Key findings from our investigation into the people who got sick after cleaning up BP’s oil spill

Thousands of people have sued BP for long-term health conditions they claim stem from the dirty work of cleaning up BP's Deepwater Horizon oil spill 13 years ago. The explosion marked the biggest industrial disaster in US history, which saw thousands of Gulf coast residents, many from poor fishing communities, take part in the clean-up effort.

The Guardian spoke with two dozen former workers, used computer programming to analyze a random sample of cases and combed through legal filings to understand the scope of the public health disaster.

BP declined to comment on detailed questions, citing ongoing litigation.

Here are some key findings:

Among those who are sick there is a shared feeling of exasperation and anger as the chances of receiving damages and acknowledgement via the courts rapidly dwindles. They boated out into the Gulf to try to block the oil from coming ashore with floating barriers, called booms. They worked 12-hour shifts in the middle of the summer to save the wetlands and say they got sick as a result.

The Guardian used computer programming to analyze a random sample of 400 lawsuits out of the nearly 5,000 filed against BP. Many of the people in our sample have more than one ailment. Sinus issues are the most common chronic health problem listed among those who have sued, followed by eye, skin and respiratory ailments. Chronic rhinosinusitis, a swelling of the sinuses in the nose and head that causes nasal drip and pain in the face, was the most common condition. Two per cent have been diagnosed with cancer, a number some experts believe will continue to rise.

Federal agencies encouraged BP to take urine, blood or skin swab samples of cleanup workers to detect whether toxins had entered their bloodstream. Instead, the fossil fuel firm depended on air monitoring to determine if workers were safe. Internal emails, gleaned from discovery in the lawsuits and reported on for the first time by the Guardian, show that was not BP's only goal.