Coastal Dump Sites in the Lagos lagoon and toxicity of their leachate on brackish water shrimp (Palaemonetes africanus)

An assessment of the coastal dumpsites and their impacts on shrimp mortality in the Lagos lagoon was investigated. The study involved a census of dumpsites in the major sections of the coastline associated with anthropogenic activities, followed by specific bioassay to determine the acute toxicity of leachates from one of the dump sites. Our investigations revealed that there were 8 major dumping localities with approximately 28 dumpsites generated mostly by deliberate efforts and in some cases by tidal activities which litter the coastline. The major dumping localities were Abule Eledu, Ebute Ilaje, Oworonshoki, Ibese, Offin, Off Ozumba Mbadiwe Road, Iddo and Okobaba. The largest number of dumpsites was recorded at Owonronshoki and Ibeshe, each with 19% of the total dumps while the least number was recorded at Off Ozumba Mbadiwe Road (4%). The major waste categories include fabrics (worn clothes), plastics, wood and wood shavings, glass, metallic objects as well as paper and packaging materials. The acute toxicity assessment of leachates from a dumpsite at Abule Eledu indicated moderate toxicity to brackish water shrimps (Palaemonetes africanus) with 96 hr LC50 value of 93.59% (935.9ml/L). The leachate was found to be high on biological and chemical oxygen demand, conductivity, total dissolved solids, nitrate and sulphate. The findings from this study indicate widespread and unregulated practice of coastal solid waste dumping with potential effects on water quality and biota. The need for improved waste management system in the City of Lagos was discussed. Keywords: Aquatic Pollution; Waste Management; Environmental Policy; Solid Waste; Waste Recyclin

Comparative Ecotoxicological Assessment of Acetaminophen and Diclofenac using Freshwater African Catfish Clarias gariepinus (Burchell 1822)

The use and abuse of analgesics, commonly referred to as painkillers is on the rise globally. This study examined the acute toxicity and sub-lethal effects on liver function (ALT, AST, ALP) and anti-oxidative stress enzymes of the African Catfish, Clarias gariepinus, exposed to two analgesics, acetaminophen and diclofenac. The fingerlings (4 weeks old), were exposed to high concentrations of both analgesics to determine their acute toxicity of a 96 h period. The results indicated that diclofenac was approximately 500 times more toxic to the catfishes with a 96 h LC50 of 2.6 mg/L compared to 1283.6 mg/L in those exposed to acetaminophen. Another batch of the catfishes was subsequently exposed to two sub-lethal concentrations (1/10th 96 h LC50 and 1/100th 96 h LC50) of both compounds for 28 days. The result of the sub-lethal assessment indicated that the responses were not always dose-dependent. The liver function enzyme assessments indicated a varied result with AST values slightly lower than control while ALP values were all higher in the exposed groups than the control. Only catfishes exposed to 1/10th 96h LC50 diclofenac showed significant inhibition (P<0.05) of ALT enzyme activities compared to control. The activities of the anti-oxidative stress enzyme catalase were lower in those exposed to acetaminophen compared to control and this was also the case for glutathione-S- transferase (GST) activities for exposures to both concentrations of both analgesics. The findings point to the need for the inclusion of pharmaceuticals in our national effluent quality standards so as to mitigate potential harm to aquatic life.Keywords: Acetaminophen, diclofenac, toxicity, catfis

Estimation of pesticide mixture interaction in Nile tilapia (Oreochromis niloticus) using survival analysis

The acute toxicity of the pesticides atrazine, mancozeb, chlorpyrifos and lambda-cyhalothrin, acting singly and jointly, was assessed on Nile tilapia (Oreochromis niloticus) fingerlings. Median lethal concentration (LC50), median lethal time (LT50), and mixture interaction were estimated, whereas survival analysis was used to model time-todeath. The most toxic single and joint mixture was lambda-cyhalothrin and chlorpyrifos-lambda cyhalothrin, respectively. The risk of death (RoD) of fingerlings exposed to 9.22 mg l−1 atrazine-mancozeb mixture was 1.76 times higher than fingerlings exposed to 9.0 mg l−1 atrazine (p > 0.05). However, RoD of fingerlings exposed to 9.95 mg l−1 atrazine-chlorpyrifos was 5.59 times higher than fingerlings exposed to 9.0 mg l−1 atrazine (p < 0.01). The risk of death of fingerlings exposed to 20.8 mg l−1 atrazine-lambda cyhalothrin was 2.81 times higher than 21.0 mg l−1 atrazine. The toxicity of 2.3 mg l−1 mancozeb-chlorpyrifos was 254.25 higher than 2.2 mg l−1 mancozeb (p < 0.01). Fingerlings exposed to 4.33 mg l−1 mancozeb-lambda cyhalothrin and 0.177 mg l−1 chlorpyrifos-lambda cyhalothrin mixture were 0.02 and 0.14 times less likely to die than those exposed to 4.8 mg l−1 mancozeb and 0.17 mg l−1 chlorpyrifos, respectively (p < 0.01). Atrazine-mancozeb, atrazine-chlorpyrifos, atrazine-lambda cyhalothrin, and mancozeb-chlorpyrifos interaction were synergistic, and their relative risk was >1. Both mancozeb-lambda cyhalothrin and lambda-cyhalothrin-chlorpyrifos mixtures were antagonistic, and their relative risk was less than 1. Survival analysis can show interaction in complex pesticide mixtures

Comparative acute toxicity and oxidative stress responses in tadpoles of Amietophrynus regularis exposed to refined petroleum products, unused and spent engine oils

The relative acute toxicity of refined petroleum (diesel, kerosene and petrol), unused and spent engine oils as well as their abilities to alter the activities of superoxide dismutase (SOD) and cause lipid peroxidation in tadpoles of the common African toad, Amietophrynus regularis were evaluated.  After 48 h of exposures, kerosene was found to be the most toxic (LC50= 4930 mg/L) while the least toxic was unused engine oil (LC50 = 7777 mg/L). However, by 96 h of exposure, spent engine oil was found to be the most toxic (LC50 = 2915 mg/L) while unused engine oil remained the least toxic (LC50= 7353 mg/L). Further, assessment of oxidative stress markers was conducted using sub lethal concentrations of the test compounds (1/100th 96 h LC50). There was significant inhibition of SOD in exposed tadpoles compared to the control (P<0.05) with the least activity recorded in tadpoles exposed to petrol, while unused engine oil recorded the highest. The results of the lipid peroxidation assay, determined by measuring the levels of malondialdehyde (MDA) indicated significantly higher levels in the exposed individuals compared to the control. Unused engine oil caused the highest level of MDA production while diesel induced the least level. Tadpoles exposed to diesel, kerosene, petrol and spent engine oil exhibited consistent responses among the three test parameters, however inconsistent responses were observed in tadpoles exposed to unused engine oils. The relevance of the comparisons in biomarker selection and ecotoxicology were discussed.Keywords: Petroleum products, toxicity indices, tadpoles, oxidative stress.African Journal of Biotechnology, Vol 13(45) 4251-425