Tag Archives: science

Will the new global mercury treaty be effective?

After four years of negotiations, delegates from more than 140 countries met last January to finalize the first global treaty to mitigate and prevent mercury pollution, the Minamata Convention. A new paper out from MIT Mercury looks at what the impact of the treaty will be. The bottom line? Globally, the treaty should avoid the future mercury increases that would otherwise occur but more aggressive action would be needed to decrease concentrations. Also, new science and analysis is needed to help policy-makers figure out the reason for environmental mercury changes. Read more at MIT News: Will the new global mercury treaty be effective? – MIT News Office.

The new paper, in Environmental Toxicology and Chemistry, is available here.

Mercury NOMADSS travel to Smyrna, TN!

Greetings from sunny Smyrna, TN, where for the last few weeks we (Noelle Selin, Amanda Giang and Shaojie Song) have been participating in a mission to measure mercury and other pollutants in the atmosphere. NOMADSS is the title of the airplane-based campaign, which stands for “Nitrogen, Oxidants, Mercury and Aerosol Distributions, Sources and Sinks.” It’s part of the larger Southeast Atmosphere study that’s investigating air quality in the southeast U.S. this summer. We are using our models to predict where we’re likely to find pollution, and to interpret data from the last several days to guide planning.

If you’re interested in following all of the science going on this summer, check out the Southeast Atmosphere Study home page, follow @SAS_Operations on twitter. There’s also a great blog on another component of the Southeast Atmosphere Study, the Southern Oxidant and Aerosol Study. Stay tuned for further updates from the field!

For mercury-specific updates, stay tuned to #MITMercury.


Scientist on the Scene: Advice for Working at the Boundary of Science and Policy from Dr. David Evers

by Alice Alpert and Danya Rumore

Amid observing and analyzing the INC5 negotiations, one question that seems to be on many of our MIT team members’ minds is “As scientists and academics, what is our role in influencing policy and decision-making?” More specifically, where does the line between science and advocacy lie, and how should a scientist who cares about a given issue—like mercury—interact (or not) with the policy realm?

Looking for answers, a couple of us cornered Dr. David Evers after an INC5 side session on “Global Mercury Hotspots.” Hosted by David and his colleagues at the Biodiversity Research Institute (BRI) and IPEN, the side session shared with decision-makers the findings of a recent scientific report, available here, which found high levels of mercury contamination in marine and freshwater ecosystems around the world.

David, the Executive Director of BRI, is an excellent example of a scientist who, through his work, seeks to work at the boundary between science and policy.

Explaining his work, David is quick to say, “I try very hard to be that unbiased scientist that goes about getting data in an unbiased way.” Trained as a conservation biologist, he readily acknowledges that he has a fundamental interest in the sustainability of human interactions with ecosystems. As a result, he has chosen to research mercury, a compound that is harmful to ecosystems and human health. However, he makes clear, he does not have a policy objective in mind when he formulates his research questions. Nor does a particular policy objective drive his research.

Instead, David says, his goal is to provide policy makers with the best possible information about mercury and its impacts on ecosystems; it is the decision-makers’ job to translate this information into the best possible policy, whatever that may be.

For example, one of David’s recent projects brought together a team of mercury researchers with the goal of compiling scientific findings about mercury in the northeast region of the US. The team then translated these scientific findings into a language and format that is easy for policy makers to fully understand, and shared this information with Congressional staffers and federal agencies in Washington, DC.

In contrast to a policy-advocate, David doesn’t focus on whether the scientific information he is presenting supports a certain policy objective. Nor does he interpret what his findings should mean for policy and decision-making.  “I’m an advocate for scientific information,” not a policy advocate, he explains. And while he thinks that the scientific findings presented during his Global Mercury Hotspots presentation are reason for concern, he adds that, here at the INC5, “I’m not advocating, it’s strange to say, for a stronger mercury policy.”

One concern many members of our MIT team struggle with is how to influence the world of policy with our research without compromising our integrity as unbiased scientists and academics. David recognizes this concern, but says that he feels that the boundary between science-advocate and policy-advocate is quite clear. As long as you’re only advocating for the use of good information in decision-making, you haven’t compromised your position as a credible source of unbiased information. Once you begin to let policy objectives direct your research or start advocating for specific policies, however, you’ve crossed the line into policy advocacy. And, he adds, “there’s no going back.”

So what’s his advice for academic “youngsters”, like us, who are interested in the intersection of science and policy?

