Directory UMM :Data Elmu:jurnal:E:Environmental Management and Health:Vol09.Issue5.1998:
Workplace radon in Northamptonshire
A.R. Denman
Me dic al Physic s De partme nt, No rthampto n Ge ne ral Ho spital, Clifto nville ,
No rthampto n, UK
Paul S. Phillips
Sc ho o l o f Enviro nme ntal Sc ie nc e , Ne ne Co lle ge o f Highe r Educ atio n, Park
Campus, No rthampto n, UK
Northamptonshire is classifi ed
as a radon affected area, with
greater than 1 per cent of
domestic dwellings being
above the UK Action Level of
200Bq m–3 . Workplace radon
is also a health risk in
Northamptonshire, with a
signifi cant number of premises
being predicted to be above
this Action Level (400Bq m–3 ).
After an extensive survey in
National Health Service
premises, using track etch
detectors and real time monitoring systems, it was found
that certain staff were receiving very high doses – up to
around 20mSv. The annual
collective dose from radon, in
the rooms with elevated levels,
was 285mSv, an average of
4.45mSv. After remediation of
the rooms the average dose
fell to 0.5mSv. The average
cost of radon remediation in
National Health Service
premises was £3,950 per
location. This compares to a
value of £1,953 for locations
in schools in Northamptonshire. It is possible that remediation costs for the majority
of small to medium enterprises
in the country will, on our
conservative estimate of 6 per
cent being above the Action
Level, be in the region of
£1,460,000. Further monitoring of workplace radon is
taking place across the county
in an attempt to determine
more accurately the full extent
of the problem.
Enviro nme ntal Manage me nt
and He alth
9 / 5 [ 1998] 1 9 4 –1 9 9
© MCB Unive rsity Pre ss
[ ISSN 0956-6163]
[ 194 ]
Introduction
Ra don is a n a tu r a lly occu r r in g r a dioa ctive
ga s for m ed in th e decay ser ies of u r a n iu m .
Th e on ly isotope of r a don n or m a lly a bu n da n t
en ou gh to ca u se a h ea lth pr oblem is 222Rn .
Th is isotope is for m ed by th e decay of 238U. It
h a s a h a lf life of 3.82 days a n d decays in to
218Po, wh ich in tu r n decays in to 214P b, 214Bi
a n d 214Po. Th ese fou r r a dion u clides a r e ca lled
r a don da u gh ter s or pr ogen y a n d ca n be fou n d
a tta ch ed to a er osol pa r ticles in in door a ir.
Th e isotopes 222Rn , 218Po a n d 214Po a r e a ll
a lph a pa r ticle em itter s; th ese pa r ticles r esu lt
in ver y loca lised en er gy deposition in livin g
tissu e. Th e 222Rn isotope pr ovides th e la r gest
con tr ibu tion (50 per cen t) to th e tota l r a dia tion dose r eceived by th e gen er a l UK popu la tion – 2.6 m illiSiever ts (m Sv).
Th e sta n da r d u n it of a ctivity is th e
Becqu er el (Bq) – on e n u clea r disin te gr a tion
per secon d. Activity con cen tr a tion s a r e
qu oted a s becqu er els per cu bic m etr e (Bq
m –3). Th e u n it for dose equ iva len t is th e
Siever t (Sv). In stu dies on low dose r a dia tion
it is u su a l to give doses in m illiSiever ts
(m Sv).
In th is pa per we r epor t r esu lts fr om a
deta iled su r vey ca r r ied ou t in N a tion a l
Hea lth Ser vice (N HS) pr em ises in N or th a m pton sh ir e, a cou n ty in th e Midla n ds of E n gla n d, a n d com pa r e r em edia tion costs w ith
oth er wor k pla ces.
Radon in buildings
Th er e a r e a n u m ber of sou r ces for r a don in
bu ildin gs. Th ese in clu de: ou tside a ir, w a ter
su pplies, bu ildin g m a ter ia ls a n d th e gr ou n d
u n der th e bu ildin g. Over a ll, th e m ost sign ifi ca n t sou r ce is th e gr ou n d u n der th e bu ildin g.
Ra don in ou tside a ir in th e UK is fou n d in
ver y low levels, w ith a m ea n of 4Bq m –3
(Wr ixon et a l., 1988) a n d it is u n lik ely to lea d
to eleva ted levels of in door r a don .
Ra don en ter s bu ildin gs via cr a ck s in con cr ete floor s, th r ou gh ga ps in su spen ded
wooden floor s a n d via ser vice poin ts. Th e
r ea son for th e en tr y is th a t th e a tm osph er ic
pr essu r e is lower in door s th a n ou tdoor s. Air
w ill fl ow in to a n or m a l UK dom estic bu ildin g
a t a r ou n d 1 ch a n ge per h ou r a n d a r ou n d 1 per
cen t of th a t w ill com e fr om soil ga s.
Th e m ea n UK r a don con cen tr a tion in
dwellin gs is n ea r to 20Bq m –3 (Br ow n et a l.,
1981). Alth ou gh th e m ea n va lu e is low th er e
a r e a sign ifica n t n u m ber of dwellin gs over
1,000Bq m –3 or m or e. Ra don levels ca n va r y
m a r k edly fr om n igh t to day (F igu r e 1) a n d
a lso fr om sea son to sea son . In deed, sea son a l
cor r ection fa ctor s m u st be a pplied to ever y
va lu e deter m in ed to give a tr u e r epr esen ta tion of a n aver a ge va lu e over a yea r.
Th e bu ildin g r esea r ch esta blish m en t (BRE )
h a s u n der ta k en a su r vey of th e va r iou s
m ea n s to r em edy eleva ted r a don levels in
bu ildin gs a n d h a s pu blish ed its fin din gs, e.g.
BRE (1992)
Radon af fected areas
In 1990 th e N a tion a l Ra diologica l P r otection
Boa r d (N RP B) r ecom m en ded th a t th e Action
Level for r a don in existin g h om es be 200Bq
m –3, aver a ged over a yea r. P a r ts of th e cou n tr y
w ith a 1 per cen t, or gr ea ter, pr oba bility of
h om es bein g a bove th is level a r e r e ga r ded a s
a ffected a r ea s. Th e N RP B a dvised th a t Cor n w a ll a n d Devon sh ou ld be r e ga r ded a s su ch in
1990. In 1992, Der bysh ir e, N or th a m pton sh ir e
a n d Som er set (N a tion a l Ra diologica l P r otection Boa r d, 1992) wer e sim ila r ly cla ssified.
For a cou n ty, wh ich is a n a ffected a r ea , a
r a don m a p is pr odu ced th a t sh ow s a r ea s w ith
< 1 per cen t, 1-3 per cen t, 3-10 per cen t a n d > 30
per cen t of h om es bein g a bove th e a ction
level, th is fa cilita tes a ction by th e a ppr opr ia te a u th or ities, via bu ildin g r e gu la tion s.
F igu r e 2 con ta in s in for m a tion a bou t th e
per cen ta ge of h om es in N or th a m pton sh ir e
a bove th e a ction level.
A.R. De nman and
Paul S. Phillips
Wo rkplac e rado n in
No rthampto nshire
Radon and geology
E leva ted r a don levels ca n be equ a ted w ith th e
u n der lyin g geology a n d in pa r ticu la r th e
con cen tr a tion of 226Ra , th e pr ecu r sor of 222Rn ,
in r ock s a n d soil. E leva ted levels of 226Ra
sh ou ld lea d to h igh levels of 222Rn in soil ga s.
It m u st a lso be r em em ber ed th a t soil per m ea bility is a n oth er im por ta n t fa ctor.
N or th a m pton sh ir e is a n a r ea of sedim en ta r y J u r a ssic r ock s. Th e h igh est r e gion s of
r a don pr odu ction a r e fou n d on N or th a m pton
sa n d ir on ston e, u pper Lin coln sh ir e
Enviro nme ntal Manage me nt
and He alth
9 / 5 [1 9 9 8 ] 1 9 4 –1 9 9
Figure 1
Variatio ns in indo o r rado n le ve ls in a NHS ro o m in No rthampto n
Radioactivity/Bq m –3
2400
2000
1600
1200
800
6.30 Tue
10.30 Tue
2.30 Tue
22.30 Mon
18.30 Mon
14.30 Mon
6.30 Mon
10.30 Mon
2.30 Mon
22.30 Sun
18.30 Sun
14.30 Sun
6.30 Sun
10.30 Sun
2.30 Sun
22.30 Sat
18.30 Sat
14.30 Sat
6.30 Sat
10.30 Sat
2.30 Sat
22.30 Fri
18.30 Fri
0
14.30 Fri
400
Time of day
Figure 2
Pe rc e ntage o f ho me s, in No rthampto nshire , abo ve the ac tio n le ve l
Key
1-3
3-10
Corby
10-30
Kettering
Wellingborough
Daventry
Northampton
lim eston e, gla cia l sa n d a n d gr avel. Th e
ir on ston e con ta in s ph osph or u s, wh ich is
often a ssocia ted w ith u r a n iu m .
