The overall health burden of environmental toxins has decreased. But the all-clear cannot be given – especially not for children.
Not without consequences: Mercury and PCBs in fish are suspected of causing brain diseases. Picture: dpa
Modern life is characterized by a whole host of substances. Not only are there numerous chemicals in PET bottles and computer casings, but the list of ingredients in food and drinking water, cosmetics, clothing, furniture and house dust is also long – and usually not visible to the consumer.
It is true that some harmful substances have been successfully banned in the past. For example, according to studies by the Federal Environment Agency (UBA), the German population’s exposure to lead, arsenic, cadmium and mercury as well as polycyclic aromatic hydrocarbons (PAHs) has fallen. Studies by the German Federal Institute for Risk Research (BfR) also show: Today, about 60 to 95 percent fewer harmful substances are found in women’s milk than 20 years ago, such as brominated flame retardants, synthetic musk fragrances or dioxins.
But other studies, such as the UBA’s Children’s Environmental Survey, show on the other hand that substances such as phthalates, which soften plastic toys, for example, are found in alarming amounts in children’s blood and urine. Heavy metal contamination has also decreased, but is still too high for some scientists.
For example, the European Food Safety Authority (Efsa) wrote in an opinion last winter, "Current levels of lead exposure pose a low health risk for most adults. However, there are concerns about possible effects on the neurological development of young children."
What exactly these environmental contaminants do to the human brain when they are ingested over many years, even in relatively small doses, has hardly been proven so far. Only 20 percent of the market-dominating everyday chemicals have even been tested for their neurotoxicity. Moreover, modern humans are exposed to a whole cocktail of chemicals.
Causes of ADHD?
Ulf Sauerbrey, an educational scientist at the University of Jena, Germany, therefore wondered, "Could ADHD (attention deficit disorder), for instance, be caused by environmental toxins?" And compiled all the research on the subject in a book published in 2010. His conclusion: "Environmental toxins could be a major cause of neurobiological changes in the nervous system that lead to the diagnosis of ADHD."
Of course, in ADHD, several causes are discussed for the development of the disease. For example, a certain genetic predisposition or alcohol, nicotine and drugs consumed during pregnancy are considered risk factors for the child.
Sauerbrey also does not believe that pollutants alone make children fidgety. Nevertheless, he is convinced: "There are now sufficient studies to show that lead, for example, plays a role similar to that of smoking in pregnancy." In addition, there are indications that mercury could also promote ADHD, as do phthalates. Polychlorinated biphenyls (PCBs) and some pesticides at least caused individual symptoms of ADHD.
In a 2009 study by the University of Bristol, antisocial behavior and hyperactivity were three times more common in children with elevated, but quite common, blood lead levels than with low levels of exposure. Not much is known yet about the mechanism of action.
Lead and zebrafish
In 2001, Stephen Devoto, a neurologist at Rockefeller University, showed in experiments with zebrafish that lead reduces the dopamine content in the nucleus accumbens, a region of the forebrain, compared with test groups – an abnormality that is also assumed to be causal in ADHD.
There is also growing evidence that pollutants are involved in other neurological disorders. According to Philip Landrigan, an epidemiologist at Mount Sinai School of Medicine, lead or mercury exposure during pregnancy may also play a role in the development of autism.
In Alzheimer’s, heavy metals are also being discussed as a contributor. The pollutants could lead to the formation of more free radicals in the body, which in turn damage brain cells, especially the mitochondria, and cause them to die. High lead exposure, common in the 1960s, has also been linked to schizophrenia.
In addition, environmental toxins could also trigger Parkinson’s disease. For example, the inhabitants of the Danish Faroe Islands are particularly frequently affected by this brain disorder.
Mercury in fish
Lene Wermuth, a neurologist at Odense Universitetshospital, suspects that the traditional diet rich in fish, including whale and seal blubber, which is rich in mercury and PCBs, may be a trigger for the brain disease. Genetic peculiarities of the Faroese also made the islanders particularly susceptible.
In 2007, Mark Noble, a neurologist at the University of Rochester, found a universal mechanism for why heavy metals in amounts found in the environment can affect the brain. They cause a group of stem cells in the central nervous system to stop working. As a result, in young children, for example, not enough new nerve cells and new synapses can form between the cells.
But despite all this research, environmental toxins as causative agents have not yet found their way into the textbooks. "Current ADHD research is skeptical because it does not want to unnecessarily unsettle parents and those affected," Sauerbrey reports.
The chemical industry may also have its fingers in the pie here. U.S. researchers who examine environmental toxins for their danger report that they have been massively hindered in their work.