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What’s Really
Going On?
When Flint’s water started smelling foul, tasting odd,
turning orange, and the children drinking it started to
develop nasty skin rashes, there was clearly something
terribly wrong. But what? That was a mystery that only
chemistry could solve.
By Adrian Dingle
AP IMAGES; WWW.JIMWESTPHOTO.COM; THINKSTOCK; © REGINA H. BOONE/DETROIT FREE PRESS/ZUMA PRESS; VIDEO LINK HTTPS://WWW.YOUTUBE.COM/WATCH?V=K18VBGWPXZ4

I
N THE SPRING OF 2014, LARGE AMOUNTS were in the process of building a new pipeline few months, they issued a boil-water advisory.
of lead found their way into the water that to bring water from nearby Lake Huron. This Later, in October 2014, the General Motors
some residents of Flint, Mich., were using meant that officials in the city of Flint needed car plant in Flint announced that they would
to drink, cook, and brush their teeth. Lead is to find a short-term solution, while the new no longer use the water, because they feared it
known to be particularly damaging to young pipeline was being built. They decided to use would cause corrosion within the factory.
children’s developing brains. So how did lead water from the local Flint
get into the tap water in Flint? River that they would clean in
water-treatment plants.
Treating and supplying In April 2014, Flint
switched over to the new
water source, and the problems
In early 2013, in order to save money, began almost immediately.
Flint officials decided to change the source Within weeks, residents were
of the city’s water from the Detroit Water complaining of foul-smelling
and Sewerage Department to the Karegnondi and discolored water. The
Water Authority (KWA). However, KWA was city initially denied that there
not ready to deliver the water, because they were any issues, but within a

What, Why and When It Happened

April 2013:
Facing severe April 2014: Flint May 2014: Flint
financial pres- begins using water residents begin to
sures, the city from the Flint river complain about
of Flint, Mich., decides to change the until the KWA pipeline the water.
source of the city’s water and signs from Lake Huron is
a contract with the Karegnondi Water completed.
Authority (KWA), but KWA would not
supply water until 2016. ChemMatters | DECEMBER 2016/JANUARY 2017 5
 A few months later, Flint told its residents tion to those made from copper and iron— times, they found that the 13,000 ppb reading
that their water had high levels of organic to transport water to people’s homes. No one was accurate.
molecules called trihalomethanes. These knows exactly how many lead pipes are used It is important to note that no level of lead
molecules are similar to methane molecules in the United States, but the number is in the in the water supply is considered safe, but the
(CH4), but three of the hydrogen atoms are millions. In addition to the pipes themselves, U.S. Environmental Protection Agency has set
replaced with halogen (group 17) atoms— lead is also found in alloys (mixtures of met- a maximum level of lead contamination in the
fluorine, chlorine, bromine, or iodine. The als) in other parts of the plumbing system. tap water in 90% of homes at 15 ppb—also
four most common trihalomethanes are For example, the solder used to join pipes known as the “action level.” That particular
dibromochloromethane (CHClBr2), dichloro- together is an alloy of tin and lead. sample of Flint water had a lead level close to
bromomethane (CHCl2Br), trichloromethane In Flint, massive levels of lead entered the 1,000 times the action level.
(CHCl3)—better known as chloroform—and water system. In one sample of water taken
tribromomethane (CHBr3). from a Flint home, a lead level of 13,000 parts
Lead-prevention

THE FLINT WATER PROJECT; THINKSTOCK; SHUTTERSTOCK

Trihalomethanes are a concern because
techniques
per billion (ppb) was found. The chemists who
they have been linked with numerous health tested the water were skeptical at first. But
concerns, including liver, kidney, lung, and after repeating the experiment a number of Oxidizing agents in water, such as dissolved
heart conditions. When the chlorine used to oxygen, can react with exposed lead pipes
disinfect water reacts with algae, leaves, and causing soluble Pb2+ ions to enter the sup-
weeds, trihalomethanes are produced. ply. Two chemical reactions are involved: 1)
oxidation, and 2) reduction. Both reactions are
called redox reactions, for short. In the oxida-
tion reaction, lead loses electrons and forms
Pb2+ ions, as follows:

2 Pb (s) ➔ 2 Pb2+(aq) + 4 e–

In the reduction reaction, oxygen gains

electrons, as follows:

4 e– + 2 H2O (l) + O2 (aq) ➔ 4 OH– (aq)

Together, the oxidation and reduc-

tion reactions combine to give the full
redox reaction:

2 Pb (s) + O2 (g) + 2 H2O (l)

➔ 2 Pb(OH)2 (s)
Toxic levels of lead
Trihalomethanes are just one group of
chemicals associated with water contamina-
tion. Lead is another. This metal was a popular Above left, Otto Schwake, a postdoctoral microbiologist at
choice for use as water pipes for centuries. Virginia Tech, tested Flint tap water for waterborne pathogens.
Top, water flowing from a faucet in a hospital in Flint, Mich.
The Romans used the dense metal because Above, pipes from the Flint water distribution system after the
of its durability and malleability. Water pipes city decided to use water from the local Flint River.
are no longer made from lead, but older cities,
such as Flint, still rely on lead pipes—in addi- Right, water samples from Flint
collected by Virginia Tech scientists

August 2014: January 2015: Flint

Water tests positive announces that the water February 2015:
for E. coli contains high levels of tri- Flint resident
bacteria; a halomethanes, in violation LeAnne Walters’s son
boil-water of the Safe Drinking Water develops rashes. High
advisory is issued Act, but city officials tell levels of lead are
in parts of Flint. residents that the water is detected in the water
safe. in her home.

