Closure or narrowing of the pulmonary artery or part of its branches by embolic material, which may include: clots (most often; usually from the deep veins of the lower limbs or pelvis), occasionally amniotic fluid, air (during central venous catheter insertion or removal), fatty tissue (after a long bone fracture), tumor masses (e.g., kidney or stomach cancer), and foreign bodies (e.g., embolization material).