Mohammad Reza Dayer - Department of Biology, Faculty of Science, Shahid Chamran University of Ahvaz, Ahvaz, Iran.

Background: Recurring annual asthma or asthma-like outbreak in Ahvaz City, Iran, has become a serious public health problem. A toxic gas, a chemical compound, or an allergen with unknown nature and mechanism leads to severe asthma outbreaks each year. Bronchospasm, cough, dyspnea, chest tightness, and wheezing are the main symptoms of these attacks. Oxygen and anti-asthma therapy are effective treatments in outbreak management. Based on our findings, it is hypothesized that vast amounts of ammonium nitrate used in agriculture underlay high concentrations of nitrate. This substance is transported by PM۱۰ and is the main cause of the respiratory outbreak.Methods: The concentration of nitrate was determined by the ion chromatography method in dust samples during ۲۰۱۵-۲۰۱۶. Using spectroscopic methods, the effect of nitrate ions on hemoglobin oxidation and methemoglobin formation was studied.Results: Our results indicate that the concentration of ammonium nitrate in dust collected from indoor spaces is five times higher than the levels allowed amount in airborne pollutants. Our findings also indicate that this concentration of nitrate in the bloodstream can instantly increase methemoglobin percent to ۱۸% with symptomatic consequences.Conclusion: The exact mechanism proposed by this study is that inhaled nitrate or nitric acid finally increases the nitrate in the circulation of affected individuals. Hemoglobin oxidation and methemoglobin formation are the subsequent events leading to methemoglobinemia with asthma-like reactions seen in Ahvaz respiratory syndrome. Restricting or even prohibiting ammonium nitrate application in agriculture seems to be an urgent measure to stop Ahvaz's recurring respiratory syndrome.

Asthma, Dust, Ammonium Nitrate, Ahvaz, PM ۱۰, methemoglobinemia