Wikipedia

Mercury in fish

The presence ofmercuryinfishis a health concern for people who eat them, especially for women who are or may become pregnant, nursing mothers, and young children. Fish andshellfishconcentrate mercury in their bodies, often in the form ofmethylmercury,a highly toxicorganomercurycompound. This element is known tobioaccumulatein humans, so bioaccumulation inseafoodcarries over into human populations, where it can result inmercury poisoning.Mercury is dangerous to both naturalecosystemsand humans because it is ametalknown to be highlytoxic,especially due to itsneurotoxicability to damage thecentral nervous system.[1][2]

Nearbyanthropogenicsources, such as coal burning and iron mining, can contaminate water sources with methylmercury, which is efficiently absorbed in the bodies of fish. Through the process ofbiomagnification,mercury levels in each successivepredatory stageincrease.

In human-controlled ecosystems of fish, usually done for market production of wanted seafood species, mercury clearly rises through the food chain via fish consuming smallplankton,as well as through non-food sources such as underwater sediment.[3]

Fish products have been shown to contain varying amounts ofheavy metals,particularly mercury and fat-soluble pollutants fromwater pollution.Species of fish that arelong-livedand high on thefood chain,such asmarlin,tuna,shark,swordfish,king mackerelandtilefishcontain higher concentrations of mercury than others.[4]Cetaceans(whalesanddolphins) also bioaccumulate mercury and other pollutants, so populations that eatwhale meat,such asthe Japanese,Icelanders,Norwegiansandthe Faroese,are also vulnerable to mercury ingestion.

Biomagnification

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Main article:Biomagnification

The consumption of fish is by far the most significant source of ingestion-related mercury exposure in humans and animals.[5]Mercuryandmethyl mercuryare present in only very small concentrations inseawater.However, they are absorbed, usually as methyl mercury, byalgaeat the start of thefood chain.This algae is then eaten by fish and other organisms higher in the food chain. Fish efficiently absorb methyl mercury, but excrete it very slowly.[6]Methyl mercury is not soluble and therefore not excreted. Instead, it accumulates, primarily in theviscera,although also in the muscle tissue.[7]This results in thebioaccumulationof mercury, in a buildup in theadiposetissue of successivetrophic levels:zooplankton,smallnekton,larger fish, and so on.[8]The older that such fish become, the more mercury they may have absorbed. Anything that eats these fish within thefood chainalso consumes the higher level of mercury that the fish have accumulated, including humans.[8]This process explains why predatory fish such asswordfishandsharksor birds likeospreyandeagleshave higher concentrations of mercury in their tissue than could be accounted for by direct exposure alone. Species on the food chain can amass body concentrations of mercury up to ten times higher than the species they consume. This process is called biomagnification. For example, herring contains mercury levels at about 0.1 parts per million, while shark contains mercury levels greater than 1 part per million.[9]

Origins of mercury pollution

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See also:Mercury cycleandMercury pollution in the ocean

Terrestrial mercury pollution

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There are three types of mercury emission:anthropogenic,re-emission, and natural, includingvolcanoesandgeothermalvents. Anthropogenic sources are responsible for 30% of all emissions, while natural sources are responsible for 10%, and re-emission accounts for the other 60%. While re-emission accounts for the largest proportion of emissions, it is likely that the mercury emitted from these sources originally came from anthropogenic sources.[10]

Anthropogenic sources include coal burning,cementproduction,oil refining,artisanand small-scale gold mining, wastes from consumer products,dental amalgam,thechlor-alkaliindustry, production ofvinyl chloride,and the mining,smelting,and production ofironand other metals.[10]The total amount of mercury released by mankind in 2010 was estimated to be 1,960 metric tons. The majority of this comes from coal burning and gold mining, accounting for 24% and 37% of total anthropogenic output respectively.[10]

