Mercury & dioxins in fish
- From: Enrico C <use_replyto_address@xxxxxxxxxxxxx>
- Date: Tue, 7 Nov 2006 20:21:28 +0100
Here is a paper from the European Food Safety Authority (EFSA) on the
safety and nutritional contribution of wild and farmed fish.
As far as I understand, high consumption of contaminated fish, like top
predatory fish or Baltic fish, might be a risk especially for foetal
development and young children. Women going to have a baby should take
care.
What about adult males? Is there a risk for men as well?
http://www.efsa.europa.eu/en/press_room/press_release/2005/1017.html
===
EFSA provides advice on the safety and nutritional contribution of wild and
farmed fish
Last updated: 8 July 2005 Publication Date: 4 July 2005
The European Food Safety Authority (EFSA) has published an opinion on the
health risks related to the consumption of wild and farmed fish.
Press release
EFSA provides advice on the safety and nutritional contribution of wild and
farmed fish
The European Food Safety Authority (EFSA) has published an opinion on the
health risks related to the consumption of wild and farmed fish. EFSA’s
Opinion says that there are no consistent differences between wild and
farmed fish both in terms of safety and nutritional value *. Consumption of
fish, and in particular fatty fish due to its richness in long chain n-3
polyunsaturated fatty acids, is beneficial to cardiovascular health and
also to foetal development. In general, dietary recommendations suggest
weekly consumption of one to two portions of fatty fish. The greatest
susceptibility to the critical contaminants, methylmercury and dioxin-like
compounds, occurs during early human development. Scientific experts
therefore advise that - in particular for vulnerable groups such as the
unborn child, pregnant women and women of child-bearing age - the
nutritional benefits of fish should be weighed against the potential risks
related to the presence of contaminants in certain types of fish. Overall,
nutritional guidelines concerning fish consumption will not lead to intakes
of dioxins and dioxin-like PCBs which cause safety concern, with the
exception of fatty fish caught from the Baltic sea (e.g. herring and
salmon) where the available data concerning contaminant levels support the
more specific recommendations established by Swedish and Finnish food
safety authorities ** . The Panel notes however that advice regarding fish
consumption should also take into account other sources of these
contaminants in the diet. With respect to methylmercury, women eating up to
two portions of fish per week are unlikely to exceed tolerable intake
levels provided that certain types of top predatory fish are avoided.
Additional guidance regarding the types and quantities of fish most suited
to consumers’ diets is provided by national food safety authorities in
Member States. Finally, the EFSA Panel on Contaminants in the Food Chain
recommends the development of a consistent and agreed methodology for
carrying out quantitative assessments of risks and benefits related to food
consumption.
EFSA was asked by the European Parliament to assess the health risks
related to human consumption of wild and farmed fish and to include an
overall impact and risk assessment related to the consumption of Baltic
herring. EFSA’s advice concentrates on the most relevant heavy metals and
persistent organic contaminants, namely methylmercury *** , dioxins ****
and dioxin-like PCBs ***** and also reviews the nutritional value and
benefits from consuming fish. In order to carry out this assessment
requiring multi-disciplinary expertise, EFSA established an Inter-panel
working group consisting of members from the following Scientific Panels:
Contaminants in the Food Chain (CONTAM); Dietetic Products, Nutrition and
Allergies (NDA); Additives and Products or Substances used in Animal Feed
(FEEDAP); and Animal Health and Animal Welfare (AHAW).
Fish makes an important nutritional contribution to the diet, providing
proteins, fatty acids (such as long-chain n-3 polyunsaturated fatty acids -
LC n-3 PUFAs) and certain vitamins and minerals. Consumption of fish is
beneficial to cardiovascular health and may also benefit development of the
unborn child. Dietary recommendations often advise one to 2 portions (130g
per portion) of “fatty fish” (such as herring and salmon) per week, or
greater amounts of lean fish, in order to achieve intake levels of LC n-3
PUFA favourable to the cardiovascular system.
