Bioavailability of Xenobiotics in the Soil Environment.- Effects of Pesticides on Freshwater Diatoms.- The Toxic Effects of Formaldehyde on the Nervous System.- Dermal Toxicity and Environmental Contamination: Electron Transfer, Reactive Oxygen Species, Oxidative Stress, Cell Signaling, and Protection by Antioxidants.- Heavy Metals Alter the Potency of Medicinal Plants.