2. Calculate whether the following scenarios exceed any of the OSHA exposure lim

Question

2. Calculate whether the following scenarios exceed any of the OSHA exposure limits.

Determine the 8-hour TWA and identify the exposure limit in your answer.

a. 4 hours of 2 fibers/cc asbestos exposure and 4 hours of 0.5 f/cc asbestos exposure

b. 2 hours 50 ppm toluene exposure, 4 hours of 120 ppm toluene exposure, and 2 hours of 100 ppm toluene exposure

c. 8 hours of exposure to both 25 ppm methylene chloride and 50 ppm trichloroethylene

d. 8 hours of exposure to 40 ppm ethyl benzene, 40 ppm xylene, 40 ppm n-hexane, and 5 mg/m3 calcium sulfate

e. 1 hour of exposure to 50 ppm MEK, 5 hours of exposure to 200 MEK, 2 hours of exposure to 100 pm MEK

f. 8 hours exposure to both 2 ug/m3 cadmium and 35 ug/m3 le

Explanation / Answer

Solution:

Note: All OSHA PEL values are for 8 hour exposure (TWA)

a) Permissible Exposure Limit (PEL) for asbestos is 0.1 fiber per cubic centimeter of air as an eight-hour time-weighted average (TWA), with an excursion limit (EL) of 1.0 asbestos fibers per cubic centimeter over a 30-minute period. Let we calculate for the given condition,

4 hours of 2 f/cc -----> 0.5 f/cc per 1 hour --------> 0.25 f/cc per 30 minutes it does not meet EL and for 8 hours it is 4 f/cc becomes highly dangerous for human condition.

4 hours of 0.5 f/cc ------> 0.125 f/cc per 1 hour ------> 0.0625 f/cc per 30 minutes it meets the EL limit and safe in work exposure and at 8 hour exposure it reaches 1 f/cc is safe under the limit.

b) PEL for Toluene is 200 ppm for 8 hours as per OSHA,

2 hours of 50 ppm -----> 200 ppm for 8 hours it pars with safe limit and allowable limit.

4 hours of 120 ppm -------> 240 ppm for 8 hours it exceeds PEL but prolonged exposure is not advised as threshold limit is 260 ppm, so in unprevailed condition allowed under monitoring.

2 hours of 100 ppm --------> 400 ppm for 8 hours its highly dangerous and sudden death by respiration cessation is possible.

c) PEL for methylene chloride is 12.5 ppm and for trichloroethylene is 100 ppm

8 hours of 25 ppm methylene chloride is highly toxic and not permissible and 50 ppm of trichloroethylene is acceptable as it is under PEL limit of 100 ppm.

d) PEL limit ethylbenzene is 100 ppm, xylene is 100 ppm, n-hexane is 50 ppm and calcium sulfate is 5 mg/cu.m

all these components lies below the PEL so its acceptable in exposure condition.

e) PEL limit foe MEK is 200 ppm

1 hour of 50 ppm MEK ---------> 400 ppm for 8 hours is not permissble exceeds PEL

5 hours of 200 ppm MEK ----------------> 320 ppm for 8 hours is not permissible exceeds PEL

2 hours of 100 ppm MEK --------------> 400 ppm for 8 hours is not permissible exceeds PEL

f) PEL for Cadmium is 5 ug/cu.m so given exposure to 2 ug/cu.m is permissibe and in acceptable range

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