Radiation Overdose in Costa Rica, 1996

Maggie Steffens
May 3, 2017

Submitted as coursework for PH241, Stanford University, Winter 2017


Fig. 1: Fig. 1: Many effects of radiation overexposure were exhibited in the Costa Rica case of 1966. It is important to be cautious and create awareness. (Source: Wikimedia Commons

People are putting their lives in the hands of another when it comes to medicine. Although doctors and medical technicians are professionals and experts, they are still human and can make mistakes. A particularly poignant case occurred in in 1966, when 109 cancer patients in San Juan, Costa Rica were accidentally overexposed by radition. [1]

Radiotherapy is is well established as an effective and important cancer therapy. In radiotherapy, radiation is used directly to destroy malignant tissue. As radiation penetrates into the body, it also destroys healthy tissue. [2] Therefore, there is a balance to be achieved in order to effectively utilize this technique. The success of such practices "depends on achieving a radiation dose that is high enough to kill malignant tissue yet sufficiently low to preserve healthy tissue." [1] (See Fig. 1.)

The Accident

The accident occurred in the radiotherapy Alcyon II unit of the radiotherapy facility at the San Juan de Dios Hospital in San Jose, Costa Rica. [3] On August 22, 1996, a Co-60 radiation surce had been replaced, but when it was calibrated, an error was made in calculating the dose rate. [2] This miscalculation resulted in the administration to patients of significantly higher radiation doses than those prescribed. [4] This overexposure was severe and amounted to a major radiation accident. It wasn't until September that the error was discovered. The radiotherapy machine was then shut down, and a team was called in to analyze the accident.

The team found that, "the exposure rate had been greater than assumed, by about 50%- 60%" because a wrong valve size had been used. [2] This made the dose to patients proportionately higher than intended, thus explaining the overexposure. [4] There were 7 fatalities and 81 injuries due to this accident. Specifically, "of 42 patients that died through 7 July 1997, 3 died probably as a direct result of radiation exposure and 4 more with radiation exposure a contributing cause. Another 22 died probably of their disease and not of radiation exposure. Of the surviving overexposed patients, 4 suffered "catastrophic" consequences, 16 more severe effects, 26 had lesser effects, and 22 had no effects." [4] There were many complications: severe skin reactions with ulceration, mucosal reactions, and blockage of the pharynx and esophagus. [1] By some accounts 17 deaths resulted from this accident. [4] Unfortunately, a very tragic event.


Humans will always make errors of judgment. It is therefore necessary to put effective checks and procedures in place to catch and correct mistakes. This includes aspects of the system that are not obvious (at the time) sources of potential troublem. In the case of San Juan de Dios Hospital, a simple valve mixup no under direct control of the doctors and nurses in charge rendered the therapy fatal. It is therefore very important to carefully study accidents such as this one and implement improved safety procedures that will stop such accidents from happening in the future.

© Maggie Steffens. The author grants permission to copy, distribute and display this work in unaltered form, with attribution to the author, for noncommercial purposes only. All other rights, including commercial rights, are reserved to the author.


[1] I. Gusev, A. Guskova, and F. A. Mettler, eds., Medical Management of Radiation Accidents, 2nd Ed. (CRC Press, 2001).

[2] K. Coeytaux et al., "Reported Radiation Overexposure Accidents Worldwide, 1980-2013: A Systematic Review," PLoS ONE 10, e0118709 (2015).

[3] "Costa Rica Patients Hurt By Radiation Overdoses," New York Times, 13 Oct 96.

[4] J. C. Nénot, "Radiation Accidents Over the Last 60 Years." J. Radiol. Prot. 29, 301 (2009).