Heavy Metal Contamination Levels in Clams (Galatea paradoxa, Born 1778) and Surface Sediments from Mono River Estuary, Togo, and its Health Implications

Heavy metal pollution in aquatic ecosystems is one of the most important threats of human health and food chain. Thus, in this study, the level of Cd, Fe, Hg, Mn, Pb and Zn accumulation in surface sediments and in Galatea paradoxa, were investigated to estimate their potential health risks via consumption to residents alongside the Mono river, Togo-Benin border. Samples were collected at two fishing areas and analyzed using flame atomic absorption spectrophotometry Moreover, the likely health risks developed as a result of human contamination by heavy metal through clam consumption was also assessed using target hazard quotient (THQ) and hazard index (HI). The mean maximal metal concentrations (μg/g dw) were as follows: Fe (25624) > Mn (1176.0) > Zn (23.29) > Pb (4.67) > Hg (0.038) in silty sediments and Fe (15692) > Mn (654.78) > Zn (12.53) > Pb (2.42) > Hg (0.034) in sandy sediments. Cd content were all below the detectable limit. When compared against some consensus-based sediment quality guidelines (TEL, ERL, AFNOR), it was observed that all the concentrations, excluding Fe levels in the samples, were lower than reference values. Similarly, computed PLI was less than 1 indicating that the lower tidal parts of the Mono were unpolluted. The accumulation pattern of studied trace metals in the clams followed a slightly different trend from that found in the sediments (Fe>Zn>Mn>Hg>Pb>Cd). Fe (1353 ± 162 μg/g dw) and Zn (51,8 ± 8.9 μg/g dw) content in whole tissues of G. paradoxa were well above the maximum concentration allowable by food safety criteria. In contrast, Cd (0.097 mg/kg dw), Hg (0.24 mg/kg dw) and Pb (0.18 mg/kg dw) content were very low. Computed THQ values were all below 1, with highest results found in the small size clams regardless of the heavy metals. The HI values indicate that none of the analyzed heavy metals may pose serious risk to consumers through the clams studied. The highest risk was posed by small clams, followed in decreasing order by medium and large clams. We therefore suggest that the clams taken from main fishing locations at Mono river are safe to eat. Keywords: Heavy metals, Sediment pollution, Galatea paradoxa, Human health, Mono River DOI: 10.7176/JBAH/11-4-06 Publication date: February 28th 202

Évaluation et risques sanitaires de la bioaccumulation de métaux lourds chez des espèces halieutiques du système lagunaire togolais

Bioaccumulation of cadmium, lead and arsenic in fish and bivalves commonly caught in Togo lagoon system was evaluated in order to estimate the health risks associated with their use. The results showed that all analyzed fish are contaminated. The mean levels of cadmium (0.33 mg/kg for Caranx hippos to 0.98 mg/kg for Hemichromis fasciatus), lead (1.17 mg/kg for Liza falcipinnis to 2.89 mg/kg for Lutjanus goreensis ) and arsenic (9.41 mg/kg for C. hippos to 22.54 mg/kg for Pomadasys jubelini) are higher than the standards set by the WHO. Bioconcentration Factors (BCF) ranged from 6.94 to 20, 36 for Cd, 9.58 to 23.67 for Pb and 2.30 to 5.52 for As. As far as bivalves are concern, average grades indicate a high concentration of arsenic (56.06 mg/kg for Senilia senilis and 47.76 mg/kg for Crassostrea gasar) followed by lead (2.83 mg/kg for S. senilis and 2.95 mg/kg for C.gasar) and finally cadmium (0.97 mg/kg for S. senilis and 0.83 mg/kg for C.gasar). BCF ranged from 16.6 to 19.14 for Cd, 39.86 to 41.55 for Pb and 19.10 to 34.42 for As. In addition

Etat de la contamination en éléments traces des sédiments du Lac du barrage hydroélectrique de Nangbéto (Togo)

