Potential ecological risk assessment of heavy metals associated with abattoir liquid waste: A narrative and systematic review

The article presents a narrative and systematic review of the potential ecological risk heavy metals associated with abattoir liquid waste for knowledge advancement. primarily focused on (i) An overview operations; (ii) Characteristics waste; (iii) Heavy in their health effects; (iv) Environmental impacts (v) Potential index (RI) methodology. These provided essential literature review. Using exclusive/inclusive criteria, 15 abattoirs that satisfied eligibility all located Nigeria, were used meta-analysis/meta-regression. Comparative multiple linear meta-regression analyses to quantify heterogeneity variances between based standardized RIs (SRIs; effect sizes) using eight tau (τ) estimators R metafor. effects three moderators─ number metals, metallic concentrations, relative distances conserved site (Gushaka-Gumti National Park), also analyzed. Sidik-Jonkman (SJ) estimator yielded realistic output, current research findings this estimator. Cochran statistic (QE) suggested an absence (p > 0.99). Between-study heterogeneities, quantified by H2 (1.05), I2 (4.76%), τ2 (0.0032 ± 0.0032 (SE)), latter measuring true size variance underlying data, low. moderators accounted R*2 95.73% total explanatory capacity model. beta coefficients intercept significant (p-values: 0.009–0.0004). While first two showed in-phase relations SRIs, third indicated out-of-phase relation. Such links suggest existence abattoir-environment interactive processes. Although are spatially distinct independent, operations evidence-based homogeneity posed high risks. Hence, environmental legislation should be strictly enforced while ensuring human settlements sited reasonably from abattoirs.