After almost 40 years of providing fluoride to the shire's residents northern NSW's Ballina council is recommending that it scrap the service.

Since 1965 the council has offered fluoride in one form or another.

But new legislation now classifies fluoride as a poison.

Ballina's manager of water and sewerage, Phil Warner, says it is time stop the practice because the council is no longer authorised to hand out fluoride.

"The council has been providing fluoride to the community over the counter for many years now, but in tablet form and also in drop form," Mr Warner said.

"Basically fluoride is now considered a poisonous substance."

Residents in the small town of Forsayth, south of Georgetown, say their water supply is so bad it is making people sick.

Locals says the water has always been undrinkable but a $500,000 treatment plant installed last year was supposed to fix the problem.