V3I5P28

Characterization, Ecological and Human Health Risk Assessment of Potentially Toxic Metals in Indoor Dust at Dangote Cement Plant Gboko Benue State, Nigeria

Otsapa Obikwu Jonathan^1*, Sesugh Ande¹, Rufus Sha’Ato¹, Tyover David Ortil²

Abstract

Exposure to heavy metals in indoor dusts is a serious public concern that is linked to a myriad of deleterious health outcomes. Indoor dust acts as a media for heavy metal deposition. This study aimed to assess the pollution, ecological and health risks of Mn, Cu, Fe, Pb, Ni, Cr and Zn in indoor household dust at Dangote Cement Plant, Gboko. Dust samples were obtained from 4 departments within the Plant namely; Civil, Production, Mines and Quality Control departments with a clean brush. After preparation, it was digested with aqua regia before analysis for selected metals by Atomic Absorption Spectrophotometry. The physicochemical parameters were also investigated. The results of the physicochemical analysis show the following values across the sampling sites pH 8.63±0.06 to 10.9±0.06, Electrical Conductivity (168±0.10 to 469±0.002) and Cation Exchange Capacity (15.0 to 9460) respectively. The heavy metal concentrations were generally lower than their WHO’s maximum permissible level in dust particles. The metal concentrations (mg/kg) were in the ranges of 0.115 to 0.444 (Mn); 0.166 to 0.944 (Cu); 6.12 to 9.24 (Fe); 15.0 to 28.0(Pb); 0.013 to 0.091 (Ni); 0.647 to 2.36 (Cr) and 0.476 to 1.65 (Zn). The results of ecological risk indexes of the heavy metals shows the Geoaccumulation index (Igeo) ranging from uncontaminated values to moderately contaminated values; Contamination factor were less than one (Cf < 1) suggesting that, the indoor dust in the company was not contaminated by the heavy metals; Enrichment factor showed no enrichment (EF < 2), indicating 1.5 suggests that the metals originate entirely from the Earth’s crust or natural processes, Iron was used as the reference metal, and Ecological risk index suggest low ecological risk (Er < 40) of the heavy metals across the sampling sites. The results showed that the CDI of the heavy metal content in indoor dust in Dangote Cement Plant followed the trend: Pb>Fe>Zn>Cr>Cu>Mn. Moreover, direct ingestion followed by dermal contact and inhalation were the most important exposure pathways of potentially toxic metals contaminated dust for both children and adults. The Hazard Quotient (HQ) and Hazard Index values for heavy metals were found to be below the safe threshold (HQ < 1). The result indicated that, the carcinogenic risk levels for children and adult generally fell within the acceptable range for carcinogens, which typically ranges from 10–6 to 10–4. However, indoor settled dust can be drastically reduced by frequent wet mopping and vacuuming, also by minimizing the use of windows during the harmattan season. This study provided baseline data for relevant bodies to use in monitoring and controlling pollution so as to protect workers from toxic metals.

Keywords:

Organochlorine pesticide; polychlorinated biphenyls; waste, dumpsite; gas chromatography; electron capture detector