Flint Water Crisis

Author

Derek Sollberger

Published

January 24, 2026

Tidy Tuesday

The TidyTuesday data set for November 4, 2025, was about the Flint water crisis. I want to summarize some of the findings for my data science course.

library("tidyverse")

# load data (as shown)
flint_mdeq <- readr::read_csv('https://raw.githubusercontent.com/rfordatascience/tidytuesday/main/data/2025/2025-11-04/flint_mdeq.csv')
flint_vt <- readr::read_csv('https://raw.githubusercontent.com/rfordatascience/tidytuesday/main/data/2025/2025-11-04/flint_vt.csv')

Summary statistics

All MDEQ Samples

summary(flint_mdeq$lead)
   Min. 1st Qu.  Median    Mean 3rd Qu.    Max. 
   0.00    2.00    3.00    7.31    6.50  104.00

Outliers Removed

summary(flint_mdeq$lead2)
   Min. 1st Qu.  Median    Mean 3rd Qu.    Max.    NA's 
  0.000   2.000   3.000   5.725   6.000  42.000       2

Independent Test

summary(flint_vt$lead)
   Min. 1st Qu.  Median    Mean 3rd Qu.    Max. 
  0.344   1.578   3.521  10.646   9.050 158.000 
mu1_mdeq <- mean(flint_mdeq$lead, na.rm = TRUE)
mu2_mdeq <- mean(flint_mdeq$lead2, na.rm = TRUE)
mu_vt <- mean(flint_vt$lead, na.rm = TRUE)

top10_1_mdeq <- quantile(flint_mdeq$lead, 0.90, na.rm = TRUE)
top10_2_mdeq <- quantile(flint_mdeq$lead2, 0.90, na.rm = TRUE)
top10_vt <- quantile(flint_vt$lead, 0.90, na.rm = TRUE)

Histograms

All MDEQ Samples


flint_mdeq |>
  ggplot() +
  geom_histogram(aes(x = lead),
                 binwidth = 5, color = "black", fill = "gray75") +
  geom_vline(xintercept = mu1_mdeq, color = "blue", 
             linetype = 2, linewidth = 2) +
  geom_vline(xintercept = top10_1_mdeq, color = "red", 
             linetype = 2, linewidth = 2) +
  labs(title = "Flint Water Samples in 2015",
       subtitle = "MDEQ measurements (average in blue, top 10 percentile in red)",
       caption = "Source: Jen Richmond",
       x = "lead (ppb)", y = "number of samples") +
  theme_minimal()

Outliers Removed

flint_mdeq |>
  ggplot() +
  geom_histogram(aes(x = lead2),
                 binwidth = 5, color = "black", fill = "gray75") +
  geom_vline(xintercept = mu1_mdeq, color = "blue", 
             linetype = 2, linewidth = 2) +
  geom_vline(xintercept = top10_2_mdeq, color = "red", 
             linetype = 2, linewidth = 2) +
  labs(title = "Flint Water Samples in 2015",
       subtitle = "MDEQ measurements, two samples missing (average in blue, top 10 percentile in red)",
       caption = "Source: Jen Richmond",
       x = "lead (ppb)", y = "number of samples") +
  theme_minimal()
Warning: Removed 2 rows containing non-finite outside the scale range
(`stat_bin()`).

Independent Test

flint_vt |>
  ggplot() +
  geom_histogram(aes(x = lead),
                 binwidth = 5, color = "black", fill = "gray75") +
  geom_vline(xintercept = mu1_mdeq, color = "blue", 
             linetype = 2, linewidth = 2) +
  geom_vline(xintercept = top10_vt, color = "red", 
             linetype = 2, linewidth = 2) +
  labs(title = "Flint Water Samples in 2015",
       subtitle = "VT measurements (average in blue, top 10 percentile in red)",
       caption = "Source: Jen Richmond",
       x = "lead (ppb)", y = "number of samples") +
  theme_minimal()

Diagnoses

“the Lead and Copper Rule (LCR) of 1991 is 15 parts per billion (ppb). If this is exceeded in more than 10% of homes tested (or if the 90th percentile value of the total sample is above 15 ppb), action is required.” — Significance, Vol 14, Issue 2

All MDEQ Samples

ifelse(quantile(flint_mdeq$lead, 0.90, na.rm = TRUE) > 15,
       "action required", "safe water")
              90% 
"action required"

Outliers Removed

ifelse(quantile(flint_mdeq$lead2, 0.90, na.rm = TRUE) > 15,
       "action required", "safe water")
         90% 
"safe water"

Independent Test

ifelse(quantile(flint_vt$lead, 0.90, na.rm = TRUE) > 15,
       "action required", "safe water")
              90% 
"action required"

Coda

sessionInfo()
R version 4.5.2 (2025-10-31 ucrt)
Platform: x86_64-w64-mingw32/x64
Running under: Windows 10 x64 (build 19045)

Matrix products: default
  LAPACK version 3.12.1

locale:
[1] LC_COLLATE=English_United States.utf8 
[2] LC_CTYPE=English_United States.utf8   
[3] LC_MONETARY=English_United States.utf8
[4] LC_NUMERIC=C                          
[5] LC_TIME=English_United States.utf8    

time zone: America/New_York
tzcode source: internal

attached base packages:
[1] stats     graphics  grDevices utils     datasets  methods   base     

other attached packages:
 [1] lubridate_1.9.4 forcats_1.0.0   stringr_1.5.1   dplyr_1.1.4    
 [5] purrr_1.1.0     readr_2.1.5     tidyr_1.3.1     tibble_3.3.0   
 [9] ggplot2_4.0.0   tidyverse_2.0.0

loaded via a namespace (and not attached):
 [1] bit_4.6.0          gtable_0.3.6       jsonlite_2.0.0     crayon_1.5.3      
 [5] compiler_4.5.2     tidyselect_1.2.1   parallel_4.5.2     scales_1.4.0      
 [9] yaml_2.3.10        fastmap_1.2.0      R6_2.6.1           labeling_0.4.3    
[13] generics_0.1.4     curl_6.4.0         knitr_1.50         htmlwidgets_1.6.4 
[17] pillar_1.11.0      RColorBrewer_1.1-3 tzdb_0.5.0         rlang_1.1.6       
[21] stringi_1.8.7      xfun_0.52          S7_0.2.0           bit64_4.6.0-1     
[25] timechange_0.3.0   cli_3.6.5          withr_3.0.2        magrittr_2.0.3    
[29] digest_0.6.37      grid_4.5.2         vroom_1.6.5        rstudioapi_0.17.1 
[33] hms_1.1.3          lifecycle_1.0.4    vctrs_0.6.5        evaluate_1.0.4    
[37] glue_1.8.0         farver_2.1.2       rmarkdown_2.29     tools_4.5.2       
[41] pkgconfig_2.0.3    htmltools_0.5.8.1