ABSTRACT

Lead, one of the earliest metals used by humans, is poiso­ nous in all forms. It is one of the most hazardous of the toxic metals because the poison is cumulative and because the toxic effects are many and severe (1). Lead is a natu­ rally occurring bluish-gray metal found in small quantities in the earth’s crust. The natural concentration of lead is less than 10 ppb in the earth’s crust and less than 0.03 ppb in sea water. The inorganic form of lead is predominant in the environment.