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HEALTH AND SAFETY RESEARCH DIVISION

RADIUM-226 IN DRINKING WATER AND TERRESTRIAL FOOD CHAINS:A REVIEW OF PARAMETERS AND AN ESTIMATE OF

POTENTIAL EXPOSURE AND DOSE

A. P. Watson, E. L. Etnier, and L. M. McDowell-Boyer

Date Published: April 1983

NOTICE This document contains information of a preliminary nature.It is subject to revision or correction and therefore does not represent afinal report.

Prepared for theFLORIDA INSTITUTE OF PHOSPHATE RESEARCH

under Interagency Agreement DFP#81002/DOEERD-81-163

OAK RIDGE NATIONAL LABORATORYOak Ridge, Tennessee 37830

operated byUNION CARBIDE CORPORATION

for theU. S. DEPARTMENT OF ENERGY

iii

V

SUMMARY

Environmental transport of 226Ra from geological formations to

drinking water and from soil to vegetation, meat and milk were quantita-

tively analyzed following a review of literature. Both natural and

industrial sources were investigated. Particular attention was given to

references specific for the phosphate-mining region of southwestern

Florida.

Literature sources have been interpreted to develop concentration

factors describing terrestrial food-chain transport. Unweighted means

and associated ranges of concentration factor values, representing

averages of data collected over a variety of environmental conditions,

soil types, and chemical forms, are also provided. Annual human exposure

and 50-year dose commitments to bone, lung, liver, kidney and whole body

were estimated by assuming mean concentration factors as well as annual

food and water consumption rates.

vii

1. INTRODUCTION

Radium-226 is a long-lived daughter (tl/2 = 1620 y) of the 238U

decay series. As such, 226Ra occurs with the parent uranium isotope

as a trace constituent in the minerals of granites and metamorphic

rocks, unweathered sediments derived from these rocks, and as a contem-

poraneous sedimentary deposit in phosphate mineralizations (Michel and

Moore, 1980; USEPA, 1978). The source of 238U in phosphate-bearing

rocks is considered to be redeposition of uranium dissolved in the

waters of ancient oceans from which the phosphate mineralization was

derived (Osburn, 1965; Guimond, 1976). It is to be expected that

vegetation irrigated by, and drinking water originating from, water

supplies in contact with any of these primordial deposits may contain

elevated concentrations of 226Ra. However, long-range transport of

226 Ra can also occur via weathering and leaching of parent material

(Michel and Moore, 1980). Additional variability in the 226Ra content

of waters is due to the geochemistry of the element uranium, which may

be adsorbed to clays, reduced by iron or organic matter, and scavenged

by iron precipitation (Michel and Moore, 1980).

The current evaluation focused on information pertinent to phosphate

mining regions of the United States, with particular emphasis on the

Central Pebble District of western Florida. Considerable interest has

been displayed in evaluating the most probable routes of radiation

exposure that may result as a consequence of proposed phosphate mine

expansion. A major concern is the magnitude of potential ingestion

dose due to local consumption of food grown near, or water receiving

2

effluent from, phosphate mines or reclamation sites. To characterize

such transfer and estimate potential dose, an evaluation of pertinent

food chain parameters governing exposure was performed.

2. RADIUM-226 IN POTABLE WATERS

2.1 DOMESTIC OCCURRENCE

The quantity of 226Ra found in water supplies is directly determined

by the geology of the surface water drainage system or underground

aquifer supplying the consumer(s). In general, it is thought that

waters from shallow wells usually contain less 226Ra than that from

deeply drilled wells, with wells bored into granitic and deep sandstone

formations containing the highest concentrations (Smith et al., 1961;

Snihs, 1973; Brinck, et al., 1976). Hot springs, wells, or boreholes in

geothermal areas often contain elevated amounts of 226Ra and other

members of the 238 U decay series as a result of reservoir proximity to

the earth's mantle. Studies to date demonstrate that 226Ra in municipal

water supplies at the point of use is considerably lower than that found

in raw groundwater due to the purification regime at the treatment

plant; oxidation and filtration, reverse osmosis, sodium cation exchange,

and lime-soda ash softening are particularly effective and generally

remove 50 to 90% of the 226Ra present in untreated waters (Kiefer,

Wicke, and Glaum, 1980; Asikainen and Kahlos, 1980; Brinck et al.,

1976).

3

A number of municipal and private drinking water sources have been

sampled for 226Ra throughout the United States as well as in the Florida

Pebble Districts. The results of several surveys, presented in Tables 1

and 2, are by no means exhaustive. Nevertheless, these data illustrate

the large range of 226Ra concentrations measured in domestic drinking

waters available from wells, surface waters, springs, and as commercial

bottled water.

The groundwater system of central Florida is composed of two

aquifers separated by a central matrix unit of clay, sand, and phosphate

rock. The shallow water table aquifer is made up of springs, wetlands,

lakes, streams, and surface runoff; it is located above the central unit

and is unconfined (USEPA, 1978). The central matrix not only contains

the commercial phosphate ores of the region (i.e., the Bone Valley

formation), but also serves as an aquiclude preventing upward movement

of the underlying Floridan aquifer (USEPA, 1978). Since the upper

reaches of the Floridan aquifer are in closest contact with the phosphate

mineralization, these waters should contain higher concentrations of

226Ra than the deeper portions of the aquifer. Such appears to be the

case, as verified by the sample results of Kaufman and Bliss (1977) for

the Upper and Lower Floridan Aquifer (Table 2).

