Washington’s largest dental insurer will give Pierce County $420,000 to help pay for fluoridating its drinking water.

The grant is the biggest ever awarded by the Washington Dental Service Foundation.

The Tacoma-Pierce County Board of Health voted earlier this month to require fluoridation of all county water systems serving more than 5,000 people.

The mandate affects about 240,000 residents in Lakewood, Puyallup, Bonney Lake, Sumner, Milton, Edgewood, Parkland and Spanaway.

The health department estimates the initial cost to buy and install fluoridation equipment will be about $1.5 million. The health department will match the foundation’s grant, for a total of $840,000, said agency director Federico Cruz-Uribe. Water districts must pay the difference.

“This is a very reasonable start for the districts,” he said. “If they can get at least half their start-up costs covered, that’s pretty nice.”

Most of the water districts opposed the fluoridation rule, arguing that residents should be able to vote on the question.

The districts also believe the county’s cost estimates are low, and that the total price will exceed $2.5 million, said Randy Black, manager of the Lakewood Water District and president of the regional water association.

“I’m a little concerned because the (grant) is not a significant amount of money to help utilities,” Black said. “We’re hoping they can find other resources.”

Cruz-Uribe said the health department will apply next year for another grant from the foundation.

The districts have until Jan. 1, 2004, to install fluoridation equipment.

The health department will present an implementation plan to the board in June, detailing which districts will be fluoridated first and how the others will be phased in.

Pierce County’s fluoridation program is the most ambitious in Washington in recent years, said Sean Pickard, spokesman for the Dental Services Foundation. That’s why the organization decided to make the grant, he said.

Fluoridation is particularly beneficial for low-income families that lack dental insurance and don’t have access to regular dental care, Pickard said.

“It benefits our subscribers, but it also benefits the community as a whole,” he said.

Fluoridation won’t be required in Gig Harbor, Orting or Buckley, because the water districts have fewer than 5,000 customers, said Steve Marek of the health department.

However, once those districts pass the trigger number the rule will apply, he said.

Drinking water in Tacoma, University Place, Fircrest and at the local military bases has been fluoridated for more than 10 years.