B. Johnsen

Variability of UV Irradiance in Europe

The diurnal and annual variability of solar UV radiation in Europe is described for different latitudes, seasons and different biologic weighting functions. For the description of this variability under cloudless skies the widely used one‐dimensional version of the radiative transfer model UVSPEC is used. We reconfirm that the major factor influencing the diurnal and annual variability of UV irradiance is solar elevation. While ozone is a strong absorber of UV radiation its effect is relatively constant when compared with the temporal variability of clouds. We show the significant role that clouds play in modifying the UV climate by analyzing erythemal irradiance measurements from 28 stations in Europe in summer. On average, the daily erythemal dose under cloudless skies varies between 2.2 kJ m−2 at 70°N and 5.2 kJ m−2 at 35°N, whereas these values are reduced to 1.5–4.5 kJ m−2 if clouds are included. Thus clouds significantly reduce the monthly UV irradiation, with the smallest reductions, on average, at lower latitudes, which corresponds to the fact that it is often cloudless in the Mediterranean area in summer.

Trends in UV Irradiance of Tanning Devices in Norway: 1983–2005

Indoor tanning increases skin cancer risk, but the importance of different parts of the UV spectrum is unclear. We assessed irradiance of tanning devices in Norway for the period 1983–2005. Since 1983, all tanning models needed approval before being sold or used. UV Type 3 limits were valid from late 1992 (<0.15 W m−2 for CIE‐weighted, i.e. erythemally weighted, short and long wave irradiances). We analyzed data from 90% of the approved tanning models (n = 446 models) and two large inspection surveys in 1998/1999 and 2003 (n = 1341 tanning devices). Mean CIE‐weighted short wave irradiance of approved models increased from 0.050 W m−2 (95% confidence interval [CI] 0.045–0.055) in 1983–1992 to 0.101 W m−2 (95% CI 0.098–0.105) in 1993–2005, and mean long wave from 0.091 W m−2 (95% CI 0.088–0.095) to 0.112 W m−2 (95% CI 0.109–0.115), respectively. Inspection surveys revealed short wave irradiances much higher than that approved. In 1998–1999, only 28% (293/1034) of the devices were equipped with correct sunlamps and only 1 out of 130 inspected establishments fulfilled all requirements. In 2003, corresponding numbers were 59% (180/307) of devices and 2 out of 52 establishments. Mean short and long wave irradiances of the inspected tanning devices in 2003 were 1.5 and 3.5 times, respectively, higher than the irradiance of natural summer sun in Oslo. In conclusion, the short wave irradiance has increased in indoor tanning devices in Norway over the last 20 years. Due to the high long wave irradiance throughout this period, the percentage of short wave irradiance was much lower than for natural sun.

Modelling solar UV radiation in the past: comparison of algorithms and input data

The objectives of the COST action 726 are to establish long-term changes of UV-radiation in the past, which can only be derived by modelling with good and available proxy data. To find the best available models and input data, 16 models have been tested by modelling daily doses for two years of data measured at four stations distributed over Europe. The modelled data have been compared with the measured data, using different statistical methods. Models that use Cloud Modification Factors for the UV spectral range, derived from co-located measured global irradiance, give the best results.

Evaluation of Eye Protection Filters for Use with Dental Curing and Bleaching Lamps

Exposure to intense radiation sources in a dental clinic necessitates the use of eye protective filters to avoid blue-light photochemical retinal hazard. We have investigated the filtering quality and assessed whether the filters protect sufficiently against retinal hazards throughout the workday. Visible light transmittance of 18 protective filters was measured. These products consisted of spectacles, stationary lamp shields, and a hand-held shield intended for use in dental clinics. Nine of the 18 tested filters had adequate filtering capacity according to todays lamp technology and exposure limit values. These filters transmitted less than 0.1% of the radiation at any wavelength between 400 nm and 525 nm. Seven of the nine filters showed transmission values below the detection limit (∼10−3 %) in the wavelength band between 400 nm and 500 nm. Filters of inferior quality may prove inadequate if the use and radiation intensity of the lamps further increase. Lack of protection may also occur if a filter is used to protect against emission from a lamp with properties other than the lamp for which the filter has been intended. It is of major importance that the spectacles/shields accommodate the emission from the lamp source. The suppliers of dental radiation sources should be responsible for information on the need for and proper use of eye protecters. In addition, the filters should be marked according to testing procedures appropriate for the specific use.

