الفهرس 
IntroductionOnly 14 pages are availabe for public view
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Abstract
IPCS environmental health criteria reported that the ability to assess how chemicals adversely affect the nervous system has significantly improved, since the 1986. This progress is reflected in the availability of a number of national and international neurotoxicity test guidelines , risk assessment guidelines and guidance papers and international neurobehavioural test method validation studies.
Although there is marked improvements in neurotoxicity risk assessment, there is still worldwide concern about the potential neurotoxic effects of chemicals. Of particular concern is the deficiency of information on putative relationship between exposures to low levels of environmental chemicals and effects on neurobehavioural development in children and neurodegenerative diseases in the elderly. Only a small fraction of chemicals have been adequately evaluated for neurotoxicity.
Multiple potential target sites and adverse results are due to the complexity of the nervous system. The wide variety of specialized cell functions seen in the nervous system is not present in other system. Different aspects of neurotoxicity depend on the different susceptibilities of the different cells which compose the nervous system. The nature and the function of the blood-brain barrier in modulating the access of some chemicals to the nervous system are also unique considerations in assessing neurotoxicity. In addition, certain specialized cells outside the barrier have important integrative functions that orchestrate numerous physiological, metabolic and endocrine processes. These integrative functions are fundamental for cognition and higher-order neural functions, but knowledge about the mechanism of disruption by chemical exposure is limited.
Human studies provides the most direct methods of assessing health risk for detection of neurotoxicity, but is often complicated by confounding factors and inadequate data. There is difficulty to detect the exposure levels in humans, and the neurological status of populations is extremely heterogeneous. However, there has been significant progress in the last decade in developing validated methods for detecting neurotoxicity in human beings. There are several sources of human data including accidental and occupational exposures, case-studies, clinical evaluations, epidemiological studies, field and laboratory studies. Standardized neuropsychological mental testing, validated computer-assisted tests, neurophysiological and biochemical tests, and refined imaging techniques can provide and become well established. These methods can be used to assess a variety of human neurotoxic end-points and have provided useful data for the purpose of neurotoxicity risk assessment.
Till now, it is still important to depend on information derived from experimental animal models for most neurotoxicological assessments. Behavioural, biochemical, electrophysiological and histopathological methods, along with validated batteries of functional tests, are now routinely used in animal studies to identify and characterize neurotoxic effects. The quality of the data available for risk assessment has been improved by standardization and validation of animal test batteries. New guidelines for standard acute and repeated-dose toxicity studies now also include behavioural and histopathological end-points specifically intended to improve the evaluation of the nervous system. Although animal models have been used extensively to study the differential sensitivity of developing organisms to chemical insults, current guidelines for developmental neurotoxicity are complex, and the results are often subject to varying interpretations. Most neurotoxicity testing strategies use a tiered approach.