Human Health Risk Assessment of Heavy Metal Contamination in New Calabar River.

Concentration and human health risks of heavy metals (Pb, Cu, Cr, Cd, As, Ni) in water, sediment, crab (Tympanotonus fuscatus) and periwinkle (Callinectes amnicola) were assayed in New Calabar River, Nigeria. Results revealed that concentration (mg/L) of the metals in water in the two seasons studied, ranged from 1.1E-2 ± 1.0E-3…for Cd to 2.90 ± 0.03…for Cu. In sediment, the concentration (mg/kg) ranged from 1.1E-2 ± 1.0E-3…for As to 5.17 ± 0.04… for Ni. In biota, the concentration (mg/kg) ranged from 0.01…for As in crab to 19.22…for Cu also in crab. Estimated human health risk from the metals contamination due to consumption of biota gave each of HQ and HI as < 1, indicating no risk except at Agip's sample location where HI was > 1. Estimated human health risk due to dermal absorption through swimming, indicated no risk as each of HQ and HI was < 1. These make the river unpolluted except at Agip's sample location.

Ecological risks of phenolic endocrine disrupting compounds in an urban tropical river.

The distribution of emerging organic contaminants in drinking water sources in Africa is a subject with very scanty data and information. In order to fill knowledge gaps, we report here the distribution and potential ecological risks of three phenolic compounds (bisphenol A (BPA), 4-nonylphenol (NP), and 4-tert-octylphenol (OP)), which have been previously identified to have the potential of endocrine disrupting activity, in surface water and sediment of the New Calabar River. The compounds were quantified using GC-MS. At all sampling sites, a similar concentration pattern of BPA > NP > OP was recorded, with the exception of Choba sampling station in which the levels of these endocrine disrupting compounds were low or undetectable. The levels of BPA in surface water ranged from 1.20 to 63.64 µg/L, whereas those of NP and OP ranged from < 0.20 to 2.15 µg/L and from < 0.10 to 0.68 µg/L, respectively. For sediments, measured levels were from 1.20 to 66.57 µg/kg for BPA, from < 0.35 to 3.37 µg/kg for NP, and from < 0.13 to 0.90 µg/kg for OP. Risk quotients (RQs) assessed for some sensitive organisms (algae, Daphnia magna, and fish) were above 1 for BPA and NP, whereas RQs for OP were below 1. This implies that BPA and NP at the levels detected could have potential risks to the sensitive organisms considered, but low risk for OP.