Fiberglass is composed of small glass fibers and glass is made from sand, which is a basic component of silica.  Silica has been classified as a human lung carcinogen as well as linked as a leading cause to lung disease; in addition to greatly exasperating other respiratory issues such as asthma and emphysema. According to the American Lung Association, “over time, exposure to silica particles causes scarring in the lungs, which can harm your ability to breathe.”