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Effectiveness of secondary
radon protection in
Northamptonshire houses
Paul S. Phillips
Secondary radon
protection
337
University College Northampton, Northampton, UK
Julia D. Fraser
East Northamptonshire District Council, Northamptonshire, UK and
Antony R. Denman
Northampton General Hospital, Northampton, UK
Keywords Radon, Housing, United Kingdom
Abstract Northamptonshire is classified as a radon affected area, with greater than 1 per cent
of houses being above the UK action level of 200Bq/m±3. New houses, in areas where >10 per
cent are above the action level, have to have primary protection of a radon-proof membrane and
secondary measures such as a non-activated radon sump. New houses, in areas where 3-10 per
cent are above the action level only need the secondary measures. This research calls into
question the effectiveness of this strategy. The use of radon potential maps, rather than radon in
building maps, would have demonstrated that radon ``hot spots'', where a very high percentage
of houses are over the action level, can occur on a range of geology. One estate, at Higham
Ferrers, had 35 per cent over the action level, even though it had been classified as only requiring
secondary measures. The reluctance of occupiers in the UK to instigate monitoring and
remediation means that very few will have their house tested for radon and activate the sump, by
fitting a fan, if that is required. This paper provides arguments that support the view that it
would be more effective to have primary and secondary measures introduced in all new houses in
radon affected areas.
Introduction
Radon (222Rn) is a naturally occurring radioactive gas which decays into a
series of isotopes known as radon progeny, of which the most significant are
218
Po, and 214Pb. These, if inhaled, can be retained in the lung and deliver a
dose to its walls by alpha particle emission. The potential health hazards from
exposure to radon and its progeny are well documented; recent studies have
demonstrated that there is a significant risk from the dose provided by radon
and its progeny even at the levels found in domestic dwellings (Lubin and
Boice, 1997; Darby et al., 1998). Cost-effective remediation for radon and its
progeny in the built environment (Denman and Phillips, 1998a) must therefore
be a priority for a range of national agencies in an attempt to limit dose to
occupants (Denman et al., 1999).
In the UK, the National Radiological Protection Board (NRPB) established in
1990 an action level of 200Bq/m±3 for domestic properties. The NRPB has also
declared a number of affected areas, where more than 1 per cent of the housing
stock have radon levels over the action level. Northamptonshire is such an area
(NRPB, 1992), with 6.3 per cent of houses above the action level and in some
Environmental Management and
Health, Vol. 11 No. 4, 2000,
pp. 337-351. # MCB University
Press, 0956-6163
EMH
11,4
338
areas, up to 21 per cent of workplaces above that action level of 400 Bq m-3
(Denman and Phillips, 1998b)
Guidance on radon protection
In 1991, the Building Research Establishment (BRE), produced guidance
(revised in 1992) on protective measures against radon in new homes (Building
Research Establishment, 1992). They point out that requirement C2 of Schedule
1 of the Building Regulations for England and Wales (HMSO, 1991) say that:
precautions shall be taken to avoid danger to health and safety caused by substances found
on or in the ground to be covered by the building
The Approved Document (Department of the Environment and the Welsh
Office, 1992) includes radon in the contaminant list because of the increased
risk of lung cancer to those who live in buildings with elevated levels of the gas.
For houses or extensions to be erected in a range of affected areas, including
Northamptonshire, precautions against radon may be necessary. From
February 1993, the guidance applied to new houses in Northamptonshire.
There are two main methods of achieving radon protection. First, the
passive system, known as primary protection. This consists of an airtight and
radon-proof barrier across the whole of the building including the floor and the
walls. The barrier is generally a membrane of 300 micrometer (1,200 gauge)
polythene sheet. Some radon diffusion will probably occur through the sheet
but, as most gas entry is through cracks, this pathway is negligible. For this
system to be effective, it is vital that the radon-proof membrane is not damaged
during construction and that particular attention is given to jointing to prevent
pathways for gas ingress.
Second, the active system, known as secondary protection. This system
consists of a powered radon-extract system as an integral part of the services of
the house. This will incur running and maintenance costs for the life of the
building. Normally, subfloor depressurisation is used to remove radon rich air
from beneath the house and to vent it to external air. This is provided by the
use of a sump positioned centrally under the house and constructed so that the
pipe to external air is not blocked when further building work occurs. The
system is powered by a fan, often mounted on the external wall.
A study on the effectiveness of remedial measures in 943 UK homes has
been published (Naismith et al., 1998). The National Radiological Protection
Board (NRPB) has been running a programme to test the effectiveness of
remedial measures in homes with high radon. Radon sumps were found to be
the most effective remedial method with the highest reduction factor (Table I).
Since BRE guidance has been implemented, new dwellings in
Northamptonshire, in areas with a greater than 10 per cent of houses likely to
be above the action level, have to have full radon protection of primary and
secondary measures (Figure 1). New dwellings in Northamptonshire, in areas
where the risk of houses being above the action level is between 3 and 10 per
cent, have only to have the secondary measure (Figure 1). In both situations,
Remedial measure
Sump, major contractor, post-war house
Sump, major contractor, pre-war house
Sump, local builder, post-war house
Sump, local builder, pre-war house
Sump, DIY, post-war house
Sump, DIY, pre-war house
Positive ventilation, two-storey house
Positive ventilation, bungalow
Additional permanent ventilation of house, no
additional sealing
Additional permanent ventilation of house,
with additional sealing
Mechanical ventilation of underfloor space
Natural ventilation of underfloor space
Sealing of cracks, entry points
Geometric mean of
reduction factors
Percentage of houses
reduced below the
action level
17
9
11
6
7
4
1.9
3.7
95
77
82
70
77
64
42
63
1.5
49
2.4
2.8
1.9
1.7
60
54
53
41
Source: Naismith et al., 1998
builders of new houses do not have to install a fan to drive the secondary
protection. It is left to the householder to arrange monitoring to determine
whether or not the house is above the action level; if this is so they need to fit a
fan to activate the sump and bring radon levels below 200Bq/m±3.
The BRE make clear that further research may cause the list of areas that
require precautionary measures to be revised. The central role of the local
authority in enforcing Building Regulations is recognised and they will be able
to confirm the status of a given area to an enquirer. The BRE designated areas
in Northamptonshire are based upon information provided by the NRPB,
except that the area covered by the guidance is somewhat larger than that
indicated by the NRPB maps. This is because the guidance is based on
administrative areas under local authority control; this is the Parish which is
part of a District or Borough in a typical English county. East
Northamptonshire (Figure 1) contains 60 parishes, 33 of which are in affected
areas that only require active measures in new houses (3-10 per cent above
action level), while 27 require no measures (less than 3 per cent above the
action level).
Radon maps
Various types of area boundaries are used in the analysis of radon data and the
production of a range of maps. Administrative boundaries are one class, as are
geological boundaries or divisions such as 5km grid squares; these were used
by the NRPB to delineate affected areas. Using such areas simplifies
administrative action as it is easier to determine whether new houses require
radon protection by using their address (postcode) rather than using map
Secondary radon
protection
339
Table I.
Effectiveness of
remedial measures in
UK houses
EMH
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340
Figure 1.
Areas of
Northamptonshire
where primary and
secondary systems are
required in new houses
coordinates. Geological boundaries are, however, potentially more useful as
likely radon levels are strongly linked to underlying geology. They are,
however, difficult to use as the geology of an area may be much more complex
than first appears, with marked variations in a small area. It may be that those
radon ``hot-spots'', which produce houses well over the action level, may be
overlooked by the inexperienced user of such maps. Two variations of maps
may be used when delineating radon-prone areas. One type shows radon
potential for a standard house or national mix of houses, the other shows how
radon would vary for the typical housing stock for that area. When NRPB
measurement of radon in houses is studied in relation to underlying geology,
they are normalised to a standard mix of houses (Miles, 1998).
Radon and geology
Northamptonshire is a county of essentially sedimentary rocks, mainly Lower
to Middle Jurassic (Sutherland and Sharman, 1996). Highest radon levels are
found on Upper Lincolnshire Limestone, Northampton Sand Ironstone,
Marlstone Rock Bed and Glacial sand and gravel; here more than 20 per cent of
houses can be over the action level (Table II). Lowest radon levels are found on
Hazard group
Low
Slight
% houses above
action level
20
Secondary radon
protection
Geological formations and drift deposits
Clays: Alluvial, Oxford, Blisworth & Rutland
Formation
Kellaways Clay, Blisworth Limestone, Rutland
Formation, Upper Lias Clay, River gravels, Boulder
Clay
Kellaways Sand, Cornbrash, Grantham Formation,
Northampton Sand, Lower Lias Clay
Upper Lincolnshire Limestone, Northampton Sand
Ironstone, Marlstone Rock Bed, Glacial sand and gravel
Source: Sutherland and Sharman, 1996
341
Table II.