Comparison of solar UV measurements performed with spectroradiometer and moderate bandwidth multichannel radiometer for different cloud conditions

A method to control spectral global irradiance data using moderate bandwidth multichannel radiometer data was analyzed. The multichannel instrument sampled at both 1 min averages and a high frequency of approximately 0.5 Hz simultaneously with the spectral data. Deviations between multichannel radiometer and spectroradiometer, caused by different angular response (cosine and azimuth), were investigated. Uncertainties due to separate sampling systems and nonideal timing were quantified and removed before data intercomparison. It is shown that high-frequency multichannel measurements, ideal synchronized to spectral measurements can be used to identify short-term unexpected errors in spectral measurements down to a level of 5%, limited by the relative angular response error between the instrument during variable cloud conditions.

Lamps as means to homogenize solar ultraviolet irradiance measurements performed with different spectroradiometers

Portable lamp irradiance calibration units of different size were used to transfer a relative calibration in a group of spectroradiometers operating at the same site. Every unit was used as normally in the field or at a home laboratory, i.e., including any errors related to the method itself. The calibration obtained for each instrument was used to reprocess their synchronous solar measurements. Solar measurements deviating by typically ± 10% got a standard deviation as low as 3-4% when corrections derived from a common lamp measurement were applied. Because instrumental features remained the same in the original and in the reprocessed solar data, the improvement of the agreement in the solar measurements was considered as an indication of a more homogeneous irradiance scale. The remaining disagreement must be a sum of the uncertainty related to the use of each calibration unit and any instrumental peculiarities. Each of the lamp units could bring the scales of the specific instrument group closer. This was especially true for distinct outlicrs in the group. Even the smallest units performed almost as well as more sophisticated equipment, and an agreement of about 5% in the sky measurements could be reached, which is better than that seen in most recent intercomparisons.

Anthropometric factors and cutaneous melanoma: Prospective data from the population-based Janus Cohort

The aim of the present study was to prospectively examine risk of cutaneous melanoma (CM) according to measured anthropometric factors, adjusted for exposure to ultraviolet radiation (UVR), in a large population‐based cohort in Norway. The Janus Cohort, including 292,851 Norwegians recruited 1972–2003, was linked to the Cancer Registry of Norway and followed for CM through 2014. Cox regression was used to estimate hazard ratios (HRs) of CM with 95% confidence intervals (CIs). Restricted cubic splines were incorporated into the Cox models to assess possible non‐linear relationships. All analyses were adjusted for attained age, indicators of UVR exposure, education, and smoking status. During a mean follow‐up of 27 years, 3,000 incident CM cases were identified. In men, CM risk was positively associated with body mass index, body surface area (BSA), height and weight (all ptrends < 0.001), and the exposure‐response curves indicated an exponential increase in risk for all anthropometric factors. Weight loss of more than 2 kg in men was associated with a 53% lower risk (HR 0.47, 95% CI: 0.39, 0.57). In women, CM risk increased with increasing BSA (ptrend = 0.002) and height (ptrend < 0.001). The shape of the height‐CM risk curve indicated an exponential increase. Our study suggests that large body size, in general, is a CM risk factor in men, and is the first to report that weight loss may reduce the risk of CM among men.

