Studies have, however, shown mixed results regarding these other risk factors. There has been an association shown between the increased use of peripheral stem cells and the risk of developing obliterative bronchiolitis. Also, research has shown an increased risk for developing the disease within the first year of transplant if the person is infected with respiratory syncytial virus or parainfluenza virus within the first 100 days post transplant. There are many industrial inhalants that are known to cause various types of bronchiolitis, including obliterative bronchiolitis. Industrial workers who have presented with bronchiolitis:   Diacetyl is a chemical used to produce the artificial butter flavoring in many foods such as candy and microwave popcorn and occurring naturally in wines. This first came to public attention when eight former employees of the Gilster-Mary Lee popcorn plant in Jasper, Missouri developed obliterative bronchiolitis. Due to this event, obliterative bronchiolitis began to be referred to in the popular media as "popcorn lung" or "popcorn workers lung". It is also referred to as "flavorings-related lung disease". Typically found in young children and is the most common cause at this age. Generally occurs after a viral infection of adenovirus (types 3, 7, and 21), measles (rubeola), mycoplasma, CMV, influenza, and parainfluenza. Swyer-James syndrome is a rare complication of obliterative bronchiolitis caused by measles or adenovirus. Post-infectious obliterative bronchiolitis is most common in the southern hemisphere particularly in countries such as Brazil, Argentina, Australia, Chile and New Zealand. There was a large prevalence of the disease in these areas during the 1990s and early 2000s. In one hospital in Buenos Aires, the Ricardo Gutiérrez Children's hospital, the disease accounted for 14% of their inpatient respiratory population from 1993 to 2002. As such, much of the information about post-infectious obliterative bronchiolitis has come from research out of South America. The most significant risk factors for the disease are infection with adenovirus and the need for ventilator support. In contrast with another cause of obliterative bronchiolitis in children, Steven's Johnson's syndrome, post-infectious obliterative bronchiolitis tends to be a chronic but non-progressive disease. The disease can have varying impact on children and their quality of life, which has been studied by lung function tests, as well as their exercise tolerance.