The oil contains phenanthrene, a polycyclic aromatic hydrocarbon (PAH). Most scientists had linked PAHs to cancer, but a team from Stanford University has discovered that they also damage the human heart. The PAH causes irregular heartbeat and weaker contractions of heart cells.
It's been discovered in bluefin and yellowfin tuna and mackerel they tested, which came from crude oil spills. Phenanthrene is also found in soil, storm water run-offs, derelict industrial sites and in the air.
It's an unrecognised threat to global health, say the researchers, brought about by the widespread use of petroleum.