The U.S. Environmental Protection Agency (U.S. EPA) monitors air quality in the United States. Lead is among the pollutants regularly monitored and regulated. Lead is released into the atmosphere primarily by the processing of metal ores containing lead and by leadbased battery manufacturing. The effects of too much exposure to lead include neurological damage and cardiovascular disease.

Because of the Clear Air Act and its amendments, the amounts of lead in air have been decreasing for many years. The chart below shows the lead concentration in air in the United States from 2000 to 2016. Examine the data and answer the questions that follow.

a. Determine the lead concentrations in 2000 and in 2016.

b. Calculate the percent change in lead concentration that occurred from 2000 to 2016.

Calculate the percent change with the following equation:

c. How many lead atoms were in one cubic centimeter of air in 2011?

d. Examine the mass spectrum for lead shown below. How many Pb-206 atoms were in one cubic centimeter of air in 2011?

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Pb Concentration μg/m³ 0.35 0.30 0.25 0.20 0.15 0.10 0.05 Lead Air Quality 0 2000 2002 2004 2006 2008 2010 2012 2014 2016 Year