Dose estimates for exposure to radioactivity in gas mantles

Abstract

In this paper dose estimates are given for internal and external exposure that result, due to radioactive thorium, from the use of the incandescent mantles for gas lanterns. The collective, effective dose equivalent for all users of gas mantles is estimated to be about 100 Sv per annum in the Netherlands. For the population involved (ca. 700,000 persons) this is roughly equivalent to 5% to 10% of the collective dose equivalent associated with exposure to radiation from natural sources. The major contribution to dose estimates comes from inhalation of radium during burning of the mantles. A pessimistic approach results in individual dose estimates for inhalation of up to 0.2 mSv.

Full text

The Science
of
the Total Environment,
45
(1985)
157-
164
1
57
Elsevier Science Publishers B.V., Amsterdam -Printed in The Netherlands
IDSE ESl'IM.l\TES
R:>R
EXEOSURE
'10
RADIOACTIVITY'
IN
GAS
M.?INTLES
Otr.J.
l:fuyskens, J.'Ih.G.M. Hemelaar,
P.J.H
. Kicken
Eirdb::Jven
1.l'liversity
of
Techoology,
Health
'Alysics
Division
('nle
'll
etherlands)
In
this
paper
dose
estimates
are
given
for
internal
and
external
exposure
that
result,
due
to
radioactive
thorium,
from
the
use
of
the
incandescent
mantles
for
gas
lanterns.
The
collective,
effective
dose
equivalent
for
all
users
of
gas
mantles
is
estimated
to
be
about
100
Sv
per
annum
in
the
Netherlands.
For
the
population
involved
(ea.
700,000
persons)
this
is
roughly
equivalent
to
5%
to
10%
of
the
collective
dose
equivalent
associated
with
exposure
to
radiation
from
natural
sources.
The
major
contribution
to
dose
estimates
comes
from
inhalation
of
radium
during
burning
of
the
mantles.
A
pessimistic
approach
results
in
individual
dose
estimates
for
inhalation
of
up
to
0.2
mSv.
1.
INTIO~ION
'lh:>rium
nitrate
M8
been
used
in
the
production
of
incaroescent
mantles
for
gas
lanterns
since
before
the
turn
of
the
century.
At
high
temperatures
thorium
oxide
generates
a
bright
light.
All
isotopes
of
the
element
thorium
are
radioactive.
'lhe
radionuclide
Th-232,
which
is
present
in
the
gas
mantles,
decays
via
ten
different
radioactive
daughter
nuclides,
inclooin;J
'Ih-228.
'lhe
application
of
thorium
oxide
in
gas
mantles
is
based
on
its
physical/chemical
properties
and
is
not
linked
with
its
radioactivity.
The
presence
of
radioactivity
in
gas
mantles
must
be
seen
as
an
undesired
side
effect,
since
it
may
cause
radiation
exposure
to
people
involved
in
production,
distribution
and
the
application
of
gas
mantles.
Next
we
must
CD'lSider
the
dose
estimates
for:
-
inhalation
of
radioactive
aerosols
while
the
gas
mantle
is
burning
-
inhalation
of
radon
(Rn-220)
exhalated
from
the
mantle
-
inhalation
of
thorium
oxide
aerosols
in
air
while
manipulating
a
mantle
-
ingestion
of
thorium
oxide
-
external
irradiation.
'lhe
collective
dose
equivalent
is
estimated
for
the
Dltch
situation
on
the
basis
of
these
results.
In
the
stooy
CD'lSideration
is
given
to
the
possible
radiological
oonsequences
of
transport
and
storage
of
very
large
quantities
of
gas
mantles.
A few
remarks
are
made
on
the
pollutional
aspect
of
the
uncontrolled
removal
to
the
environnent.
0048-9697
/85/$03
.30 ©
1985
Elsevier Science Publishers B.V.

