Passage: While doing graduate work at the South Dakota State University in 1986, Dr. Mardon was invited to be a member of the 1986-87 Antarctic meteorite expedition for NASA and the National Science Foundation. 170 miles from the South Pole station when his team found hundreds of meteorites. During his sojourn he suffered environmental exposure which damaged his lungs and gave him a permanent cough. He received the U.S. Congressional Antarctic Service Medal for his efforts and risk.On his return to Alberta, he gave lectures on Antarctica at the University of Calgary and the University of Lethbridge. He secured an interview to be a member of the Canadian/Soviet Arctic traverse from northern Siberia to Ellesmere Island in the Canadian Arctic, but failed to get on that expedition.He was a part of the failed meteorite recovery expedition in the Canadian Arctic near Resolute in the Northwest Territories, and wrote a paper on his conversations with locals and what the Inuit thought of meteorites. He was also supposed to join an Argentinian Antarctic expedition in the late 80's, but a fire at the Argentinian Antarctic base caused his membership to be canceled.One of his most significant contributions to astronomical science was a series of articles he wrote on the Anglo-Saxon Chronicle. The Chronicle is a running commentary on different events in England during the medieval period. With the assistance of his father, a medieval scholar, Dr. Mardon found eleven cometary events mentioned in the Chronicle that are not mentioned anywhere else in astronomical literature, as well as two meteor showers recorded in the Chronicle.In 1991, Dr. Mardon was invited to join an expedition to the South Pole sponsored by the Geographical Society of the USSR. He traveled to Moscow and met with some expedition officials, receiving a strange welcome with little information and odd accommodations. He soon found out that he was under suspicion by the authorities and was arrested first by the GRU, then by the KGB. Dr. Mardon was questioned, held...

Question: What caused the damage to Dr. Mardon's lungs?
environmental exposure