First off, don’t be afraid to walk the line between science and policy, David says, just make sure to push for good science and focus on making this information readily available and understandable, rather than advocating for particular policies or regulations.

Second, you don’t need to know everything, and you can’t be an expert in everything. When your work crosses over into a discipline, like public health, that you don’t know well, bring in colleagues to help.

Third, as a scientific expert, people will often corner you to ask what you think the policy implications of your research are; when you respond, keep your opinion out of it and make clear that you are simply interpreting the data you have gathered.

Finally, he says, many scientists fear the media, because they are afraid that the media will misinterpret or skew their research and findings. David says that, when possible, it is preferable to work with journalists that you know and trust. But it’s important to get your findings into the public conversation, so don’t shy away from the media.

To learn more about working at the intersection of science and policy, read Amanda Giang’s Scientist on the Scene profile of Dr. Celia Chen and follow our blog and twitter (@MITmercury) as we report on the final day of the INC5 mercury negotiations.

Where in the World is Mercury? Part 2: Ocean and Fish

By: Noelle Selin

Our previous posts have addressed mercury in the atmosphere, global reservoirs such as oceans and soils, fish and human hair. Since oceans and fish are so important to global mercury exposure, I thought it would be useful to highlight sources of more information about mercury concentrations there. Two recent major studies have been released looking at the mercury problem in aquatic systems. Both of these are being presented at INC-5.

The Biodiversity Research Institute and IPEN, a non-governmental organization involved in the negotiations, have collected worldwide data on so-called “hotspots” of mercury concentrations in fish and human hair samples. The report, available here, found that mercury contamination is ubiquitous in marine and freshwater systems along the world. The report compares fish mercury concentrations from around the world to U.S. EPA human health advisory guidelines. Depending on the country, between 43 to 100% of fish sampled exceeded guidelines; in Japan and Uruguay, concentrations were so high that no consumption was recommended. These guidelines are for one fish mean per month.

From BRI-IPEN report: % of fish samples above health thresholds

Look for Alice Alpert’s interview with Biodiversity Research Institute’s David Evers, who’s here in Geneva, to be posted soon on our blog.

Another key report came out of the Coastal and Marine Mercury Ecosystem Research Collaborative (C-MERC), brought together by the Toxic Metals Superfund Research Program at Dartmouth College. The report analyzed and synthesized the current science on mercury sources  in seafood, and explored ecosystem responses to potential emissions controls.

The report found that mercury pollution is on the rise. In response to emissions controls, methylmercury in open ocean fish would only begin to decrease within several years to decades, while fish in coastal systems could respond over many decades to centuries. In other words, these effects are very long lasting. An interview with Celia Chen, who co-authored the report, was conducted here at INC-5 by Amanda Giang and is posted below.

Scientist on the Scene: A Profile of Dr. Celia Chen

Celia Chenby Amanda Giang

We’re certainly not the only science-folk at INC5. Over the course of the week, we’ve had the opportunity to meet many others who are here to support the negotiation in one way or another. Between sessions, I had the chance to catch up with one of them, Dr. Celia Chen, to find out a little more about why she’s here at the negotiations and what advice she has for us aspiring science-policy wonks.

Celia works in the Department of Biology at Dartmouth College, as part of the Toxic Metals Superfund Research Program. The program, which is funded by the National Institute of Environmental Health Sciences (NIEHS), looks at how mercury and arsenic in the environment affect ecosystem and human health. Within the program, she spends her time “wearing two different hats,” she says, one as a traditional eco-toxicologist and principal investigator for a project on the fate of metals in aquatic food webs, and a second as the principal investigator of research translation. “Translation is part of the mandate NIEHS gives for Superfund research,” Celia explains. Not only are researchers within these programs expected to clarify the science of contamination, but they’re also expected to make sure that their findings are communicated—or translated—to stakeholders (i.e., the people who can use or are directly affected by the findings), be they regulators from the EPA and FDA, or local food cooperatives.

She sees this research translation as a crucial role that scientists must play in policy-making forums. “We need to take what we know about the science and put it in a language that is accessible to policy makers,” she argues. Too often, critical scientific knowledge remains locked up in scientific publications, which, while they are the bread-and-butter of professional research, don’t always penetrate into policy circles. Celia feels that it is the responsibility of scientists to put their work in a form that resonates with—and is useful to—those in decision-making positions, from consumers making choices about their personal fish consumption, to negotiators working at an international scale. In fact, that’s why she’s attending the mercury negotiations. In 2010, the Toxic Metals Superfund Research Program created the Coastal and Marine Mercury Ecosystem Research Collaborative (C-MERC) to synthesize current knowledge on the environmental health impacts of mercury in a policy relevant way. Celia is attending INC5 to share the results of this project: the Sources to Seafood report.

