DETERMINATION OF HEAVY METALS IN PLASTIC HOUSING OF SELECTED OBSOLETE MOBILE PHONES AND TELEVISION PRODUCED IN SOME YEARS BETWEEN 1980 AND 2000
ABSTRACT
The concentrations of lead, nickel, silver, zinc, chromium, copper, vanadium, cobalt, and cadmium were determined in plastic housing of waste television sets produced in some years of 1980’s, 1990’s and 2000’s, and in plastics of waste mobile phones produced in some years of 1990’s and 2000’s, the samples were collected mainly from mobile phone and television repairers at railway in Ogbete main market, Enugu in Enugu state, and the famous computer village in Ikeja, Lagos State Nigeria, with the aim of providing information on the trend in concentration of these metals within the years. The concentrations of these nineelements were determined by flame atomic absorption spectrometry after acid digestion using a 1:1 mixture of sulphuric and nitric acid. The mean concentration of these metals (mg/kg) in the television set for the 1980’s, 1990’s and 2000’s respectively are (12.76±17.61, ND, 1.33±2.30) for lead; (1.84±1.33, 1.48±1.26, 2.79±2.47) for nickel; (1.53±2.35, 16.20±29.66, 40.42±20.49) for silver; (82.24±50.59, 159.69±55.87, 113.29±69.175) for zinc; (7.12±10.50, 4.23±1.07, 5.26±4.73) for chromium; (3.26±1.09, 2.76±1.15, 2.39±1.05) for copper; (4.84±10.83, 24.05±7.56, 26.67±11.13) for vanadium; (9.30±5.27, 8.40±3.00, 12.63±12.99) for cobalt; (2.60±1.25, 4.05±1.81, 4.28±1.11) for cadmium (ND – Not Detected). The mean concentration of these metals (mg/kg) in the mobile phones are (50.83±65.85, 5.71±3.55) for lead; (23.80±27.89, 1.95±1.28) for nickel; (48.04±89.00, 7.82±4.61) for silver; (325.11±261.50, 105.59±26.72) for zinc; (5.47±3.97, 4.38±3.93) for chromium; (643.92±880.48, 47.51±97.06) for copper; (20.94±5.59, 34.50±25.61) for vanadium; (4.92±1.55, 13.21±8.16) for cobalt; (8.14±7.06, 17.60±19.14) for cadmium.The total threshold limit concentration of these metals are; lead- 1000, nickel- 2000, silver 500, zinc- 5000, chromium- 2500, copper-2500, vanadium-2400, cobalt-8000, cadmium-100 (mg/kg) (sourced from California Code of Regulations). Although the mean concentration values of Zn, Cu and Ag in both the mobile phones and television samples were relatively high compared to the total threshold limit concentration (TTLC), all the metal concentration values were below the threshold limit except for Ag. Two results exceeded the TTLC threshold for Ag (500 mg/kg) within phone samples (1990). These results suggest that there may not be any immediate danger from waste television and mobile phone plastic housing investigated.