Lead comprises 0.0013% of the earth's crust,and historically humans have been exposed frequently to lead due to it's value in metallurgy and industrial processes. Biologycally lead replaces elements such as calcium which causes a wide range of biochemical and cellular processes to go hagwire. Lead can be acutely toxic to people if exposures lead to blood concentrations above 150 ml. A more pernicious problem is that lead can be very damaging to babies and children, where expisures as low as 5 micrograms/dL in blood have been found to cause impairment in learning, behavior and cognition. Some researchers suggest there may be no safe exposure. Moreover, a report in 2000 estimated that nearly 1 million children in the U. S. had blood lead above 10 ml. While the dangers of exposures to lead paint have. been known for decades, more recently attention has been focused on the lead content of children's toys. Independent studies found lead in samples of toys to range from X to Y. Recalls of toys have not been uncommon. In 2004, for example, the consumer products safety commission had a voluntary recall of metal toys jewelry while in 2007 fisher-price recalled almost a million toys due to high levels of lead. As a result the consumer protection council of the united states issued guidance which became formal regulation limiting the lead content in baby toys in 2011.