Richard McKenzie - Academia.edu (original) (raw)

Papers by Richard McKenzie

Journal of Geophysical Research, 2003

Journal of Geophysical Research, 2003

1] The International Photolysis Frequency Measurement and Model Intercomparison (IPMMI) took plac... more 1] The International Photolysis Frequency Measurement and Model Intercomparison (IPMMI) took place in Boulder, Colorado, from 15 to 19 June 1998, aiming to investigate the level of accuracy of photolysis frequency and spectral downwelling actinic flux measurements and to explore the ability of radiative transfer models to reproduce the measurements. During this period, 2 days were selected to compare model calculations with measurements, one cloud-free and one cloudy. A series of ancillary measurements were also performed and provided parameters required as input to the models. Both measurements and modeling were blind, in the sense that no exchanges of data or calculations were allowed among the participants, and the results were objectively analyzed and compared by two independent referees. The objective of this paper is, first, to present the results of comparisons made between measured and modeled downwelling actinic flux and irradiance spectra and, second, to investigate the reasons for which some of the models or measurements deviate from the others. For clear skies the relative agreement between the 16 models depends strongly on solar zenith angle (SZA) and wavelength as well as on the input parameters used, like the extraterrestrial (ET) solar flux and the absorption cross sections. The majority of the models (11) agreed to within about ±6% for solar zenith angles smaller than 60°.Theagreementamongthemeasuredspectradependsontheopticalcharacteristicsoftheinstruments(e.g.,slitfunction,straylightrejection,andsensitivity).AftertransformingthemeasurementstoacommonJOURNALspectralresolution,twoofthethreeparticipatingspectroradiometersagreetowithin60°. The agreement among the measured spectra depends on the optical characteristics of the instruments (e.g., slit function, stray light rejection, and sensitivity). After transforming the measurements to a common JOURNAL spectral resolution, two of the three participating spectroradiometers agree to within 60°.Theagreementamongthemeasuredspectradependsontheopticalcharacteristicsoftheinstruments(e.g.,slitfunction,straylightrejection,andsensitivity).AftertransformingthemeasurementstoacommonJOURNALspectralresolution,twoofthethreeparticipatingspectroradiometersagreetowithin10% for wavelengths longer than 310 nm and at all solar zenith angles, while their differences increase when moving to shorter wavelengths. Most models agree well with the measurements (both downwelling actinic flux and global irradiance), especially at local noon, where the agreement is within a few percent. A few models exhibit significant deviations with respect either to wavelength or to solar zenith angle. Models that use the Atmospheric Laboratory for Applications and Science 3 (ATLAS-3) solar flux agree better with the measured spectra, suggesting that ATLAS-3 is probably more appropriate for radiative transfer modeling in the ultraviolet. Citation: Bais, A. F., et al., International Photolysis Frequency Measurement and Model Intercomparison (IPMMI): Spectral actinic solar flux measurements and modeling,

Photochemical & …, Jan 1, 2008

Although we live in a sunny clime, and the sun is the main source of our vitamin D, for some reas... more Although we live in a sunny clime, and the sun is the main source of our vitamin D, for some reason New Zealanders have lower vitamin D levels in their bodies than people in other comparable countries at similar latitudes. Vitamin D status is determined by blood levels of 25-hydroxyvitamin D (25OHD). Recent findings from the 1997 adult nutrition survey show a mean 25OHD level of 50 nmol/L in New Zealanders aged 15 years, considerably lower than mean values above 70 nmol/L seen in the adult US population which lives at similar latitudes as the New Zealand population, and similar to the mean level of 50 nmol/L in the UK adult population which lives at higher latitudes (i.e. further from the equator than New Zealand). 1 Mean vitamin D levels are lower still among M ori (42 nmol/L) and Pacific people (37 nmol/L). 1 Furthermore, South Asian people are likely to have low vitamin D levels because of their darker skins, and veiling with traditional dress by many Muslim immigrants also places them at increased risk of developing vitamin D deficiency. 3 Moreover, osteomalacia and rickets are conditions that have re-emerged in clinical practice. 2,3 Given our lower than expected vitamin D status, the two articles on vitamin D in this issue of the Journal, one from Christchurch which confirms the low vitamin D levels described above 4 and one from Perth (Western Australia) which reports a significant positive association between serum 25OHD levels and leg muscle strength, 3 are timely since they contain conclusions that are relevant to both clinicians and policymakers. Although the article by Inderjeeth and colleagues reports results from a sample of women aged >60 years living in Perth, 5 their findings most likely apply to older New Zealand women since the mean 25OHD of 52 nmol/L in the Perth sample was higher than the value of 43 nmol/L in New Zealand women aged 65 years in the 1997 nutrition survey; 1 and probably also applicable to New Zealand men aged 65 years who had a mean 25OHD level of 52 nmol/L. 1 The Perth study is consistent with a recent meta-analysis which found that vitamin D supplementation reduced the relative risk of falling by 22%, with an absolute risk reduction of 7%, so that the number needed to treat (NNT) to prevent one fall was 15, although the time period required for treatment is unclear as this was not provided by the authors of the meta-analysis. There is a well-described mechanism for this effect since vitamin D receptors have been identified in skeletal muscle, and vitamin D supplementation increases muscle strength by increasing the size and number of type II muscle fibres, so that gait and balance are improved. Thus, vitamin D, in combination with calcium, protects against hip fracture by increasing bone density and muscle strength. 7 URL: http://www.nzma.org.nz/journal/120-1262/2735/ © NZMA At the moment, non-government organisations, such as the Cancer Society of New Zealand and the Health Sponsorship Council, are driving the development of policy on sun exposure, vitamin D, and health, but with the focus firmly on (avoiding) sun exposure. As Livesey and colleagues discuss, a second strategy-increasing vitamin D supplementation-needs to be considered in New Zealand since vitamin D synthesis from the sun during winter for people in Christchurch is estimated to be only 60 IU per day. 4 However, a third strategy also needs to be thrown into the mix-mandatory vitamin D fortification (currently it is optional) of certain foods such as margarine and milk products, which already happens in several countries, including the US, UK, and Australia.

