The 15 NTP PACs represent a small but non-negligible part of lung-cancer risk with regard to diesel exposure. From this point of view, the dibenzopyrene family are important compounds to be considered.

ABSTRACr Hand tremor due to industrial exposure to metallic mercury vapour was recorded in 26 exposed and 25 non-exposed male workers by an accelerometer attached to the dorsum of the hand. The subjects were instructed to hold the hand and the forearm in the same position first without and then with a load of 1250 g supported by the hand. Analysis of the records showed that the highest peak frequencies (HPF) (the frequency corresponding to the highest acceleration) were higher in the exposed men than in the controls and were related to the duration of exposure to mercury and to age. The changes in HPF between rest and load were again higher in the exposed men than in the controls and again related to the duration of exposure and to age. The second moment (M2) (an index taking into account the whole recorded spectrum) was similar in the exposed men and controls at rest. The changes in M2 between rest and load were higher in the exposed men than in the controls but were related to duration of exposure and to the-biological measurements (loge of mercury in urine or blood) and not to age. These neurophysiological impairments might result from the tendency of metallic mercury to accumulate in the cerebellum and the basal ganglia. These results are consistent with the hypothesis that metallic mercury, even at concentrations probably below the current TLV-TWA of 0 05 mg/m3, can lead to neurological disorders.The most consistent and pronounced effects of exposure to elemental mercury vapour are on the central nervous system (CNS). The first group of effects consists of a neuropsychiatric complex known as "erethism," which includes insomnia, loss of appetite, excessive shyness, and emotional instability.

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Recent literature about the biological monitoring of styrene-exposed workers is reviewed. Styrene primarily exhibits its toxicity on the central and peripheral nervous systems, although its mutagenicity and chromosome damaging ability also may be relevant. Uptake, transformation and excretion of styrene show that beside the usual biological indicators, such as urinary mandelic and phenylglyoxylic acids (main metabolites), other indicators also may be of interest. These include styrene in expired air, in blood or in urine. Moreover, intermediate or final metabolites such as styrene glycol or mandelic acid in blood also have been proven to be useful in the interpretation of individual values. The most widely used analytical methods for these indicators are gas or high performance liquid chromatography. Correlations between exposure and the different biological indicators mentioned above show that the most reliable indicators are mandelic acid (MA) in urine sampled at the end of the work shift (but not the first day of the week) and the sum of mandelic and phenylglyoxylic acids (MA + PGA) in urine sampled 16 hr after exposure (before the next shift). The biological exposure limit values corresponding to the threshold limit value-time-weighted average (TLV-TWA) of 50 ppm of styrene are 850 mg MA/g creatinine in the end-of-shift sample and 330 mg MA + PGA/g creatinine in the next-morning sample. Other biological indexes, such as styrene glycol (phenyl ethylene glycol) in blood or styrene in urine, look promising but require further research in field situations.