Re-emission, the largest emitter, occurs in a variety of ways. It is possible for mercury that has been deposited in soil to be re-emitted into themercury cycleviafloods.A second example of re-emission is aforest fire;mercury that has been absorbed intoplant lifeis re-released into theatmosphere.While it is difficult to estimate the exact extent of mercury re-emission, it is an important field of study. Knowing how easily and how often previously emitted mercury can be released helps us learn how long it will take for a reduction in anthropogenic sources to be reflected in the environment. Mercury that has been released can find its way into theoceans.A 2008 model estimated the total amount of deposition into the oceans that year to be 3,700 metric tons. It is estimated thatriverscarry as much as 2,420 metric tons.[10]Much of the mercury deposited in the oceans is re-emitted, however; as much as 300 metric tons is converted into methyl mercury. While only 13% of this finds its way into the food chain, that is still 40 metric tons a year.[10]

Much (an estimated 40%) of the mercury that eventually finds its way into fish originates withcoal-burning power plantsandchlorine productionplants.[11]The largest source of mercury contamination in the United States is coal-fueled power plant emissions.[12]Chlorine chemical plants use mercury to extract chlorine from salt, which in many parts of the world is discharged as mercury compounds in waste water, though this process has been largely replaced by the more economically viable membrane cell process, which does not use mercury. Coal contains mercury as a natural contaminant. When it is fired for electricity generation, the mercury is released as smoke into the atmosphere. Most of this mercury pollution can be eliminated if pollution-control devices are installed.[11]

Mercury in theUnited Statesfrequently comes frompower plants,which release about 50% of the nation's mercuryemissions.[13]In other countries, such asGhana,gold miningoften uses mercurycompounds,leading to workers receiving significant quantities of mercury while performing their jobs. Such mercury from gold mines is specifically known to contribute tobiomagnificationin aquaticfood chains.[14]

Elemental mercury often comes fromcoalpower plants, andoxidizedmercury often comes fromincinerators.Oil-fired power plants also contribute mercury to the environment.[1]Theenergy industrytherefore is a key player in the introduction of mercury into theenvironment.When addressing the issue of reducing seafood mercury bioaccumulation on a global scale, it is important to pinpoint major energy producers and consumers whose exchange of energy may be the root of the problem.

Aquatic mercury pollution

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The farming ofaquatic organisms,known asaquaculture,often involvesfish feedthat contains mercury. A study by Jardine has found no reliable connection between mercury in fish food affecting aquaculture organisms or aquatic organisms in the wild.[15]Even so, mercury from other sources may affect organisms grown through aquaculture. InChina,farmed fish species, such asbighead carp,mud carp,andSiniperca chuatsi,carried 90% of total mercury content in all of the measured fish in a study by Cheng. This study also concluded that mercury bioaccumulates through food chains even in controlled aquaculture environments. Both total mercury and methyl mercury absorption was found to be derived from sediments containing mercury, not mainly from fish feed.[3]

TheHawaii Institute of Marine Biologyhas noted that fish feed used in aquaculture often containsheavy metalssuch as mercury,lead,andarsenic,and has dispatched these concerns to organizations such as theFood and Agriculture Organizationof theUnited Nations.

Mercury can get intofreshwatersystems bypoint sourcesand extended flooding.[8]InCanada,mercury poisoning inGrassy Narrowswas likely caused by a spill at apaper mill,which is a point source. Non-point sources include floods that create hospitable habitats forbacteriathat can convert mercury tomethylmercury,which is the toxic form that bioaccumulates through aquaticfood webs.The effects of these different sources of mercury have been studied at theExperimental Lakes AreainOntario, Canada,using research procedures including whole-lake ecosystem experiments and non-lethal fish musclebiopsies.[8]

Controlling output of mercury pollution sources

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The U.S. Geological Survey projects that in the next several decades there will be a 50 percent increase in mercury levels.[citation needed]The study also shows that the increases are connected through industrial emissions and are not natural as previously thought.[citation needed]However, by decreasing emissions from industrial plants, the possibility of decreasing the high level of mercury remains plausible.[16]Several nations are currently implementing systems that will detect and therefore later be able to control the output of mercury into the atmosphere. Air pollution control devices (APCDs) have been implemented inSouth Koreaas thegovernmentis starting to take inventory of mercury sources. Mercury pollution can also be removed byelectrostatic precipitators(ESPs). Bag-based filters are also used infactoriesthat may contribute mercury to the environment.Flue-gas desulfurization,normally used to eliminatesulfur dioxide,can also be used in conjunction with APCDs to remove additional mercury beforeexhaustsare released into the environment.[1]Even so, countries such as South Korea have only begun to use inventories of mercury sources, calling into question how fast anti-mercury measures will be put into factories.

