More than three-quarters of the estimated 77,000 injuries that occur each year when people come in contact with moving power mower blades could be eliminated if the Consumer Product Safety Commission approves a new safety standard, the commission staff maintains.

A final mandatory standard was proposed by the staff this week. The controversial measure would require all models of new power mowers to pass two tests:

When a facsimile of a human foot is inserted under the rear of a mower (60 degrees on each side of the center line of each mower), the foot must not be able to reach the blade of the mower.

Blade motion must stop within three seconds of release of the power control switch -- which must be on the handle of the mower and which must turn off automatically when not held by hand.

The latter restriction would make it virtually impossible for someone using a mower to take his or her hand off the handle of the mower and down to the blade before the blade stops turning.

The proposed mandatory standard for power lawn mowers has been on the drawing board at the CPSC for five years -- since the agency was founded.

In 1973, the Outdoor Power Equipment Institute petitioned the commission to develop a mandatory safety standard, and at the same time proposed its own voluntary standard as a mandatory rule for the industry.

But the commission decided that the proposed standard was not good enough, and directed its own staff to come up with a better one.

Almost a year later, the Consumer Reports-publishing Consumers Union, which was involved in helping set the government standard, put together a recommended mandatory rule.

After three years of review, the CPSC staff published its own version of a proposed rule on May 5, 1977. The version's 14 sections dealt with a range of problems -- including delayed blade contact, thrown objects and fuel and ignition hazards.

After an industry uproar, the commission rejected the rule and decided to narrow its scope, eliminating all issues except blade contact.

Because most of the power mower-related injuries are due to blade contact -- with about 30,000 of the 77,000 injuries that occur each year requiring emergency room treatment -- the scope of the rule was limited to get some sort of rule finally in effect.

According to CPSC Program Director William Kitzes, most of the injuries occur when the mower operators try to clear the mower discharge chutes, adjust their machines or attempt other actions around them.

Nearly 10,000 of the blade-contact injuries involve amputations of fingers or toes. Kitzes and his staff estimate that the annual cost of these injuries is $283 million.

Kitzes said the technology needed for the blade stop-time rule "has been available for over 10 years. There is even one manufacturer who has been making mowers that stop blades in less than one second."

Kitzes said the entire standard proposal, which could be accepted by the commission next Thursday, "will raise the price of the average mower $35."

The industry has been fighting the commission over the blade stop-time regulation, maintaining that it is unnecessary and too costly. Two months ago, the industry embarked on a six-month plan to develop an alternative method of compliance.

Privately, industry sources have also expressed concern over the issue of product liability. They say the industry is worried that if it starts producing mowers with blades that stop within three seconds -- using old technology -- those injured by mowers will sue and claim that the injuries they suffered were avoidable because the technology was available to include fast-stop features.