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the recommended threshhold limit value ( TLV-ACGIH) air concentration for occupational exposure to water-insoluble hexavalent chromium Cr (VI) is 0.01 mg/M^3. this concentration is based on an assumption that the individual is generally healthy and is exposed for 8 hours per day over a working lifetime ( that is from age 18 to 65 years). assuming a body weight of 78 kg and an inhalation rate of 0.63 m^3/h over the working life of the individual,
a. what is the lifetime (75y) CDI?
b. estimate the low-dose cancer risk from occupational inhalation exposure to hexavalent chromium.