Videos show 'disgusting' slicks in creek water near Ohio train derailment. What's going on?

Videos appear to show shimmering chemical contamination on creeks near the site of the East Palestine, Ohio, train derailment and chemical leak.

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Experts tell USA TODAY the rainbow-colored material is likely vinyl chloride, a heavier-than-water chemical that both leaked and burned following the Feb. 3 derailment of a Norfolk Southern freight train. The videos mark yet another example of heightened health and environmental concerns in the wake of the disaster.

Authorities say about 3,500 small fish were killed in the creeks surrounding the derailment site shortly after the crash, leak and burn, but they have not reported significant subsequent deaths. Meanwhile, a new federal lawsuit claims fish and wild animals are dying as far as 20 miles away from the site of the derailment.

Here's what to know about the videos:
What do the videos show?

The videos posted by several people, including Ohio Republican Sen. J.D. Vance show rainbow-colored slicks spreading across the surface of small streams in the area after people poked the creek beds with sticks or threw rocks in.

"This is disgusting," Vance declared as sheen spread across what he said was Leslie Run creek.

FACT CHECK:Ohio train derailment fact check: What's true and what's false?

BACKGROUND: Is the Ohio River contaminated? East Palestine train derailment sparks concerns over water
What is going on in the videos?

John Senko, a professor of geosciences and biology at the University of Akron, said the videos depict what appears to be vinyl chloride, which would sink to the bottom of a lake or stream because it's denser than water.

"It looks like what's happening is you got some of that stuff on the bottom of the creek, you stir it up a little bit, it starts to come up and then it's just going to sink again," he said. "So that stuff's behaving like I would expect vinyl chloride to behave.”
What are the health risks of the creek contamination?

The videos are evidence that groundwater contamination has occurred, experts told the USA TODAY Network. But contamination does not necessarily mean there's a health risk.