Evaluating the health risk of metals (Zn, Cr, Cd, Ni, Pb) in staple foods from Lagos and Ogun States, Southwestern Nigeria.

The study evaluated the health risk of metals in commonly consumed staple foods from Lagos and Ogun states, southwestern Nigeria. One hundred and thirty-three food samples were collected and analyzed for Zn, Cr, Cd, Ni, and Pb using atomic absorption spectrophotometric method. Data collected were analyzed for simple descriptive and inferential statistics using SPSS for Windows. The health risk of metals in staple foods was assessed for average daily dose (ADD), hazard quotient (HQ), hazard index (HI), and cancer risk (CR). Results showed the highest concentrations of Zn (18.99 ± 13.62 mg kg-1) and Ni (0.21 ± 0.10 mg kg-1) in beans, while the highest amount of Cr (2.04 ± 1.44 mg kg-1) was obtained in rice. Cd concentrations in staple foodstuffs ranged from < 0.01 to 0.30 mg kg-1, while Pb was below the detection limit. The average levels of Zn in beans and maize were higher than the recommended dietary allowance (9.5 mg kg-1) of the Institute of Medicine. The mean concentrations of Cr and Cd (except for rice) in staple food samples were also higher than the permissible standards. The health risk data revealed HQ value greater than 1.0 for Cr in the food samples, indicating non-carcinogenic adverse health effects. The HI value greater than 1.0 in staple foods established cumulative adverse effects of metals. The carcinogenic evaluation of Cr (in all the food samples) and Ni (in beans) showed CR values greater than the acceptable limit of 1.0 × 10-4, thereby demonstrating possible development of cancer through consumption of the staple foodstuffs.

Bioremediation of industrially contaminated soil using compost and plant technology.

Compost technology can be utilized for bioremediation of contaminated soil using the active microorganisms present in the matrix of contaminants. This study examined bioremediation of industrially polluted soil using the compost and plant technology. Soil samples were collected at the vicinity of three industrial locations in Ogun State and a goldmine site in Iperindo, Osun State in March, 2014. The compost used was made from cow dung, water hyacinth and sawdust for a period of twelve weeks. The matured compost was mixed with contaminated soil samples in a five-ratio pot experimental design. The compost and contaminated soil samples were analyzed using the standard procedures for pH, electrical conductivity (EC), organic carbon (OC), total nitrogen (TN), phosphorus, exchangeable cations (Na, K, Ca and Mg) and heavy metals (Fe, Mn, Cu, Zn and Cr). Kenaf (Hibiscus cannabinus) seeds were also planted for co-remediation of metals. The growth parameters of Kenaf plants were observed weekly for a period of one month. Results showed that during the one-month remediation experiment, treatments with 'compost-only' removed 49 ± 8% Mn, 32 ± 7% Fe, 29 ± 11% Zn, 27 ± 6% Cu and 11 ± 5% Cr from the contaminated soil. On the other hand, treatments with 'compost+plant' remediated 71 ± 8% Mn, 63 ± 3% Fe, 59 ± 11% Zn, 40 ± 6% Cu and 5 ± 4% Cr. Enrichment factor (EF) of metals in the compost was low while that of Cu (EF=7.3) and Zn (EF=8.6) were high in the contaminated soils. Bioaccumulation factor (BF) revealed low metal uptake by Kenaf plant. The growth parameters of Kenaf plant showed steady increments from week 1 to week 4 of planting.