Some geological
formations and their
radon hazards in
Northamptonshire
Oxford Clay, Blisworth Clay and Rutland Formation Clay; here less than 1 per
cent of houses are over the action level (Table II). Ironstone in the county is
phosphatic and uranium is often associated with phosphorus. A layer of
phosphatic pebbles at the base of the ironstone layer has the highest uranium
levels in the geology and would be expected to generate significant radon
levels. This, allied to a high level of permeability in the rock, means that areas
of the county have raised radon levels in houses (Figure 1)
New house building in Northamptonshire is running above the national
average, with the housing stock increasing by 4.7 per cent since 1993, when
guidance was first applied for new housing. The number of existing and new
houses for the districts and boroughs of the county are shown in Table III. The
rapid rise in the number of new houses, allied to the serious radon problem,
means that this county is a suitable location for surveys concerning the efficacy
of radon precaution systems built into new houses. This survey reports on the
radon levels in new houses that were built with secondary protection measures,
after 1993, as well as the occupiers' responses to the requirement for them to
test for radon and if necessary to fit a fan to activate the sump.
District
Corby
Daventry
East Northants
Kettering
Northampton
South Northants
Wellingborough
Total
Housing stock
(1997)
No. tested for
radon
22,600
28,400
30,300
34,600
81,100
29,900
30,000
256,900
1,173
6,065
3,881
7,319
29,378
4,312
14,075
66,203
No. above action New houses built
level
(1993-1997)
24
475
212
997
1,304
223
936
4,171
960
1,990
1,540
1,390
3,450
1,800
1,070
12,200
Table III.
Housing statistics for
Northamptonshire
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342
Materials and method
Two recently constructed housing estates in East Northamptonshire were
chosen for this study as both have been constructed after 1993, when the BRE
guidance came into effect. East Northamptonshire is a District that has 33
parishes in the 3-10 per cent above action level category and 27 that are below
this level (Figure 1). One estate is in Higham Ferrers and the other in
Thrapston, both in the overall 3-10 per cent category. Information concerning
the radon levels in houses, on a smaller scale than a parish, can be obtained by
using the postcodes of the areas. The Higham Ferrers estate is in an area that,
using data available, is considered to have 9 per cent of houses over the action
level. Similarly, the Thrapston estate is in an area where 11.7 per cent of the
houses are over the action level.
The geology of the Higham Ferrers site is essentially that of the Great Oolite
Group. This contains Cornbrash, Kellaways sand and clay, Blisworth Clay and
Blisworth Limestone (Table II). Depending upon the detailed geology of the
site, the percentage of dwellings above the Action Level could range from
below 1 per cent to between 2-15 per cent (Table II). The Thrapston site is based
essentially on Oxford Clay; such underlying geology would be expected to have
less than 1 per cent of homes above the action level (Table II).
The estate in Higham Ferrers has around 100 occupied houses and in
Thrapston there are around 230 occupied houses. On each estate, houses have
been built by a number of different developers. Both estates are predominantly
detached three- and four-bedroom houses with a similar type of construction
and the results in this study only apply to such buildings. No house has a
radon-proof membrane but all have a sump which could be activated by fitting
a fan; this was confirmed by Local Authority Building Control. Building type
does affect the radon levels in the built environment and so this study yields
information that has not been distorted by a wide variety of building types
(Gunby et al., 1993).
Every house, on both estates, was contacted with an introductory letter and
a questionnaire. The occupiers were also offered a free radon test. The offer
was taken up by 99 houses from Thrapston (43 per cent response) and 34 from
High Ferrers (34 per cent response) and testing took place in June 1999. This
return rate is in line with other such radon surveys in the UK (Brannigan, 1999)
and appears to suggest that radon is not a high priority for householders even
in affected areas. The questionnaire was a mixture of open and closed nonbiased questions along with a number of more open ended questions. Members
of each household were counselled about the radon test and the importance of
not tampering with the detectors. Detectors were collected, at the same time as
the completed questionnaire, and placed into protective packaging before
sending for analysis.
Radon levels in houses were measured using alpha track (CR-39) detectors
with a six-day exposure. The NRPB protocol for siting detectors was used; one
was placed in the major bedroom and one in the main living room, away from
draughts and at suitable height from the floor. The living area and the bedroom
values are then combined using 0.55 for the bedroom value and 0.45 for the Secondary radon
living area, to reflect occupancy patterns. The results were sessionally adjusted
protection
by using the NRPB monthly seasonal correction factors for domestic premises.
NRPB suggest that using monthly correction factors will produce a standard
deviation of 0.96 from three monthly readings.
Results
Radon levels in houses
The radon levels for the 133 houses from the two estates are shown in Table
IV. Both estates are situated in an area that guidance, on radon protective
measures in new houses, suggests would have between 3 and 10 per cent of
houses above the action level. The Thrapston estate, with 5 per cent above
the action level, clearly falls into this category but this value is higher than
would be expected from a consideration of geology alone. Estates on the
Oxford Clay formation would be expected to have less than 1 per cent of
houses above the action level; this demonstrates that geological maps are at
best indicative.
The Higham Ferrers site has 35 per cent above the action level. This
remarkably high level is almost certainly due to a local radon ``hot spot''.
Although the surface geology is considered to be essentially the Great Oolite
Group, it is probably, in the area of the estate, dominated by the underlying
Lincolnshire Limestone Formation (Table II). The application of the guidance
for the construction of new houses does not take into account the need to
accurately determine the geology on the building site so as to locate local ``hot
spots''.
Radon (Bq/m-3)
0-25
26-50
51-75
76-100
101-125
126-150
151-175
176-200
201-225
226-250
251-275
276-300
301-325
351-375
376-400
401-425
% above action level
343
Number of houses
Higham Ferrers
Thrapston
0
14
4
1
0
1
2
0
1
1
1
6
2
1
0
0
35
0
16
30
18
10
13
5
2
2
0
3
0
0
0
0
0
5
Table IV.
Radon levels in new
houses from estates in
Higham Ferrers and
Thrapston, East
Northamptonshire
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344
Table V.
Occupiers' responses to
radon questionnaire
Results from the questionnaire
Question 1 ± Is radon gas a health risk? A clear majority of 68 per cent
indicated that they were aware that radon was a health risk while 23 per cent
thought it was not and 9 per cent came into the ``don't know'' category ± making
a total of 32 per cent who were unaware that it was a health risk (Table V). The
questionnaire did not elicit a response to the type of health risk posed by radon.
Initial, unpublished work by one of the authors concerning the public
understanding of the health risk posed by radon in East Northamptonshire
suggests that a significant proportion of those who are aware of the risk equate
it, correctly, with some type of cancer.
Question 2 ± Is radon a problem in East Northamptonshire? Some 33 per
cent were aware that there is a radon problem in East Northamptonshire, 59 per
cent did not know and 8 per cent said no (Table V). It must be borne in mind
that the occupiers had purchased a house that had been constructed according
to guidance and had a sump with a provision for a fan and so might have been
expected to be aware of the implications of this.
Question 3 ± Has your house been tested for radon? Some 9 per cent
answered yes to this and claimed that their house had been tested for radon, an
overwhelming 91 per cent said no (Table V). Of the 9 per cent (12 houses) who
answered yes, only two were above the action level and they had not proceeded
to remediate.
Question 4 ± Were you clearly informed by the developers about the radon
protection measure in your new house? Some 13 per cent said that they had
been so informed, 87 per cent said no (Table V). This is a key finding as
developers could be expected to inform the purchasers and so encourage them
to seek radon monitoring.
Question 5 ± What radon protection system is built into your house? Some
62 per cent said that they had ``no knowledge'', 17 per cent said ``some system'',
11 per cent said a membrane, 6 per cent said a sump that worked without a fan
and 4 per cent said ``no system'' (Table VI).
Question 6 ± From whom did you receive ``general'' advice about radon when
purchasing your house? Some 14 per cent said surveyors, 14 per cent said
developers, 3 per cent said the mortgage provider. No one claimed to receive
Question
Yes
1.
2.
3.
4.
68
33
9
13
Is radon gas a health risk?
Is radon a problem in East Northants?
Has your house been tested for radon?
