Risks from naturally occurring radionuclides in the Nordic ...¸d.pdf · radiation Other...

Risks from naturally occurring radionuclides in the Nordic diet With focus on seafood and the NKS NANOD project

Mari Komperød (Stockholm, 16.01.2019)

Recent work in Norway:

• Report on radiation doses to the Norwegian public (all sources)

• Scientific paper on ingestion doses

• Risk assessment by Scientific Committee for Food Safety

Currently:

• NKS NANOD on natural radioactivity in fish and shellfish consumed in Nordic countries

Ingestion makes a significant contribution

Naturally occurring radionuclides cause majority of ingestion exposure, but receive little attention

External radiation

(terrestrial and building

materials)

Cosmic radiation

Other radionuclides in

air

[KATEGORINAVN]

[KATEGORINAVN]

Anthropogenic radionuclides

in diet

Average exposure from environmental sources in Norway

Average effective dose

Groups with elevated exposure

Radioactivity in food and drinking water can cause substantially higher doses for some

0 2 4 6 8 10 12 14 16 18 20 22 24 26 28 30 32

Average adult

High consumption of wild foodsfrom contaminated area

High seafood consumption

Air crew

High consumption of reindeerfrom contaminated area

High natural radioactivity indrinking water

High radon levels in indoor air

Dose (mSv/y)

External radiation (terrestrial andbuilding materials)Cosmic radiation

Other radionuclides in air

Rn-222 in air

Natural radioactivity in the diet

Anthropogenic radioactivity inthe diet

Average ingestion dose per radionuclide

0.00

0.05

0.10

0.15

0.20

0.25

0.30

0.35

0.40

⁴⁰K

*

²¹⁰P

o

²²²R

n

²²⁸R

a

²¹⁰P

b

¹³⁷C

s

¹⁴C

²²⁶R

a

²³⁰T

h

²³²T

h

²³⁴U

²²⁸T

h

²³⁸U

⁹⁰S

r

²³⁵U

⁹⁹Tc

Dose (

mS

v/y

ear)

Adults

Children

Infants

= Anthropogenic

*Constant 40K dose regardless of diet, due to homeostatic K regulation in the body (and constant 40K:K ratio)

Average dose per food group

Fish and shellfish

Drinking water

Plants and mushrooms

Meat

Other foodstuffs

Dairy products

Average dose by food category in Norway (minus 40K)

Fish and shellfish is the food group causing largest ingestion dose in several countries*

Due to relatively high levels 210Po and other natural radionuclides

*Assessments from e.g. Norway, France, Japan, UK

Ingestion doses

National estimates vary Partly due to differences in

intake of fish/shellfish

Little data on naturally occurring radionuclides in Nordic food

a. UNSCEAR 2008; b. Watson et al. 2005; Komperød &

Skuterud 2018; Renaud et al. 2015; Ota et al. 2009

0

0.1

0.2

0.3

0.4

0.5

0.6

0.7

0.8

0.9

1

1.1

UNSCEAR(a)

UK (b) Norway (c) France (d) Japan (e)

mS

v/y

Average ingestion dose from naturally occurring radionuclides

210Po in fish and shellfish

• 210Po binds to surfaces of particles, including plankton

• Primary route in fish/shellfish via diet

Organisms with diet consisting of e.g. plankton, bottom substrates etc. generally have highest concentrations

Plankton photomontage by Kils at Wikipedia.com CC 3.0.

(https://commons.wikimedia.org/wiki/File:Plankton_collage.jpg)

210Po in fish and shellfish

210Po varies considerably between species

Important to use species actually consumed when performing dose assessments!!

