bioaccumulation and biomagnifications Marine organisms absorb and cannot excrete some toxins and heavy metals that enter the oceans from pollutants. These toxins accumulate in a fish’s body as it eats other fish, this is known as "bioaccumulation," the toxins travel through the food web from prey to predator, continuing to increase in concentration in a process called "biomagnification."At the top of the food chain are the ‘apex’ predators: sharks.Some shark species can live for 50 years or more, consuming many toxin-laden fish and storing those toxins in their bodies throughout their lifetime. No creature in the oceans comes higher in the food chain, if some sharks are prey, it is to other bigger sharks.
BMAA The consumption of shark linked to Brain diseases. BMAA, is a neurotoxin linked to neurodegenerative diseases in humans including Alzheimer's and Parkinson’s disease. A new study by University of Miami scientists has discovered high concentrations of BMAA within the flesh, cartilage and organs of sharks. The cyanobacterial neurotoxin β-N-methylamino-L-alanine (BMAA), is produced by virtually every known species of cyanobacteria, a ubiquitous algae-like microbe present in freshwater and saltwater worldwide. The study suggests that the toxin can accumulate up the food chain, increasing in concentration as one animal eats another. That is worrisome because sharks, like humans, are apex predators, and if BMAA can accumulate in shark tissues, the same could possibly happen in humans. “We could be exposed to BMAA over our life span, and it could accumulate in our tissues as well,” according to Dr. Mash, professor of neurology and of molecular and cellular pharmacology.
When they measured BMAA in the organs and muscles of sharks killed as a result of recreational fishing activities, BMAA was detected in kidney, liver, muscle and cartilage. The prized delicacy shark fin soup, and other products from shark parts are therefore a great link to BMAA consumption. BMAA bio-accumulates making the risk of these toxins great when shark products are consumed more than once. The study suggests that consumption of shark derivatives may pose a significant health risk for degenerative brain diseases.
“When I see a bowl of shark fins, I see a bowl of toxins”
ORGANIC POLLUTION TOXINS
As apex predators positioned at the top of the marine food chain, sharks are highly exposed to toxic compounds like lead, cadmium, and many persistent organic pollutants (POPs) including DDT and PCBs.
DDT – a synthetic pesticide
DDT is a toxicant; Subsequently banned for agricultural use worldwide, but is still used to a limited extent in mosquito control in certain parts of the world. DDT and its metabolic products DDE and DDD magnify through the food chain. DDT bio-concentrates significantly in fish and other aquatic species, leading to long-term exposure to high concentrations. People exposed to high levels of DDT exhibit dizziness, tremor, irritability, and convulsions. Long-term exposure can lead to lasting neurological and cognitive problems. Pregnant women exposed to DDT are more likely to have premature babies.
Prevalent in great whites and other species:
“Additionally, young great white shark “pups” caught in their nursery grounds off the Southern California coast were found to contain levels of harmful contaminants of PCBs and DDTs in their liver tissue. It was the highest observed in any shark species reported to date globally.”
Ashley Blacow, OCEANA society
PCBs (polychlorinated biphenyls)
PCB’s are used as coolants/insulating fluids, also used in flexible PVC coatings of electrical wiring and electronic components, pesticide extenders, cutting oils, flame retardants, hydraulic fluids, sealants (used in caulking, etc), adhesives, wood floor finishes, paints, and in carbonless copy paper. PCBs are very stable compounds and do not degrade readily. Despite being banned in the 1970s due to their high toxicity, PCBs still persist in the environment. PCBs have been detected globally in the atmosphere, from the most urbanized areas that are the centers for PCB pollution, to regions north of the Arctic Circle, carried by wind currents and it bio-concentrates in animals.
In humans, PCBs can cause liver disease, ocular lesions, and lessened immune response. Babies born to women exposed to PCBs have been shown to weigh less, have problems with motor skills, a decrease in short-term memory, and compromised immune systems. PCBs alter estrogen levels in the body and contribute to reproduction problems. Endocrine Disrupting Chemicals (EDC's) such as PCBs pose a serious threat to reproduction in top-level predators. Children with greater exposure to PCBs have suffered with body and brain development. Studies suggest PCBs are also toxic to the immune system, reproductive organs, and thyroid. Recent research by the National Toxicology Program has confirmed that PCB126 is a carcinogen.
The EPA (Environments protection agency) lists DDT and PCBs as a probable human carcinogen, which causes cancer.
PCB’s were found in shark meat in the Italian environment:
“In the fat of shark species Prionace glauca and Rapias vulpinus collected during 1992 in the south Adriatic sea areas non-ortho PCBs were found.”