Were you clearly informed by the
developers about the radon protection
measure in your house?
Response (%)
No
Don't know
23
8
91
87
9
59
±
±
advice from the estate agent, local doctor, local authority or NRPB. A clear Secondary radon
majority of 71 per cent said that no advice had been provided by any agent
protection
(Table VII).
Question 7 ± Who would you ask for advice on dealing with radon in your
house? The local District Council at 46 per cent was the preferred choice with
the County Council coming second with 22 per cent. Other organisations
345
include the NRPB, the local elected member of the District or Parish Council
and the local doctor (Table VIII).
Discussion
The BRE has been carrying out research, funded by the UK Department of the
Environment, Transport and the Regions (DETR), into radon and the built
environment since the late 1980s. Their research has resulted in the successful
development of a range of radon remedial measures (Scivyer and Woolliscroft,
1998). The use of the radon proof membrane has been a proven success, if
installed correctly. Monitoring of 423 houses in the South West of England, the
BRE has shown that the membrane was successful at preventing radon ingress
and significant at the 0.1 per cent level (Woolliscroft et al., 1994). This has also
been demonstrated in a number of other countries, (e.g. Najafi, 1998). The use of
a passive system, such as a membrane, may in itself not be sufficient in every
case and then an active system is required (Table I).
The guidance given by the BRE, on protection measures, is based upon
radon maps produced by the NRPB. These maps have been then used to predict
administrative areas (parishes) that fall into the two categories and are used by
local authority Building Control to issue guidance to those building new homes.
The simplistic use of such maps, without a detailed consideration of the
Measure
Some system
Membrane
Sump that worked without a fan
No system
No knowledge
Source of advice
Surveyors
Developers
Mortgage provider
Estate agent
Local authority
Local doctor
No advice
Percentage of occupiers
17
11
6
4
62
Table VI.
What radon protection
measure occupiers
thought was in their
house
Percentage of occupiers
14
12
3
0
0
0
71
Table VII.
Sources of general
advice on radon to
house purchasers
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346
geology of the site (Table II), can result in houses being built on a formation
that may lead to radon levels much higher than predicted ± a local radon ``hot
spot''.
The Higham Ferrers site, with 35 per cent of houses over the action level
(Table IV) is an example of this. The use of postcodes, to indicate a more likely
radon level, fails to signal the possibility of such a variation. The Thrapston
site, with 5 per cent above the action level, is actually below the level expected
for that postcode. The use of postcodes is informative as the Thrapston site is
in an area where 11.7 per cent are over the action level, yet, overall, it is in a 3-10
per cent parish. The BRE guidance, first issued in 1991, failed to take full
account of the possibility of such marked variations that can result from local
``hot spots''. With hindsight, a mechanism could have been developed so that
regular radon monitoring was required by a local authority in an attempt to
identify such ``hot spots''.
The BRE seem to consider that occupiers, in areas with a 3-10 per cent
chance of houses being above the action level, would proceed to have a radon
test and if the value was high enough to have a fan fitted so as to activate the
sump. Reduction factors, for indoor radon (geometric mean) of around 17 could
then be achieved (Table I). The present cost of having a fan fitted by a major
contractor in Northamptonshire is in the region of £150. This will incur
running costs of some £35 per annum. This stands in contrast to the present
estimated cost of some £320 for placing a radon proof membrane in a typical
three-bedroom detached house being constructed in Northamptonshire. The
present costs of having a major contractor install a sump and fan in a similar
house is in the region of £550.
For the guidance of the BRE to have any impact it needs to have a clear
mechanism whereby house purchasers are informed about the radon health
risks. It must also be made unambiguous that it is their responsibility to
instigate testing, and if required to activate the sump by fitting a fan. Since the
development and implementation of the BRE policy, research on householders'
responses to elevated levels in the built environment has called into question
the assumption that the public would instigate monitoring and remediation on
a significant scale.
In one study (1994) in the South West of England, only 3-5 per cent of those
above the action level proceeded to carry out some form of remediation (Lee
Source of advice
Table VIII.
Whom occupiers
considered a source of
reliable advice on
radon in the home
District Council
County Council
NRPB
Local councillor
Local doctor
Other, e.g. neighbour
Don't know
Percentage of occupiers
46
22
14
4
4
5
5
and MacDonald, 1994). Bradley reported, in 1996, the results of a postal survey Secondary radon
of 10,500 householders with initial levels above the action level (Bradley,
protection
1996). Of the 5,000 who replied, 205 had organised some form of remediation.
Assuming that those not returning the questionnaire had not organised
remediation, Bradley suggests an overall uptake of 10 per cent. A more recent
study of an affected area in England (1998), Mendip District Council,
347
confirmed the general trend; around 30 per cent of houses had been tested, 7
per cent over the action level and only about 10 per cent of those households
proceeding to remediation (Lakin, 1998). A similar situation has been found in
Northern Ireland (Brannigan, 1999). In a postal survey of 302 houses above the
action level, it was found that only 21 of the 112 who replied had carried out
some form of remediation. Assuming that those who did not reply had not
organised remediation, then the overall uptake is 6.9 per cent. Even this figure
needs to be treated with caution; in more than half of the cases the measures
taken could not be considered as reasonably effective as they were only
concerned with increasing the ventilation (Table I). A similar recent study in
the Republic of Ireland revealed that only 6 per cent of respondents, all above
the action level, had undertaken satisfactory remediation (Ryan and Kelleher,
1999).
The return rates of the questionnaire, and the uptake of the radon testing for
Higham Ferrers (34 per cent) and Thrapston (43 per cent) were acceptable and
in line with some other studies (Bradley, 1996). Some 68 per cent were aware
that radon was a risk to health (Table V); this is in line with the recent study
from the Republic of Ireland (Ryan and Kelleher, 1999) and indicates some
measure of success in media campaigns concerning radon as an environmental
hazard (Phillips et al., 1999).
Although there was a general awareness of the health risks of radon, the
occupiers demonstrated a much lower awareness of the fact that East
Northamptonshire was an affected area (Table V); 33 per cent said there was a
problem, 59 per cent said ``don't know'' and 8 per cent said ``no''. Perhaps this
indicates that awareness campaigns need to become more focused and
coordinated?
It has been pointed out that the present UK strategy is unlikely to lead to an
increase in the number remediating and that a fundamental review should be
undertaken to determine the best way to reallocate resources so as to facilitate
new and innovative approaches (Lugg and Probert, 1997). The central role of
the local authority Environmental Health Officer (EHO) in devising and
implementing strategies to inform the population, in their area, about radon has
been noted (Jones, 1994). The potential for local doctors to interact with their
patients and warn them about the health risks of radon is a new approach that
may lead to increased remediation (Baldwin et al., 1998). Informing about radon
through a public utility billing service has been shown to be effective in
encouraging remediation in homes where there is a high incidence of smoking,
especially when telephone counselling is available (Lee et al., 1999).
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348
The general low awareness that they were living in an affected area is
mirrored in the small percentage (9 per cent) of occupiers that had their homes
monitored for radon (Table V). The two houses that were above the Action
Level had not proceeded to seek remediation. The percentage of houses that
have been tested in East Northamptonshire (Table III) by 1997 was 12.8 per
cent (3,881 out of 30,300). There is considerable variation, by district, in the
percentage of houses tested for radon in Northamptonshire (Table III). The
reasons for this are many and they include the proportion of houses owned by
local authorities. It appears that in the private sector monitoring rates are low
for a number of reasons, including costs. A strategy that depends upon private
occupiers of new houses, in such areas, monitoring for radon then installing a
fan to activate the sump must be called into question. The automatic placing of
a radon-proof barrier would be superior.
It appears that there was little effective information passed on to the
occupiers by the developers (Table V). Only 13 per cent stated that they had
been clearly informed about the radon protection measures in their house.
Leaving it to the developers is a dubious strategy. Is it in the interest of the
developers, who want to quickly maximise sales, to inform prospective
purchasers that they may be buying into an affected area and that additional
expense will be incurred in monitoring for radon and if necessary fitting a fan?
It could be that local authority EHOs take on the task of informing occupiers
about their status (Jones, 1994), using the local tax demands (Lee et al., 1999)?
The lack of clear guidance from the developers is reflected in the confusion
over the type of radon protection measures in the house (Table VI). No
occupiers were aware that they had a sump that required a fan to activate it.
