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WATERLINE - June, 2024

Ask Dr. Waterline

Hey Dr. Waterline!
Every year on July 4th when I see fireworks exploding over my local lake and the colors and sparks showering down into the water, I can’t help but wonder about the impacts to water quality. I hate to be a party pooper, but surely that’s not good for the lake? What do you say?


I’m glad you asked as we approach another 4th of July season! The main chemicals of concern to lake water quality from fireworks displays are ammonium or potassium perchlorate salts, which are used as a propellant, and heavy metals associated with the colors of the fireworks. There have been few comprehensive studies on the water quality impacts of July 4th firework displays. Those that have taken measurements before and after displays tend to focus on perchlorate inputs. In 2008, EPA conducted a study on a small lake in Oklahoma and found measurable perchlorate in the waters after the display, and levels attenuated naturally over a 20-day period. Closer to home, Snohomish County conducted a brief study on a small lake pre- and post-fireworks and also found measurable perchlorate, but no obvious change in metals concentrations.

The impact of fireworks on lake water quality is likely a question deserving of further study. In fact, the North American Lake Management Society (NALMS) is beginning a study and looking for volunteers to sample American lakes before and after 4th of July to study the presence of perchlorates. Learn more and volunteer here: https://www.nalms.org/perchlorate-fireworks/

Based on what we know now, the short-term inputs of salts and metals to the lake don’t seem to have an acute impact on aquatic life. Furthermore, a brief input of particulate phosphorus from fireworks is also unlikely to affect lake nutrient concentrations in the water column. These findings remind us that our lake ecosystems can sometimes handle short-term impacts, but long-term pressures on them — or continued short-term impacts — can be a different story.

Thanks for caring about clean lakes!


EPA study: Wilkin, R. T., Fine, D. D., & Burnett, N. G. (2007). “Perchlorate behavior in a municipal lake following fireworks displays.” Environmental Science & Technology, 41(11), 3966-3971.

Snohomish study – https://snohomishcountywa.gov/Archive/ViewFile/Item/2076


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