Blood Lead and Water Treatment
Environ Health Perspect. doi:10.1289/ehp.10453 available via http://dx.doi.org [Online 11 September 2007]
Referencing: Changes in Blood Lead Levels Associated with Use of Chloramines in Water Treatment Systems
Miranda et al. (2007) recently reported the results of their investigation into the relationship between blood lead levels and residual water treatment in two locations in North Carolina. Their conclusion that " . . . the change to chloramine disinfection may lead to an increase in blood lead levels, the impact of which is progressively mitigated in newer housing" is not borne out by their analysis. Their ecologic study design cannot be used to determine causation, and their recommendation to change lead screening strategies based on their study seems premature.
Their analysis relied on ecologic assignment of drinking water exposures based on residence location, census-level exposures for housing age, and other risk factors for lead exposure. They provided no information on differences in water chemistry, such as pH or corrosivity, or on the presence of lead in the distribution systems or service lines. These characteristics are important to determine the likelihood of lead leaching, regardless of the type of residual disinfectant used. In fact, the water serving Wayne County, North Carolina, is heterogeneous. Whereas the city of Goldsboro is served by surface water sources, the rest of Wayne County is served by seven smaller sanitary districts that rely on groundwater. Further, among the groundwater sources there is considerable variability in the water quality. The Wayne Water Districts, erroneously referred to by Miranda et al. (2007) as "Wayne Water Systems," are composed of five of the seven sanitary districts in Wayne County and had 39 wells in 2006, about half of which receive no treatment. The remaining half are treated for iron removal, fluoride, chlorine, and phosphate. The pH for Wayne Water Districts water ranges from 6.5 to 7.5, whereas Goldsboro Water usually maintains a pH > 8.0.
Miranda et al. (2007) stated that they
expected that the effect of chloramines on [blood lead levels] would be less important and eventually unimportant as [they] moved into newer and newer housing stock.
However, they offered no explanation for their a priori, hypothesis of interaction. In fact, according to the U.S. Environmental Protection Agency (1993), the opposite would be true:
Lead levels decrease as a building ages. This is because, as time passes, mineral deposits form a coating on the inside of the pipes (if the water is not corrosive). This coating insulates the water from the solder.
In the categorical analysis, stratifying housing age by 25-year categories may have led to misclassification. In 1988 the Consumer Product Safety Commission (CPSC 1988) began enforcing the Federal Hazardous Substances Act restricting the use of lead solder in plumbing. The cutoffs used by Miranda et al. (2007) combine the years 1976–1988 together with newer housing stock that would not have lead solder in the plumbing. It is also curious that the tax parcel data from which they assigned housing age characteristics differs markedly from that reported in the 2000 U.S. Census (U.S. Census Bureau 2000). Where Miranda et al. (2007) reported 15.6% of Wayne County housing stock built before 1925, the U.S. Census reported just 7.6% built before 1939 (U.S. Census Bureau 2000).
Miranda et al. (2007) were unable to include 25% of records; missing these data could have biased the results. For example, if a higher proportion of the missing children were from Seymour Johnson Air Force Base, which is annexed to the city of Goldsboro and which receives water from the Goldsboro Water System, this could have overestimated the effect of switching to chloramine if the missing children had lower blood lead levels. Children who reside on military bases tend to have lower lead exposures, regardless of the housing stock (Stroop et al 2002).
Miranda et al. (2007) should have considered the possible impact of Hurricane Floyd. The September 1999 hurricane left many homeless; flooding, demolition, and construction activities could well have affected children's blood lead levels to a greater extent in Goldsboro compared with the rest of Wayne County. Indeed the raw blood lead level data show an increase county-wide in the year 2000, supporting an effect of the hurricane.
The analysis conducted by Miranda et al. (2007) is interesting, and additional studies with individual-level exposure measurements should be conducted. However, their study does not provide a basis for recommending a broad alteration of blood lead screening strategies. States need to do better to ensure that blood lead screening strategies are inclusive, especially for low-income children who are at the greatest risk of undetected elevations in blood lead levels. The recommendation of Miranda et al. (2007) to exclude certain children based on water-disinfection practices could have substantial unintended impacts. In accordance with recommendations of the U.S. Preventive Services Task Force (2007), a more prudent approach to prevent lead exposure via drinking water is that municipalities ensure careful corrosion control and remove lead service lines and distribution pipes, regardless of the method of residual disinfectant used.