Exposures to UV radiation from solaria and sunlight have potentially damaging and beneficial effe... more Exposures to UV radiation from solaria and sunlight have potentially damaging and beneficial effects that are not yet fully quantified. Here we compare weighted UV irradiances relevant to erythema (sunburn) and vitamin-D production from 2 phototherapy units and 2 commercial solaria with those under clear-skies in summer and winter at Lauder New Zealand (45 ° S). We find that weighted irradiances from one solarium are an order-of-magnitude greater than for summer sunlight whereas the others are comparable with summer sunlight, and an order-of-magnitude greater than winter sunlight. For most solaria, UV-A irradiances far exceed those in sunlight, constituting a potentially serious health risk. The calculated vitamin D benefit to erythema risk ratios for the solaria are comparable to, or greater than for with summer sunlight, and significantly greater for one of the phototherapy booths (the predominantly UV-B booth). Exposure times to maintain sufficient vitamin-D without inducing eryt...

Photochemistry and Photobiology, 2015

Monitoring ambient solar UVR levels provides information on how much there is in both real time a... more Monitoring ambient solar UVR levels provides information on how much there is in both real time and historically. Quality assurance of ambient measurements of solar UVR is critical to ensuring accuracy and stability and this can be achieved by regular intercomparisons of spectral measurement systems with those of other organisations. In October and November of 2013 a solar UVR spectroradiometer from PHE was brought to Melbourne for a campaign of intercomparisons with a new Bentham spectrometer of ARPANSA and one at the Australian BOM, supported by NIWA from New Zealand. Given all three spectroradiometers have calibrations that are traceable to various national standards, the intercomparison provides a chance to determine measurement uncertainties and traceability that support UV measurement networks in Australia, New Zealand and the UK. UV Index measurements from all three systems were compared and ratios determined for clear sky conditions when the scans from each instrument were within 2 mins of each other. While wavelengths below 305 nm showed substantial differences between the PHE unit and the two other systems, overall the intercomparison results were encouraging, with mean differences in measured UV Index between the BOM/NIWA and those of PHE and ARPANSA of < 0.1% and 7.5% respectively. This article is protected by copyright. All rights reserved.

In a recent paper in Science , Kerr, (2006) quoting Oppenheimer and Alley referring to the issue ... more In a recent paper in Science , Kerr, (2006) quoting Oppenheimer and Alley referring to the issue of cli mate change and resulting sea level rise for the melting of high latitude ice sheets stated "the ice sheet problem t oday very much resembles the ozone problem of the early 1980s, before researchers recognized the Antarctic ozone h ole". There are certainly a number of parallels that can be drawn between these two important human induced changes to the atmosphere of our planet. Table 1 highlights some of these similarities and differences.

Simultaneous NO column measurements made in France in September, 1985, using several techniques, ... more Simultaneous NO column measurements made in France in September, 1985, using several techniques, are compared with one another. The observed NO distributions vary significantly from day to day. It is shown that NO measurements using IR or UV absorption are self-consistent and show good agreement with predictions from a one-dimensional photochemical model. In situ chemiluminescent measurements produced NO columns which were systematically higher than those predicted.

