 Based on impurity monitor method, four different kinds of impurities are discovered in commercial hygromycin B from different suppliers and toxicities of different impurities to the cell lines are described in the following external links.Hygromycin resistance gene is frequently used as a selectable marker in research on plants.In rice "Agrobacterium"-mediated transformation system, hygromycin is used at about 30–75 mg L−1, with an average of 50 mg L−1.