“We tried to ask stakeholders first what they needed to know,” describes Celia. “The timing of [the Sources to Seafood report] was on purpose.”

Sources to Seafood was published on the tail of a domestic regulation in the US for mercury from coal-fired power plants, and directly before the final negotiating session for a global treaty on mercury. A key question that policy makers for both domestic and international regulation want clarified is how controlling different sources of mercury emissions and releases will actually affect human exposure. This question is important for both designing new policy and evaluating existing ones.

“When we began this work, most of the research done on mercury in the environment was done in freshwater systems, not marine. But most people are exposed to methylmercury through marine seafood,” Chen says. The report estimates that, for most of the US population, 85% of methylmercury exposure comes from marine fish. What are the sources of mercury that affect different marine and estuarine—that is, ocean and coastal—systems, from which fish are harvested? How do these sources affect human exposure? Researchers in biogeochemistry, food web dynamics, and health were all trying to answer different parts of these questions, but these different threads weren’t being woven together into a comprehensive picture.

“The most novel part of [the Sources to Seafood report],” Celia argues, is its interdisciplinary and cross-scale approach. “There are still many gaps and not enough data,” she says, but by synthesizing many different studies from different fields, a few conclusions can be drawn.

The most important point from the Sources to Seafood report that needs to be conveyed to decision-makers, Celia highlights, is that for each ocean system, critical sources of mercury may be different—some systems are most affected by atmospheric deposition, while others are most affected by inputs from rivers. Will the draft text on emissions and releases reflect these nuances? Celia hopes that reports like Sources to Seafood might help ensure that it does.

As for students interested in marine science-policy, Celia recommends that they consider the Sea Grant Knauss Fellowships, which match students with “host” policy makers in the executive and legislative branches of the US government in Washington D.C. These fellowships are open to any student, regardless of citizenship, enrolled in a graduate program at a US university that has a Sea Grant program.

For those interested in how the final treaty shapes up, keep following developments here on our blog and via twitter @amandagiang and @MITmercury.

Bioamplification, Bioaccumulation and Bioconcentration

By: Julie van der Hoop

The confusion between bioamplification, bioaccumulation and bioconcentration is understandable. Yesterday, delegates asked for a clarification and explanation as to how this happens. These terms are not interchangeable, though they are often used as if they were. This post should clarify the situation.


Bioamplification (or biomagnification, as the picture shows) refers to an increase in the concentration of a substance as you move up the food chain. This often occurs because the pollutant is persistent, meaning that it cannot be, or is very slowly, broken down by natural processes. These persistent pollutants are transferred up the food chain faster than they are broken down or excreted.

In contrast, bioaccumulation occurs within an organism, where a concentration of a substance builds up in the tissues and is absorbed faster than it is removed. Bioaccumulation often occurs in two ways, simultaneously: by eating contaminated food, and by absorption directly from water. This second case is specifically referred to as bioconcentration.

So, what have we learned? Bioconcentration and bioaccumulation happen within an organism, but biomagnification occurs across levels of the food chain. An example: phytoplankton and other microscopic organisms take up methylmercury and then retain it in their tissues. Here, mercury bioaccumulation is occurring: mercury concentrations are higher in the organisms than it is in the surrounding environment. As animals eat these smaller organisms, they receive their prey’s mercury burden. Because of this, animals that are higher in the food chain have higher levels of mercury than they would have due to regular exposure. With increasing trophic level, mercury levels are amplified.

Mercury Poisoning in Popular Culture

By: Philip Wolfe

In writing for this blog, I’ve been considering the role of communication and message-building in science and science policy. I’m often surprised about the extent of people’s scientific knowledge. Last year I was in a bar in Cambridge that was having a trivia contest, and 90% of the trivia teams there were able to correctly identify the isotope of cesium used to define the second as a unit of time measurement. Now, this was not a random sampling of the US population at large (it was a heavy MIT crowd), but I still think that’s pretty amazing.