Daily NO2 column measurements have been made at Lauder, New Zealand (45S, 170E) since 1980. The m... more Daily NO2 column measurements have been made at Lauder, New Zealand (45S, 170E) since 1980. The measurement technique utilizes the highly structured absorptions by NO2 which are present in sunlight scattered from the zenith sky at twilight (dawn and dusk). The site is well suited to stratospheric observations because of the very clear troposphere and negligible amounts of NO2 in the boundary layer. The importance of nitrogen oxides, in particular the so called NOx species (NO and NO2), in determining stratospheric ozone concentrations has long been recognized. The NOx species catalytically destroy ozone but in the anthropogenically perturbed lower stratosphere, they can inhibit ozone depletion by converting active halogen and hydrogen compounds into their unreactive reservoirs (e.g. ClONO2 and HNO3). The dominant variation in the measured NO2 values at Lauder is the photochemically induced diurnal and annual cycles, with the El Chichon and Pinatubo volcanic eruptions producing signi...

The field of atmospheric ultraviolet radiation (UV) research is plagued with difficulties in nome... more The field of atmospheric ultraviolet radiation (UV) research is plagued with difficulties in nomenclature. The problems arise from (a) the strong wavelength dependence of UV radiation received at the Earth’s surface, (b) the ad-hoc way disparate groups have approached the subject and (c) the incorrect use of units when action spectra for different UV effects are incorporated. This report highlights some of the issues, taking vitamin-D synthesis, a beneficial effect, as a specific example. Standard vitamin-D dose (SDD) and minimum vitamin-D dose (MDD) are proposed, analogous to the standard erythema dose (SED) and minimum erythema dose (MED) that are in common use for erythema. In recognition of the fact that currently accepted action spectra may be revised in future if new data become available, it is recommended that spectrally resolved irradiance measurements are maintained and continued so that biologically effective irradiances and doses may be reprocessed.

Nature Communications, 2015

Photochemistry and Photobiology, 2015

Marathon runners spend considerable time in outdoor training for and participating in marathons. ... more Marathon runners spend considerable time in outdoor training for and participating in marathons. Outdoor runners may experience high solar ultraviolet radiation (UVR) exposure. South Africa, where running is popular, experiences high ambient solar UVR levels that may be associated with adverse health effects. This feasibility study explores the use of personal dosimeters to determine solar UVR exposure patterns and possible related acute health risks of four marathon runners during marathons and training sessions in Cape Town and Pretoria. Runners running marathons that started early in the day, and that did not exceed 4 hours, yielded low total solar UVR exposure doses (mean 0.093 SED per exposure period run, median 0.088 SED, range 0.062-0.136 SED; average of 16.54% of ambient solar UVR). Training sessions run during early morning and late afternoon presented similar results. Several challenges hindered analysis including accounting for anatomical position of personal dosimeter and natural shade. To assess health risks, hazard quotients (HQs) were calculated using a hypothetical runner's schedule. Cumulative, annual solar UVR exposure-calculated acute health risks were low (HQ = 0.024) for training sessions and moderate (HQ = 4.922) for marathon runs. While these data and calculations are based on 18 person-days, one can measure marathon runners' personal solar UVR exposure although several challenges must be overcome.

Frontiers in Environmental Science, 2015

Photochemistry and Photobiology, 2014

Cloud effects on UV Index (UVI) and total solar radiation (TR) as a function of cloud cover and s... more 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 southernhemisphere 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 shorttime 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%).

Photochemistry and Photobiology, 2012

Doses of erythemally weighted irradiances derived from polysulphone (PS) and electronic ultraviol... more Doses of erythemally weighted irradiances derived from polysulphone (PS) and electronic ultraviolet (EUV) dosimeters have been compared with measurements obtained using a reference spectroradiometer. PS dosimeters showed mean absolute deviations of 26% with a maximum deviation of 44%, the calibrated EUV dosimeters showed mean absolute deviations of 15% (maximum 33%) around noon during several test days in the northern hemisphere autumn. In the case of EUV dosimeters, measurements with various cut-off filters showed that part of the deviation from the CIE erythema action spectrum was due to a small, but significant sensitivity to visible radiation that varies between devices and which may be avoided by careful preselection. Usually the method of calibrating UV sensors by direct comparison to a reference instrument leads to reliable results. However, in some circumstances the quality of measurements made with simple sensors may be over-estimated. In the extreme case, a simple pyranometer can be used as a UV instrument, providing acceptable results for cloudless skies, but very poor results under cloudy conditions. It is concluded that while UV dosimeters are useful for their design purpose, namely to estimate personal UV exposures, they should not be regarded as an inexpensive replacement for meteorological grade instruments.

