Marc Wilkenfeld, M.D., is a Board Certified Occupational/Environmental physician in New York City. He is an assistant professor in Clinical medicine and Environmental Sciences at Columbia University Medical Center where he also acts as Occupational Medicine Consultant to the Department of Environmental Health and Safety. He has lectured and trained Internal Medicine and Family Practice Physicians on aspects of Occupational/Environmental Medicine. Dr. Wilkenfeld is a physician specialist at the Gouverneur Health Care Services- WTC Environmental Health Center evaluating and treating patients with medical and mental health problems as a result of the collapse of the World Trade Center on 9/11. Dr. Wilkenfeld has acted as Occupational Medicine consultant to corporations, government agencies and other organizations in the United States and Europe. He is past-president of the New York Occupational Medicine Association. He has lectured extensively in the field of Occupational and Environmental Medicine. Following the attacks on 9/11 Dr. Wilkenfeld acted as a consultant to a number of government agencies, corporations and community groups on the environmental health impact of the disaster. In this role he reviewed pre- and post-cleaning data and answered questions regarding potential health effects of contamination with WTC dust. He moderated and participated in community forums designed to answer the health questions of residents and workers. He has also evaluated cases of illness related to the 9/11 disaster.