The horrific earthquake and tsunami in northern Japan remind us that no matter how powerful we become or careful we are, nature asserts itself in ways that we can’t imagine. Â The nuclear engineers and technicians working to contain the radiation leaking from the damaged power plant in Fukushima are nothing short of heroic. Â Radiation can cause all sorts of ills, from acute sickness to cancer and infertility.
In the testis, developing sperm cells are exquisitely sensitive to radiation. Â Kyodo News reported that after an explosion at the Fukushima No. 2 reactor on March 15, radiation levels measured as high asÂ 8,217 micro sievert or 0.8217 rem per hour.Â Â (Micro sievert and rem are units of radiation dosage.)
Does that amount of radiation harm developing sperm cells? Â I askedÂ Marvin Meistrich, Ph.D., Professor of Experimental Radiation Oncology and the Florence M. Thomas Professor of Cancer Research at the University of Texas M. D. Anderson Cancer Center, a world’s expert in radiation and sperm. Â Dr. Meistrich explained that sustained exposure to 20 rem of radiation over 4 weeks caused sperm counts to drop to 1/10th of their original amount. Â At doses of 40-80 rem, sperm counts fell to about 1/100th of the starting number, and in some cases were wiped out entirely. Â At 200 rem, that drop to zero sperm became permanent. For one-time doses, Dr. Meistrich explained that 15-20 rem caused a short-term fall in sperm count, and 400 rem or more resulted in permanent loss of sperm.
We know that radiation changes DNA, the sperm’s precious genetic cargo. Â What we don’t know is what dose causes a harmful DNA change that damages a developing embryo or causes disease later in life.
The radiation leakage in Fukushima seems to be in the range at which damage to sperm occurs. Â I can only hope that the workers at Fukushima and the people near the plants are aware of the dangers and take action to protect themselves.