the brain is our most important organ it's the brain that makes us who we are it's a brain that helps us enjoy life it's the brain that makes us productive in society but because the human brain it's the most complex in the animal world it's also the one whose development is the most complicated and the complicated development of the brain with the billions of cells that have to end up in the right spots with the right connections that is what makes a plane extremely sensitive to toxic chemicals and this is something that we have only begun to realize they would lately what we have lined from neuro science is fat the human brain is so complex it's the it's the most complex in the animal world and it's also the most efficient but this would choir's that every second during early brain development every second two hundred new brain cells are formed now these brain cells then have to mike wait they have to move by themselves find their way to their final position where they need to meet with other brain cells and interact and make connections all of these processes i extremely complicated and very very sensitive to at first affects of chemicals one out of six children it could also also be of a very slight let's say reading disability and if you count all of this it's a major problem and they know that in the schools at the teachers know about it and in fact it's even bigger than that because what i'm talking about and what we have found in our studies of mike who expose children and studies of children exposed to pesticides before they were born is that the most common problem is simply that the children function at a plus a level they are bits slower they don't concentrate as well they don't really remember so well they can't find the words they have difficulty coordinating their finger movements for example problems like that so in most cases we we can't see if one particular child has been damaged because of pesticides or mercury or solvents or something else we can't see it what we can see is average shifts in distributions so so that if we look at a population of children those who have been exposed before they were born to say pesticides or mark away they function at a lower level on average and that means that the whole curve has been shifted to the left and they're more kids with problems and there are fewer kids who function at a very highly i first got interested in this problem of brain toxicity when i was a medical student my brother was the press secretary of the first minister of the environment the danish minister and here they were child and it it was tragic it made such a great impression on me and i wondered why are we not learning about this in medical school and medical in medical school they said well you know the placent world protect the freedom and you know as long as poisoning symptoms are not present there's not a problem wrong they got this wrong but it took me a couple of colleagues whether we could start some examinations of children and figure out if the mercury present in you know the oceans in sea food etc if that could  make a cost toxicity to brain development in people or not that's like the serious pollution in japan but it just the every day seafood now that  nations approved a convention to prevent mccue of pollution and the united states was the first country that signed it but listen two thousand and thirteen enough documentation to inspire decisions especially international collaboration on prevention of pollution in minamata people from pushed me and scientists then conducted autopsies and they wanted to learn what did they die from what happened and when they looked at the who were poison be fought there were born they had damage all over the brain and the crucial observation was that their mothers well ok the mot poisoned but the fetus in the way is suffering even for support policemen and many of them died when we began to analyze cord  blood that is a blood that you draw from the ability at childbirth we found that there were virtually hundreds of industrial chemicals and you know waste chemicals present in the chemicals we were looking at managed to get through and that means that the mother's exposure tearing apart and c and chemicals that she may have accumulated in her body during her lifetime are shared wit h the fetus some of them those that are fat soluble some of the chemicals are also passed into human milk and there for she will also share her chemical body burden with her child through breast feeding and so from the beginning of life we are all exposed to chemical that some of them are course presen in the environment because we live on a chemical planet so to speak but many of them are simply a result of environmental pollution and the usage of toxic chemicals in consumer products  and for other purposes and the concern is that if we exposed to chemicals like that from the very beginning of life from the beginning of brain development then maybe some of them can cause adverse effects so this is the big scientific question how do we identify these chemicals how do we figure out  which ones to control better and to record right so when we classify chemicals the ones that are known to cause poisoning in  chemicals actually chemicals that were developed to cause toxicity not to us of course but to pests of various kinds and many of them were developed to target insects in particular the nervous system of insects and i don't want to embarrass your bed but the chemistry inside the brain of a cockroach is not all that different from the chemistry inside your brain so when the pesticides can damage the nervous system of various kinds of pests we also need to be very very cautious because if humans are exposed to it then it can possibly damage the human brain in particular doing the very sensitive early development prefer to use clinical methods to try to understand how the brain is working and so we can't use a test let's say to make a diagnosis of the individual child but for example in the fair islands where we studied mercury we can see that there are tendencies to ward less optimal functioning and we can see that in very simple lower psychological tests but we can also see it when we put electrodes areas of the brain that are in actual use well will light up and one of the tests that we did was that we asked the child to to do this think or a position test here so  and normally when you do this then the this part of the brain the motor cortex on the opposite side will light up and so and  does in children without exposure to high levels of mercury but we can see that kids who one fortunate to have elevated to exposures we can see that they used both sides of the brain in order to do this with their left hand and that is clearly abnormal it's like a batch of ration of the brain that hasn't completed as it should