation and Repair, Faculty of Medical and Human Sciences, University of Manchester, Manchester Academic Health Science Centre, Salford Royal NHS Foundation Trust, Manchester, U.K.
authors.forename: S J
authors.initials: SJ
authors.lastname: Felton
authors.affiliation: Oxidative Stress Group, Department of Environmental and Occupational Health, Florida International University, Miami, FL, U.S.A.
authors.forename: M S
authors.initials: MS
authors.lastname: Cooke
authors.affiliation: School of Earth Atmospheric and Environmental Sciences, University of Manchester, Manchester, U.K.
authors.forename: R
authors.initials: R
authors.lastname: Kift
authors.affiliation: Department of Clinical Biochemistry, Manchester Royal Infirmary, Central Manchester NHS Foundation Trust, Manchester Academic Health Science Centre, Oxford Road, Manchester, U.K.
authors.forename: J L
authors.initials: JL
authors.lastname: Berry
authors.affiliation: School of Earth Atmospheric and Environmental Sciences, University of Manchester, Manchester, U.K.
authors.forename: A R
authors.initials: AR
authors.lastname: Webb
authors.affiliation: Oxidative Stress Group, Department of Cancer Studies and Molecular Medicine, University of Leicester, Leicester, U.K.
authors.forename: P M W
authors.initials: PM
authors.lastname: Lam
authors.affiliation: Department of Dermatology, Leiden University Medical Centre, Leiden, the Netherlands.
authors.forename: F R
authors.initials: FR
authors.lastname: de Gruijl
authors.affiliation: Centre for Biostatistics, Institute of Population Health, University of Manchester, Manchester Academic Health Science Centre, Salford Royal NHS Foundation Trust, Manchester, U.K.
authors.forename: A
authors.initials: A
authors.lastname: Vail
authors.affiliation: Dermatology Research Centre, Institute of Inflammation and Repair, Faculty of Medical and Human Sciences, University of Manchester, Manchester Academic Health Science Centre, Salford Royal NHS Foundation Trust, Manchester, U.K.
authors.forename: L E
authors.initials: LE
authors.lastname: Rhodes
mesh_terms: D000080242:8-Hydroxy-2'-Deoxyguanosine; D000293:Adolescent; D000328:Adult; D001210:Asia, Southeastern / Q000208:ethnology; D015415:Biomarkers / Q000097:blood / Q000652:urine; D004249:DNA Damage / Q000528:radiation effects*; D004260:DNA Repair / Q000502:physiology / Q000528:radiation effects; D003849:Deoxyguanosine / Q000031:analogs & derivatives / Q000652:urine; D004032:Diet; D004781:Environmental Exposure; D005260:Female; D006801:Humans; D008297:Male; D008875:Middle Aged; D011740:Pyrimidine Dimers / Q000652:urine; D012621:Seasons; D012867:Skin / Q000378:metabolism; D012878:Skin Neoplasms / Q000097:blood / Q000209:etiology / Q000652:urine; D012880:Skin Pigmentation / Q000528:radiation effects; D013472:Sunlight; D014807:Vitamin D / Q000008:administration & dosage / Q000031:analogs & derivatives / Q000096:biosynthesis* / Q000378:metabolism; D014808:Vitamin D Deficiency / Q000097:blood / Q000208:ethnology / Q000652:urine; D055815:Young Adult
chemical_list: D015415:Biomarkers; D011740:Pyrimidine Dimers; D014807:Vitamin D; D000080242:8-Hydroxy-2'-Deoxyguanosine; C104450:25-hydroxyvitamin D; D003849:Deoxyguanosine