Although it will not have any immediate effect on state and federal regulations, voters in lumber-rich Mendocino County have become the first in the nation to say officially they do not want herbicides sprayed on their forests from airplanes.

According to unofficial returns Tuesday, an initiative banning aerial spraying of phenoxy herbicides, chemicals containing the deadly substance dioxin, was approved 8,644 to 4,980.

The California attorney general's office has said the initiative has no effect because state and federal law supersedes local law, but county agricultural commissioner Ted Ericksen said he would obey the will of the voters.

The poisons are used to manage growth of forests and encourage production of redwoods and Douglas firs. The chemicals were used in Agent Orange, the Vietnam war defoliant, which opponents have blamed for ills ranging from loss of memory to birth defects.

But in Washington a group of scientists has concluded that one of the components of Agent Orange, the herbicide 2,4,5-T, now under temporary federal ban, has not been shown to cause cancer or miscarriages in humans.

The scientists added that much information on the herbicide is preliminary and that it is too early to say definitely there is no human risk.