Radon and workplace legislation
E xposu r e of wor k er s to r a don is gover n ed by
th e Ion isin g Ra dia tion s Re gu la tion s 1985
(Hea lth a n d Sa fety E xecu tive, 1985), a n d th e
Hea lth a n d Sa fety Com m ission h ave issu ed
a n Appr oved Code of P r a ctice cover in g r a don
(Hea lth a n d Sa fety Com m ission , 1988). Hea lth
a n d Sa fety execu tive a dvice is th a t em ployer s
in a ffected a r ea s a r e r equ ir ed by th e Ma n a gem en t of Hea lth a n d Sa fety a t Wor k Re gu la tion s 1992 (Hea lth a n d Sa fety E xecu tive, 1992)
to m a k e a r isk a ssessm en t a bou t r a don by
testin g th eir pr em ises.
Th e N RP B h ave a dvised th a t th e a ction
level for dom estic pr em ises be 200Bq m –3 a n d
400Bq m –3 for wor k pla ces. At levels a bove 400
in wor k pla ces, th e Ion isin g Ra dia tion s Re gu la tion s a r e deem ed to a pply a n d th e Hea lth
a n d Sa fety E xecu tive m u st be n otified. Room s
w ith levels over 1,000Bq m –3 a r e Con tr olled
Ar ea s a n d r equ ir es a ction , u n der Re gu la tion s, to lim it dose.
Th is stu dy u ses th e best cu r r en t estim a tes
to r ela te r a don exposu r e to dose r eceived. It
w a s a ssu m ed th a t 126k Bq h –1 m –3 w a s equ iva len t to 1m Sv. Th is fa ctor w a s der ived fr om
fa ctor s in th e A pprov ed Cod e of Pra ctice
(Hea lth a n d Sa fety Com m ission , 1988)
Radon: a human carcinogen?
Stu dies w ith m in er s exposed to r a ised levels
of wor k pla ce r a don , a n d its pr ogen y, h ave
fou n d th a t exposu r e in cr ea ses th e r isk of lu n g
ca n cer. Th e N RP B h ave r eviewed 11 stu dies
th a t pr odu ce over wh elm in g eviden ce th a t
r a don h er e is a h u m a n ca r cin ogen (N a tion a l
Ra diologica l P r otection Boa r d, 1993).
N u m er ou s ca se-con tr olled stu dies h ave
been la u n ch ed to dir ectly a ssess th e lu n g
ca n cer r isk fr om in door r a don . Som e stu dies
r epor t positive or wea k ly positive fi n din gs,
oth er s r epor t n o in cr ea sed r isk a t a ll.
In a n a ttem pt to pr ovide m or e in for m a tion
a r ecen t m eta -a n a lysis of eigh t ca secon tr olled stu dies w a s ca r r ied ou t (Lu bin a n d
Boice, 1997). Th e stu dy con clu des th a t th e r isk
fr om in door r a don is in lin e w ith th a t wh ich
h a s been pr oposed on th e ba sis of stu dies
w ith m in er s a n d th a t it is a ca r cin ogen in th e
h om e a n d th e wor k pla ce.
Tow ces ter
Materials and methods
Source: NRPB
Ra don is a n a lph a em itter, a s a r e two of its
sh or t-lived pr ogen y. Th e m eth od for detection
[ 195 ]
A.R. De nman and
Paul S. Phillips
Wo rkplac e rado n in
No rthampto nshire
Enviro nme ntal Manage me nt
and He alth
9 / 5 [1 9 9 8 ] 1 9 4 –1 9 9
for gen er a l su r vey wor k is a sm a ll r a don
diffu sion ch a m ber h ou sin g a pla stic a lph a tr a ck detector (Den m a n , 1994). Th is pr ovides
a m ea su r e of th e tota l r a don exposu r e over
th e m ea su r em en t per iod. It is th en possible to
ca lcu la te th e aver a ge r a don con cen tr a tion
over th e m ea su r em en t per iod.
To en su r e th a t th e r espon se is little a ffected
by diu r n a l a n d oth er tim e va r ia tion s in
r a don , th e detector s wer e left in position for
on e to th r ee m on th s. Tim e-aver a ged va lu es
wer e ca lcu la ted u sin g N RP B va lu es for sea son a l cor r ection fa ctor s.
Hou r ly m ea su r em en ts wer e m a de in r oom s
w ith eleva ted r a don levels th a t displayed
m a r k ed va r ia tion s (F igu r e 1). Th is occu r r ed
over a per iod of on e to fou r week s u sin g a
dir ect r ea din g RAD seven m eter (Den m a n
a n d P a r k in son , 1996). Th is a ctively pu m ps a ir
sa m ples in to a m ea su r in g ch a m ber. Sta ff
wer e a sk ed to fill in a qu estion n a ir e to in dica te h ow m a n y h ou r s th ey spen t in ea ch r oom
in a n a ttem pt to estim a te th e occu pa n cy
fa ctor. Th e r a dia tion dose to sta ff cou ld th en
be ca lcu la ted, a n d expr essed a s a n effective
r a dia tion dose u sin g th e r ela tion th a t 1m Sv is
equ a l to 126k Bq m –3 h ou r s.
Th e a ccepted pr otocol for r a don m ea su r em en t in th e wor k pla ce is to position detector s
in a selection of gr ou n d fl oor r oom s ch osen to
r eflect th e n or m a l occu pa n cy pa tter n of th e
bu ildin g. In sm a ll pr em ises, a detector is
pla ced in ea ch of th e two m ost fr equ en tly
occu pied r oom s. In la r ge bu ildin gs on e
sh ou ld be deployed for a t lea st ever y 100m 2 of
floor spa ce. In ver y la r ge, open bu ildin gs on e
sh ou ld be u sed for ever y 500m 2 of floor a r ea .
Results
N or th a m pton sh ir e is a n a ffected a r ea a n d
eleva ted levels of in door wor k pla ce r a don a r e
to be expected. Th e r esu lts for distr icts a n d
bor ou gh s in N or th a m pton sh ir e a r e to be
fou n d in Ta ble I. In clu ded in Ta ble I a r e aver a ge r a don va lu es in h ou sin g in th e r e gion s,
Table I
Numbe r o f wo rkplac e s te ste d and the pe rc e ntage abo ve the ac tio n le ve l
District/
borough
Corby
Daventry
East Northants
Kettering
Northampton
South Northants
Wellingborough
[ 196 ]
Average radon
Number Percentage above levels in housing
tested
action level
(Bq m–3 )
37
228
80
178
184
52
95
11
9
10
16
21
10
14
38
74
63
107
55
61
66
Population
Area
(ha)
53,000
63,000
68,000
77,000
181,000
71,000
68,000
8,000
66,600
51,000
23,400
8,100
63,500
16,300
th ese su r veys a r e exten sive, ba sed on a la r ge
n u m ber of dwellin gs, a n d give a n in dica tion
of possible levels in th e wor k pla ce.
Th e qu a n tity of da ta is still r ela tively sm a ll
a n d so som ewh a t lim its th e con fi den ce th a t
ca n be pla ced on it, even so, th e r a n ge fr om 9
to 21 per cen t, clea r ly su ggests th a t th er e is a
sign ifica n t pr oblem in th e r e gion . Th ese
va lu es a r e h igh com pa r ed to th e a ppr oxim a tely 6 per cen t of th e sch ools in th e cou n ty
th a t r equ ir ed r em edia tion for wor k pla ce
r a don . Th e va lu e for sch ools is pr oba bly
r epr esen ta tive of th e sca le of th e pr oblem
a cr oss th e cou n ty. Sch ools a r e even ly spr ea d
a n d th ey r epr esen t wor k pla ces th a t differ in
size fr om th e sm a ll, som e 60 pu pils, to th e
ver y la r ge, w ith h u n dr eds of pu pils a n d la r ge
com plexes of bu ildin gs. Th e r esu lt fr om
sch ools, h owever, n eeds to be tr ea ted w ith
som e ca u tion a s m ost r oom s a r e qu ite la r ge,
bu t in bu ildin gs w ith sm a ller r oom s th e pr opor tion a bove th e lim it m ay be h igh er. Th e
per cen ta ge for N HS pr oper ties, a t 8 per cen t,
m ay be h igh er beca u se of th e sign ifica n t
n u m ber of sm a ller offices. A m or e deta iled
su r vey is u n der w ay in th e cou n ty, in a n
a ttem pt to deter m in e a m or e a ccu r a te figu r e
for th e pr opor tion a bove th e a ction level, bu t
th is w ill n ot r epor t for som e tim e yet.
Ra don levels ca n va r y m a r k edly even w ith in
r ela tively sm a ll a r ea s. Th e va lu es for th e a r ea
cover ed by Nor th a m pton Bor ou gh a r e pr esen ted a ccor din g to postcode in Ta ble II.
