SACRAMENTO - In a move designed to reduce pollution in neighborhoods, the Air Resources Board (ARB) has approved standards that will virtually eliminate potentially cancer-causing dioxin emissions from incinerators used by hospitals, regional medical waste disposal facilities and other health care operations.

The ARB limits require dioxin emissions to be reduced by 99 percent, by upgrading pollution control equipment on large incinerators, including regional facilities with already dispose of 70 percent of the 12,000 tons of infectious medical waste generated each year.

The rules also require more effective operation of many small incinerators, many of which are expected to close as a result.

Besides reducing dioxin, a highly potent compound that the ARB identified as cancer-causing in 1986, the measure is expected to reduce exposure to other toxins such as benzene, cadmium, polycyclic aromatic hydrocarbons (PAH) and hydrochloric acid.

The new limits will affect about 146 incinerators, most of which are operated in residential areas, used to burn infectious medical waste, such as bandages, surgical instruments and pathological tissue.

Only about 20 percent of the state's hospitals continue to operate their own incinerators. The remainder either sterilize the waste, allowing it to be disposed of in landfills, or ship more efficient regional incinerators. The new ARB rules are expected accelerate that trend, since as many as 129 of those incinerators still operating are expected be shut down.

The ARB-approved limits require small incinerators continue in use only after personnel are trained operate them properly insure more thorough and complete burning of the waste, which is the most reliable method of preventing dioxin formation.

Under the new ARB guidelines, incinerators must operate at temperatures at least 1800 degrees F and the waste must come in contact with that high temperature for a minimum of one full second.

Eleven of the state's largest incinerators, including four regional facilities, are expected add scrubbers and baghouses their existing pollution control equipment in order meet the new standards. One large incinerator, operated by Stanford University Hospital, already complies with the new limits.

  In addition, while five relatively small regional incinerators in Southern California are expected close, a new facility in Susanville is expected begin operation soon which would double the state's capacity for burning medical waste.

At least two large, regional sterilizing facilities, one each in Northern and Southern California, also are in the planning stages, accommodate the expected upsurge in demand.

The cost of the new rules is expected be slight, adding only $0.36 $0.43 the $800 daily cost per bed for most hospital operations.

Medical waste incinerators were targeted for regulation because most of those still in operation are small, not equipped with pollution controls that are normally required on other types of incinerators, such as those that dispose of municipal waste, and are operated by untrained personnel. The result is poor or incomplete combustion, which promotes the formation of dioxin.

Also, most of these small incinerators are located in residential areas, where their emissions pose potential health threats for many people.

Adding the health problem they cause is the type of waste that they burn. Unlike specially designed regional facilities that burn medical waste exclusively, many incinerators operated by hospitals also burn non-infectious garbage that normally would be disposed of in well controlled municipal burners. ARB research shows that 70 95 percent of the waste burned by small hospitals is regular garbage.

 In approving the measure at an ARB hearing in Sacramento, Jananne Sharpless, Board chairwoman, noted, "It is ironic that backyard incinerators have been banned since the early 1950s, yet the incinerators used by 20 percent of the state's hospitals still burn more garbage than medical waste while being exempted from many routine pollution controls.

"These new standards will insure that public exposure a significant cancer-causing pollutant is virtually eliminated and that medical waste will only be burned in well-designed facilities with up--date air pollution controls.

"I hope that it will also encourage hospitals reduce the amount of waste they generate by using reusable items where it is possible and separate their garbage recycle as much as possible."

The new rules, approved during the Board's July hearings late last week, will be forwarded local air pollution control districts, where they will become effective by early next year.

At least 10 other states have used ARB testing results adopt similar standards for medical waste incinerators and other states and the EPA are also considering dioxin limits on these facilities.

States expressing the greatest interest are Arizona, Florida, Nevada and Washington.