Tests to determine whether Waikato River water contains toxins have been delayed because the only laboratory in the country capable of the work has been deluged with samples for analysis.
By the time the tests to find out if an algal bloom in the river has released toxins are completed, thesamples will be a week old.
Environmental Science and Research's Wellington laboratory told Waikato's public health unit that results from its samples were unlikely to be ready until today.
Even then, scientists would be able to determine only whether the bloom was toxic early last week, rather than its present state.
Sampling since then would provide a conveyor belt of toxicity results, which health officials would use to decide whether warnings on the quality of the water needed to be upgraded or withdrawn.
The Hamilton City Council will start dosing the city's drinking water with a tonne of powdered activated carbon daily from Friday to neutralise any toxins and improve taste and odour.
