WASHINGTON - Ending years of wait, the government agreed Thursday to provide millions of dollars in disability benefits to as many as 2,100 U.S. Air Force reservists and active-duty forces exposed to Agent Orange residue on airplanes used in the Vietnam War.

It is the first time the Department of Veteran Affairs, a government-run military veteran benefit system, has established a special category of Agent Orange exposure for troops who weren't on the ground or didn't serve on inland waterways in Vietnam.

The new rule, approved by the White House, takes effect Friday. The expected cost over 10 years is $47.5 million, with separate health care coverage adding to the price tag.

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"Opening up eligibility for this deserving group of Air Force veterans and reservists is the right thing to do," Bob McDonald, Secretary of the Department of Veteran Affairs, known as the VA, said in a statement.

The new regulation covers an expanded group of military personnel who flew or worked on Fairchild C-123 aircraft in the U.S. from 1969 to 1986 and were believed to have been exposed to Agent Orange residue. The planes had been used to spray millions of gallons of the chemical herbicide during the Vietnam War.

Still, citing weaker scientific evidence, the VA said it will not cover roughly 200,000 "Blue Water" veterans who say they were exposed to Agent Orange while serving aboard deep-water naval vessels off Vietnam's coast.

A recent study by a top U.S. research institute concluded that some C-123 reservists stationed in Ohio, Pennsylvania and Massachusetts had been exposed to Agent Orange residues in the planes and suffered higher risks of health problems as a result.

Undertaking a review of military records, the VA said it subsequently determined that pilots, mechanics and medical personnel who served at seven other locations in the U.S. and abroad also were potentially affected - Florida, Virginia, and Arizona, as well as Taiwan, Panama, South Korea and the Philippines.

Those affected individuals under the new rule will now be eligible to receive disability aid including survivor benefits and medical care. The veterans must show they worked on a contaminated plane and later developed any of 14 medical conditions such as prostate cancer, diabetes and leukemia that the VA has determined to be connected to Agent Orange.

Veterans' groups expressed tempered relief and hope that the government was now willing to acknowledge a wider range of toxic health risks undertaken by military personnel, such as Gulf War neurotoxins and burn pits in Iraq and Afghanistan.