Mercury Articles
Good
Neighbor?
Mercury Fears. February 13, 2005
Mercury Threat. January 2, 2005
Mercury In Soil. August 15, 2004
Is Salmon Safe to Eat? June 27, 2004
Good
Neighbor?
Safeway, the nation’s fifth largest food store, has posted warnings about mercury at their seafood counters: First in California as required by regulators then, apparently, nationwide as a public service.
The notice says that pregnant women, women of childbearing age, nursing mothers and young children should avoid eating large predator fish such as swordfish, king mackerel, shark and tilefish. It also suggests that these people should limit their intake of Albacore Tuna to 6 oz per week.
But are these notices helping or hurting people?
A recent Harvard Medical School study, published in the October issue of Environmental Health Perspectives, suggests that the admonitions from the U.S. Food and Drug Administration, on which the Safeway warnings are modeled, may have the unintended consequence of “depriving fetuses of essential nutrients found in fish”.
The study indicates that depriving babies of fish may be hurting their neurocognitive development.
The warning by Safeway may also result in people not eating fresh water fish. A recent publication by the Mackinac Center shows that mercury concentrations in Great Lakes region bald eagle feathers fell approximately 20% between 1985 and 2000. Bald eagles are at the top of the food chain where their primary diet is fish: It can be concluded that there has been a corresponding reduction of mercury in fish in the Great Lakes region.
There has long been a debate over whether mercury, in the amounts normally found in fish, actually has a negative effect on the cognitive development of children. The TSAugust article originally published February 13, 2005, and republished this month in Worth A Second Look on the Home Page, provides details about mercury, methyl mercury and any possible health risks.
Blanket
warnings, such as those published by Safeway, can do more harm than good.
Finding the right balance between risk and benefit is challenging; but
learning more about mercury in fish and avoiding scare stories can benefit
pregnant women and children. The benefits available from eating fish warrant
learning fact from fiction.
Mercury Fears.
Mercury in fish gets considerable media attention without providing information that would allow American’s to asses the danger of eating fish or for deciding which actions the government should take in this matter.
There are three categories of information that weigh on this issue.
They are (1) the determination of where mercury originates together with the quantities involved, (2) how, and to what extent, mercury is transformed into methyl mercury, the form of mercury ingested by fish, and (3) what levels of methyl mercury form a health risk.
Mercury emissions:
World wide mercury emissions are estimated at 5,000 to 5,500 tons/year with natural emissions half the worldwide total depending on volcanic activity. The US generates 117 tons/year (40 tons/yr from power plants).
Volcanic emissions are unpredictable but average around 700 tons/yr worldwide. There are over 5,000 surface and submarine volcanoes in the world with over 50 eruptions each month that can cause worldwide emissions to spike in any single year.
With respect to natural emissions in the U.S.: Roaming Mountain Wyoming researchers established that mercury emanating from a clay hillside were over 250 times as high as background levels away from geothermal areas. The Idaho National Engineering and Environmental Lab issued a report in 2004 that Yellowstone Park could emit as much mercury as all of Wyoming's eight coal burning power plants. Illinois researchers have demonstrated that coal fired power generation could account for only a fraction of the mercury in the soil, indicating that most of the mercury in the soil was present before coal was used for generating electricity.
Methyl Mercury:
Another confounding factor is how methyl mercury, the type of mercury that is ingested by fish, is created and destroyed. Recent studies have indicated that 72.5% of methyl mercury is created within Chesapeake Bay itself, while 20% is from rivers feeding into the bay and only 7.5% is from atmospheric deposition of mercury.
Deep sea fish caught in the Western Atlantic between the 1880’s and the 1970’s have shown little change in the amount of methyl mercury in their tissues. This could indicate that methyl mercury in fish isn’t likely to be affected by changes in mercury emissions. Fish that live in deep areas of the ocean would not have been exposed to atmospheric deposition or estuarine mercury and presumably ingested methyl mercury from natural sources.
There were also no differences in mercury levels of Yellowfin tuna between 1971 and 1998; increases would have been expected from increased mercury emissions. Also, there were no increases in mercury between 1970 and 2000 for striped bass caught in the San Francisco Bay area, though there were reductions in DDT and chlordane levels.
It appears as though SO2 in the water helps to form methyl mercury but much about the formation of methyl mercury is not known.
Health Risks:
And finally, what levels of methyl mercury in the blood denote a health risk.
The following chart shows key measurements: The EPA’s Reference Dose (RfD) at 5.8 ppb, compared with the World Health Organizations 83 ppb; the point at which WHO believes there is a health risk. Also shown is the Bench Mark Dose Lower Limit (BMDL) used by the EPA to establish the RfD. The level of mercury for mothers diagnosed with Minamata disease in the 1950’s is shown, where there was real health damage from mercury discharged by a chemical factory into the bay next to the Japanese city of Minamata.
