In this paper erythema effective UV radiant exposure data from the PHE solar network Chilton site for the 25 year period from 1991 to 2015 are presented. The year with the highest average daily erythema effective radiant exposure was 2003 at 1577 J m and the year with the lowest average daily radiant exposure was 2010 at 1149 J m. Overall, the average daily radiant exposure per year ranged from 5655 J m to 9.98 J m with the average being 1306 J m. A preliminary analysis of the data set is carried out. A statistically significant (p = 0.01) increase in annual radiant exposure of 4.4% per year was observed from 1991-1995. Thereafter a small decrease in annual erythema effective radiant exposure of 0.8% (p = 0.002) per year was observed from 1995-2015 with a slightly faster rate of decrease from 2000-2015 of 1.0% (p = 0.007) per year. In terms of seasonal analyses, a statistically significant increase in erythema effective UV radiant exposure of 5.1% (p = 0.02) per year in the summer during 1991-1995 has been found along with small decreases in spring and summer during 1995-2015 (-1.0%; p = 0.01 and -0.7%; p = 0.01 respectively) and 2000-2015 (-1.1%; p = 0.03 and -1.2%; p = 0.003 respectively). The data suggest that the erythema effective UV dose available for impacting public health has been decreasing in recent years.

Terrestrial solar ultraviolet (UV) radiation has significant implications for human health and increasing levels are a key concern regarding the impact of climate change. Monitoring solar UV radiation at the earth's surface is therefore of increasing importance. A new prototype portable CCD (charge-coupled device) spectrometer-based system has been developed that monitors UV radiation (280-400 nm) levels at the earth's surface. It has the ability to deliver this information to the public in real time. Since the instrument can operate autonomously, it is called the Autonomous Portable Solar Ultraviolet Spectroradiometer (APSUS). This instrument incorporates an Ocean Optics QE65000 spectrometer which is contained within a robust environmental housing. The APSUS system can gather reliable solar UV spectral data from approximately April to October inclusive (depending on ambient temperature) in the UK. In this study the new APSUS unit and APSUS system are presented. Example solar UV spectra and diurnal UV Index values as measured by the APSUS system in London and Weymouth in the UK in summer 2012 are shown.

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 organizations. In October and November of 2013 a solar UVR spectroradiometer from Public Health England (PHE) was brought to Melbourne for a campaign of intercomparisons with a new Bentham spectrometer of Australian Radiation Protection and Nuclear Safety Agency (ARPANSA) and one at the Australian Bureau of Meteorology (BOM), supported by New Zealand's National Institute for Water and Atmosphere (NIWA). 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 min 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.

The performance of miniature CCD array spectroradiometers, which are widely used for the assessment of personal and environmental exposures, may be affected by variations in ambient temperature. The dark signal, spectral sensitivity and wavelength position of six different array spectroradiometer models, produced by two different manufacturers, were assessed in ambient temperatures ranging from 5 °C to 40 °C. The results are presented with a discussion of the practical implications for field measurements when the instruments are used outside of a temperature controlled environment.

Public Health England has a solar network which has been established for over 25 years which measures erythema effective UV, UVA and photopic radiation. At the Chilton site there are erythema effective solar UV data available for 25 years from 1991 to 2015. Until October 2004, the data were gathered using a Solar Light R-B 500 radiometer (SL-500), which is not temperature regulated. From October 2004, the data are from a temperature regulated Solar Light R-B 501 radiometer (SL-501). A temperature correction model has been developed using overlapping SL-500 and SL-501 data from 2006 and verified using overlapping SL-500 and SL-501 data from 2005. This correction has been applied to the non-temperature regulated SL-500 Chilton data from 1991 to 2004 resulting in a 25-year dataset of SL-501 equivalent data for the analysis of long-term trends. The development and verification of this model is described.