Persistent polycyclic aromatic hydrocarbons (PAHs) in the soil, its bioremediation, and health effects
Ranjeet Kumar Singh, Shailendra Kumar Singh
Abstract
Polycyclic aromatic hydrocarbons (PAHs) are mostly toxic compounds tied with strong molecular bonds. Benzo[a]pyrene is the most toxic PAH found naturally and anthropogenically in the soil. PAHs are structurally complex and require cautious handling due to their noxious effect on the environment. PAH contamination in the environment, particularly soil, is a proven oncogenic agent as it enters the body through the food chain. They are bonded strongly with the soil depending on their nature, texture, available organic carbon, nitrogen, pH, temperature, and moisture. Out of these, texture is the most important. Clayey soil binds PAHs the most, and sandy soil the least. Many PAHs are not easily degraded and remain persistent and are liable to enter the living system through multiple modes like aerial, dermal, and food through numerous signaling pathways, posing a great risk to human health. Multiple health effects are reported, e.g., mutagenic, cardiovascular, eye, liver, kidney, and neural systems, etc., which may occur due to short- or long-term exposure to PAHs. Cancer is the most prevalent disease reported in history. Ample methods are applied for PAHs degradation in the soil. Biodegradation by microbial communities is the most recommended option, but is slow and costly. Therefore, technological intermix is the preferred choice depending on the nature of the substrate and the limits desired, e.g., degradation of phenanthrene, anthracene, and benzo[a] pyrene increased from 68% to 92–96% by nano-zero-valent iron combined with white rot fungi Peniophora incarnata. Study on PAHs remediation and its health effect in the soil environment is of paramount importance considering its severity.