BioCycle May 2016
Getting old is not for wimps — so says a bumper sticker I saw on a car. The bumper sticker was likely meant for people but the same applies to pipes. I recently listened to a web cast of the National Academy of Science’s Water and Technology Board about our drinking water infrastructure. George Hawkins, head of the DC Water and Sewer Authority, was one of the presenters. He described the pipes he has to deal with in a way that captures the message of the bumper sticker and the car to which it was affixed.
Hawkins explained that the water distribution system he had to work with was like a car that contained parts from every generation and type of automobile that had been manufactured for the last 70 years. When something went wrong, you never knew what combination of generations of hardware you would have to fix. Those generations include pipes made of different materials with different shapes and configurations. The water running through them has to meet strict standards for both appearance and safety. The standards include a range of contaminants and pathogens.
The water also has to be maintained at sufficient pressure in the pipes so that firefighters can tap into the system and fill their hoses with sufficient pressure to dose a fire. Pretty impressive — and if I had heard his talk as a stand-alone, I would have been left with the impression that he and the agency that he represents were clearly not wimps, but are closer to super heroes.
Unfortunately Hawkins wasn’t the first speaker. Marc Edwards, an engineering professor at Virginia Polytechnic was the first speaker. Dr. Edwards spoke about the recent crisis of lead contaminated water in Flint as though the local officials in Flint and the state and EPA that oversaw the water system were criminals. Low and behold, in the paper the day or two after the web-inar, I saw that in fact several municipal officials associated with the water crisis in Flint had been charged with felonies.
The Flint water crisis occurred after the source water entering the system was changed. There were many problems with the new source water, including high turbitidy, foul taste, and a high bacteria content. The bacteria in the water required high doses of a disinfectant that in turn left high levels of disinfectant residue. The new source water also had slightly different chemistry than the prior water. That slightly different chemistry in combination with the disinfectant and the absence of an additional corrosion inhibitor — all in the presence of the plumbing equivalent of car parts from the 1940s — resulted in well above regulatory limits of lead (Pb) in the drinking water for many homes.
As a result, the percentage of kids in Flint with elevated blood Pb (over the defined level of 5 µg dL-1) increased from 2.4 to 4.9 percent. If you look at the increase in selected neighborhoods, those with the equivalent of very old car parts, that increase goes from 4 percent pre water crisis to 10.6 percent. The neighborhoods with the “old car” plumbing also had higher incidences of “old car” housing and lower socioeconomic status. It is important to note that the increase in blood Pb was relatively small and generally close to the recommended limits. However, if you are a mom and your child is one of those kids with elevated blood Pb, that is likely a very minimal consolation.
Not Just Flint
The officials in Flint did the wrong thing. But from the corner that they had been backed into it likely seemed like a very reasonable alternative. All cities have aging infrastructure and insufficient funds to replace or repair it. Flint is hopefully an extreme case. I say this having heard on the news yesterday about elevated water Pb concentrations in four homes in Tacoma, Washington, not far from where I live in Seattle.
In writing this column, I also read about a similar incident in Washington, D.C. in the early 2000s. Here officials made the decision to switch from using chlorine as a disinfectant to chloramine. This was done because by-products from chlorine are potential carcinogens. However, chloramine as it degrades can also degrade brass pipes and brass contains percent concentrations of lead. When the switch was made the brass did begin to degrade and lead levels of the water increased. Lead solder also released Pb into the water. A similar increase in blood Pb as was recently seen in Flint was observed in neighborhoods with those same old plumbing car parts. It was found that the addition of a corrosion inhibitor prevented the release of Pb from the brass.
In the webcast Dr. Edwards noted that this is happening with much less fanfare in cities across the country. He was clearly passionate and clearly frustrated by the lack of action. His anger has to be put into context. As he notes in one of his publications, blood Pb concentrations had decreased by almost 80 percent in the 25 years prior to the DC water incident. This decrease was due to the elimination of Pb in paint and gasoline. Levels continue to fall. Lead in drinking water contributes less than 20 percent to a child’s body burden of this element.
On a very practical note, absorption of Pb through water on an empty stomach can be close to 60 percent of the total lead. Add some food into the mix and that falls to less than 5 percent of the total lead in the water being absorbed. So lead in drinking water constitutes a relatively small portion of a child’s exposure to this element and overall, lead levels in children have been decreasing. As of 2012 the new level of acceptable blood Pb is 5 µg dl-1, a level set by the CDC as one that 97.5 percent of U.S. children are below.
In the case of Flint, the decision to change to a less expensive water source was made by officials in a city that had lost half of its population and more than half of its revenue. At the same time, the water pipes in the city had to be kept full and ready for fires. The new water and the failure to use a corrosion inhibitor were financial decisions for a city up against a financial wall. While Flint is an extreme example of an aging and bankrupt city, all of our cities have water infrastructure that merits the words on that bumper sticker. How best to replace that infrastructure is a very complex question with no clear answer. Do we have one system for potable water and separate systems for all other uses? Do we use wastewater to fight fires? Can grey water and storm water be incorporated into our water infrastructure? These are very expensive decisions to make and ones that are difficult to redo if you get it wrong the first time.
CDC Blood Lead Levels in Children Aged 1–5 Years
Sally Brown is a Research Associate Professor at the University of Washington in Seattle and a member of BioCycle’s Editorial Board.