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Environmental toxins and you

Picture the world from space at night. Points of light show where humans live. They also show where most environmental toxins are: right where humans are. But toxins spread, too: outward to remote areas, borne by ocean currents and wind; and inward into your own body. Did you know they were there?

Figure Therese Fram Forum_english_650x267.jpg

A)Grossly simplified, the graph shows how PBC production, emissions to the environment and concentrations in humans are correlated. As concentrations in the environment rise and fall, the concentrations in humans follow after a time lag.B)Food is currently our main source of environmental toxins. High intake of an environmental toxin gives increasing concentrations in the body. When intake is reduced, the amount in the body will also decrease over time. 

By Linda Hanssen and Therese Haugdahl Nøst // NILU – Norwegian Institute for Air Research

Picture the world from space at night. Points of light show where humans live. They also show where most environmental toxins are: right where humans are. But toxins spread, too: outward to remote areas, borne by ocean currents and wind; and inward into your own body. Did you know they were there?

All humans carry environmental toxins in their body. Some carry more, some less, depending on how old they are, where they live, what they eat, and many other factors. But what is an environmental toxin? The precise scientific term, “persistent organic pollutant” (POP), gives a better description of what it is all about. Environmental toxins are persistent and if they degrade at all in the environment, they do so slowly. Organic environmental toxins are man-made and can have harmful effects on the environment and in humans. They also bioaccumulate, which means that the concentration of toxins increases the further up the food chain you go.

Where do environmental toxins come from? Some are formed as by-products of industrial processes (dioxins), others are synthesised on purpose (pesticides), and others were invented by accident (perfluorinated organic compounds) before being put to use in industry.

The group of environmental toxins that has been most in focus over the years is polychlorinated biphenyls (PCBs). PCBs were first synthesised in the 1930s and quickly became popular because their properties made them ideal for use in a number of industrial applications, for example in paint, plastics and electrical transformers.

Emissions to the environment through production and use led to the PCBs ending up in the food chain. These substances have an affinity for fat (we say they are lipophilic), and since the marine food chain contains a great deal of lipids, the PCB concentrations in marine mammals, oily fish and birds’ eggs have been high. International agreements restricting or even prohibiting the production and use of PCBs have resulted in a decrease in concentrations of PCBs in the environment and in humans.

According to Miljostatus.no, “PCBs can weaken the immune system, which increases susceptibility to infection and disease. Different PCB compounds can damage the nervous system, cause cancer of the liver and reduce fertility. Foetuses and infants are most sensitive to the effects. PCBs have a negative impact on humans’ learning ability and development.” Other effects have also been indicated in studies of human populations exposed to low doses, although the effects are often unclear.

Effect studies require data on exposure

To be able to study the effects of environmental toxins on humans, we need to have good knowledge of human exposure to them. There is no clear connection between the concentration of PCB in blood and its effect on the body. There are several reasons for this. Most epidemiological studies have measured the content of PCB in the blood at one particular point in time. But the group studied may have consisted of both old and young, women and men – individuals, each with a unique personal history, and whose bodies may contain completely different amounts of PCB. Conclusions have thus been drawn from that point in time, but time is also an important factor.

PCB emissions have risen and then fallen again over time, and the concentrations of PCBs in the environment and in humans have done the same. As long as PCB intake is high, the concentrations will increase in the body, but if emissions are low and human intake goes down, the concentrations in an individual will fall over time. This conclusion is supported by model calculations based on emissions and measurements of concentrations in blood. Thus, time is an important parameter for assessing exposure and evaluating effects.

A person’s lifetime exposure to environmental toxins depends on when he or she was born in relation to peak emissions. Let’s use PCBs as an example: a baby born in 1940 was exposed to lower concentrations before birth than a baby born in 1980, when emissions were at their peak. Now, in 2016, the total amount of PCBs may be higher in the individual born in 1940 (who has lived forty years longer) but the baby from 1980 had higher prenatal exposure to environmental toxins than the baby from 1940. To be able to understand the effects, we must take into account the emissions that lie behind human exposure.

We know that the foetus is exposed to environmental toxins through its mother during pregnancy, as these toxins have been found in blood from the umbilical cord and in the newborn’s first stool. In addition, lipophilic environmental toxins like PCBs are present in human breastmilk. So individuals are exposed from very early in life. (Just to be absolutely clear, we recommend breastfeeding nonetheless, as breastmilk contains many other valuable nutritional substances that are important for the child!)

So why are we still so concerned about PCBs, when their new use has not been permitted since the 1980s? In Norway, although PCB-containing products and waste have been collected for several years now, there are still an estimated 100 tonnes of PCBs in products and buildings in Norway (http://www.miljostatus.no/PCB). And PCB is just one in the multitude of chemicals we have all around us. But since so much research has been done on PCBs, we can use our knowledge about their environmental fate and human exposure when studying other environmental toxins. The fact that human exposure to PCBs is so closely correlated with emissions is important, and is probably also true for other substances. In recent years, researchers working on environmental toxins have been interested in cocktails – and we don’t mean fancy drinks. We mean toxic cocktails – the mixture of chemicals our blood contains. There are indications that environmental toxins can influence each other’s effects – sometimes enhancing them, sometimes counteracting them. We can do cause-and-effect studies in the laboratory, seeking correlations between one type of environmental toxin and its effect, but will the results hold true in the real world, where many other toxins are also present? Thorough knowledge about environmental toxins in human blood and how they change over time is crucial for cause-and-effect studies.

Further reading:

Nøst TH, Breivik K, Fuskevåg O-M, Nieboer E, Odland JØ, Sandanger TM. 2013. Persistent Organic Pollutants in Norwegian Men from 1979 to 2007: Intraindividual Changes, Age–Period–Cohort Effects, and Model Predictions. Environmental Health Perspectives http://dx.doi.org/10.1289/ehp.1206317

Nøst TH, Breivik K, Fuskevåg O-M, Nieboer E, Odland JØ, Sandanger TM. 2015. Estimating Time-Varying PCB Exposures Using Person-Specific Predictions to Supplement Measured Values: A Comparison of Observed and Predicted Values in Two Cohorts of Norwegian Women. Environmental Health Perspectives http://dx.doi.org/10.1289/ehp.1409191

Published in Fram Forum 2016

Fram Forum is published once a year on behalf of FRAM - High North Research Centre for Climate and the Environment. Its aim is to imform the general public about the wide activities that take place within the Fram Centre. The magazine is available online free of charge  to any and all who are interested in topics related to climate, environment and people in the high north. Do you want a printed copy, please send an email to post@framsenteret.no