These results confirm the fact that comet assay is a
very sensitive and rapid technique for measuring DNA
damage in individual cells. It is in fact more sensitive
than short-term test using prokaryotic organisms
(Ames test) and even yeast cells (Zimmermann test).
This could be explained by the fact that bacteria do not
posses internal metabolic activation enzyme system,
responsible for xenobiotic metabolism and the addition
of an exogenous system was not effective enough to
activate potentially genotoxic compounds in drinking
water present at very low concentrations. Yeasts, on
the other hand, do posses the metabolic enzymes
responsible for bioactivation processes, but the content
of the enzymes depend on the growth state and here we
must focus on another possible draw back of the system:
the complex cell wall. For this purpose special strains
of yeasts with higher permeability of cell wall (D7 ts1)
are used in order to increase the sensibility of the test.
Our study showed that the comet assay with HepG2
cells is very quick, simple and most sensitive method
in comparison to both other tests. These advantages
of the comet assay, offer the assay to become one of
the tests of a larger battery of tests, which are used in
genotoxicity evaluations of environmental samples,
especially drinking water samples.
While talking about the presence of potential
genotoxins in water samples, arising mainly from the
anthropogenic activities (i.e. industrial chemicals,
biocides, agrochemicals, pharmaceuticals, etc.),
we must take into consideration the (geno)toxic
compounds arising from different water treatment
strategies, especially disinfection of drinking water
by chlorination.38 New strategies for reduction of
genotoxins in drinking water (like granular activated
carbon, filtration, chemical destruction, ozone, chlorine
dioxide and monochloramine) have to be considered.
Granular activated carbon treatment has been found to
be effective for removal mutagens from drinking water.
All disinfectant chemicals appear to have the capacity of
forming mutagenic chemicals during water treatment.1,2
It has been shown that the levels of mutagenicity formed