<P> Fireworks pose risks of injury to people, and of damage, largely as a fire hazard . </P> <P> Fireworks produce smoke and dust that may contain residues of heavy metals, sulfur - coal compounds and some low concentration toxic chemicals . These by - products of fireworks combustion will vary depending on the mix of ingredients of a particular firework . (The color green, for instance, may be produced by adding the various compounds and salts of Barium, some of which are toxic, and some of which are not .) Some fisherman have noticed and reported to environmental authorities that firework residues can hurt fish and other water - life because some may contain toxic compounds such as antimony sulfide . This is a subject of much debate due to the fact that large - scale pollution from other sources makes it difficult to measure the amount of pollution that comes specifically from fireworks . The possible toxicity of any fallout may also be affected by the amount of black powder used, type of oxidizer, colors produced and launch method . </P> <P> Fireworks have also been noted as a source of perchlorate in lakes . The U.S. Environmental Protection Agency's Richard Wilkin and colleagues, have conducted research on the use of pyrotechnic devices over bodies of water noting concerns over the effects of environmental perchlorate on human health and wildlife . Sources of perchlorate range from lightning and certain fertilizers to the perchlorate compounds in rocket fuel and explosives . Scientists long suspected community fireworks displays were another source, but few studies had been done on the topic . Wilkin's group has now established fireworks displays as a source of perchlorate contamination by analyzing water in an Oklahoma lake before and after fireworks displays in 2004, 2005 and 2006 . Within 14 hours after the fireworks, perchlorate levels rose 24 to 1,028 times above background levels . Levels peaked about 24 hours after the display, and then decreased to the pre-fireworks background within 20 - to 80 days . The study is detailed in the June 1, 2007 issue of the journal Environmental Science & Technology . (Environ . Sci. Technol., 2007, 41 (11), pp 3966--3971) </P> <P> Perchlorate, a type of salt in its solid form, dissolves and moves rapidly in groundwater and surface water . Even in low concentrations in drinking water supplies, perchlorate is known to inhibit the uptake of iodine by the thyroid gland . While there are currently no federal drinking water standards for perchlorate, some states have established public health goals, or action levels, and some are in the process of establishing state maximum contaminant levels . For example, the US Environmental Protection Agency have studied the impacts of perchlorate on the environment as well as drinking water . California has also issued guidance regarding perchlorate use . </P>

What is the diameter of a firework explosion