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Table 1 Results reported in good quality studies

From: The association between drinking water turbidity and gastrointestinal illness: a systematic review

Study

Effect measure (lag in brackets)

Over what unit of turbidity

Positive Lags (days)

Measure of population impact

Schwartz, US (1997) [17]

Between 5–31% increase in A&E visits and admissions at various lags.

0.04 NTU

1, 4, 6–7†, 7–9†, 8, 10, 13

None stated.

Morris, US (1998) [23]

TERS plots suggest weak correlations; no statistical significance testing.

N/A

None.

N/A

Schwartz, US (2000) [24]

Between 5–15% (9–11) increase in admissions; 4–6 lag also significant for one plant; effect greater in those over 75 years (p < 0.0001)

0.035 NTU

4–6†, 9, 10, 11, 9–11†

None stated.

Aramini, Canada (2000) [20]

Relative rates and odds ratios between 1.2 and 2.0 for different watershed/age combinations.

*

3–6†, 6–9†, 12–16†, 21–29†

<2% GI illness estimated to be attributable to drinking water

Lim, Canada (2002) [25]

No significant measures of effect reported.

N/A

None.

N/A

Gilbert, Canada (2006) [22]

Relative rates of 1.33 (11), 1.53 (15) and 1.76 (17).

*

11, 15, 17

None stated.

  1. *A relative rate and odds ratio of, for example, 1.2 represents a 20% increase in the likelihood of gastroenteritis associated with a particular level of turbidity at a particular lag, compared to the predicted probability associated with the mean turbidity effect for that particular lag, after adjusting for other parameters in the model
  2. †combined