Health effects and outcomes

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Disparate impacts

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Mercury content in fish does not affect all populations equally. Certain ethnic groups, as well as young children, are more likely to suffer the effects of methyl mercury poisoning. In the United States, Wallace gathered data that indicated 16.9% of women who self-identify asNative American,Asian,Pacific Islander,or multiracial exceed the recommendedreference doseof mercury.[17]A study done on children of theFaroe Islandsin the North Atlantic showed neurological problems stemming from mothers consumingpilot whalemeat during pregnancy[18](seeWhaling in the Faroe Islands). A 2020 NBER paper found that in coastal Colombia, those born during periods when fish catches have high mercury content have worse educational and labor market outcomes than those born during periods of low mercury content in fish.[19]

Regulation and health

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While various studies have shown high concentrations of mercury accumulated in fish, medical cases often go unreported and pose a difficulty in correlating mercury in fish with human poisoning. Environmental issues cover a broad range of areas, but medical cases that are associated with pollutants released into the environment by factories or construction areas causepublic healthissues that affect not only the environment but also human well-being. Substances poisonous to thehuman bodyin a particular amount or dose may not cause any symptoms over time. While there are limits to how much of anything the body can have, mercury is a particular poison that produces immediate physical symptoms when the body has been accumulating it over a period of time.[clarification needed]

In the United States, the Environmental Protection Agency estimates the amount of mercury in human blood that is not likely to posefatalhealth outcomes. The agency is in charge of enforcing regulations and policies that cover a range of environmental topics.[20]Analysis of blood mercury concentrations in childbearing women has documented that exposure to methyl mercury (MeHg) occurs primarily through the consumption of fish.[21]The U.S. FDA highly recommends against pregnant women and young children consuming raw fish. Pregnant women and young children often lack strong immune systems and are more at risk for foodborne illnesses.[22]

Medical cases and exposure to mercury

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In the United States, theEPAprovides advice about the levels of mercury that are non-fatal in humans. Symptoms of exposure to high levels of methyl mercury include disturbedvision,hearing,and speech, lack of coordination, andmuscle weakness.Medical studies have examined the correlation of fish consumption and health issues. American studies have presented evidence of fish consumption and its effects onchild development.Longitudinal studiesagree that human activities release mercury that accumulates inmarine life.[23][failed verification]Addressing the issues of fish consumption forces health officials to recognize the sources of mercury in the human body. SpecificNative Americantribes are vulnerable to a high exposure of mercury. Studies have determined that thesenative peoplesin the United States suffer more from mercurypoisoningand illness than any othercohortgroup in the country. This is due to the fact that fish is a main source of protein. Exposure risk was assessed through a medical study, thus raisingjudicialissues of whether thepublic healthof these groups is a priority in the United States.[24]

Work and exposure

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Most cases that arise are due to work exposure ormedicinal poisoning.Environmental justiceadvocates can relate these mercury cases to the unregulated amount of mercury that enters the environment. Workers can be exposed to mercury through the manufacture of fluorescent tubes,chloralkali,oracetaldehydeamong other products.Anthropogenicsources and places where mercury is released or used as a solid or vapor puts these has causedfatigue,dizziness,hyperhidrosis,chest congestion, and loss of motor skills. When taken to the hospital, theneurotoxicitylevels had already exceeded the maximum amounts.[25]Over-the-counter medicines have been shown to have traces of mercurous chloride. Medical research reported that the children who received doses of these medicines experienced physical symptoms such as "drooling,irregular arm movements, and impaired gait ".[26]Exposures to this result in severe physical impairments unregulated chemicals that are put in products. The intake oflaxativesthat contained about 120 mg of mercurous chloride has also been cases of mercury's toxicity.[27]

Even in countries, such asSweden,that have phased out mercury in thedental industryand manufacturing, lingering quantities of mercury still exist inlakesand coastal areas. Moreover, global contributions of mercury to the environment also affect that country. A study in Sweden selected 127 women who had a high level of fish consumption. Around 20% of the women selected, afterhairandbloodsamples, were found to have exceeded theEPA's recommendedreference doseof 0.1 micrograms of methyl mercury per kilogram of body weight. Additionally, the study concluded that there was "no margin of safety for neuraldevelopmental effects in fetus[es]"[28]without removing the offending species of fish from the diets of the women. This indicates that families intending to raise children should be especially careful about exposing their unborn babies to toxic mercury via fish.