The author is an employee of the City and County of San Francisco Department of Public Health; her position is funded under a work order from the San Francisco Public Utilities Commission, which switched to chloramine for residual disinfection in 2004. The San Francisco Public Utilities Commission had no role in the preparation, review, or approval of this letter.
June M. Weintraub
San Francisco Department of Public Health/Environmental Health Section
San Francisco, California
References
CPSC (Consumer Product Safety Commission). 1988. Don't Use Solder that Contains Lead for Work on Drinking Water Systems: Safety Alert. CPSC Document 5056. Available: http://www.cpsc.gov/CPSCPUB/PUBS/5056.html [accessed 5 September 2007].
Miranda ML, Kim D, Hull AP, Paul CJ, Galeano MA. 2007. Changes in blood lead levels associated with use of chloramines in water treatment systems. Environ Health Perspect 115:221–225.
Stroop DM, Dietrich KN, Hunt AN, Suddendorf LR, Giangiacomo M. 2002. Lead-based paint health risk assessment in dependent children living in military housing. Public Health Rep 117:446–452.
U.S. Census Bureau. 2000. Profile of Selected Housing Characteristics: 2000. Data Set: Census 2000 Summary File 3 (SF 3). Wayne County, North Carolina. Available: http://factfinder.census.gov/servlet/QTTable?_bm=y&-qr_name=DEC_2000_SF3_U_DP4&-ds_name=
DEC_2000_SF3_U&-_lang= en&-_sse=on&-geo_id=05000US37191 [accessed 10 May 2007].
U.S. Environmental Protection Agency. 1993. Actions You Can Take To Reduce Lead In Drinking Water. EPA 810-F-93-001. Available: http://www.epa.gov/safewater/lead/lead1.html [accessed May 10, 2007].
U.S. Preventive Services Task Force. 2006. Screening for elevated blood lead levels in children and pregnant women: recommendation statement. Pediatrics 118: 2514–2518. Available: http://www.ahrq.gov/clinic/uspstf06/lead/leadrs.htm [accessed 10 May 2007].
Blood Lead and Water Treatment: Miranda et al. Respond
Environ Health Perspect. doi:10.1289/ehp.10453R available via http://dx.doi.org [Online 11 September 2007]
In response to our study (Miranda et al. 2007), in which we found an association between age of housing, water treatment practices, and blood lead levels, Weintraub concludes that
[A] more prudent approach to prevent lead exposure via drinking water is that municipalities ensure careful corrosion control and remove lead service lines and distribution pipes, regardless of the method of residual disinfectant used.
Unfortunately, this approach has fallen notably short as evidenced by tests of residential tap water in Washington, DC (Edwards and Dudi 2004), Greenville, North Carolina (Renner 2005), and in 2006, in Durham, North Carolina (Biesecker 2006). Each of these cities had increased levels of lead in tap water following a change in water treatment practices necessitated by a switch to chloramines for disinfection.
We stand by our hypothesis that the effect of chloramines on blood lead levels would be less important in newer housing stock. Weintraub cites a U.S. Environmental Protection Agency Fact Sheet (U.S. EPA 1993) as evidence that older buildings would pose less, not more, of a lead risk because of the protective effect of mineral deposits coating the inside of the pipe. However, as the U.S. EPA noted, lead levels decrease as a building ages only "if the water is not corrosive." An increase in the corrosivity of treated water after a switch to chloramines may expose lead that was shielded by mineral deposits (Schock 1990). This supports our reasoning that newer housing without lead service lines or lead solder and low-lead fixtures would pose less exposure risk.
We did not use an ecologic study design in our analysis. Our outcome variable was an individual measure of blood lead level, and our explanatory variables were either individual or census-level measures. We did not attempt to infer an individual-level association of variables from an association demonstrated only for aggregated variables.
