Unit conversion exercises and exposure pathways (a) In Contra Costa County, California, the median indoor airborne concentration of chloroform (CHCl3) was found to be 0.4gm3. Convert this concentration to a mole fraction in parts per billion (ppb) assuming that T=293K and P=1atm. (b) The same study estimated that the mean concentration of chloroform in drinking water is 42g/L. Convert this to a mass fraction in parts per billion (ppb). (c) A typical adult inhales about 20m3 of air and ingests about 2L of water per day. Assuming that the concentrations given in (a) and (b) are appropriate, compare the exposure to chloroform via inhalation ( g inhaled per day) with the exposure via ingestion ( g swallowed per day). (d) For tetrachloroethylene (C2Cl4), the study found a mean concentration in water of 0.10gL1 and a mean concentration in indoor air of 2.1gm3. Repeat part (c) for this species. (e) Comment on the relative significance of breathing and drinking for exposure to these toxic chemicals