Q$2(40$ pts$.).$ A consulting company recommends that the average air concentration of industrial exposure to hexavalent chromium $($chromium VI $)$ in a manufacturing facility should be $\backslash (0\mathrm{.}005\backslash$mathrm$\{$mg$\}/\backslash$mathrm$\{$m$\}^\{3\}\backslash ).$ The EPA general exposure data is summarized in the following table.

Source US$.$ EPA $(1991).$

Q $2-1.$ Using the EPA exposure data, what is the incremental lifetime CDI $(70$ yrs$)$ of chromium VI under the recommended concentration of $\backslash (0\mathrm{.}005\backslash$mathrm$\{$mg$\}/\backslash$mathrm$\{$m$\}^\{3\}\backslash )?(10$ pts $.)$

Q $2-2.$ You want to know the lifetime carcinogenic risk at the recommended concentration, so you search the database and find the dose$-$response data for chromium VI in the following table. What's the potency factor based on the data? $(10$ pts $.)$ What is the lifetime carcinogenic risk? $(5$ pts$.)$

Q $2-3.$ Is the risk from Q $2-2$ acceptable compared to the standard of $\backslash (1/10^\{6\}\backslash )($one in one million$)?(5$ pts$.)$ If not, estimate the air concentration of Chromium VI that would result in an acceptable risk. $(10$ pts$.)$