Thursday, April 17, 2014

Chernobyl Acident and Thyroid Cancer


Analisa and I are looking in the effects of radiation and thyroid cancer. An interesting incident occurred in Chernobyl which led to high numbers of thyroid cancer, which is detailed in this article.
   In 1986 a nuclear power plant in Chernobyl exploded causing the surrounding areas of Belarus, Russia and Ukraine to receive high doses of radiation.  The major radioactive material that contaminated the area, which affected more than 5 million people, was iodine-131 and caesium-137.  One of the major health problems reported were high incidents of Thyroid cancer in children and young adolescent.  This is significant because the thyroid gland is the major organ responsible for the metabolism of iodine, here inherently is the problem.  The iodine released from the plant contaminated the surrounding areas soil therefore contaminating the grass the cows ate.  The cows produced iodine enriched milk which was consumed by many children and young adults near the power plant and surrounding areas.  On average the amount of radiation one was exposed to was about 0.03 Gy (gray, the SI unit for ionization radiation), and the threshold for many organs in the body is 45 Gy.  But, by directly consuming the iodine milk on more than one occasion the thyroids received enough radiation to induce cancer.

   A study by Jacob Radiol found that from 1992 to 2002 more than 4000 cases of thyroid cancer were reported in children from 0-18 years of age in the areas surrounding the plant.  The graph below, found in this paper, shows incidents of thyroid cancer reported throughout the years after the accident.  The data suggests that there is a two year gap period in which the rates of thyroid cancer do not seem to be increasing at an alarming rate, but after two years the rate of reported thyroid cases increases, and continues to increase as the years go on.  This delay in the occurrence of thyroid cancer would suggest that it takes time before the cancer can form in the individual, which follows suit with a major hallmark of cancer which is that several steps must occur before cancer can develop.  The reason it takes time for the cancer to develop is twofold: one, the amount of milk that is contaminated with iodine varies among each individual and two, the amount of iodine in the milk varies over the affected area.  What this means is that, it would take a certain amount of milk at a certain radiation to cause cancer.  Lower amounts of radiation in the milk would mean that more milk needs to be consumed to cause problems, and if there are high amounts of radiation less milk would need to be consumed.  The delay in cancer development, from the data, suggests that the amount of radiation in the milk was low enough that more contaminated milk needed to have been consumed in order to cause the cancer. 

   This data suggests that the amount of iodine-131 was enough to infect enough cows which in turn produced milk with enough iodine which infected the thyroids of those who consumed the milk.  The contaminated milk then affected the thyroids of those drinking and therefore led to thyroid cancer.

"Chernobyl’s Legacy:Health, Environmentaland Socio-Economic Impacts and Recommendations to the Governments of Belarus, the Russian Federation and Ukraine" 2nd ed.

Radiol, Jacob. "Thyroid cancer among Ukrainians and Belarusians who were children or adolescents at the time of the Chernobyl accident." IOP science. 2006.