Detection of Toxic Metal in Silver Foundries

Smelting of silver from old ornaments and decorative articles is done in small foundries. In Ahmedabad city, there are 106 silver foundries situated in the residential and commercial localities. During the smelting process, a number of gaseous (SO2, NOx) and metallic (Ag, Cd, Cu, Pb, Zn) pollutants are released in the work environment and are also discharged into the community air by powerful exhausts. This study was undertaken to investigate the potential health hazards in workers of silver foundries and among people living in nearby localities and suggest suitable preventive measures.

The study consisted of medical examination of the silver foundry workers, measurement of dust, metallic and gaseous pollutants in the work environment and the community environment. Blood samples collected from the foundry workers and the general population residing in the vicinity of the foundries were analyzed for lead and cadmium.

Cadmium and silver concentrations were found to be above the permissible level of 10 mg/m3 (both for Cd and Ag). Lead concentration in the ambient air was found to be above the permissible criteria level of 1 mg/m3 as prescribed by the National Ambient Air Quality Standard (NAAQS) for residential areas. Concentrations of cadmium and other metals in the ambient air were also found to be higher than the reported values for residential areas. The source of cadmium was found to be adulteration of silver with cadmium as this metal is much cheaper than silver. Biological monitoring indicated that the mean blood cadmium level were 1.14 mg/100 ml in foundry workers and 0.32 mg/100 ml in the environmentally exposed subjects, which were significantly higher than the values for general population (0.1 mg/100 ml).

The recommendations for the prevention and control of health hazards included

(i) declaration of silver refining process as “hazardous” under section 2 (cb) of the Factories Act, thereby bringing the small factories under the purview of Factories Act;

(ii) installation of suitable pollution control devices and periodic monitoring of work environment and workers’ health and,

(iii) shifting of all silver foundries to a place away from residential zone to ensure better compliance of legal provisions and forestall community exposure. The recommendations have been accepted by the State Authorities and appropriate action has been initiated.