This Fish Contains Mercury (And So Do You)
Source: El País – Este pez tiene mercurio (y usted)
This Fish Contains Mercury (And So Do You)
The contamination of seafood calls into question recommendations of regular consumption – everyday compounds can affect cognitive development and the reproductive system
MÓNICA G. SALOMONE, December 19, 2010
Scientists confirm a decrease in contaminants like lead in the environment. They are most worried about fish and shellfish because the concentrations of compounds inside them are not decreasing.
“Of all the animals, the one that has the most contaminants in its body is you,” says Nicolás Olea, of the University of Granada, one of Spain’s pioneers in investigating the presence of contaminants in organisms. The statement sounds like it was made for dramatic effect, but the message is clear: during their long lives, humans accumulate persistent chemical compounds that season our diet, contaminants that our own industrial activity has generated. And they stay there, in an organism that doesn’t know how to eliminate them. What’s more, they’ve entered the human race to stay. Mothers transmit them through the placenta and their breast milk, and their babies incorporate them as well. What effect do they have? There is growing evidence that many affect us from cognitive development to fertility, even at low doses.
It’s already been some time since we knew the toxicity of many of these compounds, and for example in the case of dioxins, poly-chlorinated biphenyl (PCB), or heavy metals, their industrial use or release into the environment has been regulated. But that doesn’t mean they’ve vanished from the natural world. They are in the food chain, entrenched most of all in the animals we eat; the older and fattier those animals are, the more contaminated. Predatory fish, like the shark or the swordfish, can ingest methyl-mercury, the most toxic form of mercury, for over ten years before arriving on a dinner plate.
In addition, there are more modern compounds that are very commonly used in daily life, like phthalates – used in soft plastics, for example infants’ toys; bromidic compounds – put in fabrics and computers to resist fires; or Bisphenol A, whose effects on health are worrying.
Ecological organizations and experts have sounded the alarm for some time, with some results. The European Commission announced last week that from 2011, feeding bottles may not contain Bisphenol A, a ruling the United States already made a year ago. John Dalli, European commissioner of heath, announced that “new studies demonstrated that Bisphenol A could affect development, immune response, and the generation of tumors.” In contact with hot liquids, this compound separates from plastic, especially if the bottles are not new. For Olea, the prohibition “is fantastic news, but why have we waited this long? We’ve known how this compound acted since 1936.”
Exactly how many compounds do we eat? José Luis Domingo, of the Laboratory of Toxology and Environmental Health at the Rovira i Virgili University, and Joan María Llobet, of the University of Barcelona, have analyzed the contents of the average grocery basket in Catalonia since 2000. Their third report was just released. They took data about the average food purchases of consumers, analyzed the quantity of eight heavy metals in that food, then crossed the data to estimate the daily chemical ingestion of the average Catalonian.
There is some good news: “There has been a decrease of certain contaminants in the environment, such as lead (which is no longer used in gasoline), dioxins, and PCB,” says Domingo. Llobet points out that “that which we emit to the environment comes back to us; if the environment is cleaner, so is our food.”
The black mark above all is fish and shellfish, in which chemical concentrations are not low. Although average ingestion of each compound is below the maximum level established by the World Health Organization (WHO), the 2007 study published by the Catalonian Agency of Food Security (ACSA) reveals that children surpass that standard a little, and women practically meet it. The report repeats EU recommendations that small children, pregnant woman, those who wish to conceive, and those who are nursing children should not eat more than 100 grams of swordfish or shark weekly, assuming no other fish are eaten that week. Tuna should be eaten no more than twice a week. Europe is not the only place to give such advice; the U.S. and Canada have made similar announcements over the years.
The data of ACSA’s studies fits well with the majority of the alerts made by the Spanish Agency of Food Security in 2009 over the high levels of mercury in fish. It’s logical. Once it’s in the environment, mercury doesn’t disappear. And natural sources of mercury, like volcanic eruptions, add to the activity of humans, who have used the metal for more than 3500 years. It’s estimated that we release 50,000 metric tons of mercury into the environment every year.
