Analysis of Measurements and Modelling of the Biologically Active UV Solar Radiation for Selected Sites in Poland – Assessment of Photo-medical Effects

Abstract

This publication presents scenarios how to balance pro-health and detrimental effects of the UV radiation during controlled heliotherapy in order to minimize harm (erythema appearance and DNA damage) and maximize gain (increase of vitamin D level, psoriasis clearance). Referring to the literature, there is a need of finding a methodology to assess the potential risk and benefit at the moment of exposition to natural UV radiation. A method is presented of a transition from erythemally weighted UV radiation to other biological weighted radiation (such as DNA damage, psoriasis clearance, and synthesis of vitamin D3) with the use of measurements by broadband biometers (commonly used in meteorological stations) and hand-held UV index meters. The procedure has been developed analyzing the long-term measurements with the Brewer spectrophotometer at Belsk. The look-up tables containing the ratio between irradiance weighted with no-erythemal action spectra (DNA damage, psoriasis clearance, vitamin D3 synthesis) and erythemal irradiance have been determined. The calculation algorithm has been built with the use of data collected in the years 2000–2010 and verified with the data collected in the years 2011–2014. An agreement of the modelled values with the observed ones has been found. The correspondence between the modeled and the observed vitamin and DNA-damage irradiance becomes slightly worse for the solar zenith angles greater than 65°. For the antipsoriatic irradiance, the model/observation agreement appears satisfying for the whole range of solar zenith angles considered. The calculation algorithm can be effectively used to mimic vitamin and DNA-damage irradiance between 9 am and 4 pm (local time) in the spring-summer period. It is the period when more time is spent outdoors and the algorithm has the highest accuracy in the personal doses calculations. Moreover, the algorithm has also been prepared to calculate non-erythemal daily doses based on the daily erythemal doses. The procedure can be effectively used to calculate antipsoriatic, DNA-damage and vitamin daily doses from standard measurements with broadband biometers used in the UV monitoring. The erythemal daily doses of the UV radiation measured in the years 1976–2014 at Belsk are transformed to non-erythemal daily doses (vitamin D3 synthesis, DNA damage, psoriasis clearance). The monthly and yearly trends of daily doses are calculated. It is found that the trend reversed in 2005 from increasing to decreasing one. Taking this into consideration, an original method is proposed for examining the trend significance. The method is based on the generation of hypothetical time series with statistical features resembling those in the measurement time series. The statistical significance of the trends in the periods 1976-2005 and 2005-2014 is determined, analyzing the trend values of many hypothetical time series (100,000). The trend overturning in 2005 is found at Belsk in all-analyzed biologically active UV radiation. Increasing trends in the period 1976-2005 in seasonal and monthly sums of the daily doses were replaced by the decreasing trend in the years 2005-2014, which can be more apparent in seasonal sums. The sources of such trend overturning are discussed. It seems that changes of the aerosol/ clouds properties are responsible for the UV trend pattern. During Baltic 2014 field campaign, which was conducted by the author, the measurements of the UV index are used to prepare pro-healthy scenarios of safe tanning to gain the recommended dose of the vitamin D3 level due to solar radiation. A possibility of the antipsoriatic heliotherapy on the Baltic coast is also examined. It is found that individual hand-held UV indexmeters can be used to assess in-situ UV radiation doses. The sufficient daily dose of vitamin D3 from the skin synthesis could be received only if sunscreens are used after 20-30 minutes of sunbathing without any sun protection. Dermatologists suggest that sunscreens should be used all the time, which in turn causes inadequate vitamin D3 level. The examination of the antipsoriatic doses received during the Baltic 2014 campaign proves that it is possible to conduct the antipsoriatic heliotherapy there. The antipsoriatic heliotherapy was previously commonly conducted in the selected health-care centres in the Canary Islands and at the Dead Sea. The last chapter analyzes a city agglomeration of Warsaw impact on the erythemaly weighted UV radiation. Differences between erythemal doses collected by the Brewer spectrophotometers in Warsaw and at Belsk are calculated. Mean difference between both spectrophotometers midday 6 h (symmetrically around noon) doses for the clear sky is about 5%, while it was around 1%, when they were working together at the same location (Belsk). Modelled values (from the clear-sky radiation transfer model) showed that the midday 6 h doses, due to the difference in geographic location, are 2% lower in Warsaw. It allows for concluding that the specific city aerosol induces only 2% decline of erythemal radiation, which is similar to that caused by the geographic location difference. For all sky conditions the mean difference in the midday 6 h doses between two location was only 1% greater than that for the clear sky. Thus, the city agglomeration of Warsaw does not generate any specific cloudiness that could weaken the UV radiation. Pro-healthy heliotherapy is possible also in such large agglomeration and can be as effective as in the suburbs.