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. The nuclear engineers and technicians working to contain the radiation leaking from the damaged power plant in Fukushima are nothing short of heroic. 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. Kyodo News reported that after an explosion at the Fukushima No. 2 reactor on March 15, radiation levels measured as high as 8,217 micro sievert or 0.8217 rem per hour. (Micro sievert and rem are units of radiation dosage.)
Does that amount of radiation harm developing sperm cells? I asked 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. 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. 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. 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. 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. 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.