In the Netherlands considerable attention has been given to the exposure from thoron progeny in dwellings. For this purpose a nationwide survey on the thoron exhalation and thoron progeny concentration has been completed in 2015. Furthermore, extensive laboratory studies have been performed to measure activity concentrations and thoron exhalation rates from regular Dutch building materials. The purpose of this study is to demonstrate if the findings from both field experiments and laboratory results are consistent. For this reason measured properties of building materials and surface barriers, in-situ measurements on air ventilation and thoron(progeny) in dwellings as well as advanced computational modelling on indoor air and aerosol behaviour have been used. The results demonstrate that median and mean thoron progeny concentrations of 0.53 and 0.64 Bq.m(-3) found in the survey are comparable with the mean concentration of 0.57 Bq.m(-3) obtained from laboratory testing and calculation. Furthermore, upper thoron progeny concentrations from the survey and the calculations are with respectively 13 and 14 Bq.m(-3) also in good agreement. Such elevated concentrations lead to an effective doses of around 4 mSv per year. The study also includes worst-case scenarios on the application of surface materials high on Th-232, and the expected reduction in thoron progeny when using mainstream mitigation measures.

Radon and thoron progenies in Dutch dwellings cause ~400 cases of lung cancer per year. Some 30% of the risk is due to thoron progeny, which demonstrates that the influence of thoron progeny is much larger than previously anticipated. This was concluded from a national survey in 2500 Dutch dwellings, built since 1930. Radon concentrations (15.6 ± 0.3 Bq m-3 on average) are correlated to type of dwelling, year of construction, ventilation system, location (soil type) and smoking behaviour of inhabitants. The survey data support the establishment of a comparatively low national reference level for radon in dwellings in the Netherlands of 100 Bq m-3, in line with recommendations by WHO and ICRP. Some 24 thousand of the 6.2 million dwellings in the Netherlands (built since 1930) are expected to exceed this level. Around 80% of these are located in the relatively small group of naturally ventilated single-family houses in two designated geographical areas. Radon concentrations above 200 Bq m-3 are rare in the Netherlands and simple and inexpensive measures will be sufficient to reduce enhanced radon concentrations to values below the national reference level. Thoron progeny concentrations (0.64 Bq m-3, on average) show correlations with year of construction and smoking behaviour. In 75 additional dwellings, a pilot study was conducted to determine the relationship between the exhalation of thoron from walls and the concentration of thoron progeny in the room. Thoron exhalation values exceeding the median value of 2.2 × 10-2 Bq m-2 s-1 by a factor 10 or more were found frequently, but enhanced concentrations of thoron progeny were measured only occasionally. Under very unfavourable conditions, however, for instance if phosphogypsum is applied as finishing material on all walls and ceilings in the house, strongly elevated thoron progeny concentrations may occur. This survey yielded a maximum recording of 13.3 Bq m-3. There is no reason to expect that such levels are specific to the Netherlands, indicating that in other regions with low radon levels, thoron may be a more important contributor to the population dose as well.

The manuscript by Zempila et al. describes the validation of TEMIS UV products (specifically daily doses for erythemal UV, Vitamin D production, and DNA-damage) with ground-based measurements at Thessaloniki, Greece. Ground-based measurements are from a multi-filter radiometer, which was calibrated against a Brewer spectrophotometer using a Neural Network (NN) technique. The NN model appears to have been developed specifically for the purpose of the paper. It presents by itself a laudable addition to the suite of methods used for measuring solar radiation at the Earth’s surface. The description of the NN method alone warrants publication. Comparisons of the NN model’s output with Brewer measurements and measurements of a YES UVB-1

