The recommended time weighted average air concentration for occupational exposure to water soluble hexavalent chromium (Cr VI) is 0.05 mg · m−3. This concentration is based on an assumption that the individual is generally healthy and is exposed for 8 hours per day, 5 days per week, 50 weeks per year, over a working lifetime (that is from age 18 to 65 years). Assuming a body weight of 78 kg and inhalation rate of 15.2 m3 · d−1 over the working life of the individual, what is the lifetime (75 years) CDI?

the lifetime (75 years) CDI is 0.001393 mg/kg.day

Explanation:

Given that;

CA = Contaminant Concentration = 0.05 mg/m³

IR = Inhalation Rate = 15.2m³per day = 15.2 / 24 = 0.6333 m³/hr

ET = Exposure Time = 8 hour per day

ED = Exposure Duration = (65 - 18 years)  = 47

EF = Exposure Frequency = 5 day/week * 50 week/ year = 250 days/year

BW = Body Weight = 78 Kg

AT = Averaging Time = 75 years = (75 * 365 days) = 27375 days

Now to find the CDI (Chronic Daily Intake)' we say;

CDI = (CA×IR×ET×EF×ED) / ( BW×AT)

so we substitute;

CDI = (0.05 × 0.6333 × 8 ×250 × 47) / (78 × 27375)

CDI = 2976.51 / 2135250

CDI = 0.001393 mg/kg.day

therefore the lifetime (75 years) CDI is 0.001393 mg/kg.day

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