Relationship between ozone and biologically relevant UV at 4 NDACC sites.

Clouds and aerosols, as well as overhead ozone, can have large effects on ultraviolet (UV) irradiances. We use statistical methods to remove cloud effects and mean aerosol effects from spectral UV irradiance measurements to investigate the relationship between UV and total column ozone. We show that for fixed solar zenith angles (SZA), seasonal changes in ozone lead to marked changes in clear-sky UV irradiances. Such effects are larger at mid-latitudes than in the tropics. At mid-latitudes, the minimum ozone amount over the course of a year can be about 50 percent of its maximum, with the lowest values in autumn and the highest values in spring. These seasonal ozone changes lead to UV Index (UVI) values in autumn that can exceed those in spring at the same SZA by nearly a factor of two. Differences are even larger for UV spectra weighted by the action spectra for DNA-damaging UV, and for cutaneous previtamin D production. In some cases, the seasonal increase exceeds a factor of 4. The analysis experimentally demonstrates the limits of applicability of the concept of constant Radiative Amplification Factors (RAFs) for estimating effects of changes in ozone for some weighting functions. Changes in DNA-weighted UV and erythemally weighted UV are well represented by the published RAFs. However, there are large SZA dependencies in the case of UVB and vitamin D-weighted UV. For all weightings considered, RAFs calculated from the observations as a function of SZA show similar dependencies between sites, in good agreement with published values, independently of the ozone data source. High quality measurements show that natural variations in ozone are responsible for huge variations in biologically damaging UV, with seasonal changes at fixed solar zenith angles sometimes exceeding a factor of four. The measured changes from thousands of spectra agree well with calculations over a wide range of solar zenith angles.

CDKN2A testing and genetic counseling promote reductions in objectively measured sun exposure one year later.

PURPOSE: This study investigated whether genetic counseling and test reporting for the highly penetrant CDKN2A melanoma predisposition gene promoted decreases in sun exposure. METHODS: A prospective, nonequivalent control group design compared unaffected participants (N = 128, Mage = 35.24, 52% men) from (1) families known to carry a CDKN2A pathogenic variant, who received counseling about management recommendations and a positive or negative genetic test result and (2) no-test control families known not to carry a CDKN2A pathogenic variant, who received equivalent counseling based on their comparable family history. Changes in daily ultraviolet radiation (UVR) exposure (J/m2), skin pigmentation (melanin index), and sunburns between baseline and one year following counseling were compared among carriers (n = 32), noncarriers (n = 46), and no-test control participants (n = 50). RESULTS: Both carriers and no-test control participants exhibited a decrease one year later in daily UVR dose (B = -0.52, -0.33, p < 0.01). Only carriers exhibited a significant decrease in skin pigmentation at the wrist one year later (B = -0.11, p < 0.001), and both carriers and no-test control participants reported fewer sunburns than noncarriers (p < 0.05). Facial pigmentation did not change for any group. Noncarriers did not change on any measure of UVR exposure. CONCLUSIONS: These findings support the clinical utility of disclosing CDKN2A test results and providing risk management education to high-risk individuals.

Success of Montreal Protocol Demonstrated by Comparing High-Quality UV Measurements with "World Avoided" Calculations from Two Chemistry-Climate Models.

The Montreal Protocol on Substances that Deplete the Ozone Layer has been hailed as the most successful environmental treaty ever ( https://www.unenvironment.org/news-and-stories/story/montreal-protocol-triumph-treaty ). Yet, although our main concern about ozone depletion is the subsequent increase in harmful solar UV radiation at the Earth's surface, no studies to date have demonstrated its effectiveness in that regard. Here we use long-term UV Index (UVI) data derived from high-quality UV spectroradiometer measurements to demonstrate its success in curbing increases in UV radiation. Without this landmark agreement, UVI values would have increased at mid-latitude locations by approximately 20% between the early 1990s and today and would approximately quadruple at mid-latitudes by 2100. In contrast, an analysis of UVI data from multiple clean-air sites shows that maximum daily UVI values have remained essentially constant over the last ~20 years in all seasons, and may even have decreased slightly in the southern hemisphere, especially in Antarctica, where effects of ozone depletion were larger. Reconstructions of the UVI from total ozone data show evidence of increasing UVI levels in the 1980s, but unfortunately, there are no high-quality UV measurements available prior to the early 1990s to confirm these increases with direct observations.

Two methods for retrieving UV index for all cloud conditions from sky imager products or total SW radiation measurements.

Cloud effects on UV Index (UVI) and total solar radiation (TR) as a function of cloud cover and sunny conditions (from sky images) as well as of solar zenith angle (SZA) are assessed. These analyses are undertaken for a southern-hemisphere mid-latitude site where a 10-years dataset is available. It is confirmed that clouds reduce TR more than UV, in particular for obscured Sun conditions, low cloud fraction (<60%) and large SZA (>60°). Similarly, local short-time enhancement effects are stronger for TR than for UV, mainly for visible Sun conditions, large cloud fraction and large SZA. Two methods to estimate UVI are developed: (1) from sky imaging cloud cover and sunny conditions, and (2) from TR measurements. Both methods may be used in practical applications, although Method 2 shows overall the best performance, as TR allows considering cloud optical properties. The mean absolute (relative) differences of Method 2 estimations with respect to measured values are 0.17 UVI units (6.7%, for 1 min data) and 0.79 Standard Erythemal Dose (SED) units (3.9%, for daily integrations). Method 1 shows less accurate results but it is still suitable to estimate UVI: mean absolute differences are 0.37 UVI units (15%) and 1.6 SED (8.0%).