In vrijwel alle Nederlandse woningen is de concentratie van zowel radon als thoron laag. Dat blijkt uit onderzoek naar radon en thoron dat het RIVM in 2013 en 2014 in ruim 2500 woningen in Nederland (bouwjaar 1930 en later) heeft uitgevoerd. Het is wereldwijd voor het eerst dat op deze schaal onderzoek is gedaan naar thoron in woningen. Radon en thoron zijn radioactieve edelgassen die van nature ontstaan in de bodem en in daarvan gemaakte bouwmaterialen. Vandaar uit kunnen ze in de woning terechtkomen. De radioactieve stoffen die ontstaan als radon en thoron vervallen, dragen bij aan het risico op longkanker. Bij radon zien we regionale verschillen. Zo is de gemiddelde concentratie in Zuid-Limburg ongeveer tweeenhalf keer zo hoog als het landelijk gemiddelde. Dit heeft waarschijnlijk te maken met verschillen in bodemtype. Maar in vergelijking met andere Europese landen is de radonconcentratie in Nederlandse woningen laag. Verder zien we dat de gemiddelde radonconcentratie in woningen, gebouwd vanaf 2000, ruim twintig procent lager is dan het landelijk gemiddelde. Daarmee is aan de eerder gemaakte afspraken tussen overheid en bouwwereld, om de straling in nieuwbouwwoningen niet te laten toenemen, voldaan. Voor thoron vallen de metingen lager uit dan verwacht. Er zijn enkele uitzonderingen, maar het aantal woningen met een meetwaarde aan de hoge kant is veel kleiner dan het RIVM op basis van een vooronderzoek uit 2012 had ingeschat. Voor thoron zijn nog geen normen of grens- waarden vastgesteld. En omdat dit het eerste grote thorononderzoek in de wereld is, is de onzekerheid in de meetresultaten groter dan bij radon het geval is. Dat maakt het interpreteren en beoordelen van de thoronmeetresultaten ingewikkeld. Ook is het precieze verband tussen de hoeveelheid thoron die vrijkomt uit pleistermaterialen, en de concentratie van vervalproducten van thoron in de woning nog niet duidelijk. Er is extra onderzoek nodig om dit beter uit te zoeken. Van nature veranderen radon en thoron in radioactieve stoffen die zich aan zwevende stofdeeltjes in huis hechten. Na inademen blijven ze achter in de longen en geven daar straling af. Die straling draagt bij aan het risico op longkanker. Hoewel de hier gemeten concentraties radon en thoron in woningen internationaal gezien laag zijn, leidt het toch nog tot zo'n vierhonderd gevallen van longkanker per jaar in Nederland. Het betreft vooral rokers. Dat komt doordat het gezondheidsrisico van radon en thoron voor rokers gemiddeld 25 keer zo groot is als voor nooit- rokers. De nieuwe schatting van het aantal gevallen van longkanker per jaar door radon en thoron valt iets lager uit dan de vorige schatting uit 2000. Ook hebben we nu een beter beeld van de bijdrage door radon (ongeveer 70 procent) en door thoron (ongeveer 30 procent).

In the presence of clouds the ability to calculate instantaneous spectral irradiance values is limited by the ability to acquire appropriate input parameters for radiative transfer solvers. However, the knowledge of the statistical characteristics of spectral irradiance as a function of season and time of the day is relevant for solar energy and health applications. For this purpose a method to derive the wavelength dependent probability density functions (PDFs) and its seasonal site variability is presented. In contrast to the UVB range, the derived PDFS at three stations in Europe (Bilthoven, Garmisch-Partenkirchen and Thessaloniki) show only minor wavelength dependence above 315 nm. But there are major differences of the PDFs that are attributed to the site specific cloud climatology at these stations. Furthermore the results suggest that the previously described relationship between air mass and bimodality is the consequence of seasonal cloud variations. For Thessaloniki it is shown that the pyranometer sample spread around the cloudless value is proportional to the secant of the solar zenith angle and therefore scales according to air mass. Cloud amount observations are utilized to associate the local maxima of the multimodal PDFs with rough cloudiness states confirming the already established interpretation of broadband data for spectral data as well. As one application example the likelihood of irradiance enhancements over the clear sky case due to clouds is assessed.

