This residual oil has been found to exhibit toxic effects down to concentrations as low as 1 part per billion. And beyond ecosystem impacts, humans working on the cleanup experienced an average oil-mist exposure some 12 times in excess of permissible exposure limits. A maximum overexposure of 400 times the permissible limit was reported from one beach being treated with high-pressure, hot water washing. Over 1,800 worker compensation claims were received by the government in 1989, most with respiratory complaints. In summary, the biological damage of the Exxon Valdez spill was severe, unprecedented, and in most cases ongoing ten years into the event.
Many scientists expect long-term damage to continue for decades to come.