In this episode, Dr. Wu and co-host Darren Gonzalez, joined by Jordan Tsay and Kosuke Kimura, explore a striking paradox at the intersection of urban lighting, plant biology, and allergic disease, drawing on Artificial Light at Night Extends Pollen Season and Elevates Allergen Exposure, published in PNAS Nexus in 2026 by Brandt Geist, Lin Meng, Daniel S. W. Katz, Huidong Li, Franz Hölker, and Qian Xiao, a team led from Vanderbilt University. Pairing a decade of pollen counts with satellite measures of nighttime light across the Northeastern U.S., the researchers found that artificial light extends the pollen season at both ends — up to 130 additional pollen days a year between the darkest and brightest sites — while "severe" pollen days rose to 27 percent of the season versus 17 percent in darker areas. The effect may operate through two pathways at once: the same light that prolongs flowering in ragweed and London plane trees also disrupts the circadian regulation of allergic inflammation in humans. The loss of the night sky may be the most familiar consequence of urban lighting, but it may not be the most significant.