Yet, while I’ve been prepping for these negotiations, I have been speaking with friends and colleagues and many of them have no idea about the problems mercury poses to the world. How can the same group of people, a group that clearly has a good science foundation, be so unaware of something that is such a significant policy issue?

I don’t have a great answer (and I would love to hear thoughts from other people), but I thought it might be fun to look at how mercury and mercury-related health impacts are portrayed in popular culture to perhaps gain some insight.

Spoiler Alert: It’s Not Mercury

Spoiler Alert: It’s Not Mercury

It turns out there may not be a whole lot of insight to gain. Over 177 episodes of House, not once was mercury the final diagnosis, and its not like the show shied away from outré solutions. Gold, cadmium, cobalt, lead and even selenium poisoning all make it on the final diagnosis tally sheet.

In fact, mercury poisoning is rarely mentioned as even a possibility for whatever pain or illness the primary patient may have. I’ll give the writers credit, when it comes up the details are pretty accurate. In “Son of a Coma Guy,” the team guesses that seizures and visual problems could be caused by mercury exposure at a luxury yacht factory. It’s a neat throwaway fact, as mercury was formerly used in mildew-resistant paints, but that practice has been discontinued in the US since the early 90’s.

One episode of the CBS Drama The 11th Hour, in which a brilliant biophysicist solves science crimes for the FBI and stops deadly experiments (yes, that really was the premise), did look at the long lasting and potentially devastating consequences of mercury releases to lakes and watersheds. I haven’t seen the episode, but judging by the fact that the series was cancelled after just 18 episodes, I think its fair to say it wasn’t part of the cultural zeitgeist.

In movies, mercury is not represented much more. While toxic chemicals have been covered in “based on true events” movies like A Civil Action (trichloroethylene) and Erin Brockovich (hexavalent chromium), Hollywood seems to be pretty silent on mercury. The glaring exception is a wonderfully bizarre environmental agitprop horror film from the 1970s called Prophecy. In it, mercury waste from a logging company creates violent raccoons, salmon large enough to eat a duck and, worst of all, a giant bear-monster that may also be a reincarnated, evil forest spirit. What it lacks in accuracy (and it lacks a lot in accuracy) it more than makes up for in terrible special effects.

Mercury’s absence in music is a bit more understandable. “Big Issue” songs, like Joni Mitchell calling for farmers to put away their DDT, have not been in vogue over the past few decades. The Dead Kennedy’s song “Kepone Factory,” about a chemical quite similar to DDT, references the Minamata disaster. In Minamata, Japan, over 2000 people have been diagnosed with a severe neurological impairments from mercury exposure. Japanese-American composer Toshiko Akiyoshi has written a jazz suite about the Minamata disaster, but unfortunately the LP with the most acclaimed recording of this piece has not been released in the US.

I’m not sure why mercury has not been more prevalent in popular culture. The potential dangers are chilling enough and the real-life tragedies (here for example) are certainly deserving of greater acknowledgement and provide compelling narratives for art. It certainly makes it harder for scientists and policymakers to enact real change, or for victims to be compensated for that matter, because there’s such a dearth of awareness of the underlying problem.

I wonder if some celebrity took up mercury as a personal cause if it could raise the public consciousness about the issue. There is evidence that it could. In late 2008, Jeremy Piven dropped out of the Broadway revival of Speed-the-Plow, citing hydrargaria from sushi consumption. When the news broke, Google searches for “mercury poisoning” nearly doubled.

Getting a high-profile public figure to support a global treaty on mercury could be one way to improve public awareness. As a scientist though, I fear the flip side of that coin. If mercury becomes a cause célèbre overnight, there may not be enough scientifically-sound publically-available literature to properly support any nascent movement. Ask a scientist studying vaccine safety how they feel about Jenny McCarthy for an idea of how scientists can quickly find themselves unable to control a scientific conversation.

Forms of Mercury: Beyond the Silver Liquid

By: Noelle Selin

It seems a bit strange to hear delegates at an intergovernmental negotiation on mercury discussing how to define “mercury.” Doesn’t the periodic table define it? Not only is mercury an element, but it’s also the reason why we’re all here in Geneva to negotiate an agreement. But defining exactly what is being addressed by the treaty is a critical issue – especially since mercury exists in many different forms in the environment.

Mercury in its liquid form is most  familiar.

Mercury in its liquid form is most familiar.

