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The terrorist attack on 9/11/2001, and subsequent rescue, recovery, and service restoration of the World Trade Centre disaster site in New York City, created an unprecedented and unique occupational and environmental exposure that affected a large and diverse group of rescue workers and volunteers. The workers were exposed to a mixture of poorly characterised inhaled toxicants. A variety of acute and chronic respiratory illnesses have been reported among all exposed workers, which are the subject of large scale ongoing investigation and follow up. Our group created the WTC Chest Imaging Archive as a repository for more than 3500 chest CT scan studies in about 1700 WTC workers. We systematically assessed imaging abnormalities by means of the International CT Classification of Occupational and Environmental Respiratory Diseases. An examination of the first available chest CT scan for each subject (n=1453) with complete available data, a median of 6.8 years after September 11, 2001 revealed that the most frequent recorded abnormalities were pleural abnormalities (parietal in 7.9% of the workers, and visceral in 12.8% of them), inhomogeneous attenuation (13.2%), irregular/linear opacities (12.9%), and emphysema (12.0%). With regards to pleural abnormalities, although we found them across all 5 broad occupational groups, they were more frequent among construction labourers/asbestos handlers/building cleaners, most of whom were first-generation immigrants. Many of those abnormalities were not reported by clinical radiological readings. Visceral, but not parietal pleural changes were associated with mild pulmonary function impairment. Future studies will examine the evolution of imaging abnormalities, and add computerised quantitative CT scan to their assessment.