N or th a m pton sh ir e N HS pr oper ties a r e
w ith in fou r N HS tr u sts, a n d in clu de two gen er a l h ospita ls, h ea lth cen tr es a n d r esiden tia l
h om es, th e tota l n u m ber of pr oper ties is 82.
Th e tota l sta ff n u m ber is som e 6,693 wh ole
tim e equ iva len ts. Ou r su r vey h a s to da te
m ea su r ed r a don levels in 1,038 r oom s a n d th is
h a s th e u su a l log-n or m a l distr ibu tion wh ich
is a lso r epor ted in a n u m ber of su r veys of
r esiden tia l pr em ises w ith 1 per cen t over
1,000Bq m –3 a n d 8 per cen t over th e wor k pla ce
a ction level. Typica l r ea din gs fr om a bu ildin g
w ith r a ised levels a r e fou n d in Ta ble III. Th e
r esu lts for th e distr ibu tion of r a don over a ll
pr oper ties a r e fou n d in Ta ble IV.
Table II
Variation in radon levels in c ommerc ial premises
within a borough c ounc il (Northampton), by
postc ode
Radon
(Bq m–3 )
NN1
0-99
100-199
200-399
> 400
33.6
23.5
14.3
28.6
Percentage of properties
NN2
NN3
NN4
53.3
20.0
0
26.7
56.3
18.8
15.6
9.3
75.0
4.1
8.3
12.8
NN5
50.0
25.0
6.2
17.8
A.R. De nman and
Paul S. Phillips
Wo rkplac e rado n in
No rthampto nshire
Table III
De taile d surve y o f an NHS building with raise d
rado n le ve ls
Enviro nme ntal Manage me nt
and He alth
9 / 5 [1 9 9 8 ] 1 9 4 –1 9 9
Location
Direct reading (Bq m–3 )
800
1,800
3,200
1,900
700
50
300
Reception
Interview room
Consulting room
Treatment room
Corridor
Staff toilets
Rest room
Sever a l r oom s a r e ver y sm a ll stor e r oom s
th a t a r e r a r ely en ter ed, th ese h ave been discou n ted a n d w ill n ot be r em edia ted. A tota l of
21 wor k pla ce loca tion s wer e fou n d to be over
th e lim it a n d n eedin g r em edia tion . In a ll, 11
h ave been su ccessfu lly r em edia ted a n d two
r equ ir e fu r th er wor k . Th e costs for th e
r em edia tion for loca tion s is fou n d in Ta ble V,
wh ich a lso con ta in s da ta on oth er types of
wor k pla ce loca tion s in N or th a m pton sh ir e.
Loca tion s w ith levels in excess of 550Bq m –3
wer e fitted w ith on e or m or e su m ps a n d
extr a ctor fa n s. Th e tota l cost for th ese eigh t
loca tion s w a s £39,300. Th e lowest cost for
th ese loca tion s w a s £640, h er e a sin gle su m p,
w ith fa n , w a s in sta lled to su ccessfu lly r em edia te on e sm a ll r oom .
In a n oth er ca se, wh er e th e level w a s 430Bq
m –3, th e void below th e bu ildin g w a s fitted
w ith a n im pr oved for m of pa ssive ven tila tion
a s well a s a ddition a l fa n s to a ctively expel a ir
fr om th e u n der floor void to th e exter n a l
en vir on m en t. Th is w a s con sider ed su ita ble to
br in g th e level below th a t r equ ir ed by le gisla tion . Th e cost for th is w a s £2,000.
A fu r th er two loca tion s, wh er e r a don levels
wer e ju st a bove th e lim it, wer e fitted w ith
extr a ctor fa n s on ly in th e u n der floor void,
su m ps wer e n ot deem ed n ecessa r y. Th e cost
for th ese w a s £2,150.
As soon a s a pr oblem w a s detected a Hea lth
a n d Sa fety a dviser w a s con su lted. An a ction
pla n w a s devised a n d ten der s wer e in vited
fr om com pa n ies wh o wer e on th e UK Ra don
Cou n cil’s list of a ppr oved con tr a ctor s. Rem edia l wor k w a s th en ca r r ied ou t, m ostly w ith in
Table IV
Distributio n o f rado n le ve ls in site s in NHS pro pe rtie s in No rthampto nshire
Average radon
level (Bq m–3 )
< 100
101-200
201-300
301-400
>400
Hospital A
(Northampton Sand)
Hospital B
(Upper Lias Clay)
Total of
all sites
207
37
13
8
16
130
44
19
7
5
655
184
64
39
81
a per iod of a r ou n d th r ee m on th s. On ly in on e
ca se, th a t of a n office w ith levels of 2,870Bq
m –3, w a s it n ecessa r y to eva cu a te a n d pr even t
sta ff en ter in g.
Th e a n n u a l dose fr om r a don in th e N HS
wor k pla ce h a s been estim a ted for 64 sta ff wh o
wor k in th e iden tified h ot-spots. Th e distr ibu tion is sh ow n in F igu r e 3. Th e a n n u a l tota l
collective dose for th ese sta ff fr om r a don w a s
285m Sv, a n aver a ge of 4.45m Sv. After r em edia tion th e aver a ge dose fell to 0.5m Sv.
Discussion
Sim ple estim a tes of dose to wor k er s, ba sed on
aver a ge r a don levels, ca n be m islea din g.
Ra don levels ca n va r y m a r k edly du r in g a 24
h ou r per iod (F igu r e 1) w ith th e h igh est levels
a ppea r in g ou tside of sta n da r d wor k in g h ou r s.
As occu pa n cy, on th e wh ole, decr ea ses th er e is
a r edu ction in ven tila tion w ith a n in cr ea se in
r a don con cen tr a tion . As som e or ga n isa tion s
m ay em ploy a n u m ber of sh ift wor k er s a t
n igh t tim e, wh o oper a te in a seden ta r y m a n n er, th er e m ay be con sider a bly gr ea ter doses
r eceived by th ese th a n oth er s wh o wor k du r in g th e day. Th e NHS em ploys a con sider a ble
n u m ber of n igh t wor k er s a n d th ese m ay be a t
extr a r isk . However, it is essen tia l to k n ow th e
va r ia tion s in r a don levels th r ou gh ou t a 24
h ou r per iod a s well a s th e tim e-aver a ged
levels, over pr olon ged per iods, to design a
com pr eh en sive r em edia tion pa ck a ge.
Th e N RP B in dica te th a t con tin u ou s exposu r e for 80 per cen t occu pa n cy a t 100Bq m –3
gives a n effective dose of a r ou n d 5m Sv per
yea r. In th e m a n a gem en t of h igh r a don levels
it is essen tia l to r edu ce levels a s qu ick ly a n d
effectively a s possible to th e wor k pla ce a ction
level. In cr ea sin g ven tila tion a lon e ca n r esu lt
in som e clea r a dva n ta ges. In on e r oom , w ith a
va lu e of 710Bq m –3 du r in g wor k in g h ou r s,
m er ely open in g w in dow s ca u sed th e dose to
sta ff to dr op fr om 5.0m Sv to 1.1m Sv per yea r.
Im m edia te a ction m u st be ta k en wh en a loca tion is iden tified w ith ver y eleva ted levels. In
som e ca ses it is n ecessa r y to tem por a r ily sea l
off th e r oom , or sever ely lim it a ccess, u n til
r em edia tion . In extr em e ca ses, for say ver y
sm a ll stor e r oom s, it m ay be m or e cost effective to sea l off th e r oom per m a n en tly a s th e
cost of lon g ter m r em edia tion m ay be gr ea ter
th a n th e va lu e of th e spa ce.
In som e ca ses, befor e r em edia tion , N HS
sta ff wer e r eceivin g doses well a bove 5m Sv
per yea r. Th ese doses a r e in excess of th ose
r eceived by h ospita l wor k er s wor k in g w ith
r a dia tion , su ch a s r a diogr a ph er s, r a diologists, ph ysicists a n d r a dioth er a pists.
We h ave ca lcu la ted th a t ou r pr ogr a m m e
costs a r ou n d £180,000 to a ch ieve a n a n n u a l
[ 197 ]
Ma n -Siever t r edu ction . It is in ter estin g to
com pa r e th is va lu e w ith th a t pr oposed for
dom estic pr oper ties in Sweden (Sn ih s, 1992).
Sn ih s su ggests th a t costs in Sweden a r e
a r ou n d £30,000 per Ma n -Siever t saved a n n u a lly, a t a n a ction level of 400Bq m –3. E xposu r e
in th e wor k pla ce is n ot dir ectly com pa r a ble
w ith th e h om e, a s r esiden ts a r e exposed to
r a don in th e h om e wh en levels a r e th e h igh est, wh ile m a n y wor k er s a r e exposed to th e
lowest r a don levels if wor k in g 9 a .m . to 5 p.m .
