All of these nickel-containing materials are different in some respects and may behave differently when they come into contact with or enter the body. Toxicity and Avoidance There is a certain perception that materials which are regarded as toxic should necessarily be avoided. Just because something may be toxic, however, does not mean it should be or needs to be avoided. Gasoline is toxic but we use it every day. Chlorine and fluorine are toxic but drinking water is purposely chlorinated and fluorinated to purify and decrease tooth decay.
Ammonia is toxic but is a principal component of fertilizer production.
The list goes on. The point is that a substance can be toxic but safe to use, as long as the substance is handled in the right way and exposures are kept to acceptable levels. Gasoline is kept in sealed tanks. Chlorine and fluorine are added to water in low concentrations. Ammonia is combined with other elements to produce compounds that have completely different chemical and physical properties than ammonia.