The number of Hanford downwinders who will have their cases heard in a long-anticipated federal trial April 25 has dropped from 12 to 7 as a judge decided four don't have strong enough claims and one voluntarily halted her claim.

Today, defendants in the case will make summary judgment arguments in Spokane, asking to have the remaining bellwether plaintiffs dismissed.

In 1991, the first claims were filed by people who lived downwind of Hanford when plutonium was being produced during World War II and the Cold War for the nation's nuclear weapons program. Radioactive releases, primarily iodine 131, drifted downwind to settle on crops and the grass where dairy cows grazed.

After years of legal maneuvers, appeals and a change of judges in the case, U.S. District Judge William Fremming Nielsen ordered that attorneys for the plaintiffs and the early Hanford contractors each pick six defendants to serve as bellwethers.

His hope is that by seeing what a jury would decide on a sampling of plaintiffs will help a settlement to be reached out of court on the estimated 2,500 plaintiffs in the suit who believe Hanford emissions damaged their health.

Nielsen has told downwinder attorneys that the scientific testimony offered by some of its medical experts does not appear to be strong enough to support the claims of four of the bellwethers.

All four bellwethers appeared to have relatively low doses of radiation. Radioactive iodine, which could have been consumed in contaminated milk or fresh produce, settles in the thyroid, where it can cause cancer or other disease.

One bellwether plaintiff who will not go to trial, Dorothy Workman, received four-tenths of a rad dose of radioactive iodine. In comparison, if a doctor prescribed radioactive iodine to perform a diagnostic thyroid scan, the dose might be 50 to 150 rad.

"It's clear to me that (plaintiff's expert witness) can't conclude that that exposure even comes close to a more-probable-than-not cause of the thyroid problems that she had," Nielsen said in a hearing earlier this year to consider scientific evidence.

Earlier, bellwether Karla Griffin volunteered to drop out of the case after realizing that other family members who were not exposed to Hanford radiation had also developed thyroid disease. In some cases, a family history of thyroid disease may indicate that the cause of the disease was primarily hereditary rather than the result of Hanford emissions.

The five plaintiffs who will not go to trial were all picked as bellwethers by defense attorneys.

"They picked the very weakest (claims) out of 2,500," said plaintiff attorney Tom Foulds. "Most of the clients of mine and of other attorneys have more than adequate dose to establish claims."

He estimated that at least 90 percent of the 2,500 plaintiffs easily have stronger claims than the four bellwether cases questioned by the judge.

"We are not giving up on anyone the judge will permit us to go forward on," Foulds said.

Defense attorneys have said that the claimants they picked were typical.

"They have a lot of weak claims," said defense attorney Kevin Van Wart. "It's plain they have shown no inclination to screen claims."

Despite the decision not to allow the four bellwether plaintiffs to go to trial, plaintiffs "still want to pursue junk claims," he said.

Today he and other defense attorneys will ask the judge to also dismiss the six bellwethers picked by the plaintiffs and the remaining defense plaintiff.

The remaining bellwether picked by the defense is Helen Walker, who defense attorneys said received about 5.5 rads of radiation after moving to Colfax when she was 26. She was diagnosed with thyroid nodules when she was 28.

That is less than the dose she would have received from normal background radiation and less than the dose that any study has observed an increased risk of thyroid nodules among people exposed to radiation as an adult, the defense is arguing.

The plaintiffs have made a stronger case that low doses of radiation could lead to cancer or thyroid nodules than some other thyroid diseases, such as hypothyroidism, sometimes called an underactive thyroid.