RESUMEN
BACKGROUND: In addition to improving soil fertility and crop production, earthworms have been found to be useful in the removal of contaminants from soil, known as vermiremediation. Previous studies on vermiremediation have focused primarily on organic wastes, with relatively less attention paid to inorganic contaminants. In addition, some basic terms used in environmental health studies have often not been properly clarified. OBJECTIVES: The present study is a review of the state of the literature on the effectiveness of using earthworms to remediate organic and inorganic (metal) soil contaminants. Earthworms' actions in remediation of organic and inorganic contaminants are described. Some terms that are used interchangeably in environmental health are clarified. The challenges and limitations of vermiremediation are highlighted. METHODS: A systematic literature search was conducted to access online academic publications indexed in Google Scholar, PubMed, Scopus, Clarivate Analytics (Web of Science), ScienceDirect, ResearchGate and Springer Link. A total of 165 publications on the subject matter were accessed, out of which 47 were used for the review. DISCUSSION: Empirical and theoretical information from the literature showed evidence of the significant contributions of earthworms to the removal of soil organic contaminants and metals. Earthworms indirectly facilitate the conversion of organic contaminants by promoting microbial and enzyme activities. Some organic contaminants are directly taken up through dermal and intestinal absorption and accumulated by preferential sequestration in sub-organismic and tissue fractions of earthworms. Metals are directly removed and accumulated by the mechanism of detoxification and sequestration, via metallothioneins induction. The terms 'contaminants' and 'pollutants' have different meanings and should not be used interchangeably. Although vermiremediation presents an ideal clean-up technique, it is limited in application to only mildly contaminated soil environments. Ethical concerns should not pose a serious issue because vermiremediation simply takes advantage of earthworms' natural soil-conditioning abilities. Many vermiremediation processes, especially of organic wastes, are harmless to earthworms, improving the soil for their growth and survival. CONCLUSIONS: Vermiremediation presents a good long-term biological option to clean up mildly contaminated soil. It may be deployed as a secondary measure to rid the soil of residual contaminants after applying physicochemical remediation techniques to an overtly polluted soil environment. COMPETING INTERESTS: The authors declare no competing financial interests.
RESUMEN
The occurrence of conflicting reports on the improvement of male reproductive function among humans fed diet containing the seed of Mucuna pruriens (MP) have raised a major concern in Nigeria. We assessed the effect of MP seed powder on the reproductive function in 32 adult male albino rats randomized to 4 groups of 8 rats each for 8 weeks. Group 1 (control) was given standard rat chow while groups 2, 3 and 4 were fed diets containing MP seed powder at 0.75 g, 1.5 g and 2.25 g respectively. Serum level of follicle stimulating hormone, testosterone, luteinizing hormone, oxidative stress markers in the testis, epididymal sperm quality and cytoarchitectural structure of the testis were monitored using standard methods. Significant improvements (p < 0.05) in the serum levels of all the hormones, testicular antioxidant defence, epididymal sperm quality without testicular degenerative changes were observed in group 2 compared to other groups. Oxidative stress, severe degenerative architectural lesions in the testis as well as significant reductions (p < 0.05) in epididymal sperm count, percentage motility and significant (p < 0.05) increased in abnormal sperm cells were observed in group 4. MP seed enhances reproductive function in male rats only at a dose level of 0.75g. A dose value higher than 0.75 g may be toxic to the male reproductive system.