About 130,000 homes in Cumbria are supplied by water containing added fluoride – and soon that number could be increased.

Health bosses in the county are considering introducing fluoride into more of the reservoirs providing our drinking water.

They have agreed to ask the region’s strategic health authority, NHS North West, to investigate how it could be done.

The health bosses hope fluoridated water will improve the dental health of Cumbrian children and adults alike, whose rates of tooth decay are higher than in most other parts of the country.

But campaigners protest that the fluoride could be dangerous – and say more studies need to be carried out to examine its long-term effects.

If the strategic health authority decides in favour of it, a consultation will take place inviting local people to put their views for or against.

Here we look at both sides of the argument:

YES: Eric Rooney, consultant in dental public health with NHS Cumbria

Children in Cumbria have some of the worst teeth in the country – and children from deprived backgrounds have the worst of all. Yet youngsters from the West Midlands have better than average dental health. And they have had fluoridated water for around 40 years.

This, says dentist Eric Rooney, is why adding fluoride to our water supplies could be beneficial.

Mr Rooney is consultant in dental public health with NHS Cumbria. He discovered how poor dental health in Cumbrian children was after examining the infant teeth of five-year-olds in the county.

Though these children will lose their infant teeth in the coming years, as their adult teeth emerge, Mr Rooney said that factors such as diet will not change much into their teens – so the infant teeth will give a good indication of how the adult teeth will eventually turn out.

“They have teeth that come below the national average,” he said. “Those from areas of social deprivation have the worst levels.

“But in the West Midlands, the teeth of children measured at the same age shows they have better dental health. The best available evidence suggests that water fluoridation does reduce tooth decay. The weight of scientific and medical opinion agrees.”

Providing more NHS dentists is not an answer to the county’s dental problems, Mr Rooney argued, since prevention is better than cure.

“If you end up with holes in your adult teeth, those holes will never go away again.

“A dentist can fill them, but they will eventually need filled again. That is why we need preventative strategies, rather than thinking that the solution is more dentists.”

And it is impossible to check that all children are being taught to brush their teeth twice a day and cut down on sweets and sugary drinks.

Lifestyles are difficult to change.

He said: “Diet and using fluoride toothpaste require a potential change of behaviour. But water fluoridation by its very nature is universal, so everyone gets its effects.”

And people from disadvantaged backgrounds would stand to benefit, as their rates of tooth decay are the worst.

“Part of this is about reducing inequalities, and levelling up the areas where people are more deprived,” Mr Rooney said.

Opponents of water fluoridation maintain that there are potential health risks, however. Dental fluorosis, in which teeth can appear mottled or discoloured, can be caused by water containing fluoride. Mr Rooney accepted this could be the case.

But he said: “With one part fluoride per million parts of water we would expect a small increase. But the effects would probably be a few white fleck marks on teeth.

“In some parts of the world there is a large concentration of fluoride naturally in the water, of six or seven or eight parts per million. It is only there that you get severe marking of teeth.

“We don’t have a massive glut of children in the West Midlands whose teeth are so horribly discoloured by dental fluorisis that they need cosmetic treatment.”

Some of the worst fears about fluoridated water were that it could cause bone or thyroid cancer. But Mr Rooney said the evidence showed these fears were unfounded.

“When York University reviewed research they found no link between fluoridated water and any cancers.

“For other serious negative effects there was insufficient evidence.”

Besides, he added, the people of the West Midlands have had fluoridated water since the 1960s.

“If there really was an issue about this then it would have affected a lot of people in the West Midlands and it would have come to light over the last 40 years. There would have been a pattern emerging over that period of time.

“There are beneficial effects and there is a risk associated with dental fluorosis.

“But there is no real evidence to support other negative claims about fluoride.”

NO: Dianne Standen, co-founder of Cumbrians Against Fluoridation

Dianne Standen’s daughter has had to spend thousands of pounds on cosmetic dentistry after developing mottled, discoloured teeth.

She has had to pay for veneers to cover the damage done by the condition called dental fluorosis.

And Ms Standen is convinced it is down to the fluoride added to the reservoirs supplying her home.

Yet discoloured teeth are only the visible evidence. Ms Standen, from Maryport, fears the added fluoride could also be causing damage inside the body which we cannot see.

She is co-founder of Cumbrians Against Fluoridation, a pressure group set up to have the fluoride removed from local water supplies – and to fight plans to add it elsewhere.

Currently two reservoirs in the county, Corn How and Ennerdale, have fluoride added to their waters. They supply homes in west Cumbria, stretching from Aspatria in the north down the coast to Ravenglass, and inland as far as Embleton.

Members of Cumbrians Against Fluoridation fear this fluoridated water could be to blame for joint and muscle pains, thyroid problems, and ailments as varied as vomiting, difficulty sleeping, nose bleeds, headaches and skin inflammations.

So even if it did improve teeth, Ms Standen says, it is doing more harm than good.

“My children both had several health problems which, when you look at the literature, could be related to fluoride,” said Ms Standen, 57.

“In the group we have heard of other people who developed problems when they moved into this area. When they moved out and stopped drinking the water, their problems cleared up.

“I suspect that in time we may find more evidence.”

These cases are not conclusive proof that fluoride in the water is harmful. Any number of factors can cause any number of illnesses.

But as Ms Standen points out, it was a long time before a link between cigarettes and cancer was proven.

Nor, she adds, is there any proof that fluoride isn’t to blame for them.

“There has been no long-term research about the effects,” she says. “If you are going to put something in our water, you need to be absolutely, 100 per cent sure that there are no hidden health issues – and they are not 100 per cent sure.

“It beggars belief that a body entrusted with improving your health is dogmatically promoting this.”

Ms Standen also believes fluoridation goes against the current philosophy in health.

“The language is all about patient choice and evidence-based medicine at the moment. But this seems to have slipped under the radar.”

Tiny amounts of fluoride occur naturally in water, and supporters of fluoridation say they want to adjust the levels to improve our teeth. But Ms Standen said this claim is misleading.

“Calcium fluoride occurs naturally, but what they are adding is hexafluorosilic acid, which is a very different substance.

“It is a by-product of fertiliser and also contains heavy metals and other contaminants. I don’t think anyone should be drinking a chemical cocktail.”

In any case, she pointed out that nutrition and dental hygiene could just as easily do the job as fluoride. Simply brushing your teeth regularly and limiting your intake of sugary food and drink will protect them.

“There are very few people who are incapable of cleaning their teeth and aren’t aware that it is important,” she said.

And she added that the children whose teeth are most at risk won’t benefit, as they get their fluids from sugary fizzy drinks – not from tap water.

Eight years ago, scientists at York University examined 30 different studies into fluoridation, but were unable to come down for or against it.

But while the jury’s out Dianne believes adding fluoride should be put on hold.