Several conclusions may be drawn from evaluation of the data

presented in Tables 1 and 2:

(1) Very few studies have correlated their results with the

phosphate-bearing status of the aquifer being sampled

(i.e., unmineralized vs. mineralized and unmined or

mined). Thus, only the findings of Kaufman and Bliss

4

Table 2. Radium-226 in public and private supplies of potable water in Florida

Source of drinking water Activity (pCi/L)

Average Range Distribution Reference

Municipal wells

Central Florida

Arcadia Auburndale Avon Park Bartow Bowling Green Clermont Dade City Dundee Haines City Lake Alfred Lakeland Lake Wales Wedula Rec. Center Mulberry Plant City Hinter Haven Zephyr Hills

Drilled wells

Central Florida (1=105)

Private wells

Central Florida (Y=OO)

Surface waters

Central Florida Apalachicola River

110 km upstream from mouth Suwanee River

38 km upstream from mouth

0.06

0.95

2.5-3.3 0.50-0.53 0.98 1.4-1.6 2.7 0.29-0.39 0 0 0.73-0.74 1.8-4.1 0.80-0.84 0.47-0.76 0.23 0.45 0.0-0.77 0.58-0.67 0.31

~4.6~ 9oxa c2.4 75% Cl.2 50% co.5 25% O-O-76 100%

q4.6 c3.9 Cl.4 q0.5 0.0-76

90% Irwin and Hutchinson, 1976 75% Irwin and Yutchinson, 1976 50% Irwin and Hutchinson, I976 25% Irwin and Yutchinson, 1976

100% Irwin and Hutchinson, 1976

Irwin and Hutchinson. 1976 Irwin and Yutchinson; 1976 Irwin and Hutchinson. 1976 Irwin and Yutchinson, 1976 Irwin and Hutchinson, 1976 Irwin and Yutchinson, 1975 Irwin and Hutchinson, 1976 Irwin and Yutchinson, 1975 Irwin and Yutchinson, 1976 Irwin and Yutchinson, 1975 Irwin and Hutchinson, 1976 Irwin and Yutchinson, 1975 Irwin and Yutchinson, lQ?fi Irwin and Yutchinson, 1976 Irwin and Hutchinson, 1975 Irwin and Yutchinson, 1975 Irwin and Yutchinson, 1976

Irwin and Yutchinson, 1976 Irwin and Wtchlnson, 1975 Irwin and Yutchinson, 1976 Irwin and Hutchinson, 1976 Irwin and Yutchinson, 1976

Fanning, nreland, and Rryne, I982

Fanning, et-eland, and Rryne, 19X2

ln

(1977) permit a comparison of the effects of phosphate

mining on 226Ra in groundwater (Table 2). The surface

water effects of potential discharge from a phosphate

fertilizer plant may be partly considered from the sample

survey performed by Strain, Watson, and Fong (1979) in

eastern North Carolina (Table 1). Downstream concentra-

tions of 226Ra were roughly twice that of upstream;

however, the maximum was still less than 0.5 pCi/L.

(2) Available data indicate that phosphate mining does not

significantly alter the 226Ra content of the Floridan

aquifer (Kaufman and Bliss, 1977). However, surface

water in mined areas contains 226 Ra in quantities approxi-

mately three times that of surface water in unmined areas

(i.e., 0.55 vs. 0.17 pCi/L).

_(3) The 226Ra content of the upper Floridan aquifer in

unmineralized regions of central Florida (X = 5.1 pCi/L)

may exceed that of the same aquifer in phosphate-bearing

regions. This value is slightly greater than EPA's cur-

rent National Interim Primary Drinking Water Regulations,

which limit the combined 226Ra and 228Ra content of potable

waters to 5 pCi/L (Mills, Ellett, and Sullivan, 1980).

(4) Excepting the mean value noted in (3) above, the 226Ra

content of all municipal, drilled and private wells, and

surface waters in central Florida is comparable to that

found in many other regions of the U.S. that do not possess

phosphate deposits (Tables 1 and 2). The highest values

8

identified in this summary were geothermal wells in both

California (1500 pCi/L) and Utah (300 pCi/L), mineral

springs in New York (430 Ci/L), and shallow wells in

eastern North Carolina (150 pCi/L).

2.2 ESTIMATED INGESTION EXPOSURE AND DOSE

Human adults are assumed to ingest between 1 and 2 L of water

each day in the form of drinking water, beverages, and cooking water

(Fletcher and Dotson, 1971; USNRC, 1977). For the present assessment,

the upper level assumption of 2 L/day, or 730 L/y, was chosen. Annual

drinking water exposure to 226Ra was estimated from the concentrations

summarized in Tables 1 and 2 for central Florida as well as example

U.S. regions. The resulting exposures were converted to 50-year dose

commitments to target organs upon multiplying annual intake by current

ingestion dose commitment factors for 226Ra (Dunning et al., 1979).

Exposure and dose estimates are presented in Table 3.

3. UPTAKE OF RADIUM-226 BY EDIBLE CROPS

3.1 SOURCES

The relative importance of soil and air as sources of 226Ra in

edible crops will depend on the conditions of environmental contamina-

tion and the types of crops considered. For naturally occurring 226Ra,

it seems likely that uptake by roots and translocation to edible por-

tions of the plant is the primary contamination pathway, with resuspen-

sion being the largest aerosol source. However, in areas directly

Table 3. Estimated exposure and 50-year dose commitment for one year's exposure to radium-226 in drinkino water

Estimated dose (rem) Source of drinking water Annual exposure

(uCi) Bone Lung Liver Kidnev Ihole hodv

Central Florida

Municipal wells (range)

Drilled and private wells (range)

(90% of total sampled)

0 - 3E-3 0 - 1.3E-1

0 - 5.5E-2 0 - Z.iE+O 3.4E-3 1.5E-1

0 - 1,5E-3

0 - 3,OE-2 ?.OE-3

0 - 1.8E-3

0 - 3.m?-2 ?.!lE-3

n - 1.957

') - 3.V-? 2.v-7

n - l.l-lE-2

n- l.QF-1 l.nc-?

