On Feb. 1 - the start of National Children's Dental Health Month - San Jose solidified its place atop a list notorious among those battling sugary treats and cavities: it became the largest city in the country that doesn't add fluoride to its drinking water.

That day, San Diego began pumping the compound into its water supply, 46 years after New York's system went online, 12 years after Los Angeles and almost 60 years after San Francisco.

To many health professionals, the situation is an affront in a place hailed as the cradle of high-tech innovation.

"Fluoridation has been done across the country since the 1940s," said Fred Ferrer, chief executive of the Health Trust, a nonprofit public health foundation that serves Santa Clara and San Benito counties. "We're really behind the times - and that's really unlike Santa Clara County."

Next month, Ferrer and other fluoridation advocates plan to take the issue to Santa Clara Valley Water District, a water wholesaler whose retail customers serve about 1.8 million people. In a 2010 letter to the water district, county supervisor Liz Kniss said recent polls showed that two-thirds of county residents support fluoridation, with only 13 percent opposed.

"The scientific evidence is overwhelming," Kniss wrote. "The need is great. It's time for Silicon Valley to join Los Angeles, San Diego, San Francisco and virtually every other major metropolitan area in the United States as a community that fluoridates its water."

Some remain opposed

Even with the expected cooperation of the water agency, the issue in San Jose is far from settled. A 1995 California state law requires public water agencies with more than 10,000 connections to fluoridate their water - but they must find outside funding for the infrastructure. Despite much evidence showing fluoride is safe and effective in fighting dental decay, a vocal group called the Fluoride Action Network contends the substance may harm kidney function and erode proteins in bones.

"I swim 150 miles a year," said Maureen Jones, 68, a Fluoride Action Network representative in San Jose. If the city succeeds in adding fluoride to its water, "I won't drink it and I won't bathe in it. Just the thought of it makes me squirm."

The American Dental Association says water fluoridation reduces tooth decay 20 to 40 percent, even with regular exposure to fluoride in toothpaste, rinses and food. Every $1 spent on fluoridation, the group says, saves $38 in dental procedures.

Small amounts of fluoride prevent tooth decay in two ways. When it is ingested, the compound is incorporated into teeth, helping to strengthen them. On the surface, fluoride helps block the bacteria that can eat away at tooth enamel.

After decades of research on cities with elevated, naturally occurring levels of fluoride, a half-dozen cities in the United States and Canada started adding fluoride to their water in the mid-1940s.

Fluoride in most cities

Sixty years later, more than 72 percent of the U.S. population uses fluoridated water and 42 of the 50 largest cities in the country have installed fluoridation systems or possess water with high enough levels of the compound, according to the Centers for Disease Control and Prevention.

While San Francisco and Oakland fluoridated most or all of their water decades ago, some cities adopted the policy only after the 1995 law. Others, such as Santa Cruz and Watsonville, have been the site of vigorous fights over the issue.

In Santa Clara County, the fluoridation question also hinges on money and logistics. The water district pulls its supply from varied sources and serves dozens of smaller utilities and cities. Some of those - and the Evergreen section of San Jose - moved to fluoridate their water years ago, in part, because customers approved it and they received water from different sources.

Because the Santa Clara Valley Water District itself is a water wholesaler, technically it doesn't have the 10,000 connections that require fluoridation. What's more, the district and other water providers in the county draw significant portions of their source water from wells - meaning that each may have to be outfitted with fluoridation equipment. Such a broad-scale project could cost tens of millions of dollars. For its project, San Diego accepted a $4 million grant from the First 5 Foundation of San Diego County.

An issue of funding

Bruce Cabral, water quality manager for the Santa Clara utility, said his agency is a willing partner on fluoridation.

"If our retailers request us to fluoridate, we'll go down that path with them," Cabral said. "The problem so far is, none of our retailers have ever been approached with money."