The Nangbéto hydroelectric dam lake, which is a spillway for agricultural input residues, urban and industrial effluents present in the Mono basin, is exposed to all forms of pollution. The aim of this work is to estimate the content of seven trace elements present in the sediments of the aforementioned lake in order to assess the ecological risk incurred by the aquatic biocenosis and therefore by man. Forty-two sediment samples (21 per season) are realized in different areas of the Lake. Cd, Pb, Ni, Cu, Cr, As and Hg are measured out in the sediments by the flame atomic absorption spectrophotometer in these pre-mineralized samples. The results show average contents varying from the lowest level 0.04 mg / kg for Hg to the highest 12.15 mg / kg for Cu in the rainy season and from 0.03 mg / kg for Hg and for As to 9.14 mg/kg for Cu in the dry season. All of these values are below Canadian sediment quality standards. The strongest average geoaccumulation indices (Igeo) are obtained for Pb with values less than 2. The mean values of the contamination factor (FC) are less than 1. The mean indices of contamination (Im) are less than 2, threshold d 'an onset of polymetallic contamination. The ecological risk (Ri) in relation to the contamination of the sediments of the Lake with trace elements is low in any season (Ri <40) and this implies a low risk of contamination of the biocenosis. However, the present study only deals with metallic trace elements. It does not take into account other pollutants, nor the potential "cocktail" effects between them. Additional work should therefore be continued in this direction to consolidate the low risk recorded for the biocenosis.Le Lac du barrage hydroélectrique de Nangbéto qui constitue un déversoir des résidus des intrants agricoles, des effluents urbains et industriels présent dans le bassin du Mono est exposé à toutes formes de pollution. Le but de ce travail est de quantifier les teneurs de sept (7) éléments traces dans les sédiments dudit Lac afin d’évaluer le risque écologique encouru par la biocénose aquatique et partant par l’homme.Quarante-deux (42) échantillons de sédiments (21 par saison) sont échantillonnés dans différentes zones du Lac. Le Cd, Pb, Ni, Cu, Cr, As et Hg sont dosés dans les sédiments par le spectrophotomètre d’absorption atomique à flamme dans ces échantillons minéralisés. Les résultats montrent des teneurs moyennes variant de la plus faible teneur 0,04mg/kg pour le Hg à la plus forte (12,15mg/kg) pour le Cu en saison pluvieuse et de 0,03 mg/kg pour le Hg et pour l’As à la plus forte (9,14 mg/kg) pour le Cu en saison sèche. Toutes ces valeurs sont inférieures aux normes canadiennes de qualité des sédiments. Les plus forts indices de géoaccumulation (Igeo) moyens sont obtenus chez le Pb avec des valeurs inférieures à 2. Les valeurs moyennes de facteur de contamination (FC) sont inférieures à 1. Les indices moyens de contamination (Im) sont inférieurs à 2, seuil d’un début de contamination polymétallique. Le risque écologique (Ri) par rapport à la contamination des sédiments du Lac en éléments traces est faible en toute saison (Ri < 40) et cela implique un faible risque de contamination de la biocénose. La présente étude ne porte toutefois que sur les éléments traces métalliques. Elle ne tient compte ni des autres polluants, ni des effets "cocktail" potentiels entre eux. Un travail complémentaire devra donc être poursuivi dans ce sens pour consolider le faible risque enregistré pour la biocénose

Physico-chemical quality of ashes post-incineration and waste from laboratory automaton biochemistry, hematology and serology in Togo

Biochemistry, hematology and serology laboratories produce very heterogeneous discharges capable of polluting water, soil and the environment. The aim of this study is to evaluate the physico-chemical quality of the ashes, effluents and the range of equipment that produce the much effluent and pollutions.This is a descriptive and cross-sectional study of 82 laboratories followed by the sampling of effluents from automatons. The physico-chemical parameters and trace elements are determined according to French Standardization Association (AFNOR) standards and used atomic absorption spectrometers and molecular absorption spectrometers. The Mindray hematology automaton is used for 64.7% and 81.5% of the cans are used to collect waste. Semehow 77.8% of discharges are released into sinks without adequate treatment in 42.6% of cases. Chemical analyses show that trace elements (TE) levels in effluents range from 5.89 ± 0.21 to 105.80 ± 0.96 μg/L for Arsenic; from 5.62 ± 0.34 to 6.53 ± 0.49 μg/L for Cadmium; 0.70 ± 0.01 to 10.63 ± 1.17 μg/L for Mercure and 35.72 ± 1.88 to 61.98 ± 5.15 μg/L for Plomb. pH ranges from 7.17 ± 0.65 to 8.3 ± 1.35 with total dissolved salts (TDS) range from 3260.20 ± 401.68 to 17117.41 ± 265.37 mg/L. All averages of contamination indices (CI) and polymetallic contamination indices (PCI) for post-incineration ashes are greater than 1.5 with the exception of Hg (0.22). For effluents, in addition to polymetallic contamination indices (PCI), CI in hematology effluents (1.09), all CI are less than 1. Hematology effluents have a lower pH and are much more mineralized and concentrated in trace elements while those from biochemistry and serology appear to be similar. However, the effluents of Biochemistry and Serology are more basic and concentrated in Suspended Solids with higher values obtained in Biochemistry. Although the physico-chemical parameters comply with WHO standards, discharges from automatons deserve appropriate treatment before their disposal