Children exposed to mercury are particularly susceptible topoisoningsince the ratio of food, water, and air intake versus individual body weight is much higher than that ofadults.[29]Additionally, children undergo fast growth that causes them to be more susceptible to damaging exposure to methylmercury, as well as the long term consequences of such exposure duringchildhood development.[29]Young age plays an important role in terms of damage caused by mercury, and much literature on mercury focuses onpregnant womenand specific precautions designed to prevent youth mercury exposure. Prenatal methylmercury exposure does causebehavioralproblems in infants and worsenedcognitivetest performance. Additionally, Hughner estimates that 250,000 women may be exposing their unborn babies to levels of methyl mercury above recommended federal levels.[30]

Economically, there does not seem to be a difference in mercury exposure based onsocioeconomicbracket and the ability to buyfishfrom the market. One study shows "no significant differences in mercury levels intuna,bluefish,andflounderas a function of type of store or economic neighborhood ".[31]

By nation

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Certaincountrieshaveculturaldifferences that lead to morefish consumptionand therefore more possible exposure toseafoodmethylmercury. InGhana,the local population traditionally consumes large quantities of fish, leading to potentially dangerous amounts of mercury in thebloodstream.[14]In theAmazonian Basin,during therainy season,herbivorousfish dominate the diet of 72.2% of the women selected from a particular Amazonianvillage.Analysis also shows increase of mercury content in the hair of humans who eat fish on a daily basis in the Amazon.[32]

The most serious case of mercury poisoning in recent history was in the Japanese city ofMinamata,in the 1950s.Minamata poisoningdemonstrated that significantprenatalandpostnatalexposure to high levels of methylmercury caused serious neurological problems. Minamata victims also showed higher than normal signs ofpsychiatric diseases,along with thosediseasesbeing caused by underlying neurological issues.[33]

A 2014 USGS survey of mercury levels in the United States water system found that methylmercury concentrations in fish were typically highest in wetland areas including the coastal plain streams in the Southeast. Fish methylmercury levels were also high in the Western US, but only in streams that had been mined for mercury or gold.[34]

Minamata disease

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In the 1950s, inhabitants of the seaside town ofMinamata,onKyushuisland in Japan, noticed strange behavior in animals. Cats would exhibit nervous tremors, dance, and scream. Within a few years, this was observed in other animals; birds would drop out of the sky. Symptoms were also observed in fish, an important component of the diet, especially for the poor. When human symptoms started to be noticed around 1956 an investigation began. Fishing was officially banned in 1957. It was found that theChisso Corporation,apetrochemicalcompany and maker ofplasticssuch asvinyl chloride,had been discharging heavy metal waste into the sea for decades. They used mercury compounds as catalysts in their syntheses. It is believed that about 5,000 people were killed and perhaps 50,000 were to some extent poisoned by mercury. Mercury poisoningin Minamata, Japan, is now known asMinamata disease.

Seafood consumption benefits

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TheAmerican College of Obstetricians and Gynecologistsnoted that, considering all the dangers and benefits, the overall result of eating fish in the United States is likely to improve personal health rather than damage it.[18]The College argues that theomega-3 polyunsaturated fatty acidsfound in fish have a health benefit that outweighs the harm from mercury orpolychlorinated biphenyls.Even so, the College suggested limiting fish consumption for pregnant women. A risk-benefit study weighing the risks of mercury consumption against the benefits derived from fish in Alaska showed that the benefits outweigh the risks when consuming salmon for both cardiovascular health and infant neurological development, and that methyl mercury data for non-oily fish need to be of high quality before relative risk can be reliably identified. [35]TheSeychellesChild Development Study traced more than seven hundred mother-child pairs for nine years and found no neurological problems in the children resulting from both prenatal and postnatal methylmercury exposure. A study done with marketed fish inOmanconcluded that, except in a few rare cases, the fish available for consumption had lower levels of mercury than limits defined by various health organizations.[36]Some, citing these studies, have suggested the creation of place-based consumption advisories.[37]However place-based approaches do not take into account cases of severe mercury poisoning, such as that found inMinamata disease.

