Lead in school drinking water: Canada can and should address this important ongoing exposure source.

Barn, Prabjit ; Kosatsky, Tom

The control of major historic sources of lead exposure, including leaded gasoline and residential paints, has lowered lead levels in children. US data indicate that the prevalence of blood lead levels (BLLs) [greater than or equal to] 10 [micro]g/dL among children 1-5 years of age decreased from 8.6% in 1998-1991 to 1.4% in 1999-2004, (1) while 2007-2009 Canadian data show that the geometric mean BLL of children aged 6-11 years was 0.90 [micro]g/dL. (2) Still, BLLs <10 [micro]g/dL have been linked to persistent deficits in intelligence as well as to neuropsychiatric disorders including antisocial behaviour. (3) A pooled analysis of seven prospective studies investigating the relationship between childhood lead exposure (from birth or infancy to 5-10 years of age) and full-scale IQ tests showed a log-normal dose-response relationship; a rise in BLLs from 20 to 30 [micro]g/dL was associated with a drop in mean IQ of 1.1 points (95% CI, 0.7-1.5), a BLL rise from 10 to 20 [micro]g/dL was associated with an IQ deficit of 1.9 points (95% CI, 1.2-2.6), and a BLL rise from 2.4 to 10 [micro]g/dL was associated with the greatest deficit of 3.9 IQ points (95% CI, 2.4-5.3). (4) The observation of health impacts at lower levels of blood lead, and the demonstration that even small reductions in BLL can have important population-level health gains, stresses the need to address continuing residual exposure sources. It has been argued that the mitigation of ongoing lead sources is strongly cost-beneficial. In the US, researchers estimated that a mean decline of 15 [micro]g/dL in children aged 1-5 years between 1976 to 1999 resulted in a gain of 2.2-4.7 IQ points per child; this gain was in turn estimated to result in economic benefits of $110-$319 billion, through increased productivity and higher lifetime earnings. (5) Although no cost-benefit analysis for drinking water could be identified, it is reasonable to assume that economic benefits would likewise accrue with the reduction of lead in school drinking water.

Children are exposed to lead through school drinking water

Elevated water lead levels exist in Canadian schools. Testing of Ontario schools in 2007 showed that 28% of 3,669 "first draw" 1L samples were above the Canadian drinking water guideline of 10 [micro]g/L, (6) as were 9% of the 3,479 1L samples taken after 30 seconds of flushing. (7) School water systems can contain high lead levels for several reasons, the most common being leaching. Lead can enter treated water systems through leaching from plumbing, including tin-lead solder and brass fittings, within the municipal water distribution system or inside the school building.

Two factors, stagnation and outlet design, are especially important for school water systems. Stagnation plays a key role in lead leaching where lead plumbing, solder or fixtures exist. Water delivered after overnight stagnation and even after shorter periods of non-use, such as between morning and midday, can contain elevated lead levels through the progressive release of lead from plumbing. (8) The design of outlets in schools can further promote leaching; drinking fountains typically contain more soldered joints and narrower piping than traditional taps, and if lead components are present, a high degree of leaching can occur. Beyond stagnation and outlet design, the roles of other factors in influencing lead concentrations in water are summarized in Table 1.

While food, consumer products and leaded dust are also important continuing sources of childhood lead exposure, drinking water intake constitutes approximately 10% of total lead exposure in 2-year-old children (11% in adults). (9) This estimate is based on a water lead concentration of 4.8 [micro]g/L and a consumption rate of 0.6 L/day; the contribution of water to total lead exposure increases with more frequent consumption and where water contains higher lead levels. Although no data on water consumption patterns in Canadian schoolchildren could be identified, the 2004 Canadian Community Health Survey suggests that 70% of children consume water on a daily basis. (10) Considering that children can spend up to 8 hours a day at school, it is reasonable to assume that some of this water consumption occurs during the school day. Additionally, initiatives to restrict soft drink sales (11) and ban bottled water sales (12) in schools may increase the importance of school sinks, fountains and coolers as sources of hydration. Consequently, some children may be exposed to lead on a daily basis through their school's drinking water, and in areas where municipal lead service pipes are the cause, residential water levels may also be elevated, further contributing to children's exposure.