In assessing the safety of wild and farmed fish, EFSA’s CONTAM Panel
reviewed a wide range of contaminants and concluded that the two
contaminants for which high consumers of fish might exceed the provisional
tolerable weekly intake (PTWI) are:
(i) methylmercury which is found at elevated concentrations in tuna and
other top predatory fish which are mostly caught in the wild, and
(ii) dioxins and dioxin-like PCBs for which higher levels are found in
fatty fish, e.g. herring and salmon.
Methylmercury is particularly toxic to the nervous system and the
developing brain. Exposure during pregnancy and early infancy is therefore
of particular concern. Pregnant women eating up to two portions of fish per
week are unlikely to exceed provisional tolerable weekly intake (PTWI)
levels for methylmercury, as long as they do not consume blue fin or
albacore tuna. (These species are not likely to be found in canned tuna in
Europe). Other top predatory fish, such as marlin, pike, swordfish, and
shark also frequently contain high levels of methylmercury. EFSA already
recommended in March 2004 ****** that women of childbearing age (in
particular, those intending to become pregnant), pregnant and breastfeeding
women, as well as young children, select fish from a wide range of species
without giving undue preference to top predatory fish, such as swordfish
and tuna.
For dioxins and dioxin-like PCBs, it would take several years to reduce
levels in the human body. It is therefore not possible for women wishing to
become pregnant to reduce these levels without excluding fish (as well as
other possible food sources of dioxins and dioxin-like PCBs) from their
diets completely for several years before conception. However, women
consuming up to two portions per week of fatty fish will not exceed the
provisional tolerable weekly intake for dioxins and dioxin-like PCBs
provided that they take into account other possible sources in the diet so
as not to exceed the PTWI.
According to EFSA’s Opinion frequent consumers of fatty fish coming from
the Baltic Sea, i.e. Baltic herring and wild Baltic salmon are more likely
to exceed the PTWI for dioxins and dioxin-like PCBs than other consumers of
fatty fish. On average, Baltic herring and wild Baltic salmon are
respectively 3.5 and 5 times more contaminated with dioxin and dioxin-like
PCBs in comparison with non-Baltic herring and farmed salmon. Specific
advice concerning Baltic fish consumption, taking into account these higher
contamination levels, is given by national food safety authorities in
Sweden and Finland2.
Advice on fish consumption needs to take into account total dietary
exposure of relevant contaminants, based on national consumption patterns.
Guidance regarding the types and quantities of fish most suited to
consumers’ diets is provided by national food safety authorities in Member
States. Factors which affect the levels of contaminants found in fish
include: species; life stage and fish’s diet; season; and location of
catch. These levels vary broadly within species and between species in both
wild and farmed fish. Based on the data available, there are no consistent
differences between nutrient and contamination levels of wild and farmed
fish. In farmed fish, fish oil and fish meal are the most important sources
of organic contaminants and possibilities for reducing contaminants levels
in fish feed should be further explored. For wild fish the only action
possible is the long-term control of emissions of pollutants to the
environment.
Fish, whether wild or farmed, has its place in a well balanced diet and
overall there is no consistent difference between wild and farmed fish with
respect to their safety for the consumer.
For additional information on the CONTAM Panel’s Opinion on the Safety of
Wild and Farmed Fish, see the background note attached.
The full text of the opinion.
For media enquiries, please contact:
Alun Jones, Press Officer
Tel: + 32 2 337 2487
E-mail: Alun.Jones@xxxxxxxxxxx
or
Anne-Laure Gassin, EFSA Communications Director
Tel : + 32 2 337 2248
GSM: + 32 (0)473 301 968
E-mail: Anne-Laure.Gassin@xxxxxxxxxxx
For further information about the European Food Safety Authority:
http://www.efsa.eu.int
__________________________________________
* This assessment is based on available data but there is a need for
further development in the standardization of sampling methods in order to
improve comparisons between wild and farmed fish.
** For Finland: www.nfa.fi and for Sweden:
http://www.slv.se/templates/SLV_Page____11374.aspx
*** Methylmercury (MeHg) is the predominant form of mercury in fish and is
the most toxic form of mercury from the diet for
human health. It occurs primarily as a result of microbial activity on the
mercury present in the sea.