Indeed, 6 per cent thought that they had a sump that worked without any fan. It
may be argued that around 34 per cent considered that they had a working
system in place. This is achieved by adding the ``some system'' (17 per cent),
membrane (11 per cent) and ``sump with a fan'' (6 per cent) categories. This high
proportion of occupiers would see no need to monitor for radon.
There is a range of agents who might be expected to offer general advice
concerning radon to house purchasers. A majority, of 71 per cent, said that they
were offered no general advice by any agent (Table VII). Surveyors, at 14 per
cent, were the major source of general advice, followed by developers (12 per
cent) and mortgage providers (3 per cent). It appears that estate agents and the
local authority gave no advice (Table VII) even though both could be expected
to. But is it in the best interest of estate agents to inform prospective purchasers
that they may be buying into an affected area and that may entail extra costs?
There are a number of agents whom occupiers have indicated that they may
contact in an attempt to obtain more information concerning radon (Table VIII).
Local authority EHOs need to revisit their strategies to utilise the services of a
range of other agents, including those in Table VIII, in an attempt to attain the
60 per cent remediation levels reached in to well-planned campaigns (Wang
et al., 1999).
It is vital to continue to educate the general public in an attempt to improve Secondary radon
the remediation rate. To guide risk communicators, a new conceptual model
protection
approach to the design and characterisation of all radon communication is
required. New and dynamic partnerships, working closely on the local level,
need to be developed, mostly led by local authority EHOs. The present BRE
strategy is ineffective and needs to be reconsidered because there are
349
considerable barriers to persuading occupiers to monitor for radon and if
necessary remediate. A more effective strategy would offer guidance such that
all new houses in an affected area have a radon-proof barrier installed. The cost
of this would be passed on by the developers to the purchaser of the new houses
but it would ensure that a higher proportion of houses would be below the
action level.
Conclusions
Building Research Establishment (BRE) guidance on radon protection in new
houses was instigated in Northamptonshire in 1993. Houses, in areas where
>10 per cent are above the action level are provided with primary and
secondary measures and those in areas of between 3-10 per cent are only
provided with secondary measures. In the case of the Higham Ferrers estate,
the percentage of houses above the action level at 35 per cent is much greater
than was originally predicted (3-10 per cent), on the basis of NRPB maps,
probably because of underlying geology. The Thrapston estate, with 5 per cent
above the action level, is in line with NRPB predictions. The delineation of
likely radon levels in the Higham Ferrers estate did not fully take into account
an assessment of geological radon potential. Future guidance must take
account of geological radon potential maps. The level of awareness of
householders, at 33 per cent, to the radon problem in East Northamptonshire
was low and demonstrates the need for a continuous information campaign.
The assumption that occupiers would instigate monitoring and if necessary
proceed with remediation is questionable as only 9 per cent were aware that
their homes had been tested for radon. This study confirms the general UK
trend; few occupiers instigate monitoring and remediation. A more effective
guidance would require the installation of primary and secondary measures for
each new house in an affected area; this would reduce dose, in the majority of
cases, to occupiers and circumnavigate the reluctance of the public to pay for
monitoring and remediation.
References
Baldwin, G., Frank, E. and Fielding, B. (1998), ``US women physicians' residential radon testing
practices'', American Journal of Preventive Medicine, Vol. 15 No. 1, pp. 49-53.
Bradley, E.J. (1996), ``Responses to radon remediation advice'', Proc. 9th Int. Congress of the
International Radiation Protection Association, 4-798-4-800.
Brannigan, E. (1999), ``Radon remediation in Northern Ireland, National Radiological Protection
Board'', Environmental Radon Newsletter, No. 21.
EMH
11,4
350
Building Research Establishment (1992), Radon: Guidance on Protective Measures for New
Buildings, Watford, UK.
Darby, S., Whitley, E., Silcocks, T., Thakara, B., Green, B.M.R., Lomas, P.R., Miles, J.C.H., Reeves,
G., Searn, T. and Doll. R. (1998), ``Risk of lung cancer associated with residential radon
exposure in South-West England: a case-controlled study'', British Journal of Cancer,
Vol. 78 No. 3, pp. 394-408.
Denman, A.R. and Phillips, P.S. (1998a), ``A review of cost-effectiveness of radon mitigation in
domestic properties in Northamptonshire'', Journal of Radiological Protection, Vol. 18 No. 2,
pp. 119-24.
Denman, A.R and Phillips, P.S. (1998b), ``Workplace radon in Northamptonshire'', Environmental
Management and Health, Vol. 9 No. 5, pp. 194-9.
Denman, A.R., Barker, S., Parkinson, S., Marley, F. and Phillips, P.S. (1999), ``Do the National
Radiological Protection Board action levels reflect the radiation dose received by
occupants?'', Journal of Radiological Protection, Vol. 19 No. 1, pp. 37-43.
Department of the Environment and the Welsh Office (1992), The Building Regulations Approved
Document C. Site preparation and Resistance to Moisture, HMSO, London, UK.
Gunby, J.A., Darby, S.C., Miles, J.C.H., Green, B.M.R. and Cox, D.R. (1993), ``Factors affecting
indoor radon concentrations in the United Kingdom'', Health Physics, Vol. 64 No. 1, pp. 212.
HMSO (1991), The Building Regulations, London, UK.
Jones, M. (1994), ``Solving the radon problem in the UK ± the role of Environmental Health
Officers'', Radiation Protection Dosimetry, Vol. 56 No. 1-4, pp. 367-70.
Lakin, C. (1998), Radon Remediation in the Private Housing Sector. A Review of the Effectiveness
of Radon Remediation Strategies, Mendip District Council, UK.
Lee, M.E., Lichtenstein, E., Andrews, J.A., Glasgow, R.E. and Hampson, S.E. (1999), ``Radonsmoking synergy: a population-based behavioural risk reduction approach'', Preventive
Medicine, Vol. 29 No. 3, pp. 222-7.
Lee, T.R. and MacDonald, S. (1994), ``Public responses to indoor pollution from radon'', Radiation
Protection Dosimetry, Vol. 56 No. 1-4, pp. 331-7.
Lubin, J.H. and Boice, J.D. Jr (1997), ``Lung cancer risk from residential radon: meta-analysis of
eight epidemiologic studies'', Journal of National Cancer Institute, Vol. 89, pp. 49-57.
Lugg, A. and Probert, D. (1997), ``Indoor radon gas: a potential health hazard resulting from
implementing energy-efficiency measures'', Applied Energy, Vol. 56 No. 2, pp. 193-6.
Miles, J. (1998), ``Mapping radon-prone areas by lognormal modelling of house radon data'',
Health Physics, Vol. 74 No. 3, pp. 370-77.
Naismith, S.P., Miles, J.C.H. and Scivyer, C.R. (1998), ``The influence of house characteristics on
the effectiveness of radon remedial measures'', Health Physics, Vol. 75 No. 4, pp. 410-16.
Najafi, F.T. (1998), ``Radon reduction systems in the construction of new houses in Gainesville,
Florida'', Health Physics, Vol. 75 No. 5, pp. 514-17.
National Radiological Protection Board (1992), Radon Affected Areas: Derbyshire,
Northamptonshire and Somerset, Documents of the National Radiological Protection
Board, Vol. 3 No. 4.
Phillips, P.S., Denman, A.R., and Bates, M.P. (1999), ``The UK radon programme: a review of the
response to the discovery of elevated levels in the built environment'', Environmental and
Waste Management, Vol. 2 No. 3, pp. 167-83.
Ryan, D. and Kelleher, C.C. (1999), ``A survey of householders' mitigation strategy'', European
Journal of Public Health, Vol. 9 No. 1, pp. 62-4.
Scivyer, C. and Woolliscroft, M. (1998), ``Radon remediation and protective measures in UK
buildings: the work of the Building Research Establishment Ltd'', Radiation Protection
Dosimetry, Vol. 78 No. 1, pp. 39-44.
Sutherland, D. and Sharman, G. (1996), ``Radon ± in Northamptonshire?'', Geology Today, Vol. 12
No. 2, pp. 63-7.
Wang, Y., Ju, C., Stark, A.D. and Teresi, N. (1999), ``Radon mitigation survey among New York
State residents living in high radon homes'', Health Physics, Vol. 77 No. 4, pp. 403-09.
Woolliscroft, M., Scivyer, C. and Parkins, L. (1994), ``Field trials on the effectiveness of radon
protection measures in new dwellings'', Radiation Protection Dosimetry, Vol. 56 No. 1-4,
pp. 33-40.
