THE LINK BETWEEN CANCER

The Link Between Cancer and Environmental Radiation Exposure

Tina Cassar, BSN, RN

A Capstone Presented to the Faculty of the Department

of Nursing of Western Governors University

in Partial Fulfillment of the Requirements for the Degree of

Master of Science in Nursing, Education Specialty

February 2010

Chair: Michelle Winters, MSN, MBA/HCM, RN, NHA, LNCC

Chapter 4: FINDINGS

Materials and methods

Earlier reports addressed methods used and initial findings from the baby tooth study (Gould et al., 2000b and Mangano et al., 2000). These teeth were processed using a scintillation counter from the University of Waterloo in Ontario, Canada. In June of 2000, RPHP leased a Perkin-Elmer 1220-003 Quantulus Ultra Low-Level Liquid Scintillation Spectrometer. Introduced in 1995, only approximately 15-20 units are now in use in the US (Laxton, Mark, Perkin-Elmer, 2002).

The new counter is located on the premises of REMS, Inc., a radiochemistry laboratory in Waterloo, and not at the University of Waterloo, thus changing the level of background radiation. Also, the method of removing organic material from the teeth was changed by treating them with hydrogen peroxide prior to grinding them into powder. This procedure proved to be more effective in allowing light produced in the liquid scintillation fluid by the beta particles emitted by the Sr-90 and its daughter product, Yttrium-90, to reach the photomultipliers. This greater efficiency is caused partly by shifting the spectrum of the light emitted by the scintillation fluid. As a result of these changes (the counter, its location, level of background radiation and method of cleaning teeth), the efficiency of detecting the very low radioactivity in single teeth was more than doubled overall. However, the data lack a consistent factor that could be used to analyze teeth from both counters together. Thus, this report will be based solely on the 2089 deciduous teeth tested after June 2000.

RPHP sends teeth to REMS for testing, and Sr-90 levels are measured individually. Lab personnel are blinded about all information concerning each tooth, that is, they know nothing about characteristics of the tooth donor. This blinding helps assure objectivity in results. The laboratory measures the concentration of Sr-90 by calculating the current activity (in mBq) of Sr-90 per gram of calcium in each tooth (mBq Sr-90/g Ca). (See Appendix A for more specific technical procedures.) The strontium-to-calcium ratio has been used in the St. Louis study in the 1960s, and all other recent baby tooth studies mentioned earlier.

The laboratory returns results to RPHP staff, who converts the ratio to that at birth, using the Sr-90 half-life of 28.7 years. The Sr-90/Ca ratio for a single tooth is not a precise number because a typical baby tooth is small in mass. The counting error for each tooth is plus or minus 26 mBq, and somewhat less for the larger teeth.

RPHP conducted several tests to assure the inter-laboratory reliability and internal consistency of its results. It selected 10 teeth from persons born in 1954 in St. Louis that were tested both by REMS and the University of Georgia Center for Applied Isotope Studies, which operates three counters ...