The most common toxins or contaminants in the marine environment are dioxins, dioxin-like PCB’s, heavy metals like mercury and cadmium and flame retardants. Most of these substances got into the environment through industry, although some of them occur in a minor amount in nature too. A lot of studies about the impact of these toxins on human health have already been carried out. The problem is that, due to practical issues, often only the impact of a single toxin or a single group of toxins is considered and not the impact of the interactions of these substances. Toxicologists advise to investigate the effects of the combinations of different contaminants (toxins) on human health, as we know almost nothing about that.
During their lifetime, people take up a lot of dioxins. About 95% – 98% of them enters the human body through food consumption. Most dioxins are found in animal products and especially in fish. The biggest problem of dioxins is their high chemical stability. Once taken up, dioxins nestle themselves in the living organism and stay there for a long time. They got built up in the food chain, so how further up in the chain, the higher the concentration of dioxins. Pregnant women and newborn babies are the most vulnerable category of people. In contrast to what is claimed regularly, pregnant women have to be discouraged to eat fat fish. In the current European Directive about inter alia the maximum amount of dioxins a person may eat, can be found that mainly fish contains a lot of toxic dioxins: twenty times more then meat and milk and ten times more then eggs.
Mainly fat fish contains much more toxins than whitefish or fish down in the food chain. These are often carcinogen substances that can cause cancer by frequent consumption for a long time. A research conducted at the University of Ghent (2008) revealed that about 50% of all PCB’s, dioxins and dioxin-like PCB’s in our body comes from fish and other seafood, although they count for only 1%-2% of all the food we eat. According to the Netherlands Nutrition Center Foundation, the Belgian study is not correct and from all dioxins in the food of a Dutch person “only” 12% should come from fish.
Although for most of the toxins the measured amounts in fish are under the limits implemented by Europe, almost no studies have been carried out on the effects of the combined toxins often present in fish. The fatter the fish, the more toxins it contains. Reason is that a lot of these toxins are lipophilic: they nestle themselves in the fat tissues. The position in the food chain also determines how toxic a fish can be. Predator fishes, like tuna, swordfish and shark, contain more toxins than small fishes at the base of the food chain. Yet, it is often said that eating fatty fish is important for the fatty acids it contains. But fish do not make these Omega-3 fatty acids themselves. They take it up with their food and gills while breathing. It comes from unicellular plankton algae containing these Omega-3 fatty acids. Already of lot of these algae are being farmed for their derivatives of Omega-3 (EPA and DHA), so it is not necessary to eat fish to get these fatty acids. Besides, a lot of other plant based products contain the mother form of Omega-3, alpha linolenic acid (ALA), too, like purslane, walnuts, linseed (-oil) and rape seed (-oil).
- Winkel, Dos (red). 2010. De Huilende Zee. Elmar Uitgeverij.