6 ChemMatters | DECEMBER 2016/JANUARY 2017 www.acs.org/chemmatters

 Cities use various methods to prevent may dissolve and fall off. We can explain
lead pipes from leaching lead ions into this by considering Le Châtelier’s principle,
Before: Treated Detroit water
the water supply. One method is to cre- Phosphate corrosion inhibitor helps maintain a mineral
which states that a system that is shifted
ate a protective layer on the inside of the passivation layer on the inside of Flint’s pipes, protecting
them from corrosion. With little corrosion, chlorine
away from equilibrium acts to restore the
pipe. This is done by adding phosphate disinfectant levels remain stable. equilibrium by reacting in opposition to
ions (PO43–) to the water supply. Phos- the shift.
Mineral
phate is also known as orthophosphate. O passivation layer
Cl2 Lead(II) carbonate is relatively insoluble
These negative polyatomic ions help to P
Lead in water, but does dissolve a little, and in
Cl2 Cl– or
create lead(II) phosphate (Pb3(PO4)2), an
–O
O–
O–
Cl2
iron the process sets up this equilibrium:
Cl2 pipe
insoluble, mineral-like crust on the inside Phosphate corrosion
inhibitor
of the pipes. Cl2 Cl2
PbCO3 (s) ⇌ Pb2+ (aq) + CO32– (aq)
The addition of phosphate ions to the
water needs to be an ongoing, continual
After: Treated Flint River water The carbonate ions that are produced
process, and if the crust is maintained Lack of a corrosion inhibitor, high chloride levels, and other
over time, the water comes into less or factors cause the pipe passivation layer to dissolve and fall can then react with hydrogen ions (acid)
off, leading to increased corrosion in Flint’s pipes. As the
no contact with the lead pipe itself and, pipes corrode, chlorine disinfectant breaks down. present in the water supply, according to
as a result, fewer redox reactions take this equation:
Cl–
place and less lead enters the water. If Cl– Cl–
Cl–
the phosphate crust is not maintained, it CO32– (aq) + 2 H+ (aq)
Cl– Cl– Lead
breaks down over time and lead can leach Cl– pipe ➔ H2O (l) + CO2 (g)
Cl–
into the water supply. Cl–
Cl– Pb2+ Pb2+
The water that Flint used to get from O2 O2

nearby Detroit was treated with phos- The lower the pH, the more hydrogen
phate ions in this way and, as a result, Oxidants such as dissolved O2 ions that are present in solution, and
corrode pipes and leach soluble metal.
remained relatively free of lead ions. the more the carbonate ions react. The
When Flint changed its water supply to removal of carbonate ions from the equi-
Cl– O2 O2
⨉2
Cl Fe2+ Fe2+ librium system of lead(II) carbonate in the
THE FLINT WATER PROJECT; CHEMICAL & ENGINEERING NEWS; AP IMAGES

river water, authorities failed to treat it

with phosphate ions, so the phosphate Exposed iron Iron corrosion first equation results in an increase in the
reduces free Cl– leads to Iron
crust broke down over time and lead ions chlorine used as rust-colored pipe concentration of lead ions. To restore the
disinfectant. water.
entered the water. Cl– equilibrium, the chemical reaction shifts
Cl– ⨉2
Cl Cl–
Cl– to the right, so that additional carbonate

Complicating factors ions (and lead ions) are produced.

To ensure that the number of lead and
In addition to the loss of the phosphate carbonate ions is the same on the right
protective layer in the pipes, two other prob- an example of connections between different side of the equation, the reaction then shifts
lems occurred, as well. applications of chemistry: De-icing Michigan’s to the left and to the right a few times until
First, the Flint River water had some unusu- slippery roads has some immediate and obvi- a new equilibrium is reached. In this new
ally high levels of chloride ions, which can ous benefits, but the run-off of chloride ions equilibrium, the number of lead ions is the
accelerate the corrosion of the pipes. In can be an unintended consequence. same as the number of carbonate ions, but
part, these high chloride Second, the pH of the water from the the number of lead ions is larger than what
levels came from salts Flint water treatment plants was too low. By it was during the original equilibrium (before
used to treat roads dur- maintaining a relatively high pH (around 10), the carbonate ions were removed), resulting
ing the cold and snowy the solubility of another lead compound that in more lead ions at equilibrium than before.
Michigan winters. Often, contributes to the protective layer, lead(II) Flint’s water was found to have pH values
chlorides enter rivers carbonate (PbCO3), decreases. This helps to between 7 and 8, which is not basic enough to
as run-off from the maintain the protective layer on the pipes. If prevent lead carbonate from dissolving.
roads. This is actually the pH is too low, then the protective layer

October 2015:
Flint switches back January 2016: Michigan Gov.
to using water from Rick Snyder declares a state of
September 2015: Detroit. emergency in Flint. Then, President
Data show that Barack Obama signs an emer-
many children have gency declaration and orders fed-
elevated lead levels eral aid for Flint.
in their blood.

