A COMPARISON OF SR90 COMPONENT OF HUMAN AND COWS' MILK

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A COMPARISON

OF

5R9#{176}

COMPONENT

OF

HUMAN

AND

COWS’

MILK

Conrad P. Straub, Ph.D., and Gopala K. Murthy, Ph.D.

Robert A. Taft Sanitary Engineering Center, The Division of Radiological Health,

((71(1 the Food Chemistry, Milk and Food Research Program, Public Health Service,

U.S. Department of Health, Education, and Welfare, Cincinnati, Ohio

(Submitted NIarch 10; accepted for publication May 19, 1965.)

ADDRESS: (C.P.S. ) Robert A. Taft Sanitary Engineering Center, 4676 Columbia Parkway, Cincinnati.

732

PEDIATRICS, Vol. 36, No. 5, November 1965

I

NFORMATION OIl the concentrations of

specific radionuclides in htiman milk

as velI as in cows’ milk is needed to under-stand potential exposure to radiation of in-fants consuming these milks. Considerable data are available on radionuclide concen-trations in cows’ milk,’ but similar data for

human milk are meager.25 To obtain data

on radionuclide concentrations in human

milk, samples of human milk were

ob-tamed from Denver, Colorado (July 9, 1959, through February, 1961), and Chicago, liii-nois (December 21, 1959, through August, 1961). The Denver samples represented

pooled htiman milk collected postpartum,

while those from Chicago represented

human milk from individtial donors

con-tributing to a milk bank. For comparison,

samples of cows’ milk corresponding to

that consumed by the donors participating

in the Chicago program were collected

(November, 1960, through August, 1961). In turn, these samples were compared with samples collected monthly from the raw-milk network serving a portion of the Chi-cago milkshed.

Samples were analyzed for calcium,

potassium, strontium-90, and cesium-137,

and the restilts are summarized in Tables I and II. As shown in Table I, the concentra-tions of strontium-90 and calcium in human milk samples from Denver and Chicago are similar, the mean geometric values being 0.62 and 0.56 picocurie of strontium-90 per

liter (pc/i), and 0.24 and 0.25 gm of cal-cium per liter (gm/i), respectively. A corn-parison of the strontium-90 and the calcium

concentrations of cows’ milk with those of

human milk from Chicago indicates that

the concentration of strontium-90 in human milk is smaller by an order of magnitude, and that of calcium by a factor of

approxi-mately 5. There is little difference in the cesium concentrations, but this could be associated with the relatively small envi-ronmental concentrations of cesium.

The measured strontium-90 and calcium concentrations in market milk reported to be consumed by the donors were similar to those found in monthly milk samples col-lected as being representative of a portion of the Chicago raw-milk production area.6 The geometric mean strontium-90 values

were 6.4 pc/I for the market milk constimed

by the donors and 6.6 pc/i for the raw milk

while the corresponding calcium values were 1.12 and 1.13 gm/l.

Radionuclide concentrations reported herein were obtained during the period of

no atmospheric nuclear tests (except for the French test of February, 1960), and

coinci-ded over a period of a few months with the collection of human milk samples from six

Toronto 2 These values were

in-tercompared during a common period (Oc-tober, 1960, through June, 1961) and show (Table III) that the Denver and Toronto values were similar (geometric mean values

equal to 0.259 gm/i and 0.79 pc/I; and

0.252 gm/i and 0.70 pc/l for calcium and

strontium-90, respectively). The values for

milk samples from Chicago for the same

period were somewhat lower, 0.230 gm/i

for calcium and 0.57 pc/i for strontium-90.

The differences were not, however,

be-lieved to be significant.

Lough et al. reported values (see Table

(2)

collect-‘#{176}Sr,pc/I Ca, g/l 9#{176}Sr/Ca, pc/gm ‘37Cs, pc/i K, gm/l 16 16 16 14 16 18 18 16 18 10 8 8 6 8 x

0.6 + I .,5.5 1<

O.24±1 *1

1< -52-- I .73

0-6 + I .16

x

0. 56 -i- I ->( 0.)25+1 .6

x .73+ 1.

