Radioactivity in the areas near Los Alamos National Laboratory is due largely to natural sources, lab officials said in releasing the results of a study it conducted in August.

The LANL study largely confirmed the data published in a July 2007 report by the Government Accountability Project, but LANL's conclusions are different, according to LANL scientist Michael McNaughton.

The Government Accountability Project reported last year that there were elevated levels of radioactivity in dust samples taken from homes and workplaces near the Northern New Mexico lab.

While acknowledging the need for bigger studies, GAP said at the time that the radionuclides found in the samples "most likely" were generated at the nuclear weapons lab, which has been operating for more than six decades.

The lab said Wednesday that its study conducted by scientists in LANL's Environmental Programs Directorate used samples collected from the areas previously sampled by the GAP researchers.

The samples were analyzed by an independent laboratory in Colorado.

McNaughton said the LANL analysis showed that 99 percent of the measured radioactivity — and almost the entire dose received by Los Alamos residents — is natural.

Less than 1 percent is due to global fallout resulting from worldwide nuclear weapons testing, according to McNaughton.

He also said that in the few cases where LANL activity contributed to radioactivity, it also represented less than 1 percent. The doses do not constitute a health hazard, the scientist said.

Concentrations of radioactivity in soil depend on factors including altitude, rainfall, snowfall, soil permeability, and the shape of the terrain, according to McNaughton. He said the Los Alamos area's high elevation — about 7,300 feet — is part of the reason for the levels of radioactivity.

According to the lab, its study also concluded that radioactivity in neighboring Embudo Valley, Picuris Pueblo, Llano and Trampas Lake could not be attributed to LANL