Photochemistry and Photobiology, 2007

The European light dosimeter network (ELDONET) comprises more than 40 stations in 24 countries on... more The European light dosimeter network (ELDONET) comprises more than 40 stations in 24 countries on 5 continents. The present report compares solar radiation data in the photosynthetic active radiation, UV-A (315-400 nm) and UV-B (280-315 nm) wavelength ranges for 17 stations at different latitudes on the northern and southern hemispheres for up to 10 years of monitoring. While the maximal irradiances on clear days follow a latitudinal gradient due to the cosine dependence on the solar angle, the total doses strongly depend on the local climate and atmospheric conditions as well as the day-length distribution over the year. UV-B irradiances and doses are strongly influenced by the total column ozone, which is recorded for all covered stations.

Photochemical & Photobiological Sciences, 2006

UV measurements from instruments maintained by USDA at 16 mid-latitude sites were analysed to inv... more UV measurements from instruments maintained by USDA at 16 mid-latitude sites were analysed to investigate geographic differences. Fifteen of the sites are in North America, and one is in New Zealand. The instruments measure erythemally weighted UV radiation, and the results are presented in terms of UV Index (UVI). The focus of this work is on data from 2003, but the main results are also shown for years 2002 and 2004. In the North American sites, the peak UVI values increase by ∼15% between latitudes 47 • N and 40 • N, and they show an increase with altitude of ∼15% in the first kilometer, but much smaller rates of increase above that level. Peak UV intensities in the New Zealand site (45 • S, alt. 0.37 km) exceed those at comparable latitudes and altitudes in North America by 41 ± 5%, and are more comparable with those over 1 km higher and 5 degrees closer to the equator. The number of observations on these days that exceeded various thresholds of UVI showed similar patterns. Furthermore, the number of days in which the peak values exceeded various thresholds also showed similar patterns, with the number of extreme values in New Zealand being anomalously high. For example, the only sites in North America where UVI exceeded 12 were at the high altitude sites in Colorado and Utah, for which there were 53 days, 6 days and 2 days respectively at the 3.2 km, 1.6 and 1.4 km sites. By contrast, the peak UVI at Lauder (0.37 km) exceeded 12 on 17 days. Lauder was the only site under 1 km altitude where the UVI exceeded 11 on a regular basis (48 days). The optical depths at Lauder were significantly lower than at all North American sites. These, together with the lower ozone amounts and the closer Earth-Sun separation in summer all contribute to the relatively high UV intensities at the New Zealand site. Other sites in New Zealand show similar increases compared with corresponding sites in North America, and the differences persist from year to year.

Photochemical & Photobiological Sciences, 2014

The standardisation of UV information to the public through the UV Index (UVI) has been hugely be... more The standardisation of UV information to the public through the UV Index (UVI) has been hugely beneficial since its endorsement by multiple international agencies more than 10 years ago. It has now gained widespread acceptance, and UVI values are available throughout the world from satellite instruments, groundbased measurements, and from forecasts based on model calculations. These have been useful for atmospheric scientists, health professionals (skin and eye specialists), and the general public. But the descriptors and health messages associated with the UVI scale are targeted towards European skin types and UV regimes, and are not directly applicable to the population living closer to the equator, especially for those in the high-altitude Altiplano

Photochemical & Photobiological Sciences, 2008

Irradiation in the ultraviolet wavelength range is found to be up to 50% lower in the European su... more Irradiation in the ultraviolet wavelength range is found to be up to 50% lower in the European summer compared to sites with comparable latitudes in New Zealand. We have developed a method to quantitatively attribute the causes for such differences between sites by analysis of spectra. We conclude that these large differences are caused mainly by differences in total ozone, cloudiness, aerosol loading and Sun-Earth separation. The relative contribution of clouds varies from year to year and it is site dependent. Averaged over several years we find a strong latitudinal gradient of the cloud impact within Europe, with much less cloud attenuation in southern Europe. Due to the differences in total ozone and aerosol loading, the UV-B levels are generally lower in Europe compared to New Zealand. It is likely that inter-hemispheric differences will change in coming decades due to a combination of changes in ozone concentrations, air pollution and cloudiness as a result of climate change. However, since the future evolution of these major parameters is highly uncertain, the magnitude and even the sign of such changes are not known yet.

