After briefly recalling the professional pathology characteristics of workers exposed to nitro derivatives and the perplexities surrounding the actual pathogenetic mechanism of the "Withdrawal hazard", the AA report the results of an investigation carried out among the workers of a dynamite producing plant. In the study, the NG and EGDN environmental levels were checked and the workers were submitted to ECG tracings, ECG D according to Holter, and monitoring of postural pressure changes both during exposure to the substances and during time-outs. The results obtained showed that the concentrations found in the plant were practically within the recommended TLV values, with no pathological modifications of the parameters examined. The AA put forward a pathogenetic hypothesis based on these findings and analyzing epidemiologic data on coronary sudden death as well as the mechanisms regarded as responsible for the disorders described in the literature in professionally exposed subjects. According to such hypothesis, the "Withdrawal hazard" (if any) would not be due to the cessation of the vasodilation effect of the nitro derivatives but would be a "rebound" phenomenon following the NG - and EGDN - inhalation induced stimulation to the production of endothelial prostaglandins, and of EDRF in particular, in exposed workers. The withdrawal of nitro derivatives inhalation would thus eliminate a vascular and coronary protection mechanism in the case of pathogenetic noxae at cardiovascular level. Such an interpretation would at last account for the time elapsing between cessation of work and occurrence of the disorders, which would not be justified by the cessation of the mere vasodilating action, since this wears out within a few hours.(ABSTRACT TRUNCATED AT 250 WORDS
