To assess the damage caused by pesticides and their mixtures on humans, we designed in-vitro experiments to evaluate their cytotoxicity and genotoxicity. Three equimolar pesticide mixtures were investigated for their capability to affect cultured human peripheral blood lymphocytes. The LC50 values for cytotoxicity, using standard trypan blue dye exclusion and calculated by probit analysis, were 4.18, 5.76, and 7.5 microM for endosulfan, carbofuran, and monocrotophos, respectively. When combined in equimolar concentrations, the LC50 values for cytotoxicity were 0.7, 0.9, and 1.0 microM for monocrotophos + carbofuran, endosulfan + monocrotophos, and endosulfan + carbofuran, respectively, using the method. DNA damage was estimated using chromosomal aberrations (chromatid breaks, fragments, gaps, aneuploidy, and satellite association) and comet assays using 1/10 of the LC50 concentrations. Using a standard alkaline comet assay procedure, high concentrations of individual pesticides (0.5-4.0 microM) caused significant DNA damage as indicated by visible tail lengths. Lower concentrations (0.05-0.5 microM) of their binary mixtures could cause the same effect. The results suggest that analysis of genotoxicity may serve as an important biomarker for occupational and household exposure to pesticides, especially mixtures of pesticides, with different modes of action.

Experimental studies in our laboratory have established the role of delta-aminolevulinic acid dehydratase (ALAD) and matrix gamma-carboxyglutamic acid (MGP) gene polymorphisms in the etiology of lead toxicity. Polymorphisms in these genes influenced the levels of lead in subjects exposed to this metal. In extension to our studies, we aimed to investigate the possible role of these proteins in evolution by studying the phylogenetic relationship and divergence of ALAD and MGP genes using computational phylogenetic methods. The human ALAD and MGP protein sequences from various species were retrieved from Swiss-Prot database and were compared using Basic Local Alignment Search Tool. Multiple sequence alignment was carried out using ClustalW with defaults, and phylogenetic trees for both the genes were built using neighbor-joining method as in Mega software. Our study indicated that ALAD is a highly conserved protein with the same metal binding site distributed in all the phyla (from archaea to chordates). Phylogenetic analysis of MGP gene revealed that it had an important role in the evolution of endogenous skeleton in contrast to exoskeleton of insects. Occurrence of these genes in evolution with conserved metal binding sites strengthens the role of ALAD and MGP genes in regulating heme biosynthesis and mineralization, respectively, in evolution and helps in better understanding of lead poisoning.