Exposure to environmental contaminants, including pesticides and xenobiotics, is a risk factor for the development of diseases, such as cancer and neurodegenerative disorders. As pesticide use increases in Thailand, risk of exposure increases, even though new generation pesticides are supposedly safer, because farmers and/or general public are not trained on proper handling. We have used proteomics to elucidate the modes of action of pesticides and their effects, using human cancer cell lines as model systems. Exposure of high concentrations of atrazine, a triazine herbicide, on hepatocellular carcinoma cells implicated its possible involvement in causing cardiovascular diseases. On the other hand, fipronil, a broad spectrum phenylpyrazole insecticide, affected neuronal cells by altering the expression of proteins involved in protein biosynthesis, mitochondrial function, and glucose metabolism. Proteomic studies in plants in relation to pesticides are also interesting due to their importance in agriculture sector, and chlorpyrifos, an organophosphate insecticide, showed effects on proteins involved in growth and photosynthetic activity in the leaves of Chinese kale.  Moreover, the cellular and molecular effects of xenobiotics that persist in the environment, such as perfluorinated compounds, are also of interest.