Surface waters (range) (mean)

Unnineralized

Upper Floridan (mean) Lower Floridan (mean)

Mineralized, unmined

Surface water (mean) Upper Floridan (mean) Lower Floridan (mean)

Mineralized, mined

Surface water (mean) Upper Floridan (mean) Lower Floridan (mean)

United States

1.5E-1 - 1.5E+O 2.OE-3 - 2.OE-2 2.OE-3 - 2.X-2 2.1-E-3 - ','.'-I?-" 5.1E-4 - 5.1F--J 3.OE-2 4.OE-4 4.OF-4 A.W-A ?.Y-7

1.5E-4 - 1.5E-3 6.7E-4

3.7E-3 1.6E-1 2.2E-3 3.2E-3 2.X-7 l.T-7 l.OE-3 4.OE-2 6.X-4 6.OC-4 ci.W-4 ?.AF-7

1.2E-4 l.OE-2 : 7.2E-5 7.X-5 7.?F-5 4.1~4 1.7E-3 7.OE-2 l.DE-3 l.DE-3 l.‘)F-7 I.57 1.5E-3 6.DE-2 9.OE-4 9.OE-4 9.nE-4 l.nE-3

4.OE-4 Z.OE-2 2.4E-4 2,4E-4 ?,4F-4 l.AF-2 1.2E-3 5.OE-2 7.2E-4 7.?F-4 7.y-4 4.lC-3 1.4E-3 6.9E-2 8.4E-4 S.4E-4 9.4E-4 A,F-7

klunicipal wells (range)

Other public water supplies (range)

Geothermal wells/springs

6.6E-5 - l.OE-2

2.9E-5 - 2.6E-2

7.3E-6 - l.OE+O

2.8E-3 - 4.3E-1 4.OE-5 - 6.nE-2 4.w5 - km-2 4.nE-5 - 6.w? ?,?E-4 - 7,nF-2

1.2E-3 - l.lE+O 1.7E-5 - 2.DE-2 1.7E-5 - 2.w2 1.7E-5 - 7.E-? Q.9F-5 - 9,4?-3

3.3E-4 - 4.3E+l 4.5E-6 - 6.OE-1 4.5E-6 - r;.'-F-1 4.5E-6 - e.nr-1 7.r;=-5 - 7,aF+n

10

downwind of anthropogenic 226 Ra sources, aerosol deposition may become

the most significant source of 226 Ra in edible crops, especially in

leafy vegetables or forage crops.

The uptake of 226Ra from soil by plant roots is influenced by

soil type, as well as by factors such as soil pH, content of other

alkaline-earth elements in the soil, clay content, exchangeable calcium

and potassium, plant species, and chemical form of 226Ra in soil

(Grzybowska, 1974; Garner, 1971; Rusanova, 1964; Verkhovskaja, Vavilov,

and Maslov, 1966; Kirchmann, Boulenger, and LaFontaine, 1968; Nishita,

Wallace, and Romney, 1978). Numerous studies have been performed to

investigate the behavior of 226Ra in the soil-plant system and its

incorporation into plant tissues from nutrient solutions. However,

experiments quantifying uptake from nutrient solutions are less useful

for our purposes, since retention of 226Ra by soil particles and its

interaction with soil components are important properties in determining

transfer efficiencies (Grzybowska, 1974; Garner, 1971; Verkhovskaja,

Vavilov, and Maslov, 1966; Rusanova, 1964; Taskayev et al., 1977).

The mobility of 226Ra within plant tissues appears to be high during

transport from root to shoot, but low after deposition within leaf

tissues, resulting in an acropetal concentration gradient. A potential

for uptake by animals feeding

(Taskayev et al., 1977; Vavilo

of translocation to other non

been well documented.

on forage or leafy vegetables exists

v, Popova, and Kodaneva, 1964). Dynamics

leafy edible portions of plants has not

11

3.2 CONCENTRATION FACTORS

Transfer to edible portions of vegetation may be characterized by

the soil-plant concentration factor (CFsp), the unitless ratio of fresh

weight specific activity in plants to dry weight specific activity in

soil at harvest or equilibrium.

Since naturally occurring 226Ra originates in soil, the question of

direct foliar uptake has generally been neglected in studies of radium

translocation in agricultural crops. It is known that 17 to 79% of

total radium activity measured in air-cleaned samples of native grasses

and shrubs collected near inactive uranium mill sites in New Mexico is

due to surficial contamination (Marple, 1980). Thus is is reasonable to

assume that deposition of 226Ra-containing aerosols or resuspended soils

containing 226Ra could be an important consideration for some crops in

certain areas. Therefore, the CFsp's describing soil-plant transfer and

presented here may overestimate the actual ratio if deposition of aerosol

radium was a significant source of total plant radium at a given study

site.

We have chosen to provide estimates of unweighted averages and

ranges of CF's as calculated from existing literature available for

edible crops. These are presented for vegetables, fruit, grain, forage,

feed, and hay (Table 4). In all likelihood, CF's are lognormally distri-

buted (Ng, 1982), and a geometric mean of the measured values would be

the most accurate estimate. Nevertheless, the arithmetic average will

be the most conservative value.

