Evaluating Employee Exposures to Methyl n-Amyl Ketone during a Painting Operation

 

Evaluating Employee Exposures to Methyl n-Amyl Ketone during a Painting Operation
Introduction
Employee safety is of utmost importance in any workplace. Exposure to hazardous substances such as methyl n-amyl ketone (MAK) during a painting operation can pose significant health risks. In this case study, we will evaluate employees’ exposures to MAK and compare the results to the Occupational Safety and Health Administration (OSHA) permissible exposure limit (PEL) and the American Conference of Governmental Industrial Hygienists (ACGIH) threshold limit value (TLV) for MAK.

Sampling Method
To evaluate employee exposures to MAK, we chose to use the NIOSH Method 2553 for sampling. This method provides accurate measurements of MAK concentrations in the air. The full details of this method can be found in the NIOSH Manual of Analytical Methods (4th ed.) [^1].

Sample Volumes
The pre-sampling and post-sampling pump calibrations were both 0.05 L/min. The sampling duration for Sample 1 was 430 minutes, and for Sample 2, it was 440 minutes. We need to calculate the sample volumes for each of the samples.

Sample 1: Sample volume = Pump calibration × Sampling duration = 0.05 L/min × 430 min = 21.5 L

Sample 2: Sample volume = Pump calibration × Sampling duration = 0.05 L/min × 440 min = 22 L

Concentrations in µg/L and mg/m³
Given the amounts of MAK in the front and back sections of each sample, we can calculate the concentrations of the two personal samples in µg/L and mg/m³.

Sample 1: Front section concentration = Amount of MAK in front section / Sample volume = 5000 µg / 21.5 L ≈ 232.56 µg/L ≈ 0.23256 mg/m³

Back section concentration = Amount of MAK in back section / Sample volume = 200 µg / 21.5 L ≈ 9.30 µg/L ≈ 0.0093 mg/m³

Sample 2: Front section concentration = Amount of MAK in front section / Sample volume = 4000 µg / 22 L ≈ 181.82 µg/L ≈ 0.18182 mg/m³

Back section concentration = Amount of MAK in back section / Sample volume = 50 µg / 22 L ≈ 2.27 µg/L ≈ 0.00227 mg/m³

Conversion to ppm
To compare the results to the OSHA PEL and the ACGIH TLV, we need to convert the concentrations from mg/m³ to ppm using the molecular weight of methyl n-amyl ketone (114.2 g/mol) and the ideal gas constant (24.45).

Sample 1: Front section concentration in ppm = (Front section concentration in mg/m³ × 24.45) / Molecular weight of MAK = (0.23256 mg/m³ × 24.45) / 114.2 ≈ 0.0498 ppm

Back section concentration in ppm = (Back section concentration in mg/m³ × 24.45) / Molecular weight of MAK = (0.0093 mg/m³ × 24.45) / 114.2 ≈ 0.00199 ppm

Sample 2: Front section concentration in ppm = (Front section concentration in mg/m³ × 24.45) / Molecular weight of MAK = (0.18182 mg/m³ × 24.45) / 114.2 ≈ 0.039 ppm

Back section concentration in ppm = (Back section concentration in mg/m³ × 24.45) / Molecular weight of MAK = (0.00227 mg/m³ × 24.45) / 114.2 ≈ 0.000484 ppm

Comparison to OSHA PEL and ACGIH TLV
According to OSHA’s Table Z-1, the 8-hour TWA PEL for methyl n-amyl ketone is set at 100 ppm. Comparing the results of our sampling, which range from 0.000484 ppm to 0.0498 ppm, it is evident that all concentrations are significantly below the OSHA PEL.

The ACGIH TLV for methyl n-amyl ketone is set at 50 ppm as an 8-hour TWA exposure. Comparing our results, it is clear that all concentrations are also well below the ACGIH TLV.

Choice of Comparison – OSHA PEL or ACGIH TLV
In this case, since both the OSHA PEL and the ACGIH TLV are significantly higher than the concentrations we obtained from our sampling, it is reasonable to conclude that employee exposures to methyl n-amyl ketone during the painting operation are well below both regulatory limits.

However, it is important to note that the ACGIH TLV is generally considered more stringent than OSHA PELs, as