Seleniumis an element that is known to counteract some of the dangers of ingesting mercury.[30]Multiple studies have been done, such as those inNew JerseyandSweden,that take into account selenium as well as mercury levels. Fish often do contain selenium in conjunction with bioaccumulated mercury, which may offset some of the dangers associated with the mercury ingested.

Levels of contamination

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Most-contaminated fish species

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The danger level fromconsumingfish depends on species and size. Size is the best predictor of increased levels of accumulated mercury.Sharks,such as themako shark,have very high levels of mercury. A study onNew Jerseycoastal fishindicated that one third of the sampled fish had levels of mercury above 0.5parts per million,a level that could pose a human health concern forconsumerswho regularly eat this fish.[30]Another study of marketplace fish caught in waters surroundingSouthern Italyshowed that, undoubtedly, greater fish weight leads to additional mercury found in fish body tissues. Moreover, the concentration, measured inmilligramsof mercury perkilogramof fish, steadily increases with the size of the fish.Anglerfishoff the coast of Italy were found with concentrations as high as 2.2 milligrams of mercury per kilogram, higher than the recommended limit of 1 milligram of mercury per kilogram. Annually,Italycatches approximately a third of its fish from theAdriatic Sea,where these anglerfish were found.[38]

Fish that consume theirpreyin a certain manner may contain much higher concentrations of mercury than other species.Grass carpoff the coast of China hold far less internal mercury than dobighead carp.The reason for this is that bighead carp arefilter feeders,while grass carp are not. Thus, bighead carp gather more mercury by eating large amounts of small plankton, as well as sucking up sediments that collect a sizable amount of methyl mercury.[3]