The chair’s draft treaty text defines mercury as “elemental mercury”. Elemental mercury is the liquid substance that many people recall when they think of mercury. In the atmosphere, most mercury is in elemental form, but it is a gas rather than a liquid. Elemental mercury is often abbreviated as Hg(0).

Another definition in the convention is “mercury compounds,” which addresses forms of mercury other than elemental mercury. What other forms of mercury are there?

Methylmercury is of particular concern, because it is the toxic form of mercury found in fish. Mercury is converted to methylmercury in aquatic systems by sulfate- and iron-reducing bacteria. For more on the health effects of methylmercury, see our earlier post.

In addition to elemental mercury, atmospheric mercury also exists as divalent mercury. Divalent mercury, also referred to as Hg(II), is formed when elemental mercury has undergone a chemical reaction of oxidation, losing electrons. In the atmosphere, Hg(II) can bind with other elements, but scientists don’t yet know exactly what these forms are. The chemical form of Hg(II) in the atmosphere could be HgCl2, HgBr2, Hg(OH)2, or HgO. The leading candidate is HgCl2, [give the name for this?], but this is a topic of current research. When Hg(II) is measured in the atmosphere, it is referred to as reactive gaseous mercury. Forms of mercury found in the ocean include both Hg(0) and Hg(II).

Emissions from different sources release different forms of mercury. Emissions from the surface ocean and land are in the form of elemental mercury. Anthropogenic sources, such as coal power plants, can release both Hg(0) and Hg(II). This is important because the two forms of mercury have different environmental behavior.

Hg(0) lasts for a long time in the atmosphere (6 months to a year), meaning that it circulates around the globe and can travel long distances. Hg(II) can easily rain or settle out after only a few days in the atmosphere, which means it is more likely to enter the environment nearby its source. Thus, reducing Hg(II) emissions will have important local benefits, compared with reducing Hg(0), which has important global benefits.

The behavior of mercury in the environment, however, is complex. Thus, we need to use computer models [pdf] to determine how mercury changes form and travels after it is emitted. These models use the chemical and physical properties of mercury in its various forms to estimate where mercury will travel over time. Mercury deposited to the environment as Hg(II) can return to the atmosphere as Hg(0). Additionally, Hg(0) can react (oxidize) to form Hg(II) in the atmosphere, and Hg(II) can then reduce back to Hg(0). In other words, mercury can change its form. This can occur anywhere in the atmosphere, even when it is being released from power plant plumes [pdf]. Ultimately, all mercury released continues to cycle through the environment for centuries, contributing to the global mercury legacy.

Many of these reactions are not well understood by scientists, so the transport and fate of mercury in the environment is a topic of significant ongoing research.

Mercury in Unexpected Products

by Hannah Horowitz

Written by Hannah Horowitz from Harvard University, this is the second in our series of Guest Scientist Blogs. Hannah is a graduate student in Earth and Planetary Sciences at Harvard University and a member of the Atmospheric Chemistry Modeling Group. Her research focuses on the environmental fate of mercury used in products and processes, and modeling the terrestrial mercury cycle.    Email: hmhorow@fas.harvard.edu        Website: http://people.fas.harvard.edu/~hmhorow/

When I first began my research on mercury used in products and processes, I was taken aback to learn that there were over 3000 known applications of the heavy metal [1]. What’s more interesting than the sheer number are some specific products containing mercury that are particularly surprising and unexpected. The vast variety of applications of mercury in the past and present are a result of its many unique chemical and physical properties. Its toxicity makes the disposal of mercury-containing products – some of which we may not realize are in our homes, schools, and businesses – challenging.

Some gym floors can release a lot of mercury.

Some gym floors can release a lot of mercury.

Polyurethane flooring used in school gymnasiums and indoor and outdoor tracks from the 1960s-1985 in the United States contain mercury used as a chemical catalyst [2]. One gym floor in Minnesota released mercury equivalent to breaking 280 compact fluorescent light bulbs per day, even 24 years after its installation [3]. However, measured concentrations and calculated total exposure in gyms tested in Ohio, Michigan, and Minnesota did not exceed levels that would result in health impacts [2, 4] from chronic (long-term) or acute (short-term) mercury exposure: 750 ng/m3 during 16 – 40 hours per week over a year, and 1800 ng/m3 for one hour, respectively [5]. Proper ventilation was key to reducing mercury levels [4]. However, average concentrations in Minnesota gyms were still around 200 times higher than typical outdoor background concentrations of 1.5 ng/m3 [6].

