This recent Pennlive.com story about Three Mile Island and thyroid cancer is of special interest to me for a couple of reasons. One is that I was within sight of TMI’s cooling towers on the day of the partial meltdown in 1979. I was on the west bank of the Susquehanna helping my brother move from York Haven to Camp Hill. Another is that from 1981-85 I lived just east of TMI, inside “the plume” area. During those years I was a medical student at the Milton Hershey Medical Center. That’s where a lot of research was done examining the long-term health effects on the general population due to radiation release from the accident. Last but not least, my nephew’s wife – a life-long resident of central PA – recently underwent thyroid cancer surgery at Johns Hopkins.
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As stated in the article linked above, Central Pennsylvania in recent years has had one of the nation’s highest thyroid cancer rates. But experts have concluded that direct radiation exposure at the time of the TMI release was insufficient to account for more than a tiny fraction of this total. What gives? Well, as usual, the devil’s in the details. And in this case, those details have to do with human biology, with agriculture… and with the passage of time.
The first thing to note is that the human thyroid gland concentrates iodine. And human dietary iodine comes almost exclusively from fresh milk. When radiation was released from TMI, it blew east and landed “inside the plume” on prime dairy pasture land. Dr. David Brenner ties it together in this 2011 piece from Time magazine:
“The way radioactive iodine gets into human beings is an indirect route,” he said. “It falls to the ground, cows eat it and make milk with radioactive iodine, and you get it from drinking the milk. You get very little from inhaling it. The way to prevent it is just to stop people from drinking the milk.” He said that the epidemic of thyroid cancer around Chernobyl could have been prevented if the government had immediately stopped people from drinking milk.
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Of course, at TMI only a tiny fraction of the radiation was released into the atmosphere compared to Chernobyl. Still, the biological mechanisms are the same. Thyroid cancer is extremely slow growing. And babies have an increased cancer risk from radiation exposure because their cells are rapidly dividing. So, you might expect to see an mini-epidemic of thyroid cancers in middle aged people who had radioactive Iodine exposure decades earlier when they were infants drinking a lot of fresh milk. That actually may be the case here. But convincing public health people – and insurance companies – to see it that way? Well, that’s a whole ‘nuther ballgame.