Perchlorates are a group of toxic chemicals that have been linked to pollution in groundwater, primarily due to their potential to interfere with thyroid function. Traditionally associated with human-made sources such as explosives, rocket propellants, and industrial activities, these chlorine-based chemicals have raised concerns for years.
However, recent findings have revealed that perchlorates can also form naturally in the atmosphere, which adds a new dimension to their environmental impact.
Research published in PNAS highlights how these chemicals are produced in the stratosphere and could contribute to groundwater contamination. This new discovery emphasizes the need for a deeper understanding of perchlorate formation and its broader implications for pollution.
The Unexpected Origins of Perchlorates
Researchers had previously suspected that perchlorates formed in the stratosphere, but they did not know the exact conditions and sources. The latest study reveals that these toxic chemicals form at altitudes between 6 and 31 miles (10 to 50 kilometers) above Earth’s surface.
Perchlorates are not typically found on common sulfuric acid particles in the stratosphere but instead attach to rarer particles from smoke and organic materials. These particles, which can originate from wildfires and other natural processes, make their way into the stratosphere where cosmic rays trigger the chemical reactions that produce perchlorates.
“We don’t know if changing the particles in the stratosphere will cause more perchlorate or not, said Daniel Murphy,” the program lead in aerosol properties and processes at the National Oceanic and Atmospheric Administration (NOAA) Chemical Sciences Laboratory.
Murphy emphasized the importance of further research:
These were the most detailed measurements of the perchlorate. They had information we’d never had before on what the perchlorate was like for that natural source in the stratosphere.
The findings of the study were based on data gathered from NASA’s WB-57 aircraft, which can reach altitudes of 62,000 feet (around 19,000 meters), much higher than the typical commercial flight altitude of 30,000 to 42,000 feet (9,100 to 12,800 meters). This high-flying aircraft provided unique insights into the formation of perchlorates in the upper atmosphere, revealing their presence on these unusual particles.
The Impact of Pollution on Groundwater Contamination
Once formed in the stratosphere, perchlorates eventually fall to the Earth’s surface, where they can seep into groundwater. The problem is that perchlorates can persist in the environment for over 10,000 years in dry, arid areas, making them difficult to remove once they infiltrate water supplies. This poses serious risks for human health, as prolonged exposure to perchlorates can interfere with thyroid function, leading to developmental and cognitive problems.
As Murphy pointed out,
“We know, for example, that wildfires are increasing globally and that might mean that this natural source of perchlorate might increase.”
With more frequent fires due to climate change and human activity, there is growing concern that the pollution in the stratosphere could lead to higher concentrations of perchlorates falling to the Earth’s surface. This would contribute to further contamination of groundwater, posing significant risks to water safety worldwide.