Secondary radon
protection
351
http://www.mcbup.com/research_registers/emh.asp
The current issue and full text archive of this journal is available at
http://www.emerald-library.com
Effectiveness of secondary
radon protection in
Northamptonshire houses
Paul S. Phillips
Secondary radon
protection
337
University College Northampton, Northampton, UK
Julia D. Fraser
East Northamptonshire District Council, Northamptonshire, UK and
Antony R. Denman
Northampton General Hospital, Northampton, UK
Keywords Radon, Housing, United Kingdom
Abstract Northamptonshire is classified as a radon affected area, with greater than 1 per cent
of houses being above the UK action level of 200Bq/m±3. New houses, in areas where >10 per
cent are above the action level, have to have primary protection of a radon-proof membrane and
secondary measures such as a non-activated radon sump. New houses, in areas where 3-10 per
cent are above the action level only need the secondary measures. This research calls into
question the effectiveness of this strategy. The use of radon potential maps, rather than radon in
building maps, would have demonstrated that radon ``hot spots'', where a very high percentage
of houses are over the action level, can occur on a range of geology. One estate, at Higham
Ferrers, had 35 per cent over the action level, even though it had been classified as only requiring
secondary measures. The reluctance of occupiers in the UK to instigate monitoring and
remediation means that very few will have their house tested for radon and activate the sump, by
fitting a fan, if that is required. This paper provides arguments that support the view that it
would be more effective to have primary and secondary measures introduced in all new houses in
radon affected areas.
Introduction
Radon (222Rn) is a naturally occurring radioactive gas which decays into a
series of isotopes known as radon progeny, of which the most significant are
218
Po, and 214Pb. These, if inhaled, can be retained in the lung and deliver a
dose to its walls by alpha particle emission. The potential health hazards from
exposure to radon and its progeny are well documented; recent studies have
demonstrated that there is a significant risk from the dose provided by radon
and its progeny even at the levels found in domestic dwellings (Lubin and
Boice, 1997; Darby et al., 1998). Cost-effective remediation for radon and its
progeny in the built environment (Denman and Phillips, 1998a) must therefore
be a priority for a range of national agencies in an attempt to limit dose to
occupants (Denman et al., 1999).
In the UK, the National Radiological Protection Board (NRPB) established in
1990 an action level of 200Bq/m±3 for domestic properties. The NRPB has also
declared a number of affected areas, where more than 1 per cent of the housing
stock have radon levels over the action level. Northamptonshire is such an area
(NRPB, 1992), with 6.3 per cent of houses above the action level and in some
Environmental Management and
Health, Vol. 11 No. 4, 2000,
pp. 337-351. # MCB University
Press, 0956-6163
EMH
11,4
338
areas, up to 21 per cent of workplaces above that action level of 400 Bq m-3
(Denman and Phillips, 1998b)
Guidance on radon protection
In 1991, the Building Research Establishment (BRE), produced guidance
(revised in 1992) on protective measures against radon in new homes (Building
Research Establishment, 1992). They point out that requirement C2 of Schedule
1 of the Building Regulations for England and Wales (HMSO, 1991) say that:
precautions shall be taken to avoid danger to health and safety caused by substances found
on or in the ground to be covered by the building
The Approved Document (Department of the Environment and the Welsh
Office, 1992) includes radon in the contaminant list because of the increased
risk of lung cancer to those who live in buildings with elevated levels of the gas.
For houses or extensions to be erected in a range of affected areas, including
Northamptonshire, precautions against radon may be necessary. From
February 1993, the guidance applied to new houses in Northamptonshire.
There are two main methods of achieving radon protection. First, the
passive system, known as primary protection. This consists of an airtight and
radon-proof barrier across the whole of the building including the floor and the
walls. The barrier is generally a membrane of 300 micrometer (1,200 gauge)
polythene sheet. Some radon diffusion will probably occur through the sheet
but, as most gas entry is through cracks, this pathway is negligible. For this
system to be effective, it is vital that the radon-proof membrane is not damaged
during construction and that particular attention is given to jointing to prevent
pathways for gas ingress.
Second, the active system, known as secondary protection. This system
consists of a powered radon-extract system as an integral part of the services of
the house. This will incur running and maintenance costs for the life of the
building. Normally, subfloor depressurisation is used to remove radon rich air
from beneath the house and to vent it to external air. This is provided by the
use of a sump positioned centrally under the house and constructed so that the
pipe to external air is not blocked when further building work occurs. The
system is powered by a fan, often mounted on the external wall.
A study on the effectiveness of remedial measures in 943 UK homes has
been published (Naismith et al., 1998). The National Radiological Protection
Board (NRPB) has been running a programme to test the effectiveness of
remedial measures in homes with high radon. Radon sumps were found to be
the most effective remedial method with the highest reduction factor (Table I).
Since BRE guidance has been implemented, new dwellings in
Northamptonshire, in areas with a greater than 10 per cent of houses likely to
be above the action level, have to have full radon protection of primary and
secondary measures (Figure 1). New dwellings in Northamptonshire, in areas
where the risk of houses being above the action level is between 3 and 10 per
cent, have only to have the secondary measure (Figure 1). In both situations,
Remedial measure
Sump, major contractor, post-war house
Sump, major contractor, pre-war house
Sump, local builder, post-war house
Sump, local builder, pre-war house
Sump, DIY, post-war house
Sump, DIY, pre-war house
Positive ventilation, two-storey house
Positive ventilation, bungalow
Additional permanent ventilation of house, no
additional sealing
Additional permanent ventilation of house,
with additional sealing
Mechanical ventilation of underfloor space
Natural ventilation of underfloor space
Sealing of cracks, entry points
Geometric mean of
reduction factors
Percentage of houses
reduced below the
action level
17
9
11
6
7
4
1.9
3.7
95
77
82
70
77
64
42
63
1.5
49
2.4
2.8
1.9
1.7
60
54
53
41
Source: Naismith et al., 1998
builders of new houses do not have to install a fan to drive the secondary
protection. It is left to the householder to arrange monitoring to determine
whether or not the house is above the action level; if this is so they need to fit a
fan to activate the sump and bring radon levels below 200Bq/m±3.
The BRE make clear that further research may cause the list of areas that
require precautionary measures to be revised. The central role of the local
authority in enforcing Building Regulations is recognised and they will be able
to confirm the status of a given area to an enquirer. The BRE designated areas
in Northamptonshire are based upon information provided by the NRPB,
except that the area covered by the guidance is somewhat larger than that
indicated by the NRPB maps. This is because the guidance is based on
administrative areas under local authority control; this is the Parish which is
part of a District or Borough in a typical English county. East
Northamptonshire (Figure 1) contains 60 parishes, 33 of which are in affected
areas that only require active measures in new houses (3-10 per cent above
action level), while 27 require no measures (less than 3 per cent above the
action level).
Radon maps
Various types of area boundaries are used in the analysis of radon data and the
production of a range of maps. Administrative boundaries are one class, as are
geological boundaries or divisions such as 5km grid squares; these were used
by the NRPB to delineate affected areas. Using such areas simplifies
administrative action as it is easier to determine whether new houses require
radon protection by using their address (postcode) rather than using map
Secondary radon
protection
339
Table I.
Effectiveness of
remedial measures in
UK houses
EMH
11,4
340
Figure 1.
Areas of
Northamptonshire
where primary and
secondary systems are
required in new houses
coordinates. Geological boundaries are, however, potentially more useful as
likely radon levels are strongly linked to underlying geology. They are,
however, difficult to use as the geology of an area may be much more complex
than first appears, with marked variations in a small area. It may be that those
radon ``hot-spots'', which produce houses well over the action level, may be
overlooked by the inexperienced user of such maps. Two variations of maps
may be used when delineating radon-prone areas. One type shows radon
potential for a standard house or national mix of houses, the other shows how
radon would vary for the typical housing stock for that area. When NRPB
measurement of radon in houses is studied in relation to underlying geology,
they are normalised to a standard mix of houses (Miles, 1998).
Radon and geology
Northamptonshire is a county of essentially sedimentary rocks, mainly Lower
to Middle Jurassic (Sutherland and Sharman, 1996). Highest radon levels are
found on Upper Lincolnshire Limestone, Northampton Sand Ironstone,
Marlstone Rock Bed and Glacial sand and gravel; here more than 20 per cent of
houses can be over the action level (Table II). Lowest radon levels are found on
Hazard group
Low
Slight
% houses above
action level
20
Secondary radon
protection
Geological formations and drift deposits
Clays: Alluvial, Oxford, Blisworth & Rutland
Formation
Kellaways Clay, Blisworth Limestone, Rutland
Formation, Upper Lias Clay, River gravels, Boulder
Clay
Kellaways Sand, Cornbrash, Grantham Formation,
Northampton Sand, Lower Lias Clay
Upper Lincolnshire Limestone, Northampton Sand
Ironstone, Marlstone Rock Bed, Glacial sand and gravel
Source: Sutherland and Sharman, 1996
341
Table II.