Table 4. Concentration factors representing soil-to-plant transfer of **'Ra (CFsp)'*b

Edible plant portion Mean concentratEon Number of

factors (CF ) derived Range

(*lo-2)sp (x10-q Reference

values

Vegetables (fresh weight)

Beet Cabbage

Carrot Potato

Unspecifiedd

Unweighted average

Fruit (fresh weight)

Orange Grapefruit Unspecifiede

Unweighted average

Grain (fresh weight)

Barley Buckwheat Millet Peanuts Rice Wheat

3.7 2 1.4-6.0 130

Kirchmann, Boulenger, and LaFontaine, 1968 130 Mordberg et al., 1976

40 : Mordberg et al., 1976 4.1 3 29.5 EERF, personal communication

100 24 48-175 Adriano, McLeod, and Ciravnlo, 1981 100 1 100 Mordberg et al., 1976

Unweighted average

Forage, hay (dry weight)

63 ‘32 1.4-178

_A _ , . 1 . , .‘

Ng;;a hay 7.0 24 1.0-34 Grzybowska, 1974 21 6 1.1-48 Kirchmann, Boulenger, and LaFontaine, 1968;

Taskayev et al., 1977; Rusanova, 1964 Fescue 2.8 2.8 Taskayev et al., 1977 Grass indian ricegrass

13 2; 2.0-63 Grzybowska, 1974, 1.5 1 1.5 Rajno, Momenf, and Sabau. 1980

Mixed grasses 17 :47

3.5-28 Ibrahim, Flot, and Whicker, 1982 Rye grass 24 2.0-62 Kirchmann, Boulenger, and LaFontaine, 1968;

Taskayev et al., 1977 Timothy hay 1 Wetch hay 1 ::;’

Taskayev et al., 1977 Taskayev et al., 1977

Unweighted average 10.0 103 1.0-63

aAerosol radium-226 was assumed to contribute‘insigniticant amounts of radium-226 to the plant. b Table adapted from McDowell-Boyer, Watson, and Travis, 1980.

>,

::6” 5 2 <O.!ll-4.0 0.6-3.0

i:: 2 3 0.07-13.6 1.0-3.0

0.1 1 0.1

1.2 13 CO.Ol-4.0

E 4 0.3-1.1 a:05 1 0.2

1 0.05 ,, .

0.3 6 0.05-1.1

Kirchmann, Boulenger, and LaFontaine, 1968 Kirchmann, Boulenger, and LaFootaine, 196R; Vavilov, Popova, and Kodaneva, 1964 Kirchmann. Boulenger, and LaFontaine, 1968 Kirchmann, Boulenger, and LaFontaine. 1968 Vavilov, Popova, and Kodaneva, 1964 DeBortoli and Gaglione, 1972

EERF, personal ccmmunication EEQF, personal communication 9eBortoTi and,Gaglione, 1972

'Values express ratios of fresh-weight radium-226 concentrations in plants to dry-weight concentrations in soil for all food crops directly edible by man. Dry-weight concentrations in both plants and soil were used for forage, hay, and feed calculations.

d Sample consisted of tomatoes, beans, lettuce and small pumpkins in equal amounts.

eSample consisted of peaches, pears, apples, plums, and grapes in equal amounts,

12

13

The CFsp

's are given in dry weight concentrations for forage, hay

and feed; and in fresh weight concentrations for vegetables, fruits

and grains (i.e., moisture content as normally consumed). When neces-

sary, conversion of literature data to fresh or dry weight was made

with the use of information supplied in the text of each paper cited

or by standard conversions documented in Spector (1956). Both the

unweighted arithmetic average of mean CFsp

's and range of individual

values are given for each food category. The ranges indicate that

much uncertainty is involved in determining a single value for CF;

much of this uncertainty is probably due to the variability in experi-

mental, conditions among the studies cited as well as the wide range of

soil, climatic, and nutritional conditions evaluated.

Values presented in Table 4 indicate that grains tend to concentrate

226Ra when compared to vegetables and fruit. The actual fraction of

total grain 226Ra present in the hull versus that present within the

kernel is not known; most of the available studies do not mention

whether analyses were performed on whole or de-hulled grain. The one

study that described grain processing stated that "no attempt was made

to dehull" (Adriano, McLeod and Ciravolo, 1981). This is probably

true for the majority of grain analyses. A single CF value availablespfor flour equals 0.5 (DeBortoli and Gaglione, 1972), which further

supports the assumption that the values in Table 4 are for whole grain.

The unweighted mean CFsp for 226 Ra transfer to grain is 0.63.

The averages for fruit CFsp 's are based on a very small number of

samples, most of which originated in a limited field study performed

for the U. S. Environmental Protection Agency (EPA) by staff of the

14

Eastern Environmental Radiation Facility (EERF, 1978, personal communi-

cation) at various study sites in southwestern Florida. An estimate

of dietary exposure and dose from potential consumption of oranges and

grapefruit sampled in the EERF study will be included in Sect. 5.2.

The results of the current review suggest that the unweighted mean

CFsp for 226Ra transfer to fruits (3.0 x 10-3) is reasonable for assess-

ment purposes.

For forage and hay, an average dry weight CF of 1.0 x 10-1sp

was

estimated. The value for forage, hay, and feed expressed in dry weight

is most useful since herbivore ingestion studies seldom consider fresh

weights. Observation of the wide range of values of CFsp's derived

from the literature suggests that experimental conditions can greatly

influence the value calculated for a particular forage species. Only

one forage study, cited in Table 4, involved vegetation grown in

naturally contaminated environments (Rusanova, 1964).

From this review, specific values of CF sp for soil to plant transfer

of 226Ra are recommended for use in environmental transport assessments

where the food category is known (i.e., fruit, grain, etc.). A previously

recommended generic value for this parameter, labeled Biv by the U. S.

Nuclear Regulatory Commission in its Regulatory Guide 1.109 (USNRC,

1977), is 3.1 x 10-4. This generic estimate does not distinguish

between forage or other crops but is useful as a default value., Ng

(1982) recommended separate values for different commodities and pointed

out the extreme variability in values available for soil-plant CF

estimates (i.e., range extends from 10-5 to 10-l).