Photochemical & Photobiological Sciences, 2012

We investigate the relationship between blood serum 25-hydroxyvitamin D (25(OH)D) and UV exposure... more 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 twoarm 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. † Current address:

Journal of Geophysical Research, 2003

Journal of Geophysical Research, 2003

1] The International Photolysis Frequency Measurement and Model Intercomparison (IPMMI) took plac... more 1] The International Photolysis Frequency Measurement and Model Intercomparison (IPMMI) took place in Boulder, Colorado, from 15 to 19 June 1998, aiming to investigate the level of accuracy of photolysis frequency and spectral downwelling actinic flux measurements and to explore the ability of radiative transfer models to reproduce the measurements. During this period, 2 days were selected to compare model calculations with measurements, one cloud-free and one cloudy. A series of ancillary measurements were also performed and provided parameters required as input to the models. Both measurements and modeling were blind, in the sense that no exchanges of data or calculations were allowed among the participants, and the results were objectively analyzed and compared by two independent referees. The objective of this paper is, first, to present the results of comparisons made between measured and modeled downwelling actinic flux and irradiance spectra and, second, to investigate the reasons for which some of the models or measurements deviate from the others. For clear skies the relative agreement between the 16 models depends strongly on solar zenith angle (SZA) and wavelength as well as on the input parameters used, like the extraterrestrial (ET) solar flux and the absorption cross sections. The majority of the models (11) agreed to within about ±6% for solar zenith angles smaller than 60°.Theagreementamongthemeasuredspectradependsontheopticalcharacteristicsoftheinstruments(e.g.,slitfunction,straylightrejection,andsensitivity).AftertransformingthemeasurementstoacommonJOURNALspectralresolution,twoofthethreeparticipatingspectroradiometersagreetowithin60°. The agreement among the measured spectra depends on the optical characteristics of the instruments (e.g., slit function, stray light rejection, and sensitivity). After transforming the measurements to a common JOURNAL spectral resolution, two of the three participating spectroradiometers agree to within 60°.Theagreementamongthemeasuredspectradependsontheopticalcharacteristicsoftheinstruments(e.g.,slitfunction,straylightrejection,andsensitivity).AftertransformingthemeasurementstoacommonJOURNALspectralresolution,twoofthethreeparticipatingspectroradiometersagreetowithin10% for wavelengths longer than 310 nm and at all solar zenith angles, while their differences increase when moving to shorter wavelengths. Most models agree well with the measurements (both downwelling actinic flux and global irradiance), especially at local noon, where the agreement is within a few percent. A few models exhibit significant deviations with respect either to wavelength or to solar zenith angle. Models that use the Atmospheric Laboratory for Applications and Science 3 (ATLAS-3) solar flux agree better with the measured spectra, suggesting that ATLAS-3 is probably more appropriate for radiative transfer modeling in the ultraviolet. Citation: Bais, A. F., et al., International Photolysis Frequency Measurement and Model Intercomparison (IPMMI): Spectral actinic solar flux measurements and modeling,

Photochemical & …, Jan 1, 2008

Although we live in a sunny clime, and the sun is the main source of our vitamin D, for some reas... more Although we live in a sunny clime, and the sun is the main source of our vitamin D, for some reason New Zealanders have lower vitamin D levels in their bodies than people in other comparable countries at similar latitudes. Vitamin D status is determined by blood levels of 25-hydroxyvitamin D (25OHD). Recent findings from the 1997 adult nutrition survey show a mean 25OHD level of 50 nmol/L in New Zealanders aged 15 years, considerably lower than mean values above 70 nmol/L seen in the adult US population which lives at similar latitudes as the New Zealand population, and similar to the mean level of 50 nmol/L in the UK adult population which lives at higher latitudes (i.e. further from the equator than New Zealand). 1 Mean vitamin D levels are lower still among M ori (42 nmol/L) and Pacific people (37 nmol/L). 1 Furthermore, South Asian people are likely to have low vitamin D levels because of their darker skins, and veiling with traditional dress by many Muslim immigrants also places them at increased risk of developing vitamin D deficiency. 3 Moreover, osteomalacia and rickets are conditions that have re-emerged in clinical practice. 2,3 Given our lower than expected vitamin D status, the two articles on vitamin D in this issue of the Journal, one from Christchurch which confirms the low vitamin D levels described above 4 and one from Perth (Western Australia) which reports a significant positive association between serum 25OHD levels and leg muscle strength, 3 are timely since they contain conclusions that are relevant to both clinicians and policymakers. Although the article by Inderjeeth and colleagues reports results from a sample of women aged >60 years living in Perth, 5 their findings most likely apply to older New Zealand women since the mean 25OHD of 52 nmol/L in the Perth sample was higher than the value of 43 nmol/L in New Zealand women aged 65 years in the 1997 nutrition survey; 1 and probably also applicable to New Zealand men aged 65 years who had a mean 25OHD level of 52 nmol/L. 1 The Perth study is consistent with a recent meta-analysis which found that vitamin D supplementation reduced the relative risk of falling by 22%, with an absolute risk reduction of 7%, so that the number needed to treat (NNT) to prevent one fall was 15, although the time period required for treatment is unclear as this was not provided by the authors of the meta-analysis. There is a well-described mechanism for this effect since vitamin D receptors have been identified in skeletal muscle, and vitamin D supplementation increases muscle strength by increasing the size and number of type II muscle fibres, so that gait and balance are improved. Thus, vitamin D, in combination with calcium, protects against hip fracture by increasing bone density and muscle strength. 7 URL: http://www.nzma.org.nz/journal/120-1262/2735/ © NZMA At the moment, non-government organisations, such as the Cancer Society of New Zealand and the Health Sponsorship Council, are driving the development of policy on sun exposure, vitamin D, and health, but with the focus firmly on (avoiding) sun exposure. As Livesey and colleagues discuss, a second strategy-increasing vitamin D supplementation-needs to be considered in New Zealand since vitamin D synthesis from the sun during winter for people in Christchurch is estimated to be only 60 IU per day. 4 However, a third strategy also needs to be thrown into the mix-mandatory vitamin D fortification (currently it is optional) of certain foods such as margarine and milk products, which already happens in several countries, including the US, UK, and Australia.