ChemMatters | DECEMBER 2016/JANUARY 2017 7

 The lack of a protective layer in the iron but the concerns are real and troubling for
pipes can cause a similar oxidation reac- all of the families affected.
tion to the one occurring in the lead pipes: In addition to the long-term health
concerns, a number of lawsuits have been
filed against Flint and Michigan officials,
Fe (s) ➔ Fe2+ (aq) + 2 e–
and millions of dollars will be required to
address the crisis and rebuild the water-
The aqueous iron ions can cause the pipe system. In January 2016, the U.S.
water to turn an unsightly rust color, but
it can also have another troublesome side
T he Flint water crisis may be the
most serious lead contamination in
drinking water to date, but other water sup-
government pledged $80 million in aid to
the state of Michigan, most of which is
effect. This time, elemental chlorine (Cl2) to be used to repair the infrastructure of
plies across the United States have been
can be reduced to chloride ions (Cl–). Flint’s water-supply system. In February
affected, too. In 2001, Washington, D.C.,
When the electrons are given up by the of the same year, the U.S. Department of
changed how it treated drinking water,
iron and picked up by the chlorine mol- Health and Human Services announced
and lead levels rose dramatically. In 2006,
ecules, the following reduction reaction that $500,000 would be made available to
unsafe levels of lead were found in Durham
occurs: two Flint-area health centers to help fight
and Greenville, N.C. In the summer of
the problems caused by the tainted water.
2015, officials discovered significant lead
2 e– + Cl2 (aq) ➔ 2 Cl– (aq) Through knowledge of chemistry,
contamination in the drinking water in Jack-
including the formation of precipitates, the
son, Miss., but waited six months before
pH scale, and redox chemistry, scientists
The loss of elemental chlorine is a informing residents. The list goes on.
were able to solve the Flint water mystery.
potentially huge problem for public health. The U.S. Congress banned the use of
The crisis was stopped before it became
Chlorine is added to the water supply lead water pipes 30 years ago, but the rule
worse, and Flint’s water supply was made
to eliminate waterborne pathogens. The applies only to new water pipes. Millions
safer—all thanks to chemistry.
removal of elemental chlorine via reduc- of older ones remain in use. One possible
tion can mean that waterborne pathogens solution is to dig up and replace these lead
have a better chance of surviving, causing pipes, as has occurred between 2001 and SELECTED REFERENCES
2011 in Madison, Wis. But doing so is How Lead Ended Up in Flint’s Tap Water. Chem.

ADOBE STOCK; SHUTTERSTOCK; AP IMAGES; STUDENT PHOTO BY DEB JACQUES, COURTESY OF C & G PUBLISHING
disease.
costly, and not all cities have the financial Eng. News, 94 (7), Feb 11, 2016, pp 26–29.
Haines, G. K. Is this Water Recycled Sewage?
How is Flint’s water now? means to do it. Other solutions include
adding more or different chemicals to the
ChemMatters, Feb 2011, pp 8–10.
Walters, L. A. Flint Water Study Updates.
In October 2015, Flint switched back source water and to continuously test for Virginia Polytechnic Institute and State
to the Detroit system as the source of its contaminants. The problem is not easy to University: http://flintwaterstudy.org/
[accessed Sept 2016].
water. But this incident will still have some solve, but at least the Flint water crisis has
Dennis, B. Water in Flint Is Improving but
far-reaching consequences. raised awareness of the issue, and it may Still Unsafe to Drink, Researchers Say. The
At the top of the list are the potential lead to safer drinking water throughout Washington Post, April 12, 2016: http://
ongoing health problems for an estimated the United States in the future. tinyurl.com/zdn3o2a [accessed Sept 2016].
6,000 to 12,000 children. Nobody can —Adrian Dingle Adrian Dingle is a science writer who lives
predict what those problems may be, but in Atlanta, Ga. This is his first article in
high levels of lead exposure have been ChemMatters.
linked to developmental and behavioral
problems in children and issues related to
brain function. It will likely be a long time
before all of the problems come to light,

January 2016:
Volunteers from around the
country, including students March 2016: The Flint
from Harper Woods High water task force, appointed
School, Harper Woods, by Governor Snyder, finds
Mich. (also pictured that state agencies within
on the cover), donate Michigan are mainly
water and supplies to responsible for the crisis.
Flint residents.

8 ChemMatters | DECEMBER 2016/JANUARY 2017 www.acs.org/chemmatters