Polychlorinated Biphenyls (PCBs) are widely used throughout the world since the middle of the past century, they are components of transformers, capacitors, hydraulic and heat exchange fluids, and the dismantling and burning activities enhanceits release into the surrounding soils. PCBs are hydrophobic, which are tend to beaccumulated in organisms and magnified through the food chain.The legacy of PCBs in environment poses toxic effects in human, and even the whole ecological system. 

The Midway Atoll is in the North Pacific Ocean 1100 miles northwest of Honolulu, Hawaii. During World War II, several aircraft carriers and hundreds of aircraft were sunk near the Midway. PCBs have been released to the surroundings from the generators, capacitors, etc. of the sunken aircraft carriers and aircraft.  

In order to investigate the concentrations and potential source of PCBs in the soil of the Midway Atoll, a study was conducted by Dr. GE Jing,under the supervision of Professor WANG Jun, from Key Laboratory of Aquatic Botany and Watershed Ecology, Wuhan Botanical Garden. Twenty eight of polychlorinated biphenyls (PCBs) were studied in soils from the Midway Atoll. The analytical procedure involved the application of accelerated solvent extraction (ASE) and gas chromatographycoupled with ion trap mass spectrometric detection (GC/ITMS) for identification and quantification. Among the 28 PCB congeners studied, 26 of them, except CB195 and CB209, were detected in the analyzed samples at different frequencies. The total concentrations of 26 indicator PCBs (SPCBs) ranged from 2.6 to 148.8 ng g^-1 with an average value of 50.7 ng g^-1 and median of 39.5 ng g^-1. Sources and congeners’ pattern of PCB were investigated in the soil of Midway Atoll as well.  

The results showed that the concentrations of PCBs in this area were at the medium level compared with several different places around the world. According to the principal component analysis, the compositions of PCBs in most of the soil samples were similar, which indicated that the pollution of PCBs probably originated from the same source. Furthermore, risk assessments via ingestion, dermal and inhalation were evaluated based on the data obtained. The cancer risk of PCBs in the soils fell into very low range. 

Since the Midway Atoll is a wildlife refuge, and a breeding and feeding habitat for seabirds, threatened green sea turtles and Hawaiian monk seals, this study provided the reference for the distribution, sources and risk assessment of PCBs and data for environment protection and restoration. 

This project was supported in part by the U.S. Fish and Wildlife Service (QXL) and Open Funding Project of the Key Laboratory of Aquatic Botany and Watershed Ecology (JW), Chinese Academy of Sciences. Relevant results were published in PLOS ONE 8(8): e71521. doi:10.1371/journal.pone.0071521 entitled “Distribution, Sources and Risk Assessment of Polychlorinated Biphenyls in Soils from the Midway Atoll, North Pacific Ocean”.