**** “Dioxins” can be divided into 2 principles types: PCDDs
(polychlorinated dibenzo-p-dioxins) and (PCDFs) polychlorinated
dibenzo-p-furans.
***** Dioxin-like PCBs are polychlorinated biphenyls (PCBs), which have the
same mode of action as dioxins.
****** http://www.efsa.eu.int/press_room/press_release/258_en.html
__________
Background note on EFSA risk assessment related to the safety of wild and
farmed fish (Request N° EFSA- Q-2004-23)
1. What types of fish were considered by EFSA in its risk assessment?
In carrying out its risk assessment, the Scientific Panel on Contaminants
in the Food Chain focused on the principal fish species found in the
European Union (EU) market: herring, salmon, tuna, rainbow trout, carp,
anchovies, mackerels and pilchards.
2. Is it healthy to eat fish?
Fish makes an important contribution to an overall healthy diet by
providing protein, fatty acids (such as long chain n-3 polyunsaturated
fatty acids, LC n-3 PUFAs) and certain vitamins and minerals (vitamins A,
B12 and D, iodine and selenium). Substantial dietary intake of LC n-3
polyunsaturated fatty acids can be obtained readily by eating fatty fish or
larger amounts of lean fish. Therefore individuals who eat no fish will
have difficulties in meeting the daily intakes of LC n-3 PUFA recommended
with regard to cardiovascular health and foetal development.
However fish can also contribute significantly to the dietary exposure to
contaminants such as methylmercury, dioxins and PCBs, brominated flame
retardants, camphechlor and organotin compounds. Concentrations of these
contaminants in fish vary with the nature of the contaminant and the type
of fish. Fat soluble contaminants (such as dioxins and dioxin-like
compounds) are especially found in fatty fish, e.g. salmon and herring. In
contrast, methymercury levels are not related to the fat content of the
fish but due to its accumulation in the food chain, methylmercury is
present in higher amounts in large predatory fish (such as swordfish and
tuna).
High consumers of top predatory fish such as pike or tuna (especially
bluefin or albacore tuna, not likely to be found in canned tuna in Europe)
may exceed the provisionally tolerable weekly intake (PTWI) for
methylmercury. High consumers of fatty fish may exceed the PTWI for dioxins
and dioxin-like compounds.
But it should also be kept in mind that there exist other dietary sources
for the fat soluble contaminants. Consumers who have high meat intakes may
also exceed the PTWI for dioxins (PCDD/F) and dioxin-like compounds,
regardless of their level of fish consumption. Therefore replacing fish
with meat will not inevitably lead to decreased dietary exposure to these
contaminants.
Intakes of contaminants in fish other than methylmercury and dioxins and
PCBs, are not a health concern. Fish do not contribute significantly to
total dietary exposure to these contaminants, and where it does, it is
unlikely that even high consumers of fish exceed the tolerable intake
levels (where these have been established).
3. Should I be eating fish leading up to or during pregnancy
Methylmercury is particularly toxic to the nervous system and the
developing brain. Exposure during pregnancy and early infancy is therefore
of particular concern. Methylmercury is removed from the body naturally but
it takes about several months for the levels to fall. Canned tuna seems to
have lower levels of methylmercury than fresh tuna due to different species
and/or size of fish used.
Pregnant women eating up to two portions/week fish are unlikely to exceed
the PTWI for methylmercury provided that one of these portions is not
bluefin or albacore tuna. Such species are not likely to be found in canned
tuna marketed in the EU. Other top predatory fish such as marlin, pike,
swordfish and shark frequently contain high levels of methylmercury. More
specific dietary recommendations regarding fish consumption are given by
national food safety authorities in Member States.
Dioxins and dioxin-like compounds affect in particular the developing male
reproductive system; therefore exposure of the unborn child through the
mother during pregnancy is the most critical period. Dioxins and
dioxin-like compounds accumulate in the body’s fatty tissue and have very
long half-lives which means that it takes many years for the body to clear
these chemicals. Consequently the level found in the body or “body burden”
during pregnancy is not determined by the dioxin intake at that time but by
the accumulation of all previous intakes over many years.
