By Kim Smiley
A recent study found that babies born on the West Coast of the United States shortly after the Fukushima nuclear reactor meltdown have a higher rate of congenital hypothyroidism than those born a year earlier. Thyroid issues have long been known to be associated with exposure to radiation and this finding feeds worries about the long term and long distance impact of the reactor disaster.
This issue can be analyzed by building a Cause Map, a visual root cause analysis, which intuitively lays out all the causes that contributed to an issue. A Cause Map is built by asking “why” questions and adding the answers to the Cause Map to show the cause-and-effect relationships.
Why has the rate of congenital hypothyroidism increased? This happened because the infants had radioactive iodine in their thyroids and radioactive iodine may affect the functioning of the thyroid if ingested. If the thyroid doesn’t function properly, it can’t make the necessary hormones for healthy development and both growth and development can be stunted. The impacts of radioactive iodine are predominantly seen in the thyroid because ingested iodine concentrates in the thyroid where it is used to produce hormones. The body can’t distinguish between stable and radioactive isotopes of iodine and it will store whatever iodine is available so ingested radioactive iodine can be kept within the body long enough to cause damage.
In the cases of fetuses, the mother passes iodine to her baby. If pregnant woman ingests radioactive iodine, some of it will likely end up in the thyroid of her baby who needs the iodine to develop properly. In this example, pregnant women on the West Coast were exposed to significantly higher than normal levels of iodione-131 following the Fukushima meltdown. Iodione-131 is a fission product that is created in a nuclear reactor when atoms are split. When the reactor containment failed, radioactive isotopes of iodine were released into the environment along with other fission products. Winds carried some of the radiation across the Pacific Ocean. Iodine-131 concentrations in precipitation in the United States were up to 211 times above normal in the days following the accident. Some of this radioactive iodine found its way into the food supply and was ingested by people, some of them pregnant women causing the increase in cases of congenital hypothyroidism.
The good news is that congenital hypothyroidism with can be treated if found early. The bad news is that there may be more health issues from the Fukushima meltdown in places outside of Japan discovered in the future. The reality is that more than two years after the event we still don’t know what all the impacts of the radiation will be, both in Japan which has obviously suffered the most and in other countries.