158
2.
RADIOACTIVITY
IN
GAS
MANTLES
'lborium
nitrate
is
won
from
thorium
ore.
1\11
isotopes
of
the
element
tb:>rium
are
radioactive.
'Il'lorium-232
decays
via
ten
different
dau;Jhter
nuclides
to
the
stable
Pb-208.
One
of
those
daughter
nuclides
is
Th-228.
There
is
secular
activity
equilibrium
in
the
ore
between
Th-232
and
the
radioactive
daughter
products.
After
extraction
of
thorium
from
the
ore,
the
activity
of
'lh-228
an:i
'lh-232
are
the
same.
'lhe
activity
of
all
other
dau:Jhter
products
are
initially
zero,
immediately
after
?Jrification.
'lb:lse
activities
grow
as
a
result
of
the
radioactive
decay
of
Th-232
and
Th-228.
About
40
years
after
the
thorium
extraction
there
is
again
secular
activity
equilibrium.
Insufficient
information
is
available
on
the
possible
abundance
of
Th-230
occurring
in
the
natural
decay
chain
of
uranium
(see
par.
4.6).
The
typical
value
for
.
Th-232
activity
in
gas
mantles
is
about
1000
Bq.
Figure
1 sh:>ws
the
activity
of
each
radionuclide
in
a
gas
mantle
as
a
function
of
time
since
the
extraction
of
thorium
nitrate
from
the
thorium
ore.
The
changes
in
activity
of
the
different
nuclides
during
the
use
of
gas
mantles
can
be
summarized
as
follows.
'lb:lrium
activity
(l:x>th
'lh-232
an:i
'lh-228)
remain
rou:JhlY
constant
•
.About
30%
of
radium
activity
(&3.-228
an:i
&3.-224)
is
mainly
emitted
during
the
first
45
minutes
of
burning
•
.About
60%
to
70%
of
the
original
activity
for
R>-212 an:i
Bi-212
is
distributed
to
the
air.
'lhis
emission
takes
place
during
the
first
5
to
10
minutes
of
use.
Activity
of
Ac-228
apparently
remains
unchanged.
The
decrease
in
growth
as
a
result
of
disappearance
of
the
mother
nuclide
Ra-228
is
of
no
influence.
Reduction
in
J\c-228
activity
is
cnly
a
result
of
radioactive
decay.
No
detailed
information
is
held
as
to
the
possible
emission
of
:Rn-220, Pt>-216,
Po-212
and
Tl-208.
For
all
dose
estimates
stated
in
this
report,
the
activity
for
these
nuclides
is
assumed
to
be
equal
to
the
activity
of
Bi-212
an:i Pb-212.
It
can
be
seen
that
the
activity
content
in
a
gas
mantle
is
significantly
different,
depending
on
the
age
of
the
thorium
nitrate.
In
the
following
dose
estimates
we
therefore
discriminate
between
young
mantles,
with
thorium
nitrate
several
years
old
and
old
thorium
nitrate
extracted
from
the
ore
more
than
40
years
ago.
Table
1
shows
the
estimated
radioactivity
for
the
respective
nuclides
at
different
stages
of
use,
for
three
time
periods
since
extraction
of
the
thorium
from
the
ore.

