In 1939, the use of ddt (a powerful synthetic chemical) as an insecticide was discovered. the united states adopted its widespread use, producing up to 100 million kilograms per year (200 million pounds per year). twenty years later, severe side effects started to be reported as a result of ddt use. which was an advantage of using ddt?

Tooth enamel consists mainly of the mineral calcium hydroxyapatite, ca_10(po_4)_6(oh)_2. trace elements in teeth of archaeological specimens provide anthropologist with clues about diet and diseases of ancient people. students at hamline university measured strontium in enamel from extracted wisdom teeth by atomic absorption spectroscopy. solutions with a constant total volume of 10.0 ml contained 0.726 mg of dissolved tooth enamel plus variable concentrations of added sr. added sr find the concentration of sr in the 10 ml sample solution in parts per billion = ng/ml. find the concentration of sr in tooth enamel in parts per million = mu g/g.