Microbial water quality monitoring collects information on levels of faecal contamination over time.
Microbial assessment category
The microbial assessment category (MAC) is determined from the 95th percentile of a dataset of at least 100 enterococci data points. The four categories (A to D) relate to levels of risk of illness determined from key epidemiological studies. The National Health and Medical Research Council recommend MAC be calculated from a rolling five year dataset, with at least 20 samples collected each year during the swimming season.
95th %ile enterococci (cfu/100ml)
Basis of derivation
| A|| <41||No illness seen in most epidermiological studies|
| B|| 41-200|
Upper threshold is above the threshold of illness transmission reported in most studies
| C|| 201-500||Represents a substantial elevation in the probability of adverse health outcomes|
| D|| >500||Above this level there may be a significant risk of high levels of illness transmission|
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Page last updated: 15 February 2013