HOW do you tell the difference between a scare story and a cover up?

The realm of health has proved fertile ground for conspiracy theorists who over the years have claimed everything from the artificial sweetener aspartame causing multiple sclerosis to the MMR vaccine causing autism - a stubborn myth that seems to have been given a whole new lease of life courtesy of social media.

A dearth of scientific and statistical literacy amongst the general public and (it pains me to say) the media, helps.

Read more: Headteacher says 'blue water' school is safe and has not caused cancer

Take for example, the difference between relative risk and absolute risk. A 2012 study found that children who have several CT scans are "three times more likely to develop leukaemia or brain cancer as an adult".

But this is the relative risk compared to children who were never scanned, and - because childhood cancers are so rare within the population anyway - in absolute terms it only translated into one additional case of adult brain cancer and one of leukaemia for every 10,000 children scanned.

Then there is the difference between causation and correlation. For example, a 1982 study famously concluded that drinking coffee was linked to pancreatic cancer, but the authors had failed to control for the real cause (smoking). A lot of smokers also drink coffee - the latter 'link' was merely coincidence. Or 'correlation'.

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Which brings me to what may (or may not) be Scotland's latest health scare story: the 'blue water' school.

Buchanan High in Coatbridge is at the centre of an alleged bladder cancer cluster blamed on toxins emanating from the ground beneath it, formerly the site of an industrial and domestic landfill site.

Firstly, it is worth noting that the blue water itself is probably a red herring. Copper - the cause of the blue tinge discolouring some of the school's tap water - can cause stomach upsets, but it is not a carcinogen.

Arsenic, which does increase a person's risk of bladder cancer, has reportedly been detected in unusually high levels among some pupils.

However, arsenic occurs in two forms: inorganic and organic. The former is toxic and long-term exposure, for example through contaminated drinking water, can lead to skin cancer.

Organic arsenic meanwhile is harmless and occurs naturally in rice, shellfish and fruit juices.

The council says there have been "no cases with the toxic form".

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Men, older people, smokers and diabetics are also at higher statistical risk of bladder cancer. If that description fits all four individuals with bladder cancer, the chance that something is genuinely amiss would weaken - and strengthen if it is the opposite.

Passions inevitably run high in cases like this, and it doesn't help that genuine cover ups do happen. The Infected Blood Inquiry, currently ongoing, is testament to that.

In the end, the difference is evidence.

Only by sharing it, fairly and openly, can the 'blue water' school fears truly be resolved.