exposure of some Marshallese to radioactive fallout in 1954 (10). Nevertheless,
the program encompasses many aspects of health care not related to radiation.

Specimen collection. Nonfasting blood samples were collected at the time of
medical examination in New York, Rongelap, or Majuro. The venipuncturesite

was cleansed with 70% isopropyl alcohol (Tomac Prep Packet, Amer. Hosp.

Supply, Edison, N.J.). Multisample Vacutainer blood collection tubes Model B-D
6453, containing disodium EDTA, and Model B-D 6512 (Becton, Dickinson and
Co., Rutherford, N.J.) were used for red cells and serum, respectively. Packed
red cells were obtained after washing the anticoagulated blood three times with
normal saline (0.9% sodium chloride injection, Travenol, Deerfield, Ill.). Red

cells and sera were frozen in polyethylene chemical containers (Bel-Art, Pequan-

nour, N.J.) for transport and storage. The sametype of vial was used for storage
of atoll water and coconut liquid collected for the evaluation of environmental
sources of Br in drinking fluids.
Specimen analysis. In preparation for analysis 300-ul samples of thawed serum
or red cells were layered onto Parafilm over an area of 1 cm?. The specimens

were then covered to avoid dust contamination andair-dried. Sample processing

was alternated among the groups of specimens to minimize systematic bias in

preparation or analysis.

For EDXRFanalysis the sample was irradiated with soft X rays emitted by a
1099Cd radioactive source. This technique creates vacancies in the inner atomic

shells of the elements. The subsequent emission of characteristic X rays by the
target atoms is monitored by a Si(Li) detector. The signals are processed by standard electronics and displayed in the form of a pulse—height distribution. This
method enables quantitative and qualitative evaluation of the sample composi-

tion. In the present study, red cells were analyzed for Cl, K, Fe, Zn, Br, and Rb,
and the sera were analyzed for Cl, Zn, and Br. Other elements were below the
detection limits of the EDXRF system employed.
Calibration. The EDXRF system was calibrated for Br with the addition
method in which serum and red cell samples were spiked with graded amounts of

Br (5 to 15 g/ml) in the form of NaBrOQ;. It was determined that the mean value
of 3296 counts of Br corresponds to a concentration of 1.3 pg Br/ml of packed red
cells (the calibration line is ppm = 4.02 x 10-4 XRF —4.83 x 10-4 where XRF

is the Br peak intensity) and a mean value of 23,971 counts corresponded to 6.4

pg Br/ml of serum (calibration line is ppm = 2.62.10-+ XRF + 8.33.10-2). These

values were used to calculate absolute Br concentrations in the blood samples.

Statistical analysis. For analysis of normalized values of all the detected ele-

ments, a standard one way analysis of variance (ANOVA) wasused. The test

was applied to test the equality of group means, and statistics were computed to
test the equality of means between each pair of groups. The nonparametric Wilcoxon rank sum test and Spearman’s rank correlation were used for analysis of

group differences in serum and red cell Br levels.

Possible contamination of containers was investigated. Vacutainers are known

to be contaminated with inconsequential amounts of Br (<0.006 and <0.05 wg per


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