Exposures to UV radiation from solaria and sunlight have potentially damaging and beneficial effe... more Exposures to UV radiation from solaria and sunlight have potentially damaging and beneficial effects that are not yet fully quantified. Here we compare weighted UV irradiances relevant to erythema (sunburn) and vitamin-D production from 2 phototherapy units and 2 commercial solaria with those under clear-skies in summer and winter at Lauder New Zealand (45 ° S). We find that weighted irradiances from one solarium are an order-of-magnitude greater than for summer sunlight whereas the others are comparable with summer sunlight, and an order-of-magnitude greater than winter sunlight. For most solaria, UV-A irradiances far exceed those in sunlight, constituting a potentially serious health risk. The calculated vitamin D benefit to erythema risk ratios for the solaria are comparable to, or greater than for with summer sunlight, and significantly greater for one of the phototherapy booths (the predominantly UV-B booth). Exposure times to maintain sufficient vitamin-D without inducing eryt...

Photochemistry and Photobiology, 2015

Monitoring ambient solar UVR levels provides information on how much there is in both real time a... more Monitoring ambient solar UVR levels provides information on how much there is in both real time and historically. Quality assurance of ambient measurements of solar UVR is critical to ensuring accuracy and stability and this can be achieved by regular intercomparisons of spectral measurement systems with those of other organisations. In October and November of 2013 a solar UVR spectroradiometer from PHE was brought to Melbourne for a campaign of intercomparisons with a new Bentham spectrometer of ARPANSA and one at the Australian BOM, supported by NIWA from New Zealand. Given all three spectroradiometers have calibrations that are traceable to various national standards, the intercomparison provides a chance to determine measurement uncertainties and traceability that support UV measurement networks in Australia, New Zealand and the UK. UV Index measurements from all three systems were compared and ratios determined for clear sky conditions when the scans from each instrument were within 2 mins of each other. While wavelengths below 305 nm showed substantial differences between the PHE unit and the two other systems, overall the intercomparison results were encouraging, with mean differences in measured UV Index between the BOM/NIWA and those of PHE and ARPANSA of &amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;lt; 0.1% and 7.5% respectively. This article is protected by copyright. All rights reserved.

In a recent paper in Science , Kerr, (2006) quoting Oppenheimer and Alley referring to the issue ... more In a recent paper in Science , Kerr, (2006) quoting Oppenheimer and Alley referring to the issue of cli mate change and resulting sea level rise for the melting of high latitude ice sheets stated "the ice sheet problem t oday very much resembles the ozone problem of the early 1980s, before researchers recognized the Antarctic ozone h ole". There are certainly a number of parallels that can be drawn between these two important human induced changes to the atmosphere of our planet. Table 1 highlights some of these similarities and differences.

Simultaneous NO column measurements made in France in September, 1985, using several techniques, ... more Simultaneous NO column measurements made in France in September, 1985, using several techniques, are compared with one another. The observed NO distributions vary significantly from day to day. It is shown that NO measurements using IR or UV absorption are self-consistent and show good agreement with predictions from a one-dimensional photochemical model. In situ chemiluminescent measurements produced NO columns which were systematically higher than those predicted.