Examples (muscle / edible parts) Po-210

(Bq/kg fw)

Atlantic coda 0.35

Atlantic mackerelb 3.5

European pilchard (sardine)b 66

Blue musselsa 37

Lobsterc 62

Common periwinkle (snail)b 283

a. Dahlgaard 1995

b. Carvalho 2011

c. Rollo et al. 1992

NKS NANOD project

Natural Radioactivity in the Nordic Diet (NANOD)

Objective: More data to improve dose assessments for fish/shellfish and total diet in the Nordic countries

Partners

• Denmark: Technical University of Denmark (DTU)

• Sweden: University of Gothenburg (GU)

• Iceland: Icelandic Radiation Safety Authority (IRSA)

• Finland: Radiation and Nuclear Safety Authority (STUK)

• Norway: Norwegian Radiation and Nuclear Safety Authority (DSA)

NKS NANOD project

Consumption

data

Existing data

Expected high

levels

Sampling

~ 10 species in

each country

Analyses: 210Po, 210Pb, 226Ra, 228Ra

Results and

improved dose

assessments

Criteria

NKS NANOD - consumption

Total and species-specific consumption varies

Preferred fish species (> 5 g/d):

0

10

20

30

40

50

60

Denmark Finland Iceland Norway Sweden

Con

su

mp

tio

n g

/da

y

Fish

Shellfish

Denmark: Herring, tuna, mackerel

Finland: Salmon, trout

Iceland: Haddock, cod

Norway: Cod, salmon

Sweden: Cod, mackerel

Note: Large individual variation!

NKS NANOD - samples

Collected samples 2018

NKS NANOD – preliminary results 210Po

0.0

0.2

0.4

0.6

0.8

1.0

1.2

1.4

1.6

1.8

2.0

Euro

pe

an

pla

ice

Atlan

tic

herr

ing

Atlan

tic

ma

cke

rel

Atlan

tic c

od

Hake

Saith

e

Hadd

ock

Atlan

tic

sa

lmo

n

Rain

bo

w t

rout

(farm

ed

)

Po

lon

ium

-21

0 in f

ish (

Bq/k

g f

w)

Baltic Sea

North Sea

Norwegian Sea

Kattegat/Skagerrak

0

10

20

30

40

50

60

70

80

90

Blu

e m

usse

l

Nort

hern

pra

wn

Bro

wn c

rab

Gre

at

sca

llop

Po

lon

ium

-21

0 in s

he

llfis

h (

Bq/k

g f

w)

Norwegian Sea

Kattegat/Skagerrak

NKS NANOD – preliminary results 210Po

Possible factors for variations within the same species:

• Location?

• Size?

• Season?

Uncertainties in assessing ingestion doses

• Representative values for activity concentration

• Reliable consumption data

• Dose coefficients (ICRP)

?

?

?

Uncertainties in assessing ingestion doses

Effect of food preparation?

By Superbass - Own work, CC BY-SA 4.0,

https://commons.wikimedia.org/w/index.php?curid=37744930

?

?

By Archangel12 - Normandy '10: Saint-Vaast-la-Hougue, CC BY 2.0,

https://commons.wikimedia.org/w/index.php?curid=31868904

Uncertainties in assessing ingestion doses

Delay from harvest until consumption

(210Po halflife = 138 days)

Lotus Head [GFDL

(http://www.gnu.org

/copyleft/fdl.html),

CC-BY-SA-3.0 via

Wikimedia

Commons ?

By Daniel Case,

CC BY-SA 3.0,

https://commons.wi

kimedia.org/w/inde

x.php?curid=58393

92

Nordic seafood in global market

> 10 % of fish export in world market

IAEA, FAO, WHO: joint project on guidelines for natural radioactivity

Already frequent requests for documentation of anthropogenic radionuclides – increased need for documentation of natural radionuclides in future?

By Strebe CC BY-SA 3.0 via Wikimedia Commons)

Summary

• Ingestion contributes a significant share of average dose, primarily through naturally occurring radiouclides

• For some, the ingestion dose is substantially higher

• Fish and shellfish is a major contributor to ingestion dose

• It is important to use species actually consumed

Way forward

NANOD: Remaining analyses, dose assessments and Final Report 2019

For improved dose assessments:

• More data on naturally occurring radionuclides in food

• Obtaining reliable consumption data (incl. percentiles)

• Futher examining effects of delay and food preparation on radionuclide levels