This two-part series focused on a product called Zonolite. For decades it was used as an attic insulation in millions of homes across the United States. Internal documents from the company that mines the raw material, and government agencies found that the product contains tremolite asbestos, one of the most deadly forms of asbestos. It is related to numerous deaths and illness of the lungs from inhalation of the dust particles of the product. More than 70,000 homes statewide in Michigan (including Detroit) have the product in their attics. Many former employees of the company are at risk of lung ailments without their knowledge of the product's hazard. The series discovered that the EPA was trying to internally assess exactly what to tell the public who may come in contact with the product about how to handle Zonolite. It also included information about how to check the attic of a home to see if there is Zonolite, as well as precautions to be taken.