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Lead Level Analysis for the Drinking Water in Flint
Barbara Kaufmann
Yifang Wang
ChemE 335
3/14/2016
Executive Summary
Since April 2014, the city of Flint in Michigan changed its water source from Lake Huron to
murky waters that ran through Flint. Residents in Flint were experiencing a water crisis because
of the bad quality of the water. What was worse, thousands of children in Flint had been exposed
to drinking water with high levels of lead and they were likely to experience a range of serious
health concerns. The state’s Department of Environmental Quality should be responsible for this
because they did not collect sufficient data from the right place of the murky water and ignored
the warning sign visible in what they did collect. Therefore, our project aims to analyze the data
for lead levels in the water and in the resident's blood with the honesty and rigor the issue
deserves. More systematic studies of water samples and pediatric records of blood tests were
performed in 2015. Using techniques from the correlation and hypothesis testing portions of the
course will quantify the differences in water and blood levels between the time when Lake
Huron supplied Flint and the time since the switch to the Flint river supply was made. It can then
be concluded from the more recent data whether the change in supply coincided with a
statistically significant change in lead levels. The deliverable will include a regression analysis of
lead levels versus time and a determination of whether and how far the lead levels post-switch
are outside the confidence intervals of pre-switch levels.

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Introduction
On April 16, 2013, an agreement to construct a new water pipeline that will deliver water from
Lake Huron was made by the governor, however, there will be three more years before this
pipeline is available. In order to save money, the governor agreed to stop buying water from
Detroit and started to use water from the Flint River as a temporal drinking water supplier on
April 25th, 2014. After the flint river was treated as the water source, complaints about the
quality of water start coming in on May, 2014. Also, large number of residents in flint, especially
children were diagnosed that the lead level in their blood exceeded the normal value, which
would cause a series of health problems. And the state’s Department of Environmental Quality
should be responsible for this because they did not collect sufficient samples from the right place
of flint river to do the water analysis before they made a decision to use the flint water as a water
source. Therefore, our project aims to analyze the lead level in the flint water by collecting
samples from the different parts of the flint river as well as the lead level in the blood to figure
out the lead level was within the acceptable range or not. And we used statistical method such as
correlation, hypothesis testing, etc to analyze collected samples, which was expected to provide
an accurate result of the lead level in flint river.
Analysis
B. Lead analysis for samples collectedfrom the flint water in 2015
After Flint water was treated as the water supplier in April, 2015, there was 672 samples
collected from different location in flint. We analyzed the data using histogram and generated a
bar graph, shown as figure 1. For this sample, we found that the mean for the lead concentration
was 10 ppb, and the standard deviation was 99.2 ppb. And the upper control limit was 15 ppb,
which means that if the lead concentration was below this limit, the water in flint water was safe

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enough to be treated as water supplier. So we used null hypothesis to see whether the population
mean of the lead concentration was under 15 ppb or not. In Addition, we used 95% confidence
interval to figure out the range of population mean. And all the performance were shown below:
X = 10 ppb S = 99.2ppb n= 672 α=0.05
Assumed : large sample with unknown ර, normal distribution
Z(α/2)=Z(0.025)=1.96
Z(α/2)* S/ √n=1.96*99.2/√672=7.5ppb
So the 95% confidence interval was (2.5ppb, 17.5ppb).
Null hypothesis: the population mean was 15 ppb.
Alternative hypothesis : the population mean was less than 15 ppb.
Z[( X - μo)/(S/ √n)]= -1.31
Z(α/2)=Z(0.025)=1.96
So Z < Z(α/2), which means we can not reject the null hypothesis, the mean of lead
concentration in flint River was 15 ppb.
B. Using ANOVA analysis to see whetherthe lead concentrationaffectedby
locations in Flint
We collected 4 samples with different sample size from different area in flint. Then analyzed the
data using one-way ANOVA with 0.05 significance to figure out how spread of lead level in
flint. The samples collected from different area with zip codes 48502, 48503, 48504, 48505. And
we used Excel build in function ANOVA TO do the analysis. The result was shown below:

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Anova:'Single'Factor
SUMMARY
Groups Count Sum Average Variance
Column'1 117 547 4.67521368 186.255673
Column'2 294 2270 7.72108844 951.068701
Column'3 351 7244 20.6381766 56900.9744
Column'4 351 1330 3.78917379 166.406854
ANOVA
Source4of4Variation SS df MS F P:value F4crit
Between'Groups58045.5605 3 19348.5202 1.05838341 0.36585268 2.61292776
Within'Groups20273852.2 1109 18281.2013
Total 20331897.8 1112
Table 1: ANOVA testresult by using Excel
From the ANOVA chart: F = 1.058, which was less than F(0.05), so we can not reject the null
hypothesis, that means the lead concentration of Flint River can affect every area in flint.
C. Lead level in blood analysis
We focused on the lead level in the blood for children under six years old. The safe lead
concentration in blood for children is less than 5 mcg/dl. The data we found were shown below:
year lead'level'greater'than'5'mcg/dl(%)
2010 6.3
2011 5.8
2012 4.1
2013 3.9
2014 3.3
2015 5
the mean for this sample was 4.73 mcg/dl, the standard deviation was 1.1 7mcg/dl
small sample size, we assumed it followed normal distribution. The degree of freedom was 5.
Under 95% confidence, t (0.025)= 2.015. Therefore, the confidence interval was
(3.76mcg/dl ,5.69mcg/dl).
Null hypothesis: the lead level in blood was 5mcg/dl