Mercury levels in commercial fish and shellfish[a][b]
Species Median(ppm) Mean(ppm) Std dev(ppm) Trophic level Max age(years) Comment
Tilefish (Gulf of Mexico) — 1.123 — 3.6 35 Mid-Atlantic tilefish has lower mercury levels
and is considered safe to eat in moderation.[4]
Swordfish 0.870 0.995 0.539 4.5 15
Shark 0.811 0.979 0.626
Mackerel (king) — 0.730 — 4.5 14
Tuna (bigeye) 0.560 0.689 0.341 4.5 11 Fresh/frozen
Orange roughy 0.562 0.571 0.183 4.3 149
Marlin[c] 0.390 0.485 0.237 4.5
Mackerel (Spanish) — 0.454 — 4.5 5 Gulf of Mexico
Grouper 0.399 0.448 0.278 4.2 All species
Tuna 0.340 0.386 0.265 All species, fresh/frozen
Bluefish 0.305 0.368 0.221 4.5 9
Sablefish 0.265 0.361 0.241 3.8 94
Tuna (albacore) 0.360 0.358 0.138 4.3 9 Fresh/frozen
Tuna (yellowfin) 0.311 0.354 0.231 4.3 9 Fresh/frozen
Patagonian toothfish 0.303 0.354 0.299 4.0 50+[40] Chilean sea bass
Tuna (albacore) 0.338 0.350 0.128 4.3 9 Canned
Croaker white 0.280 0.287 0.069 3.4 Pacific
Halibut 0.188 0.241 0.225 4.3
Weakfish 0.157 0.235 0.216 3.8 17[41] Sea trout
Scorpionfish 0.181 0.233 0.139
Mackerel (Spanish) — 0.182 — 4.5 South Atlantic
Mahi-mahi 0.180 0.178 0.103
Bass 0.094 0.167 0.194 3.9 Striped,black,andblack sea
Snapper 0.113 0.166 0.244
Monkfish 0.139 0.161 0.095 4.5 25
Perch 0.146 0.150 0.112 4.0 Freshwater
Tuna (skipjack) 0.150 0.144 0.119 3.8 12 Fresh/frozen
Tilefish (Atlantic) 0.099 0.144 0.122 3.6 35
Skate — 0.137 —
Buffalofish 0.120 0.137 0.094
Tuna 0.077 0.126 0.134 All species, canned, light
Perch (ocean)[c] 0.102 0.121 0.125
Cod 0.066 0.111 0.152 3.9 22
Carp 0.134 0.110 0.099
Lobster (American) 0.086 0.107 0.076
Pickerel (American) 0.091 0.095 0.100
Lobster (spiny) 0.062 0.093 0.097
Sheephead (California) 0.080 0.090 0.050
Whitefish 0.067 0.089 0.084
Mackerel (chub) — 0.088 — 3.1 Pacific
Jacksmelt 0.050 0.081 0.103 3.1
Hake 0.067 0.079 0.064 4.0
Herring 0.042 0.078 0.128 3.2 21
Trout 0.025 0.071 0.141 Freshwater
Croaker (Atlantic) 0.061 0.065 0.050
Crab 0.050 0.065 0.096 Blue,kingandsnow crab
Butterfish — 0.058 — 3.5
Flatfish[c] 0.050 0.056 0.045 Flounder,plaiceandsole
Haddock 0.049 0.055 0.033 Atlantic
Whiting 0.052 0.051 0.030
Mackerel (Atlantic) — 0.050 —
Mullet 0.014 0.050 0.078
Shad (American) 0.033 0.038 0.045
Crayfish 0.035 0.032 0.012
Pollock 0.003 0.031 0.089
Squid 0.017 0.024 0.023
Catfish 0.005 0.024 0.056 3.9 24
Salmon[c] 0.015 0.022 0.034 Fresh/frozen
Anchovies 0.011 0.016 0.015 3.1
Salmon[c] 0.010 0.014 0.021 Canned
Sardine 0.010 0.013 0.015 2.7
Tilapia[c] 0.004 0.013 0.023
Oyster < 0.001 0.012 0.035
Clam[c] 0.002 0.009 0.011
Shrimp[c] 0.001 0.009 0.013 6.5[42]
Scallop < 0.001 0.003 0.007
  1. ^The mercury levels in the table, unless otherwise indicated, are taken from theUS FDA.[4]
  2. ^Trophic levels and maximum ages are, unless otherwise indicated, taken from the relevant species pages on Rainer Froese and Daniel Pauly (Eds) (2012).[39]Where a group has more than one species, the average of the principal commercial species is used.
  3. ^abcdefghOnly methylmercury was analyzed (all other results are for total mercury)

US government scientists tested fish in 291 streams around the country for mercury contamination. They found mercury in every fish tested, according to the study by theU.S. Department of the Interior.They found mercury even in fish of isolated rural waterways. Twenty-five percent of the fish tested had mercury levels above the safety levels determined by theU.S. Environmental Protection Agencyfor people who eat the fish regularly.[12]

Legislation

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Japan

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Since theMinamata disaster,Japanhas improved on itsmercuryregulation. During the 1970s Japan made strides to reduce mercury demand and production. Chief among these efforts was the reduction of inorganic mercury produced bymines.It was halted by 1974, and demand fell from 2,500 tons per year in 1964, its peak, to 10 tons per year in recent years.[43]Since these initial strides, Japan has introduced a list of regulations governing the mercury content of a variety of materials.

Japan Mercury Regulation[43]
Category Regulation Result
Cosmetics PharmaceuticalAffairs Act Ban the use of mercury and its compounds
Agriculture Agricultural Chemicals Control Act Ban the use of mercury and its compounds as an active ingredient
Household Commodities Act on Control of Household Products Containing Hazardous Substances No mercury in householdadhesives,householdpaints,householdwax,shoe polish,shoe cream,diapers,bibs,undergarments,gloves,andsocks
Pharmaceutical Products Pharmaceutical Affairs Act No use of mercury compounds in oral preparations. No use of mercury compounds, other thanmercurochrome,as an active ingredient. Mercury as a preservative only if no other option is available.
Air Air Pollution Control Law No more than 40 ng/m3
Water Basic Environment Law and Water Pollution Control Act Environmental quality standard: no more than 0.0005 mg/L inwaterwayandground water.Effluent standard: no more than 0.005 mg/L in effluence.
Soil Basic Environment Law and SoilContaminationCountermeasures Act Environmental quality standard: no more than 0.0005 mg/L sample solution.Elutionstandard: no more than 0.0005 mg/L. Content standard: no more than 15 mg/kg

