A general report on the use of the Allium test as cytotoxicological and genotoxicological assay is proposed, with particular emphasis about the standardization of the test in several common applications. The intraspecific variation in Allium cepa has been overlooked, as in most investigations no mention is made about origin and denomination of the onion cultivar used. A standardization of the used material would allow a better generalization of the results, since we cannot be sure that all cultivars would give the same response. A more frequent use of transmission electron microscopy (TEM) investigation is proposed. Even if relatively time consuming and not available in all laboratories, it may help to better understand the mechanism of cytotoxicity, since many morphological characters may appear similar but be arisen from different processes observable only with TEM. About statistical testing, tests other than chi-squared may be used in case of a lower amount of data. The most commonly used statistical tests are the parametric tests ANOVA and Student's t, and the nonparametric tests Kruskal-Wallis and Mann-Whitney U, for analysis of variance. Tests should be used also to assess the minimal sample dimension for obtaining significance, since data collection (microscope observation) appears to be one of the main bottle necks of the test. Also the use of the Allium test for testing liposomes and other nanovectors for drug delivery is proposed, in order to assess the cytotoxicity of these types of medium and the possible increase in cytotoxicity of the associated drug.

The onion plant (Allium cepa L.) is a suitable indicator plant for the determination of potential genotoxic agents in the samples taken from the environment. The genotoxic level of the agent under study is reflected by structural changes of the chromosomes and their changed numbers. The chromosomes under study are taken from the meristem cells of the young growing onion roots. A healthy normal onion cell has 16 (2n = 16) chromosomes. They are relatively large and so very appropriate for the detection of morphological changes. Prior to the chromosome study the root tip cells were immersed in a 0.1% aquatic solution of colchicine which stopped the mitotic cycle continuing beyond metaphase. The changes in morphology varied from a single distortion of a single chromosome up to several morphological changes observed on many chromosomes. We identified 15 categories of morphological aberrations which are classified into three groups: chromatid damage (CtD), centromere damage (CmD) and chromosome damage (CsD). CtD includes: single break chromatid, double break chromatid, isochromatid break, multiple break chromatid, gap chromatid, centric ring chromatid, acentric ring chromatid and triradial chromosomes. CmD includes: break centromere, gap centromere, single break centromere, double break centromere and multiple break centromere. CsD includes: ring chromosomes and dicentric chromosomes. Sometimes also the chromosome number changed which occurred as aneuploidy with monosomy 2n = 15 (2n =16-1) and euploidyincreased number of the basic chromosome number (2n = 6x-8x). We identified also the translocation: t(3p-; 5p+).

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The aim of this study was to evaluate the cytotoxic and genotoxic potential of the wastewater (WW), the effectiveness of the treatment used by the wastewater treatment plant (WWTP) with sequential batch reactors (SBR) technology, and whether its final treated effluent (FTE) can compromise the water quality of the river at the location where it is discharged. We focused our research on six examples. For analytical chemistry and Allium metaphase (M) test all six samples were collected. Of these, three are so-called biotechnological patterns (WW, WW after mechanical step treatment and FTE), and three are natural riverine environmental patterns. For the micronucleus (MN) test, fish specimens were collected from three sites in the river Kamniška Bistrica. The first two sites locations are up and down the FTE outlet. Results from these areas were compared to the third site (not polluted) reference site, the so-called natural control group. Complementary study with analytical chemistry and biological tests shows that the treatment effect SBR in the Domžale–Kamnik central WWTP carried effectively proved to be efficient for the removal of the cytogenotoxic substances in treated effluent and  consequently in aquatic environment.