Lagoons are large bodies of water that provide essential economic and ecosystem services such as fishing, erosion protection, transportation, as well as water for domestic, industrial, and agricultural use, among others. Unfortunately, municipal, agricultural, and industrial waste are often dumped in lagoons, polluting the water and predisposing humans and aquatic organisms to environmental and health hazards. This calls for regular monitoring of lagoons worldwide. This study assessed the water quality of Epe lagoon in Lagos State, Nigeria, with regard to heavy metal contamination. Water samples obtained at three settlements (Epe, Ejinrin, and Agbowa) along the lagoon were treated and subjected to heavy metal analysis using standard protocols. The heavy metals analysed were lead (Pb), copper (Cu), nickel (Ni), cadmium (Cd), and chromium (Cr). The chronic daily intake (CDI), chronic dermal contact (CDC), hazard quotients (HQ), heavy metal index (HMI), and probability of cancer risk (PCR) of the heavy metals were also calculated. The results revealed that the water samples from the three locations contained non-permissible levels of Pb, Cu, Ni, Cd, and Cr. The CDI, CDC, and HQ of the heavy metals via ingestion and dermal contact were within the recommended limits, except for Pb. Meanwhile, the HMI and PCR of all the heavy metals exceeded the permissible limits. The results obtained suggest that Epe lagoon’s water is contaminated with heavy metals and thus poses health hazards. Consequently, there is a need for heavy metal remediation and control in the lagoon.

Background: Psidium guajava (guava tree) is widely used in Nigeria to treat diseases. However, a paucity of information exists on the safety of the plant. Objectives: This study determined the safety of P. guajava leaves collected in Birnin Kebbi, Nigeria. Methods: The methanolic extract of the plant’s leaves was subjected to phytochemical and heavy metal screening using standard protocols, and thereafter, subjected to a cytogenetoxicity test using the Allium cepa toxicity assay. Twenty-one A. cepa bulbs divided equally into seven groups were grown over beakers containing distilled water (negative control), formaldehyde (positive control), as well as 0.25, 0.5, 1, 2, and 4 g of the extract, respectively, for five days. The root-tip cells of the A. cepa bulbs were treated and then examined for chromosomal aberrations. Results: The phytochemical screening revealed high levels of saponins, and moderate levels of phenols, tannins, and flavonoids, while quinones and terpenoids were sparingly available. The heavy metal analysis showed non-permissible levels of cadmium and zinc, while two other tested heavy metals (lead and copper) were undetected. Except for the A. cepa treated with 0.25 and 0.5 g, the extract induced dose-dependent root growth and mitotic index inhibition (P<0.05). The extract also induced cytogenetic effects, mainly sticky, vagrant, and fragmented chromosomes as well as anaphase bridges. Conclusions: It can be inferred from the results that low to medium doses of the extract are safe but may elicit harmful effects at high doses. Advice from a phytomedicine or phytotherapy expert should be sought before using it.