Evaluation of chlorite and chlorate genotoxicity using plant bioassays and in vitro DNA damage tests.

In the last few years chlorine dioxide has been increasingly used for disinfecting drinking
water in many countries. Although it does not react with humic substances, chlorine
dioxide added to water is reduced primarily to chlorite and chlorate ions, compounds
that are under investigation for their potential adverse effects on human health.
The aim of this research was to study the genotoxicity of chlorite and chlorate and their
mixtures. The end-points included two plant tests (chromosomal aberration test in Allium
cepa and micronucleus assay in Tradescantia, carried out at different times of exposure) and
two genotoxicity tests in human HepG2 cells (comet assay and cytokinesis-blocked micronucleus
test). Preliminary toxicity tests were carried out for both plant and HepG2 assays.
The results showed that chlorite and chlorate are able to induce chromosomal damage to
plant systems, particularly chromosomal aberrations in A. cepa root tip cells, even at
concentrations lower than the limit established by Italian normative law and WHO
guidelines.
In HepG2 cells increased DNA damage was only observed for chlorate at the lowest concentration.
No increase in micronuclei frequency was detected in any of the samples tested in
human HepG2 cells.