Th e volu m e of a r oom is a lso a cr itica l fa ctor,
ver y la r ge a r ea s h ave a r edu ced sta ck effect
a n d ver y little u n der pr essu r e. It is difficu lt to
dir ectly com pa r e both situ a tion s bu t it ca n be
sa id th a t r em edia tion in com m er cia l
pr em ises ten ds to be sign ifi ca n tly h igh er in
cost th a n dom estic dwellin gs a s th er e a r e
often m u ltiple foci of r a don en tr y wh ich com plica tes r a don r edu ction .
Th e costs for a r a don pr ogr a m m e a r e
a lw ays gr ea ter th a n th e m er e costs of r em edia tion . We qu ote a va lu e of £43,450 for r em edia tion wor k bu t th is n e glects th e costs of detector s a s well a s sta ff tim e. We estim a te th a t on
com pletion th e tota l cost w ill be a r ou n d
£98,000 for a ll 21 loca tion s. For ou r stu dy,
r em edia tion costs a r e 76.5 per cen t of tota l
costs, th e oth er s a r e; sta ff tim e (9.2 per cen t)
a n d detector s (14.3 per cen t).
Th e da ta th a t a r e ava ila ble for r em edia tion
costs a r e in for m a tive. Th ose for r em edia tion
A.R. De nman and
Paul S. Phillips
Wo rkplac e rado n in
No rthampto nshire
Enviro nme ntal Manage me nt
and He alth
9 / 5 [1 9 9 8 ] 1 9 4 –1 9 9
Table V
Co sts, so far, fo r re me diatio n in so me No rthampto nshire wo rkplac e s
NHS
11
Number of locations
Total cost (£)
43,450
Average cost
per location (£)
3,950
Range (£)
640-13,865
Schools
Libraries
Social service
Police
21
41,031
2
1,546
12
20,955
3
1,908
1,953
259-8,500
773
568-978
1,746
563-6,362
636
589-703
Figure 3
Estimate d do se s fo r 6 4 staff in lo c atio ns with raise d rado n le ve ls
Number of Staff
30
25
20
15
in sch ools a r e pa r ticu la r ly u sefu l to com pa r e
w ith th ose fr om th e N HS. Th e costs com e
fr om r em edia tion in 21 sch ools ou t of th e
a ppr oxim a tely 360 tested th r ou gh ou t th e
cou n ty. Th e costs a r e h igh er in th e N HS pr oper ties beca u se of a sm a ll n u m ber of situ a tion s
th a t pr oved pa r ticu la r ly difficu lt to dea l w ith ,
beca u se of m u lti-foca l en tr y poin ts. Th e costs
for th e sch ools a ppea r to be m or e r epr esen ta tive of “th e aver a ge situ a tion ” fou n d th r ou gh ou t th e cou n ty for sm a ll to m ediu m en ter pr ises (u p to 250 em ployees), especia lly th ose
w ith la r ger r oom s.
Th e a r ith m etic m ea n of £1,953 for sch ools
com pa r es to a fi gu r e of a r ou n d £1,110 th a t ca n
be der ived fr om da ta pr ovided by th e N RP B
for r em edia tion of dom estic pr oper ties, w ith
su m ps (Ken da ll et a l., 1994). Ou r da ta for
sch ools spa n th e per iod 1993 to 1996 a n d th e
da ta fr om th e N RP B a r e u p u n til m id-1994.
Du r in g th a t tim e r em edia tion costs h ave
h a r dly r isen , so th e figu r e qu oted by th e
N RP B w ill still sta n d, to a good a ppr oxim a tion , today.
With in N or th a m pton sh ir e th er e a r e
a ppr oxim a tely 19,000 en ter pr ises, th a t fa ll
in to th e follow in g ca te gor ies:
• 15,000 1 – 10 em ployees;
• 4,000 11 – 199 em ployees;
• 100 > 200 em ployees;
Wor k pla ces in th e fir st ca te gor y sh ou ld h ave
r em edia tion costs a ssocia ted m or e closely
w ith dom estic a n d th ose in th e secon d w ith
sch ools a n d so it is possible to su ggest a n
a ppr oxim a te figu r e for a lik ely cost to th e
cou n ty to r em edia te in th ese types of bu sin ess, a ssu m in g th a t 6 per cen t r equ ir e r em edia tion . Th e figu r e is in th e r e gion of
£1,460,000. Th e fu ll costs sh ou ld con sider sta ff
tim e for m on itor in g, in sta llin g r em edia tion
a n d th e costs of th e detector s. It is th en lik ely
th a t th is figu r e w ill in cr ea se by 20-30 per cen t.
It is pr oblem a tic to su ggest a n over a ll va lu e
for la r ger com pa n ies a s deta ils a r e n eeded
a bou t th e n a tu r e of th e site(s). A fu r th er
stu dy is pla n n ed to ta k e pla ce in th is a r ea .
Th e fin a l cost w ill of cou r se depen d on th e
n u m ber a bove th e a ction level. In itia l wor k by
som e a u th or ities su ggest th a t th is m ay be a s
h igh a s 14 per cen t (Dixon et a l., 1996). Th e
possible r a n ge of costs is qu ite w ide w ith ou r
va lu e bein g a con ser va tive on e.
10
Conclusions
5
22
20
to
19
15
.5
12
to
14
to
12
to
.4
9
.9
9
.9
9
.4
99
10
to
5
7.
to
5
to
5
2.
[ 198 ]
9.
49
7.
99
4.
49
2.
to
0
Dos e from Radon in mSvs
9
0
F r om ou r stu dies w ith N HS pr oper ties in a n
a ffected a r ea we con clu de:
1 Th er e a r e n o r a ised levels in w a r d a r ea s.
Th is m ay in pa r t be du e to th e r ela tively
la r ge volu m e of th ese r oom s.
A.R. De nman and
Paul S. Phillips
Wo rkplac e rado n in
No rthampto nshire
Enviro nme ntal Manage me nt
and He alth
9 / 5 [1 9 9 8 ] 1 9 4 –1 9 9
2 Ra ised r a don levels a r e ver y loca lised.
Som etim es on ly on e of a n a dja cen t pa ir of
r oom s is a ffected.
3 Ra don gives m or e dose to m or e sta ff th a n
u se of X-r ays a n d isotopes for th er a py a n d
dia gn osis.
4 Th e dose r eceived by sta ff fr om r a don (2024.49m Sv – F igu r e 3) is fa r h igh er th a n
expected a n d sw ift r em edia l a ction w a s
essen tia l.
5 For th e tota l N HS sta ff, cu r r en t r isk estim a tes su ggest th a t r a don in th e wor k pla ce
gives r ise to 0.13 lu n g ca n cer s per a n n u m
(of wh ich 13 per cen t wou ld occu r in sta ff
wor k in g in a r ea s of h igh r a don a n d so
cou ld be avoided), com pa r ed w ith a n a tu r a l in ciden ce of six lu n g ca n cer s.
6 On ce r em edia ted, it is essen tia l th a t n o
str u ctu r a l ch a n ges ta k e pla ce in bu ildin gs
u n til a n im pa ct a ssessm en t on th e r edu ction system s ta k es pla ce.
7 Per iodic testin g sh ou ld occu r to en su r e
th a t th e r em edia tion system is still effective (N a ism ith , 1997).
References
Br ow n , L., Cliff, K.D. a n d Wr ixon , A.D. (1981),
“N a tu r a l r a dia tion exposu r e in door s”, R a d iol.
Prot. B u ll., N o. 41, pp. 9-13.
Bu ildin g Resea r ch E sta blish m en t (1992), R a d on
S u m ps: A B R E Gu id e to R a d on R em ed ia l M ea su res in Ex istin g B u ild in gs, BRE Book sh op,
Ga r ston , BR227.
Den m a n , A.R. (1994), “Th e sign ifi ca n ce of r a ised
r a don levels in N HS pr oper ties in N or th a m pton sh ir e”, R a d ia tion Protection Dosim etr y,
Vol. 54 N o. 1, pp. 65-8.
Den m a n , A.R. a n d P a r k in son , S. (1996), “E stim a tes of r a dia tion dose to N a tion a l Hea lth
Ser vice wor k er s in N or th a m pton sh ir e fr om
r a ised r a don levels”, T h e B r itish J ou r n a l of
R a d iolog y, Vol. 69, pp. 72-5.
Dixon , D.W., Goodin g, T.D. a n d McCr ea dySh ea , S.
(1996), “E va lu a tion a n d sign ifi ca n ce of r a don
exposu r es in Br itish wor k pla ce”, En viron m en t In ter n a tion a l, Vol. 22 N o. 51, pp. 1079-82.
Hea lth a n d Sa fety Com m ission (1988), A pprov ed
Cod e of Pra ctice – Pa r t 3. Ex posu re to R a d on ;
T h e Ion isin g R a d ia tion s R egu la tion s, HMSO,
Lon don .
Hea lth a n d Sa fety E xecu tive (1985), T h e Ion isin g
R a d ia tion s R egu la tion s, (S I (1985) 1333),
HMSO, Lon don .
Hea lth a n d Sa fety E xecu tive (1992), T h e M a n a gem en t of Hea lth a n d S a fety a t Work R egu la tion s, (S I (1992) 2051), HMSO, Lon don .
