The news that come Nov. 5, San Diego County’s main water supplier will begin fluoridating the treated water it sends our way should have been greeted with cheers and bafflement. It is a big step forward for public health, and this should have happened long ago.

Instead, the Metropolitan Water District of Southern California’s decision has revived the bizarre, baseless allegations that fluoridation amounts to a systematic poisoning of the public. In a Sept. 16 Union-Tribune story, Jeff Green, the San Diego-based national director of the Citizens for Safe Drinking Water, contended fluoridated water raised the risk of lung and bladder cancer.

This isn’t just foolishness. Given fluoridation’s vast record as an easy, cheap way to improve dental health, Green is engaged in outrageous fear-mongering.

Yes, the use of fluoride to prevent tooth decay must be done carefully. Too much fluoride can stain the teeth of younger children. This is why the San Diego County Dental Society has advised local dentists to stop prescribing fluoride supplements to kids until tests of county water after the MWD’s Nov. 5 changeover show whether the supplements are still needed.

But there is simply no evidence linking fluoridated water and cancer among the hundreds of millions of people who have long used it. Green and a few renegade dentists may tout their own studies, yet does anyone seriously think the World Health Organization, the U.S. Centers for Disease Control and Prevention, the American Medical Association, the American Cancer Society and, of course, the American Dental Society would endorse fluoridation if it were carcinogenic?

When fluoridation first came into routine use a half-century ago, critics routinely described it as a communist plot. This led to hopes that as the Cold War faded, a more rational view would take hold.

Unfortunately, the very idea of someone putting something in our drinking water seems to inspire conspiratorial thinking. The old theory – the Soviets have figured out a way to poison us! – has given way to such new theories as the notion that fluoridation is really a way for big businesses to dispose of their toxic waste.

This is absurd. Why would any business undertake such an elaborate, reckless and lawsuit-inviting subterfuge to get rid of its toxics given the practical, inexpensive means of disposal? Fluoridation isn’t carcinogenic, but pondering it evidently can interfere with clear thinking.

So we hail the MWD’s decision and hope for more local fluoridation gains. The city of San Diego gets less MWD water than most county areas. County Supervisor Ron Roberts thinks an initiative-created state agency dedicated to helping children might be able to help the city come up with the estimated $3 million to $8 million to buy the equipment needed to fluoridate the rest of its water supply.

Roberts should pursue this possibility vigorously. It’s time San Diego surrendered its status as the largest U.S. city without fluoridation – no matter what the conspiracy theorists say.