Daily NO2 column measurements have been made at Lauder, New Zealand (45S, 170E) since 1980. The m... more Daily NO2 column measurements have been made at Lauder, New Zealand (45S, 170E) since 1980. The measurement technique utilizes the highly structured absorptions by NO2 which are present in sunlight scattered from the zenith sky at twilight (dawn and dusk). The site is well suited to stratospheric observations because of the very clear troposphere and negligible amounts of NO2 in the boundary layer. The importance of nitrogen oxides, in particular the so called NOx species (NO and NO2), in determining stratospheric ozone concentrations has long been recognized. The NOx species catalytically destroy ozone but in the anthropogenically perturbed lower stratosphere, they can inhibit ozone depletion by converting active halogen and hydrogen compounds into their unreactive reservoirs (e.g. ClONO2 and HNO3). The dominant variation in the measured NO2 values at Lauder is the photochemically induced diurnal and annual cycles, with the El Chichon and Pinatubo volcanic eruptions producing signi...

The field of atmospheric ultraviolet radiation (UV) research is plagued with difficulties in nome... more The field of atmospheric ultraviolet radiation (UV) research is plagued with difficulties in nomenclature. The problems arise from (a) the strong wavelength dependence of UV radiation received at the Earth’s surface, (b) the ad-hoc way disparate groups have approached the subject and (c) the incorrect use of units when action spectra for different UV effects are incorporated. This report highlights some of the issues, taking vitamin-D synthesis, a beneficial effect, as a specific example. Standard vitamin-D dose (SDD) and minimum vitamin-D dose (MDD) are proposed, analogous to the standard erythema dose (SED) and minimum erythema dose (MED) that are in common use for erythema. In recognition of the fact that currently accepted action spectra may be revised in future if new data become available, it is recommended that spectrally resolved irradiance measurements are maintained and continued so that biologically effective irradiances and doses may be reprocessed.

Nature Communications, 2015

Photochemistry and Photobiology, 2015

Marathon runners spend considerable time in outdoor training for and participating in marathons. ... more Marathon runners spend considerable time in outdoor training for and participating in marathons. Outdoor runners may experience high solar ultraviolet radiation (UVR) exposure. South Africa, where running is popular, experiences high ambient solar UVR levels that may be associated with adverse health effects. This feasibility study explores the use of personal dosimeters to determine solar UVR exposure patterns and possible related acute health risks of four marathon runners during marathons and training sessions in Cape Town and Pretoria. Runners running marathons that started early in the day, and that did not exceed 4 hours, yielded low total solar UVR exposure doses (mean 0.093 SED per exposure period run, median 0.088 SED, range 0.062-0.136 SED; average of 16.54% of ambient solar UVR). Training sessions run during early morning and late afternoon presented similar results. Several challenges hindered analysis including accounting for anatomical position of personal dosimeter and natural shade. To assess health risks, hazard quotients (HQs) were calculated using a hypothetical runner&amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;#39;s schedule. Cumulative, annual solar UVR exposure-calculated acute health risks were low (HQ = 0.024) for training sessions and moderate (HQ = 4.922) for marathon runs. While these data and calculations are based on 18 person-days, one can measure marathon runners&amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;#39; personal solar UVR exposure although several challenges must be overcome.

Frontiers in Environmental Science, 2015

Photochemistry and Photobiology, 2014

Cloud effects on UV Index (UVI) and total solar radiation (TR) as a function of cloud cover and s... more 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 southernhemisphere 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 shorttime 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%).

Photochemistry and Photobiology, 2012

Doses of erythemally weighted irradiances derived from polysulphone (PS) and electronic ultraviol... more Doses of erythemally weighted irradiances derived from polysulphone (PS) and electronic ultraviolet (EUV) dosimeters have been compared with measurements obtained using a reference spectroradiometer. PS dosimeters showed mean absolute deviations of 26% with a maximum deviation of 44%, the calibrated EUV dosimeters showed mean absolute deviations of 15% (maximum 33%) around noon during several test days in the northern hemisphere autumn. In the case of EUV dosimeters, measurements with various cut-off filters showed that part of the deviation from the CIE erythema action spectrum was due to a small, but significant sensitivity to visible radiation that varies between devices and which may be avoided by careful preselection. Usually the method of calibrating UV sensors by direct comparison to a reference instrument leads to reliable results. However, in some circumstances the quality of measurements made with simple sensors may be over-estimated. In the extreme case, a simple pyranometer can be used as a UV instrument, providing acceptable results for cloudless skies, but very poor results under cloudy conditions. It is concluded that while UV dosimeters are useful for their design purpose, namely to estimate personal UV exposures, they should not be regarded as an inexpensive replacement for meteorological grade instruments.

