Definition - What does Toxicity mean?
Toxicity is a chemical property that refers to the ability of a substance to negatively destabilize another chemical or biological environment. Any impurity that causes corrosion to occur on a metallic surface essentially acts as a toxin relative to that substrate and environment.
Corrosionpedia explains Toxicity
Corrosion inhibitors are organic or inorganic compounds used to reduce corrosion by forming a protective layer on a metallic surface. These inhibitors or other chemicals used to treat or prevent corrosion (e.g., coatings, solvents) may sometimes be emitted into the environment as a waste product. They then act as a toxin to living organisms due to their polluting and chemically destabilizing properties. These chemical substances disintegrate into different forms in oil, air and water. Less toxic corrosion inhibitors should be used whenever possible.