1000
·900
800
700
600
500
400
300
200
100
0 .5
11-lf-lf.--.._
~-ll-lf-ll-lf-
#
-4-
tt-
lt-W-,A.-
Th-228 ::> -.... Th-23Z
.~
·"'"
......
,,
.
.,.
!l
......
:'
.,.
'
'l
If
'
..
, .
. , .
# ~
1
ii
,..
• f
I : I
~
!T
, I : '
I
~
:
.I
.
Ii
·~
,,
R•-224 • "
Rn-220 / I
: I
: f
. I
:'
" Th-228, R•-224
\;
I Rn-220, Po-216
Po-216 •
1'
/
IPb-212
• t. Bi-212
/ j ( dec•y products
I I
of
Th-228)
.
.,.
/ I
•
I
• .
...
4 6 810
15
20 I 1 2
..
...
~
rPb-212,
Bi-212
;
~
I (decay products
of
•
\'
Th-232)
Ra-228
.'
'J
Ac-228;'
/'\
..
...
'
I .
/r
\
~·
.
2 6
810
1520
30
40
60 100
DAYS
:
l«JNTHS
4' 6 B
U:ll
I
I
YEARS
159
Fig.
1
Activity
for
'Ih-232
and decay
products
as
function
of
"age"
of
'lhoriurn
TABLE
1
E.stimated
activity
[BqJ
in
a
gas
mantle
at
3
stages
of
use
for
3
ages
of
thorium
~
U>wle:!
gas
11W1ntle
I-iat.ly
aft.er
22
hcNr9
after
the
of
uae
(mro
burning
lnlr•)
tNO
blrni"'J
hour•
first
t""
blplinc.i
hour•
age
[y]
1/12
4 40
1/12
4 40
1/12
4
40
'l'h-232 1000 1000 1000 1000 1000 1000 1000 1000 1000
lb-228
10
380
1000 270 700 270
700
Ac-228 10 380 1000 10 370
980
270 700
'lh-228
1000 425 1000 1000 425
1000
1000 425 1000
lb-224
1000 425 1000 700 300 700 700 300 700
a.-220
1000 425 1000 300 130 300 700
JOO
700
P0-216 1000 425 1000 300 130 300 700 300 700
l'b-212 1000 425 1000
JOO
130 300 620 270 620
Bi-212
1000 425 1000 300 130
)()()
620 270 620
P0-212 640 275 640 190
85
190 400
170
400
Tl-208
360 150 360 110
45
110 220
100
220

160
3. MEI'fDD
FDR
IDSE CAl.CUlATI0NS
D::>se
estimates
for
internal
exposure
are
based
on
!CRP
publication
no.
30.
'!he
estimated
value
for
the
committed
effective
dose
equivalent
follows
from
CO!llparison
of
the
intake
with
the
annual
li
mit
on
int"lke
as
define:l
by
ICRP
as
follows:
int"lke
850 = * 50
~mSV]
ALI
For
radiation
protection
purposes
this
approach
is
acceptable.
q:,wever,
it
slnuld
be
realised
that
the
ICRP-30 mooel
is
meant
to
be
usei
for
occupational
exposure.
F\lrther,
it
must
be
realised
that
results
in
dose
calculations
should
not
be
interpreted
in
individual
dose
terms.
Individual
differences
in
diet,
metabolism,
etc.
can
result
in
significant
deviations.
N.B.
For
reasons
of
readability,
effective
committed
dose
equivalent
is
abbreviated
to
dose
where
feasible.
4.1.
INHAIATI'JN OF
AEIDS:>LS
Burning
the
gas
mantle
generates
radiaoctive
aerosols
to
the
air.
~
sh::>wn
in
Table
1,
the
activity
of
the
majority
of
nuclides
decreases
significantly
in
the
first
2 h::>urs
of
use.
To some
extent
new
growth
takes
place,
deperrling
on
half-
life.
Fbr
the
first
2 h::>urs
of
use
the
individual
dose
is
estimated
to
be
0.01
mSI
for
a
young
mantle
and
0.025
mSV
for
an
old
mantle.
As
already
explained,
the
difference
is
caused
by
the
larger
amount
of
radium
activity
in
old
thorium
nitrate.
D::>se
estimates
are
based
on
assumptions
for
room
volume
(15
m3
),
ventilation
rate
(2
per
ln~r)
and
breath
volume
rate
(1.2 m3
per
lnur).
Assuming
a
use
of
2
hours
per
day
for
one
week,
the
internal
dose
from
inhalation
of
radioactive
aerosols
is
calculated
as
0.04
and
0.09
mSV
per
caput.
The
latter
result
is
based
on
the
assumption
that
all
nuclides
except
Th-232,
Th-228
and
Ac-228
are
released
to
the
air
each
time
the
mantle
is
burne:i.
Since
this
a somewhat
pessimistic
approach,
we
took
the
average
values
of
dose
calculations
and
conclude
to
a
typical
value
of
0.02
a
0.06
mSv
per
caµit
and
mantle.
It
must
be
noted
that
calculations
for
the
extreme
case
that
old
mantles
are
burned
in
a
nonventilated
room,
the
calculated
dose
is
0.2 mSI.
Exposure
of
that
kioo
should
(and
can)
be
avoide:i.