15

4. RADIUM-226 IN MEAT AND MILK

The most common pathways by which 226Ra may be potentially trans-

ferred to milk and animal muscle used for human consumption are via

(1) fugitive dust deposition onto surfaces of forage plants, and (2) root

uptake from soils and eventual translocation to plant parts consumed

as forage or feed supplements. The transfer of any element from feed

to meat or milk by these means can be predicted with the use of various

parameters derived from experimental feeding studies or field measure-

ments. The concentration factor (CF) parameter is one, and is defined

as an expression of the equilibrium concentration of the element in

milk or meat as a fraction of the chronically ingested concentration

in feed. Specifically, CFm is the unitless ratio of activity concentra-

tion in milk (fresh weight) to the activity concentration in the dairy

animal's diet (dry weight); CFf represents the same ratio for meat

(beef in our analysis). As stated in Sect. 3.2, CF's are probably

lognormally distributed. However, only the conservative arithmetic

mean will be derived in the present analysis.

The number of sources documenting trophic transfer of 226Ra from

feed to animal products is small. Despite the availability of numerous

publications presenting the 226Ra content of milk and meat products

from market basket surveys (Morse and Welford, 1971; Fisenne and Keller,

1970; Hallden, Fisenne, and Harley, 1963; Hallden and Harley, 1964;

Muth et al., 1960; Wu and Weng, 1977), most of the literature does not

contain the necessary information on 226Ra concentration in the feed

of livestock from which the products were obtained. As a result, many

16

available sources were considered inadequate for

present analysis.

inclusion in the

4.1 DISTRIBUTION IN MILK

A few attempts have been made to measure the concentration of

radium isotopes in milk resulting from their ingestion by dairy cattle

(Table 5). A biological half-time of 50 hours for radium elimination

via milk has been estimated from monitoring data on two dairy cows

exposed to single oral administrations of 5 mCi 224Ra (Sansom, Garner,

and West, 1966). It may be estimated that 93% of the total 224Ra

elimination via milk (0.35% of the total administered 224Ra) occurred

during the eight days following acute administration. At that time,

sampling was discontinued. The major fate of ingested 224Ra was fecal

excretion (99%). The average diet-to-milk CFm is estimated to equal

3.7 x 10-3 (range of 3.1 to 4.4 x 10-3 reported by Sansom, Garner, and

West, 1966) in Table 5, although the isotope was not technically

administered in feed.

Kirchmann and his colleagues consider forage ingestion to be a

major source of radium excreted in milk (Kirchmann et al., 1972).

Analysis of data obtained by these investigators from individual animals

exposed to either drinking water containing 226RaC12 or hay harvested

from industrially contaminated pastures indicates that forage only

slightly exceeds drinking water as a source of radium in milk. Similar

results have been observed for another alkaline-earth element, 85Sr

(Van den Hoek et al., 1969). Equilibrium estimates of CFm from the

hay ingestion experiment are also presented in Table 5.

Table 5. Concentration factors (CF,,,)a for 226 Ra ingested by dairy animals

and transferred to milk

Radium source

Vean CFm

milk; diet

(x1o-3)

Number of derived values

Reference

Oral administration of 5 mci'radium-224; Britain 3.7 2 Sansom, Garner and blest, 1966

Radium from industrial emissions incorporated into forage; Belgium 8.4 4 Kirchmann et al., 1972

Natural radium-226 in native upland meadows; central Yugoslavia 14.0 7 MiloS'evii et al., 1980

Dairy farms on or adjacent to reclaimed phosphate land, Polk County, Florida 0.71 1 EERF, 1978 (personal

0.79 2 communication)

Unweighted avg. CFm 5.5

aCF defined as equilibrium ratio of specific activity in milk (fresh wt) to specific activity"in diet (dry wt).

18

Milosevic and his colleagues (1980) report the distribution of

226Ra in the milk of cattle grazing the upland pastures of central

Yugoslavia, a nonindustrialized region devoted to cattle breeding and

dairy production. According to the authors, none of the locations

sampled had ever been cultivated or planted; cattle ingested native

grasses. A mean CFm calculated from data for seven sites is 0.014

(Table 5). The 226Ra compound being evaluated was not identified.

A preliminary assessment of 226Ra in foodstuffs associated with

reclaimed phosphate lands and background sites in Polk County and

adjacent counties in Florida has been released as a personal communi-

cation by the Eastern Environmental Radiation Facility (1978) of

Montgomery, Alabama. The milk from two dairy farms as well as the

grass and feed supplements ingested by the test animals, were sampled.

Estimates of CFm derived from the feeding rates and specific activities

provided in the report are presented in Table 5.

The unweighted mean value of CFm derived from these four studies

(5.5 x 10-3) compares well with the value of 4.0 x 10-3 derived from

the 226Ra transfer coefficient estimated by McDowell-Boyer, Watson,

and Travis (1980) and recommended by Ng (1982). The unweighted average

listed in Table 5 may be used to reasonably estimate the degree of

226Ra transfer to milk from forage, provided the specific activity of

the forage is known.

Existing data for naturally occurring 226Ra in milk supplies is

presented in Table 6. The majority of samples contain less than

0.3 pCi/kg, with only a few approximating 1 pCi/kg. The U.S. and

Table 6. Measured values of naturally occurring radium-226 in dietary meat and milk (pCi/kg fresh weight)

Site

: . . .._ ., . z 1 ",, . _, ,j .~ , Milka,b '-- ".Meata _ "'.' '

(pCi/kg) (pCi/kg) References

---

United States

New York State Wisconsin Tennessee Chicago

New York City

New York City

New York City San Francisco

0.13 0.24 0.27 0.23

(0.24-0.25) 0.09

(0.08-0.10) San Francisco

Germany 0.3

Yuqoslavia 0.88 (N = 7)

(0.06-2.30)

United Kingdom 0.10 (N = 6)

Yl%**) 0:10 0.18 1.07 0.22

Italy

Varese, N. Italy 0.18 (N = 2 to 4) (0.175-0.185)

Throughout Italy 0.26 (N = 15) (0.08-0.50)

Taiwan 0.15 (0.10-0.20)

Puerto Rico -- 0.15 0.08

Unweighted mean, U.S. 0.22 0.22

Range (0.09-0.27) (O-0.55)