The Canadian response

Ontario is the only jurisdiction in Canada to establish a regulatory framework to assess lead levels in school drinking water. All Ontario schools must test their facility's water annually; if any sample exceeds an action level of 10 [micro]g/L, schools are required to implement mitigation measures. (13) Recently, Ontario instituted a reduced testing frequency, based on risk level, thus allowing allocation of efforts towards "priority" schools. Changes to the testing requirements allow testing every three years for schools that show lead results below 10 [micro]g/L for all samples over the previous 2 years. (14)

Outside of Ontario, testing for lead in school drinking water occurs case by case, typically initiated by parental concerns (15,16) or as part of testing of residences and institutions in neighbourhoods where lead is shown to be leaching from the distribution system. (17) Health Canada (HC) provides some guidance for lead testing in schools to specifically locate the source of lead in drinking water within a building and to identify how best to proceed with remedial actions. Their technical document outlines a screening phase, which requires testing of water from each outlet, and a program phase, which requires monitoring of "high priority" outlets, following development of a school-specific corrosion control program. (18) Health Canada's sampling plan is adapted from the US Environmental Protection Agency's (EPA) guidelines, which also include diagnostic sampling techniques to determine sources of lead contamination in samples taken from different locations in the school facility and a list of refrigerated water cooler models identified as containing lead-based plumbing. (19)

Although the resources described above are valuable in developing a school-based screening and monitoring program, each has important limitations. Ontario only requires samples to be collected from a single outlet within a facility. As lead levels can vary between outlets, samples taken from a single outlet may not be representative of the building's water supply. Several reasons exist for this variability, including differences in tap and fountain fittings and differences in frequency of outlet use throughout the facility. Additionally, testing of refrigerated water coolers is excluded; this is an important oversight as refrigerated units in schools can be an important source if leaded components are present. Both HC and EPA guidelines encourage thorough sampling of outlets within the facility. The EPA guidelines, in particular, describe in-depth diagnostic sampling to determine the source of contamination; such sampling programs can be time-consuming and expensive. Schools would benefit from further direction on how to identify "priority" outlets, as well as a simplified approach to sampling "priority" schools. Differences between sampling frameworks developed by Ontario Ministry of the Environment, Health Canada and EPA are summarized in Table 2.

In order for any lead monitoring program to be effective, the roles and responsibilities of provinces, municipalities and schools must be clear and practical. Programs should consider the resources involved in monitoring and mitigation; this is particularly important considering that school districts may have limited discretionary budgets. Testing needs to be prioritized to identify schools in which elevated lead levels may exist and in which risk is highest in order to ensure optimal use of resources. Testing programs should emphasize elementary schools (which in many cases house day-care centres or pre-kindergarten programs) as lead exposure is a greater concern among younger children, (20) although it is not clear at what age children no longer represent a susceptible population. Older schools, in which lead plumbing is more likely, and neighbourhoods known to have lead service pipes, as well as schools located in areas where previous residential sampling has found elevated levels or where municipal water is "soft" or of low pH, need to be tested. Following Ontario's example, testing frequency can be based on the level of risk, to avoid burdening local health units and school boards with lower-yield testing.

Mitigation

Several options are available to decrease lead exposures through drinking water (Table 3). Flushing is often considered an effective mitigation action, but it can be time consuming, wastes water and is not effective for all school water systems. Source removal through the replacement of lead plumbing components, although associated with higher initial costs, offers a long-term, permanent solution to elevated drinking water lead levels. The advantages and disadvantages of each action should be evaluated before implementation as no one method may be feasible or appropriate for every school.

Practical research is needed

The exploration and reporting of best practices on monitoring and remediation, including the establishment of criteria to prioritize areas in which high water lead levels are likely to exist, are needed to better guide school-based lead monitoring and remediation programs. Recommendations for remediation need to be evaluated, particularly for flushing; while flushing can decrease lead levels in water over the short term, the frequency and length of flushing required to maintain low lead levels in various school environments are not well understood. In order to better estimate current risks and the potential gains that mitigation could bring, the distribution of exposure to facility water by Canadian schoolchildren should be monitored prospectively. An assessment should be conducted to apportion the various sources (including school water) in contributing to blood lead levels for both younger and older children. Finally, the effectiveness of monitoring programs needs to be evaluated at the school and provincial levels; cost-benefit evaluations should consider the costs of remediation versus the direct and indirect cost of unmitigated lead exposure.

