The occurrence of acetaminophen, amoxicillin, diclofenac and methylparaben in Lagos and Ologe Lagoons was investigated by random sampling of the water bodies during rainy and dry seasons. Samples analysis was carried out using high performance liquid chromatography. For the two seasons, the mean environmental concentrations of acetaminophen in Lagos and Ologe Lagoons were 0.075 µg/L and 1.233 µg/L respectively. The mean environmental concentration of amoxicillin in Lagos Lagoon was 0.008 µg/L while 0.003 µg/L was the mean value in Ologe Lagoon. Diclofenac occurrence in Lagos Lagoon had a mean value of 0.136 µg/L while 0.519 µg/L was recorded in Ologe Lagoon. The environmental concentration of methylparaben in Lagos Lagoon was 0.453 µg/L while its means concentration in Ologe Lagoon was 0.089 µg/L. From the results, the environmental concentrations of acetaminophen and diclofenac in Ologe Lagoon were higher than their level of occurrence in Lagos Lagoon. However, the levels of occurrence of amoxicillin and methylparaben in Lagos Lagoon were higher than their environmental concentrations in Ologe Lagoon. Methylparaben was the most frequently detected in the water bodies with 87.5% detection frequency. This was followed by diclofenac with 75%. Also, 50% of the water samples analysed contained acetaminophen while amoxicillin had the least (37.5%) frequency of occurrence. The study established that there are active pharmaceuticals compounds and excipients present in the Nigerian aquatic environment which are micropollutants of emerging environmental concerns and of significant ecological risk. Therefore, there is need for environmental regulators to make concerted efforts towards environmental monitoring of this group of pollutants.

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 (1/10 th 96 h LC50 and 1/100 th 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 1/10 th 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.

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Oil industry activities often involve the cleaning and replacement of pipelines, usually resulting in the discharge of effluents into waterbodies. The toxicity of de-oiling effluent from a decommissioned crude oil pipeline in the Niger Delta region of Nigeria was assessed using the brackish water shrimp Palaemonetes africanus in a 96 h laboratory bioassay. On the basis of the computed 96 h LC 50 , the effluent showed a significant dose-dependent relationship in its toxicity between 24 and 96 h of exposure. The 96 h LC 50 was 4.6 times more toxic than the 24 h LC 50 , indicating that the toxicity of the effluent increased over the study period. Besides crude oil and refined petroleum products, which are often the major concern for regulators, there is a need for the proper enforcement of standards and safe limits for effluents prior to discharge so as to protect sensitive marine species.