"Anchorage, Alaska -- Two decades ago, Roy Dalthorp helped clean up the rocky shores of Prince William Sound after the tanker Exxon Valdez ran aground, producing what was then the largest oil spill in U.S. history.

Today, with that record surpassed by the 11-week-old disaster in the Gulf of Mexico, Dalthorp struggles to breathe. He coughs, and his failing eyes sometimes tear up uncontrollably.

Dalthorp told CNN that he was 'slowly poisoned' during the Alaska cleanup effort -- and he says some of those now working to clean up the BP spill off Louisiana and neighboring states are risking the same fate."

Drew Griffin reports for the CNN Special Investigations Unit July 8, 2010. [2]