Ecological and potential health risk assessment of heavy metals in soils and food crops grown in abandoned urban open waste dumpsite.

PURPOSE: This work investigated the levels, ecological and potential human health risk of heavy metals in soils and crop plants of an abandoned open municipal solid waste dumpsite being used for agricultural crop planting at Ugwuaji in Enugu, Nigeria. METHOD: Samples of soils and plants were collected from the site and heavy metals (Pb, Cr, Cd, Zn, Al and Fe) contents and some soil physicochemical parameters were determined after wet digestion with Nitric acid/perchloric acid mixture. The digested samples and all the supernatants were analyzed for heavy metals using Atomic Absorption Spectrophotometer (Shimadzu AA7000 made in Japan) fitted with deuterium lamp for background correction. RESULTS: The heavy metal concentrations in the soils (mg/kg) ranged from 20.825 to 62.501; 7.25 to 11.806; 54.074 to 275.559; 10.861 to 40.139; 1835.751 to 2225.768; and 7166.724 to 11,601.940 for Pb, Cd, Cr, Fe, Al and Zn respectively. The Cr, Fe, Al, and Zn contents (mg/kg) in the plants samples were within the recommended limits but Cd levels were higher. CONCLUSION: The ecological and health risk assessments revealed contamination and high human health risk associated to Cd. Apart from Cd, other heavy metals under investigation in the soil posed low ecological risk. The target hazard quotient (THQ) values for Cd in the plants samples were all above one except for for Ocimum gratissimum, indicating that people consuming the plants cultivated in the vicinity of the dumpsite may experience adverse effects due to Cd toxicity.

Ecological and human health risk assessment of heavy metal contamination in soil of a municipal solid waste dump in Uyo, Nigeria.

The study assessed the levels of some heavy metals in soils in the vicinity of a municipal solid waste dumpsite with a view to providing information on the extent of contamination, ecological risk of metals in the soils and human health risk to the residents in Uyo. Soil samples were collected in rainy and dry seasons and analyzed for metals (Pb, Cd, Zn, Mn, Cr, Ni and Fe) using atomic absorption spectrometry. The concentrations of heavy metals (mg/kg) at the dumpsite in rainy season were Pb (9.90), Zn (137), Ni (12.56), Cr (3.60), Cd (9.05) and Mn (94.00), while in dry season, the concentrations were Pb (11.80), Zn (146), Ni (11.82), Cr (4.05), Cd (12.20) and Mn (91.20). The concentrations of metals in the studied sites were higher than that of the control site (P < 0.05). Pollution indices studies revealed that soil samples from dumpsite and distances from 10 and 20 m east of the dumpsite were highly polluted with cadmium. Ecological risk assessment carried out showed that cadmium contributed 98-99 % of the total potentially ecological risk. No probable health risk was observed as the total hazard index of all the metals was less than one. However, children were found to be more susceptible to heavy metal contamination than adult.

Studies of biosorption of Pb2+, Cd2+ and Cu2+ from aqueous solutions using Adansonia digitata root powders.

The potentials of Adansonia digitata root powders (ADRP) for adsorption of Pb(2+), Cd(2+) and Cu(2+) from aqueous solutions was investigated. Physico-chemical analysis of the adsorbent (ADRP) shows that hydroxyl, carbonyl and amino groups were predominant on the surface of the adsorbent. Scanning Electron Microscope (SEM) image revealed its high porosity and irregular pores in the adsorbent while the Energy Dispersive X-ray Spectrum showed the major element with 53.0% Nitrogen, 23.8% carbon, 9.1% calcium, 7.5% potassium and 6.6% magnesium present. The found optimal conditions were: initial concentration of the metal ions = 0.5 mg/L, pH = 5, contact time = 90 min, adsorbent dose = 0.4 g and particle size = 32 µm. Freundlich isotherm showed good fit for the adsorption of Pb(2+), Cd(2+) and Cu(2+). Dubinin-Radushkevich isotherm revealed that the adsorption processes were physisorption Cd(II) and Cu(II) but chemisorption with respect to Pb(II) ions. The kinetics and thermodynamic studies showed that Pseudo-second order and chemisorptions provided the best fit to the experimental data of Pb (II) ions only. Batch desorption result show that desorption in the acidic media for the metal ions were more rapid and over 90% of the metal ions were recovered from the biomass.

