QUANTIFICATION OF BIOLOGICAL EFFECTIVENESS OF UV RADIATION - Environmental UV Radiation: Impact on Ecosystems and Human Health and Predictive Models - page 57

Table 1 . Most commonly used sensory systems for biological UV dosimetry

Biological
detector

Biological endpoint Dosage unit Application

Uracil 36 Dimer formation Dose to reduce O.D. by e -1 Long-term monitoring

Vitamin D 37 Isomerization to pre-D3 % conversion of 7 DHC Environmental monitoring

DNA 38

Inactivation,
dimer formation

H eff equivalent to 254 nm Clear tropical marine

water

Bacteriophage T7 34 Inactivation of plaque

formers

Long-term/
continuous monitoring;
measurements in lakes,
rivers, ocean

(_ln(N/N o _)

Bacterial cells
( E. coli sp.) 39

Inactivation, mutagenesis,
role of repair processes,
interactions

H eff equivalent to 254 nm Diurnal profiles, daily

totals, vertical dose
distribution in natural
water

Bacterial spores
( B. subtilis sp.) 35

Inactivation; mutagenesis;
spore photoproduct
formation

ID or H eff equivalent to 254
nm

Diurnal profiles, daily
totals, long term
monitoring, personal
dosimetry

Biofilm 40 Loss of biological activity H eff equivalent to 254 nm Long term monitoring,

personal dosimetry, trend
estimation

RODOS:
mammalian cells 41

Inhibition of cell growth H eff from relative

absorbance

Prototype

An alternative approach is to deduce the dosimetric quantity from the dose effect
curves for a certain critical biological process. For exponential dose effect relationships,
such as the inactivation curves of bacteriophage T7 or of repair deficient spores of
Bacillus subtilis , the average number of lethal hits is given by the absolute value of the
term ln( N/N 0 ), with N = number of viable individuals after irradiation and N 0 = number
of viable individuals without irradiation 34,35 . This method allows a dosimetric
characterization independent of a certain reference wavelength.
So far, in most cases simple test systems have been used as biological dosimeters
(reviewed in 42 ), such as the uracil molecule 36 , DNA 38 , bacteriophages 34 , bacteria 35,39,40 or
mammalian cells 41 (Table 1). Their action spectra agree fairly well with that for DNA
damage 18 which has been actually obtained by averaging over responses in bacteria,
bacteriophages and DNA. Induction rates for lethality, mutagenesis and dimerization
have been used to determine directly the BED, either in terms of equivalent incident
dose at 254 nm for DNA damaging capacity 38,39,40 or as number of lethal hits 34-36 . For
ecological questions, more complex dosimetric systems, such as a motility test of
flagellates 43 or survival of Daphnia have been introduced.
The advantage of a biological dosimeter stands or falls with the degree to which
its action spectrum agrees with the spectral sensitivity of the photobiological
phenomenon under consideration. Unlike the above mentioned chemical dosimeters, the
biological dosimetry systems respond sensitively to small variations at the