Some geological
formations and their
radon hazards in
Northamptonshire
Oxford Clay, Blisworth Clay and Rutland Formation Clay; here less than 1 per
cent of houses are over the action level (Table II). Ironstone in the county is
phosphatic and uranium is often associated with phosphorus. A layer of
phosphatic pebbles at the base of the ironstone layer has the highest uranium
levels in the geology and would be expected to generate significant radon
levels. This, allied to a high level of permeability in the rock, means that areas
of the county have raised radon levels in houses (Figure 1)
New house building in Northamptonshire is running above the national
average, with the housing stock increasing by 4.7 per cent since 1993, when
guidance was first applied for new housing. The number of existing and new
houses for the districts and boroughs of the county are shown in Table III. The
rapid rise in the number of new houses, allied to the serious radon problem,
means that this county is a suitable location for surveys concerning the efficacy
of radon precaution systems built into new houses. This survey reports on the
radon levels in new houses that were built with secondary protection measures,
after 1993, as well as the occupiers' responses to the requirement for them to
test for radon and if necessary to fit a fan to activate the sump.
District
Corby
Daventry
East Northants
Kettering
Northampton
South Northants
Wellingborough
Total
Housing stock
(1997)
No. tested for
radon
22,600
28,400
30,300
34,600
81,100
29,900
30,000
256,900
1,173
6,065
3,881
7,319
29,378
4,312
14,075
66,203
No. above action New houses built
level
(1993-1997)
24
475
212
997
1,304
223
936
4,171
960
1,990
1,540
1,390
3,450
1,800
1,070
12,200
Table III.
Housing statistics for
Northamptonshire
EMH
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342
Materials and method
Two recently constructed housing estates in East Northamptonshire were
chosen for this study as both have been constructed after 1993, when the BRE
guidance came into effect. East Northamptonshire is a District that has 33
parishes in the 3-10 per cent above action level category and 27 that are below
this level (Figure 1). One estate is in Higham Ferrers and the other in
Thrapston, both in the overall 3-10 per cent category. Information concerning
the radon levels in houses, on a smaller scale than a parish, can be obtained by
using the postcodes of the areas. The Higham Ferrers estate is in an area that,
using data available, is considered to have 9 per cent of houses over the action
level. Similarly, the Thrapston estate is in an area where 11.7 per cent of the
houses are over the action level.
The geology of the Higham Ferrers site is essentially that of the Great Oolite
Group. This contains Cornbrash, Kellaways sand and clay, Blisworth Clay and
Blisworth Limestone (Table II). Depending upon the detailed geology of the
site, the percentage of dwellings above the Action Level could range from
below 1 per cent to between 2-15 per cent (Table II). The Thrapston site is based
essentially on Oxford Clay; such underlying geology would be expected to have
less than 1 per cent of homes above the action level (Table II).
The estate in Higham Ferrers has around 100 occupied houses and in
Thrapston there are around 230 occupied houses. On each estate, houses have
been built by a number of different developers. Both estates are predominantly
detached three- and four-bedroom houses with a similar type of construction
and the results in this study only apply to such buildings. No house has a
radon-proof membrane but all have a sump which could be activated by fitting
a fan; this was confirmed by Local Authority Building Control. Building type
does affect the radon levels in the built environment and so this study yields
information that has not been distorted by a wide variety of building types
(Gunby et al., 1993).
Every house, on both estates, was contacted with an introductory letter and
a questionnaire. The occupiers were also offered a free radon test. The offer
was taken up by 99 houses from Thrapston (43 per cent response) and 34 from
High Ferrers (34 per cent response) and testing took place in June 1999. This
return rate is in line with other such radon surveys in the UK (Brannigan, 1999)
and appears to suggest that radon is not a high priority for householders even
in affected areas. The questionnaire was a mixture of open and closed nonbiased questions along with a number of more open ended questions. Members
of each household were counselled about the radon test and the importance of
not tampering with the detectors. Detectors were collected, at the same time as
the completed questionnaire, and placed into protective packaging before
sending for analysis.
Radon levels in houses were measured using alpha track (CR-39) detectors
with a six-day exposure. The NRPB protocol for siting detectors was used; one
was placed in the major bedroom and one in the main living room, away from
draughts and at suitable height from the floor. The living area and the bedroom
values are then combined using 0.55 for the bedroom value and 0.45 for the Secondary radon
living area, to reflect occupancy patterns. The results were sessionally adjusted
protection
by using the NRPB monthly seasonal correction factors for domestic premises.
NRPB suggest that using monthly correction factors will produce a standard
deviation of 0.96 from three monthly readings.
Results
Radon levels in houses
The radon levels for the 133 houses from the two estates are shown in Table
IV. Both estates are situated in an area that guidance, on radon protective
measures in new houses, suggests would have between 3 and 10 per cent of
houses above the action level. The Thrapston estate, with 5 per cent above
the action level, clearly falls into this category but this value is higher than
would be expected from a consideration of geology alone. Estates on the
Oxford Clay formation would be expected to have less than 1 per cent of
houses above the action level; this demonstrates that geological maps are at
best indicative.
The Higham Ferrers site has 35 per cent above the action level. This
remarkably high level is almost certainly due to a local radon ``hot spot''.
Although the surface geology is considered to be essentially the Great Oolite
Group, it is probably, in the area of the estate, dominated by the underlying
Lincolnshire Limestone Formation (Table II). The application of the guidance
for the construction of new houses does not take into account the need to
accurately determine the geology on the building site so as to locate local ``hot
spots''.
Radon (Bq/m-3)
0-25
26-50
51-75
76-100
101-125
126-150
151-175
176-200
201-225
226-250
251-275
276-300
301-325
351-375
376-400
401-425
% above action level
343
Number of houses
Higham Ferrers
Thrapston
0
14
4
1
0
1
2
0
1
1
1
6
2
1
0
0
35
0
16
30
18
10
13
5
2
2
0
3
0
0
0
0
0
5
Table IV.
Radon levels in new
houses from estates in
Higham Ferrers and
Thrapston, East
Northamptonshire
EMH
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344
Table V.
Occupiers' responses to
radon questionnaire
Results from the questionnaire
Question 1 ± Is radon gas a health risk? A clear majority of 68 per cent
indicated that they were aware that radon was a health risk while 23 per cent
thought it was not and 9 per cent came into the ``don't know'' category ± making
a total of 32 per cent who were unaware that it was a health risk (Table V). The
questionnaire did not elicit a response to the type of health risk posed by radon.
Initial, unpublished work by one of the authors concerning the public
understanding of the health risk posed by radon in East Northamptonshire
suggests that a significant proportion of those who are aware of the risk equate
it, correctly, with some type of cancer.
Question 2 ± Is radon a problem in East Northamptonshire? Some 33 per
cent were aware that there is a radon problem in East Northamptonshire, 59 per
cent did not know and 8 per cent said no (Table V). It must be borne in mind
that the occupiers had purchased a house that had been constructed according
to guidance and had a sump with a provision for a fan and so might have been
expected to be aware of the implications of this.
Question 3 ± Has your house been tested for radon? Some 9 per cent
answered yes to this and claimed that their house had been tested for radon, an
overwhelming 91 per cent said no (Table V). Of the 9 per cent (12 houses) who
answered yes, only two were above the action level and they had not proceeded
to remediate.
Question 4 ± Were you clearly informed by the developers about the radon
protection measure in your new house? Some 13 per cent said that they had
been so informed, 87 per cent said no (Table V). This is a key finding as
developers could be expected to inform the purchasers and so encourage them
to seek radon monitoring.
Question 5 ± What radon protection system is built into your house? Some
62 per cent said that they had ``no knowledge'', 17 per cent said ``some system'',
11 per cent said a membrane, 6 per cent said a sump that worked without a fan
and 4 per cent said ``no system'' (Table VI).
Question 6 ± From whom did you receive ``general'' advice about radon when
purchasing your house? Some 14 per cent said surveyors, 14 per cent said
developers, 3 per cent said the mortgage provider. No one claimed to receive
Question
Yes
1.
2.
3.
4.
68
33
9
13
Is radon gas a health risk?
