ABSTRACT
A comprehensive ecological and human health risk assessment of heavy metal contamination resulting from nickel and chromite mining activities in Santa Cruz, Zambales, Philippines are hereby presented in this study. Contaminants including cadmium, chromium, cobalt, iron, lead, and nickel were analyzed in various ecosystem compartments, such as rice field soil, dust particles, and rice grains. The risk assessment revealed elevated concentrations of heavy metals, posing potential threats to both environmental health and human well-being. The rice field soil samples exhibited varying concentrations of heavy metals, with Rice Field Soil L2 showing particularly high levels of cadmium, chromium, and iron. More also, the dust particles analyzed show distinctive contamination patterns across locations, indicating the influence of different mining sites on heavy metal dispersion. Guiguis L1 and SC Dust L2 stood out with significant concentrations of several metals. Similarly, the composite Rice Grains L1 displayed notable concentrations of chromium, iron, and nickel.
The hazard Index (HI) values suggested a heightened risk of non-cancer health issues, especially in areas with high dust deposition, while the Cumulative Cancer Risk (CCR) values indicated an astronomical increased risk of cancer, emphasizing the potential long-term health implications of heavy metal exposure in the locality. On implementing the Pearson’s Correlation, the correlation analysis revealed strong positive correlations between certain metals, signifying potential common sources with Nickel and chromium displaying a particularly noteworthy associations. Hence, we propose a Rationality-Based Mining Decision Support Model which utilizes Cost-Benefit Analysis (CBA). It is argued that this novel CBA model should integrate environmental, health, and economic data; wherein the costs associated with contamination remediation, health treatments, and ecosystem services valuation, providing a holistic approach for informed decision-making amid the current dependency on mining proceeds alone in proposing mining projects in the locality and the entire Philippines.
1.0 INTRODUCTION
In Santa Cruz, Zambales, the relentless expansion of mining operations, coupled with lax regulations and insufficient monitoring, has raised profound concerns regarding the health and environmental well-being of the local community. This is particularly alarming given the discernible enrichment of heavy metals in critical ecosystems, including farm soil, surface water, deposited dust from roadsides, and rice grains. Heavy metals, recognized carcinogens such as lead, cadmium, and arsenic, pose severe health risks in mining sites (Hagnazar et al., 2023; Nolos et al., 2022; Ngole-Jeme & Fantke, 2017; Ali et al., 2021; Bouida et al., 2022; Docena et al., 2018; Hassaan et al., 2016; Kim et al., 2015). The uncontrolled release of mine tailings during flash floods, indiscriminate mining in protected areas, and the emission of dust from mine sites and hauling trucks exacerbate the release of heavy metals. The toxic, persistent, and bioaccumulative nature of these metals amplifies the detrimental effects on both human life and diverse ecosystems; (Hagnazar et al., 2023; Hassaan et al., 2016; Kim et al., 2015), highlighting a pressing environmental concern in mining regions of developing countries, including Santa Cruz in Zambales, necessitating urgent recognition and action, as exemplified in some of the most relevant and recent research from disturbed ecosystems from the works of (Fadlillah et al., 2023; Milena et al., 2020; Decena et al., 2018; Akoto & Anning, 2021; Hagnazar et al., 2023).
To begin with, the increasing dust from ore hauling trucks along major road networks, as reported by communities, is a matter of concern. The impact of airborne dust has been associated with both immediate and prolonged health repercussions in humans (Lara et al., 2021). Additionally, considerable epidemiological data substantiates its correlation with heightened daily morbidity and mortality rates (Huang et al., 2019). These observations underscore the multifaceted challenges arising from mining activities and emphasize the need for a thorough investigation into the ecological and human health risks associated with heavy metal contamination in Santa Cruz.
In response to these concerns, this research adopts a comprehensive approach to assess the ecological and human health risks linked to heavy metal contamination. The computation of the Potential Ecological Risk Index employs toxic response factors for each heavy metals, while the Contamination Factor, Pollution Load Index, and Enrichment Factor were dully computed to assess the metals impacts on the ecosystems as they each have their interpretations. The corresponding geochemical background concentrations were based on (Bowen, 1979; Turekian, 1961; Olivares et al., 2019). The human health risk assessment model follows guidelines from USEPA, 1989, through USEPA, 2004 to USEPA, 2011, with similar goals achieved in the following papers; (Lisa et al., 2021; Patil et al., 2022; Sin & Espuña, 2020; Lanzani et al., 2019; and Nduka et al., 2019). The computational analysis, implemented through the Python programming language using google colab and the aim is to provide a detailed understanding of the extent and nature of heavy metal contamination in Santa Cruz with line and bar plotting for visualization.
The research framework involves a comprehensive investigation into heavy metal contamination in Santa Cruz, Zambales, suspected to originate from mining activities. This encompasses the collection and analysis of samples from diverse ecosystem compartments, including farm soil, surface water, rice grains, and deposited dust particles as seen in figure 1. Similar work have been executed in mining communities through the sampling, analysis and reporting of the risk level from surface water; (Alcolea et al., 2015;), atmospheric deposited contaminates; (Yu et al., 2023; Wang et al., 2003;), soil, sediment and rice grain in e-waste dismantling center; (Li et al., 2021), groundwater; (Liu & Ma, 2020; Lu et al., 2016), rice grains, stem and leaves due to bioaccumulation from contaminated soil (Gu et al., 2018), soil and water media (Ahmad et al., 2021). Interestingly, the high correlation between contaminated soil to crop and the need for risk assessment on this due-ecological compartment has been documented (Mingtao et al., 2021), contaminated soil from coal mining and production sites; (Zhang et al., 2021), and the need for more holistic approach to risk assessment involving the uncertainty considerations, bioavailability, sensitivity analysis and robust modeling of risk to capture the dynamics of stressed ecosystems (Panquin et al., 2023; Yang et al., 2023). These processes include the application of environmental indices (PERI, CF, PLI, Igeo, EF) for ecological risk assessment, statistical analyses for spatial patterns, and health risk modeling for human exposure assessment. The output aims to deliver a decision support model for cost-benefit analysis, integrating health, environmental, and economic data to quantify the costs associated with heavy metals contamination. This model will inform policy makers on sustainable management practices, offering a holistic perspective on the ecological risks and human health hazards posed by heavy metals in Santa Cruz and their origin.
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