Neurotoxicants are substances capable of causing adverse effects in the central and peripheral nervous system, and in sense organs.
These effects include narcosis, nausea, dizziness, vertigo, irritability, euphoria, movement coordination problems, impaired memory and behaviour, and alterations of the peripheral nerves. Exposure to some neurotoxicants has also been associated with neurodegenerative diseases like Alzheimer"s disease. Some neurotoxic effects may be reversible (e.g. narcosis, nausea, dizziness, vertigo) and others may be irreversible (e.g. neurodegenerative diseases).
Former Dangerous Substances Directive (67/548/EEC) and the new Regulation 1272/2008 (CLP) identify neurotoxic substances with the following risk phrases ® and hazard statements (H):
R67 or H336: May cause drowsiness and dizziness.
R23 or H330 or H331: Toxic by inhalation
R24 or H311: Toxic in contact with skin
H301 R25: Toxic if swallowed
R26 or H330: Very toxic by inhalation
R27 or H310: Very toxic in contact with skin
R28 or H300: Very toxic if swallowed
The only risk phrase ® or hazard statement (H) specifically associated with neurotoxic effects is phrase R67 or hazard statement H336, the remaining statements are associated with both neurotoxicant and toxic substances.
Neurotoxicants can cause major permanent functional changes in the central or peripheral nervous system and due to their high impact on occupational health and frequent use in industry, these substances actually raise a high level of concern.
Given the serious effects of exposure to these agents they are classified as highly hazardous chemicals and risks of exposure must be avoided. Their elimination or substitution are priority actions and only in those cases where these actions are not technically feasible, workers’ exposure must be reduced through other measures (individual and collective protection) following the principles of preventive action expressed in Framework Directive 89/391/EEC on the introduction of measures to encourage improvements in the safety and health of workers at work.
There is no unified model for the classification of neurotoxic substances. However, several classification systems have been proposed based on their chemical structure, chemical or physical properties, effects, and other properties.
There is no available official list of substances that cause major permanent functional changes in the central or peripheral nervous system. CLP regulation only includes narcotic effects; therefore it does not include a classification for neurotoxicity itself or specific hazard statements. In view of those facts, literature review was used to identify occupational neurotoxicants and include them in the list.
Neurotoxicants that cause unspecific clinical changes without identification of the biological bases involved (e.g. narcosis, irritability, euphoria, lack of movement coordination, etc.)
Level 2
Neurotoxicants causing measurable biochemical changes (e.g. neurotransmitters at the level enzymes activity)
Level 3
Neurotoxicants that cause physiological changes (such as myelinopathy or alterations in sensory organs)
Level 4
Neurotoxicants that cause morphological changes in cells in the central nervous system (CNS) or peripheral nervous system(PNS) (e.g. cell death, axonal injury or sub-cellular morphological alterations)
Another classification criterion is reflected in other studies, according to the specific location where the chemical acts or interacts (on myelin, on the axons, substances associated with neuronal damage, etc.).
Council Directive 89/391/EEC of 12 June 1989 on the introduction of measures to encourage improvements in the safety and health of workers at work
Regulation 1272/2008 (CLP) on classification, labelling and packaging of substances and mixtures.
Council Directive 67/548/EEC of 27 June 1967 on the approximation of laws, regulations and administrative provisions relating to the classification, packaging and labelling of dangerous substances.
Council Directive 98/24/EC of 7 April 1998 on the protection of the health and safety of workers from the risks related to chemical agents at work.
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