Anthropometric factors and Breslow thickness

Melanoma is the most rapidly increasing cancer form in Norway, and in 2016, 2114 men and women were diagnosed with the disease. This form of cancer is often diagnosed at an early stage, and if you follow changes in your skin you will be able to detect the cancer at an early stage. Melanoma with metastasis (spreading elsewhere in the body), however, is a serious disease that is difficult to treat, and more than 300 people die in Norway from melanoma each year. The thickness of the tumour (called Breslow thickness) is an important factor for survival after melanoma; those with a thin tumour at diagnosis live longer than those with a thick tumour. In a new Norwegian study, researchers explored associations between certain factors (called anthropometric factors ‐ such as body mass index (BMI), body surface area (BSA), height, weight and weight change) and Breslow thickness, overall and by anatomical site and histological subtype (type of melanoma). Nearly 300,000 Norwegian men and women who were enrolled into a study group called the Janus population‐based cohort 1972–2003 were followed for melanoma. By 2014, 2570 cases of melanoma with information on tumour thickness were identified. This large case‐series of incident melanomas, demonstrated positive associations between BMI, BSA, weight and Breslow thickness, and showed that Breslow thickness increased with increasing BMI, BSA and weight, before levelling off or declining at high values, suggesting that behavioural or other mechanisms apply at high values.

Anthropometric factors and Breslow thickness: prospective data on 2570 cases of cutaneous melanoma in the population-based Janus Cohort

Breslow thickness is the most important prognostic factor of localized cutaneous melanoma (CM), but associations with anthropometric factors have been sparsely and incompletely investigated.

Relevance of investigating light transmittance through red protective shields in dentistry

Thank you for the high-quality content of the BDJ and BDJ Open. However, we became aware of a recent publication that did not represent the usual up-to-date information in the field of dentistry, namely ‘A study on light transmittance through red protective shields modified with different window films’ published on 30 June 2017 in BDJ Open. Although we are convinced that the authors have the best intentions in conveying the message that clinicians’ eyes must be protected during treatments using optical radiation, we are afraid that a solution is presented to a marginal or nonexistent problem. As the wavelengths emitted by LED-based dental light-curing devices so closely match those that are most detrimental to retina and the output of these lamps are high enough to theoretically exceed the limit values in normal use within a workday, the focus should be on eye protection against blue light. In evaluating the risk of eye hazards due to optical radiation the following questions must be addressed: What is the source and magnitude of exposure? Which type of hazards can be induced? What is the exposure limit? To our knowledge, most dental lightcuring devices being produced today are LED-based and these do not emit any red or infrared radiation. There are likely to be some halogen lamps still in use, some of which may not be in accordance with the standard for dental light-curing devices (‘Powered polymerization activators’, ISO 10650:2015). Radiation outside the absorption spectrum of the most commonly used photoinitiators in the material to be cured is neither needed nor justified, and optical filters are often used to remove light of these unwanted wavelength ranges. In the absence of such filters some of these devices may theoretically emit red or near-infrared radiation. According to the ISO standard there is a maximum level for the emission of wavelengths above 515 nm (green light and longer wavelengths). When lamps comply with this standard it is highly unlikely that wavelengths outside the violet–blue range pose any threat for photochemical retinal hazard in normal use. Another potential eye hazard due to optical radiation is heat. Thermal damage to the retina and iris may be induced by visible light and near-infrared radiation. However, the output of the red and near-infrared wavelengths is not high enough to exceed the exposure limit values (International Commission on Non-Ionizing Radiation Protection. ICNIRP Guidelines on Limits of Exposure to Incoherent Visible and Infrared Radiation, 2013). During the ~ 15 years we have measured and evaluated spectral data of about 50 different lamp systems intended for use in the dental clinic, we observed only two lamps that emitted any radiation (1% of maximum value) above 700 nm (‘border’ visible/near-infrared) and those lamps were specifically made for tooth bleaching purposes. Still, the radiation output was too low to induce thermal damage to the eyes of the patient or operator in normal use. Furthermore, judging protection efficiency from the colour of the protective filters is not an accurate measure of transmittance and does not guarantee adequate protection. According to our calculations, the transmittance level should be below 0.1% in the blue light wavelength range. After measuring the transmittance of 30 commercially available orange filters, we found that about half of them were inferior as eye protection against reflected blue light.