The Michigan city of Flint became a national symbol of environmental disaster when it was revealed that thousands of residents had been exposed to dangerous levels of lead in the city's drinking water. And according to John Oliver, the problem extends well beyond Flint.

Oliver, the host of HBO's "Last Week Tonight," took a closer look Sunday at how state and local officials ignored multiple warning signs that lead had seeped into the water system.

"Flint has become a city whose name is synonymous with disaster," said Oliver. "[The city's water crisis] was a perfect storm of incompetence from start to finish."

The TV host explained that many states across the country face the same problem. Oliver identified the myriad difficulties in preventing lead poisoning, including the fact that the locations of many of the lead pipes in the ground across the country are unknown and that lead paint dust poses an even bigger threat. He added that the government has been slow to act. Congress has shied away from allocating the $230 million per year minimum that would be required to contain the threat of lead poisoning across the country, Oliver said. 

"You would think that our members of Congress would be on board with doing more to fight lead poisoning. After all, you remember how angry they were about all those kids who got poisoned in Flint, right?" Oliver pointed out, after showing a montage of congressmen scolding officials in Flint over the water crisis. "That’s what makes it so frustrating that last year, all of those men voted for a bill that would have reduced the already low funding for HUD-led abatement programs by $35 million — amounting to a 32 percent cut. And the truth is, if you cut funding like that, a whole lot more children might get poisoned."

Watch John Oliver break down the Flint water crisis in the clip from "Last Week Tonight" below:

Oliver ended the segment with some help from "Sesame Street." He reminded his audience that the popular children's show used a song in an episode 20 years ago to teach children to avoid exposure to lead. Oliver figured it was time to update the song and brought out a few favorite "Sesame Street" characters, including Elmo and Oscar the Grouch, for the new musical number.