Photochemistry and Photobiology, 2007

The European light dosimeter network (ELDONET) comprises more than 40 stations in 24 countries on... more The European light dosimeter network (ELDONET) comprises more than 40 stations in 24 countries on 5 continents. The present report compares solar radiation data in the photosynthetic active radiation, UV-A (315-400 nm) and UV-B (280-315 nm) wavelength ranges for 17 stations at different latitudes on the northern and southern hemispheres for up to 10 years of monitoring. While the maximal irradiances on clear days follow a latitudinal gradient due to the cosine dependence on the solar angle, the total doses strongly depend on the local climate and atmospheric conditions as well as the day-length distribution over the year. UV-B irradiances and doses are strongly influenced by the total column ozone, which is recorded for all covered stations.

Photochemical & Photobiological Sciences, 2006

UV measurements from instruments maintained by USDA at 16 mid-latitude sites were analysed to inv... more UV measurements from instruments maintained by USDA at 16 mid-latitude sites were analysed to investigate geographic differences. Fifteen of the sites are in North America, and one is in New Zealand. The instruments measure erythemally weighted UV radiation, and the results are presented in terms of UV Index (UVI). The focus of this work is on data from 2003, but the main results are also shown for years 2002 and 2004. In the North American sites, the peak UVI values increase by ∼15% between latitudes 47 • N and 40 • N, and they show an increase with altitude of ∼15% in the first kilometer, but much smaller rates of increase above that level. Peak UV intensities in the New Zealand site (45 • S, alt. 0.37 km) exceed those at comparable latitudes and altitudes in North America by 41 ± 5%, and are more comparable with those over 1 km higher and 5 degrees closer to the equator. The number of observations on these days that exceeded various thresholds of UVI showed similar patterns. Furthermore, the number of days in which the peak values exceeded various thresholds also showed similar patterns, with the number of extreme values in New Zealand being anomalously high. For example, the only sites in North America where UVI exceeded 12 were at the high altitude sites in Colorado and Utah, for which there were 53 days, 6 days and 2 days respectively at the 3.2 km, 1.6 and 1.4 km sites. By contrast, the peak UVI at Lauder (0.37 km) exceeded 12 on 17 days. Lauder was the only site under 1 km altitude where the UVI exceeded 11 on a regular basis (48 days). The optical depths at Lauder were significantly lower than at all North American sites. These, together with the lower ozone amounts and the closer Earth-Sun separation in summer all contribute to the relatively high UV intensities at the New Zealand site. Other sites in New Zealand show similar increases compared with corresponding sites in North America, and the differences persist from year to year.

Photochemical & Photobiological Sciences, 2014

The standardisation of UV information to the public through the UV Index (UVI) has been hugely be... more The standardisation of UV information to the public through the UV Index (UVI) has been hugely beneficial since its endorsement by multiple international agencies more than 10 years ago. It has now gained widespread acceptance, and UVI values are available throughout the world from satellite instruments, groundbased measurements, and from forecasts based on model calculations. These have been useful for atmospheric scientists, health professionals (skin and eye specialists), and the general public. But the descriptors and health messages associated with the UVI scale are targeted towards European skin types and UV regimes, and are not directly applicable to the population living closer to the equator, especially for those in the high-altitude Altiplano

Photochemical & Photobiological Sciences, 2008

Irradiation in the ultraviolet wavelength range is found to be up to 50% lower in the European su... more Irradiation in the ultraviolet wavelength range is found to be up to 50% lower in the European summer compared to sites with comparable latitudes in New Zealand. We have developed a method to quantitatively attribute the causes for such differences between sites by analysis of spectra. We conclude that these large differences are caused mainly by differences in total ozone, cloudiness, aerosol loading and Sun-Earth separation. The relative contribution of clouds varies from year to year and it is site dependent. Averaged over several years we find a strong latitudinal gradient of the cloud impact within Europe, with much less cloud attenuation in southern Europe. Due to the differences in total ozone and aerosol loading, the UV-B levels are generally lower in Europe compared to New Zealand. It is likely that inter-hemispheric differences will change in coming decades due to a combination of changes in ozone concentrations, air pollution and cloudiness as a result of climate change. However, since the future evolution of these major parameters is highly uncertain, the magnitude and even the sign of such changes are not known yet.

Photochemical & Photobiological Sciences, 2012

We investigate the relationship between blood serum 25-hydroxyvitamin D (25(OH)D) and UV exposure... more 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 twoarm 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. † Current address: