He identifies the effects of chemicals on mice and humans

That the brain is affected by environmental toxins has been known for some time. The question, however, is which chemicals cause which specific kinds of behavioural disturbances and at what doses? Some unique studies carried out with mice have given environmental toxicologist Stefan Hallgren some important clues.

DDT, PCB, PFOS are abbreviations which have found their way into the general consciousness in recent decades. Used as an agricultural pesticide, chemicals in industrial equipment and a fluorosurfactant in fire-fighting foam, their effects have been thoroughly investigated. At the Department of Organism Biology, environmental toxicologists are working to identify the effects of environmental toxins on health and the environment.

“From time to time, water repellent chemicals such as PFOS receive a lot of attention in the media. It turns up in groundwater which is not where you want to find it,” says Stefan Hallgren. “The substance is now banned but it is still present in the environment, especially in and around fire-fighting training facilities.”

Despite all the efforts at decontamination, it takes a long time for the chemicals to be broken down, says Stefan Hallgren. It is therefore important that we examine the consequences of them spreading. In one of his projects, he has investigated two newer kinds of agricultural pesticides. One is an organophosphate and the other a carbamate compound. The studies are being carried out by a large research consortium financed by the EU since 2012.

“These pesticides have replaced older ones which we already knew were toxic. There are a lot of people working in agriculture. The substances get into their clothes and so they take the chemicals into their homes. In this way, children, pregnant women and people who just live near farms are indirectly exposed to the chemicals.”

These pesticides are mainly designed to attack the neurotransmitter acetylcholine which controls muscle contractions. When the substance is sprayed on fields, the toxins cause insects to collapse.

“The problem is, though, that the human nervous system is very reminiscent of an insect nervous system. That is why we are particularly interested in this substance.”

It was while working as a post-doctoral fellow at Södertörn University that Stefan Hallgren started to look into the effects of chemicals on the nervous system, especially while it was still developing. While there, he studied behaviour changes in fish which were subjected to endocrine disruptors. In 2013, he was given the opportunity to investigate the effect of environmental toxins on mice at Uppsala University.

“The experiments we are doing now involve feeding 10-day-old mice with a solution which is to be as close as possible to suckling milk. The solution contains two different agricultural pesticides in doses which are close to what a baby might consume through breast-feeding.

Human brains develop most quickly in babies and children up to the age of two. It is then they are most sensitive to the effects of chemicals. The equivalent critical time period in mouse development is up to 3-4 weeks from birth, with a peak in sensitivity normally around day 10. When mice in the experiment reach two months of age, they display essentially the same behaviour patterns.

“Mice subjected to environmental toxins are much more anxious. When put in a new cage, right from the start they are considerably more passive than the control group. The activity level of the treatment group then increases and they find great difficulty in becoming habituated to their new surroundings. They become hyperactive.”

The studies carried out with mice are part of a major EU project. The Uppsala group is led by Henrik Viberg and Per Eriksson, ecotoxicologists at the Department of Organism Biology. The project will come to an end in autumn 2015 but before that Stefan Hallgren hopes to gain further insight into the effects of environmental toxins on the nervous system.

“We are presently looking at which particular brain mechanisms are affected by these chemicals and in what way they are affected. We can see behavioural changes, but we want to know which specific underlying functions are affected.”

Would you like to do research into anything else?

“I would very much like to go further with this, possibly in collaboration with an Alzheimer’s researcher, perhaps at the university hospital Akademiska sjukhuset. I want to see if environmental toxins increase the risk of Alzheimer’s or if some chemicals hasten its progress. It would be very exciting to look into this.”

Anneli Björkman