$2-6$ Human exposure to radiation is often measured in rems $($roentgen$-$equivalent man$),$ or

millirems $($mrem$).$ The cancer risk caused by exposure to radiation is thought to be

approximately $1$ fatal cancer per $8,000$ person$-$rems of exposure $($e$.$g$.,1$ cancer death if

$8,000$ people are exposed to $1$ rem each, or $10,000$ people exposed to $0\mathrm{.}8$ rems each, etc.$).$

Natural radioactivity in the environment is thought to expose us to roughly $130$mre$\frac{m}{y}r.$

How many cancer deaths in the US $($population $260$ million$)$ would be expected from this

exposure?

$2-7$ For the following carcinogens, the US drinking water standards are given. For each, find

the lifetime individual cancer risk and the incremental cancers per year in a population of

$260$ million as computed using a standard risk assessment based on residential exposure

factors recommended by the EPA.

$(1)$ Trichloroethylene $($TCE$),0,005m\frac{g}{L}$

$(2)$ Benzene, $0\mathrm{.}005m\frac{g}{L}$

$(3)$ Arsenic, $0\mathrm{.}01m\frac{g}{L}($NJ has its own arsenic standard at $0\mathrm{.}005m\frac{g}{L}$

$(4)$ Vinyl chloride, $0\mathrm{.}002m\frac{g}{L}.$