The most likely reason is.. (Score 1)

The more likely connection between asthma and hours of presence in front of a TV is, the toxicity and fumes from the TV. Fire retardant chemicals and conformal coatings on the circuit boards and other electronic components are all releasing chemical, toxic fumes into the air, albeit small, especially once a TV gets heated up from being on. In addition, if it is an older CRT tube-type of TV involved, there are fair amounts of ozone produced by the high voltage circuitry. All of these things are chemical outgassings, which are exactly the known triggers for people that already have asthma and other lung ailments.