What Actually Caused the Flint Water Crisis?

By Alyssa DiGirolamo

Water flowing from a faucet in a hospital in Flint, Michigan [10].

I first read about the Flint water crisis when it was breaking news in 2015, although I didn’t know just how complex the story was until I got to college. I studied Civil and Environmental Engineering at UC Davis, now using what I learned to design wastewater treatment facilities and study water treatment methods and technologies. While in one of my undergraduate courses at UCD, the professor presented a detailed timeline of events and allowed us to fill in the blanks where we could identify any mistakes regarding the city’s management of their drinking water. Through this exercise, I realized how the story of Flint was just as much an environmental crisis as it was an environmental justice issue, spanning over decades and involving multiple agencies who continuously neglected the health of Flint River and the citizens who depended on it.

The story of Flint requires some context, including an overview of the city’s socioeconomic history. In the 1980s, Flint’s median income for young workers was the highest in the nation thanks to its status as a hub for manufacturing and steel production[2]. As blue-collar work started to leave Michigan, however, Flint’s population began experiencing higher rates of unemployment, depopulation, and food insecurity[11]. As of 2010, about 40% of the population lived in poverty, only 12% of people 25 and older held a bachelor’s degree or higher, and 45% of homes were renter-occupied[15]. By 2011, the city had accumulated a $25 million dollar deficit and was considered incapable of making any further financial decisions[6]. The state was handed control of the city’s budget and began making cost-saving maneuvers, which included switching the city’s drinking water provider from the Detroit Water and Sewerage Department (DWSD) to the Karegnondi Water Authority (KWA). Although this move was projected to save the city $200 million over 25 years, it required temporary use of the Flint River as the city’s primary drinking water source while the permanent connection to KWA was under construction[9].

The Flint River was historically used as an industrial waste stream site for lumber mills, chemical plants, and automobile manufacturing sites, eventually serving as an outfall location for the city’s wastewater treatment plant[13]. Years of neglect left the Flint River polluted from these sources and others, including surface runoff from rain and snow. All of these factors can introduce potential carcinogens and water-borne pathogens to the water, making it more difficult to treat.

Photo of the Blue Ribbon Carriage Factory in Flint [13].

Almost immediately after switching to the Flint River in April 2014, residents began reporting foul-tasting, brown, and smelly water coming from their faucets, along with skin rashes[11]. The city tested the water and measured high levels of coliform bacteria—a type of organism that may not be harmful itself, but is an indicator of other, potentially disease-causing pathogens. This preceded two confirmed outbreaks of Legionnaires Disease, an illness caused by the Legionella pneumophila bacterium, that infected at least 87 people and killed 12 [12]. Legionella pneumophila is naturally present in freshwater sources, but can spread into improperly maintained drinking water systems when the water lacks enough chlorine disinfectant. It was later proven that 80% of these cases were linked to decreased levels of chlorine in Flint’s tap water, the cause of which would not be known for some time[3].

Chlorine dosing is the most common method for disinfecting drinking water worldwide due to its affordability and efficacy in inactivating many kinds of bacteria and viruses[16]. A chlorine compound, usually sodium hypochlorite or chlorine gas, is added to the water just prior to being discharged from the treatment plant. Hypochlorous acid and hypochlorite ions penetrate the unwanted organism’s cell membrane, preventing DNA replication and cell respiration*. The chlorine dose required for disinfection is calculated such that residual chlorine compounds will remain in the water distribution system to prevent the growth of any pathogens post-treatment. However, chlorine dosing is a sensitive process that can be impacted by the presence of unknown organics or other harmful compounds in the water. 

* A more detailed explanation of chemical relationships between elemental chlorine and water can be found here.

In August 2014, the city issued boil water advisories and increased the chlorine dose without investigating what caused the low concentration. This allowed high levels of residual chlorine to react with organic matter in the water and produce a type of disinfection byproduct: trihalomethanes. Trihalomethanes are a group of four carcinogenic compounds—most commonly tribromomethane (chloroform)—that impact the kidneys, lungs, liver, and heart[14]. In response to elevated levels of trihalomethanes, the city reduced their chlorine dose, which triggered the second of the two Legionnaires Disease outbreaks in Flint. At this point, the nearby General Motors plant discontinued use of Flint River water in their manufacturing processes, citing its corrosivity to their engine parts. 

