UV radiation monitoring: UV index and UV dose

Main data product pages:

Erythemal UV index | Daily erythemal UV dose

Introduction to
UV radiation
monitoring

UV radiation

UV & health

UV index

forecasts of
UV index

UV dose

example:
1 June 2002

links

Action spectra
As mentioned on the main UV radiation page, most of the UV radiation reaching the surface is UV-A. Due to the higher energy levels of UV-B, however, the UV-B component has more effect on flora and fauna than UV-A.
An action spectrum is a parameter function which describes the relative effect of energy at different wavelengths in producing a certain biological response. These effects may be at a molecular level, such as DNA damage, or at the level of the whole organism, such as plant growth. An action spectrum is used as a "weighting function" for the UV spectrum in an integration of the monochromatic UV irradiance.
The TEMIS data service provides the UV data based on two action spectra:

Erythemal UV index and UV dose

The CIE action spectrum for erythema (reddening of the skin due to sunburn), proposed by McKinlay & Diffey (1987) and adopted as a standard by the Commission Internationale de l'\'Eclairage ( International Commission on Illumination).
The erythemal UV index is an integration between 280 and 400 nm of the UV irradiance at ground level, weighted with the erythemal action spectrum.

Generalised DNA damage UV index and UV dose

An action spectrum for generalised DNA-damage, which has been determined by Setlow (1974) and was parametrised by Bernard and Seckmeyer (1997).
The DNA-damage UV index is an integration between 256 and 370 nm of the UV irradiance at ground level, weighted with the DNA-damage action spectrum.

Action spectra of the susceptibility of the human skin to erythema (sunburn) and of generalised DNA damage due to UV radiation.

The UV data currently provided is based on two these action spectra. Other action spectra can, of course, be used as well for a parametrisation of the UV index. This could be useful, as each action spectrum has a different wavelength dependency, thus giving more information as to how changes in the ozone concentration in the stratosphere affect the UV irradiance at the Earth's surface, and the possible biological effects of these changes.
For example the mammalian non-melanoma skin cancer action spectrum (De Gruijl and Van der Leun, 1994), which lies between the erythemal and DNA-damage action spectrum, but shows a sine-like wavelength dependency between 340 and 400 nm (see this external web page for a graph). Another example is the action spectrum for melanoma induction in platyfish-swordtail hybrids (Setlow et al., 1993), which has a much more significant UV-A component, indicating that ozone depletion would not have as great an influence on melanoma in these species of fish as would the responses described by other action spectra. For references to more action spectra, see for example Madronich et al. (1998).
Note that the action spectra in themselves only give an indication of the relative wavelength dependency of biological effects: the actual biological response is determined by the actual dose amount, i.e. the UV irradiance weighted with the action spectrum and integrated over the wavelength range and the exposure time, keeping in mind that the dose-response relation may not be linear.

References of the action spectra

Bernhard, G. and Seckmeyer, G., "Measurements of spectral solar UV irradiance in tropical Australia", J. Geoph. Res. 102, No. D7, 8719-8730, 1997.
De Gruijl, F.R. and Van der Leun, J.C., "Estimate of the wavelength dependency of ultraviolet cacinogenesis in humans and its relevance to the risk assessment of stratospheric ozone depletion," Health Physics 67, 319-325.
Madronich, S., McKenzie, R.L., Björn, L.O. and Caldwell, M.M., "Changes in biologically active ultraviolet radiation reaching the Earth's surface," Photochem. Photobiol. 46, 5-19, 1998.
McKinley A. and B.L. Deffey B.L., "A reference action spectrum for ultraviolet induced erythema in human skin", in Humen Exposure to Ultraviolet Radiaton: Riskes and Regulations, (W.F. Passchier and B.F.M. Bosnajakovic, eds.), International Congress Series, pp. 83-87, Elsevier, Amsterdam, The Netherlands, 1987.
Setlow, R.B., "The wavelengths in sunlight effective in producing skin cancer: a theoretical analysis", Proc. Nat. Acad. Sci., USA, 71, No. 9, 3363-3366, 1974.
Setlow, R.B., Grist, E., Thompson, K. and Woodhead, A.D., "Wavelengths effictive in induction of malignant melanoma," Proc. Nat. Acad. Sci., USA,. 90, 6666-6670, 1993.