Purpose
This Policy Position Statement presents a balanced technical
view on the complex subject of Lead in Drinking Water, recognising
both the significance of public health implications and the
enormity of the potential costs involved with further actions to
reduce lead concentrations, and encouraging solutions that are
environmentally sustainable. It has been updated in the light of
information published by the World Health Organization (WHO).
CIWEM's Position on Lead in Drinking Water
1. The European standards for lead in drinking
water are fully justified to protect public health. The current
interim standard of 25 µg/l will be tightened to 10 µg/l in
December 2013, providing a greater level of safety. These
standards apply at consumers' cold water taps.
2. A further tightening of the lead standard may
be necessary, as health concerns have increased, and it will be
essential for a holistic approach to be taken that is achievable in
practical terms. The World Health Organization has retained its
guideline value of 10 µg/l in the 4th Edition of
Drinking Water Quality Guidelines (WHO, 2011), but it has been
given provisional status on the basis of achievability.
3. Problems with sampling for determining
compliance have been identified in many EU countries (but not the
UK) and the specification of a harmonised sampling methodology by
the European Commission is long over-due. Recommendations to the
European Commission (Hoekstra et al, 2008) that are
welcomed will:
(i) incorporate risk assessment and risk management in a revision
of the EU Drinking Water Directive, highlighting metal pick-up from
domestic pipework systems, particularly lead;
(ii) encourage operational monitoring additional to compliance
monitoring; and
(iii) adopt random daytime sampling as the harmonised method for
assessing compliance with standards for lead (and copper and
nickel).
4. Wholesale replacement of lead pipes in the UK
would involve great cost and inconvenience and is complicated by
lead pipes being partly owned by the water supplier and partly
owned by the property owner. Nevertheless, replacement of all
lead pipes must be the long-term aim and a strategy for doing this
should be developed. In the meantime, the proactive
replacement programme (DWI, 2010) for lead pipes in public
buildings is welcomed. The partial replacement of lead pipes to a
home (such as just removing the lead pipe section owned by the
water company) is not recommended as lead concentrations can be
increased as a result of physical disturbance in such
circumstances, at least in the short term.
5. Reducing the plumbosolvency of water
supplies (how readily they dissolve lead) by dosing with a
corrosion inhibitor (most commonly orthophosphate) can, depending
on circumstances, offer a rapid, comprehensive and low-cost
approach for achieving substantial compliance with EU lead
standards.
6. Optimisation of plumbosolvency control by
treatment requires:
(i) correct pH conditions;
(ii) correct orthophosphate dose;
(iii) adequate organics removal (particularly colour); and
(iv) distribution networks to be free of significant iron
discolouration problems.
About 95% of water supplies are now dosed with ortho-phosphate
in the UK and following optimisation in England and Wales, 99.8 %
of random daytime samples complied in 2010 with the current lead
standard of 25 µg/l and 99.0 % complied with the future lead
standard of 10 µg/l. Compliance in Scotland and Northern Ireland is
fairly similar.
7. Where orthophosphate dosing of water
supplies is practised, an objective assessment of its environmental
impact in wastewater catchments should be considered, to ensure
that any subsequent environmental controls are justified.
8. Corrective action to reduce lead in
drinking water will depend on local circumstances and economics,
and must be balanced with environmental impact. Whichever
corrective action is taken, the intention must be to protect public
health, regardless of any complications arising from the split
ownership of lead pipes.
9. Across main-land Europe there is scope for
a better understanding of the complex inter-related issues relating
to lead in drinking water, particularly because some Member States
have not historically sampled from consumers' premises and have
little relevant data.
10. Small and very small water supply systems are
particularly vulnerable as often treatment is either poorly
maintained or simply unavailable. Best Practice Guides are now
available from the International Water Association that span all
sizes of water supply systems (IWA, 2010 a, b).
The Chartered Institution of Water and Environmental
Management (CIWEM) is the leading professional body for the people
who plan, protect and care for the environment and its resources,
providing educational opportunities, independent information to the
public and advice to government. Members in 98 countries include
scientists, engineers, ecologists and students.
Context
Lead is a cumulative poison that affects the nervous system and
can retard some aspects of child development (both size and
intelligence). The World Health Organization, in its booklet on
Childhood Lead Poisoning (WHO, 2010) has drawn attention to:
(i) recent research that indicates that lead is associated with
neurobehavioural damage at blood levels of 5 µg/dl and even lower
(hitherto, 10 µg/dl has been considered to be the trigger for
concern);
(ii) there appears to be no threshold level below which lead causes
no injury to the developing human brain;
(iii) an increase in blood lead level from < 1 to 10 µg/dl has
been associated with an IQ loss of 6 points; and
(iv) further IQ losses of between 2.5 and 5 have been associated
with an increase in blood level over the range 10 to 20 µg/dl.
