Table 3.
Welders’ TWA breathing zone concentrations (μg m−3) of respirable particle size manganese (Mn) fractions measured at three heavy equipment plants.
| Plant | Parameter | TWA concentration | ||||||||
|---|---|---|---|---|---|---|---|---|---|---|
| Mn (Sol) | Mn (0, +2) | Mn (+3, +4) | Mn (Insol) | Mn (Sum) | ||||||
| A | n | 9 | 9 | 9 | 9 | 9 | ||||
| Minimum | 0.33a | 15 | 14 | 5.3 | 36 | |||||
| GM (GSD) | 1.3 (2.6) | 32 (1.9) | 37 (1.7) | 13 (2.0) | 85 (1.8) | |||||
| Maximum | 4.6 | 120 | 100 | 69 | 290 | |||||
| B | n | 10 | 10 | 10 | 10 | 10 | ||||
| Minimum | 2.1 | 28 | 37 | 10 | 79 | |||||
| GM (GSD) | 5.7 (1.9) | 70 (1.8) | 87 (1.6) | 35 (2.4) | 200 (1.8) | |||||
| Maximum | 15 | 140 | 170 | 230 | 530 | |||||
| C | n | 10 | 10 | 10 | 10 | 10 | ||||
| Minimum | 6.9 | 38 | 42 | 31 | 120 | |||||
| GM (GSD) | 9.7 (1.4) | 63 (1.5) | 60 (1.3) | 52 (1.9) | 190 (1.5) | |||||
| Maximum | 21 | 140 | 90 | 220 | 470 | |||||
| All | n | 29 | 29 | 29 | 29 | 29 | ||||
| Minimum | 0.33 | 15 | 14 | 5.3 | 36 | |||||
| GM (GSD) | 4.3 (2.9) | 53 (1.9) | 58 (1.7) | 29 (2.6) | 150 (1.9) | |||||
| Maximum | 21 | 140 | 170 | 230 | 530 | |||||
Sol Mn, manganese concentration dissolved in first sequential extraction solution: 0.01 molar ammonium acetate, room temperature (over 90 min); Mn 0, 2+, manganese concentration dissolved in second solution: 25% acetic acid, 75°C (over 90 min); Mn 3+, 4+, manganese concentration dissolved in third solution: 0.5% hydroxylamine-hydrochloride in 25% acetic acid, 75°C (over 90 min); Insol Mn, manganese concentration dissolved in fourth solutions: hydrochloric acid, 95°C (over 15 min) and nitric acid, 95°C (over 15 min); Sum Mn, addition of all four previous extraction manganese concentrations.
aData in this table reported with two significant figures.