Where do we go from here?

School drinking water can be an important source of lead exposure to a susceptible population, but at present, outside of Ontario, no mandated monitoring framework exists.

Monitoring in Ontario has shown that schools with elevated water lead levels are not uncommon, supporting the argument that all provinces and territories should consider implementing policies to reduce children's lead exposure in schools.

Acknowledgements: We thank the following people for their advice and information: Ralph Stanley, Peel Public Health; Richard Stanwick, Vancouver Island Health Authority; Vanita Sahni, BC Centre for Disease Control; France Lemieux, Health Canada; Monique Beausoleil and Julie Brodeur, Direction de sante publique de l'Agence de la sante et des services sociaux de Montreal; Mona Shum, National Collaborating Centre for Environmental Health; Steve Hrudey, University of Alberta; Stewart Irwin and Maria Roxborough, Capital Regional District Water Services.

REFERENCES

(1.) Jones RL, Homa DM, Meyer PA, Brody DJ, Caldwell KL, Pirkle JL, et al. Trends in blood lead levels and blood lead testing among US children aged 1 to 5 years, 1988-2004. Pediatrics 2009;123(3):e376-e385.

(2.) Bushnick T, Haines D, Levallois P, Levesque J, Van Oostdam J, Viau C. Lead and bisphenol A concentrations in the Canadian population. Health Reports 2010;21(3):1-12.

(3.) Bellinger DC. Very low lead exposures and children's neurodevelopment. Curr Opin Pediatr 2008;20(2):172.

(4.) Lanphear BP, Hornung R, Khoury J, Yolton K, Baghurst P, Bellinger DC, et al. Low-level environmental lead exposure and children's intellectual function: An international pooled analysis. Environ Health Perspect2005;113(7):894-99.

(5.) Grosse SD, Matte TD, Schwartz J, Jackson RJ. Economic gains resulting from the reduction in children's exposure to lead in the United States. Environ Health Perspect 2002;110(6):563-69.

(6.) Health Canada. Guidelines for Canadian Drinking Water Quality Summary Table. 2008.

(7.) Ontario Ministry of the Environment. O. Reg 243/07: 2007 Lead Data Results Release. Toronto, ON: Ministry of the Environment, 2009.

(8.) Murphy EA. Effectiveness in flushing on reducing lead and copper levels in school drinking water. Environ Health Perspect 1993;101(3):240-41.

(9.) Health Canada. Lead. 2008. Available at: http://www.hc-sc.gc.ca/ewhsemt/pubs/water-eau/lead-plomb/i-eng.php#1 (Accessed December 2, 2008).

(10.) Garriguet D. Beverage consumption of children and teens. Health Rep 2008;19(4):17-22.

(11.) Ontario Ministry of Education. Policy/Program Memorandum No. 135; Healthy Foods and Beverages in Elementary School Vending Machines. 2004. Available at: http://www.edu.gov.on.ca/extra/eng/ppm/135.html (Accessed July 14, 2010).

(12.) Board to study water ban. The Ottawa Citizen 2008. Available at: http://www.canada.com/ottawacitizen/news/city/story.html?id=97fdd0f40a6c- 418c-b1ce-5c8e8e74f578 (Accessed December 2, 2008).

(13.) Ontario Ministry of the Environment. Flushing and Testing for Lead in Drinking Water. Toronto, ON: Ministry of the Environment, 2007;20.

(14.) Ontario Environmental Registry. Updates to Lead And Drinking Water Regulations Under the Safe Drinking Water Act, 2002. 2009. Available at: http://www.ebr.gov.on.ca/ERS-WEB-External/ displaynoticecontent.do?noticeId=MTA3MTkx&statusId=MTYyNTc5 (Accessed January 21, 2010).