If a gym floor is believed to contain mercury, floor and air mercury concentrations should be measured, with help from the Agency for Toxic Substances and Disease Registry (ATSDR). If recommended exposures are exceeded, time spent in the gym should be limited, ventilation should be increased, and the floor may need to be removed (see [5]). Removal should be done carefully, as disturbing the floor may release more mercury than normal use [4]. Depending on its mercury content, the floor should be treated as hazardous waste or disposed in a lined landfill with leachate collection to prevent environmental releases [4].

Fishing lures

Fish lures can contain mercury.

Fish lures were once made using mercury.

Between the 1920s and the 1950s, fishing lures were made with visible liquid mercury inside to create motion and a shiny appearance to better attract fish [7]. Perhaps these mercury-containing fishing lures helped fishermen become exposed to methylmercury through the fish they successfully caught!

Now, care should be taken to avoid breakage and mercury release from the antique, fragile lures. For proper disposal, they should be brought to a hazardous waste collection program (varying state-by-state in the US) so the mercury can be removed and recycled [7].

Expected use in unexpected places

You can clearly see the mercury in this switch.

You can clearly see the mercury in this switch.

Some of the more typical uses of mercury – electrical switches and relays, lighting, and batteries – are widespread in many products that may be surprising. Mercury switches and relays help ovens and irons (pre-1990) shut off automatically [8, 9], thereby helping to prevent house fires. Similar switches and relays in cars brake with anti-lock brake systems (pre-2004) [10]  help prevent car crashes. However, these mercury-containing products may lead to environmental mercury contamination if their disposal is not handled properly. Electric lighting using mercury is ubiquitous – for example, LCD displays in cameras and sewing machines, UV lamps in printers, or fluorescent lamps in scanners and portable DVD players [8] to name a few. Button cell batteries present in children’s toys, calculators, and watches can also contain mercury [8, 11] and may be imported from other countries with less stringent mercury regulations [11].

The consumer should remove batteries from smaller products and contact their local municipality to find out about household hazardous waste collection services before throwing the object away [7, 12], so that they will not end up landfilled or incinerated along with general waste [13]. Electronics and larger appliances should also be collected if possible, and may be accepted by the original retailer depending on where you live (these services may or may not be free) [7, 12]. In the US, some automobile collection companies partner with End of Life Vehicle Solutions (or are mandated to do so by state law) to remove mercury-containing switches prior to turning the car into scrap metal, in order to prevent mercury emissions [10].

For more information, see the New England Waste Management Association’s mercury legacy products website.


  1. Nriagu, J. O. (1979), The biogeochemistry of mercury in the environment, Elsevier/North-Holland Biomedial Press, Amsterdam, the Netherlands.
  2. http://www.newmoa.org/prevention/mercury/projects/legacy/schools.cfm#gf
  3. http://www.newmoa.org/prevention/mercury/conferences/sciandpolicy/presentations/Herbrandson-Bush_Session3B.pdf
  4. http://www.atsdr.cdc.gov/HAC/pha/MercuryVaporReleaseAthleticPolymerFloors/MercuryVaporRelease-FloorsHC092806.pdf
  5. http://www.health.state.mn.us/divs/eh/hazardous/topics/mercury/hgflooringprofguide.pdf
  6. Slemr, F., E. G. Brunke, R. Ebinghaus, and J. Kuss (2011), Worldwide trend of atmospheric mercury since 1995, Atmospheric Chemistry and Physics, 11(10), 4779-4787.
  7. http://www.newmoa.org/prevention/mercury/projects/legacy/sport.cfm#fl
  8. https://imerc.newmoa.org/publicsearch/NEWMOA_IMERC.aspx#/CustomizedSearch
  9. http://www.newmoa.org/prevention/mercury/projects/legacy/appliances.cfm#ci
  10. http://www.newmoa.org/prevention/mercury/projects/legacy/automobiles.cfm#abs
  11. http://www.chem.unep.ch/mercury/GC-23-responses/GOV/Denmark-attachment-mercuryreport2004.pdf
  12. http://www.environment-agency.gov.uk/business/topics/waste/32096.aspx
  13. http://ec.europa.eu/environment/chemicals/mercury/pdf/study_report2008.pdf


Mercury’s Health Effects

by Alice Alpert, Ellen Czaika, and Amanda Giang

Pathways to exposure

Although these negotiations are explicitly focused on creating an environmental treaty, mercury’s major significance is its toxicity to humans. When you think about mercury, you probably picture a mercury thermometer. In a thermometer, you can literally see the silvery mercury in its bulb – this is liquid, elemental mercury. If you are absent minded and accidentally drop that mercury thermometer on the bathroom floor, the mercury will spills and form into beads. Although it’s not a good idea to touch this mercury, it is also not easily absorbed by the digestive system in this form.

