Q: What happened in Flint to cause the corrosion problem, and how damaging was it?

A: A change of water source led to the introduction of very aggressive water that caused grossly contaminated water at the tap from its corrosive action on existing piping. Lead was also being extracted from old lead pipe surfaces. However, indications of serious water quality problems existed well before the change. Apparently, the problem has not been completely resolved even though the municipality has returned to the original source.

The water rates for Flint residents using water purchased from Detroit were very high, and Flint was in serious financial trouble. In 2014, the municipality decided to return to producing its own water to reduce costs by making a temporary shift to the Flint River while laying a pipe to an intake in Lake Huron, but they did not do it properly. As a result, consumers have been suffering because of the very poor water quality. It apparently was and might still be brown or orange and contain mobilized lead in some cases, even though the city switched back to Detroit water in October 2015. During that time, consumers were advised that the water was safe, which is debatable, but it certainly could not be considered palatable.

A recent report from the Michigan Department of Health and Human Services indicated that 2.5 percent of 3,351 Flint children whose blood levels were tested between Oct. 1, 2015, and Jan. 22, 2016, were above 5 micrograms per deciliter (µg/dl). In the third quarter of 2014, about 7 percent were above 5 µg/dl. In 2013 testing before the water change, 2.2 percent of children tested in Genesee County, where Flint is located, exceeded 5 µg/dl, and 0.2 percent exceeded 10 µg/dl. That same year in Detroit, 8 percent exceeded 5 µg/dl, and 1.4 percent exceeded 10 µg/dl. Both communities have a lot of older housing, but I have not been able to learn whether the pre-1978 lead paint contributions to the Flint statistics have been determined.

As reported by a U.S. Environmental Protection Agency (EPA) memo, the child of the mother who testified at a congressional hearing had 3 and 6.5 µg/dl in blood measured in early 2015. Water measurements in some homes reported lead levels in the 100s to 1,000s of µg/l in water, and iron was more than 3.3 mg/l (the standard is 0.3 mg/l). A possible reason that community blood lead levels are not higher is that the water tasted and looked so bad that most people did not drink it, even though authorities told them it was safe. Actually, the greater concern could be the possibility that the corrosive water allowed for the mobilization of Legionella bacteria from biofilms and sediments that increased the risk of legionellosis from inhalation of aerosols.

The Flint case should never have happened. The water supplier did not properly treat the water. The water system needed to follow the EPA Lead and Copper Rule (1991), and the Michigan regulators should have enforced it because those responsibilities are delegated to the state under the national Safe Drinking Water Act. Eventually, the EPA should have been more aggressive in the follow-up.

The Flint situation is somewhat similar to what happened in Washington, D.C., about 15 years ago but for different technical reasons. In Washington, the system changed from free chlorine to combined chlorine residual. That caused a change in the water chemistry that solubilized lead salts and resulted in exceeding the Lead and Copper Regulation. The Washington problem was not nearly as severe as Flint’s. After similar national opprobrium, the problem was solved by adding a few mg/l of phosphate to the water. In the Flint case, at least part of the corrosivity problem might have been due to much higher chloride levels and different chloride/sulfate ratios in the Flint River compared to Lake Huron.

Lead’s recent health history

In the 1920s, an intense search was held for a gasoline additive that would have excellent antiknock properties so that high compression engines with much better fuel economy could be achieved. Many antiknock chemicals were evaluated including iodine, aniline, bromine, ethyl alcohol, benzene and tetraethyllead. The toxicity of tetraethyllead was the cause of major controversy. Numerous production and user workers died or developed mental health problems including insanity because of the mishandling and lack of worker safety provisions at the time. After much debate, tetraethyllead was chosen despite the acknowledged risks because of its low cost and low gasoline dosage requirement of about 1 to 1,000. The toxicity of leaded gasoline was known, but it was downplayed because some argued that the population’s lead exposure would be small and less than the amount caused by lead paint. The latter unfortunate comparison ultimately proved to be a mute argument when household lead paint was banned in 1978.

The concern levels determined by the Centers for Disease Control (CDC) for lead in blood have moved downward over time from 60 µg/dl in 1960 to the current 5 µg/dl reference level. CDC estimates that at least 97.5 percent of children, which is their metric for the reference level, are below it, so it will probably be lowered soon to the new 97.5 percent level, perhaps 3 µg/dl.

The National Health and Nutrition Examination Survey II found that the average childhood blood lead level in the U.S. from 1976 to 1980 was 16 µg/dl. That means many of us and our children had high lead exposures during the leaded gasoline days. The EPA’s required introduction of catalytic converters in 1975 necessitated the phasing out of leaded gasoline, and it was complete by 1996. As leaded gasoline was phasing out, the child blood levels began dropping, and today the average is around 1 µg/dl. The EPA should be applauded for solving most of the lead exposure problem.

Most remaining exposure potential is from old lead paint that can cause high blood levels when children are exposed to leaded dust such as during renovations of older houses. In addition,  some other water suppliers are probably not following the corrosion control law. The CDC said that subtle IQ loss can occur at around 5 µg/dl. At the reference level and above, identification and elimination of the lead source is recommended. Medical intervention chelation therapy is considered at 45 µg/dl, according to the CDC.