(15.) Father's test on school water finds twice allowable lead levels. Edmonton Journal November 17, 2003, B7.

(16.) McIntyre S. Water fountain lead levels concern parent. Gulf Islands Driftwood 2008.

(17.) Hamilton Public Health Services. Lead Water Service Pipes Information Report. Hamilton, ON: City of Hamilton, 2008.

(18.) Health Canada. Corrosion Control in Drinking Water Distribution Systems. 2007.

(19.) US Environmental Protection Agency. 3Ts for Reducing Lead in Drinking Water in Schools. Washington, DC: EPA, 2006.

(20.) Bellinger DC. Lead. Pediatrics 2004;113(4):1016.

(21.) Boyd GR, Shetty P, Sandvig AM, Pierson GL. Pb in tap water following simulated partial lead pipe replacements. J Environ Engineering 2004;130(10):1188.

(22.) Payne M. Lead in drinking water. CMAJ 2008;179(3):253-54.

(23.) Minnesota Department of Health and Section of Drinking Water Protection. Reducing Lead in Drinking Water: A Manual for Minnesota's Schools. St Paul, MN: Minnesota Department of Health, 2000;1-16.

(24.) Arizona Department of Environmental Quality. A Manual for Assessing Lead in Drinking Water in Arizona Schools and Day Care Facilities. Phoenix, AR: Department of Environmental Quality, 2004;1-25.

Received: July 20, 2010

Accepted: October 24, 2010

Authors' Affiliation

Prabjit Barn, MSc, Tom Kosatsky, MD, MPH

The National Collaborating Centre for Environmental Health, Vancouver, BC

Correspondence: Prabjit Barn, NCCEH, 400 East Tower, 555 West 12th Avenue, Vancouver, BC V5Z 3X7, Tel: 604-707-2463, E-mail: prabjitbarn@bccdc.ca Source of Funding and Disclaimer: The National Collaborating Centre for Environmental Health is funded by the Public Health Agency of Canada (PHAC). Opinions expressed in this article, however, should not be taken as representing PHAC policy.

Conflict of Interest: None to declare.

Table 1. Factors Associated With a High Degree of Lead Leaching Within
a Plumbing System *

Factor                              Comments

Long contact time                   Drinking fountains and stand-alone
                                    water coolers are associated with
                                    intermittent use and longer
                                    stagnation periods.

Older plumbing systems              Older plumbing systems may have
                                    lead-based components.

Lead pipe length                    Longer pipes increase contact time
                                    between water and plumbing and may
                                    increase leaching.

Smaller diameter pipes              Pipes of smaller diameter, such as
                                    those used in water fountains,
                                    increase contact time between water
                                    and plumbing.

Low pH                              The pH is a measure of the hydrogen
                                    ions in water. Water with higher pH
                                    is associated with less leaching,
                                    especially if water is not well
                                    buffered. A higher pH can also
                                    increase the effectiveness of
                                    corrosion inhibitors.

Low alkalinity                      Alkalinity is a measure of
(as differentiated from pH)         bicarbonate, carbonate or hydroxide
                                    compounds in water. Higher
                                    alkalinity will buffer the pH of
                                    water and help to form a protective
                                    scale lining along pipes.

Absence of corrosion inhibitors     Corrosion inhibitors, which are
                                    introduced to water systems at the
                                    municipal treatment level, form a
                                    protective scale lining along
                                    pipes.

* Assuming lead-containing plumbing is present.

Table 2. Differences Between Monitoring Frameworks for Lead Levels in
School Drinking Water Developed by the Ontario Ministry of the
Environment, the US Environmental Protection Agency (EPA), and Health
Canada

Organization              Action               Stagnation   Sample
                          Level(s)             Period       Volume

Ontario Ministry                               [greater
of the Environment (13)   10 [micro]g/L        than or      1L
                                               equal to]
                                               6 hours

Health Canada (18)        1st: 20 [micro]g/L   [greater     250 mL
                          2nd: 10 [micro]g/L   than or
                                               equal to]
                                               8 hours

EPA (19)                  20 [micro]g/L        [greater     250 mL
                                               than or
                                               equal to]
                                               8 hours

                          No. of               Sampling Method
                          Samples

Ontario Ministry
of the Environment (13)   Two                  Samples collected from
                                               single outlet.

