Fluoride can have a detrimental effect on a child's IQ and should be removed from drinking water, anti-fluoride activists said Thursday.

Members of the Fluoride Action Network and Citizens for a Safe Environment said they have found studies from China and other countries that prove fluoride exposure may inhibit the development of a child's brain.

An international group of scientists who study fluoride in drinking water appeared with members of the two advocacy groups at a Queen's Park press conference.

"Does fluoride cause problems? Absolutely," Paul Connet, director of the Fluoride Action Network, told reporters. "Fluoride lowers thyroid function, fluoride damages the bone and fluoride lowers IQ. All of these have been demonstrated in India and China."

However, a prominent Ontario dentist defends the presence of fluoride in drinking water, and refutes claims that it can cause a range of health problems in children.

Dr. Larry Levin appeared on CTV Newsnet on Thursday and dismissed concerns that fluoride is linked to health problems such as lower IQs in children.

Levin referred to a recent report posted on Health Canada's website that recommended reducing the amount of fluoride in drinking water but found no evidence to suggest a link between fluoride and an increased risk of cancer, developmental or reproductive problems or a lower IQ.

"They've brought together six top experts who have carefully looked at all of the details and they have come to a very clear result that there is not a link that would suggest fluoride is going to cause the problems that some people would suggest," Levin said.

The report, which was dated April 2008, recommends reducing the amount of fluoride, a chemical that prevents tooth decay, in drinking water.

The report says fluoride levels should be lowered to 0.7 parts per million from the current range of 0.8 to one ppm.

However, this recommendation is designed to lower the incidence rates of a stain that fluoride can leave on teeth.

The report also recommends that children up to age three use low-fluoride toothpaste, and says that fluoride levels in infant formula should be reduced.

Health Canada told CTV News last month that it accepts the recommendations, but would leave it up to the individual municipalities to implement them.

Levin said that children should be exposed to fluoride in drinking water to ward off dental problems later in life.

"The fluoride gets incorporated into the enamel of the tooth at the time that the tooth is forming, so this makes a stronger coating on the tooth which is more resistant to decay right from the very start," Levin said.

With a report from CTV medical specialist Avis Favaro and senior producer Elizabeth St. Philip