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The chemicals that were used to break up oil from the 2010 BP Deepwater Horizon blowout have long been suspected of sickening workers who responded to the disaster. Now a federal health agency is backing some of their assertions.

The National Institutes of Health this month published a study saying workers exposed to oil dispersants suffered a range of symptoms, including cough, shortness of breath and eye and lung irritation. The authors make for the most prominent group of scientists to examine the human health effects of dispersants.

For 87 days after the Deepwater Horizon drilling platform exploded off the Louisiana coast, the Macondo well spewed oil largely unchecked into the Gulf of Mexico. At 172 million gallons lost, it was the world’s largest oil disaster.

Two dispersants, Corexit EC9500A and Corexit EC9527A, both manufactured by Nalco Environmental Solutions, were dropped by airplane to break up oil on the water’s surface. It was the first time dispersants had been used on a large scale, and their potential effects on human health and the environment were not known. As late as 2013, a BP spokesman told The Times-Picayune that dispersants posed no health or safety concerns.

The National Institutes of Health study follows similar research by university scientists and activist groups in the years after the disaster. In interviews with the Government Accountability Project, a Washington D.C. watchdog group, cleanup workers and coastal residents reported a wide range of symptoms, including memory loss, bloody urine, heart problems and liver damage, according to a 2013 report. A 2015 study by the University of Alabama at Birmingham indicated dispersants could damage human lungs and the gills of fish and other marine life.

National Institutes of Health scientists found that workers exposed to dispersants were more likely to experience certain symptoms — cough, wheeze, chest tightness and burning in the eyes, nose, throat and lungs — than those who were not exposed to dispersants. The researchers were able to isolate the effects of oil exposure, which is also harmful, from those associated with dispersants.

Dale Sandler, a researcher who worked on the study, said the findings apply to only workers involved in the cleanup effort. “The health effects that we see in the workers don’t necessarily apply to the community at large, although many of the workers live in affected areas,” she said.

Most workers who suffered health problems during the cleanup no longer had them three years later, indicating dispersants might cause only short-term harm. A small percentage of workers were still feeling the same symptoms years after the disaster, according the new study. “Some of them are continuing to not feel well, and we don’t know what factors are contributing to it,” National Institutes of Health scientist Linda Birnbaum said.

A BP spokesman on Thursday (Sept. 21) would not comment on the study. In the past, BP has said the use of dispersants was approved by federal environmental agencies and the U.S. Coast Guard.

According to the National Institutes of Health, most research on dispersants has focused on their effectiveness and potential environmental consequences, with little study of their effects on human health. While finding no evidence of serious problems, the new study cited research by other institutions suggesting dispersants might be toxic to animals.

National Institutes of Health researchers interviewed more than 31,000 people involved in the BP disaster  response and cleanup. Participants who indicated symptoms were visited at home, where they underwent medical assessments and provided biological samples for testing.

Tristan Baurick