Unweighted eean, all sites 0.27 0.44

Range (0,09-1.07) O-l.6

0

0.01 0.46

Shandley, 1953 Shandley, 1953 Shandley, 1953 Hallden and Fisenne, 1961

Hallden and Fisenne, 1961

Fisennc and Keller, 1970

Fisenne and Keller, 1970 Morse and Welford, 1971 Hallden and Fisenne, 1961 Fisenne and Keller, 1970

Muth et al., 1960

MiloZeviS et al., 1980

Smith and Watson, 1963

Smith and Watson, 1963 Smith and Watson, 1963 Smith and Watson, 1963 Smith and Watson, 1963 Smith and Watson, 1963

DeBortoli and Gaglione, 1972

Mastinu and Santaroni, 1980

Wu and Weng, 1977

Hallden and Harley, 1964 Hallden and Harley, 1964

aValues in parentheses are range and/or number of samples (Y). b

Based on milk density of 1.028 g/cm3, R. C. Weast, 1976, page F-3).

19

20

global means derived from these literature values are very similar,

i.e., 0.22 and 0.27 pCi/kg, respectively.

The average 226Ra content of three milk samples collected from

two dairies on or adjacent to reclaimed phosphate lands in Polk County,

Florida, was 2.51 pCi/kg (range of 1.43 to 3.85 pCi/kg) (EERF, 1978,

personal communication), or approximately 1 order of magnitude greater

than the U.S. and global means presented in Table 6. Milk samples

were not collected from reference areas on unmined or nonphosphate

lands, so no comparison with normal background levels in the same

region can be made. If it is assumed that the average adult milk

consumption is 110 kg/y (USNRC, 1977) and that the target adult would

exclusively consume milk of the same specific activity as the two

Florida dairies sampled, then the average annual exposure from milk

consumption would be 276 pCi. Using the dose conversion factors of

Dunning et al. (1979), this exposure would translate into a 50-year

dose commitment factor for bone, lung, liver, kidney, and whole body

of 1.2 x 10-2, 1.7 x 10-4, 1.7 x 10-4, 1.7 x 10-4, and 9.4 x 10-4 rem,

respectively. Those individuals ingesting milk of 226Ra specific

activities equal to the U.S. or global mean presented in Table 6 would

receive estimated doses of approximately 1 order of magnitude lower

than those derived above.

4.2 DISTRIBUTION IN MEAT

Holtzman and his colleagues have recently examined human food

chain samples collected from rangeland areas surrounding tailings

piles created by milling and processing uranium ore (Holtzman et al.,

21

1979). Radium-226 concentrations in the stomach contents and muscle

of two cattle grazing in a reference area located 20 km from uranium

tailings piles were used to derive the average CFf of 6.5 x 10-3

presented in Table 7. The mean value for cattle grazing in the unpol-

luted mountain meadows of central Yugoslavia was derived from the

previously described study by Milosevic et al. (1980).

Data collected from caribou and reindeer populations have been

included in the assessment of forage-to-meat transfer for two reasons:

(1) the paucity of information regarding cattle ingestion of 226Ra,

and (2) caribou, reindeer, and cattle all possess similar digestive

systems (i.e., they are all ruminants). Most of the pertinent caribou

and reindeer information addresses incidental radionuclide uptake via

grazing on Cladonia lichens in Alaska and Finland (Holtzman, 1966a, b).

Due to their slow growth habit and large surface-to-volume ratio,

lichens accumulate dust particles containing significant quantities of

the naturally occurring isotope 226Ra, Because data characterizing

the radium concentration of rumen contents was unavailable, an alternate

method of estimating the concentration factor to these ruminants (CFr)

was developed. Although it is known that caribou and reindeer freely

ingest annual grasses, sedges, and horsetails during the short Arctic

summer, the present calculation conservatively assumes lichen ingestion

as the principal source of forage. Annual mean values of lichen 226Ra

activity in Alaska and Finland were used to compute the caribou CFr of

4.7 x 10-3 and the reindeer CFr of 8.6 x l0-3 (Table 7) (Holtzman,

1966a, b). It must be noted that Holtzman's data represent a special

case.

Table 7. Concentration factors (CF, and CFf) for radium-226 ingested by cattle and other

ruminants and transferred to meat

Animal Radium source Mean CFf, CFra No. of

( x1o-3) derived Reference values

Cattle Uncontaminated pasture; 7.4 5 MiloS'evic' et al., 1980 central Yugoslavia

Cattle Reference area 20 km 6.5 2 Haltzman et al., 1979 from uranium ore tailings piles; range- land in New Mexico

Other ruminants

Caribou Lichens contaminated with naturally occurring radium-226

Reindeer Lichens contaminated with naturally occurring radium-226

Mean for ruminants other than cattle

4.7 12 Holtzman, 1966a, b

8.6

6.7

Mean for all ruminants 6.8

1 Holtzman, 1966a, b

aCFr is concentration factor for ruminants; CF is defined as equilibrium ratio of activity in meat

(fresh wt) to specific activity in diet (dry wt).

23

Radium-226 is a known bone-seeker due to its metabolic similarity

to calcium; the greatest body burden of an animal ingesting 226Ra would

be in the skeleton (Hardy et al., 1969). Thus, the human populations

potentially exposed to the highest concentrations in animal tissue

would be those who ingest significant quantities of bone meal. The

transfer of 226Ra from bone to soup broth or bouillon is unknown; it

is known that such transfer for the daughter products 210Pb and 2l0Po

can be equal to a maximum of 1.0% and 13.8%, respectively (Milosevic

et al., 1980).

The average transfer value estimated for all ruminants (CFf =

6.8 x 10-3; Table 7) is in close agreement with the value of 5.1 x 10-3

previously recommended by (McDowell-Boyer, Watson, and Travis, 1979;

Ng, 1982).

