Question

1. A worker was exposed over his shift to trichloroethylene. Four samples were measured during the 8-hour workday. They are:
   
   1. 8:00 – 9:30                            17.5 mg/m³
   2. 9:30-11:30                             15.7 mg/m³
   3. 12:00 - 1:30                           18.5 mg/m³
   4. 2:30 - 4:30                            20.5 mg/m³

What is the PEL for this compound and was it exceeded?

2. Given the following exposures to individual contaminants and their respective PELs, what is the combined exposure if the contaminants are considered additive?

            Contaminant             Exposure (mg/m³)                PEL (mg/m³)

                        X                                 150                                   500

                        Y                                 225                                   500

                        Z                                  175                                  500

Is the PEL for the mixture exceeded?

Answer 1

For the determination of PEL, we use the formula

E= (C1T1 + C2T2 + C3T3.....CnTn)/8

Where, E is equivalent exposure

C is concentration

T is the particular time period

Hence, the PEL of the compound is

E= (17.5*1.5 + 15.7*2 +18.5*1.5 + 20.5*2)/8

= (26.25 + 31.4 + 27.75 + 41)/8

= (126.4)/8

= 15.8