have children have deficits we have looked at all of the human studies all of the epitome on cheese studies where we ourselves or our colleagues have followed children from childbirth and through to school age or and even longer and assessed brain functions in week too the exposure to toxic chemicals  from early development now all of that evidence like mercury has been accumulated over many many years it takes decades to do these studies and so far we been able to identify twelve chemicals that we are certain can cause damage to the human brain and and of course its lead and mercury and then there are a couple doesn't if you want is a very short list it's the tip of an iceberg that we need to control better because at exposures that we're all exposed to today we know that adverse effects on brain development can happen then there is an additional group of chemicals where we just don't know yet for sure if they can damage human brain development but we know that they can damage brain development in rodents we know that experiments with rats and mice and when i go through that last then there are maybe as many as one thousand chemicals that can damage brain development in laboratory animals and most of them the vast majority of them have never been examined in regard to human brain development we haven't had the time and most of them are not regulated at all in recovery to protecting us from exposures that there's say an additional source of  the chemical can can reach for brain and cause neurological symptoms that means that the brain the brain is once you get the chemical in to the body the chemical will pass through the blo brain barrier get into the brain and act and cause at orsa facts to the brain cells we think that all of these very same chemicals were also passive placent and since they can damage brain cells in the adult we think that the developing brain would be even more vulnerable than the adult brain and that's a list of about that over two hundred compounds again these compounds are not regulated for the vast majority of sick and they we're all exposed to them  so we have a whole picture whole perspective of chemicals that we are quite convinced were percent a hazard to shuman brain development i would say we have the tools now but one we have our animal tests always city has developed a protocol how to determine if a chemical can cause damage to brain and that's a whole lot faster to they're waiting to to conduct an experiment in their involvements so we have the tools to do it all we need to do is to make the decision in the meantime there's also been some controversy as for us of all there will always be scientists who say well you know this is not proven and there's still some doubt and you know maybe we need to do some more research so there will necessarily always be uncertainties but in regard to mercury as with lead with past the sides with many other this has been true with my career as well and so when my studies were evaluated by the national academy of sciences and the united states environmental protection the end people won't understand that science speaks a soft language we will never express ourselves as if we are one hundred percent certain about issue we have to deal with here in america but it's also an issue that is of international concern i participated very recently in a workshop with the world health organization and it was clear from the discussion that the colleagues from the world health organization and international colleagues in the field that they shared this and  must protect the next generation sprains from chemicals that can harm brain development and i understand that world health organization is eager to take the lead but but obviously nothing will happen unless the member states like america like the e u all support that so over time we have seen that of course not because lead on market became more toxic with time it's simply because we had underestimated how bad these chemicals or and therefore it was only when we finally got better evidence that we realized all we done something wrong in the past we better decrease the exposure element so with pesticides it has been a similar experience but but more often pesticides get banned after maybe one or two decades of use because then it's found out that they were more toxic than the intended we recently did a study in denmark woman working with pesticides gets pregnant then she is excused from work and she's paid being paid unemployment joining the two ration of the pregnancy after the pregnancy has been determine looked at those women's children at school age and we had a comparison group of kids of other employees from the same facilities not exposed to pesticides and it would say pesticides still had deficient functions in the brain so that really scared me that we not doing enough to control the these chemicals they haven't been tested sufficiently in recurred to toxicity to the brain and then we also have to look at the global picture because pesticides set up banned here in the united states or in denmark  and safety controls are exposed to them under circumstances that i'm quite certain well costs chemical brain drain in the next generation and we have a responsibility i think to help those countries protect the populations against these chemicals and promote brain development in the next generation so the status today is that number one the consumer can do a little bit but basically we cannot ourselves make decisions the necessary decisions in order to protect ourselves and our children against chemical brain drain hours the chemicals that will damage the next generation sprains we can't so something needs to be done unfortunately that legislation is totally irrelevant in with curry to the protection of the next generation sprains it doesn't help at all so we're not testing whether existing chemicals or new chemicals can affect brain development we're not regulating chemicals that we already know can cause damage to brain development and we not sharing the information that we do have with consumers so that they can perhaps make at least some decisions on their own part and perhaps also inspire you to a we realize that we have acted irresponsibly there's a whole generation of children who have been exposed to lead and whose brains are not functioning compounds and there may be an even larger and i'm pro chemicals that have already cost that damage we should not continue allowing that to happen i think being a grandfather age i think that it's responsible for grandchildren and the following generations we we have to we have to make it the situation to change this way of acting and i'm speaking  here as not just as a scientist but as a human being because i i think this is an issue where public health science has shown some very clear with salts and of course