161
4.2.
INHAIATIOO
OF
~
Fad.on
exhalation
occurs
both
when
the
mantle
is
burned
and
when
the
mantle
is
not
in
use.
'lbe
dose
CXJlltribution from
radon
and
radon
dai..ghters
durir¥J
burnir¥J
is
included
in
the
results
in
par.
4.1.
'lbe
remainir¥J
dose
CXJlltribution from
radon
and
dai..ghters
is
calculated
for
the
condition
that
a
gas
mantle
is
used
for
one
week,
the
occupancy
is
8
hours
per
day,
with
crlditional
assumptions
for
breath
volume
rate
(O.S m3)
and
ventilation
rate
(2
per
hour).
As
an
average,
Ra-224
activity
in
the
mantle
is
taken
as
constant
and
equal
to
500
Bq.
calculations
result
in
an
extra
dose
CXJntribution
of
about
0.0015
mSv
.
Witb:>ut
any
ventilation,
this
dose
CXJlltribution would
be
0.011
mSv.
4. 3.
INHAIATIOO
OF
lXJST
By
combustion
of
the
tissue
the
form
and
robustness
of
the the
mantle
chan;Jes:
what
remains
is
a
brittle
structure.
'Jlny
manipulation
with
used
mantles
can
bring
fine
dust
into
the
air.
The
actual
spread
of
dust
in
air
cannot
be
foreseen,
but
it
must
be
clear
that
blowir¥J away
the
residues
of
a
mantle
will
be
a
quite
common
habit.
A
tentative
dose
estimate
is
based
on
the
assumption
that
ea.
0.1%
of
the
fine
dust
is
distributed
in
a volume
of
2
m3
as
potentially
respirable.
The
AMAD
is
chosen
as
1
micrometer.
An
occupancy
of
10
minutes
in
the
cloud
causes
inhalation
of
a
fraction
0.1.
'lbe
calculated
internal
dose
due
to
inhalation
of
thorium
oxide
results
in
approximately
0.03
mSV
per
person.
'Ibis
dose
estimate
is
based
on
'lb-232
and
'lb-228
only,
the
lower
radiotoxicity
of
the
other
nuclides
takir¥J
into
account.
4.4.
INGESTIOO
OF
'JlDRILM
OXIDE
A
fraction
of
the
dust
from
a
used
gas
mantle
could
lead
to
ingestion.
For
dose
calculations
it
is
assumed
that
ea.
1%
of
the
activity
in
the
form
of
dust
gets
on
to
the
hands
and
that
approximately
1%
of
it
will
be
swallowed.
In
addition,
an
intake
of
0.01%
is
assumed,
via
deposition,
on
objects
and/or
focrls.
New
mantles
are
plastic
ex>ated
and
are
therefore
assumed
oot
to
cause
any
ir¥Jestion.
On
these
assumptions
the
intake
by
ir¥Jestion
is
0.02%
of
the
total
activity.
Dose
calculations
were
performed
both
for
mantles
in
which
secular
activity
equilibrium
exists
and
for
mantles
in
which
cnly
'lb-232,
'lb-228
and
Ac-228
are
present.
As
an
average
the
dose
contribution
due
to
ir¥Jestion
is
estimated
to
be
0.0002
mSv
per
ea.put
and
gas
mantle.