Source: Selected persistent organic pollutants (POPs) in the Italian environment, United Nations Environmental Programme. Stockholm Convention on Persistent Organic Pollutants (POPs). )
Health Canada tests on fish oils found the highest levels of DDT, PCBs and other contaminants in shark oil.
(Health Canada- www.hc-sc.gc.ca)
MERCURY AND METHYL MERCURY
As well as containing mercury, sharks contain Methyl mercury which is a much more toxic compound that forms when mercury binds with organic molecules in the environment. This usually happens when mercury is released into the atmosphere through burning and settles into wetlands or streams, where it can be taken up by aquatic life.
The dangerous effects of mercury poisoning are loss of motor control, involuntary spasms and seizures, corrosion of skin and mucous membranes, blindness, deafness, premature birth or loss of fetus’s, birth defects, spinal problems, impotence, sterility, and it is linked with various illnesses and cancers such as Hodgkin’s Lymphoma, Parkinson’s disease, and Alzheimer’s disease to name a few.
“Between 1953 and 1965 over a hundred adult men and women developed symptoms of central nervous system disorders such as ataxia, alterations in gait, tremors, altered sight and sensation. Methyl Mercury can easily work its way through all safety barriers of the human body. Something that most other poisons cannot do as easily. In the last 30 years Minamata Disease has claimed at least 3,000 lives, mostly through consumption of fish, poisoned with methyl-mercury. There are probably a lot more deaths that could be contributed to methyl-mercury but the testing methods have never been as accurate as the one, which has now been developed in Germany.”
Source: The German organization Sharkproject, study by Prof. Dr. Heumann 20th, 2005.(http://www.sharkprotect.com/en-health)
2004 EPA and FDA Advice For: Women Who Might Become Pregnant Women Who are Pregnant Nursing Mothers Young Children.3 recommendations for selecting and eating fish:
First Recommendation: Do not eat Shark, Swordfish, King Mackerel, or Tilefish because they contain high levels of mercury.
Environmental Defense Fund. (in the case of shark meat)
Due to elevated mercury levels we recommend:
Women should not eat at all
Men should eat no more than 1 meal per month
Kids up to age 12 should not eat at all
Healthy eating in pregnancy fact sheet: Foods to limit .
To minimise the intake of mercury during pregnancy, various types of fish with higher levels of mercury should be limited to: shark (flake) and billfish (broadbill, swordfish and marlin), 1 serve (150g) per fortnight and no other fish that fortnight.
Organizations throughout the world, including the United States Environmental Protection Agency (USEPA), the World Health Organization (WHO) and the Food and Agriculture Organization of the United Nations (FAO), recognize mercury to be a dangerous neurotoxin and warn against eating shark, especially pregnant women, women who plan to become pregnant, or children.Methyl mercury exposure can cause serious neurological and heart problems and has been linked to infertility. One quarter of 70 uncooked fins from a Hong Kong market contained mercury concentrations well above the World Health Organization’s guidelines, enough to be identified as a significant threat to children and babies. Methyl mercury is most dangerous for the human body.
Toxicologist Dr. Hermann Kruse of the University of Kiel (Germany) explains why: "methyl mercury is a "Trojan horse" which can pass easily through each protection barrier and the separation mechanism between the blood circulation of a mother and her unborn child as well as the blood-brain barrier of each adult. Consequences of such a poisoning are forms of infant mental development disturbances and for an adult even damage to the central nervous system. These express themselves by headache, memory difficulties or depressions, kidney damages, cancer and massive damages of the
Inorganic mercury is converted into biologically active methyl-mercury by microbes that live on the bottom of the ocean. It is then concentrated in the bodies of fish, where it never dissolves. Since sharks eat a lot of fish in their relatively long life span, they carry a very highly concentrated amount of methyl-mercury in their bodies, which also does not dissolve during their very long lifetime.
Methyl Mercury: dangerously close
.These toxins are not confined to shark fin soup. Prof. Dr. Klaus Heumann from the University in Mainz, German, and the inventor of the newly patented method of analysis, has found an alarming concentration of up to 1,400 micro grams of methyl-mercury in one kilogram of blue shark steak. That means that a normal portion of 250 grams could contain 350 micrograms of the deadly poison.
Note: RfD (oral reference dose): RfD is an estimate daily oral exposure of a chemical to the human population (including sensitive subpopulations) that is likely to be without risk of deleterious noncancer effects during a lifetime.
