Assessment of Heavy Metal Contents of End-Of-Life Computer Monitor Cathode Tubes and Plastic Casings

Abstract

Development and innovation in computer technology have led to the generation of large quantities of end-of-life computing equipment with the attendant challenge of environmentally sound management, especially in developing countries. This study evaluated the heavy metal contents of the cathode ray tube (CRT) and the plastic casing of thirty (30) end-of-life computer monitors of different brands, years of manufacture (spanning 1981-2005) and countries of manufacture. The specimens were analysed for Pb, Cu, Cr, Zn, Cd, and Ni using atomic absorption spectrophotometer after acid digestion. The mean concentrations of metals in the CRTs varied widely: 1400-14300 mg/kg for Pb; 291-1750 mg/kg for Zn; <0.1-129 mg/kg for Cu; <0.1-15 mg/kg for Ni; <0.1-16.3 mg/kg for Cr, and <0.1-4.0 mg/kg for Cd. The Pb concentrations of all the CRT samples, with mean 5120±3000 mg/kg (range: 1400- 14300 mg/kg), exceeded the 1000 mg/kg Pb limit in the EU Directive on the Restriction of Hazardous Substances (RoHS) and the Total Threshold Limit Concentrations (TTLC) used by the USA Department of Toxic Substances and Control (DTSC), for characterizing waste as hazardous. For the plastic casings, the Cu and Cd concentrations in 10 % and 20 % of the samples respectively, exceeded the TTLC. The results of this study show that the CRTs are hazardous waste requiring environmentally sound management and the crude methods of management in Nigeria which include disposal at open dumpsites and surface water, as well as recycling using crude techniques are highly dangerous, exposing man and the ecosystem to toxins.