Well I believe that MJ is alive, therefore, in my opinion, it isn't his autopsy. But in the worst of cases, if that is his autopsy ...Have you not thought of fog or smoke machines? Take a look at this...
Theatrical Fog and Artificial Mists
A number of studies have been published on the potential health effects presented by exposure to theatrical fogs and artificial mists.
The first study that was completed was done by Consultech Engineering, Co. under contract to Actor's Equity. The findings of the Consultech study were confirmed by two additional studies -- a Health Hazard Evaluation completed in 1994 by the National Institute for Occupational Safety and Health, and another one in 2000 by the Department of Community and Preventative Medicine at the Mount Sinai School of Medicine and ENVIRON ; both prepared for Actors Equity and the League of American Theatres and Producers, focused on the effects on actors and performers in Broadway musicals. The conclusion of all three studies was that there was irritation of mucous membranes such as the eyes and the respiratory tract associated with extended peak exposure to theatrical fog.
Another study focused on the use of theatrical fog in the commercial aviation industry for emergency training of staff in stimulated fire conditions. This study also found eye and respiratory tract irritation.
In May 2005, a study published in the American Journal of Industrial Medicine, conducted by the School of Environment and Health at the University of British Columbia, looked at adverse respiratory effects in crew members on a wide variety of entertainment venues ranging from live theatres, concerts, television and film productions to a video arcade. This study determined that cumulative exposure to mineral oil and glycol-based fogs were associated with acute and chronic adverse effects on respiratory health. This study found that short-term exposure to glycol fog was associated with coughing, dry throat, headaches, dizziness, drowsiness, and tiredness. This study also found long-term exposure to smoke and fog was associated with both short-term and long-term respiratory problems such as chest tightness and wheezing. Personnel working closest to the fog machines had reduced lung function results.
The Entertainment Services and Technology Association (ESTA) has compiled a standard for theatrical fogs or artificial mists compositions for use in entertainment venues that "are not likely to be harmful to otherwise healthy performers, technicians, or audience members of normal working age, which is 18 to 64 years of age, inclusive." This standard was based primarily (though not exclusively), upon the findings of a report commissioned for ESTA by the Cohen Group and applies only those fog fluid compositions that consist of a mixture of water and glycol (so called "water based" fog fluid).
Short term exposure to glycol fog can be associated with headaches, dizziness, drowsiness and tiredness. Long term exposure to smoke and fog can be related to upper airway and voice symptoms. Extended (multi-year) exposure to smoke and fog has been associated with both short-term and long-term respiratory health problems. Efforts should be made to reduce exposure to theatrical smoke to as low a level as possible. The use of digital effects in post production on film and television sets can be considered a safer practice than using theatrical smoke and fog during filming, although this is not always practical.
http://en.wikipedia.org/wiki/Theatrical_smoke_and_fog
And I agree with the poster above, bronchiolitis is very common, and can be acquired by aspiration of food particles or liquids into the lungs.