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Alternative hypothesis: the lead level in blood was less than 5 mcg/dl
to = (4.73-5)/(1.17/𝑠𝑞𝑢𝑎𝑟𝑒 𝑟𝑜𝑜𝑡(6)=-0.56mcg/dl, which was less than t(0.025).
Therefore, we can not reject the null hypothesis. That is, the lead level in blood for children
under 6 in flint was 5 mcg/dl.
Results
Table 2: Summary of lead level distribution
Figure 1: The lead level in Flint River distribution
Figure 2: The percentage for lead level greater than 5 mcg/dl in blood for children under
six

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0
1
2
3
4
5
6
7
2009 2010 2011 2012 2013 2014 2015 2016
Lead.level.(mcg/dl)
year
Lead.Level.in.Blood.VS.Years
Figure 1 showed the lead level distribution for samples collected from Flint River in 2015. The
lead level in most samples were below 5ppb, which was good because the lead level below 5ppb
was acceptable. However, if the lead level was above 15 ppb, this should attract people’s
attention because this would a potential threat for human health. And during the samples we
analysis, there was about 6% samples had lead level above 15 ppb. For some samples, the lead
level was even above 150 ppb, which was very dangerous. We used 95% confidence interval to
estimate the range of the average lead level in flint water, and the result was between 2.5 ppb and
17.5 ppb. then we used hypothesis testing to see whether the lead level in flint was below 15 ppb.
And the result was that we can not reject the null hypothesis. So we we were not sure that the
lead level in flint river was under control limit. Then we used ANOVA one way test to check
whether the lead level in flint river only affect some specific area. By comparing the F value we
calculated to the F value with 0.05 significance, we got that everywhere in flint can be affected
by the lead level in Flint River, which means that everyone in flint can be affected if the quality
of flint water was too bad to drink. In addition, we analyzed the lead level in blood of children
who were under six years old in flint in different years. As figure 2 shown, before 2012, large
percentage of children has lead level in blood higher than 5 mcg/dl. This might be the reason
why new pipeline was need to deliver water from Lake Huron. Between 2012 to 2013, there was
a drop for the percentage of lead level higher than 5 mcg/dl because the water supplier bought

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water from Detroit. However, once the flint river was treated as water supplier, the lead level in
children’s blood started to increase after 2014. We also used hypothesis to test the the average
lead level in children’s blood and we can not reject the null hypothesis. So the lead level in
children’s blood was 5 mcg/dl in flint.
Discussion
During our analysis, we found that there were large percentage sample collected from flint river
had lead level below 5 ppb. And this matched the analysis from the state’s Department of
Environmental Quality. And we concluded that those samples might be collected from the wrong
spots of flint River. And there were some samples were detected to have high lead level. So we
should focus on those sample and check where those samples were collected. Then we should
collected samples from those areas and analyzed those data again.
As for the ANOVA test, the samples were collected from four different zip codes and we found
that there was no relation between location and lead level. This might not fully correct. Instead,
we can collect sample in residents’ houses depending on the number of complaints of the
residents. Since the distance of the pipeline to different homes were different. By analyzing those
data, we could get an idea which part of the pipeline was the main reason causing the lead in the
flint water.
Summary
By analyzing the data collected from the flint River and the lead level in blood, we used
knowledge we learned in class, such as hypothesis testing, ANOVA test to check whether the
lead level in flint water was above 15 ppb. The result we found that the flint river has average 15
ppb lead level. Even though this was not out of our control limit, we did have samples had lead
level higher than 15 ppb, some of them can reach to 50 ppb, which means in some area of the
Flint River has high concentration of lead and this was dangerous to residence who were living
in those area. By using Anova test, we found that everyone in flint, no matter how far you live
away from the flint river, they can still be affected by the quality of flint water. When we
measure the lead level in blood, the percentage of children who had lead level in their blood

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higher than 5 mcg/dl started to increase when the water supplier switched to flint river, which
means the quality of flint would be a cause for this rise. The safety lead level in children was
below 5 mcg/dl, but we use hypothesis testing to find that the lead level in blood was not below 5
mcg / dl, which was a threat to children health and might cause a series of health problems to the
children who live in flint. Therefore, the quality of flint was not acceptable so that they can not
be treated as water supplier. And the state’s Department of Environmental Quality should think
highly of this and stop using flint river as drinking water.
Reference
Flint Blood Testing
Report."Http://www.michigan.gov/documents/flintwater/Flint_Blood_Testing_Report_26
Feb16_515770_7.pdf. 26 Feb. 2016. Web.
"Taking Action On Flint Water." Http://www.michigan.gov/flintwater. Web.
"Mediline Plus." Https://www.nlm.nih.gov/medlineplus/ency/article/003360.htm. Web.