Guidelines for recreational waters
National Health and Medical Research Council (NHMRC 2008) Guidelines for Managing Risks in Recreational Waters provide guidance for assessing recreational water quality.
For chemicals, the guidelines suggest a screening approach where a substance occurring in recreational waters, at a concentration that exceeds 10 times the drinking water guideline, warrants further investigation.
The drinking water guidelines are based on someone drinking 2 L of water every day over their life. As the drinking water guidelines are designed for people who actually ingest the water (by drinking it) a factor of 10 is applied to account for the lower exposure that typically occurs from swimming in it, as swimmers are more likely to ingest small amounts accidentally. It would be very unusual for a swimmer to ingest 2L of seawater every day.
Occasional exceedances of the investigation level may not necessarily pose a health concern however repeated exceedences within a short period will be a trigger for notifying DHS. Levels above those considered safe for short-term exposure will also be a trigger to notify DHS.
Refer to information on enterococci and algae for details of guidelines applying to these parameters.