Abstract
With the increase of utilization of special steel containing antimony (Sb), the welding rod containing Sb has also been developed rapidly. However, the industrial hygienic consideration is left behind this development, since the biologic effects of Sb contained in the welding fumes are unknown up to now.
The author examined, with the use of an electron microscope and an X-ray diffractometer, the physical and chemical properties of the arc welding fumes containing Sb which are generated in the experimental welding, and conducted animal experiments with guinea pigs which were exposed to the fumes with Sb and without Sb. The animals were followed up after the inhalation of fumes and the biologic effects were assessed.
The results were obtained as follows :
1) The amount of fumes generated from the welding rod with Sb was less than the one without Sb, in the amount per unit length of rod as well as per unit time of welding.
As the results of chemical analysis, Sb content of the fumes was found to be 0.9% in the ilmenite type and 1.2% in the low hydrogen type. If the welding is operated under the conditions conforming to the commendation of IIW, the environmental Sb level should be kept within the threshold limit value of ACGIH (0.5 mg/m3 as Sb).
By the X-ray diffractometry, the Sb compounds in the fumes were identified as Sb2O3 and Sb2O5. These compounds were hardly soluble in warm water at the temperature of 37°Cand in the pH range from 4 to 10.
The particles in the fumes generated from the Sb containing rod showed a tendency to form dendritic or chain-like agglomerates of the secondary particles larger than a few microns by electron-microscopy.
2) In animals exposed to the fumes containing Sb, death rate, signs and symptoms in the exposed guinea pigs did not show any significant difference from those of the control animals. After the exposure, these animals were killed at the selected intervals and the levels of Sb were followed up in organs including blood and urine. The highest level of Sb was found in the lungs, the second level in the contents of the stomach and traces in the remainder. Sb level in the lungs was highest one hour after the exposure and it decreased with the lapse of time, showing 10% of the highest value after one week and a trace after 3 weeks.
Sb in the contents of the stomach showed the highest level 4 hours after the exposure, and Sb in the contents of the large intestines showed its peak after 12 hours,