Is radon a problem in East Northants?
Has your house been tested for radon?
Were you clearly informed by the
developers about the radon protection
measure in your house?
Response (%)
No
Don't know
23
8
91
87
9
59
±
±
advice from the estate agent, local doctor, local authority or NRPB. A clear Secondary radon
majority of 71 per cent said that no advice had been provided by any agent
protection
(Table VII).
Question 7 ± Who would you ask for advice on dealing with radon in your
house? The local District Council at 46 per cent was the preferred choice with
the County Council coming second with 22 per cent. Other organisations
345
include the NRPB, the local elected member of the District or Parish Council
and the local doctor (Table VIII).
Discussion
The BRE has been carrying out research, funded by the UK Department of the
Environment, Transport and the Regions (DETR), into radon and the built
environment since the late 1980s. Their research has resulted in the successful
development of a range of radon remedial measures (Scivyer and Woolliscroft,
1998). The use of the radon proof membrane has been a proven success, if
installed correctly. Monitoring of 423 houses in the South West of England, the
BRE has shown that the membrane was successful at preventing radon ingress
and significant at the 0.1 per cent level (Woolliscroft et al., 1994). This has also
been demonstrated in a number of other countries, (e.g. Najafi, 1998). The use of
a passive system, such as a membrane, may in itself not be sufficient in every
case and then an active system is required (Table I).
The guidance given by the BRE, on protection measures, is based upon
radon maps produced by the NRPB. These maps have been then used to predict
administrative areas (parishes) that fall into the two categories and are used by
local authority Building Control to issue guidance to those building new homes.
The simplistic use of such maps, without a detailed consideration of the
Measure
Some system
Membrane
Sump that worked without a fan
No system
No knowledge
Source of advice
Surveyors
Developers
Mortgage provider
Estate agent
Local authority
Local doctor
No advice
Percentage of occupiers
17
11
6
4
62
Table VI.
What radon protection
measure occupiers
thought was in their
house
Percentage of occupiers
14
12
3
0
0
0
71
Table VII.
Sources of general
advice on radon to
house purchasers
EMH
11,4
346
geology of the site (Table II), can result in houses being built on a formation
that may lead to radon levels much higher than predicted ± a local radon ``hot
spot''.
The Higham Ferrers site, with 35 per cent of houses over the action level
(Table IV) is an example of this. The use of postcodes, to indicate a more likely
radon level, fails to signal the possibility of such a variation. The Thrapston
site, with 5 per cent above the action level, is actually below the level expected
for that postcode. The use of postcodes is informative as the Thrapston site is
in an area where 11.7 per cent are over the action level, yet, overall, it is in a 3-10
per cent parish. The BRE guidance, first issued in 1991, failed to take full
account of the possibility of such marked variations that can result from local
``hot spots''. With hindsight, a mechanism could have been developed so that
regular radon monitoring was required by a local authority in an attempt to
identify such ``hot spots''.
The BRE seem to consider that occupiers, in areas with a 3-10 per cent
chance of houses being above the action level, would proceed to have a radon
test and if the value was high enough to have a fan fitted so as to activate the
sump. Reduction factors, for indoor radon (geometric mean) of around 17 could
then be achieved (Table I). The present cost of having a fan fitted by a major
contractor in Northamptonshire is in the region of £150. This will incur
running costs of some £35 per annum. This stands in contrast to the present
estimated cost of some £320 for placing a radon proof membrane in a typical
three-bedroom detached house being constructed in Northamptonshire. The
present costs of having a major contractor install a sump and fan in a similar
house is in the region of £550.
For the guidance of the BRE to have any impact it needs to have a clear
mechanism whereby house purchasers are informed about the radon health
risks. It must also be made unambiguous that it is their responsibility to
instigate testing, and if required to activate the sump by fitting a fan. Since the
development and implementation of the BRE policy, research on householders'
responses to elevated levels in the built environment has called into question
the assumption that the public would instigate monitoring and remediation on
a significant scale.
In one study (1994) in the South West of England, only 3-5 per cent of those
above the action level proceeded to carry out some form of remediation (Lee
Source of advice
Table VIII.
Whom occupiers
considered a source of
reliable advice on
radon in the home
District Council
County Council
NRPB
Local councillor
Local doctor
Other, e.g. neighbour
Don't know
Percentage of occupiers
46
22
14
4
4
5
5
and MacDonald, 1994). Bradley reported, in 1996, the results of a postal survey Secondary radon
of 10,500 householders with initial levels above the action level (Bradley,
protection
1996). Of the 5,000 who replied, 205 had organised some form of remediation.
Assuming that those not returning the questionnaire had not organised
remediation, Bradley suggests an overall uptake of 10 per cent. A more recent
study of an affected area in England (1998), Mendip District Council,
347
confirmed the general trend; around 30 per cent of houses had been tested, 7
per cent over the action level and only about 10 per cent of those households
proceeding to remediation (Lakin, 1998). A similar situation has been found in
Northern Ireland (Brannigan, 1999). In a postal survey of 302 houses above the
action level, it was found that only 21 of the 112 who replied had carried out
some form of remediation. Assuming that those who did not reply had not
organised remediation, then the overall uptake is 6.9 per cent. Even this figure
needs to be treated with caution; in more than half of the cases the measures
taken could not be considered as reasonably effective as they were only
concerned with increasing the ventilation (Table I). A similar recent study in
the Republic of Ireland revealed that only 6 per cent of respondents, all above
the action level, had undertaken satisfactory remediation (Ryan and Kelleher,
1999).
The return rates of the questionnaire, and the uptake of the radon testing for
Higham Ferrers (34 per cent) and Thrapston (43 per cent) were acceptable and
in line with some other studies (Bradley, 1996). Some 68 per cent were aware
that radon was a risk to health (Table V); this is in line with the recent study
from the Republic of Ireland (Ryan and Kelleher, 1999) and indicates some
measure of success in media campaigns concerning radon as an environmental
hazard (Phillips et al., 1999).
Although there was a general awareness of the health risks of radon, the
occupiers demonstrated a much lower awareness of the fact that East
Northamptonshire was an affected area (Table V); 33 per cent said there was a
problem, 59 per cent said ``don't know'' and 8 per cent said ``no''. Perhaps this
indicates that awareness campaigns need to become more focused and
coordinated?
It has been pointed out that the present UK strategy is unlikely to lead to an
increase in the number remediating and that a fundamental review should be
undertaken to determine the best way to reallocate resources so as to facilitate
new and innovative approaches (Lugg and Probert, 1997). The central role of
the local authority Environmental Health Officer (EHO) in devising and
implementing strategies to inform the population, in their area, about radon has
been noted (Jones, 1994). The potential for local doctors to interact with their
patients and warn them about the health risks of radon is a new approach that
may lead to increased remediation (Baldwin et al., 1998). Informing about radon
through a public utility billing service has been shown to be effective in
encouraging remediation in homes where there is a high incidence of smoking,
especially when telephone counselling is available (Lee et al., 1999).
EMH
11,4
348
The general low awareness that they were living in an affected area is
mirrored in the small percentage (9 per cent) of occupiers that had their homes
monitored for radon (Table V). The two houses that were above the Action
Level had not proceeded to seek remediation. The percentage of houses that
have been tested in East Northamptonshire (Table III) by 1997 was 12.8 per
cent (3,881 out of 30,300). There is considerable variation, by district, in the
percentage of houses tested for radon in Northamptonshire (Table III). The
reasons for this are many and they include the proportion of houses owned by
local authorities. It appears that in the private sector monitoring rates are low
for a number of reasons, including costs. A strategy that depends upon private
occupiers of new houses, in such areas, monitoring for radon then installing a
fan to activate the sump must be called into question. The automatic placing of
a radon-proof barrier would be superior.
It appears that there was little effective information passed on to the
occupiers by the developers (Table V). Only 13 per cent stated that they had
been clearly informed about the radon protection measures in their house.
Leaving it to the developers is a dubious strategy. Is it in the interest of the
developers, who want to quickly maximise sales, to inform prospective
purchasers that they may be buying into an affected area and that additional
expense will be incurred in monitoring for radon and if necessary fitting a fan?
It could be that local authority EHOs take on the task of informing occupiers
about their status (Jones, 1994), using the local tax demands (Lee et al., 1999)?
The lack of clear guidance from the developers is reflected in the confusion
over the type of radon protection measures in the house (Table VI). No
occupiers were aware that they had a sump that required a fan to activate it.