The RfD for methyl mercury is 0.0001 mg/kg/d based on developmental neurologic abnormalities in human infants.
OVER THE LIMIT: An insight into Methyl Mercury consumption
The legal limit, set by the toxicology department of the EPA for methyl mercury, is 0.1 micrograms per kilogram of body weight.
1,400 micro grams in one kilogram of blue shark steak (1.4 per gram)
That means that a normal portion of 250 grams could contain 350 micrograms of the deadly poison.
A human weight: 70kg.
70 x 0.1 micrograms (recommended intake daily)= 7 micrograms per day for my body.
250g serving of blue shark = 350 micrograms (1.4 micrograms per gram)
A blue shark steak of 250g contains 350mg of methyl mercury – 343 mg over the legal limit in one dose.
4 servings in 60-80 days, (60-80 days to leave the body) =350mg X 4 = 1,400mg
It has been estimated that the minimum lethal dose of methyl mercury for a 70-kg person ranges from 20 to 60 mg/kg. 1,400mg divided by 70kg= 20mg per kg
70 days is 10 weeks- or 2 and a half months, 4 servings of 250 gram portions of blue shark in this time would give each kg of body weight 20mg of methyl mercury- the minimum lethal dose of methyl mercury for a 70-kg person.
A 500g serving of blue shark for a 70kg person would be a quarter of the minimum lethal dose.
High doses of methyl mercury over a short time period cause a more severe, sometimes irreversible damage to the human organism than lower doses over a long period of time.
This was just for blue shark: Methyl mercury is present in any top food chain predator: Blue Shark: Prionace glauca Status: Near Threatened – listed under the species woolworths is able to sell under the name ‘blacktip shark’. Seafood Services Australia (source).
Queensland Health:“It is caused by eating warm water ocean finfish that carry ciguatera poison (a toxin). This poison is produced by a very tiny organism called a dinoflagellate, which attaches itself to algae growing in warm ocean water reef areas. Small plant-eating fish eat this toxic algae and in turn are eaten by larger predatory fish which are eaten by humans.”
Ciguatera is a type of sea food poisoning caused by the consumption of fish, especially certain tropical reef fish, which contain one or more naturally occurring neurotoxins from the family of ciguatoxins and maititoxins. It has also been suggested that ciguatera may be caused by occupational exposure to ciguatoxic fish organs during repetitive handling or processing of fish. Ciguatoxins are odourless, tasteless and generally undetectable by any simple test. Therefore, bioassays have traditionally been used to monitor suspected fish. Ciguatera is reported to be the most common form of sea food poisoning in the world, with the estimated number of cases ranging from 50,000 to 1,000,000 annually. In view of the fact that only 2% - 10% of ciguatera cases are actually reported, and many doctors have never heard of ciguatera, it is clear that the true prevalence of this disorder could be much greater than these figures suggest. Although ciguatera is often considered to be a mild non fatal disease, it has a world wide mortality rate ranging between 0.1% - 12% with isolated outbreaks as high as 20%.
Paraesthesias in extremities and around mouth including numbness,
Temperature reversal where hot feels cold and vice versa.
Pain on urination
Abdominal cramping C
Sudden blood pressure spikes
Dermatitis, itch, rash, aches and pains, arthralgia, myalgia, general weakness, salivation, breathing problems, dyspnea, neck stiffness, headache, ataxia, exhaustion, fatigue, sweating, depression, and metallic taste in the mouth. Ciguatera, it should be noted, may also be sexually transmitted and may cause premature labour or spontaneous abortion. Ciguatoxins may also be transmitted via breast milk
Ciguatera toxins or ciguatoxins, are said to be amongst the deadliest mammalian poisons known, reportedly being, volume for volume, 1000 times more potent than arsenic. These heat stable toxins originate from a type of micro-organism which attaches to certain species of algae on dead or damaged coral in tropical areas around the world. Increasing damage to coral reefs therefore correlates with an increasing frequency of ciguatera outbreaks.
SHARKS POTENTIALL CONTAINING CIGUETERA ARE CAUGHT IN THE GBR LEGAL SHARK FISHERY AND FED TO AUSTRALIANS
Three of these different species of fish are banned from sale if caught in Queensland due to the present risk of the ciguatera toxin in them. These fish are reef fish occurring in tropical Queensland & therefore are part of the prey of sharks captured by the ECIFF, and therefore continue to carry the toxins in the food chain to the point where it becomes available to humans. TWO of the species of shark listed as potentially containing the cigueter toxing on 'fish base' website, are two species on the list of available sharks at woolworths.