The first autumn rains in Ahvaz, the provincial capital of Khuzestan in southwest Iran, foretell imminent dust storms—endless days of dust choking the city streets, leaving a film of yellow on cars and houses. They also mean thousands of hospital visits: Last year, 17,000 patients flooded the waiting room with complaints of dry coughs or symptoms of respiratory distress syndrome.Muhammad Hussein, a 28-year-old part-time student and employee of the provincial water company, was rushed to the hospital by his wife after experiencing shortness of breath, in addition to a persistent dry cough. "I have no memory of ever going to the hospital except after my niece was born," he told me. "But suddenly I felt like I could no longer breathe, it felt fatal." He said the symptoms went away within days.As emergency rooms grapple with the influx of new patients, scientists are trying to figure out exactly why this is happening. Politicians say it's pollen from the city's Conocarpus trees, planted in vast numbers across the city, or dust from nearby Iraq. Researchers point to other possible causes, including unregulated industries that dump waste into the air and water and rising temperatures from climate change. But with the government muzzling scientific research, solving the mystery has many barriers.Continue reading on Motherboard