Argument: 'A city's public health office notes that emergency-room visits for respiratory illness rose sharply the same month a new industrial coating plant opened nearby. Some residents attribute the rise to airborne particulates from the plant. But hospital records show the increase began three weeks before the plant's ventilation systems were ever switched on, so the plant cannot be the cause of that initial rise. **Because the timing rules out the plant, some other shared factor must explain the early spike.** Weather data reveal that an unusual pollen surge hit the region in that same three-week window, and pollen surges are independently documented to raise respiratory ER visits. **The early spike in respiratory visits was most likely driven by the pollen surge, not by the plant.** None of this, however, shows that the plant played no role in the respiratory visits recorded after it began operating, and the office recommends continued air-quality monitoring near the plant.' The two boldface portions are marked.