Flint Michigan was not an aberration nor was it the worst incidence of lead in drinking water supplies, but rather some combination of determined population, blatant misrepresentation by public officials, and public sentiment allowed Flint to become the poster child for lead in drinking water. In a 2017 examination of data, Reuters found 3,000 communities elevated lead in drinking water.
While Flint’s corrosive drinking water source and failure to have a corrosion control may or may not be an outlier among modern municipal water systems, prior research by Kelsey J. Pieper PhD USDA-NIFA Postdoctoral Fellow at Virginia Tech found that in a group of 2,146 samples from the Virginia Rural Household Water Quality well testing program 19% of the tested systems had elevated lead concentrations (above 15 μg/L) and 12% had elevated copper concentrations (above 1.3 mg/L) in the first draw. The high lead levels during the Flint crisis were the same as she found in some homes dependent on private wells in Virginia. When Dr. Peiper put up the chart below at a groundwater conference last spring, I was surprised.
Dr. Peiper and the other authors found that the 90th percentile water lead levels in Flint during the “Water Crisis” and the lead levels found in Virginia wells were almost identical at 26.8 and 26.7 micrograms /L respectively. The 99th percentile water lead levels in Flint were 118.9 micrograms/L and in the Virginia well group was 95.0 micrograms/L. However, the U.S. Environmental Protection Agency (USEPA) Lead and Copper Rule lead action level of 15 μg/L is not a health-based standard, rather it is used to identify system-wide contamination. There is no safe level of lead exposure. Water lead levels as below 5 micrograms/L can increase a child’s blood lead level and cause permanent damage to biological and developmental processes.
Lead leaches into water primarily as a result of corrosion of plumbing and well components. Corrosion control techniques such as adjusting pH or alkalinity that are commonly used in public systems are not common in private wells where the decision to install and maintain treatment is solely the prerogative and responsibility of the homeowner. As a result, though 26% of the private wells had pH outside the neutral range of 6.5-8.5 (and 89% of these were below 6.5), only 5% of private well systems had acid neutralizers installed to control pH and corrosion within the home and 3% had reverse osmosis units that could remove lead among other contaminants. Lead does not exist in in most groundwater, rivers and lakes- the source water for most municipal and private water supplies. Instead, lead in drinking water is picked up from the pipes on its journey into a home and based on the recent research by Dr. Peiper from the metal components of a well.
The presence of lead in drinking water in homes supplied by both municipal service and private wells has been linked to the corrosion of lead-bearing plumbing components. In older homes the water service lines delivering water from the water main in the street into each home were once commonly made of lead. This practice began to fade by the 1950’s but was legal until 1988. Lead was also used to solder copper pipes together before 1988 (when the 1986 ban on lead in paint and solder went into effect). Also until very recently (2011 Reduction of Lead in Drinking Water Act) almost all drinking water fixtures were made from brass containing up to 8% lead, even if they carry a plated veneer of chrome, nickel or brushed aluminum and were sold as "lead-free." So even homes built with PVC piping in the 2000’s may have some lead in most of the faucets.
In Dr. Pieper’s study of private well supplied homes, flushing for 5 minutes reduced lead concentrations below 15 μg/L. However, 2% of households experienced an increase in lead concentrations with flushing suggesting that there may be other components within the well and plumbing system that release lead and/or particulate lead and may have been mobilized. In a second study in North Carolina, the Macon County Health Department in North Carolina found county-wide water lead contamination in private wells due to corrosion of galvanized well components. In their analysis of 29,30 First draw samples collected at the wellhead between 2008 and 2012 they found that 55 of 398 (14%) of newly constructed wells exceeded the Lead and Copper Rule lead action level, with concentrations reported as high as 191 μg/L, exceeding the Flint Michigan 99th percentile.
During follow-up testing in 2013, the water lead levels varied based on sampling location within the home and flushing intervals. If the lead was coming from the plumbing or dissolved lead shorter flushing produced good results. However if lead was coming from the well or particulate lead, sporadic spikes were seen. The result was in site-specific flushing recommendations for each home. The unique water lead pattern(s) associated with
corrosion of components in the well may impact the efficacy of current flushing and treatment remediation recommendations. Dr. Pieper and the other scientists feel that in order to develop effective remediation and prevention additional work must be done to increase our understanding of the mechanisms of lead release in well systems.
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