It certainly is just one study, but it does provide some indication about long term, which is rare.
As for inhalers, it's an interesting point. However, dose reaction amounts are probably different when you compare sleeping in a room every night while exposed continuously to a contaminant, as opposed to occasionally taking a toke from an inhaler. In the second case you have a much higher intake in short bursts, in the first exposure is continuous.
Whether one is more effective than the other in respect to some specific effect really depends on the type of substance and the effect.
Then, it's true that the study focussed on a range of contaminants.
It's also interesting that the study muses about whether repainting one of more rooms in the house over the gestation period, with the relative continuous, and more intense, concentration-wise, exposure, might be the determining factor. Rather than continuous but milder exposure after birth.
While the asthma inhaler argument is a good one, I always find the lung transplant one to be quite weak.
People are not given lung transplants and associated therapies because it's 'safe'.
Rather because it's unavoidable, the alternative being sure death.
Therefore, the administrations of substances under that circumstance is not in itself indicative of their safety over the long period. Specific studies might find a correlation in a sense or the other, but the 'it's used for post lung transplant therapy' it's just not an argument, in my opinion.