Ken da ll, G.M., Miles, J .C.H., Cliff, K.D., Gr een ,
B.M.R., Mu ir h ea d, C.R., Dixon , D.W., Lom a s,
P.R. a n d Goodr idge. S.M. (1994), “E xposu r e to
r a don in UK dwellin gs”, Ch ilton , N RP B-R”&”,
HMSO, Lon don .
Lu bin , J.H. a n d Boice, J.D. J r (1997), “Lu n g ca n cer
r isk fr om r esiden tia l r a don : m eta -a n a lysis of
eigh t epidem iologic stu dies”, J ou r n al of th e
N ation al Can cer In stitu te, Vol. 89 No. 1, pp. 49-57.
N a ism ith , S. (1997), “Du r a bility of r a don r em edia l
a ction s”, R a d ia tion Protection Dosim etr y,
Vol. 71 N o. 3, pp. 215-18.
N a tion a l Ra diologica l P r otection Boa r d (1992),
R a d on A ffected A rea s: Der b ysh ire, N or th a m pton sh ire a n d S om erset, Docu m en ts of th e
N RP B, Vol. 3 N o. 4, pp. 19-28.
N a tion a l Ra diologica l P r otection Boa r d (1993),
Estim a tes of la te ra d ia tion r isk s to th e UK
popu la tion , Docu m en ts of th e N RP B, Vol. 4
N o. 4, pp. 15-57.
Sn ih s. J .O. (1992), “Swedish r a don pr ogr a m m e”,
R a d ia tion Protection Dosim etr y, Vol. 42 N o. 3,
pp. 177-84.
Wr ixon , A.D., Gr een , B.M.R., Lom a s, P.R., Miles,
J.C.H., Cliff, K.D., F r a n cis, E.A., Dr iscoll,
C.M.H., J a m es, A.C. a n d O’Rior da n , M.C. (1988),
“Natu r a l r a diation exposu r e in UK dwellin gs”,
Ch ilton , NRPB-R190, HMSO, Lon don .
[ 199 ]
A.R. Denman
Me dic al Physic s De partme nt, No rthampto n Ge ne ral Ho spital, Clifto nville ,
No rthampto n, UK
Paul S. Phillips
Sc ho o l o f Enviro nme ntal Sc ie nc e , Ne ne Co lle ge o f Highe r Educ atio n, Park
Campus, No rthampto n, UK
Northamptonshire is classifi ed
as a radon affected area, with
greater than 1 per cent of
domestic dwellings being
above the UK Action Level of
200Bq m–3 . Workplace radon
is also a health risk in
Northamptonshire, with a
signifi cant number of premises
being predicted to be above
this Action Level (400Bq m–3 ).
After an extensive survey in
National Health Service
premises, using track etch
detectors and real time monitoring systems, it was found
that certain staff were receiving very high doses – up to
around 20mSv. The annual
collective dose from radon, in
the rooms with elevated levels,
was 285mSv, an average of
4.45mSv. After remediation of
the rooms the average dose
fell to 0.5mSv. The average
cost of radon remediation in
National Health Service
premises was £3,950 per
location. This compares to a
value of £1,953 for locations
in schools in Northamptonshire. It is possible that remediation costs for the majority
of small to medium enterprises
in the country will, on our
conservative estimate of 6 per
cent being above the Action
Level, be in the region of
£1,460,000. Further monitoring of workplace radon is
taking place across the county
in an attempt to determine
more accurately the full extent
of the problem.
Enviro nme ntal Manage me nt
and He alth
9 / 5 [ 1998] 1 9 4 –1 9 9
© MCB Unive rsity Pre ss
[ ISSN 0956-6163]
[ 194 ]
Introduction
Ra don is a n a tu r a lly occu r r in g r a dioa ctive
ga s for m ed in th e decay ser ies of u r a n iu m .
Th e on ly isotope of r a don n or m a lly a bu n da n t
en ou gh to ca u se a h ea lth pr oblem is 222Rn .
Th is isotope is for m ed by th e decay of 238U. It
h a s a h a lf life of 3.82 days a n d decays in to
218Po, wh ich in tu r n decays in to 214P b, 214Bi
a n d 214Po. Th ese fou r r a dion u clides a r e ca lled
r a don da u gh ter s or pr ogen y a n d ca n be fou n d
a tta ch ed to a er osol pa r ticles in in door a ir.
Th e isotopes 222Rn , 218Po a n d 214Po a r e a ll
a lph a pa r ticle em itter s; th ese pa r ticles r esu lt
in ver y loca lised en er gy deposition in livin g
tissu e. Th e 222Rn isotope pr ovides th e la r gest
con tr ibu tion (50 per cen t) to th e tota l r a dia tion dose r eceived by th e gen er a l UK popu la tion – 2.6 m illiSiever ts (m Sv).
Th e sta n da r d u n it of a ctivity is th e
Becqu er el (Bq) – on e n u clea r disin te gr a tion
per secon d. Activity con cen tr a tion s a r e
qu oted a s becqu er els per cu bic m etr e (Bq
m –3). Th e u n it for dose equ iva len t is th e
Siever t (Sv). In stu dies on low dose r a dia tion
it is u su a l to give doses in m illiSiever ts
(m Sv).
In th is pa per we r epor t r esu lts fr om a
deta iled su r vey ca r r ied ou t in N a tion a l
Hea lth Ser vice (N HS) pr em ises in N or th a m pton sh ir e, a cou n ty in th e Midla n ds of E n gla n d, a n d com pa r e r em edia tion costs w ith
oth er wor k pla ces.
Radon in buildings
Th er e a r e a n u m ber of sou r ces for r a don in
bu ildin gs. Th ese in clu de: ou tside a ir, w a ter
su pplies, bu ildin g m a ter ia ls a n d th e gr ou n d
u n der th e bu ildin g. Over a ll, th e m ost sign ifi ca n t sou r ce is th e gr ou n d u n der th e bu ildin g.
Ra don in ou tside a ir in th e UK is fou n d in
ver y low levels, w ith a m ea n of 4Bq m –3
(Wr ixon et a l., 1988) a n d it is u n lik ely to lea d
to eleva ted levels of in door r a don .
Ra don en ter s bu ildin gs via cr a ck s in con cr ete floor s, th r ou gh ga ps in su spen ded
wooden floor s a n d via ser vice poin ts. Th e
r ea son for th e en tr y is th a t th e a tm osph er ic
pr essu r e is lower in door s th a n ou tdoor s. Air
w ill fl ow in to a n or m a l UK dom estic bu ildin g
a t a r ou n d 1 ch a n ge per h ou r a n d a r ou n d 1 per
cen t of th a t w ill com e fr om soil ga s.
Th e m ea n UK r a don con cen tr a tion in
dwellin gs is n ea r to 20Bq m –3 (Br ow n et a l.,
1981). Alth ou gh th e m ea n va lu e is low th er e
a r e a sign ifica n t n u m ber of dwellin gs over
1,000Bq m –3 or m or e. Ra don levels ca n va r y
m a r k edly fr om n igh t to day (F igu r e 1) a n d
a lso fr om sea son to sea son . In deed, sea son a l
cor r ection fa ctor s m u st be a pplied to ever y
va lu e deter m in ed to give a tr u e r epr esen ta tion of a n aver a ge va lu e over a yea r.
Th e bu ildin g r esea r ch esta blish m en t (BRE )
h a s u n der ta k en a su r vey of th e va r iou s
m ea n s to r em edy eleva ted r a don levels in
bu ildin gs a n d h a s pu blish ed its fin din gs, e.g.
BRE (1992)
Radon af fected areas
In 1990 th e N a tion a l Ra diologica l P r otection
Boa r d (N RP B) r ecom m en ded th a t th e Action
Level for r a don in existin g h om es be 200Bq
m –3, aver a ged over a yea r. P a r ts of th e cou n tr y
w ith a 1 per cen t, or gr ea ter, pr oba bility of
h om es bein g a bove th is level a r e r e ga r ded a s
a ffected a r ea s. Th e N RP B a dvised th a t Cor n w a ll a n d Devon sh ou ld be r e ga r ded a s su ch in
1990. In 1992, Der bysh ir e, N or th a m pton sh ir e
a n d Som er set (N a tion a l Ra diologica l P r otection Boa r d, 1992) wer e sim ila r ly cla ssified.
For a cou n ty, wh ich is a n a ffected a r ea , a
r a don m a p is pr odu ced th a t sh ow s a r ea s w ith
< 1 per cen t, 1-3 per cen t, 3-10 per cen t a n d > 30
per cen t of h om es bein g a bove th e a ction
level, th is fa cilita tes a ction by th e a ppr opr ia te a u th or ities, via bu ildin g r e gu la tion s.
F igu r e 2 con ta in s in for m a tion a bou t th e
per cen ta ge of h om es in N or th a m pton sh ir e
a bove th e a ction level.