Regulation of these potential sources of pollution reduces the amount of mercury that ends up infishand, throughbiomagnification,inhumans.In addition to enactinglegislationcontrolling the mercury levels in potential pollutants, Japan has directly influenced theenvironmentby issuing regulations setting acceptable levels of environmental mercurypollution.

It is Japan's goal to promote international mercury legislation in hopes of preventing any country from experiencing what it did.[43]Despite Japan's extensive regulation and experience with mercury-based disasters, there is still little information provided to the public. The Japanese Federal Fish Advisory's recommendations are less strict than those inAmerica.[44]

United States

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Fish advisory chart issued byU.S. Environmental Protection AgencyandFood and Drug Administration
Main article:Mercury regulation in the United States

Air pollution regulations

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The United States has regulated mercury emissions under the authority of theClean Air Act.

TheEnvironmental Protection Agency(EPA) first attempted to regulate power plant mercury emissions with theClean Air Mercury Rulein 2005.[45]TheGeorge W. Bush administrationintended for the regulation to use acap-and-tradesystem to control emissions across multiple industries. The rule was challenged in litigation, and in 2008 theU.S. Court of Appeals for the District of Columbia Circuitvacated the rule, stating that EPA had improperly excluded power plants from designation as emittinghazardous air pollutants.[46]

EPA subsequently classified mercury emissions from power plants as hazardous under section 112 of the Clean Air Act. The 2012Mercury and Air Toxics Standards(MATS) regulation, issued by theBarack Obama administration,targets airborne mercury emissions from power plants and other stationary sources.[47][48]Airborne mercury is dissolved in the oceans, wheremicroorganismsconvert waterborne mercury intomethyl mercury,which enters thefood chainand is stored in fish tissue.

EPA stated that the MATS regulation would prevent about 90% of power plant mercury.[48]The agency estimated the total expected health benefits are estimated at $37 billion–$90 billion by 2016.[citation needed]EPA estimated the economic cost at $9.6 billion annually.[citation needed].

In 2020 theTrump administrationweakened the MATS rule by disavowing EPA's previous calculations and justifications, thereby making the rule subject to legal challenges.[49]

Wastewater regulations

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EPA published wastewater regulations (effluent guidelines) for mercury in industrial categories where mercury is used in the manufacturing process, includingbatterymanufacturing;[50]inorganic chemicalsmanufacturing;[51]oil and gas extraction (drilling fluidsandcuttings);[52]and nonferrous metals manufacturing (smelting).[53]

European Union

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In EU, the regulation (EU) 2017/852[54]covers the full life cycle of mercury. This legislation prohibits the manufacture, export and import of a large range of mercury-added products; puts an end to all uses of mercury catalysts and large electrodes in industrial processes and reduces the use of and pollution from dental amalgam. Recently, the EU estimated the Mercury content in the topsoils based on a large Land Cover Survey named LUCAS.[55]The mercury content in EU topsoils has a median of 38 μg per Kg with a total content of around 45,000 tons[56]in the 0–20 cm of EU.

