Firework as a source of perchlorate-a contaminant of emerging concern

Potassium Perchlorate (KClO4) as an oxidizer is commonly used in fireworks to produce temperatures of 1700 to 2000°C. Such high temperature make it possible to excite the electrons surrounding the nuclei of metal atoms and when the absorbed energy is emitted, different atoms give out specific colors. 

Firework is an important source of perchlorate to aquatic environment. Monitoring data show over four percent of public water systems have detected perchlorate.  In a human biomonitoring campaign, perchlorate was found in all human urine samples collected from the U.S. The chemical was also found in cow's milk in California with an average level of 1.3 µg/L, which may have entered the cows through feeding on crops that had exposure to water containing perchlorates. Studies have indicated that perchlorate can disrupt the thyroid’s ability to produce hormones needed for normal growth and development.

Because of the adverse effect on the health and frequent detection in public water systems at levels causing a public health concern, the U.S. Environmental Protection Agency issued a "regulatory determination" in 2011 that perchlorate meets the Safe Drinking Water Act criteria for regulation as a contaminant. Prior to issuance of its regulatory determination, the U.S. EPA issued a recommended Drinking Water Equivalent Level (DWEL) for perchlorate of 24.5 µg/L. Such regulation provides
opportunity for health risk reduction for the between 5.2 and 16.6 million people who may be
served drinking water containing perchlorate.

References and more to read:

http://water.epa.gov/drink/contaminants/unregulated/perchlorate.cfm
http://water.epa.gov/drink/contaminants/unregulated/upload/FactSheet_PerchlorateDetermination.pdf
http://pubs.acs.org/doi/abs/10.1021/es504444e
Blount, B. C.; Valentin-Blasini, L.; Osterloh, J. D.; Mauldin, J. P.; Pirkle, J. L. Perchlorate exposure of the US Population, 2001−2002. J. Exposure Sci. Environ. Epidemiol. 2007, 17 (4), 400−407.