Assessing spatial fluctuations, temporal variability, and measurement error in estimated levels of disinfection by-products in tap water: implications for exposure assessment

Table 4

Sources of variation trihalomethane levels in tap water due to inter- and intra-household differences and measurement error

	Inter-household variation ( $\text{[math]}$ )	% of total variation*	Intra-household variation ( $\text{[math]}$ )	% of total variation^*	Sampling and analytical error ( $\text{[math]}$ )	% of total variation*
Data source: exposure assessment study, July–September 1994, n = 111 measurements.
*Estimated total variation: $\text{[math]}$ ; percentages may not add up due to rounding.
Total trihalomethanes	0.077	58	0.041	31	0.013	10
Chloroform	0.090	52	0.067	39	0.017	10
Bromodichloromethane	0.026	82	0.0002	1	0.006	18
Dibromochloromethane	0.021	37	0.025	45	0.010	18