Percentage of free chlorine samples reading under the minimum 0.2mg/L threshold required for treatment and reported Legionnaires Disease cases from 2014-2015 [3].

DWSD offered to reconnect the city to its distribution system in January 2015, but the city declined, stating that their water was safe[3]. In February, numerous tests around the city found lead levels above the federal action limit of 15 parts per billion (ppb)—including multiple samples reading over 100 ppb and one reading over 1000 ppb[7]. For months, residents and researchers from Virginia Tech continued to expose the water crisis, while city, state, and EPA officials downplayed the severity and omitted test data. In September, a pediatrician from Michigan State University reported an increase in blood lead levels above the CDC reference value in children 5 years and younger, which was correlated to homes with lead in their tap water[8]. Childhood lead exposure can cause brain and nervous system damage, delayed development, and behavioral or learning problems. The city issued a lead advisory one day after the report was released and switched back to DWSD in December—nearly 20 months after the initial transition to Flint River water. 

90th percentile readings of water lead level (WLL) in Flint distribution system sampled from 2012-2017 [5].

Nearly seven years later, the cause of the water crisis is widely understood to be a combination of factors that are closely related:

1. The city of Flint failed to continue implementing a corrosion inhibitor in its water after switching from DWSD to the Flint River. Many researchers highlighted this as a major point of failure during the height of the crisis, but were largely ignored by government officials. Water from DWSD was treated with orthophosphate, which reacts with lead pipes, creating lead (II) phosphate and forming an insoluble and impenetrable layer on its surface[1]. The addition of orthophosphate needs to be continuous, or the layer will begin to dissolve and allow the lead surface to be exposed and corroded*. 

2. Treated Flint River water contained elevated levels of chloride, which is corrosive when introduced to some metals, including lead[3]. Since there was no steady flow of orthophosphate into the water, chloride ions began to dissolve the lead (II) phosphate layer and corrode the surface of the pipes. Lead ions also break down chlorine disinfectant, making the water more susceptible to bacterial growth. Most of the chloride was later connected to de-icing or salting of nearby roads during winter, which allows sodium chloride to enter the Flint River as snow melts. 

3. Pre-treated Flint River water also contained high levels of total organic carbon (TOC), which promotes growth of sulfate-reducing bacteria—a family of bacteria that are highly corrosive to iron[3]. These bacteria, along with the lack of orthophosphate and elevated chloride levels, caused iron distribution pipes to corrode as well. When iron pipes are exposed to water, the iron reduces elemental chlorine to chloride ions, which causes residual chlorine to drop[1]. This, along with lower chlorine levels in the lead pipes, could have caused the outbreak of Legionella pneumophila. 

* A more detailed analysis of corrosivity in Flint’s drinking water can be found here.

[10]

Lead concentrations in Flint’s tap water remained elevated long after switching back to DWSD due to the severity of the damage. Overall, about 140,000 Flint residents were exposed to lead and other contaminants in their tap water, including 6,000 to 12,000 children[1]. Many attribute this widespread impact to the slow—and sometimes nonexistent—response by local, state, and federal agencies*. Impacted homes were unable to use their tap water for years before seeing considerable water quality improvements. Today, more than 25,000 water service lines in Flint have been inspected and more than 85% of those have been replaced, with lead concentrations remaining within federal limits[4]. Despite this, some Flint residents refuse to drink from their taps, citing distrust in their local government. Can you blame them?

* A detailed timeline of governmental actions during and after the Flint water crisis can be found here.

References

[1] A. Dingle, “The Flint Water Crisis: What's Really Going On?,” American Chemical Society, Dec-2016. [Online]. Available: https://www.acs.org/content/acs/en/education/resources/highschool/chemmatters/past-issues/2016-2017/december-2016/flint-water-crisis.html.

[2] D. Thompson, “The Richest Cities for Young People 35 Years Ago-and Why They Fell Apart,” The Atlantic, 03-Dec-2015. [Online]. Available: https://www.theatlantic.com/business/archive/2015/02/for-great-american-cities-the-rich-dont-always-get-richer/385513/.

