Gas ovens are not necessarily going to cause asthma. You can mitigate the amount of air pollution that they produce but having a gas oven doesn't necessarily mean a child will develop asthma or that they will even be the cause. Florida has a very small amount of gas stoves and yet have a median share of asthmatic children. There's too many other factors that can effect the data link to say for sure that gas ovens are a leading cause.