The potential link with lead in drinking water is considered
important (IWA, 2011) and an average concentration of lead in
drinking water of 20 µg/l has been associated with a blood lead
concentration of between 10 and 15 µg/dl, in generalised terms,
although specific impacts from lead in drinking water will depend
on individual consumption patterns and age. The Joint FAO/WHO
Expert Committee on Food Additives re-evaluated lead in June 2010
and withdrew the provisional tolerable weekly intake guideline
value for lead on the grounds that it was inadequate to protect
against IQ loss. This guideline value had been used as a basis for
determining WHO's guideline value for lead in drinking water of 10
µg/l. It is therefore possible that WHO may lower its guideline
value for drinking water in the future. For the time being,
WHO (2011) has retained its guideline value of 10 µg/l for lead in
drinking water, but as a provisional guideline on the basis of
achievability.
Lead pipes were used up to the 1980s both for connecting a
property to the water supply main and for internal plumbing, due to
lead's strength, malleable nature and resistance to corrosion. In
the UK, about 40% of properties are supplied via a lead pipe.
Elsewhere in Europe, the estimated percentage of properties
supplied by lead pipe-work varies from <5 to 50 per cent.
Although the rate of corrosion of the internal lead pipe wall is
very small, lead dissolution into drinking water can very
occasionally still reach concentrations of several milligrams per
litre (parts per million), way in excess of the concentrations
considered to be safe for regular ingestion (parts per billion).
Lead pipes are, by far, the commonest source of lead in drinking
water. There is no lead in the water suppliers' distribution
network, as the materials used for water mains are iron, plastic or
asbestos cement. Short-term contributions are possible from some
pipe-work fittings (particularly brass) and from the galvanic
(electro-chemical) corrosion of lead-containing solders (which are
now prohibited for use in drinking water systems) used to join
copper pipes. The lead that dissolves mostly remains in solution
but contact with iron corrosion deposits from old iron mains can
result in the lead being converted to a particulate form.
As the extent of the problem of lead in drinking water has
become clearer, standards for drinking water have been tightened
and much attention is being given to the recently implemented
standards that derive from the European Drinking Water Directive of
1998. Such standards do not differentiate between the soluble and
particulate forms of lead.
A standard of 25 µg/l has applied since December 2003 at the
point of use by the consumer (commonly regarded as the kitchen sink
tap). Although this standard is expressed as a weekly average
concentration, it has been implemented more stringently in the UK
as a maximum concentration because of the way compliance samples
are obtained (through random day time samples of the first litre of
water that issues from the tap when the sampler visits, taken from
randomly selected properties). This standard tightens to 10 µg/l in
December 2013 although the UK Government has already required some
corrective measures to be taken in an attempt to achieve the
tighter standard much sooner, as far as it is practicable to do
so.
Key Issues
A Europe-wide
problem
The concentration of lead in drinking water varies quite
considerably, as a function of how much lead pipe is present,
water-pipe contact time and the corrosivity of the water, making it
difficult to characterise by sampling. This has made the
optimisation of corrective measures much more difficult and many
water suppliers have used additional investigational tools,
including testing the corrosivity of the water, lead solubility
modelling and computer simulation of lead emissions across whole
zones (using probabilistic techniques). The UK has a comprehensive
understanding of the extent of lead in drinking water problems as a
result of widespread sampling at consumers' taps for over twenty
years. In contrast, many other European countries have very little
knowledge of the extent of the problem because they have not
routinely monitored consumers' premises, or have done so only after
flushing the pipework. The root cause of these problems is that the
EU Member States failed to agree a harmonised monitoring method for
copper, lead and nickel at the tap, making the current Drinking
Water Directive inoperable for these parameters. On the basis of
evidence gained by an international research network (COST Action
637) it appears that problems with lead in drinking water are
widespread in Europe. The full extent of the problem will only
emerge when monitoring deficiencies have been resolved. For the
time being, it has been estimated (IWA, 2010) that up to one in
four children in Europe could be at risk from lead in drinking
water, but not in the UK because of the comprehensive actions
taken.
Pipe replacement
The ultimate solution to the lead in drinking water problem
would, very simply, be to replace all the lead pipes (water
suppliers and property owners), but this is not without a range of
problems:
- In many cases, the ownership of the lead piping is split
between the water supplier and the property owner, complicating
legal aspects
- Consumers do not perceive lead in drinking water to be a
problem (as it cannot be seen, tasted or smelt) so are therefore
reluctant to take expensive (and disruptive) action
themselves.
