The investigation into a contaminated pillow indicated that the contamination was intentional.

The Case of the Radioactive Pillow
George Hamawy

Abstract: A married couple pursuing their Ph.D. degrees at Columbia University were involved in a case of radioactive contamination.  A bedpillow was found in their apartment that was contaminated with ³²P.  This paper describes the investigation of this case and, the findings. Health Phys. 81(Supplement2):562-564; 2001

Key words: operational topic; dose assessment; exposure, occupational; ³²P

On 9 February 2000, the Radiation Safety Office received a telephone call from a laboratory reporting a contamination incident that had occurred the previous day (8 February 2000). A graduate student had been using the radio-isotope ³⁵S.A routine survey at the end of an experiment had shown that the graduate student's fingers were slightly contaminated.  A survey by the radiation safety personnel confirmed that the student's fingers as well as a small spot on her head were slightly contaminated, reading approximately double the background radiation level (0.04 mR h^-l). A sample of her urine was collected and analyzed the same day; no ³⁵S contamination was detected. The urine sample was labeled and stored for future reference. The laboratory where the experiment was conducted was surveyed and no radioactive contamination was found.

The following day (10 February 2000), the student informed the Radiation Safety Officer (RSO) that during the previous evening, worried about her contamination, she borrowed her laboratory's Geiger counter and surveyed her apartment. She said that she had found a highly contaminated pillow on her bed.

Immediately, the radiation safety personnel went to the student's apartment to conduct a survey and to bring the pillow to the radiation safety office. The contaminated pillow, without a pillowcase, had been placed in a large plastic bag, which was retrieved from one of the apartment's closets and presented to the radiation safety personnel.  The apartment was surveyed and no contamination was detected anywhere.

The plastic bag containing the pillow was brought to the radiation safety laboratory, and the pillow was subsequently removed from the bag for survey and analysis.

When a gloved finger touched one of the pillow's surfaces, the glove became contaminated, indicating that the contamination was readily transferable. The measurement on the contaminated surface of the pillow was not uniformly distributed. The measurement at a I-em distance from the surface, using a Geiger counter with a pancake probe, varied between 200 mR h^-l in some areas to 50 mR h^-l at others. At some spots it was much higher than 200 mR h^-l.

A small piece of the contaminated pillow's fabric was cut then measured and analyzed using a liquid scintillation counter. The contaminant was found to be ³²P. No contamination was found below the surface of the pillow's stuffing. The total amount of ³²P on the pillow, using the liquid scintillation counts, was estimated to be between 150 and 200 microcuries.

The student's husband was also checked and was found to have a similar pattern of body contamination as his wife, namely, contaminated fingers and a small spot on the head, all reading approximately double the background level.

Urine samples were obtained from both of the graduate students and were analyzed in addition to her original urine sample.  A small amount of ³²P was detected in all the urine samples. Thereafter, urine samples were obtained and analyzed whenever the two students were available (Fig 1). Her film badge was sentfor emergency processing and the results were negative.

The large amount of radioactivity found on the surface of the pillow excluded the possibility that casual contamination had occurred. It was clear to the RSO that most likely the contamination was the result of a deliberate act. Additionally, the fact that no contamination was detected anywhere in the apartment was a strong indication that no one had slept on this pillow after it was contaminated. The large amount of easily transferable ³²P on the pillow surface was highly supportive of the above assumption. The chemical and physical characteristics of the material were not crucial items of inquiry because of the complete lack of contamination anywhere else in the apartment.

The two students claimed that a pillowcase was on the pillow the previous night, and that they had washed it in the bathroom tub after they discovered the contamination.

Such a claim was considered by the RSO to be highly unlikely; a pillowcase touching the contaminated pillow would have been contaminated on the inside surface of the pillowcase, and if the contaminated pillowcase had been washed in the bathtub, some ³²P should have been detected in the bathtub. The pillowcase and the bathtub were surveyed thoroughly, and no contamination was found.