Long-term analysis of cloud effects on ultraviolet (UV) radiation on the ground using spaceborne observations requires the use of instruments that have operated consecutively. The longest data record can be built from the reflectivity measurements produced by the instruments Total Ozone Mapping Spectrometers (TOMS) flown on Nimbus 7 from 1979 to 1992, TOMS on Earth Probe from 1996 to 2005, and the Ozone Monitoring Instrument (OMI) flown on EOS Aura since 2004. The reflectivity data produced by TOMS on Earth Probe is only included until 2002. A comparison is made with cloud effects inferred from ground-based pyranometer measurements at over 83 World Radiation Data Centre stations. Modelled UV irradiances utilizing the standard reflectivity are compared with measurements of UV irradiances at eight European low-elevation stations. The reflectivity data of the two TOMS instruments shows a consistent agreement, and the required corrections are of low percentage, i.e. 2–3%. In contrast, the reflectivity product of OMI requires correction of 7–10%, and a solar angle dependency therein is more pronounced. These corrections were inferred from a comparison with pyranometer data, and tested using the UV measurements. The average reduction of UV radiation due to clouds for all sites together indicates a small trend: a diminishing cloudiness, in line with ground-based UV observations. Uncorrected implementation of the reflectivity data would have indicated the opposite.An optimal area was established for reflectivity data for the calculation of daily sums of UV radiation. It measures approximately 1.25° in latitudinal direction for square-shaped areas overhead the ground-based UV stations. Such an area can be traversed within 5 to 7 h at the average wind speeds found for the West European continent.

This paper is based on a comparative study on ultraviolet radiation (UV) measurements and UV reconstruction models for eight sites in Europe. Reconstruction models include neural network techniques and radiative transfer modeling combined with empirical relationships. The models have been validated against quality‐controlled ground‐based measurements, 8 to 20 years, on time scales ranging from daily to yearly UV sums. The standard deviations in the ratios of modeled to measured daily sums vary between 10 and 15%. The yearly sums agree within a 5% range. Depending on the availability of ancillary measurements, reconstructions have been carried out to the early 1960s. A method has been set up to educe one best estimate of the historical UV levels that takes into account the long‐term stability and underlying agreement of the models, and the agreement with actual UV measurements. Using this best estimate, the yearly sums of erythemally weighted UV irradiance showed a range of 300 kJ/m2 at 67°N to 750 kJ/m2 at 40°N. The year‐to‐year variability was lowest at 40°N with a relative variation of 4.3%; for central and northern European latitudes this year‐to‐year variation was 5.2 to 6.5%. With regard to the period 1980 to 2006, first‐order trend lines range from 0.3 ± 0.1 to 0.6 ± 0.2% per year, approximately two thirds of which can be attributed to the diminishing of cloudiness and one third to ozone decline.

Erythemal daily UV doses have been calculated using input data from the ERA‐40 reanalysis for years 1958–2002. The quality of input parameters for UV calculations has been validated with available ground based total ozone data and estimates of Cloud Modification Factor (CMF), and the results have been compared with existing UV data. Owing to limited availability of validation data especially during 1960s and 1970s the analysis focused on sites located in central and northern Europe. The current work is the first step in deriving reliable long‐term UV time series from the ERA‐40 reanalysis. Total ozone from the ERA‐40 reanalysis is affected by significant biases, especially before satellite ozone measurements were available for assimilation. Estimations of the effect of clouds on surface UV were made using global radiation (300–3000 nm) budgets at the surface because available ERA‐40 cloud data do not allow good estimates of surface daily UV doses. There are some problems with ERA‐40 solar radiation budgets which cause systematic biases in calculated daily UV doses. Comparison of calculated daily erythemal UV doses against ground‐based UV data indicate that ERA‐40 UV doses are typically overestimated by 6–18% in central and northern Europe and underestimated by 9–17% at Davos, Switzerland. Root‐mean‐square errors of the calculated daily UV doses are usually in the range of 30–40%. Trends of UV doses were calculated for the concurrent period of the TOMS satellite UV data (1979–2002). The trends of zonally averaged ERA‐40 and TOMS UV agree well and are mostly of the same sign and magnitude.

