Asthma is a heterogeneous disease, and although much is understood about mechanisms of inflammation in allergic asthma, less is known about mechanisms of irritant-induced asthma (IA). Understanding the underlying similarities and differences in mechanisms of these two types of asthma will help focus current treatments and lead to development of new therapies. There is a longstanding NYU/Bellevue Asthma registry (NYUBAR), with a large population (N = 900) of asthma cases and controls, a program that has been housed at the CTSI (formerly GCRC). The destruction of the World Trade Center (WTC) resulted in massive dust, gas and fume exposures to local residents, workers and cleanup workers and individuals involved in rescue and recovery and adverse respiratory health effects of this disaster are reported more than 7 years after 9/11. Many responders, as well as those exposed as residents or local workers, have developed IA, asthma that arises after a lag from an environmental exposure . The WTC Environmental Health Center (WTC EHC) is one of the three New York City (NYC) WTC Centers of Excellence and the only one that focuses on treatment and monitoring of local workers and residents. As such, it has a large population of individuals with irritant-induced asthma. It has been proposed to use participants from the NYUBAR and the WTC EHC to expand the knowledge of irritant and allergic asthma. Non-invasive studies allow for the assessment of airway inflammation, a non-specific response to environmental exposure and injury. Recent technologies also allow for assessment of microRNA (miRNA), small RNAs that regulate gene expression at the post-transcriptional level and thus serve as a pathway to regulation of inflammation. The hypothesis will be tested in that airway inflammation in irritant and allergic asthma may be similar, but result from divergent miRNA regulatory pathways expressed in sputum cells. These studies will provide preliminary data for future studies that will help identify biological pathways to categorize these asthma phenotypes and target future treatment interventions.