DETERMINATION OF LEAD (Pb) LEVELS IN SELECTED MINING COMMUNITIES IN ZAMFARA STATE – NIGERIA

DETERMINATION OF LEAD (Pb) LEVELS IN SELECTED MINING COMMUNITIES IN ZAMFARA STATE – NIGERIA

Abstract:

In 2010, the world’s attention was drawn to Zamfara State, Nigeria following the ‘unprecedented’ death reported (particularly of children) as a result of lead poisoning in the process of small scale gold mining of lead-rich ore using rudimentary tools. This study was aimed at a wholistic assessment of lead levels in the affected communities. Lead (Pb) levels were determined from samples of residential compound soil, underground and surface water, common grains (sorghum, millet and maize), human and animal blood samples collected from ten selected villages (Bagega, Kadauri, Kawaye, Kwali, Magami, Sunke, Tsunami/Unguwan Danbaba, Tungar-Guru, Tungar-Kudaku and Yargalma) among the mining, communities for analysis. Samples collected were carefully handled, preserved, and digested using adopted and validated methods of analysis for lead using Atomic Absorption Spectrophotometry (AAS) technique. Results obtained from the analysis were subjected to statistical analysis using GraphPad Prism 6 analytical package. Results indicated that the mean lead concentration in residential soil ranged from 12.44 ± 3.23 to 757.69 ± 645.35 mg/Kg. Apart from Tungar-Guru, with the highest mean lead concentration in soil, the rest of the villages were below the US-EPA threshold level (400 mg/Kg) of concern. Mean lead concentration in common grains indicated that, apart from the millet sample from Kwali with the highest mean lead concentration of 72.07 ± 57.36mg/Kg, the mean lead concentration of all the grains from other locations ranged from 5.56 ± 2.02 to 28.18 ± 5.93 mg/Kg. The results indicated that the mean lead concentration of all the grain samples have exceeded the WHO threshold level of concern for the WHO (3.0 μg/Kg). Mean Blood lead levels (BLLs) for children within the age ranged of 2 – 6 years in the mining communities ranged from 32.20 ± 7.34 – 157.60 ± 9.11 μg/dL. With the exception of Kwali, Tungar-Kudaku and Yargalma with BLLs of 32.20 ± 7.34, 35.80 ± 8.10 and 41.60 ± 4.70μg/dL respectively, children in other villages have blood concentration exceeding the threshold level (45 μg/dL) for chelation therapy in children. The mean blood lead concentration in adults in the selected mining communities ranged from 37.80 ± 5.94 to 146.40 ± 27.40 μg/dL. Overall, children from Kwali have the lowest blood lead concentration and the highest from Bagega. Both children and adults blood lead levels have exceeded the threshold levels of concern for lead poisoning for both CDC (5μg/dL) and WHO (10μg/dL). The mean blood lead concentration of all the animals/livestock involved in the study ranged from 52.25 ± 5.19 to 101 ± 9.07μg/dL. Goats and chickens from Sunke and Tsunami have the lowest mean lead concentration (52.25 ± 5.19 μg/dL) while Yargalma has the highest (101 ± 9.07μg/dL). Blood lead concentration in all the animals were above the WHO acceptable level (10μg/dL). Underground (UW) and surface water (SW) were contaminated with lead. The mean lead concentration for underground water ranged from 187.67 ± 99.05 to 1273.00 ± 444.00 μg/L. For the surface water, the mean lead concentration ranged from 413.00 ± 202.43 to 4235.00 ± 121.75μg/L. These results indicated that, the mean lead concentration for both underground and surface water samples have exceeded the WHO and FAO/WHO acceptable guidelines of 10μg/L and 100μg/L for underground and surface water respectively. Statistical analysis indicated that there was no significant difference (P < 0.05) in lead concentrations in residential soil within each community but significantly different (P < 0.05) across communities. However, lead concentrations in common grains were not statistically significant (P < 0.05) within each community and across the communities, except for the millet from Kwali that was significantly higher. Results also indicated that blood lead levels in both children and adults within each community was significant (P < 0.05), however, comparison across communities indicated no statistical significance (P < 0.05) across most of the communities. In animal blood samples, blood lead concentration was significant (P < 0.05) within community and across communities. Similarly, significant (P < 0.05) differences exist in underground water samples within community, while in surface water samples it was not significant. Apart from compound residential soil in few remediated villages, lead concentrations in all other samples were still significantly (P < 0.05) above internationally threshold levels of concern. Public education, remediation process, chelation therapy and safe mining practices must be fully implemented to bring the lead poisoning under control and concentration of lead levels in these communities below the threshold level of concern in order to save future generation of manpower from extinction or permanent incapacitation.

DETERMINATION OF LEAD (Pb) LEVELS IN SELECTED MINING COMMUNITIES IN ZAMFARA STATE – NIGERIA