A.R. De nman and
Paul S. Phillips
Wo rkplac e rado n in
No rthampto nshire
Radon and geology
E leva ted r a don levels ca n be equ a ted w ith th e
u n der lyin g geology a n d in pa r ticu la r th e
con cen tr a tion of 226Ra , th e pr ecu r sor of 222Rn ,
in r ock s a n d soil. E leva ted levels of 226Ra
sh ou ld lea d to h igh levels of 222Rn in soil ga s.
It m u st a lso be r em em ber ed th a t soil per m ea bility is a n oth er im por ta n t fa ctor.
N or th a m pton sh ir e is a n a r ea of sedim en ta r y J u r a ssic r ock s. Th e h igh est r e gion s of
r a don pr odu ction a r e fou n d on N or th a m pton
sa n d ir on ston e, u pper Lin coln sh ir e
Enviro nme ntal Manage me nt
and He alth
9 / 5 [1 9 9 8 ] 1 9 4 –1 9 9
Figure 1
Variatio ns in indo o r rado n le ve ls in a NHS ro o m in No rthampto n
Radioactivity/Bq m –3
2400
2000
1600
1200
800
6.30 Tue
10.30 Tue
2.30 Tue
22.30 Mon
18.30 Mon
14.30 Mon
6.30 Mon
10.30 Mon
2.30 Mon
22.30 Sun
18.30 Sun
14.30 Sun
6.30 Sun
10.30 Sun
2.30 Sun
22.30 Sat
18.30 Sat
14.30 Sat
6.30 Sat
10.30 Sat
2.30 Sat
22.30 Fri
18.30 Fri
0
14.30 Fri
400
Time of day
Figure 2
Pe rc e ntage o f ho me s, in No rthampto nshire , abo ve the ac tio n le ve l
Key
1-3
3-10
Corby
10-30
Kettering
Wellingborough
Daventry
Northampton
lim eston e, gla cia l sa n d a n d gr avel. Th e
ir on ston e con ta in s ph osph or u s, wh ich is
often a ssocia ted w ith u r a n iu m .
Radon and workplace legislation
E xposu r e of wor k er s to r a don is gover n ed by
th e Ion isin g Ra dia tion s Re gu la tion s 1985
(Hea lth a n d Sa fety E xecu tive, 1985), a n d th e
Hea lth a n d Sa fety Com m ission h ave issu ed
a n Appr oved Code of P r a ctice cover in g r a don
(Hea lth a n d Sa fety Com m ission , 1988). Hea lth
a n d Sa fety execu tive a dvice is th a t em ployer s
in a ffected a r ea s a r e r equ ir ed by th e Ma n a gem en t of Hea lth a n d Sa fety a t Wor k Re gu la tion s 1992 (Hea lth a n d Sa fety E xecu tive, 1992)
to m a k e a r isk a ssessm en t a bou t r a don by
testin g th eir pr em ises.
Th e N RP B h ave a dvised th a t th e a ction
level for dom estic pr em ises be 200Bq m –3 a n d
400Bq m –3 for wor k pla ces. At levels a bove 400
in wor k pla ces, th e Ion isin g Ra dia tion s Re gu la tion s a r e deem ed to a pply a n d th e Hea lth
a n d Sa fety E xecu tive m u st be n otified. Room s
w ith levels over 1,000Bq m –3 a r e Con tr olled
Ar ea s a n d r equ ir es a ction , u n der Re gu la tion s, to lim it dose.
Th is stu dy u ses th e best cu r r en t estim a tes
to r ela te r a don exposu r e to dose r eceived. It
w a s a ssu m ed th a t 126k Bq h –1 m –3 w a s equ iva len t to 1m Sv. Th is fa ctor w a s der ived fr om
fa ctor s in th e A pprov ed Cod e of Pra ctice
(Hea lth a n d Sa fety Com m ission , 1988)
Radon: a human carcinogen?
Stu dies w ith m in er s exposed to r a ised levels
of wor k pla ce r a don , a n d its pr ogen y, h ave
fou n d th a t exposu r e in cr ea ses th e r isk of lu n g
ca n cer. Th e N RP B h ave r eviewed 11 stu dies
th a t pr odu ce over wh elm in g eviden ce th a t
r a don h er e is a h u m a n ca r cin ogen (N a tion a l
Ra diologica l P r otection Boa r d, 1993).
N u m er ou s ca se-con tr olled stu dies h ave
been la u n ch ed to dir ectly a ssess th e lu n g
ca n cer r isk fr om in door r a don . Som e stu dies
r epor t positive or wea k ly positive fi n din gs,
oth er s r epor t n o in cr ea sed r isk a t a ll.
In a n a ttem pt to pr ovide m or e in for m a tion
a r ecen t m eta -a n a lysis of eigh t ca secon tr olled stu dies w a s ca r r ied ou t (Lu bin a n d
Boice, 1997). Th e stu dy con clu des th a t th e r isk
fr om in door r a don is in lin e w ith th a t wh ich
h a s been pr oposed on th e ba sis of stu dies
w ith m in er s a n d th a t it is a ca r cin ogen in th e
h om e a n d th e wor k pla ce.
Tow ces ter
Materials and methods
Source: NRPB
Ra don is a n a lph a em itter, a s a r e two of its
sh or t-lived pr ogen y. Th e m eth od for detection
[ 195 ]
A.R. De nman and
Paul S. Phillips
Wo rkplac e rado n in
No rthampto nshire
Enviro nme ntal Manage me nt
and He alth
9 / 5 [1 9 9 8 ] 1 9 4 –1 9 9
for gen er a l su r vey wor k is a sm a ll r a don
diffu sion ch a m ber h ou sin g a pla stic a lph a tr a ck detector (Den m a n , 1994). Th is pr ovides
a m ea su r e of th e tota l r a don exposu r e over
th e m ea su r em en t per iod. It is th en possible to
ca lcu la te th e aver a ge r a don con cen tr a tion
over th e m ea su r em en t per iod.
To en su r e th a t th e r espon se is little a ffected
by diu r n a l a n d oth er tim e va r ia tion s in
r a don , th e detector s wer e left in position for
on e to th r ee m on th s. Tim e-aver a ged va lu es
wer e ca lcu la ted u sin g N RP B va lu es for sea son a l cor r ection fa ctor s.
Hou r ly m ea su r em en ts wer e m a de in r oom s
w ith eleva ted r a don levels th a t displayed
m a r k ed va r ia tion s (F igu r e 1). Th is occu r r ed
over a per iod of on e to fou r week s u sin g a
dir ect r ea din g RAD seven m eter (Den m a n
a n d P a r k in son , 1996). Th is a ctively pu m ps a ir
sa m ples in to a m ea su r in g ch a m ber. Sta ff
wer e a sk ed to fill in a qu estion n a ir e to in dica te h ow m a n y h ou r s th ey spen t in ea ch r oom
in a n a ttem pt to estim a te th e occu pa n cy
fa ctor. Th e r a dia tion dose to sta ff cou ld th en
be ca lcu la ted, a n d expr essed a s a n effective
r a dia tion dose u sin g th e r ela tion th a t 1m Sv is
equ a l to 126k Bq m –3 h ou r s.
Th e a ccepted pr otocol for r a don m ea su r em en t in th e wor k pla ce is to position detector s
in a selection of gr ou n d fl oor r oom s ch osen to
r eflect th e n or m a l occu pa n cy pa tter n of th e
bu ildin g. In sm a ll pr em ises, a detector is
pla ced in ea ch of th e two m ost fr equ en tly
occu pied r oom s. In la r ge bu ildin gs on e
sh ou ld be deployed for a t lea st ever y 100m 2 of
floor spa ce. In ver y la r ge, open bu ildin gs on e
sh ou ld be u sed for ever y 500m 2 of floor a r ea .
Results
N or th a m pton sh ir e is a n a ffected a r ea a n d
eleva ted levels of in door wor k pla ce r a don a r e
to be expected. Th e r esu lts for distr icts a n d
bor ou gh s in N or th a m pton sh ir e a r e to be
fou n d in Ta ble I. In clu ded in Ta ble I a r e aver a ge r a don va lu es in h ou sin g in th e r e gion s,
Table I
Numbe r o f wo rkplac e s te ste d and the pe rc e ntage abo ve the ac tio n le ve l
District/
borough
Corby
Daventry
East Northants
Kettering
Northampton
South Northants
Wellingborough
[ 196 ]
Average radon
Number Percentage above levels in housing
tested
action level
(Bq m–3 )
37
228
80
178
184
52
95
11
9
10
16
21
10
14
38
74
63
107
55
61
66
Population
Area
(ha)
53,000
63,000
68,000
77,000
181,000
71,000
68,000
8,000
66,600
51,000
23,400
8,100
63,500
16,300
th ese su r veys a r e exten sive, ba sed on a la r ge
n u m ber of dwellin gs, a n d give a n in dica tion
of possible levels in th e wor k pla ce.