Dietary intake and health risk assessment of lead and cadmium via consumption of cow meat for an urban population in Enugu State, Nigeria.

The study assessed the dietary intake of lead and cadmium and health risk from consumption of various parts of cow meat by the urban population of Enugu State, Nigeria. Meat samples (n=150) comprising of muscle, liver, kidney, intestine and tripe were purchased from abattoirs in Nsukka and Enugu. The samples were dried, ground and two gram was digested with 3:2 HNO3:HClO4 v/v. The Cd and Pb concentrations were read with an atomic absorption spectrophotometer. The dietary intakes were estimated using a one week food frequency questionnaire administered to 755 subjects. The dietary intake of lead (µg/kg body weight/week) were in the following ranges; men [0.15 (kidney)-0.55(intestine)], non pregnant/non lactating women [0.16 (kidney)-0.62 (liver)], pregnant/lactating women [0.13 (kidney)-0.53 (intestine)], undergraduate students [0.12 (kidney)-0.62 (intestine)] and school children [0.29 (kidney)-1.16 (liver)]; cadmium: men [0.42 (liver)-1.21 (tripe)], non-pregnant/non-lactating women [0.53 (kidney)-1.20 (tripe)], pregnant/lactating women [0.43 (kidney)-0.90 (intestine)], undergraduate students [0.40 (kidney)-1.18 (tripe)] and school children [0.97 (kidney)-1.93 (tripe)]. The total dietary intakes of lead from the various cow meat parts by the groups were much lower than the provisional tolerable weekly intake (PTWI) guide line, but for cadmium, the intakes were quite appreciable when compared to the PTWI guideline while the intake for school children was very high, 113% of PTWI for the metal. The target hazard quotients were in the range of 0.05-0.10 for lead and 0.42-0.90 for cadmium. These values are less than one, indicating that the subjects are not exposed to any significant health risk via cow meat consumption.

Cadmium in locally grown rice (Oryza sativa) in Nigeria.

Cadmium levels were determined in locally grown rice samples in Nigeria and any potential risk involved in their consumption was assessed. The dried samples were digested with a 1:1 HNO3:HClO4 mixture and analysed with atomic absorption spectrophotometer (AAS). Mean cadmium values (mg/kg) were: Adamawa (0.50 ± 0.02), Benue (0.63 ± 0.05), Nasarawa (0.48 ± 0.10), Taraba (0.48 ± 0.10), Anambra (0.49 ± 0.09), Ebonyi (0.60 ± 0.08) and Enugu (0.59 ± 0.10). All samples exceeded the Codex Alimentarius maximum limit for cadmium in rice. The dietary intake for a 60 kg adult ranges from 235 to 309 µg/week in the northern region and 240-294 µg/week in the south-eastern region. The target hazard quotient (THQ) ranged from 0.54 to 0.71, which is less than 1, indicating that the population will not be exposed to a potential health risk from dietary cadmium. However, the measured cadmium levels in rice should be of concern.

Cadmium and lead levels in muscle and edible offal of cow reared in Nigeria.

The study assessed the concentration of cadmium and lead in the muscle, liver, kidney, intestine and tripe of cow in Nigeria. Results show that the ranges of detectable values of cadmium in mg/kg were 0.01-0.80 in muscle, <0.004-0.90 in liver, 0.10-1.12 in kidney, 0.01-0.90 in intestine and 0.01-1.10 in tripe while for lead, the ranges were <0.005-0.72 in muscle, 0.08-501.79 in liver, 0.04-44.89 in kidney, 0.01-108.02 in intestine and 0.01-127.90 in tripe. Cadmium was accumulated mostly in kidney while Pb accumulated more in liver and both were above international maximum permissible levels in most samples.