The NewYorkCity Department of Health (NYDOH), the regulatory agency that oversees radiological health in New York City, was notified on 11 February 2000. Two NYDOH inspectors arrived at the university the same day and conducted their own investigation of the case. The university's upper management and the Radiation Safety Committee were also notified and were briefed as to the nature of the finding. As a precautionary measure the two students were sent to the University Health  Services for medical and psychological evaluation.

On 24 February 2000, the RSO requested that the University immediately suspend the two students. The deans of their respective schools suspended the two students pending an inquiry. A hearing by the university's Committee of Grievances and Discipline followed the suspension. The outcome of the hearing and the negotiations that followed are kept confidential; however it is sufficient to say that the two students were permanently banned from having access to any laboratory that uses radioactive material.

Three important issues had to be addressed. The first issue was finding the source of the ³²P.The second issue was to find the motive behind the deliberate contamination of the pillow. The third and most important issue was to evaluate the radiation exposure that the two students had received.

Possible sourceof the radioactive phosphorous: The husband had no access to any laboratory that used radioactive materials. On the other hand, the wife had access to all the laboratories located on the floor of the science building where her laboratory was located.  The day the incident was discovered an inventory of all the radioactive materials in her laboratory was conducted and no material was found missing.

An. adjacent laboratory that uses large amounts of ³²P was also checked for missing material; however, due to the large volume of ³²P received, used, and disposed of weekly in the laboratory, a precise determination of missing material was hard to determine with certainty.

Possible motive for the contamination: The investigation concluded that the contamination of the pillow was deliberately done by the student. The question then was why would a person intentionally contaminate his/her pillow?  For what purpose? Given the fact that no one slept on the pillow after its contamination, it appeared that there was no intended "victim."

In order for the RSOto calculate the internal exposure received by the two students, urine samples, whenever they were available, were collected and analyzed. The activity in the two students' urine samples, as shown in Fig. I, is consistent with the natural initial process of biological elimination of phosphorous. The fact that the peak of the activity in the urine was reached four days after the contamination was discovered on the students' fingers is an indication that the fingers' contamination, and hence ingestion, occurred around the time of the discovery of contamination.

The amount of activity in theurine sample of the wife on the fourteenth day raised an interesting point. The amount of activity in her urine sample that day was far from the expected result and was the same as the result of her husband's urine sample. The assumption was made that the two samples collected that day were both from him.

The amount of activity in the urine of the two students was integrated for 20 d, and two assumptions were made: (1) each student excreted 1 L of urine daily, and (2) 50% of the amount of phosphorus ingested was excreted in the urine in the initial phase. A total amount of ³²P ingested was calculated to be approximately 2-3 microcuries by her and 4-6 microcuries by him.

The Annual Limit of Intake (ALI) for ³²P ingested (all compounds) is 600 microcuries, which would deliver a total body dose equivalent of 5,000 mrem. Based on this value, the dose that was received by her was calculated to be 20-30 mrem and by him to be 40-50 mrem.

Fortunately, no one was harmed in this bizarre incident.  The amount of exposure that the two students received was considered small with no potential for consequences. Stricter control measures for access to radioactive materials were devised and implemented.

International Commission on Radiological Protection. Limit of intakes of radionuclides by workers. Oxford: Pergamon; Publication 30; 1984.

U.S. Code of Federal Regulation. Title 10: part 20, Appendix B, Standard for Protection against Radiation. 1991.

* Office of Health and Radiation Safety, Columbia University, 398 Engineering Terrace, MC 2215, 500 W. 120th Street, New York, NY 10027.  For correspondence or reprints contact the author at the above address.

George Hamawy is the Radiation Safety Officer at Columbia University in the City of New York. He received his bachelor's degree in Nuclear Engineering from Alexandria University, Egypt; a master's degree from City University of New York in Environmental Health Science and a master's degree from New York University in Applied Science. He has over 30 years of experience in handling radioactive materials used in biomedical applications, physical and chemical sciences and in industrial processes. His email address is ghB1@columbia.edu.

Copyright ~ 2001 Health Physics Society