162
4.5. E>ITEm?\L
EXP:>SURE
FUR
CAMPERS
External
radiation
exposure
c:m
result
from gamma
rays
emitted
by
the
various
daughters
of
Th-232.
Under
conditions
of
secular
activity
equilibrium
with
'lh-232
and
neglectin;J
radon
exh'llation,
the
dose
rate
at
a
distance
of
1
metre
is
calculated
to
be
3
10-
7
mSIT
per
hour
for
a
gas
mantle
with
1000
Bq
Th-232.
Even
the
most
pessimistic
assumptions
about
effective
occupancy
at
l
metre
distance
do
not
lead
to
dose
contributions
from
external
irradiations
that
are
comparable
with
the
dose
contributions
from
interMl
exposure
discussed
in
the
foregoin;J.
4.6. 'IH)RIUM-230
Since
thorium
ore
often
contains
uranium
it
must
be
n:>ted
that
the
isotope
'lh-230
could
be
also
present
in
the
thorium
nitrate
that
is
used
in
gas
mantles.
However,
it
was
not
possible
to
deduce
a
typical
value
for
the
relative
abun1ance
of
thorium-230
from
literature.
Based
on
our
own
alpha-spectromectric
measurements
we
conclu:led
that
'lh-230
activity
in
gas
mantles
was
less
than
the
'lh-228
activity.
Ibwever,
it
was broU;Jht
to
our
attention
that
high
values
could
occurr
for
the
activity
ratio
between
'lh-230
arrl
'lh-228
in
thorium
samples.
I:bse
calculations
on
the
same
model
and
assumptions
for
an
extri'i
1000
Bq
Th-230
activity
in
mantles
result
in
an
additional
nose
contribution
of
0.007
mSIT
from
inhalation
and
2.5
10-
5
mSIT
from
oral
intake
of
dust.
It
can
be
calculated
that
an
a:iditional
1000 Bq
thorium-230
would
increase
the
total
per
caput
dose
equivalent
by
an
ad.di
tional
5
to
10%.
4.
7. (J)ILEX:l'IVE IDSE
roJIVAUNT
FJR
USERS
OF
Gl.S
MANrIES
The
calculated
individual
dose
contributions,
as
already
explained,
are
summarized
in
·
Table
2.
In
addition
to
average
values,
the
possible
ranges
are
presented.
On
the
basis
of
these
dose
estimates,
the
yearly
collective
effective
dose
equivalent
can
be
calculated
for
users
of
gas
mantles.
It
is
known
that
on
a
yearly
basis
about
700.000
gas
mantles
are
imp:::>rted
to
the
Netherlarrls
arrl
sold,
97%
of
them
to
campers.
It
is
assumed
that
a
camping
unit
consists
of
two
persons
usiD:J
two
mantles
a
year.
As
summarized
in
Table
2,
the
main
contribution
to
the
collective
dose
is
from
inhalation
of
aerosols
arrl
is
estimated
to
be
in
the
ra_n;Je
of
35-80
9J
per
year.
'lhe
secccid
large
contribution
results
from
inhalation
of
thorium
oxide.
With
no
Th-230
present
about
17
SIT
is
estimated.
An
additional
1-2
SIT
per
year

163
collective
dose
equivalent
results
from
inhalation
of
radon
and
daughters
together
with
ingestion
of
radioactive
dust.
Elcternal
exposure
is
estimated
as
less
than
0.02
Sv.
Altogether
the
collective
effective
dose
equivalent
for
all
users
of
gas
mantles
is
estimated
to
be
about
100
Sv
per
annum
in
the
Netherlands.
tnse
estimates
for
cnly
}'OUB3
gas
mantles
result
in
a ran:Je
of
from
30-76
Sv,
while
a
range
of
values
between
50-150
Sv
has
been
calculated
when
only
old
thorium
nitrate
gas
mantles
were
used.
It
srould
be
evident
that
the
accuracy
of
these
figures
soould
not
be
overestimated.
'lbe
various
results
of
dose
calculations
rely
heavily
en
the
assumptions
made
as
the
various
parameters.
Of
real
importance
is
the
relative
value
of
this
collective
dose.
For
example,
in
relaticn
to
the
collective
effective
oose
equivalent
from
natural
sources
which
can
be
taken
as
about
1200
Sv
for
the
exposed
group
of
700,000
persons.
'lbe
collective
oose
that
results
from
the
use
of
gas
mantles
is
in
the
order
of
5
to
10%
of
this.
TABLE
2
D:lse
estimates
per
caput
and
collective
I:.-
equi
Y&l.ent
per
cap..tt
and
9119
111antle Cl:>lleetive <Dee
[in
millisievert)
[in
Sievert]
age
of
'lh
( 4
40
40 ( 4
40
[:r-r•J
ventilation
a
rate
[per
hour)
Inhalation
a.a25
a.06
0.2 35
80
of
aeroa:>ls
(a.a1-o.04)•
(a.a25-0.Q9)•
(a.l-0.3)*
(14-56)*
(35-126)*
Inhalatim
a.001
a.0015
a.au
1.4
2.1
of
radon
Inhalation
0.024
a.a26
o.a33
16.8 18.2
of
dust
Irqestion
of
l.
7xl0-4
2.
2xl.a-4
2.2xlo-4
a.12
o.1s
thorit.11.
oxide
External
<
l.
3xl0-5
l.
3x10-S
l.
Jxla-
5
a.a2 a.a2
exposure
Total
a.as
0.09
a.2
53 100
(a.03-0.a7)
(0.~.13)
(a.l-0.3)
(30-76)
(Sl-lSa)
•range
dt»
to
:ncdel
assumptions
5.
REMARKS
In
the
complete
report
of
the
study
dose
estimates
are
also
given
for
transport
and
storage
of
large
quantities
of
mantles.
Collective
dose
contribution
from
external
exposure
is
about
0.1
Sv
per
year.
In
abnormal
circumstances,
especially
in
the
event
of
fire,
relatively
high
individual
doses
from
internal
cx:ntaminaticn
are
p:>ssible.

