Following birth the average human lung continues to grow until the age of 18, stops growing for about 10 years, then declines naturally. The air we breathe combined with lifestyle and our genetic makeup impacts upon all three stages of lung development. Furthermore, research has shown that slow passive breathing drives particles deeper into lungs than increased breathing rates. Taken together, passive breathing in a poorly ventilated room combined with excessive dust exposure and humidity over 50% relative humidity, is not good for lungs. Scientists have noted immune reactions against house dust mite allergens deep in the delicate gas exchange area of the lung.
Recirculation of fouled air in an enclosed space can exacerbate the problem.
The 9th Symposium on Specific Allergy 2012, 27-29 September, Berlin, Germany www.alk abello.com/research/congresses/sosa/Documents/Abstracts%20only.pdf
'Nitric oxide production by alveolar macrophages in response to house dust mite faecal pellets and the mite allergens, Der p 1 and Der p2.' Peake et al. J. Aller. Clin. Immunol.; 2003, 112:531-7
'Mechanisms of particulate matter toxicity', S Salvi, S T Holgate, 'Clin. & Exper. Allergy', 1999, Vol. 29, pp 1187 - 1194