The pseudo Pelger-Huët anomoly as a potential biomarker for chronic low-dose radiation exposures of Sus scrofa leucomystax and Apodemus speciosus

Abstract

On March 11, 2011 a 9.0 earthquake struck off the east coast of Japan, resulting in a near 20-foot Tsunami that devastated the coastline. Among the damage was the Fukushima-Daiichi nuclear reactor which over pressurized, due to failed cooling systems, leading to the release of a plume of radionuclides into the surrounding environment that included Iodine-131, Cesium-134, and Cesium-137. The people of the region were immediately evacuated, many of whom have still not returned to the exclusion zone, leaving nature to take over. Many wildlife populations, including the Large Japanese Field Mouse (Apodemus speciosus) and Wild Boar (Sus scrofa leucomystax) have begun to thrive in the region largely due to the absence of human influence. The contaminated environment in which these animals live provides a unique opportunity for radiobiological research involving chronic low dose exposures, similar to those that human inhabitants of Fukushima Prefecture and radiation workers are likely to experience. Here, quantitative bio-dosimetry was employed to evaluate environmental radiation exposure in two wildlife species. Specifically, frequencies of abnormal neutrophils referred to as pseudo Pelger-Huët anomalies (PPHAs) in peripheral blood of the large Japanese field mouse and wild boar living in exclusion zone and control zones. PPHAs have been shown to be informative biomarkers of radiation exposure in several scenarios, including archived slides from the 1958 Y-12 criticality accident, the radium dial painters from the first half of the 20th century, and chronically exposed bats in South African caves containing high levels of thorium. The PPHA morphology was indeed confirmed in the blood of exposed wild boars, however PPHAs did not occur in the large Japanese field mouse. In the future, this PPHA approach needs to be compared to other quantitative methods of estimating dose to wildlife, e.g., dicentric chromosome analysis. The potential impacts of this study include influencing the time frame in which the people of Fukushima can return to their homes, as well as reducing the cost incurred for bio-dosimetric analyses in the event of accidental or occupational radiation exposure.