Although no measurements of 226Ra uptake in beef were made in the

previously described Polk County study (EERF, 1978, personal communi-

cation), an estimate of beef specific activity (26.5 pCi/kg) was made

from the mean CFf above and the measured values of226Ra in grass

ingested by dairy cattle. If it is assumed that all beef consumed has

been produced by animal s ingesting grass of the same activity measured

by the EERF, and that every adult consumes the average quantities of

beef estimated by the U.S. Department of Agriculture (32 kg/y) (USDA,

1977), then the average adult exposure would equal 848.2 pCi. Again

using the conversion factors of Dunning et al. (1979), this exposure

translates to an individual 50-year dose commitment factor for bone,

lung, liver, kidney, and whole body of 3.6 x l0-2, 5.0 x 10-4,

5.0 x 10-4, 5.0 x 10-4, and 2.9 x 10-3 rem, respectively. Similar

24

exposure to the average U.S. beef specific activity of 0.22 pCi/kg

226Ra (Table 6) would result in exposure and dose approximately 2 orders

of magnitude lower than that estimated above.

5. TOTAL DIETARY INTAKE OF RADIUM-226

5.1 CONSUMPTION OF FOODSTUFFS

Several investigators have attempted to estimate daily intake of

226 Ra from total diet samples containing naturally occurring radium

(Morse and Welford, 1971; Fisenne and Keller, 1970). Other investi-

gators have reported 226Ra in a limited number of food items and esti-

mated intake for a diet composed of those items alone (Mastinu and

Santaroni, 1980; Lalit and Ramachandan, 1980; DeBortoli and Gaglione,

1972; Oakes et al., 1977; and EERF, 1978, personal communication).

Problems in comparing results from these various studies arise from

differences in daily intake of individual food items and variability

in total intake. As an illustration, Table 8 lists reported intake

rates for various food items, as well as values recommended by the

USNRC (1977) for the maximum and average individual.

The Oakes et al. (1977) study investigated fruits and vegetables

only, which represent 14.3% of the total southeastern U. S. diet on a

kg/y basis. Statistics for consumption in the Southeast were provided

by the U. S, Department of Agriculture (USDA). Total intake for persons

ingesting the Oakes et al. (1977) diet is approximately 675 kg/y,

midway between the values recommended by the USNRC. Morse and Welford

(1971) as well as Fisenne and Keller (1970) report a total annual

Table 8. Annual intake of foodstuffs (kg/y) as reported by various authors

aUSNRC Reg. Guide 1.109.bOakes et al., 1977. Only fruits and vegetables were considered; total intake of these

food items is estimated to be 14.3% by weight of the total annual intake.cFisenne and Keller, 1970; Morse and Welford, 1971.d DeBortoli and Gaglione, 1972. A survey of a sample diet representing 61% of the total

annual intake.eLalit and Ramachandran, 1980.fEERF, 1978 (personal communication). Intake values are listed for maximum and average

individual. Food categories such as grain, poultry, and fish are ignored.

26

intake of 637 kg, based on numbers available from USDA. This latter

intake estimate is similar to that of Oakes et al. (1977), although

much higher in the fruit, vegetable, and potato categories. The

DeBortoli and Gaglione (1972) study measured the 226Ra content of

commodities representing 61% of 497 kg/y total intake (excluding wine

and water). Only a few grains, and no meat were considered. Lalit

and Ramachandran (1980), reporting on a 5-year study in India, discuss

a diet of only 196 kg/y, which they consider to be representative of

the normal Indian diet.

The U. S. Environmental Protection Agency, Office of Radiation

Programs report (EERF, 1978, personal communication) presents a diet for

maximum and average individuals (Table 8) based on local food intake

in southwestern Florida. These values represent only 65% and 56%

of the respective USNRC maximum and average individual dietary intake.

The EERF did not include shellfish, poultry, eggs, grains or juices in

their analyses.

5.2 INGESTION RATES OF RADIUM-226

In spite of the wide variability in total intake of foodstuffs as

reported in the above studies, and with that variability in mind, it

is helpful to list the range of estimates for daily dietary intake of

226Ra. Table 9 summarizes reported data from literature evaluating

total dietary intake of naturally occurring 226Ra .

The studies by Morse and Welford (1971), Fisenne and Keller (1970),

and Oakes et al. (1977) were based on "market basket" surveys-in which

selected food items were purchased at local commercial supermarkets.

27

Table 9. Daily intake of naturally occurring radium-226 in the adult diet

aThis estimate includes a contribution from both milk and, water.b This estimate includes solid foods, but not milk or drinking water.cThis estimate includes a contribution from milk, but not from

drinking water.d This estimate is for fruits and vegetables only.

28

Food items studied by DeBortoli and Gaglione (1972) and Lalit and

Ramachandran (1980) were grown locally, and assumed to be in a zone of

natural radioactivity. Crops analyzed in Florida by the EERF (personal

communication) were grown locally under varying conditions of phosphate

exposure. However, only those grown under background conditions are

summarized in Table 9.

Mastinu and Santaroni (1980) studied various foods, milk, and

mineral waters in Italy, although the dietary composition was not

reported. Daily estimates for total 226Ra intake equalled 0.3-2 pCi for

adults (Table 9), 0.3-0.9 pCi for teenagers, and 1.2-5.9 pCi for one-

year-old children (l-month: 0.7-2.2 pCi; 3-month: 0.17-3.2 pCi; 6-month:

0.7-4.5 pCi). Natural levels of 226Ra in another Italian diet were

analyzed by DeBortoli and Gaglione (1972). Adults consuming foods of

local origin were estimated to ingest 1.4 pCi/d (Table 9). This esti-

mate includes a 24% contribution from milk, wine and water (estimated

intake from solid foods only was 1.1 pCi/d).

