Studying the effects of alpha particles on zebrafish embryos with the help of CR-39 nuclear track detectors

Abstract

Alpha particles from inhaled radon progeny are the most common source of irradiation of the human respiratory tract. Not only the human respiratory tract may be affected, radon may dissolve into the blood and enter other organ through the blood circulatory system. Radon progeny in the blood of a pregnant woman may affect the embryo through the exchange of nutrient at the placenta. It is therefore important to estimate the effect caused by alpha particles to the embryo by using zebrafish embryo as a vertebrate model. Study has been shown that alpha particle would cause morphologic abnormalities in 48 hpf zebrafish embryo. In this project, we want to further study the relationship between occurrence of malformation and the absorbed dose of the zebrafish embryo. CR-39 solid-state nuclear track detectors with a thickness of 16 μm are used as support substrates for holding the zebrafish embryos during irradiation. It can also help to record the alpha particle incident position so that the number of alpha particle actually going into the embryo cells can be found, thus, it can enable the calculation of absorbed dose of the embryo cells. In this study, planar 241Am source with an activity of 0.1151μCi and main alpha energy equal to 5.49 MeV was employed. Five sets of experiments with irradiation times of 2, 4, 6 and 8 min were conducted. Observations were made when the irradiated embryos were developed to 48 hpf to determine whether malformation had occured or not. Among 112 irradiated zebrafish embryos, 21 of them showed morphologic abnormalities. The smallest value of absorbed dose that caused malformation in this study was 0.51 mGy and the largest value was 2.2 mGy. These correspond to 5.17 and 22 mSv equivalent doses in human, respectively.