This story originally appeared on StateImpact Pennsylvania.
The Pennsylvania Department of Health has determined that there is no cancer cluster in a Washington County school district. The agency conducted the study after several cases of Ewing sarcoma, a rare bone cancer, were reported there.
The department looked at statistics from the Pennsylvania Cancer Registry dating to 1985. In addition to Ewing sarcoma, the agency looked at other types of cancer rates: liver, brain, bone, lung, and breast cancers. It compared cancer rates in Washington County and Canon-McMillan School District against statewide rates.
In a report released Tuesday, the state concluded that rates of Ewing sarcoma weren’t “consistently or statistically significantly higher than expected” in either Washington County or the school district.
The study did find that between 2005 and 2017, rates of Ewing sarcoma were three times higher than expected in the school district. The rare tumor mainly affects young people and can be fatal.
The authors said the number of cases was so small — just three instances of Ewing sarcoma in the district over those years — that the higher-than-expected rates weren’t “statistically significant.”
Only about 200 cases of the tumor are reported in the U.S. each year.
Jian-Min Yuan, a professor of epidemiology at Pitt’s Graduate School of Public Health, said the state used appropriate methods in analyzing whether the Washington County cases represented a cancer cluster or were a statistical anomaly.
He said the sample size of cases in the district was too small to determine whether there was a cancer cluster.
“It is unusual for this small area to have three Ewing cancers occur in a very short time period, but the scientific evidence does not support it yet,” Yuan said.
When the department announced it was performing the study, it said it would be looking into “possible environmental risk factors” for cancer in the area. The district includes a former radium and uranium plant in Canonsburg. It’s also in one of the busiest natural gas areas in the state, near more than a thousand shale gas wells and several compressor stations and other natural gas processing facilities.
The agency said it will continue to monitor the rate of pediatric cancers in the district as new data become available.