Keywords: carcinogen lung lungs breathe breath breadth long belong health air oxygen pure clean dirty purity small particulate matter pm particular bidirectional link causality science asbestos cancer metastasize metaplasia apoptosis programmed rejuvenation telomeres longevity dna environment phenotype alveoli function structure physiology anatomy physiological pathological blame medicine medical legality precaution caution precautionary risk danger harm life experience journey irony ironic paradox round circle Catch22 Explore risingsun0618's 107 photos on Flickr! |