Sometime ago, I wrote about arsenic being deliberately added to chicken feed and the harm it did to the human body. There is, however, another food source in which arsenic is usually found in large quantities — seafood.
Arsenic is an odourless, tasteless element which is used in wood preservatives, fertilizers, animal feed, and other industrial and agricultural applications. Like lead, mercury, and other heavy metals, arsenic can persist in soil for years after it is applied to crops.
Arsenic is found in two forms: organic, which is considered less harmful, and inorganic, which is considered very harmful. The key organic arsenic compounds that can be routinely found in food include monomethylarsonic acid (MMAsV), Dimethylearsonic acid (DMAsV), arsenobetaine, arsenocholine, arsenosugars, and arsenolipids.
Seafood and seafood products contain high levels of arsenic compounds. The chemical element is mainly found as arsenobetaine. DMAsV or MMAsV can be found in various types of finfish, crabs, and molluscs. Arsenocholine, which is mainly found in shrimp, is chemically similar to arsenobetaine.
Arsenosugars and arsenolipids have recently been identified in marine molluscs. The current biological exposure index in the US (of 35 microgram per litre total urine arsenic concentration) may easily be exceeded by a healthy person eating a seafood meal. In Indians there are no standards, but our marine life contains far more arsenic than is safe to eat.
Arsenic is present in all seafood, but there are higher amounts in bivalves (clams, oysters, scallops, mussels), crustaceans (crabs, lobsters), and cold water and bottom feeding finfish and seaweed/kelp, especially Hijiki seaweed which is the most commonly used in Japanese/Chinese food.
Arsenobetaine is considered nontoxic because it is organic. But then so was arsenic in the form of Roxarsone given to chickens to make them get fatter faster and look redder. It was proven in 2011 to be deadly because it changed from organic to inorganic (which is toxic) in the chicken’s body and got even more toxic when it was cooked.
Calcium, and other supplements made from seafood, may also contain high amounts of arsenic.
Concerns about the adverse effects of chronic arsenic exposure have focused on contaminated drinking water and airborne workplace exposures; the risks of naturally-occurring arsenic in foods have received less attention. About 90 percent of the arsenic in US diets comes from seafood. This has not been taken seriously as it was considered that only a small proportion occurs in inorganic forms. However, recent studies of seafood have documented that this arsenic becomes carcinogenic in rodents. Borak and Hosgood have analysed the risk of seafood arsenic on humans and found it substantial.
Research done by analytical chemists at the University of Graz in Austria found that certain forms of arsenic, which appear in seafood and are thought to be harmless, might actually be toxic. Even more troubling, the researchers found that while arsenic mostly passes right through some people, it lingers inside others for an extended period.
Francesconi and colleagues at the university created organic arsenic that they fed to six volunteers. The researchers had originally wanted to test 50 people, but medical ethics concerns limited the size of the study. Over the next four days, testing of urine and blood showed that four of the six participants excreted into their urine at least 85 percent and as much as 95 percent of the arsenic they ingested, with most of it coming out in the first day. Of the remaining two volunteers, one excreted just 15 percent, and the other eliminated less than 4 percent of the arsenic she had swallowed.
What happened to the non-excreted arsenic? Obviously, it was being stored by the body — and that is not good news. Two out of six people is a very high percentage.
Results also showed that, over the course of digestion, the synthetic organic arsenic broke down into potentially toxic forms. This finding raises new concerns about levels of organic arsenic in seafood.
At very high levels, arsenic can be fatal. At lower levels, arsenic can cause nausea and vomiting and decrease the amount of red and white blood cells produced by the body. It causes abnormal heart rhythms, may damage blood vessels, and causes a pins and needles sensation in the hands and feet.
What happens to people when they are exposed to low levels of arsenic over a long period of time? Arsenic is associated with skin, bladder, and lung cancers, says Johns Hopkins Bloomberg School of Public Health in Baltimore. Chronic low-level poisoning leads to heart disease, lung damage and breathing problems. Long-term exposure to arsenic causes skin discoloration that looks like freckles, or small moles, on the hands, feet, or trunk.
Skin lesions start about ten years after first exposure. White lines appear on the nails, and pigmentation on the arms and upper chest. This is accompanied by hair fall, conjunctivitis, corneal ulceration. There is also an increased risk of diabetes.
For children and pregnant women, the risks are heightened. “The more we learn about arsenic’s additional effects on the developing brain, the more concerned I am. Getting exposed to a toxicant like arsenic in-utero, or during early childhood, can cause damage that may not appear until decades later,” says Michael Waalkes, at the Division of the National Toxicology Program. He is one of the authors of a June 2012 report, funded in part by the National Institutes of Health, that concluded that early life exposure to arsenic produces a wide range of cancers and other diseases.
In a recent study, published in the Journal of Trace Elements in Medicine and Biology, the scientists focused on arsenic in seafood. Thirty eight healthy young men and women, between 20-40 in age, were selected to eat 150 grams of salmon, cod, or mussels, for 14 days. Another group ate 150 grams of potatoes. Before and after this eating regimen, the subjects had blood samples taken in order to measure arsenic, iodine and selenium – all chemicals indicative of thyroid activity. Included in the blood analysis were the enzymes that reflect the exact levels of thyroid activity.
After 14 days of seafood consumption, the subjects had a 20-60 percent rise in arsenic levels in their bodies. And the increased arsenic in the plasma did, in fact, cause hikes in thyroid activity as well as TSH levels.
Arsenic not only is a potent human carcinogen but it can set up children for other health problems in later life. The Environmental Protection Agency assumes there is actually no “safe” level of exposure to inorganic arsenic. WHO considers arsenic as one of the ten major public health concerns. It is ranked by the International Agency for Research on Cancer (IARC) as one of more than 100 substances that are Group 1 carcinogens. Two forms of organic arsenic, called DMA and MMA, found in seafood, have also been labelled by the same agency as “possibly carcinogenic to humans”.
A study has been done by Lorenzana, Yeow, Colman, Chappell and Choudhary on what percent of inorganic arsenic exists in seafood round the world. This is their finding: “…the data from the worldwide literature indicate the percent of inorganic arsenic in marine/estuarine finfish does not exceed 7.3 percent and in shellfish can reach 25 percent in organisms from uncontaminated areas. However, percentages can be much higher in organisms from contaminated areas and in seaweed. For freshwater finfish, the average percent inorganic arsenic is generally 10 percent, but ranges up to nearly 30 percent.”
Should you be worried about the fish, shellfish and seaweed you eat? Yes. But in India neither the