A 29-year-old man is seen in the chest clinic. A week ago he was seen in the ER with symptoms of headache, fever, and metallic taste in his mouth. He denied any specific respiratory symptoms. It was noted in the ER record that he had a history of substance abuse. His physical exam was normal except for needle tracks in his right arm. At that time, before a complete evaluation was done, he left the ER against medical advice. A CXR done in the ER is retrieved . The patient is currently asymptomatic and came to the clinic because he wanted a general checkup.Based on the chest x-ray, the most likely diagnosis is