Indeed, 6 per cent thought that they had a sump that worked without any fan. It
may be argued that around 34 per cent considered that they had a working
system in place. This is achieved by adding the ``some system'' (17 per cent),
membrane (11 per cent) and ``sump with a fan'' (6 per cent) categories. This high
proportion of occupiers would see no need to monitor for radon.
There is a range of agents who might be expected to offer general advice
concerning radon to house purchasers. A majority, of 71 per cent, said that they
were offered no general advice by any agent (Table VII). Surveyors, at 14 per
cent, were the major source of general advice, followed by developers (12 per
cent) and mortgage providers (3 per cent). It appears that estate agents and the
local authority gave no advice (Table VII) even though both could be expected
to. But is it in the best interest of estate agents to inform prospective purchasers
that they may be buying into an affected area and that may entail extra costs?
There are a number of agents whom occupiers have indicated that they may
contact in an attempt to obtain more information concerning radon (Table VIII).
Local authority EHOs need to revisit their strategies to utilise the services of a
range of other agents, including those in Table VIII, in an attempt to attain the
60 per cent remediation levels reached in to well-planned campaigns (Wang
et al., 1999).
It is vital to continue to educate the general public in an attempt to improve Secondary radon
the remediation rate. To guide risk communicators, a new conceptual model
protection
approach to the design and characterisation of all radon communication is
required. New and dynamic partnerships, working closely on the local level,
need to be developed, mostly led by local authority EHOs. The present BRE
strategy is ineffective and needs to be reconsidered because there are
349
considerable barriers to persuading occupiers to monitor for radon and if
necessary remediate. A more effective strategy would offer guidance such that
all new houses in an affected area have a radon-proof barrier installed. The cost
of this would be passed on by the developers to the purchaser of the new houses
but it would ensure that a higher proportion of houses would be below the
action level.
Conclusions
Building Research Establishment (BRE) guidance on radon protection in new
houses was instigated in Northamptonshire in 1993. Houses, in areas where
>10 per cent are above the action level are provided with primary and
secondary measures and those in areas of between 3-10 per cent are only
provided with secondary measures. In the case of the Higham Ferrers estate,
the percentage of houses above the action level at 35 per cent is much greater
than was originally predicted (3-10 per cent), on the basis of NRPB maps,
probably because of underlying geology. The Thrapston estate, with 5 per cent
above the action level, is in line with NRPB predictions. The delineation of
likely radon levels in the Higham Ferrers estate did not fully take into account
an assessment of geological radon potential. Future guidance must take
account of geological radon potential maps. The level of awareness of
householders, at 33 per cent, to the radon problem in East Northamptonshire
was low and demonstrates the need for a continuous information campaign.
The assumption that occupiers would instigate monitoring and if necessary
proceed with remediation is questionable as only 9 per cent were aware that
their homes had been tested for radon. This study confirms the general UK
trend; few occupiers instigate monitoring and remediation. A more effective
guidance would require the installation of primary and secondary measures for
each new house in an affected area; this would reduce dose, in the majority of
cases, to occupiers and circumnavigate the reluctance of the public to pay for
monitoring and remediation.
References
Baldwin, G., Frank, E. and Fielding, B. (1998), ``US women physicians' residential radon testing
practices'', American Journal of Preventive Medicine, Vol. 15 No. 1, pp. 49-53.
Bradley, E.J. (1996), ``Responses to radon remediation advice'', Proc. 9th Int. Congress of the
International Radiation Protection Association, 4-798-4-800.
Brannigan, E. (1999), ``Radon remediation in Northern Ireland, National Radiological Protection
Board'', Environmental Radon Newsletter, No. 21.
EMH
11,4
350
Building Research Establishment (1992), Radon: Guidance on Protective Measures for New
Buildings, Watford, UK.
Darby, S., Whitley, E., Silcocks, T., Thakara, B., Green, B.M.R., Lomas, P.R., Miles, J.C.H., Reeves,
G., Searn, T. and Doll. R. (1998), ``Risk of lung cancer associated with residential radon
exposure in South-West England: a case-controlled study'', British Journal of Cancer,
Vol. 78 No. 3, pp. 394-408.
Denman, A.R. and Phillips, P.S. (1998a), ``A review of cost-effectiveness of radon mitigation in
domestic properties in Northamptonshire'', Journal of Radiological Protection, Vol. 18 No. 2,
pp. 119-24.
Denman, A.R and Phillips, P.S. (1998b), ``Workplace radon in Northamptonshire'', Environmental
Management and Health, Vol. 9 No. 5, pp. 194-9.
Denman, A.R., Barker, S., Parkinson, S., Marley, F. and Phillips, P.S. (1999), ``Do the National
Radiological Protection Board action levels reflect the radiation dose received by
occupants?'', Journal of Radiological Protection, Vol. 19 No. 1, pp. 37-43.
Department of the Environment and the Welsh Office (1992), The Building Regulations Approved
Document C. Site preparation and Resistance to Moisture, HMSO, London, UK.
Gunby, J.A., Darby, S.C., Miles, J.C.H., Green, B.M.R. and Cox, D.R. (1993), ``Factors affecting
indoor radon concentrations in the United Kingdom'', Health Physics, Vol. 64 No. 1, pp. 212.
HMSO (1991), The Building Regulations, London, UK.
Jones, M. (1994), ``Solving the radon problem in the UK ± the role of Environmental Health
Officers'', Radiation Protection Dosimetry, Vol. 56 No. 1-4, pp. 367-70.
Lakin, C. (1998), Radon Remediation in the Private Housing Sector. A Review of the Effectiveness
of Radon Remediation Strategies, Mendip District Council, UK.
Lee, M.E., Lichtenstein, E., Andrews, J.A., Glasgow, R.E. and Hampson, S.E. (1999), ``Radonsmoking synergy: a population-based behavioural risk reduction approach'', Preventive
Medicine, Vol. 29 No. 3, pp. 222-7.
Lee, T.R. and MacDonald, S. (1994), ``Public responses to indoor pollution from radon'', Radiation
Protection Dosimetry, Vol. 56 No. 1-4, pp. 331-7.
Lubin, J.H. and Boice, J.D. Jr (1997), ``Lung cancer risk from residential radon: meta-analysis of
eight epidemiologic studies'', Journal of National Cancer Institute, Vol. 89, pp. 49-57.
Lugg, A. and Probert, D. (1997), ``Indoor radon gas: a potential health hazard resulting from
implementing energy-efficiency measures'', Applied Energy, Vol. 56 No. 2, pp. 193-6.
Miles, J. (1998), ``Mapping radon-prone areas by lognormal modelling of house radon data'',
Health Physics, Vol. 74 No. 3, pp. 370-77.
Naismith, S.P., Miles, J.C.H. and Scivyer, C.R. (1998), ``The influence of house characteristics on
the effectiveness of radon remedial measures'', Health Physics, Vol. 75 No. 4, pp. 410-16.
Najafi, F.T. (1998), ``Radon reduction systems in the construction of new houses in Gainesville,
Florida'', Health Physics, Vol. 75 No. 5, pp. 514-17.
National Radiological Protection Board (1992), Radon Affected Areas: Derbyshire,
Northamptonshire and Somerset, Documents of the National Radiological Protection
Board, Vol. 3 No. 4.
Phillips, P.S., Denman, A.R., and Bates, M.P. (1999), ``The UK radon programme: a review of the
response to the discovery of elevated levels in the built environment'', Environmental and
Waste Management, Vol. 2 No. 3, pp. 167-83.
Ryan, D. and Kelleher, C.C. (1999), ``A survey of householders' mitigation strategy'', European
Journal of Public Health, Vol. 9 No. 1, pp. 62-4.
Scivyer, C. and Woolliscroft, M. (1998), ``Radon remediation and protective measures in UK
buildings: the work of the Building Research Establishment Ltd'', Radiation Protection
Dosimetry, Vol. 78 No. 1, pp. 39-44.
Sutherland, D. and Sharman, G. (1996), ``Radon ± in Northamptonshire?'', Geology Today, Vol. 12
No. 2, pp. 63-7.
Wang, Y., Ju, C., Stark, A.D. and Teresi, N. (1999), ``Radon mitigation survey among New York
State residents living in high radon homes'', Health Physics, Vol. 77 No. 4, pp. 403-09.
Woolliscroft, M., Scivyer, C. and Parkins, L. (1994), ``Field trials on the effectiveness of radon
protection measures in new dwellings'', Radiation Protection Dosimetry, Vol. 56 No. 1-4,
pp. 33-40.
Secondary radon
protection
351