Cardiovascular reflexes and low long-term exposure to mercury vapour

Subjective symptoms related to autonomic dysfunction and quantitative non invasive tests measuring both sympathetic and parasympathetic functions of the autonomic nervous system were studied among a group of 41 chlorine-alkali workers with low long-term exposure to mercury (Hg degree) vapour and their matched referents. The test battery included measurements of pulse rate variation in normal and deep breathing, in the Valsalva manoeuvre and in vertical tilt as well as blood pressure responses during standing and isometric work. The exposure time had been 16 years on average, and the mean exposure to Hg vapour was estimated to have been about 30 micrograms/m3 of air. Only a tendency for a subtle reduction of cardiovascular reflex responses and a slight increase of subjective symptoms were seen in the exposed group, but no significant autonomic dysfunction was associated with the low level of exposure.