20th June 2006, FAYETTEVILLE: An expert witness’ calculations of inhaled arsenic exposure in Prairie Grove won’t be allowed at trial, a judge ruled Monday.
Several lawsuits allege that spreading chicken litter caused cancer and other health problems in Prairie Grove.
Rod O’Connor used dust samples from heating and cooling system filters and applied a mathematical formula to calculate arsenic exposure among residents of the west Washington County town.
“The formula that he uses, this court has no faith in the validity of those numbers,” Washington County Circuit Judge Kim Smith said.
The judge said there were problems with O’Connor’s calculations because the scientific community has not generally accepted the methodology and reasoning he used. It has also not been peer reviewed, Smith said. He agreed with defense attorneys that O’Connor appears to have pulled some numbers “out of the air.”
O’Connor, a chemist and retired professor of environmental studies at Baylor University, is the plaintiff’s star witness in the case. He’s expected to testify that the poultry feed additive Roxarsone turns into a toxic form of arsenic as it degrades in chicken litter. The arsenic is then transported through the air to area homes after the litter is spread on fields as fertilizer.
O’Connor claims his sampling of dust from houses and schools in Prairie Grove shows an arsenic “fingerprint” that matches that of chicken litter.
Smith also threw out O’Connor’s calculations of arsenic exposure at Prairie Grove schools. The judge said O’Connor used dust samples from nine homes in the area rather than sampling the school buildings themselves to calculate exposure rates. Smith said the method used “grossly misleads the jury.”
During previous hearings, O’Connor implied the schools had conspired to clean up filters. He did not say why he thought school officials would do that.
Defense attorneys have maintained that dust samples taken from the Prairie Grove schools didn’t show arsenic, so samples taken from houses near the schools were substituted instead. O’Connor supposedly found that arsenic exposure levels at the schools were higher than any other place in Prairie Grove.
Smith also ruled that other expert witnesses can testify but cannot use the O’Connor data. The opinions of two medical doctors, James Dalhgren and Michael Wolfson, who both specialize in internal medicine will be allowed. Both are expected to say arsenic is responsible for increased cases of cancer and other health problems in Prairie Grove.
O’Connor will also be allowed to testify about other research he did in Prairie Grove and his findings.
The court has a gate-keeping role when it comes to expert witnesses. Experts are allowed to testify if the judge feels they have knowledge or expertise that will help him or the jury better understand the issues in a case. The court must determine whether the experts’ reasoning and methodology are valid and will not mislead jurors.
Smith is expected to rule on several pending motions for summary judgment today that, if approved, could result in the lawsuit being dismissed.
Lawyers for families suing the chicken industry said during earlier hearings that O’Connor’s findings show vividly what is happening in Prairie Grove because 30 of 31 homes tested showed at least traces of Roxarsone. The only source of Roxarsone is chicken feed, they contend.
The defendants maintain there’s no evidence of causation, that the arsenic exposure levels as calculated by the proposed experts in the case are so low they couldn’t have caused the cancers and other problems complained of by the plaintiffs.
Trial in the first of several “toxic tort” lawsuits over the spreading of chicken litter is currently set for Sept. 5 before Smith.
Members of about 50 families in the Prairie Grove area say they’re convinced there is a link between health problems in the community and substances found in chicken litter, particularly Roxarsone. They sued area poultry companies more than two years ago. Taken together, the various lawsuits include about 100 plaintiffs.
The companies sued include Alpharma, Alpharma Animal Health, Cal-Maine Farms, Cargill, George’s, Peterson, Simmons and Tyson Foods.