“We will never remove mercury from the food chain,” says Bernardo Herradón, chemist of the Superior Council of Scientific Investigations (CSIC). “It’s been used a lot, and though it’s now very restricted, it persists in some types of batteries and florescent light bulbs, for example.” Mercury is in the soil and also the atmosphere; rain sends it to rivers and from there to the sea, where microorganisms convert it to methyl-mercury, which is the form in which we eat it through our fish. Microorganisms are at the base of the marine food chain, and the great predatory fish, as well as ourselves, are at the top.
But in addition to diet, the researches are discovering – “to their surprise,” says Olea – another source of chemical contaminants: cosmetics. “The effect of the components of creams and shampoos is now an area of vigorous research. We have more and more evidence that compounds very commonly used in cosmetics, like parabens, interfere with the action of hormones. They are easily absorbed through the skin, but their elimination is very difficult,” explains Olea.
UV filters, used in sunscreen and recommended by dermatologists to prevent skin cancer, are becoming suspect. In confirming its toxic action, the biomedical community would encounter a cost-benefit dilemma.
Without a doubt, the researchers say that it will not be easy to
establish beyond all doubt the connection between daily exposure to contaminants and illnesses. To begin with, the effects, as they are, take decades to manifest. Also, the important thing, according to researchers, is the “cocktail” of chemical products; that is, their action together. There are many compounds, and their possible interaction is a mystery.
“We don’t know what will happen, but the data is there,” says Olea. “The exposure is real. The toxins are in the blood and placenta, and they are excreted in maternal milk. Mothers pass them to children. We have compounds in our body compounds that we’ve never had before,” says Olea.
Epidemiologists, for the moment, are investigating the relationship between exposure to contaminants and ailments like cancer, diabetes, endometriosis, infertility, genital-urinary malformations, immunological depression, asthma, Alzheimer’s, and Parkinson’s.
This type of work requires a treasure trove of tissue and data like that possessed by the Olea group in Granada: 6000 placentas from mothers all over Spain obtained a decade ago, with information collected from mother and child ever since. This permits investigation, for example, into the relationship between contaminants in the placenta and physical development. One of the latest scientific studies published, in September, indicates that the majority of chlorinate compounds could negatively affect cognitive function and recommends more studies.
The researchers have also recently observed that the low concentration of these compounds does not guarantee an organism’s safety. The so-called “myth of low dosage” is being dispelled.
“In animals as well as humans, we have seen adverse effects from contaminants at doses traditionally labeled low,” explains Miquel Porta, chair of Epidemiology and Public Health at the University of Barcelona and researcher for the Municipal Institute of Medical Investigations (IMIM). “Strictly speaking, these doses are not really low: the concentrations or levels in blood or amniotic liquid, for example, are as high as those of our own natural hormones, and often much more.” Until now, it has been accepted that these compounds had to be present in more elevated doses to alter physiological functions in organisms, but “this is under review,” says Porta.
It does not reassure this expert to know that in the majority of food, these compounds do not surpass the levels considered safe by governmental agencies and the WHO. “Often these legal levels are established simply by the quality of what commonly arrives on our tables,” indicates Porta. “But no one can assure us that these concentrations consumed by a large part of the population are safe; for me, as a doctor, that is very worrisome.”
In a recent study, a group measured the presence of contaminants in a group of 919 people in Catalonia who were considered representative of the general population. The results revealed that some people had levels of DDE (which proceeds from the breakdown of DDT) and hexachlorobenzene up to 6000 times higher than those of others. “A minority of the population has internal contamination scandalously higher than most. Does that minority later develop illness?” wonders Porta.
It’s one of many ongoing topics for study. The researchers ask, for example, how environmental toxins interfere with the activity of genes. Some data indicate that arsenic, cadmium, and organochloride pesticides could turn off genes that suppress tumors and turn on genes that do precisely the opposite.
More proof of the importance of this problem is that the European Union has assigned funds to investigate it. The Olea group and seven other European laboratories participate in the international project Contamed, which studies the relationship between everyday chemicals and disturbances in the reproductive system. The incidence of such alterations – from the lower quality of semen to malformation of genitals – is increasing in Europe, and that problem causes “considerable worry,” says the project’s web site.