N 0.31.18 N 6.4 +1 x 1-1#{247}1-o.5 x 6.05+1.15 N 1.4+1 .03

90 Sr, pc/I

Ca, gm/l “'Sr/Ca, pc/gm ‘37Cs, pc/i K, gm/I Cows’ milk-Chicago ‘#{176}Sr,pc/l Ca, gm/I ‘#{176}Sr/Ca, pc/gin ‘3TCs, pc/l K, gm/i 0.65 0.7 3.0 0.636 0.60

0.21()

2.4

0.33

6.6

1.118

6.0

I.43

0.67

U.237

3.1

0.611

0.61

0.’215

0.331

6.5

I .111 6.1

1.42l

0.’2 tol.’2

0.1-26 to 0.358

0.9 to 9.5 ND to 19 0.’271 to 0.777

0.’25 tol.4

0.1’26 to 0.301

1.1 to7.4 Ni) to 10

0.251 to 0.535

4.4 tolO

I .056 to 1 .17’2

4.1 to8.9 5 to25

1.376 to I .464

ARTICLES

TABLE I

733

CHEMICAL AND RADI0Ac’rIvE CONSTITUENTS IN HUMAN AND Cows’ MILK, JULY, 1959, ThROUGh AUGUST, 1961

n* JIQ±Og-x ill - flange

Human milk-Denver

Human milk-Chicago

6 = number of sampies.

x X

Mg Og = geometric mean ± geometric standard deviation.

“.!i = median value. M= arithmetic mean value. ND = not detected.

ed from May through June, 1959;

geomet-nc mean values were computed and found

to be 0.252 gm/i for calcitim, 0.33 pc/i for

trontium-9O, and 1.32 picocuries of

stron-tium-90 and strontium-90/calcium values

values are very similar to other values re-ported in Tables 1 and 3, but the

stron-tium-90 and strontium-90 per calcium values

are lower by a factor of about 2.

A marked difference between the

potas-TABLE II

COMPARISON OF CONSTITUENTS IN Cows’ MILK COLLECTED IN TILE ChIcAGo AREA, NOVEMBER, 1960

THROUGH AUGUST, 1961

n “#{176}Sr,pc/I

1 6

x

6.4±1.

‘, 2t 10 6.6+1.48

6 MiLk consumed by donors.

t Raw milk from portion of milkshed.

Number of samples analyzed.

-N

§Mgtg.

(3)

Ca, gm/l 0.59#{247}1.16*

No. of observations 3

90Sr, pc/i No. of observations

‘#{176}Sr/Ca, pc/gin

No. of observations

(‘hicago x 0.’230±1.6 8 x 0.57 +1.48 9 x #{247}I .90 8 x 0.79 #{247}1.83 3 x 3.04 +1.87 3 Toronlo2 x 0.51.Q4 10 N 0.70 #{247}2.0sl 10 2.73 +‘2.04 10

Lough ci (Il.’j

N 5 x 0.33 +1.65 ‘5 x 1.3 #{247}1.59 5 N * Mg+lTg.

t May through June, 1959.

TABLE III

INTERCoapARIsoN OF CALCIUM AND STR0NTIUu-90 CONCENTRATIONS OF HUMAN MILK SAMPLES COLLECTED

FEOM DIFFEHENT (;EOGRAPHIC AIIEAs OCT0BEIL, 1960, THROUGH JUNE, 1961

siufll content of human niilk from Denver

and that fronl Chicago was observed (Table

I). The geometric mean values for the two

areas were O.61.16 (16 values) and O.3

1.18 gm/l (18 values), respectively. This (hiference was believed to reflect the

(lifTer-ence between samples from these two areas.

In 1)enver, the salnples were i)Ooled from

milk collected postpartum from a number of donors and represente(1 colostruin and

tran-sitional fllilk, whereas in Chicago each

sample analyzed came from a sI)ecific (lonor an(I represented nlaturc nulk. The values

we report agree generally with values pub-lisile(1 111 the literature.7 These show

po-tassiiiin levels in colostrum (first to fifth

(lay of lactation) of 0.74 (0.66-0.87) gm/i, in

transitional milk sixth to tenth (lay of

lac-tation) of 0.64 (0.53-0.77) g/liter, an(1 in

mature milk of 0.5,5 (O.27-O.81) gm./l.

