Because of advances in analytical equipment and measurement techniques, trace elements of
synthesized and natural chemicals can be detected in parts per billion or even parts per trillion in
groundwater. The following comparisons may put these numbers in better perspective.
Think of one part per million as: 1 inch in 16 miles,
1 minute in 2 years,
1 cent in $10,000,1 ounce of salt in 31 tons of potato chips, or
1 bad apple in 2,000 barrels.
One part per billion compares with: 1 inch in 16,000 miles,
1 second in 32 years,
1 cent in $10 million,
1 pinch of salt in 10 tons of potato chips,
1 lob of 1,200,000 tennis matches, or
1 bad apple in 2 million barrels.
One part per trillion compares with: 1 postage stamp in an area the size of Dallas,
1 inch in 16 million miles (more than 600 times around the earth),
1 second in 320 centuries,
1 flea on 360 million elephants,
1 grain of sugar in an Olympic-sized pool, or
1 bad apple in 2 billion barrels.