All-female round the world voyage hunts for pollution hotspots

Eight hundred miles from land in the Pacific Ocean, Emily Penn had a revelation. It was the late 2000s and she was working aboard the boat Earthrace as it circumnavigated the globe. Jumping overboard for a wash, she saw a toothbrush floating by. Then a cigarette lighter. Then a bottle top. Then hundreds of plastic fragments came into view. "It just didn't make any sense," she recalls.