Po-tassiuni concentrations in cows’ fllilk

(geo-metric itiean values) were about to 4 times

greater than the concentrations measured in our human milk safllples. Spector7 reports

potassium levels in cows’ milk of 1.38

(0.38-p2.87) gm/I which compare favorably with

OU values of 1.42 (1.38 to 1.46) gm/I.

The concentrations of cesium-137 in the

human milk samples were very small and did

not exceed f20 pc/I, and in most cases were close to the minimum detectable amount for this ra(lionucli(le under the conditions of

nleasurement. Cesium-137 concent rat ions in

cOvs’ milk were also small, 5 to 5 pc/l,

(luring this period.

Information on tile (liscrimination of

strontium-90 in relation to calcium by

mothers consuming cows’ milk was

oh-taine(1 from the Chicago data (Table I).

Based on the assumption that the sole

soul.(e of calcium consumed by tile donors

was cows’ milk (not necessarily a valid

assumption, since the donors may have

re-ceive(l calcium from other sources), the

Observed Ratio* was found to average

(#{241}g7g) 0.39.0 With a range for the

eight values of 0.18 to 0.89. Similarly, the Observed Ratio for the discrifllinlLtiOn of

cesium-137 in relation to potassium was

calculated aIl(I found to be 1.0 and 0.81 for

March and April, 1961 , respectively. These

values have little significance since the

cesium-137 values were very low.

The data reported in this study show that in the metabolism of cows’ milk and

j)r0-(luction of hunian nlilk, the mother

(liscrimi-nates in favor of calcium over strontium

by a factor of approximately .5 which

ac-counts for the lower levels of both

radio-StFOfltiUIfl and stable calcium. Actually, in

terms of the strontium-90 and calcium

con-cent rations, the differences between human and cows’ milk were equivalent to a factor of about 11 and 4.5, respectively. Since

* Observed Ratio,

“#{176}Srh/Cah “7Csh/Kl,

OR. = “#{176}Sr,/Ca, and

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ARTICLES 735

stront iuin-90 concentrat ions in hu IIan mi 1k are smaller than those in cows milk by an

order of magnitude, the consumption of

human milk should result in a lower intake of

this radionuclide by infants, which should

reduce potential ra(hation exposu re, tinless

there is a difference in inetabolisni of the

two sources of milk.

REFERENCES

1. Radiological Heaith Data, Monthly Publication, Division of Radiological Health, Public

Health Service, U. S. Department of health,

Education, and Welfare, Washington 25, D.C.

2. Brown, J. R., and Jarvis, A. A. Strontium-90

levels in human milk. A nine-months survey in Toronto. Canad. J. Pub. Health, 52:463,

1961.

3. Lough, S. A., Hamada, G. H., and Comar, C.

L. Secretion of dietary strontium-90 and

calcium in human milk. Proc., Soc. Exp.

Biol. Med., 104:194, 1960.

4. Aarkrog, A. Caesium-137 from fall-out in

hu-man milk. Nature, 197(4868):667, 1963. 5. Jarvis, A. A., Brown, J. R., TiefenLach, B.

Strontium-89 and strontium-90 in breast

milk and in mineral-supplement preparations.

Canad. Med. Ass. J., 88:136, 1963.

6. Campbell, J. E., Murthy, C. K., Lewis, K. H.,

and Straub, C. P. Radionuclides in miTk. In Radioactive Fallout, Soils, Plants, Foods,

Man, E. B. Fowler (Ed). Amsterdam,

Lon-don, New York: Eisevier Publishing Co.,

(1965), pp. 156-179.

7. Spector, W. S. (Ed.), Handbook of Biological

Data, p. 50, Philadelphia: \V. B. Saunders,

Co., 1956.

Acknowledgment

The writers wish to express their appreciation to Drs. L. Gerber and N. C. Telles, who made ar-rangements for the Denver and Chicago samples, respectively; to Messrs. S. Cox and U. Rhea for some of the chemical analyses; and to Mr. B. M.

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1965;36;732

Pediatrics

Conrad P. Straub and Gopala K. Murthy

COMPONENT OF HUMAN AND COWS' MILK

90

A COMPARISON OF SR

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1965;36;732

Pediatrics

Conrad P. Straub and Gopala K. Murthy

COMPONENT OF HUMAN AND COWS' MILK

90

A COMPARISON OF SR

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