Naar schatting zullen er rond 2050 in Nederland ieder jaar ongeveer 1500 tot 2000 extra gevallen van huidkanker bijkomen doordat de ozonlaag is aangetast. Deze toename bedraagt 10 tot 12 procent van het aantal nieuwe gevallen voordat de ozonlaag aangetast werd. Als in deze schattingen het effect van de vergrijzing wordt meegenomen, zal het aantal gevallen van huidkanker nog verder stijgen. Zonder het succesvolle internationale beleid om de ozonlaag te beschermen zou de toename nog veel hoger uitkomen. Het aantal huidkankergevallen rond 2050 kan alsnog sterk worden teruggebracht als mensen, kinderen in het bijzonder, vandaag de dag verantwoord zonnen. Dit blijkt uit nieuwe berekeningen van het RIVM, dat in samenwerking met andere instituten het zogeheten AMOUR-model heeft ontwikkeld. Hiermee kunnen de gevolgen van ozonaantasting voor het UV-klimaat en voor daarmee samenhangende risico's op huidkanker worden ingeschat. Aantasting van de ozonlaag en klimaatverandering beinvloeden de intensiteit van de UV-straling op de grond en kunnen daarmee de kans op huidkanker vergroten. In dit rapport is een verbeterde versie van het AMOUR-model beschreven en (deels) gevalideerd. Het model koppelt satellietgegevens over ozon en bewolking aan berekeningen over UV-straling op de grond. Daarmee worden lokaal veranderingen in het UV-klimaat in kaart gebracht. Daarnaast gebruikt het model historische gegevens over gebruik en concentraties van ozonafbrekende stoffen. Bovendien gebruikt het scenario's voor de productie en emissie van ozonafbrekende stoffen zoals die zijn voortgekomen uit het succesvolle internationale verdrag om de ozonlaag te herstellen, het (aangescherpte) Montreal Protocol. Resultaten van Europese en mondiale scenarioberekeningen en trendanalyses zijn beschikbaar via internet in het webdossier UV, ozonlaag en klimaat. Ga naar http://www.rivm.nl/uv en kies dan het dossier UV ozonlaag en klimaat, of ga rechtstreeks naar http://www.rivm.nl/milieuportaal/dossier/uv-ozon-en-klimaat/.

Artificial Neural Networks (ANN) are efficient tools to derive solar UV radiation from measured meteorological parameters such as global radiation, aerosol optical depths and atmospheric column ozone. The ANN model has been tested with different combinations of data from the two sites Potsdam and Lindenberg, and used to reconstruct solar UV radiation at eight European sites by more than 100 years into the past. Special emphasis will be given to the discussion of small-scale characteristics of input data to the ANN model. Annual totals of UV radiation derived from reconstructed daily UV values reflect interannual variations and long-term patterns that are compatible with variabilities and changes of measured input data, in particular global dimming by about 1980/1990, subsequent global brightening, volcanic eruption effects such as that of Mt. Pinatubo, and the long-term ozone decline since the 1970s. Patterns of annual erythemal UV radiation are very similar at sites located at latitudes close to each other, but different patterns occur between UV radiation at sites in different latitude regions.

UV-B gegevens afkomstig van het Ozone Monitoring Instrument (OMI) zijn op dit moment nog onvoldoende nauwkeurig voor milieu-evaluaties. Verbetering is mogelijk door lokale concentraties van stofdeeltjes in de lucht in de berekeningen te betrekken. Dit concludeert het RIVM nadat UV-B-data van het OMI-instrument en acht grondstations in Europa zijn vergeleken. Het OMI-instrument zit aan boord van een NASA-satelliet en is erop gericht de ozonlaag te observeren, evenals luchtvervuiling en gassen die bijdragen aan de klimaatveranderingen. Nauwkeurige gegevens over UV-straling zijn nodig om het effect van de aantasting van de ozonlaag te kennen. De ozonlaag absorbeert UV-straling van de zon. Elk jaar krijgen meer dan 20 duizend Nederlanders huidkanker, van wie er ongeveer vijfhonderd overlijden. De belangrijkste oorzaak daarvan is blootstelling aan UV-B. De OMI-metingen van de hoeveelheid UV-B straling zijn 7 tot 22 procent hoger dan waarnemingen vanaf de grond. Dat komt vooral doordat er in de lucht meer stofdeeltjes zitten dan waarmee OMI rekent. Stofdeeltjes hinderen de passage van UV-straling door de atmosfeer. Ook onderschat OMI het effect van zware bewolking. Na verbetering van beide aspecten zijn UV-B gegevens van OMI beter bruikbaar voor milieu-evaluaties. De mogelijkheden hiertoe zijn aangetoond met behulp van het AMOUR-model van het RIVM. Dit model gebruikt naast satellietgegevens over ozon en bewolking, lokaal beschikbare gegevens om de hoeveelheid UV-straling op de grond te berekenen. Satellieten geven een regionaal en mondiaal beeld. Zonder satellietgegevens zouden veel extra grondstations nodig zijn om heel Europa te dekken. Echter, satellietinstrumenten degenereren, terwijl op grondstations veel nauwkeuriger en aantoonbaar stabiel gemeten wordt. Juist door de combinatie van satellietobservaties en grondwaarnemingen kan de hoeveelheid UV-B-straling het meest efficient bepaald worden. Validatie van de satellietgegevens met grondwaarnemingen over langere perioden zijn daarbij cruciaal.

