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Scientific Report 2007-2009
Geophysics
G2. Solar spectrophotometry to measure O 3 , NO 2 , UV irradiance and
polysulphone dosimetry to quantify human UV exposure
The discovery of the Antarctic ozone hole in 1985 and
the stratospheric ozone (O 3 ) downward trend at middle
latitudes, observed since the 1970s, have hightened
the interest within the scientific community on a possible
increase of solar UV irradiance at the Earth’ surface.
Current evidence suggests that UV exposure is the major
causative factor in several short and long term skin
and eyes diseases, whereas the only well-established beneficial
effect of solar UV radiation is the production of
vitamin D3, essential for bones health. Although the
stratospheric O 3 downward trend is well documented
and its relationship to UV irradiance is established, the
understanding of the global UV climate, including variability
and trends, is still not easily detectable. The
role of cloud cover, aerosol and pollutants which, in
turn may have a time behavior, is still under study.
Although the availability of UV measurements of high
quality from ground-based instruments has increased in
the last decades, reliable UV time series are shorter than
the total O3 series.
In addition, most of ambient UV data consists of irradiance
data while little is still known about UV exposure.
The differently oriented body parts receive changing
levels of radiation which is itself continuously changing,
thus the quantification of human UV exposure is
a complex issue being directly linked to the features of
ambient UV irradiance under different conditions (i.e.
urban, mountain, coastal sites), as well as to individual
behavioural and cultural factors. As a result, even in areas
of relatively low ambient UV radiation it is possible
to experience relatively high personal exposure levels.
The Meteorology research group (GMET) has carried
out, since 1992, high quality UV and total ozone and nitrogen
dioxide (NO 2 ) measurements using Brewer spectrophotometry.
The Rome UV series is the longest time
series in Italy (Fig.1).
UVB-1 broad-band radiometer operational since 2000.
In the last few years the GMET group participated to
the investigation of solar UV variability in Europe [1].
That study shows that changes in solar zenith angle are
the major responsible, on a diurnal and annual basis,
and that clouds play a significant role in modifying the
UV pattern.
In addition the GMET group contributed to the validation
studies of satellite-derived total O 3 and UV data
from the Ozone Monitoring Instrument (OMI), investigating
the possible sources of uncertainty in an urban
site [2]. Besides the remote sensing activity, the GMET
group is involved in studies on the quantification of UV
exposure using polysulphone (PS) dosimetry (Fig.2).
Figure 2: PS dosimeters on the Brewer spectrophotometer
during a calibration campaign (University Campus).
Two field experiments were carried out in mountainous
areas on the Alps [3] and on the beach of a
popular sea-side location in central Italy [4] involving
volunteering skiers and sunbathers respectively. The
studies yielded new important data resulting in a better
understanding of UV exposure of outdoor occupational
and leisure activities of Italians and providing information
relevant to the future health policies regarding the
potential detrimental effects from overexposure to UV
radiation.
References
1. G. Seckmeyer et al., Photochem. Photobiol. Sci. 83, 1
(2007).
2. I. Ialongo et al., Atmos. Chem. Phys. 8, 3283 (2008).
3. A.M. Siani et al., Atmos. Chem. Phys. 8, 3749 (2008).
4. A.M. Siani et al., Photochem. Photobiol. 85, 171 (2009).
Figure 1: Climatological UV Index (thick line) at Rome
(clear sky data 1992–2008) for each day of the year. The
index is a measure of the intensity of UV radiation relevant to
effects on the human skin. Thin line is 1 standard deviation.
The color codes indicate exposure categories.
Authors
A.M. Siani, G.R. Casale, I. Ialongo
http://www.phys.uniroma1.it/gr/gmet/index.html
Erythemal Dose Rates (i.e. the incoming solar radiation
on a horizontal surface convolved with the erythema
action spectrum) have been also determined by YES
Sapienza Università di Roma 167 Dipartimento di Fisica