SESSION TITLE: Occupational and Environmental Lung Disease SESSION TYPE: Original Investigation Poster PRESENTED ON: Wednesday, October 26, 2016 at 01:30 PM - 02:30 PM PURPOSE: Previous studies demonstrated more severe bronchospasm during seasonal thunderstorms (thunderstorm asthma). Ahvaz, a metropolitan city located in Southwest of Iran, was named the World’s worst air polluted city by the World Health Organization (WHO) in 2011. Drastic changes in the ecosystem resulted in more thunder- and sand-storms. This is believed to be due to substantial ecologic changes in the Southern part of Iraq & Iran after decades of wars and industrialization. Evidence is lacking on spirometric changes after thunderstorms. In the current study, we aimed to examine the difference of spirometric indices among patients presented to the Ahvaz Jundishapur Medical University (AJMU) emergency departments (ED) with symptoms of thunderstorm-asthma during seasonal thunderstorms compared to those presented during other times. METHODS: In a cross-sectional case control study, we reviewed all patients presented to the AJMU’s nine hospital emergency departments in November 2013 (peak incidence of regional thunderstorms) with patients presented during seasons other than Fall. Overall, 585 patients were randomly selected, all of which underwent spirometry. If spirometry did not show evidence of obstruction, then patient underwent methacholine challenge test (MCT). All studies were conducted 3 weeks after resolution of acute symptoms. Primary outcome was spirometric indices and MCT results. Patients with history of COPD, pregnant women, those with hemoptysis or nonacceptable spirometry and chest pain were excluded. Using Chi-square and student’s t-test, we compared the characteristics and spirometric indices between two groups. RESULTS: Overall, 284 patients were enrolled during the thunderstorm period (cases) and 267 from other time-periods (controls). Cases and controlled were age and sex matched. Higher rate of history of asthma and smoking were noted among control (35.2% vs. 26.1%, p-value <0.001) and (20% vs. 13.7%, p-value 0.02), respectively. Despite insignificant difference between two groups in rate of obstructive pattern (30.6% vs. 33.3% among cases and controls, respectively), the severity of obstructive pattern and positive MCT were substantially higher among cases. CONCLUSIONS: The results of the current study showed more severe bronchial hyperresponsiveness during seasonal thunderstorms. CLINICAL IMPLICATIONS: Our results underscore the impact of ecosystem changes on people’s daily life. Further studies on the material and molecular characteristics of the regional thunderstorms are warranted. DISCLOSURE: The following authors have nothing to disclose: Maryam Haddadzadeh Shoushtari, Seyed Ali Mousavi, Hanieh Raji, Arash Foroozan, Seied Hamid Borsi, Esmail Eidani, Sakineh Afrakhteh, Mohammad-Ali Assarehzadegan, Kamran Masoumi, Roozbeh Sharif No Product/Research Disclosure Information