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.

Satellite‐derived ultraviolet (UV) irradiances may form the basis for establishing a global UV climatology, provided that their accuracy is confirmed against ground‐based measurements of known quality. In this study, quality‐checked spectral UV irradiance measurements from four European stations (Sodankyla, Finland; Bilthoven, Netherlands; Ispra, Italy; and Thessaloniki, Greece) are compared with those derived from TOMS, based on the (version 8) data set. The aim of this study is to validate the TOMS UV irradiances and to investigate the origin of disagreements with ground‐based data. Comparisons showed that TOMS overestimates summertime noon CIE‐weighted irradiances from 6.6% at the high‐latitude site of Sodankyla up to 19% for the three other sites. The influence of clouds and aerosols on the observed differences was investigated. For the other three sites (Bilthoven, Ispra, and Thessaloniki), TOMS overestimates the irradiance at 324 nm by almost 15% even under conditions with cloud optical depth of less than 5. For cloud‐free days at Ispra and Thessaloniki, differences ranging between 3% and 20% are well correlated with aerosol optical depth.

The variability and long‐term changes in the ultraviolet (UV) climate in the Netherlands have been studied in relation to ozone and clouds, by analyzing modeled and measured values for daily, monthly, and yearly integrated erythemally weighted UV doses. At Bilthoven, Netherlands (longitude 5.19°E, latitude 52.12°N), UV irradiance measurements for the 1994–2003 period yielded a mean annual dose of 447 ± 29 kJ/m2 and a mean daily dose of 2.5 ± 0.5 kJ/m2 for June and July. On average, the maximum UV index exceeded 6.5 (i.e., 0.1625 W/m2 erythemally weighted) on 10 days per year (21 days in 2003). The mean value of measured‐to‐modeled ratios of erythemal UV irradiances was 1.00 with a standard deviation of 0.06 for days when the measured global solar radiation agrees within 5% with the cloudless sky value. Three previously introduced approaches to model cloud effects on UV doses were shown to have limitations when applied for low Sun and/or optically thick clouds, while a new approach provided the most consistent results with an average ratio of the measured‐to‐modeled daily doses of 1.02 and a standard deviation of 0.09, for all seasons and weather conditions for the period 1994–2002. Further analysis also revealed a wavelength dependency of the correlation between global solar radiation and UV radiation. Clouds, on average, reduced the daily dose of erythemal UV to 68% of the clear‐sky value, whereas for global solar radiation this was 57%. The modeled annual erythemal UV dose was 622 kJ/m2 (402 kJ/m2) averaged over the years 1979–1982, while the years 2000–2003 yield 662 kJ/m2 (448 kJ/m2) for cloudless (cloudy) conditions. In the past 25 years the highest annual doses were received in 1995 (485 kJ/m2) and 2003 (488 kJ/m2): in 1995 as a result of extremely low ozone values and moderate cloud reduction and in 2003 as a result of extremely low cloud reduction combined with moderately low ozone values. As an indication of the changes over time, a linear regression is performed showing that the annual UV dose received at the ground for all weather conditions increased with 5.5 ± 2% per decade for erythemal UV over the 1979–2003 period.