ee eT ek
76
OF
Cet BRAT A
ADAMSET AL.
TABLEII
Age Distribution of Hepatitis B Seronegative Persons in Rongelap Exposed and Comparison Groups
Percentage seronegative
Group
Number of
Numberof
Meanage(+SD)
Age group
persons
seronegative
seronegative
(years):
29-39
40-49
>49
61
Lt
39.7 + 10.8
25.0(7/28)
16.7(2/12)
9.5 (2/21)
95
9
41.7+ 10.3
12.2 (5/41)
10.0(2/20)
5.9 (2/34)
>0.30
>0.50
>0.30
tested
Rongelap
exposed
Rongelap
comparison
persons
persons
P value*
* x? analysis of Rongelap exposed versus comparison group.
Antibody to 6 antigen was determined by a blocking enzyme immunoassay using human anti-é IgG and
é antigen derived from chimpanzee liver.
Statistical testing ofdifferences in the prevalence of HB markers was performedby x? analysis ofindependence between two or more groups; the Kruskal-Wallis test was used for comparing HBsAgratio units.
Analysis by age was based on the groupings of <29, 29-39, 40-49, and >49 years. Since the adult prevalence ofpositive hepatitis B serology was reached during the second decadeorearlier,it was judged probable
that most persons >49 years of age had acquired hepatitis B prior to the 1954 fallout, whereas the younger
groups would include those most likely to express an interaction between radiation exposure and acquisition of the infection.
RESULTS
Serologic evidence of prior hepatitis B infection was widespread by adulthood in
the Marshallese population tested (Table I), with the sexes showing equivalent preva-
lences. No significant difference in the prevalence of at least one hepatitis B marker
was detected when evaluated accordingtoatoll of residence (x (3) = 1.86, P > 0.50),
age group (x? (3) = 1.10, P > 0.70), or radiation exposure group (x? (2) = 4.36,
P > 0.10). The prevalence of seronegativity did not differ significantly between the
Rongelap exposed and the comparison group (x? (1) = 1.88, P > 0.10), even when
analyzed by age (TableII).
HBsAgwas detected in 1 1.5% ofthe total population tested (Table I). The relatively
low prevalance in the exposed Rongelap population was notsignificantly different
from the comparison group (x? (1) = 1.83, P > 0.10). All of the Utirik population
tested were exposed, thereby precluding a comparison of their very high prevalence
with unexposed Utirik inhabitants. Because the prevalence of HBsAg by atoll was
also lowest on Rongelap (x? (3) = 19.39, P< 0.001), prevalence byatoll was recalcul-
ated after excluding the exposed Rongelap group.A statistically significant variation
amongatolls remained apparent(x? (3) = 14.18, P< 0.01), with Rongelapstill having
the lowest prevalence. When grouped by age, the oldest population had the highest
mrmas
rms
CSi
P39
#
csi
prevalence of HBsAg (Table I), although group differences were notstatistically significant (x? (3) = 1.77, P > 0.50). The meanlevels of HBsAg antigen (+SD) among