http://theguardian.com/environment/ethicallivingblog/2009/jul/31/sky-lanterns and http://bbc.com/news/magazine-23129276 are critical about use of lanterns which float into the sky using hot air because of risk of fire and litter, but the same sites do not question the impact of firework displays, especially massive ones during Bonfire Night and the New Year.
For the same typical audience size, how do they compare?