Fatty fish such as salmon and herring contain higher levels of contaminants
such as dioxins and dioxin-like compounds than lean fish.
Pregnant women eating up to two portions per week of fatty fish such as
non-Baltic herring or salmon will not exceed tolerable intake values (i.e.
the PTWI) for dioxin and dioxin-like compounds, although other sources of
dietary exposure need to be taken into account.
In previous advice issued in March 2004, EFSA recommended that women of
childbearing age (in particular, those intending to become pregnant),
pregnant and breastfeeding women as well as young children select fish from
a wide range of species without giving undue preference to top predatory
fish such as swordfish and tuna.
http://www.efsa.eu.int/press_room/press_release/258_en.html. This advice is
still valid and should be taken into account in selecting the one or two
portions of fish a week which are considered to contribute to a healthy
diet. Further and more specific dietary advice regarding fish consumption
is provided by national food safety authorities in Member States.
4. Why is Baltic fish getting special attention?
The Baltic Sea is heavily contaminated by a number of pollutants, e.g.
dioxins and PCBs. Whilst the reason for this is not fully elucidated, it is
thought that industrial activities of the past together with the long
retention time of the water could be important factors. Contamination
levels have declined in Baltic fish over the past three decades but no
further decrease is seen today. On average levels of dioxin and dioxin-like
compounds in Baltic herring is about 3.5 times higher than in non Baltic
herring. Wild Baltic salmon is about 5 times more contaminated with dioxin
and dioxin-like compounds than farmed salmon.
As a result there is a greater potential to exceed the provisional
tolerable weekly intake (PTWI) if people eat herring or wild salmon from
the Baltic sea more than once a week. Specific national advice is given,
notably in Sweden and Finland, and particularly for girls. This is due to
the fact that dioxins and dioxin-like compounds are stored in the body for
a long time with consequences on the levels found in a woman’s body during
pregnancy and in breast milk (for those women choosing to breastfeed).
5. Which fish are farmed
While EU fish catches have declined, fish consumption has increased by at
least 1% per year during the last ten years. The increasing consumer demand
for fish has been met mainly by greater availability of farmed fish both
from the EU and imported. Fish caught from the wild represent however about
two-thirds of total fish consumed. Examples of fish which are predominantly
or exclusively farmed are salmon, rainbow trout and carp. Fish caught from
the wild include herring, anchovies, tuna mackerels and pilchards.
6. Is consumption of farmed fish less safe than wild fish?
There are no consistent differences between wild and farmed fish both in
terms of safety and nutritional contribution. (An exception is Baltic
salmon where farmed Baltic salmon is less contaminated than that caught
from the wild). Species, season, location, diet, lifestage and age all have
a major impact on both the nutrient and contaminant levels of fish. These
levels vary broadly within species and between species in both wild and
farmed fish.
7. Is European fish more contaminated than North American fish?
In a scientific paper published about one year ago and a follow-up paper of
the same authors published in May this year (Hites et.al., 2004 Foran
et.al., 2005) the authors indeed suggested that North American salmon was
less contaminated than European salmon. However, the authors did not take
into account the seasonal, location, and fish’s diet, lifestage and age
factors which vary widely. When taking these factors into account no
consistent differences in contaminant levels could be observed between
European and North American fish, including salmon.
References:
Hites R.A., Foran J.A., Carpenter D.O., Hamilton M.C., Knuth B.A., Schwager
S.J. (2004).
Global Assessment of Organic Contaminants in Farmed Salmon Science, 303:
226-229.
http://www.nal.usda.gov/fnic/foodcomp/search/
Foran J.A., Carpenter D.O., Hamilton M.C., Knuth B.A., Schwager S. J.
(2005). Risk-based consumption advice for farmed Atlantic and wild Pacific
salmon contaminated with dioxins and dioxin-like compounds. Environmental
health perspectives 113: 552-556.
===
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