International

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Some believe that legislation on a global scale is needed for this issue because mercury pollution is estimated to be so far-reaching. Pollution from one country does not stay localized to that country. Despite this,international regulationhas been slow to take off. The first forms of international legislation appeared in the 1970s, beginning as agreements about shared bodies of water.[57]The next step was theStockholm Declaration,which urged countries to avoid polluting the oceans by dumping.[58]The 1972Oslo Conventionand the 1974Paris Conventionwere adopted by parts ofEurope.Both lessened polluting the ocean with mercury, the former by banning the dumping ofshipsandaircraftinto the ocean and the latter by obligating participants to reduce land-based pollution on coastlines.[59][60]The first real global legislation regarding mercury pollution was theBasel Conventionof 1989. This convention attempts to reduce the movement of mercury across borders and primarily regulates theimportandexportoftoxicchemicals, including mercury.[57]In 1998 the Convention on Long-Range Transboundary Air Pollution was adopted by most of theEuropean Union,the United States, andCanada.Its primary objective is to cut emissions ofheavy metals.The convention is the largest international agreement on mercury established to date.[57]In the early 21st century, the focus of mercury regulation has been on voluntary programs.[57]The next phase in legislation is a global effort, and this appears to be what the Minamata Convention hopes to accomplish. TheMinamata Convention,named after the Japanese city that suffered horribly from mercury pollution, has taken four years of negotiation but was finally adopted by delegates from over 140 countries. The convention was ratified after 50 countries signed it. The Minamata Convention requires all participants to eliminate, where possible, the release of mercury from small-scalegold mining.It also requires a sharp reduction in emission fromcoalburning.[61]

Current advice

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The complexities associated with mercury transport and environmental fate are described by USEPA in their 1997 Mercury Study Report to Congress.[62]Because methyl mercury and high levels of elemental mercury can be particularly toxic to a fetus or young children, organizations such as theU.S. EPAand FDA recommend that women who are pregnant or plan to become pregnant within the next one or two years, as well as young children, avoid eating more than 6 ounces (170g, one average meal) offishper week.[63]

In the United States, the FDA has an action level for methylmercury in commercial marine and freshwater fish that is 1.0 parts per million (ppm). In Canada, the limit for the total of mercury content is 0.5 ppm. TheGot Mercury?website includes a calculator for determining mercury levels in fish.[64]

Species with characteristically low levels of mercury includeshrimp,tilapia,salmon,pollock,andcatfish(FDA March 2004). The FDA characterizes shrimp, catfish, pollock, salmon,sardines,and canned light tuna as low-mercury seafood, although recent tests have indicated that up to 6 percent of canned light tuna may contain high levels.[65]A study published in 2008 found that mercury distribution in tuna meat is inversely related to the lipid content, suggesting that the lipid concentration within edible tuna tissues has a diluting effect on mercury content.[66]These findings suggest that choosing to consume a type of tuna that has a higher natural fat content may help reduce the amount of mercury intake, compared to consuming tuna with a low fat content. Also, many of the fish chosen forsushicontain high levels of mercury.[67]

According to theUS Food and Drug Administration(FDA), the risk from mercury by eating fish and shellfish is not a health concern for most people.[68]However, certain seafood might contain levels of mercury that may cause harm to an unborn baby (and especially its brain development and nervous system). In a young child, high levels of mercury can interfere with the development of the nervous system. The FDA provides three recommendations for young children, pregnant women, and women of child-bearing age:

  1. Do not eatshark,swordfish,king mackerel,ortilefish(Gulf of Mexico) because they might contain high levels of mercury.
  2. Eat up to 12 ounces (2 average meals of 170 g each) a week of a variety of fish andshellfishthat are lower in mercury. Five of the most commonly eaten fish and shellfish that are low in mercury are:shrimp,canned light tuna,salmon,pollock,andcatfish.Another commonly eaten fish,albacoreor ( "white" ) tuna depending on its origin might have more mercury than canned light tuna. So, when choosing your two meals of fish and shellfish, it is recommended that you should not eat more than up to 6 ounces (one average meal) of albacore tuna per week.
  3. Check local advisories about the safety of fish caught by family and friends in your local lakes, rivers, and coastal areas. If no advice is available, eat up to 6 ounces (one average meal of 170 g) per week of fish you catch from local waters, but consume no other fish during that week.

Research suggests that selenium content in fish is protective against the toxic effects of methylmercury content.[69]Fish with higher ratios of selenium to methylmercury (Se:Hg) are better to eat since the selenium binds to the methylmercury allowing it to pass through the body un-absorbed.

In 2012 theEuropean Food Safety Authority(EFSA) reported on chemical contaminants they found in the food of over 20 European countries. They established that fish meat and fish products were primarily responsible for methylmercury in the diet of all age classes. Particularly implicated were swordfish, tuna, cod, pike, whiting and hake. The EFSA recommend a tolerable weekly intake for methylmercury of 1.3 μg/kg body weight.[70]

See also

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References

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