GUERNSEY Water regularly tests for more than 130 chemicals in the island’s drinking supply.

Some have been known about for years, but the first UK guidelines on PFOS, the firefighting foam, were issued just two years ago.

The toxicity of PFOS, the way it is absorbed into the soil and its point blank refusal to break down make it a particularly nasty pollutant.

Once released into the environment it accumulates in organisms and works its way up the food chain, where it can become a serious problem.

For those reasons, the Scrutiny Committee is rightly keen to ensure that everything possible has been done to contain the pollution and to mitigate its effects. In that way, the island can minimise dangers stored up for the future.

That is not to say that officers at Public Services, Guernsey Water, HSSD or Environmental Health have not been fully up to the mark, only to recognise the high stakes and the need to allay any public fears about the quality of drinking water.

States experts have been adamant – convincingly so – that the PFOS found in streams, boreholes and, ultimately, St Saviour’s reservoir represents no immediate threat to islanders.

And speculation at this stage from one deputy that high cancer levels in the island might be attributable to the foam is certainly premature.

Scrutiny’s investigation will hopefully put to bed wild conjecture. If an underground toxic timebomb is ticking away and steadily polluting our environment it is best to know now. But the debate needs to be at a reasoned scientific level, unpolluted by hysteria and assumption.

If there are questions to be asked and recommendations to come out of Scrutiny’s report they will almost certainly come out of how speedily departments reacted to reports that the PFOS in firefighting foam was an issue of high concern.

It was certainly known about by the time of the Buncefield fire in 2005 – the scale of the oil depot fire meant that the old PFOS-contaminated foam was reluctantly pulled out of storage – but there were earlier reports.

It will be Scrutiny’s task to judge whether lessons are there to be learned.