Th e qu a n tity of da ta is still r ela tively sm a ll
a n d so som ewh a t lim its th e con fi den ce th a t
ca n be pla ced on it, even so, th e r a n ge fr om 9
to 21 per cen t, clea r ly su ggests th a t th er e is a
sign ifica n t pr oblem in th e r e gion . Th ese
va lu es a r e h igh com pa r ed to th e a ppr oxim a tely 6 per cen t of th e sch ools in th e cou n ty
th a t r equ ir ed r em edia tion for wor k pla ce
r a don . Th e va lu e for sch ools is pr oba bly
r epr esen ta tive of th e sca le of th e pr oblem
a cr oss th e cou n ty. Sch ools a r e even ly spr ea d
a n d th ey r epr esen t wor k pla ces th a t differ in
size fr om th e sm a ll, som e 60 pu pils, to th e
ver y la r ge, w ith h u n dr eds of pu pils a n d la r ge
com plexes of bu ildin gs. Th e r esu lt fr om
sch ools, h owever, n eeds to be tr ea ted w ith
som e ca u tion a s m ost r oom s a r e qu ite la r ge,
bu t in bu ildin gs w ith sm a ller r oom s th e pr opor tion a bove th e lim it m ay be h igh er. Th e
per cen ta ge for N HS pr oper ties, a t 8 per cen t,
m ay be h igh er beca u se of th e sign ifica n t
n u m ber of sm a ller offices. A m or e deta iled
su r vey is u n der w ay in th e cou n ty, in a n
a ttem pt to deter m in e a m or e a ccu r a te figu r e
for th e pr opor tion a bove th e a ction level, bu t
th is w ill n ot r epor t for som e tim e yet.
Ra don levels ca n va r y m a r k edly even w ith in
r ela tively sm a ll a r ea s. Th e va lu es for th e a r ea
cover ed by Nor th a m pton Bor ou gh a r e pr esen ted a ccor din g to postcode in Ta ble II.
N or th a m pton sh ir e N HS pr oper ties a r e
w ith in fou r N HS tr u sts, a n d in clu de two gen er a l h ospita ls, h ea lth cen tr es a n d r esiden tia l
h om es, th e tota l n u m ber of pr oper ties is 82.
Th e tota l sta ff n u m ber is som e 6,693 wh ole
tim e equ iva len ts. Ou r su r vey h a s to da te
m ea su r ed r a don levels in 1,038 r oom s a n d th is
h a s th e u su a l log-n or m a l distr ibu tion wh ich
is a lso r epor ted in a n u m ber of su r veys of
r esiden tia l pr em ises w ith 1 per cen t over
1,000Bq m –3 a n d 8 per cen t over th e wor k pla ce
a ction level. Typica l r ea din gs fr om a bu ildin g
w ith r a ised levels a r e fou n d in Ta ble III. Th e
r esu lts for th e distr ibu tion of r a don over a ll
pr oper ties a r e fou n d in Ta ble IV.
Table II
Variation in radon levels in c ommerc ial premises
within a borough c ounc il (Northampton), by
postc ode
Radon
(Bq m–3 )
NN1
0-99
100-199
200-399
> 400
33.6
23.5
14.3
28.6
Percentage of properties
NN2
NN3
NN4
53.3
20.0
0
26.7
56.3
18.8
15.6
9.3
75.0
4.1
8.3
12.8
NN5
50.0
25.0
6.2
17.8
A.R. De nman and
Paul S. Phillips
Wo rkplac e rado n in
No rthampto nshire
Table III
De taile d surve y o f an NHS building with raise d
rado n le ve ls
Enviro nme ntal Manage me nt
and He alth
9 / 5 [1 9 9 8 ] 1 9 4 –1 9 9
Location
Direct reading (Bq m–3 )
800
1,800
3,200
1,900
700
50
300
Reception
Interview room
Consulting room
Treatment room
Corridor
Staff toilets
Rest room
Sever a l r oom s a r e ver y sm a ll stor e r oom s
th a t a r e r a r ely en ter ed, th ese h ave been discou n ted a n d w ill n ot be r em edia ted. A tota l of
21 wor k pla ce loca tion s wer e fou n d to be over
th e lim it a n d n eedin g r em edia tion . In a ll, 11
h ave been su ccessfu lly r em edia ted a n d two
r equ ir e fu r th er wor k . Th e costs for th e
r em edia tion for loca tion s is fou n d in Ta ble V,
wh ich a lso con ta in s da ta on oth er types of
wor k pla ce loca tion s in N or th a m pton sh ir e.
Loca tion s w ith levels in excess of 550Bq m –3
wer e fitted w ith on e or m or e su m ps a n d
extr a ctor fa n s. Th e tota l cost for th ese eigh t
loca tion s w a s £39,300. Th e lowest cost for
th ese loca tion s w a s £640, h er e a sin gle su m p,
w ith fa n , w a s in sta lled to su ccessfu lly r em edia te on e sm a ll r oom .
In a n oth er ca se, wh er e th e level w a s 430Bq
m –3, th e void below th e bu ildin g w a s fitted
w ith a n im pr oved for m of pa ssive ven tila tion
a s well a s a ddition a l fa n s to a ctively expel a ir
fr om th e u n der floor void to th e exter n a l
en vir on m en t. Th is w a s con sider ed su ita ble to
br in g th e level below th a t r equ ir ed by le gisla tion . Th e cost for th is w a s £2,000.
A fu r th er two loca tion s, wh er e r a don levels
wer e ju st a bove th e lim it, wer e fitted w ith
extr a ctor fa n s on ly in th e u n der floor void,
su m ps wer e n ot deem ed n ecessa r y. Th e cost
for th ese w a s £2,150.
As soon a s a pr oblem w a s detected a Hea lth
a n d Sa fety a dviser w a s con su lted. An a ction
pla n w a s devised a n d ten der s wer e in vited
fr om com pa n ies wh o wer e on th e UK Ra don
Cou n cil’s list of a ppr oved con tr a ctor s. Rem edia l wor k w a s th en ca r r ied ou t, m ostly w ith in
Table IV
Distributio n o f rado n le ve ls in site s in NHS pro pe rtie s in No rthampto nshire
Average radon
level (Bq m–3 )
< 100
101-200
201-300
301-400
>400
Hospital A
(Northampton Sand)
Hospital B
(Upper Lias Clay)
Total of
all sites
207
37
13
8
16
130
44
19
7
5
655
184
64
39
81
a per iod of a r ou n d th r ee m on th s. On ly in on e
ca se, th a t of a n office w ith levels of 2,870Bq
m –3, w a s it n ecessa r y to eva cu a te a n d pr even t
sta ff en ter in g.
Th e a n n u a l dose fr om r a don in th e N HS
wor k pla ce h a s been estim a ted for 64 sta ff wh o
wor k in th e iden tified h ot-spots. Th e distr ibu tion is sh ow n in F igu r e 3. Th e a n n u a l tota l
collective dose for th ese sta ff fr om r a don w a s
285m Sv, a n aver a ge of 4.45m Sv. After r em edia tion th e aver a ge dose fell to 0.5m Sv.
Discussion
Sim ple estim a tes of dose to wor k er s, ba sed on
aver a ge r a don levels, ca n be m islea din g.
Ra don levels ca n va r y m a r k edly du r in g a 24
h ou r per iod (F igu r e 1) w ith th e h igh est levels
a ppea r in g ou tside of sta n da r d wor k in g h ou r s.
As occu pa n cy, on th e wh ole, decr ea ses th er e is
a r edu ction in ven tila tion w ith a n in cr ea se in
r a don con cen tr a tion . As som e or ga n isa tion s
m ay em ploy a n u m ber of sh ift wor k er s a t
n igh t tim e, wh o oper a te in a seden ta r y m a n n er, th er e m ay be con sider a bly gr ea ter doses
r eceived by th ese th a n oth er s wh o wor k du r in g th e day. Th e NHS em ploys a con sider a ble
n u m ber of n igh t wor k er s a n d th ese m ay be a t
extr a r isk . However, it is essen tia l to k n ow th e
va r ia tion s in r a don levels th r ou gh ou t a 24
h ou r per iod a s well a s th e tim e-aver a ged
levels, over pr olon ged per iods, to design a
com pr eh en sive r em edia tion pa ck a ge.
Th e N RP B in dica te th a t con tin u ou s exposu r e for 80 per cen t occu pa n cy a t 100Bq m –3
gives a n effective dose of a r ou n d 5m Sv per
yea r. In th e m a n a gem en t of h igh r a don levels
it is essen tia l to r edu ce levels a s qu ick ly a n d
effectively a s possible to th e wor k pla ce a ction
level. In cr ea sin g ven tila tion a lon e ca n r esu lt
in som e clea r a dva n ta ges. In on e r oom , w ith a
va lu e of 710Bq m –3 du r in g wor k in g h ou r s,
m er ely open in g w in dow s ca u sed th e dose to
sta ff to dr op fr om 5.0m Sv to 1.1m Sv per yea r.