Also shown is a graph of the levels of Hg found in 1,709 women in the U.S. of child bearing age tested for Hg, with 92% of these women having mercury levels falling below the RfD.
There is a serious question whether the RfD accurately reflects the point at which mercury levels indicate a health risk and whether establishing the RfD at such a low level is actually harming people by discouraging them from eating fish.
The BMDL was set so that there was 95% confidence that there would be no health risks from mercury at that level (58 ppb). The RfD was set at one tenth (10%) of the BMDL, to establish a further factor of safety.
In addition the BMDL was set based on the Faroe Island study of children whose mothers ate whale blubber (not fish). The recent Seychelles Island study of children, whose mothers ate fish, shows no negative neurological effect.
The
considerable negative publicity surrounding mercury and fish has
led a number of people to complain that health warnings based on
the RfD are causing harm. Typical of these comments is that of
John Middaugh, State Epidemiologist of Alaska, who recently warned
the FDA:
“Advisories based upon risk assessment without consideration of well-established public health benefits of fish consumption have great potential to harm public health if reductions in fish consumption occur.”
Middaugh reported that many native Alaskan communities abandoned traditional fish diets since the FDA’s 2001 mercury advisory, with a subsequent increase in diabetes, heart disease, and vitamin A and D deficiencies.
Sources for this article include comments on EPA’s Docket ID No. OAR-2002-0056, by the Center for Science and Public Policy, December 2004; and a study by the AEI-Brookings Joint Center for Regulatory Studies, September 2004.
February 13, 2005
Mercury Threat.
It would appear as though the dramatic reduction in mercury emissions from U.S. sources has already greatly lessened any threat from methyl mercury in fish caught in the U.S.: Though scare stories to the contrary abound.
The large unknown is how much the mercury from Asia will affect Americans. Much of Asian mercury will settle in the oceans, which is bound to exacerbate the mercury levels in fish such as Tuna.
A recent report by the AEI-Brookings Center for Regulatory Studies concludes that there is little threat to Americans, women and children included, from the mercury being emitted by US utilities.
Mercury emitted by Asian utilities may represent a greater threat: By one estimate, China alone emits 600 mt of mercury annually and this could double as China increases its generation of electricity using coal.
Total U.S. mercury emissions have been reduced from around 375 million tons (mt) in 1989 to around 117 mt in 1999, of which around 48 mt were from utilities. It would appear as though total U.S. mercury emissions have fallen from around 800 mt in 1980. Further, it is estimated that mercury emissions from U.S. utilities today are around 40 mt.
The extent to which methyl mercury actually affects Americans is unclear. The most recent study would indicate that Americans are largely unaffected by mercury at current levels.
A study of children in the Seychelles showed no harm from mercury exposures several times greater than relatively highly exposed Americans. The earlier Faroe Islands study seemed to show some neurological effect from eating whale blubber; but associations of “mercury with reductions in other specific tests (e.g. finger tapping, recall of names) or in more general tests of cognitive performance required either higher mercury doses or did not occur at any dose”. (Americans don’t eat whale blubber.)
The EPA’s reference dose RfD is set based on the Faroe Islands study and incorporates several safety factors; it also fails to consider that the Seychelles study would indicate little if any threat from mercury found in America’s fresh water fish.
(The
RfD is a daily intake of a chemical that EPA estimates is
“likely to be without appreciable risk of deleterious effects
in a lifetime.”)
In addition to these factors (i.e., dramatic reduction in U.S. mercury emissions, the Seychelles study and the extremely conservative RfD) the mercury emitted by utilities must be converted to methyl mercury in the land or water before it can be ingested by fish and ultimately humans. It would appear as though only half the mercury is transformed into methyl mercury and that SO2 helps the conversion: Reducing SO2 will reduce the formation of methyl mercury.
This would indicate that cutting back on SO2 emissions could have a greater effect on eliminating methyl mercury in fish than would further reductions in mercury emissions from U.S. utilities, as SO2 affects mercury from all sources.
The AEI-Brookings study examines why there is little risk to women or children from eating fresh water fish. The RfD is set “so as to protect the most sensitive individuals from even the most subtle effects” “The RfD is also intended to protect a developing fetus from harm”.
While
8% of women in childbearing age have mercury levels that exceed
the RfD, the study examines why even this group has little risk.
In essence, the RfD is set so low that the vast majority of
people who exceed the RfD by as much as two or three times will
incur little if any risk. The benchmark dose lower limit (BMDL),
which is the point at which some observable effects from methyl
mercury might be detected, is ten times the RfD.
