Total and bio-accessible toxic metals in low-cost children toys sold in major markets in Ibadan, South West Nigeria

Abstract

Toxic metals are usually added to children's toys to improve/impact some intrinsic properties such as colour which attracts children. Some of the toxic metals have life-threatening potentials on children when ingested. There is no specific legislation in Nigeria that monitors and regulates limits of such metals in toys. This study assessed total and bio-accessible concentrations of Pb, Cd, Cr, Ni, and Mn in imported low-cost children's plastic toys sold in popular markets in Ibadan, Nigeria. A total of 22 different toys were purchased and subjected to an indicative test for the presence of polyvinyl chloride (PVC) following the Beilstein method as well as analysing for total recoverable metals and migrated fractions into simulated saliva and gastric environments. Toy samples were crushed, ashed, and dissolved with dilute nitric acid for total recoverable metals while migration studies were carried out using simulated saliva and gastric environments to check bio-accessible fractions that could leach into the human system. Metals in all extracts were determined using flame atomic absorption spectrophotometric technique. The indicative PVC test showed 12 samples positive to PVC and 10 tested negative. Total recoverable metal concentrations (mg/kg) ranged as follows: Pb: Below Detection Limit (BDL) - 4838, Cd: BDL - 44.9, Cr: 0.331–79.8, Ni: 0.273–59.1 and Mn: 0.205–31.0 with Pb and Cr having 18 and 14% of samples higher than EU limits of 90 and 60 mg/kg. Bio-accessible concentrations in artificial saliva were: Pb: BDL - 42.4, Cd: BDL-0.450, Ni: BDL-1.40 and Mn: BDL-0.058 with Pb higher in 70% of samples compared to 2.0 mg/kg migrated EU limit while other metals were within the limits. Furthermore, metal concentrations that migrated to gastric environment were: Pb: 8.24–50.3, Cd: BDL-0.057, Ni: 0.103–1.96 and Mn: BDL-1.37 with Pb in 100% of samples higher than 2.0 mg/kg EU migrated limit. Chromium migration in both environments was BDL. The results of this study suggest that toxic metal contents are present in both PVC and non-PVC made toys, but higher in PVC containing toys. Though the calculated hazard index for health risk assessment of heavy metals was < 1 for all metals, Pb concentration in both total recoverable extract and saliva and gastric environments seem to be problematic and constant monitoring and regulation are required.