Im m edia te a ction m u st be ta k en wh en a loca tion is iden tified w ith ver y eleva ted levels. In
som e ca ses it is n ecessa r y to tem por a r ily sea l
off th e r oom , or sever ely lim it a ccess, u n til
r em edia tion . In extr em e ca ses, for say ver y
sm a ll stor e r oom s, it m ay be m or e cost effective to sea l off th e r oom per m a n en tly a s th e
cost of lon g ter m r em edia tion m ay be gr ea ter
th a n th e va lu e of th e spa ce.
In som e ca ses, befor e r em edia tion , N HS
sta ff wer e r eceivin g doses well a bove 5m Sv
per yea r. Th ese doses a r e in excess of th ose
r eceived by h ospita l wor k er s wor k in g w ith
r a dia tion , su ch a s r a diogr a ph er s, r a diologists, ph ysicists a n d r a dioth er a pists.
We h ave ca lcu la ted th a t ou r pr ogr a m m e
costs a r ou n d £180,000 to a ch ieve a n a n n u a l
[ 197 ]
Ma n -Siever t r edu ction . It is in ter estin g to
com pa r e th is va lu e w ith th a t pr oposed for
dom estic pr oper ties in Sweden (Sn ih s, 1992).
Sn ih s su ggests th a t costs in Sweden a r e
a r ou n d £30,000 per Ma n -Siever t saved a n n u a lly, a t a n a ction level of 400Bq m –3. E xposu r e
in th e wor k pla ce is n ot dir ectly com pa r a ble
w ith th e h om e, a s r esiden ts a r e exposed to
r a don in th e h om e wh en levels a r e th e h igh est, wh ile m a n y wor k er s a r e exposed to th e
lowest r a don levels if wor k in g 9 a .m . to 5 p.m .
Th e volu m e of a r oom is a lso a cr itica l fa ctor,
ver y la r ge a r ea s h ave a r edu ced sta ck effect
a n d ver y little u n der pr essu r e. It is difficu lt to
dir ectly com pa r e both situ a tion s bu t it ca n be
sa id th a t r em edia tion in com m er cia l
pr em ises ten ds to be sign ifi ca n tly h igh er in
cost th a n dom estic dwellin gs a s th er e a r e
often m u ltiple foci of r a don en tr y wh ich com plica tes r a don r edu ction .
Th e costs for a r a don pr ogr a m m e a r e
a lw ays gr ea ter th a n th e m er e costs of r em edia tion . We qu ote a va lu e of £43,450 for r em edia tion wor k bu t th is n e glects th e costs of detector s a s well a s sta ff tim e. We estim a te th a t on
com pletion th e tota l cost w ill be a r ou n d
£98,000 for a ll 21 loca tion s. For ou r stu dy,
r em edia tion costs a r e 76.5 per cen t of tota l
costs, th e oth er s a r e; sta ff tim e (9.2 per cen t)
a n d detector s (14.3 per cen t).
Th e da ta th a t a r e ava ila ble for r em edia tion
costs a r e in for m a tive. Th ose for r em edia tion
A.R. De nman and
Paul S. Phillips
Wo rkplac e rado n in
No rthampto nshire
Enviro nme ntal Manage me nt
and He alth
9 / 5 [1 9 9 8 ] 1 9 4 –1 9 9
Table V
Co sts, so far, fo r re me diatio n in so me No rthampto nshire wo rkplac e s
NHS
11
Number of locations
Total cost (£)
43,450
Average cost
per location (£)
3,950
Range (£)
640-13,865
Schools
Libraries
Social service
Police
21
41,031
2
1,546
12
20,955
3
1,908
1,953
259-8,500
773
568-978
1,746
563-6,362
636
589-703
Figure 3
Estimate d do se s fo r 6 4 staff in lo c atio ns with raise d rado n le ve ls
Number of Staff
30
25
20
15
in sch ools a r e pa r ticu la r ly u sefu l to com pa r e
w ith th ose fr om th e N HS. Th e costs com e
fr om r em edia tion in 21 sch ools ou t of th e
a ppr oxim a tely 360 tested th r ou gh ou t th e
cou n ty. Th e costs a r e h igh er in th e N HS pr oper ties beca u se of a sm a ll n u m ber of situ a tion s
th a t pr oved pa r ticu la r ly difficu lt to dea l w ith ,
beca u se of m u lti-foca l en tr y poin ts. Th e costs
for th e sch ools a ppea r to be m or e r epr esen ta tive of “th e aver a ge situ a tion ” fou n d th r ou gh ou t th e cou n ty for sm a ll to m ediu m en ter pr ises (u p to 250 em ployees), especia lly th ose
w ith la r ger r oom s.
Th e a r ith m etic m ea n of £1,953 for sch ools
com pa r es to a fi gu r e of a r ou n d £1,110 th a t ca n
be der ived fr om da ta pr ovided by th e N RP B
for r em edia tion of dom estic pr oper ties, w ith
su m ps (Ken da ll et a l., 1994). Ou r da ta for
sch ools spa n th e per iod 1993 to 1996 a n d th e
da ta fr om th e N RP B a r e u p u n til m id-1994.
Du r in g th a t tim e r em edia tion costs h ave
h a r dly r isen , so th e figu r e qu oted by th e
N RP B w ill still sta n d, to a good a ppr oxim a tion , today.
With in N or th a m pton sh ir e th er e a r e
a ppr oxim a tely 19,000 en ter pr ises, th a t fa ll
in to th e follow in g ca te gor ies:
• 15,000 1 – 10 em ployees;
• 4,000 11 – 199 em ployees;
• 100 > 200 em ployees;
Wor k pla ces in th e fir st ca te gor y sh ou ld h ave
r em edia tion costs a ssocia ted m or e closely
w ith dom estic a n d th ose in th e secon d w ith
sch ools a n d so it is possible to su ggest a n
a ppr oxim a te figu r e for a lik ely cost to th e
cou n ty to r em edia te in th ese types of bu sin ess, a ssu m in g th a t 6 per cen t r equ ir e r em edia tion . Th e figu r e is in th e r e gion of
£1,460,000. Th e fu ll costs sh ou ld con sider sta ff
tim e for m on itor in g, in sta llin g r em edia tion
a n d th e costs of th e detector s. It is th en lik ely
th a t th is figu r e w ill in cr ea se by 20-30 per cen t.
It is pr oblem a tic to su ggest a n over a ll va lu e
for la r ger com pa n ies a s deta ils a r e n eeded
a bou t th e n a tu r e of th e site(s). A fu r th er
stu dy is pla n n ed to ta k e pla ce in th is a r ea .
Th e fin a l cost w ill of cou r se depen d on th e
n u m ber a bove th e a ction level. In itia l wor k by
som e a u th or ities su ggest th a t th is m ay be a s
h igh a s 14 per cen t (Dixon et a l., 1996). Th e
possible r a n ge of costs is qu ite w ide w ith ou r
va lu e bein g a con ser va tive on e.
10
Conclusions
5
22
20
to
19
15
.5
12
to
14
to
12
to
.4
9
.9
9
.9
9
.4
99
10
to
5
7.
to
5
to
5
2.
[ 198 ]
9.
49
7.
99
4.
49
2.
to
0
Dos e from Radon in mSvs
9
0
F r om ou r stu dies w ith N HS pr oper ties in a n
a ffected a r ea we con clu de:
1 Th er e a r e n o r a ised levels in w a r d a r ea s.
Th is m ay in pa r t be du e to th e r ela tively
la r ge volu m e of th ese r oom s.
A.R. De nman and
Paul S. Phillips
Wo rkplac e rado n in
No rthampto nshire
Enviro nme ntal Manage me nt
and He alth
9 / 5 [1 9 9 8 ] 1 9 4 –1 9 9
2 Ra ised r a don levels a r e ver y loca lised.
Som etim es on ly on e of a n a dja cen t pa ir of
r oom s is a ffected.
3 Ra don gives m or e dose to m or e sta ff th a n
u se of X-r ays a n d isotopes for th er a py a n d
dia gn osis.
4 Th e dose r eceived by sta ff fr om r a don (2024.49m Sv – F igu r e 3) is fa r h igh er th a n
expected a n d sw ift r em edia l a ction w a s
essen tia l.
5 For th e tota l N HS sta ff, cu r r en t r isk estim a tes su ggest th a t r a don in th e wor k pla ce
gives r ise to 0.13 lu n g ca n cer s per a n n u m
(of wh ich 13 per cen t wou ld occu r in sta ff
wor k in g in a r ea s of h igh r a don a n d so
cou ld be avoided), com pa r ed w ith a n a tu r a l in ciden ce of six lu n g ca n cer s.
6 On ce r em edia ted, it is essen tia l th a t n o
str u ctu r a l ch a n ges ta k e pla ce in bu ildin gs
u n til a n im pa ct a ssessm en t on th e r edu ction system s ta k es pla ce.
7 Per iodic testin g sh ou ld occu r to en su r e
th a t th e r em edia tion system is still effective (N a ism ith , 1997).
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