- The cost of replacing lead pipes is high - for example, the
cost of replacing all lead pipes in the UK has been estimated at
between £8 billion and £10 billion.
- The density of properties with lead piping can be as high as
75% in many towns and cities, and any concerted replacement
programme would cause considerable disruption to road users and
property owners.
- A question also arises: is it acceptable to simply leave old
lead pipes in the ground or should they be removed and disposed of
properly?
The long-term aim must be to replace all lead pipes.
However, it will be necessary to recognise the deep reluctance of
many property owners to replace their pipes (due to the inherent
cost, disruption and inconvenience). Consideration should be given
to new regulations that would require a dwelling to be certified as
lead pipe free at the time of its sale or letting; this would take
25 or more years to be fully effective, but costs would be spread
(water companies would be required to replace their lead pipes at
the same time). It is appropriate that replacement of lead pipes in
buildings used by the public (eg. hospitals, schools, offices)
should be enforced by regulations, over a shorter, albeit realistic
timescale. In appropriate circumstances, grant aid may need
to be available.
Consumers can also be encouraged to take other measures
themselves to reduce exposure. Flushing standing water from the
pipework after a period of non-use has been advocated but recent
research suggests that it would be necessary to flush pipework
before every period of use, resulting in considerable increases in
water consumption. Another option, widely used in the US, is to fit
simple point-of-use treatment (filtration/absorption) devices;
however, it can be difficult to gauge when such treatment units
have become exhausted and therefore ineffective.
Particularly in small and very small water supply systems, lead
pipe replacement may be preferred as the strategic means for
achieving compliance. However, benefits will be limited if a water
supplier replaces its part of the lead connection pipe but the
property owner does not replace his/her part of the connection pipe
and internal plumbing. Indeed, lead concentrations can increase in
such circumstances, at least in the short term. The
opportunistic replacement of lead connection pipes by water
companies, for example during mains refurbishment programmes,
should be considered carefully as part of a routine risk assessment
and any perceived risks should be mitigated. Water suppliers
should continue to take active steps in their area to prevent the
use by plumbers of lead-containing solders in drinking water
systems and should actively promote the use of brass fittings that
have a lead content no higher than 0.25% in recognition of a recent
tightening of the definition of "lead-free" in the US. For small
and very small privately owned water supplies, total lead pipe
replacement should be pursued by the regulatory agencies. In such
cases, any problems with lead in drinking water will be amplified
when water quality is poor and inadequately treated.
Orthophosphate
dosing
An alternative preventative approach is to reduce the
plumbosolvency of the water supplies. For low alkalinity supplies
(<50 mg/l as CaCO3) much can be achieved by
increasing the pH to above 8.0 but UK experience has shown that the
dosing of orthophosphate (a corrosion inhibitor) in the typical
range 0.5 to 1.0 mg/l P is also required if the new European
standards are to be achieved to a substantial degree. High
alkalinity waters do not respond sufficiently to pH elevation and
plumbosolvency reductions are achieved by orthophosphate dosing
alone, albeit at a higher dose (typically 1.0 to 1.5 mg/l
P).
Orthophosphate dosing must be optimised in order to achieve
substantial compliance with the tighter standard of 10 µg/l whilst
minimising environmental impacts of the additional orthophosphate
on receiving waters. Such optimisation is not straightforward
because of the limitations inherent in sampling and additional
techniques should be considered (such as corrosivity testing,
solubility modelling and zonal emission modelling). Optimisation of
orthophosphate dosing is largely concerned with establishing the
correct concentration, complicated by changing seasonal
requirements and by the fact that all water supply areas have their
own specific requirements, as determined by how much lead piping is
present and by the plumbosolvency of the supplies. Optimisation
also requires the correct pH to be maintained, natural organic
constituents of the water to be minimised and the distribution
network to be kept free from iron discolouration problems.
Optimised orthophosphate dosing will continue to be necessary
until such time as all lead pipes have been removed, including
those owned by consumers. Particularly in the light of WHO's
booklet on Childhood Lead Poisoning and FAO/WHO's withdrawal of the
provisional tolerable weekly intake guideline value for lead on the
grounds that it was inadequate to protect against IQ loss, there is
no scope for water companies in the UK to relax the very high
standards of corrosion control that they have achieved in recent
years.
