Not long after certain groups decided to panic residents of the Gulf Coast about Corexit, a mixture of chemicals used to disperse oil from the Deepwater Horizon/Macondo disaster, worried residents of City of Orange Beach, AL started collecting dirty water from local waterways and a nearby lab quickly confirmed that Corexit had indeed washed up on their shores. Since Corexit is composed of common chemicals it was never clear how the lab decided it had detected the original formulation and the lab owner refused to shed any light on the matter. Nevertheless, people were outraged, press conferences were held and all manner of maladies and misfortunes among the locals were blamed on Corexit.
Fast forward two years.
Researchers at Auburn University examined the data on the water samples that had been collected and then decided to test the hypothesis that the chemicals detected had come from Corexit (rather than some other more mundane source). So they sampled rainwater runoff to see if the same chemicals were in the water that City of Orange Beach was itself discharging into inland and nearshore waters. Sure enough they were; and at the same levels found in the samples collected by locals. The conclusion? "Our assessment indicates that these compounds are unlikely to be present as a result of the use of Corexit dispersants; rather, they are likely related to point and non-point source storm water discharge." Read all about it in "Provenance of Corexit-related chemical constituents found in nearshore and inland Gulf Coast waters".