Table 4 Respiratory health of South African coal miners: Geometric means of dust levels by mine, year and zone (face, backbye and surface) (n = number of data points for that category of mine, zone and year)

Year / Surface / Backbye / Face
n / Geometric Mean (mg/m3) (Geometric SD) / n / Geometric Mean (mg/m3) (Geometric SD) / n / Geometric Mean (mg/m3) (Geometric SD)
MINE 1
1993 / 17 / 0.31 (3.18) / 39 / 0.52 (4.25) / 84 / 1.69 (4.29)
1994 / 27 / 0.16 (3.74) / 83 / 0.72 (3.85) / 110 / 2.28 (3.05)
1995 / 33 / 0.38 (3.74) / 105 / 1.38 (3.58) / 130 / 2.75 (2.73)
1996 / 37 / 0.22 (4.42) / 129 / 0.89 (4.51) / 99 / 2.60 (3.96)
1997 / 42 / 0.15 (4.62) / 141 / 1.01 (3.36) / 89 / 2.72 (3.01)
1998 / 37 / 0.08 (2.87) / 145 / 0.34 (3.63) / 80 / 1.40 (3.70)
1999 / 9 / 0.18 (1.67) / 29 / 0.25 (2.34) / 20 / 1.02 (5.38)
MINE 2
1996 / 25 / 0.5 (2.76) / 37 / 1.23 (3.53) / 46 / 2.32 (3.08)
1997 / 27 / 0.26 (1.99) / 55 / 1.48 (2.22) / 46 / 2.06 (2.34)
1998 / 59 / 0.44 (3.51) / 55 / 1.38 (2.96) / 49 / 2.42 (2.41)
1999 / 68 / 0.93 (2.43) / 57 / 2.07 (2.17) / 46 / 3.06 (1.57)
2000 / 43 / 0.74 (3.52) / 43 / 1.37 (3.32) / 38 / 2.96 (2.36)
MINE 3
1991 / 34 / 0.12 (4.95) / 51 / 0.20 (4.79) / 46 / 0.43 (3.98)
1992 / 55 / 0.25 (5.12) / 57 / 0.39 (3.93) / 45 / 1.03 (3.76)
1993 / 84 / 0.23 (5.74) / 85 / 0.50 (3.82) / 41 / 0.67 (5.74)
1994 / 58 / 0.32 (7.46) / 77 / 0.66 (4.32) / 31 / 1.79 (6.09)
1995 / 51 / 0.33 (5.10) / 86 / 0.51 (4.88) / 36 / 2.33 (5.11)
1996 / 81 / 0.26 (6.20) / 110 / 0.58 (5.28) / 74 / 1.69 (4.85)
1997 / 68 / 0.40 (5.09) / 149 / 0.54 (4.23) / 76 / 1.67 (5.21)
1998 / 12 / 0.11 (5.53) / 32 / 0.42 (5.21) / 16 / 0.81 (4.10)

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