The study also shows that cutting back on mercury emissions in the U.S. has no effect on mercury levels in fish caught in the ocean, such as Tuna, and establishes world wide mercury emissions at 5,000 to 5,500 tons per year.
The AEI-Brookings study does not address the effect of Asian mercury emissions on Americans or whether U.S. resources could be better utilized by assisting Asian nations with the technology that can reduce their mercury emissions rather than narrowly focusing on regulating mercury emissions (that are already at low levels) from U.S. utilities.
(See the complete report, "A Regulatory Analysis of EPA's Proposed Rule to Reduce Mercury Emissions from Utility Boilers," AEI-Brookings Joint Center for Regulatory Studies, September 2004. http://aei-brookings.org/admin/authorpdfs/page.php?id=1044)
January 2, 2005
Mercury In Soil.
High mercury levels in the soil may not be from power plant emissions.
A recent study published in Hydrology and Earth System Science by E.C. Krug and D. Winstanley of the Illinois State Water Survey indicates that the amount of mercury in the soil is so great, relatively speaking, that it could not all have been deposited by burning coal.
The approach used to test the hypothesis about the anthropogenic source of mercury in the soil, was to compare rates of atmospheric deposition of mercury with the mercury content of the soil, while assuming 100% retention of deposited mercury in the soil.
The results showed that it would take several hundred years of emissions from power plants for the soil to accumulate the amount of mercury now found in the soil; obviously this is impossible since power plants burning coal have only been in existence for little over one century. The study compared soils in Illinois and for the USA under various scenarios.
The report also referenced earlier studies dating back to 1975 and 1979 that also concluded that mercury in soils came mainly from non anthropogenic sources. These earlier studies estimated that anthropogenic activities could only have increased mercury in the soil by .02%. (Wallest et al 1975, Andren and Nrigu 1979).
These
studies discredit the assumption that mercury in soils was
naturally low and that mercury in soils came primarily from
power plants.
In addition, these studies raise serious issues concerning methyl mercury in fresh water fish, the states prohibitions on eating fresh water fish and the urgency of regulating mercury emissions from power plants.
As
of 2002, 43 states had warned residents to limit how much
freshwater fish they consume, restrictions that encompass 30
percent of the nation's lakes and 13 percent of its rivers.
The EPA has just conducted the first ever nationwide survey of fresh water fish over a four year period sampling 2,547 fish from 260 lakes; three quarters of these fish may have had mercury levels that some would claim as being unhealthy.
Jim Pendergast, Chief of the EPA Office of Science and Technology Health Protection and Modeling branch, said that the EPA had not yet set a safe limit for fresh water fish and that mercury levels outlined in the survey should not be a problem.
Is it possible that fresh water fish have always contained significant levels of mercury? And, if so, what light does this shed on the prohibitions on eating fresh water fish promulgated by many states?
Will reducing mercury emissions from power plants have any meaningful impact on the amount of methyl mercury found in fresh water fish?
These
are serious questions deserving serous attention.
Source:
Comparison of mercury in atmospheric deposition and in
Is
Salmon Safe to Eat?
Recent reports by various environmental organizations (PIRG, EWP, PEW) have claimed that salmon and other fish are unsafe to eat. Farm raised salmon were singled out as having unsafe levels of PCB’s.
The Washington Post for example said.“A sharp rise in the consumption of farmed salmon may be posing a health threat to millions of Americans because of high levels of PCB’s…”
Two studies, one Easton et al and the other by the Environmental Working Group (EWG), were the basis for these misleading media stories. Both studies are flawed and misrepresented the facts. The more recent PEW study is covered below.
Dr.
Santerre,
-
The sample size of 8 fish (4 farmed, 4 wild) and 5 feeds was so small that it was statistically meaningless. In addition the samples were taken from grocery stores with no documentation of their point of origin; were they actually farm or wild?
-
The report attempted to make the numbers look larger than they actually were by using parts per trillion rather than the widely accepted parts per billion. 50,000 ppt amounts to .05 ppm, where ppm is used as the standard reference by most regulatory bodies.
-
The measures of tolerable daily intake (TDI) and toxic equivalent (TEQ) measurements were inflated. These measurements in the study, for example, were based on lipid concentration rather than fish weight, where lipid content is about 10% of fish weight, thereby inflating the TDI and TEQ numbers by about 10 times.
The EWG study had similar flaws.
-
The sample size of 10 fish from a local grocery store was touted as the “most extensive test to date of cancer causing PCB’s in farmed fish”. Again, the sample size was statistically meaningless.
-
Misleading results. The EWG claimed that “seven of the ten fish were so contaminated with PCB’s that they raise cancer risk concerns…” In fact the average test results of 27 ppb of PCB’s found in the sample of ten fish were 98.5 % below the tolerance level of 2000 ppb (2.0 ppm) set by the US Food and Drug Administration.
