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In an Environmental Surveillance report for 2007 that was issued in early October, Los Alamos National Laboratory identified the location of the maximally exposed individual (MEI) — exposed by the airborne pathway – as an air monitoring station across from the Fire Station on DP Road, a few hundred yards west of the Los Alamos Monitor.
The MEI is a standard measure for identifying where the largest off-site radiation dose might occur to a hypothetical member of the public. For many years the location for the airborne MEI was at East Gate, the main entrance to the townsite, because of its proximity to the Los Alamos Neutron Scattering Center and the direction of the prevailing winds.
But, according to the surveillance report, a “leak” at LANSCE was repaired in December 2005, when offsite exposure was significantly curtailed.
In 2006, the location was identified at the Los Alamos County Airport, because of a contaminated ash pile that has since been remediated.
The dose at East Gate in 2005, which was the worst year since 1994, was 6.46 millirem per year, approaching the 10 millirem allowable maximum for offsite airborne exposure.
The most recent airborne MEI on DP Road, by comparison, was 0.52 millirem per year, about .2 percent more than the average American receives, which the surveillance report concludes, “causes no observable health effects.”
The dose in the DP Road area was attributed to “plutonium re-suspended” during preparations for cleanup of Material Disposal Area B, a legacy waste disposal site, located south of the road, according to the report.