Lead and Copper Rule

The EPA’s Lead and Copper Rule regulation was promulgated in 1991 and updated in 2000 and 2007. It requires water suppliers to regularly test for excessive corrosivity in drinking water at the tap in highest risk distribution system locations. Testing is performed on water that has been stagnant overnight or for at least 6 hours. A 1-liter first draw sample is collected, and if more than 10 percent of the samples exceed the lead action level of 15 µg/liter or the copper action level of 1.3 mg/l, the system must introduce corrosion control procedures and public notification. If the corrosion control is not successfully achieving the defined lead action level, then the system must begin a lead service line replacement program of 7 percent every year.

It is important to recognize that the action level is not a maximum contaminant level. It is a benchmark screening value to indicate excessive corrosion potential for the water. Since it is a 1-liter stagnant first draw sample, it will include water in contact with the usually lead brass tap and some length of plumbing that includes solder joints, which would be high lead solder if they were installed before 1986 when lead solder was banned by statute.

The World Health Organization’s lead guideline and the European Union’s drinking water lead directive are 10 µg/l. Some people have misinterpreted that to mean that they are more protective than the EPA action level, but they are not. Those measurements do not require stagnant first draw water as the EPA’s screening test does, but they would allow typical running water sampling. Therefore, they might allow continuous exposure to water at 10 µg/l or even more.

Congressional hearing

In a House Oversight Committee hearing on Feb. 3, 2016, those who testified were the EPA’s Joel Beauvais; Virginia Tech professor Marc Edwards, who was critical of the situation and city; those in state and federal roles; and the mother of a child in Flint who felt that her child was harmed by the lead in the water. Briefly, Republicans were blaming the city, and Democrats were blaming the governor. Several members pressed the EPA to move to revise the Lead and Copper Rule as soon as possible. The EPA said that it was scheduled for 2017. Interestingly, Edwards and the EPA representative said that the Flint problem would not have occurred if Flint had done what was required to be in compliance with the existing Lead and Copper Rule. No one seemed to hear that.


The Lead and Copper Rule could be strengthened with limited effort. First, partial lead service line replacements that include the public portion, but not the private segment, are not generally a good idea. In Washington, D.C., lead levels peaked and then stabilized within a few weeks of public lead service line replacements. Bottled water or filters should be provided in the interim.

Second, history shows that delegation to the resident to conduct uncontrolled monitoring is too difficult and fraught with opportunities for error. A method for controlled sampling must be used, probably on site by utility or health department personnel with advance approval from residents. Another perhaps better possibility is to use simulated testing of local lead line loops in a laboratory to determine the intrinsic corrosivity of the system’s water to a lead line.

Third, the sampling protocol using stagnant first draw water is good with respect to plumbing lead, but it would only be influenced to some degree by the service line if a leak allowed some continuing flow from the service line. The simplest improvement would be to add a second draw sample when the temperature change indicates that service line water is being accessed. The District of Columbia Water and Sewer Authority also conducted second draw sampling and showed that the phosphate corrosion control process was successful.

Lead service lines to buildings would not exist because the lead pipe capacity is too small, so first draw stagnant samples would probably be fine for determining the effects on plumbing in an apartment building.

Read more coverage of the Flint water crisis.

Here is my advice to consumers and water treatment professionals helping their clients:

  • Check to see if a lead service connection exists. Find where the outside incoming line connects to the indoor meter if one is present. Ask the water supplier for a water analysis if in doubt.
  • Do not drink first draw water regardless of lead. It will probably be warm and not taste good, and it might have extracted some material from pipe during stagnation. Let it run at least several seconds, preferably until the temperature has changed.
  • Do not make baby formula, reconstituted juices, rice, pasta or soup from first draw water or water from the hot water tap.
  • Read the water supplier’s annual Consumer Confidence Report and insist that the water supplier is following the law and managing corrosion.

Treatment technology

Corrosion control is essential at the municipal plant. Its correction is not trivial and requires case-by-case study. Typical approaches include pH, alkalinity and hardness adjustments. The addition of a few milligrams per liter of a form of phosphate has been shown to be a successful, low-cost technique for lead control in many circumstances. Apparently, a coating of relatively insoluble salts forms to passivate the lead containing surfaces.

Certified point-of-use filters and pitcher filters have been successful. Both particulate and dissolved lead removal are important. Filters or bottled water have been provided by authorities at no cost when high lead cases have been detected, and they should be used in the event of a partial service line replacement until the water has restabilized.


The social and economic consequences of the situation in Flint are real, but they have also been exacerbated by media hype. Even some presidential primary candidates have resorted to trying to take advantage of Flint’s misfortune.

From what I can glean of the Flint situation, it was certainly a breakdown of the water supplier’s responsibilities, as well as the state regulator’s. If both had carried out their legal and professional responsibilities and followed regulatory requirements from the beginning, the problem would never have happened. The EPA’s elimination of leaded gasoline has eradicated most of the U.S. population’s lead exposure as verified by extensive blood lead measurements. Lead exposure has risk and no benefit, so less is better. The Flint blood lead data that I have seen so far does not seem to indicate a large health impact, and I do not know what portion of the higher values is attributable to lead paint versus water exposures.

State regulators did not respond rapidly to require the city to comply with the Lead and Copper Rule, and ultimately EPA’s Region 5 did not push the state regulators to do what was necessary to get Flint’s water into compliance with the regulation. It would have been a different story if all three of the authorities had just followed the law as they should have and carried out their responsibilities.

Dr. Joe Cotruvo is president of Joseph Cotruvo and Associates, LLC, Water, Environment and Public Health Consultants. He is a former director of the EPA Drinking Water Standards Division.