Multivariate analysis of potential health hazards of manganese via dietary exposure of widely consumed vegetables amended with municipal solid waste

Abstract

Improper disposal of municipal solid waste in metropolitan and semi-urban regions presents a significant global challenge, contributing to heavy metal contamination and associated health risks. This study assessed the ecological and anthropogenic health risks of manganese contamination resulting from the dietary intake of vegetables cultivated using municipal solid waste amendments in Sargodha, Pakistan. Commonly consumed vegetables (n = 15) were grown in pots over two years (2022-2023) with soil and municipal solid waste mixtures (100/0, 75/25, 50/50, and 25/75; w/w), designated as T0, T1, T2, and T3, respectively. Manganese concentrations were analyzed in soil (n = 600), vegetables (n = 600), and residents' blood serum (n = 240) using an atomic absorption spectrophotometer. Manganese levels ranged from 15.49 to 18.97 mg kg⁻¹ in soil, 0.508-5.483 mg kg⁻¹ in vegetables, and 0.0015-0.0043 mg L⁻¹ in serum. The highest manganese concentration was detected in S. oleracea during T3 in Year 2, while the lowest was observed in C. sativus during T0 in Year 1. Although these concentrations were within FAO/WHO permissible limits, the elevated manganese levels in S. oleracea may still pose a moderate risk if consumed frequently, whereas C. sativus presents a negligible risk. A strong positive correlation was observed between vegetable samples from Year 1 and Year 2 (r = 0.93, p < 0.01), indicating a significant relationship across the two years. The PCA results indicate that S. oleracea (PC1 = 3.9645) and C. sativum (PC1 = 2.6912) exhibit strong positive associations, while C. sativus (PC1 = - 1.3125) and C. vulgaris (PC1 = - 1.0466) show strong negative correlations. PC2 values were relatively lower, indicating weaker associations across species. The computed indices (BCF, PLI, EF, EF%, HRI, DIM, Igeo, EDI, EDD, and THQ) were consistently below the threshold of 1, indicating negligible concentrations in both soil and vegetables, thereby confirming the safety of the local population upon ingestion. To mitigate the potential risk of manganese accumulation from MSW, implementing regulated composting practices, adopting soil amendments to minimize metal uptake, and promoting public awareness regarding safe vegetable consumption are essential. Furthermore, continuous monitoring and the establishment of strict regulatory guidelines are crucial to prevent excessive heavy metal buildup in the food chain.

Keywords: C. sativus; S. oleracea; Daily intake; Dietary intake; Implications; Nutrients; Population; Urban area.