The UK approach
In the UK corrective treatment has been promoted, as opposed to
the widespread replacement of lead pipes, as an appropriate first
stage of achieving the new European standards for lead in drinking
water. As a consequence, about 95% of the UK's public water
supplies are now dosed with orthophosphate and it has become
apparent that very substantial compliance has been achieved with
not only the interim standard of 25 µg/l but with the future
standard of 10 µg/l in England and Wales, 99.8 % of random daytime
samples complied in 2010 with the current lead standard of 25 µg/l
and 99.0 % complied with the future lead standard of 10 µg/l. The
positions in Northern Ireland and Scotland are moving towards these
levels of compliance. The DWI (2010) has recently issued further
guidance to water companies, based on an integrated package of
measures to mitigate lead risks, including responding to regulatory
failures, requiring owners of public buildings to take appropriate
action, opportunistic removal of lead communication pipes, working
with health protection teams to identify vulnerable consumers, and
raising awareness in consumers and other stakeholders.
Discussion
The UK's widespread use of orthophosphate is consistent with
practice in the USA but contrasts to many other European countries
where the dosing of orthophosphate to water supplies is considered
to be unacceptable on environmental grounds. The environmental
concerns relate to the eutrophication of water bodies and the
possible prolific growth of algae, some of which can be toxic.
Whilst this linkage is of course possible, the overall perspective
relating to the orthophosphate dosing of water supplies appears to
be missing. Whereas the concentration added to water supplies for
the purpose of reducing plumbosolvency is most commonly about 1
mg/l P, the sewage derived from water use commonly has an
orthophosphate concentration of about 10 mg/l P, i.e. ten
times as much (this is derived mostly from human waste and to a
lesser extent from detergents). Therefore orthophosphate dosing of
water supplies is not critical with respect to eutrophication and
the European stance poses a number of questions:
- If eutrophication is such an important issue, why has it not
been considered necessary to remove phosphate from treated sewage
effluent for the great majority of sewage treatment works?
- In cases where nutrients are considered to be a problem (or a
potential problem) why does existing European legislation require
phosphate removal down to only 1 or 2 mg/l P (depending on size of
works) when it is well known that the limiting concentration of
phosphate in receiving waters is below 0.01 mg/l P?
It can be concluded that the environmental aspects of dosing
phosphate to water supplies need to be properly balanced with the
public health consequences of not taking comprehensive action to
reduce plumbosolvency, at least in the short to medium term.
Whichever corrective actions are taken, the intention must be to
protect public health, regardless of any complications arising from
the split ownership of lead pipes.
The possibility of WHO tightening its guideline value for lead
in drinking water needs to be considered. Whereas compliance with
the current guideline value (and future EU standard) of 10 µg/l has
been shown to be technically feasible, at least to a level of 99%,
compliance with a lower guideline value may not be practicable. It
will be essential for water practitioners, health officials,
regulators and policy makers to work closely together on any such
developments.
July
2011
Note: CIWEM Policy Position Statements (PPS) represents the
Institution's views on issues at a particular point in time.
It is accepted that situations change as research provides new
evidence. It should be understood, therefore, that CIWEM
PPS's are under constant review, that previously held views may
alter and lead to revised PPS's.
References
Drinking Water Inspectorate (2010). Guidance on the
implementation of the Water Supply (Water Quality) Regulations 2000
(as amended) in England. September 2010.
Hoekstra, E J, Aertgeerts, R, Bonadonna, L, Cortvriend, J,
Drury, D, Goossens, R, Jiggins P, Lucentini, L, Mendel, B,
Rasmussen, S, Tsvetanova, Z, Versteegh, A and Weil, M, 2008. The
advice of the Ad-Hoc Working Group on Sampling and Monitoring to
the Standing Committee on Drinking Water concerning sampling and
monitoring for the revision of the Council Directive 98/83/EC.
European Commission Joint Research Centre, EUR 23374 EN - 2008.
International Water Association (2010a). Best Practice Guide on
the Control of Lead in Drinking Water. IWA Publishing. ISBN
9781843393696.
International Water Association (2010b). Guide for Small
Community Water Suppliers and Local Health Officials on Lead in
Drinking Water. Editor, IWA Publishing. ISBN 13 9781843393801
International Water Association (2011). Comments on the WHO
Booklet "Childhood Lead Poisoning". Available to download from the
IWA Water Wiki via www.iwahq.org
World Health Organization (2010). Booklet on Childhood Lead
Poisoning. ISBN 978 924 150033 3
World Health Organization (2011). Guidelines for Drinking Water
Quality. 4th Edition. ISBN 978 924 1548151
