Global Pollution Carries Local Implications

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Illustration by Celia Fong.
Illustration by Celia Fong.

The discussion of global pollution has become nearly synonymous with that of CO2, but research from two UC Santa Cruz scientists is proving another harmful global pollutant is on the rise — mercury.

Along with a team of researchers, Peter Weiss-Penzias, UCSC assistant researcher and atmospheric chemist, along with a team of researchers grabbed the scientific community’s attention in 2012 when he found that the California coast’s famed fog is harboring the neurotoxin mercury. This year he’s looking at the ecosystems bathed in this mercury- laced fog and finding high levels in some Santa Cruz pumas.

“The Santa Cruz mountain pumas have 10 times more mercury than the inland pumas,” Weiss-Penzias said. Mercury in fog is picked up from the ocean, transformed into the toxic element methylmercury and deposited onto land and picked up by animals.

Like carbon dioxide, mercury occurs naturally but can have disastrous effects on human and ecological health when emitted into the atmosphere in large amounts, including kidney and brain damage and birth defects in exposed fetuses, according to the Center for Disease Control.

“We had this information from land-based archives that said the amount of mercury moving around on earth today looks like it’s about three to seven times as much pre- industrially,” said UCSC assistant professor and biogeochemist Carl Lamborg.

Lamborg’s research is focused on mercury pollution in ocean waters, and he gathers data while he spends months at a time aboard research vessels. Mercury bioaccumulates, meaning it increases within organisms that consume it. This makes it especially hazardous for organisms higher on the food chain, like pumas.

“It turns out, for mercury, you don’t have to put that much into the system because of the bioaccumulation in the food chain,” Weiss-Penzias said. A little bit of mercury can do a lot of damage.

The U.S. Environmental Protection Agency (EPA) issues the most pollutant advisories for mercury. There are three forms of mercury: elemental, inorganic and organic compounds like monomethyl mercury.

“One form, the monomethyl, is the form that accumulates in fish, and is the form we’re most readily exposed to. It’s the most biologically sticky, it’s really hard for our bodies to get rid of,” Lamborg said.

Fish and shellfish consumption is the primary point of human exposure to mercury in North America. The average American eats 15.8 pounds of seafood a year, according to a 2009 survey from the National Oceanic and Atmospheric Administration.

Fish and shellfish accumulate mercury that the atmosphere deposits into the ocean. There are an estimated 80,000 metric tons of mercury pollution invading the world’s oceans, Lamborg said in an email. That’s as heavy as 707 blue whales.

A recent article co-authored by Weiss-Penzias found areas of increase in atmospheric mercury levels in Central-Western regions of the country and decreasing or unchanged levels in Eastern regions.

These are what Lamborg calls regional stories — pockets of higher concentrations of mercury over land and in the ocean.

“There’s a regional story now,” Lamborg said. “The north Atlantic seems to be cleaning up a bit while the north Pacific is continuing to get loaded with pollution.”

There is no current consensus among the scientific community regarding global trends in mercury levels. However, overall levels in the U.S. have declined, thanks in part to EPA emission controls created to mitigate a prior global polluter and acid rain inducer, sulfur dioxide. Lamborg said these emission controls helped to curb the output of U.S. sulfur and mercury pollution.

However, if the U.S. is cleaning up its mercury pollution, then why are scientists like Weiss-Penzias and Lamborg observing higher levels of mercury?

Weiss-Penzias and his team determined the mercury levels were effects of rising mercury emissions from other countries, most likely from regions of the world that rely on coal power — the leading contributor to mercury pollution.

The largest mercury emitter is China, which accounts for 44 percent of the world’s coal production. It even increased its coal use by 415 percent between 1980 and 2010, according to the U.S. Energy Information Administration.

“We hypothesize that the location of these regions with the largest positive trends in the center of the continent is consistent with a contribution from long-range transported Hg [mercury] emissions in the free troposphere,” according to the January 2016 article published by Weiss-Penzias and his colleagues.

Pollution knows no borders, and like CO2, mercury is a global problem that, if left unaddressed,will continue to grow.

“Mercury — we don’t know what it’s going to do exactly,” Weiss-Penzias said, “But the models suggest that it is going to increase up through 2050.”