We coined the phrase "Wayne Water Systems" to represent the collection of water systems in Wayne County, North Carolina, that do not use chloramines. "Wayne Water Systems" includes the five water systems that make up the Wayne Water Districts, as well as the five other active community water systems (Fremont, Fork, Pikeville, Mt. Olive, and Southern Wayne) in the county. We should have noted this in the text.
With respect to the categorical analysis, stratifying housing age by 25-year categories did not lead to misclassification of the housing, in spite of grouping together houses built before and after the ban of lead solder in 1986. We performed model iterations with several different age categories of housing and presented the best-performing model. We did run a model with housing built after 1986 as a referent group, but we found the variable of 1976–1986 statistically insignificant.
We based our finding that 15.6% of the housing stock in Wayne County was built before 1925 on tax parcel data, which we consider to more accurately represent housing age than homeowner responses to age-of-housing questions posed by the U.S. Census. We would have preferred to include all blood lead records, but it was not possible because we could not geocode incomplete addresses. However, when we compared the blood lead levels of children from geocoded and non-geocoded addresses, we did not find a significant difference. Records of children from Seymour Johnson Air Force Base were included in the analysis.
In July 2006, the U.S. EPA proposed changes to the Lead and Copper Rule that would require water systems to notify, and obtain approval from, state regulatory agencies before changing a water treatment process (U.S. EPA 2006). As the U.S. EPA noted, if a water system notifies the State after changes have already been made, there may be little or no opportunity to minimize any corrosion problems to prevent lead from leaching from plumbing components. We suggest the use of housing age as a simple metric for states to use in designing a water monitoring program, and expanding blood lead screening in advance of changes in water treatment practices.
Weintraub states that our recommendations "to exclude certain children" based on water disinfection practices could have "substantial unintended impacts." This is a misrepresentation of our recommendations. Based on the Wayne County results (and those in Washington, Greenville, Durham), we recommended that local health departments expand their scope of targeted screening in the years following the introduction of chloramines as a supplement to, not a replacement of, existing programs that are in place to provide blood lead screening services to children at risk of lead exposure. We also suggested that health departments might target more intensive outreach and education to residents of older housing, a strategy that would help focus limited resources on residences where additional lead sources may also be present.
Our recommendations are consistent with the U.S. EPA's rationale for revising the Lead and Copper Rule to require advance notification of water treatment changes, and with recommendations by water chemistry experts to closely monitor water lead levels after changing to chloramines for disinfection.
The authors declare they have no competing financial interests.
Marie Lynn Miranda
Martha Keating
Dohyeong Kim
Andrew P. Hull
Christopher J. Paul
M. Alicia Overstreet Galeano
Nicholas School of the Environment and Earth Sciences
Duke University
Durham, North Carolina
References
Biesecker M. 2006. Durham lead fear widens. News and Observer (Raleigh, NC), 13 June. Available: http://www.newsobserver.com/news/health_science/lead/story/450089.html [accessed 8 June 2007].
Edwards M, Dudi A. 2004. Role of chlorine and chloramine in corrosion of lead-bearing plumbing materials. J Am Water Works Assoc 96(10):69–81.
Miranda ML, Kim D, Hull AP, Paul CJ, Galeano MA. 2007. Changes in blood lead levels associated with use of chloramines in water treatment systems. Environ Health Perspect 115:221–225.
Renner R. 2005. Chloramines again linked to lead in drinking water. Environ Sci Technol 39(15):314A. Available: http://pubs.acs.org/isubscribe/journals/esthag-a/39/i15/html/080105news3.html [accessed 8 June 2007].
Schock M. 1990. Causes of temporal variability of lead in domestic plumbing systems. Environ Monit Assess 15(1):59–82.
U.S. EPA (Environmental Protection Agency). 1993. Actions You Can Take to Reduce Lead in Drinking Water. EPA 810-F-93-001. Available: http://www.epa.gov/safewater/lead/lead1.html [accessed 8 June 2007].
U.S. EPA (Environmental Protection Agency). 2006. National primary drinking water regulations for lead and copper: short-term regulatory revisions and clarifications; proposed rule. Fed Reg 71:40828–40863. Available: http://www.epa.gov/fedrgstr/EPA-WATER/2006/July/Day-18/w6250.pdf [accessed 4 September 2007].