The more pernicious way for this mercury to enter your body is if it vaporizes, which happens to a small amount of the liquid mercury at room temperature. If you inhale the vapor it can easily pass from your lungs into your blood stream and damage tissues. In fact, vacuuming up the spilled mercury can increase its vaporization and therefore the danger.

In truth, most people will not be exposed to mercury in this form. Instead, people working in chlor-alkali production, mercury mining and refining, thermometer production, dentistry, and in the production of mercury-based chemicals are at increased risk. Although measures have been taken to limit occupational exposure to mercury, many workers may continue to be at risk. Similarly, artisanal or small-scale gold miners are routinely exposed to mercury vapor at very high levels, in the process of burning the mercury-gold amalgam used to extract gold from ore. Indeed, miners and their communities often exhibit clear signs of mercury poisoning.

Another important pathway for mercury exposure is through eating seafood. In fact, according to the World Health Organization (WHO) (Section 2.4, paragraph 128), for many people this is the main pathway for human exposure to methylmercury. Exposure happens through the process of bioaccumulation and biomagnification. In brief, mercury is methylated to methylmercury (CH3HgX) by bacteria in the ocean and then accumulates in fish and marine mammals. Long-lived predatory fish at the top of the food-chain, such as swordfish, tilefish, shark, and tuna, can accumulate dangerously high concentrations of mercury. The US EPA lists guidelines for safe consumption of fish. Women who are pregnant or who could become pregnant should be especially careful about eating mercury contaminated fish because the mercury can be harmful to the developing fetus.

In addition, exposure could happen through dental amalgams. Elemental mercury is used in dental amalgam, and it can be ingested or its vapors can be inhaled. This is a contentious issue in the negotiations. The American Dental Association and the US Environmental Protection Agency state that mercury in dental amalgam is safe, while a report by the WHO (p.11) states that dental amalgam is a significant source of mercury exposure in those who have mercury fillings. We encourage you to look into the reports if you are concerned about this issue. For a solid overview of all pathways, see the WHO report on mercury exposure.

How and why does mercury make us so sick?

The most serious effects of elemental mercury vapor concern the nervous system, including tremors, erethism (a neurological disorder characterized by irritability and shyness), insomnia, muscle weakness, and memory loss. At especially high concentrations, the kidneys, thyroid, and pulmonary system can be affected. Similarly to elemental mercury, mercury in its organic form, methylmercury, has serious neurological effects, including neurobehavioral deficits, neuronal loss, loss of muscle movement, hearing loss, paralysis, and death.

Why is mercury so toxic for the nervous system? There are two specific processes: first, elemental mercury and methylmercury can easily cross the blood-brain barrier and once in the brain, can be oxidized to the mercuric ion (Hg2+), which cannot cross back across the barrier. Instead, mercury is trapped in the brain, where the second process begins, neurotoxin by excitotoxicity. What? Okay, we’ll slow down and explain these multi-syllabic words: in studies of rats, Hg2+ inhibits glutamine and glutamate transport, causing receptors for these molecules to become overexcited. This causes a large influx of the calcium ion into the cell, which activates enzymes that can lead to the neuron’s death, and thus the serious neurological effects. This second process is the reason why mercury is so toxic.

Mercury crucially effects developing fetuses. In the same way that methylmercury can cross the blood-brain barrier, it can also pass through the placenta from a mother to her fetus and then to the developing fetus’ brain. As a neurotoxin, methylmercury can also damage its nervous system, and in fact mercury has lasting negative effects when fetuses are exposed to concentrations at levels that are only 10%-20% of toxic levels for adults.

Babies born to women who consumed significant amounts of methylmercury while pregnant display symptoms similar to cerebral palsy, including delayed walking and talking, altered muscle tone and reflexes. Tragically, these impairments are permanent and affected will suffer from these impairments for their entire life. In fact, recently published research estimates that IQ reductions due to chronic, low-level fetal mercury neurotoxicity costs the European Union alone € 8-9 billion euros per year. Clearly, there are significant social and economic impacts from mercury exposure, particularly for the young.