Anxiety surrounding the chemical dispersant used to battle the BP oil spill is rising, thanks in part to seven cleanup crew members who were admitted to a hospital with complaints of nausea, shortness of breath and high blood pressure. Doctors say the symptoms are related to some kind of irritant, as well as dehydration, according to the story in The New York Times.

Coast Guard officials say the boats the men were working on were 50 miles from any spraying of chemicals, and the crew had been wearing protective gear. A spokeswoman from the Louisiana Department of Health and Hospitals said no other ailments linked to the dispersant had been reported in the region.

Only a week ago, the E.P.A. asked BP to stop using the chemical dispersant known as Corexit because of its high level of toxicity. BP did not switch brands but turned to using less of the chemical agent. BP says it is now using less than 15,000 gallons of Corexit, down from 70,000 a day.

Little is known about Corexit’s long-term effects, and Nalco, the company that makes the product, has refused to release its formula.

Epidemiologists in Louisiana are investigating the cases.

Meanwhile, BP struggled with plugging the flow of oil again today, suspending the latest effort as President Obama visited the region.

Related: Gulf Oil Spill: Effort to Seal Leak May Be Delayed, Disputes Over Dispersant