Iodine is an essential trace element for mammals and aquatic plants. Increasing alga populations due to serious eutrophication in the coastal waters of China promote iodine emission. China contributes about 60 % of the global cultivated seaweed production. Iodine is likely emitted to the atmosphere and transformed into nanoparticles during the farming, harvesting, and processing of seaweed. Wild and farmed algae make the coastal area of China a potential hotspot of new particle formation.