Using the spectroscopic techniques of resonance light scattering (RLS), absorption spectroscopy, fluorescence spectroscopy, and atomic force microscopy (AFM), we studied the toxic interactions of the combined pesticides pollutants thifensulfuron and simazine with fish sperm deoxyribonucleic acid (fsDNA). The results show that the pesticides individually have relatively weak toxicity to fsDNA compared to the combined thifensulfuron–simazine pollution, which shows obvious toxic interaction with fsDNA. Thifensulfuron and simazine have a strong synergistic effect on interaction with fsDNA with a dose of 3.0 × 10 -4 mol/L thifensulfuron and 8.0 × 10 -6 mol/L simazine in Briton-Robinson (BR) buffer solution (pH 2.09).
During the past decade there was an increased focus on the fact that humans, animals, and plants are concurrently exposed to a number of chemicals via water and the environment. These chemicals may have a combined action that causes a lower or higher toxic effect than would be expected from a single compound (1,2). This has raised concerns regarding their impact on human health and the functioning and health of aquatic and terrestrial ecosystems. Consequently, combined contamination has become a more important direction in environmental science.
Thifensulfuron and simazine have recently been reported as suspected endocrine disrupters (3,4), they are also known to cause multiple types of cancers (3), and have many other effects such as interrupting regular hormone function and causing birth defects, reproductive tumors, and weight loss in mothers and embryos. Despite the fact that these drugs are used at very low levels, they are found in the environment because of their solubility and other chemical and physical properties. Thus, thifensulfuron, simazine, and their metabolites end up in natural waters and soil, which are considered serious problems for environmental safety and human health.The traditional and most frequently used methods to evaluate the toxicity of combined pollutants are biotoxicity tests, including animal toxicity tests (5–7), microorganism toxicity tests (8,9), and epiphytology investigations. Cell toxicity tests (10,11) are also commonly used. Most of the above methods are time consuming and are limited to the study of the effects of the combined contamination. The mechanism of toxicity is seldom studied.
A molecular toxicity test investigates the toxicity of combined pollutants at the molecular level (12,13). It is a simple and rapid method that can be combined with advanced experimental measurements. It is well known that contamination influences organisms by reacting with functional biological molecules such as deoxyribonucleic acid (DNA) and protein. Thus, there is great importance in directly researching the interaction between contamination and biological molecules and for learning the toxic mechanism. Spectroscopic methods, especially resonance light scattering (RLS), have been widely developed for the sensitive detection of biomolecules (14–16), pollutants (17,18), and research on the interaction of biomolecules with contamination (12,13,19,20). These spectroscopic methods are potentially powerful approaches for investigating the toxic interaction mechanism of the combined contamination with DNA in vitro (13).
In this study, the toxic mechanism of the combined contamination of thifensulfuron and simazine to fish sperm deoxyribonucleic acid (fsDNA) is investigated from the view of molecular toxicology using RLS, absorption spectroscopy, fluorescence spectroscopy, and atomic force microscopy (AFM). This work gives a new approach for investigating the toxic mechanism of combined contamination. It aims to simulate the interaction of pesticide mixtures with organisms and provides a scientific basis for the research on the toxicity mechanism of pesticides in vivo.