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11 November 2019 ..:: Neurodevelopmental Disorders  » State of the art ::..   Login
Neurodevelopmental Disorders

State of the art

Causal - effect diagram


 Current state of the art
Neurodevelopmental disorders are those that affect the central nervous system of the offspring as a result of maternal exposure to chemicals during gestation or lactation. Despite major advances achieved by the rapid development of science and technology, European countries are confronted with increasing problems in the field of neurodevelopment and behaviour.

Neurodevelopmental disorders, such as mental retardation, attention deficit disorder, cerebral palsy, and autism are common, costly and can cause lifelong disability. Their aetiology is mostly unknown. There is a concern that environmental influences are involved due to the rapid increase over only two or three decades of disorders such as attention deficit disorder, autism and autoimmune diseases such as diabetes (type 1 and 2). Environmental influences include both voluntary exposure to hazards such as alcohol, smoking and drugs and involuntary exposure to chemicals such as PCBs and dioxins.

A recent review by Grandjean and Landrigan of the available scientific literature identified only a small number of industrial chemicals - lead, methylmercury, polychlorinated biphenyls, arsenic, and toluene - as recognised causes of neurodevelopmental disorders and subclinical brain dysfunction. Documentation on these hazards shows that exposures during early development can cause brain injury at dose levels much lower than those affecting adult brain function. Recognition of these risks has led to some evidence-based programmes of prevention, such as eliminating lead additives in petrol but these prevention campaigns were initiated only after substantial delays. The review by Grandjean and Landrigan also identified 201 additional industrial chemicals, which are known to cause clinical neurotoxicity in adults and may therefore be considered potential causative agents for neurodevelopmental disorders.

Although almost nothing is known about the possible effects of these substances on the developing brain, a cautious interpretation of current evidence on vulnerability during development would suggest that these substances are likely to affect the nervous system of children and the foetus at much lower exposure levels than those that cause symptoms in adults. Intra-uterine exposure resulting in intra-uterine growth retardation (IUGR) can be the origin of later diseases in childhood, adolescence and adulthood as demonstrated by Barker et al. with neurotoxicants included as an important factor.

In the field of neurodevelopmental disorders and behavioural abnormalities the main “epidemics” of today are:

· Autism;
· Attention Deficit Hyperactivity Disorder (ADHD);
· Learning disabilities;
· Eating disorders, a.o. anorexia and bulimia;
· Criminality;
· Hearing problems.

The prevalence of these deficits should be monitored in a standardised manner. Based on research in the field of neurodevelopmental disorders, important policies in public health have to be developed for prevention. At the level of government and industry, controlling and lowering exposure levels of neurotoxicants must be developed and enforced further for the prevention of associated disorders.

Progress beyond current state of the art by HENVINET:
Concerted actions aim to promote and support the networking and coordination of research and innovation activities. This is very important in the area of neurodevelopmental disorders where knowledge of exposure trends and causal links is limited. Reports and information from research activities and networks (e.g. SCALE Technical Working Groups and PINCHE) that have specifically considered neurodevelopmental disorders in relation to environmental exposures will provide a valuable source for the state of the art documents to be produced by HENVINET.

New findings from disparate research groups and activities in the fields of health and environment will be identified by searches in databases such as PubMed, Medline and Embase and scientific journals. Conferences and their proceedings, workshops, meetings and their reports including regional and national research meetings will also be valuable sources of new information in this area. HENVINET will develop a network to access people and reports with current/recent information relating to neurodevelopmental disorders and environmental exposure in order to facilitate dissemination of the most up-to-date information available in this field, building upon the findings from SCALE and PINCHE and including contact with groups currently working in the area e.g., Framework 6 projects and other international and national groups with a focus on the same subject. The biggest challenge is to find out who is doing what and this will be achieved through contact with the acknowledged experts in this area as suitable nodes to link to other people/information in the field and the use of state-of-the-art internet solutions and methodologies.

The SCALE Technical Working Group on priority diseases, subgroup neurodevelopmental disorders (January 2004), highlighted gaps in knowledge and listed programmes and projects of relevance. The general gaps relate to knowledge about trends in environmental and internal exposure and prevalence data for neurodevelopmental disorders and a lack of descriptive epidemiology data and monitoring data. Without more knowledge about the trends, it will be difficult to determine the causation of neurodevelopmental disorders. There are also knowledge gaps relating to specific substances such as PCBs, dioxins and PBDEs, pesticides, solvents, metals and organometals, food additives, therapeutic agents and mixed exposures. In addition, the report highlighted knowledge gaps concerning risk-benefit relationships for consumption of specific food types such as fish and breast milk with particular concern regarding pregnancy and the diet of infants and young children. Information to help fill in some of these knowledge gaps will be contributed through networking with several existing European projects and networks in the area of neurodevelopmental disorders and environmental influences which will inform policy decisions in this area.

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