Table 1

The number of measurements and distribution of TTHMs between three exposure categories and reference category.
Exposure categories
 No of samples
 Mean ± SD (μg/L)
 Minimum (μg/L)
 25 percentile (μg/L)
 Median (μg/L)
 75 percentile (μg/L)
 Maximum (μg/L)
Reference (TTHMs (0–4 μg/L)
 528
 3.64 ± 0.95
 .85
 3.50
 3.80
 4.06
 4.96
Low (TTHMs 5–9 μg/L)
 168
 5.57 ± 0.96
 5.00
 6.25
 7.15
 8.05
 9.50
Medium (TTHMs 10–19 μg/L)
 240
 16.48 ± 2.94
 10.68
 14.95
 15.57
 17.57
 19.53
High (TTHMs 20 ± μg/L)
 228
 23.24 ± 2.27
 20.35
 21.90
 22.70
 24.90
 32.65

Hwang et al. Environmental Health 2008 7:23   doi:10.1186/1476-069X-7-23