shelters continue to use asbestos. Cutting these sheets to size and drilling holes to receive 'J' bolts to help secure the sheets to roof framing is done on-site. There has been no significant change in production and use of A/C sheets in developing countries following the widespread restrictions in developed nations. September 11 attacks As New York City's World Trade Center collapsed following the September 11 attacks, Lower Manhattan was blanketed in a mixture of building debris and combustible materials. This complex mixture gave rise to the concern that thousands of residents and workers in the area would be exposed to known hazards in the air and dust, such as asbestos, lead, glass fibers, and pulverized concrete. More than 1,000 tons of asbestos are thought to have been released into the air following the buildings' destruction. Inhalation of a mixture of asbestos and other toxicants is thought to be linked to the unusually high death rate from cancer of emergency service workers since the disaster. Thousands more are now thought to be at risk of developing cancer due to this exposure with those who have died so far being only the "tip of the iceberg". In May 2002, after numerous cleanup, dust collection, and air monitoring activities were conducted outdoors by EPA, other federal agencies, New York City, and the state of New York, New York City formally requested federal assistance to clean and test residences in the vicinity of the World Trade Center site for airborne asbestos. Asbestos contaminants in other products Vermiculite Vermiculite is a hydrated laminar magnesium-aluminum-iron silicate that resembles mica. It can be used for many industrial applications and has been used as insulation. Some deposits of vermiculite are contaminated with small amounts of asbestos. One vermiculite mine operated by W. R. Grace and Company in Libby, Montana exposed workers and community residents to danger by mining vermiculite contaminated with asbestos, typically richterite, winchite, actinolite or tremolite. Vermiculite contaminated with asbestos from the Libby mine was used as insulation in residential and commercial buildings through Canada and the United States. W. R. Grace and Company's loose-fill vermiculite was marketed as Zonolite but was also used in sprayed-on products such as Monokote. In 1999, the EPA began cleanup efforts in Libby and now the area is a Superfund cleanup area. The EPA has determined that harmful asbestos is released from the mine as well as through other