Читать книгу Geochemistry - Группа авторов - Страница 29

Understanding the nature and human exposure and health risks of toxic geogenic contaminants in serpentinitic ultramafic geological systems is critical for safeguarding human health. The current chapter presented an overview of the nature, occurrence, environmental behavior, and human exposure and health risks associated with toxic geogenic contaminants in serpentinitic ultramafic geological environments. Toxic geogenic contaminants of human health concern include toxic metals, rare earth elements, and chrysotile asbestos. Occupational and non-occupational exposure are the dominant human intake pathways. Human occupational exposure via inhalation occurs in industrial settings such as mining, milling, sculpturing, engraving, and carving. Non-occupational exposure pathways include inhalation of toxic geogenic contaminants and ingestion of contaminated geophagic earths, wild foods, herbal medicines, and water. Weak and poorly enforced occupation and environmental regulations, lack of environmental and human health surveillance systems coupled with high consumption of potentially contaminated wild foods, geophagic earths, and water increase human exposure and health risks in Africa. The prevalence of geophagy and high dietary intake of iron coupled with genetic disposition increases iron overload and the associated human health risks among native Africans. The human health risks of chrysotile include asbestosis, cancers, and mesothelioma, while toxic metal and rare earth elements induce oxidative stress which damages biomolecules such as deoxyribonucleic acid. Human health risks may also occur via synergistic interactions among toxic geogenic contaminants (e.g., chrysotile and toxic metals), and even between toxic geogenic contaminants and other health stressors such as the prevalence of infectious diseases. Mitigation measures to safeguard human health, and future research directions were highlighted.