The EPA has an unusually restrictive standard saying that people should restrict their intake to one fish meal per month when the PCB level is 24 – 48 ppb. This sets the standard at a level where the EPA feels certain there is no increase in risk over a 70 year life span.
Many have noted that such a restrictive standard deprives Americans of the great benefits derived from eating fish.
The
American Heart Association calculates that about 250,000
Americans die from heart attacks each year and that a modest
increase in daily consumption of fish could drastically reduce
this toll. A recent, still preliminary study of elderly, by
researchers at
Then another study published in January 2004 by PEW, Global Assessment of Organic Contaminants in Farmed Salmon, also warned that people should limit their intake of salmon.
Dr Santerre disagreed with the PEW study’s conclusion. He said, "The study demonstrates that farmed salmon is very low in contaminants and meets or exceeds standards established by the Food and Drug Administration and the World Health Organization," Santerre said, "The study also shows that the cancer risk from eating large amounts of salmon is significantly lower than the risk of developing heart disease from not eating generous amounts of the fish."
“Santerre recommends farm-raised or wild salmon for pregnant and nursing mothers as an ideal source of nutrients for a developing fetus and infant. He also says salmon is one of the safest fish on the market.”
Hg Emissions Lower in U.S.
Mercury emissions in the U.S. have been cut nearly in half since 1995, having been reduced from 77 tons in 1995 to around 40 tons today.
In
1995 emissions in China were 495 tons,
More importantly, while Hg emissions in the U.S. were being significantly cut they were increasing in most parts of the world except Europe.
Confounding proposed legislation is that most Hg comes from natural, not anthropogenic sources, with 55% of Hg occurring naturally.
Also
U.S. utilities represent only 1% of total worldwide Hg sources. Hg
emissions are transported around the world so there is a serious
question whether reducing U.S. emissions will have any effect on the amount of Hg found in
fish. In addition only .03% (three one hundredths of a percent)
of Hg from U.S. local emissions are converted to methyl mercury
(MeHg), the type
of mercury that can affect human health.
These
confounding factors are at the core of the debate over how
drastically to regulate Hg emissions. EPA has itself indicated
that, no matter how strictly Hg from coal fired power plants is
regulated, it is not possible to meet regulatory standards. By
one estimate, the strictest regulations will only reduce total
deposition of Hg by around 3%.
Then
there is the debate over whether Hg actually causes harm to
humans in the quantities that Americans ingest as MeHg through
the consumption of fish. The Seychelles studies indicate there is little if any risk while the
Faroe Island studies are the basis for claiming there is risk.
Commentary
published in The Lancet on the
On
balance, the existing evidence suggests that methyl mercury
exposure from fish consumption during pregnancy, of the level
seen in most parts of the world, does not have measurable
cognitive or behavioral effects in later childhood…For now,
there is no reason for pregnant women to reduce fish consumption
below current levels, which are probably safe.
These
are some of the facts that need to be considered before reaching
conclusions on how to regulate mercury.
(See
the Center
for Science and Public Policy, www.scienceandpolicy.org, for
more information.)
Hg False Alarms.
There is no scientific evidence that cutting mercury emissions from US power plants will reduce mercury in fish. Recent hype by the Sierra Club, Friends of the Earth and the National Wildlife Federation have attempted to scare Americans into believing that eating Tuna and other high food chain fish will cause learning disabilities and harm people’s health.
Some
55% of Mercury emissions occur naturally. Another 42%come
from outside the
With so much mercury coming from outside the U.S. it is no wonder that mercury levels in Pacific tuna have remained the same.
But, does mercury in fish cause harm?
As
reported by the Wall Street Journal, “The gold standard in
mercury research is a
The alarmists refer to a study of Faroe Island children that has been discredited for not having a statistical correlation of test results and because the mothers consumed other toxins such as DDT.
The following quote puts the issue in perspective.
“We
do not believe that there is presently good scientific evidence
that moderate fish consumption is harmful to the fetus.
However, fish is an important source of protein in many
countries and large numbers of mothers round the world rely on
fish for proper nutrition. Good maternal nutrition is essential
to the baby’s health. Additionally, there is increasing
evidence that the nutrients in fish are important for brain
development and perhaps for cardiac and brain function in older
individuals”.
– Dr. Gary Meyers,
(Pediatric Neurologist, University
of
It would appear that the health warnings from the alarmists may be doing a lot more more harm than good.
More
detailed information can be obtained from the Center for
Science and Public Policy (www.scienceandpolicy.org).
Copyright © 2002 - 2006 TSAugust