164
In
general,
no
special
measures
are
taken
to
regulate
the
disposal
of
used
gas
mantles.
Even
in
a
conservative
appr0ach
it
is
estimated
that
local
concentrations
of
thorium
in
domestic
refuse
cannot
be
more
than
0.15
Bq '1'1-232
per
kilogram,
which
is
less
than
1%
of
the
"natural"
concentration
in
soil
(25
Bq
per
kilogram).
It
is
concltrle:i
that
the
uncontrolle:i
removal
of
use:i
gas
mantles
throuqh
the
environment
(soil)
does
not
result
in
a
significant
increase
of
environmental
radiation
exp:>sure.
REFERFNCES
1
ICRP
Publication
30,
Limits
for
intakes
of
radionoclides
by
workers,
part
1,
Pergamon
Press,
OXford,
1979.
2 J.W.
I.uetzelschwab
and
s.w.
G:>ogins,
Radioactivity
released
from
burning
gas
latern
mantels,
~alth
"Rlysics,
\bl.
46,
oo.
4,
pp.873-881,
1984.
3
L.
Hannibal,
On
the
radiological
significance
of
inhale:i
uranium
arrl
toorium
ore
dust,
Health
Physics,
Vol.
42,
no.
3,
pp.
367-371,
1982.
4 O'D::>nnell,
Assessment
of
radiation
doses
from
radioactive
materials
in
consumer
products
-
methods,
problems,
and
results,
Radioactivity
in
consumer
Erodocts,
NUREG/CP-0001, 1978.
5
Environmental
assessment
of
consumer
products
containing
radioactive
material,
NUREG/CR
1755, IB
Nuclear
R:!gulation
Cbmmission, 1980.
6 R.R. ')'D::>nnel,
and
E.L.
Etnier,
An
Assessment
of
Radiation
D::>ses
from
Incandescent
Gl.s
Mantles
that
contain
'lllorium,
NUREG/CR-1910, 1981.
7
J.
IJ..Jetzelschwab, D:?termining
the
Fiqe
of
Gl.s
lantern
Mantles
Using
Gl.mma-
ray
l\nalysis,
Am.J.Phys.
51
(6),
pp.
538-542,
1983.
8
Chr.J.
Huyskens,
J.Th.G.M.
Hemelaar,
P.J.H.
Kicken,
Stralingsdoses
ten
ge-
volge
van
radioactiviteit
in
gloeikousjes,
Report
no.
SBD
4889,
January
1985,
Ein:ihollen
U'liversity
of
Technology,
~lth
Physics
Divison
( <bmplete rep:>rt
of
this
study.)