                                               A "first draw" sample is
                                               collected. A second
                                               flushed (30 seconds)
                                               sample is collected
                                               approximately 35 minutes
                                               after the first sample.

Health Canada (18)        Screening phase:     "First draw" samples
                          All outlets          collected from all
                                               outlets. Follow-up
                                               sampling is conducted
                                               for outlets exceeding
                                               the first action level
                                               (AL).

                          Program phase:
                          High-priority        For follow-up sampling,
                          outlets              outlets are flushed for
                                               only 30 seconds * prior
                                               to sample collection.
                                               Samples must not exceed
                                               second the AL.

EPA (19)                  All priority         Initial sampling is
                          outlets (number      conducted of all
                          not specified)       priority outlets.

                                               Follow-up sampling is
                                               conducted for outlets
                                               exceeding the AL.

                                               For follow-up sampling,
                                               outlets are flushed for
                                               30 seconds prior to
                                               sample collection.

* The 1-minute flushing value found in the 2007 document should read 30
seconds flushing (Personal communication, France Lemieux, Water, Air
and Climate Change Bureau, Health Canada, August 27, 2009).

Table 3. Summary of Different Approaches to Dealing With Drinking Water
Found to Be Above the Sampling Strategy Action Level

Approach                 Result                  Comments

Replacing lead-          [down arrow] Lead       Represents the ideal
containing plumbing      levels & exposure       approach to dealing
with certified                                   with lead
fittings *                                       contamination, but due
                                                 to high costs, is not
                                                 typically implemented.

                                                 Extensive flushing is
                                                 required after partial
                                                 replacement of lead
                                                 pipes or service lines
                                                 due to the release of
                                                 lead particles. (21)

Altering water           [down arrow] Lead       At the municipal
chemistry                levels & exposure       treatment level, pH
                                                 can be increased,
                                                 alkalinity adjusted,
                                                 and/or corrosion
                                                 inhibitors can be
                                                 added.

Regular flushing of      [down arrow] Exposure   Flushing should only
plumbing system                                  be used for temporary
                                                 mitigation; can be
                                                 time consuming and is
                                                 associated with use of
                                                 large volumes of
                                                 water.

                                                 Flushing must be
                                                 conducted
                                                 systematically in the
                                                 mornings and after
                                                 weekends and holidays.

                                                 Given the lack of
                                                 experimental data, it
                                                 is not clear how long
                                                 flushing must occur
                                                 for lead levels to be
                                                 significantly reduced,
                                                 as well as how factors
                                                 such as plumbing
                                                 characteristics,
                                                 locations of lead
                                                 contamination, and
                                                 water chemistry
                                                 influence required
                                                 flushing times.
                                                 Recommended flushing
                                                 times are 1-5 minutes
                                                 for individual
                                                 fountains, (22-24) 10
                                                 minutes for entire
                                                 systems within a
                                                 building (23,24) and
                                                 15 minutes for
                                                 refrigerated units.
                                                 (24)

Use of only cold-        [down arrow] Exposure   Cold water is
water taps                                       associated with less
                                                 leaching than hot
                                                 water.

Alternative drinking     [down arrow] Exposure   Alternatives may come
water sources                                    with additional
                                                 concerns, such as
                                                 generation of plastic
                                                 waste with bottled
                                                 water.

Water filtration         [down arrow] Lead       Point-of-use filters
                         levels & exposure       are installed at
                                                 individual fountains.
                                                 Filters should contain
                                                 activated carbon to
                                                 remove dissolved lead
                                                 in water.

                                                 Appropriate, certified
                                                 filters must be used
                                                 in order to
                                                 effectively remove
                                                 lead from water.
                                                 Proper installation
                                                 and filter maintenance
                                                 is also required,
                                                 including daily
                                                 flushing to remove
                                                 trapped bacteria.

* Health Canada recommends the use of NSF International (NSF)/American
National Standards Institute (ANSI) health-based performance standard
(NSF/ANSI Standard 61) certified fittings.