When Fog Becomes a Toxic Killer

What's in California's morning dew?

At a recent meeting of the American Geophysical Union, researchers talked about a disturbing finding: California coastal fog contains a significant amount of mercury. The substance comes in the form of monomethylmercury, which at high enough levels is poisonous to animals and humans. Additionally, the scientists’ mercury findings arrive amidst an overall discovery that coastal fog is increasing along California.

Researchers are quick to point out, though, that the levels of mercury found in the fog so far are not dangerous to humans. The real risk lies in the aquatic food chain. Mercury is a neurotoxin that accumulates and concentrates in organisms over time. We often hear about mercury because it can reach high levels in fish and other organisms that humans consume. The reason for this type of mercury showing up in animals isn’t quite understood, but some scientists speculate that it has something to do with coal combustion emissions.

Researchers see the initial results as a reason to keep tabs on the fog and continue to monitor levels of mercury within it. In a world of competitive funding, their findings seem to indicate that environmental-monitoring activities are a worthwhile endeavor, if we are to understand the coming threats to our ecosystems and food chains.

Again, humans are still safe from the direct mercury impacts of the fog, but the harms of ingesting the high levels of mercury that can accumulate in other animals include very serious health issues, such as “kidney failure, birth defects, and neurological impairment.”

Mercury levels aren’t just a California issue. Levels on the surface of oceans worldwide have tripled since the industrial revolution. But at least we can be thankful that we have the technology to detect mercury and try to do something about it while the problem is still at a level we can handle.

Image Credit: Justin Sullivan / Staff via Getty Images


Stefani is a writer and urban planner based in Oakland, CA. She holds a master’s in City and Regional Planning from UC Berkeley and a bachelor’s in Human Biology from Stanford University. In her free time, she is often found reading diverse literature, writing stories, or enjoying the outdoors.  Follow her on Twitter: @stefanicox

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