Neurotoxic syndromes and occupational exposure to solvents.

Neurotoxic syndromes due to occupational solvent exposure present a worldwide health problem, the magnitude of which varies from country to country. Apart from the relatively clear-cut exposure-effect relationships in acute solvent intoxications, those caused by long-term, low-level occupational exposure to solvents are more difficult to detect. Controversial opinions and even debate are frequently encountered in literature on this matter. This is partly due to differences in neurobehavioral methods used, partly to difficulties in obtaining accurate information about exposure. These effects can be studied in humans using biochemical, clinical, and epidemiological methods. It is thus quite conceivable that direct comparison of the results obtained by different methods is not always possible. Moreover, exposure to a variable mixture of solvents is frequent in an occupational setting which is problematic from the toxicological point of view. The clinical pictures of "chronic" occupational solvent intoxications are, with few exceptions, quite nonspecific in nature and share several common features regardless of the underlying chemical exposure. The development of manifest disease is insidious and high interindividual variation of symptoms and signs exists. Some solvents cause primarily peripheral neuropathy. Deterioration in many psychological and neurophysiological functions can be seen. The most common subjective symptoms of solvent intoxication are headache, tiredness, memory disturbances, and dizziness. Clinical findings comprise signs of the central nervous system depression (psychoorganic syndrome, tiredness), dizziness, disturbances in coordination, and general neurasthenic signs. From the clinical point of view, it is important to define the criteria for a diagnosis. In different countries the diagnostic criteria for solvent intoxication may vary considerably, which provides additional difficulties in interpreting the results of studies in this field.