Accumulation and toxicological risk assessments of heavy metals of top soils from markets in Owerri, Imo state, Nigeria

The assessment of human health risks associated with heavy metal contamination of frequently visited places, represents an important environmental study. Soil samples from Ekeonunwa Market (EM), New Market (NM), Nkwo-Orji Market (NOM), Timber Market Umunwonyeali (TMU), Timber Market Naze (TMN), Amakohia Market (AM), Worldbank Market (WBM), and Relief Market (RM) were evaluated for Ag, Co, Ni, Hg, As, Cu, Zn, Cr, Cd, and Pb contents using an Atomic Absorption Spectrophotometer. The Ag contents were above the baseline and control values in all the study sites except at NM and WBM that were below detection levels. The Co, Ni, Pb, and Cr levels were significantly below the baseline values at all the sites while the Hg and Zn levels at all sites assessed were not significantly different from the baseline values. The models employed to assess the levels and sources of pollution showed for Igeo, that NOM, and AM were severely polluted with Ag, and EM severely polluted with Ag and Cu, while NM was moderately polluted with As, and NOM slightly polluted with Hg. Hg contributed the highest contamination at the sites assessed while Cr and Pb were among the metals that least contributed to contamination. Results for the Enrichment Factor showed that only Co at AM, Ni and Hg at NM, Cd at WBM, and Pb at TMN and AM, resulted from natural sources while other heavy metal depositions were of anthropogenic origin. The average Daily Intake of the metals at all the study sites was below the reference doses while the Total Hazard Index at all the sites was still within the acceptable standards. This study has provided the scientific basis for the regular assessments of the markets, and recommends the development of imminent strategies to halt further degradation of these environments.