Lalit and Ramachandran (1980) reported the results of a study

measuring the concentration of 226Ra in some foodstuffs forming the

principal ingredients of a standard Indian diet. Measurements were

made over a 5-year period (1970-1974). Total average daily intake of

226 Ra for the period 1970-1974 was 3.8 pCi/d, based on a daily intake

of 410 g/d (150 kg/y) of solids (Table 8). The greatest 225Ra intake

rate recorded in Table 8 (3.8 pCi/d) results from ingestion of this

minimal diet as a result of the high specific activities found in the

principal dietary components rice, wheat, potatoes and "pulses" (peas

29

and beans). Radium-226 concentrations in milk were not analyzed, and

the estimate above does not include intake via milk or water.

Morse and Welford (1971) sampled and measured the specific activity

of 226Ra in 19 categories of food in a New York City diet. A daily

226Ra intake of 1.6 pCi (Table 9) was estimated, and included milk but

not drinking water. Fisenne and Keller (1970) also studied New York

City foodstuffs, as well as those in San Francisco; daily intake of

1.7 pCi and 0.8 pCi were reported for the two cities, respectively

(Table 9). This estimate includes milk, but not tap water.

The southwestern Florida study of the EERF (1978, personal communi-

cation) determined 226 Ra specific activities in a limited number of

food samples. Sampled fruits and vegetables were grown locally on

three types of soil:

(1) land assumed to be representative of background,

(2) reclaimed land, and

(3) land overlying unmined phosphate deposits.

An adult daily intake of 1.5 pCi/d 226Ra was estimated to result from

ingestion of local fruits and vegetables grown on land representative

of background (Table 9).

Oakes et al. (1977) calculated a total daily intake of 0.94 pCi

(Table 9), based only on a "market basket" survey of fruits and vegeta-

bles collected in Oak Ridge, Tennessee. Results do not distinguish

between locally grown and imported items.

Inspection of the available summary values (Table 9) indicates

that average daily adult intake of226Ra is similar for each region

studied. The adult range is 0.3-3.8 pCi/d.

30

5.3 DOSE ESTIMATE

The total dietary exposure estimated from annual ingestion of

selected food items (Table 9) was converted to 50-year dose commitments

by multiplying exposure and dose conversion factors recommended by

Dunning et al. (1979). These estimates are presented in Table 10.

Based on the limited range of food items sampled to date, the

average adult exposed to background dietary levels in southwest Florida

receives critical organ and whole body doses comparable to those deter-

mined for sites elsewhere in the U. S. and abroad, and less than diets

sampled in India. The average adult exposed to a diet of food items

grown on phosphate reclaimed land is estimated to receive a dose approxi-

mately twice that of background. That is, bone, 5.3E-2 rem; lung,

liver and kidney each 7.3E-4 rem, and whole body, 4.2E-3 rem.

6. RECOMMENDATIONS

During the present evaluation, the authors have identified a

number of

more real

currently

(1)

research areas that should be addressed in order to obtain a

istic quantification of food chain transport of 226Ra than

possible in the absence of site-specific data.

A principal problem area is the lack of experimentation

specifically designed to determine milk and meat trans-

fer coefficients in cattle. Not only should transfer

coefficients for the chemical forms of 226 Ra specific

to background, historical, and current phosphate mining

Table 10. Individual adult 50-year dose commitments for one year's dietary intake of radium-226 (rem) from natural sources"

Target organ Italyb

Data source

ItalyC Indiad New York Citye Yew York Cityf San Franciscof Southwest Fast Florida Tennesseeh

Bone

Lung

Liver

Kidney

Whole Body

4.71E-3 to 3.1E-2 2.2E-2 6.OE-2 2.5E-2 2.7E-2 1.3E-? 2.4F-2 1.5E-?

6.5E-5 to 4.2E-4 3.OE-4 8.2E-4 3.5E-4 3.7E-4 1.7E-4 3.2t-4 7,flE-4

6.5E-5 to 4.2E-4 3.OE-4 8.2E-4 3.5E-4 3.7E-4 1.7E-4 3.?E-4 ?.rlE-4

6.5E-5 to 4.2E-4 3.OE-4 8.2E-4 3.5E-4 3.7E-4 1.7E-4 3.2F-4 P.Qrr-4 CA w

3.7E-4 to 2.5E-3 1.7E-3 4.7E-3 Z.DE-3 2.1E-3 9.9E-4 1.9E-3 l.?F-3

aUsing dose commitment factors developed by Dunning et al., 1979. b Mastinu and Santaroni, 1980.

'DeBortoli and Gaglione, 1972.

dLalit and Ramachandran, 1980.

eMorse and Welford, 1971.

fFisenne and Keller, 1970.

gEERF, 1978, personal communication. h Oakes et al., 1977.

32

areas of southwestern Florida be determined; but releases

from tailings piles should also be simulated as nearly as

possible in feeding studies by offering contaminated feed.

In addition, sufficient numbers of animals should be

investigated to allow statistical comparison of results.

(2) The importance of ingested soil as a source of contamina-

tion for milk and meat has not been critically examined.

Data from feeding studies are needed to determine the

degree of 226 Ra solubilization from ingested mineral

soil in the digestive tract, and the subsequent internal

transport.

(3) Experimental data are needed to distinguish between

the contributions of soil and atmospheric 226Ra to

total plant 226Ra content. Particular attention should

be paid to simulation of field conditions by the use

of 226Ra compounds which may occur in soil or air

naturally, or as a product of mining activities.

(4) There is a lack of experimental data documenting soil-

to-plant transfer of 226Ra to the chief agricultural

produce commodities of the phosphate mining region,

ie., citrus and strawberries. Limited numbers of

samples have been collected for which specific activi-

ties of both the edible portions and local agricultural

soils are known. Sufficient numbers of samples should

be collected to permit statistical comparisons among

background, reclaimed, and unmined soils.

33

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