Small doses from artificial UV sources elucidate the photo-production of vitamin D.

To clarify the relation between UV exposure and vitamin D status, 201 volunteers wore personal electronic UV dosimeters during daylight hours, to record their UV exposure over a 10 week period when ambient UV levels were significantly less than the summer maxima. Blood samples to determine serum 25-hydroxyvitamin D3 [25(OH)D3] levels were taken at the end of week 4 and week 8. Participants were then given a single full-body exposure of approximately 2 SED from one of four artificial UV sources with different spectral outputs and a further blood sample taken at study completion, nominally week 10. The artificial UV exposure reversed the mean seasonal decline in 25(OH)D3. Increases in 25(OH)D3 from week 8 to week 10 were related to total UV exposure, including the ambient sun exposures. These exposures were weighted by the erythemal action spectrum and separately for three different action spectra for pre-vitamin D production. For the erythema weighting function, 25(OH)D3 increased 1.78 ± 0.25 nmol per litre per SED, a value consistent with other studies. Any differences due to age, BMI, gender, and skin reflectance were not statistically significant. Ethnicity differences were the only significant factor, with Asians producing the least vitamin D, and Maori the most. There was no statistically significant improvement in consistency between sources for any of the three pre-vitamin weightings compared with that for erythema. Further work is needed to verify which vitamin D action spectrum is most appropriate. Nevertheless, these small doses of UV from artificial sources were helpful in quantifying the relationship between UV exposure and vitamin D status among the New Zealand population.

Serum 25-hydroxyvitamin-D responses to multiple UV exposures from solaria: inferences for exposure to sunlight.

We investigate the relationship between blood serum 25-hydroxyvitamin D (25(OH)D) and UV exposure from two artificial sources. We then use the results to test the validity of the action spectrum for vitamin D production, and to infer the production from summer and winter sunlight. The results are based on a two-arm randomised clinical trial of biweekly UV exposure for 12 weeks using two different types of dermatological booths: one emitting primarily UV-A radiation, and the other emitting primarily UV-B radiation (booth A and booth B respectively). In terms of the vitamin D production per unit erythema, one of the booths mimics summer noon sunlight, while the other mimics winter noon sunlight. Blood samples were taken before and after the exposures. For all participants, the phototherapy booth treatments arrested the usual wintertime decline in 25(OH)D, and for most the treatments from either booth resulted in significant increases. The increases were highly non-linear and there was a high degree of variability in 25(OH)D and its response to UV from person to person. By the end of the 12 week period, the mean increase was >30 nmol l(-1) from a cumulative exposure of 17 SED from the UV-A booth, and twice that for the UV-B booth for which the cumulative exposure was 268 SED. Assuming a logarithmic relationship between UV and vitamin D, the results for the two booths show no obvious inconsistency in the action spectrum for pre-vitamin D production. However, further measurements with similar exposures from each booth are required to confirm its validity. A model was developed to describe the increases in serum 25(OH)D resulting from the UV exposures, which differed markedly between the two booths. The deduced initial rate of increase of 25(OH)D was approximately 5 nmol l(-1) per SED. From the large increases in 25(OH)D from each booth, along with knowledge of the spectral distribution of sunlight and assuming the currently-accepted action spectrum for photo-conversion to pre-vitamin D, we infer that the production of 25(OH)D from sunlight should be possible throughout the year, although in winter the exposures necessary to maintain optimal levels of 25(OH)D would be impractically long. This finding is at variance with the commonly-held view that no vitamin D is produced at mid-latitudes in the winter. Further work is needed to resolve that inconsistency.

Seasonal variation in vitamin D levels in the Canterbury, New Zealand population in relation to available UV radiation.

AIM: The optimal plasma 25-hydroxyvitamin D (25(OH)D) concentration is probably >75 nmol/L but in temperate regions lower levels are common. Few studies report the intensity of solar ultraviolet (UV) radiation when 25(OH)D is measured. We measured plasma 25(OH)D and incident solar UVB radiation in Christchurch and modelled the relationship between them. METHODS: 25(OH)D, total calcium (CaT), ionised calcium (CaI) and parathyroid hormone (PTH) were measured in healthy volunteers (119 female, 82 male; median age 45 years, range 18 to 83) between February and July 2004. Vitamin D-weighted UV energy measurements (dUV) for Christchurch were from the National Institute of Water and Atmospheric Research (NIWA) UV Atlas. RESULTS: In February 2004, 88% of 25(OH)D levels were below 75 nmol/L, increasing to 100% in June and July. Severe deficiency (<12.5 nmol/L) was found in 1.5% of subjects. From February to July, 25(OH)D and CaI fell and CaT rose (p<0.001,<0.01, and <0.001). There was a hyperbolic relationship between PTH and 25OHD while CaT and CaI correlated negatively with PTH (r=-0.30 and -0.33; both p<0.001). Monthly mean dUV intensity ranged from 10 kJ m-2 day-1 in Dec 2003 to 0.5 kJ m-2 day-1 in June 2004. Compartmental modelling estimated that a Christchurch person made 1200 IU/day of vitamin D in mid-summer but only 60 IU/day in midwinter. Daily supplements of 1450 or 2600 IU vitamin D3 are predicted to raise the annual minimum mean plasma 25(OH)D to 75 or 100 nmol/L respectively. CONCLUSIONS: Most Christchurch people are vitamin D deficient most of the time and a daily supplement of 2600 IU vitamin D3 would correct this.