Letter to W J Bair, Subject: Derivation of the Numbers of Births and Deaths Expected in a Limited Group of the Marshallese People (Encls: as Stated)

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University of California LOS ALAIVIOS SCIENTIFIC LABORATORY Post Office Box 1663 Los Alamos, New Mexico87545 BEST COPY AVAILABLE Battelle Pacific Northwest Lab . Following is the derivation of the numbers on the numbers of births and deaths expected in a limited group of the Marsh allese people. A-s you will remember , we agreed that it was better to use data somewhat representative of the Marshall Island experience than to use U. S. experience even if the data on the Marshall Islands is not as good as the data in the U.S. My primzry reference was the final draft of the Marshall Islands 5-yr Health Plan prepared by the Trust Territory Dept. of Health Services Office of Health Planning and Resources Department. The document is undated , but the presence of data from 1975 indicates that it must have been prepared in the period of 1977 to 1979 ‘~hen we received it. It was noted that there are apparent inconsistencies amonq several of the different tables. For example, Table 111-1 gives data for the Marshall Islands for the period 1955-1975 and Table III-5 gives data for the infant mortality rate for 1976. In Table 111-1, the infant -death rate per 1000 births for 1970 through 1975 is given as 2S.3, 33.5, 25.4, 46.4, 21.1 and 37.0. However, Table 111-5 indicates the infant mortality rate to be only 17.04. i~e have used the data of Table 111-1 in the following estimates, because it is more complete and it provides a self-consistent set of data. Y, owever , in view of the discrepancies, the results can only be considered as approximations. In my vi?w this makes little real difference in view of the uncertainties in the risk estimating coefficients. There is also a bias built into the data because of the inclusion of Ebye and !lajaro in the overall Marshall Island ratzs. This arises from the different death rates (particularly’ infants) at these two locations. \ For the estimates we us?d the last 5 or 5 year average of the d=ti as being most representative of current conditions. From this, we 1. Rate of increase of the population - 3.8%/yr. 2. Infant death rate - 3.2% per birth. 3. Overall death rate - 0.S4% per year. 4. Birth rate - 4.2?% per year.

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LOS ALAMOS SCIENTIFIC LABORATORY A population of 550 was assumed to be the one that may move back to an island . Values for other initial populations may be obtained by ratios of the results. The total population at the end of 30 years is given by the The number of births in 30 years are given by: where x is the time between O and 30. This gives Similarly, the number of deaths in the 30 year period wauld be: One other item needed is the reduction in 30 year dose to those born ~fter the return becauss of the decrease in radiation levels and the smaller amount of time in the 30 year period that is spent on the island. For this, the total population dose for thos? born ~ft?~ returning assuming an initial dose rate of 1 rad/year is giv$n by:

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University of California LOS ALAMOS SCIENTIFIC LABORATORY Los Aiamos, New Mexico 87545 A is the half-life of decrease of the radition dose, taken here as 30 This integral cannot be solved anal-ytical. .4n approximate solution was obtained by calculatin~ this function for each of 30 years and summing. This gave .8949 rads for the total population including the original 550. The total dose received by the original 550, aSSL131itIg that all live for tins 30 years, is For those born after the return, the population would be the difference bebween the total population in 30 years, the number of deaths anti the original 550 people or 1134. Thus, the per capita dose for this group is 8949/113~ = 7.9 rads. For the original 550, the Per capita dose is 11,902/550 = 22 rads. The ratio of these two to give an estimate or the fraction of the full 30 year dose received by the The assumption of no deaths in the original 550 returning was made for simplicity and the lack of good death rate data. I also took a brief look at the age characteristics of the Marshallese from Table IV-3 and the U.S. population in 1970. This comparison is given in the attached curve. As you can see the slopes are similar above age 35 but the magnitudes are distorted by the high birth rate in the Marshall Islands. However, in terms of the relative risk the slznilar slopes mean to me that if the two natural cancer rates are similar, the relative risk for people above 35 in both populations would be similar because most of the cancer occurs at ages about 40 and above. However, the magnitude of the relative risk in the U.S. used for the Marsha~~ese will be high by a factor of s~ewhere around 2-3 because of the distortion caused by the very high proportion of young peoplz ‘who have a relatively low natural cancer incidence.