[3] “Flint MI -- Fatal Disruption in a Drinking Water System,” Flint water crisis. [Online]. Available: http://www.sedimentaryores.net/Pipe Scales/Pb scales/Flint_case_history.html.

[4] H. Winchester and A. Ainsworth, “6 years later: Where things stand in the Flint water crisis,” Click On Detroit, 24-Apr-2020. [Online]. Available: https://www.clickondetroit.com/consumer/help-me-hank/2020/04/24/6-years-later-where-things-stand-in-the-flint-water-crisis/.

[5] K. Drum, “A Brand New Look at Lead Contamination in Flint,” Mother Jones, 30-May-2019. [Online]. Available: https://www.motherjones.com/kevin-drum/2019/05/a-brand-new-look-at-lead-contamination-in-flint/.

[6] M. Denchak, “Flint Water Crisis: Everything You Need to Know,” NRDC, 08-Nov-2018. [Online]. Available: https://www.nrdc.org/stories/flint-water-crisis-everything-you-need-know.

[7] M. Edwards, “Our sampling of 252 homes demonstrates a high lead in water risk: Flint should be failing to meet the EPA Lead and Copper Rule,” Flint Water Study Updates, 08-Sep-2015. [Online]. Available: http://flintwaterstudy.org/2015/09/our-sampling-of-252-homes-demonstrates-a-high-lead-in-water-risk-flint-should-be-failing-to-meet-the-epa-lead-and-copper-rule/.

[8] M. Hanna-Attisha, J. LaChance, and R. Casey Sadler, “Elevated Blood Lead Levels in Children Associated With the Flint Drinking Water Crisis: A Spatial Analysis of Risk and Public Health Response,” American Journal of Public Health, 21-Dec-2015. [Online]. Available: https://pubmed.ncbi.nlm.nih.gov/26691115/.

[9] M. Kennedy, “Lead-Laced Water In Flint: A Step-By-Step Look At The Makings Of A Crisis,” NPR, 20-Apr-2016. [Online]. Available: https://www.npr.org/sections/thetwo-way/2016/04/20/465545378/lead-laced-water-in-flint-a-step-by-step-look-at-the-makings-of-a-crisis.

[10] M. Torrice, “How Lead Ended Up In Flint's Tap Water,” Chemical & Engineering News, 16-Aug-2020. [Online]. Available: https://cen.acs.org/articles/94/i7/Lead-Ended-Flints-Tap-Water.html.

[11] P. Z. Ruckart, A. S. Ettinger, M. Hanna-Attisha, N. Jones, S. I. Davis, and P. N. Breysse, “The Flint Water Crisis: A Coordinated Public Health Emergency Response and Recovery Initiative,” Journal of public health management and practice : JPHMP, 2019. [Online]. Available: https://www.ncbi.nlm.nih.gov/pmc/articles/PMC6309965/.

[12] R. Hersher, “Lethal Pneumonia Outbreak Caused By Low Chlorine In Flint Water,” NPR, 05-Feb-2018. [Online]. Available: https://www.npr.org/sections/health-shots/2018/02/05/582482024/lethal-pneumonia-outbreak-caused-by-low-chlorine-in-flint-water.

[13] T. Carmody, “How the Flint River got so toxic,” The Verge, 26-Feb-2016. [Online]. Available: https://www.theverge.com/2016/2/26/11117022/flint-michigan-water-crisis-lead-pollution-history.

[14] “Trihalomethanes: Health Information Summary,” 2006. [Online]. Available: https://www.des.nh.gov/organization/commissioner/pip/factsheets/ard/documents/ard-ehp-13.pdf.

[15] “U.S. Census Bureau QuickFacts: Flint city, Michigan,” Census Bureau QuickFacts. [Online]. Available: https://www.census.gov/quickfacts/fact/table/flintcitymichigan/PST040219.

[16] “What is Chlorination?,” Safe Drinking Water Foundation, 27-Nov-2016. [Online]. Available: https://www.safewater.org/fact-sheets-1/2017/1/23/what-is-chlorination.