Polycyclic Aromatic Hydrocarbons in Environmental Systems

Polycyclic aromatic hydrocarbons (PAHs) are a class of organic compounds composed of two or more fused benzene rings. They arise primarily from incomplete combustion of fossil fuels, biomass burning and various industrial processes. Due to their hydrophobicity, low volatility and thermostability, PAHs persist in air, water, soil and sediments, where they partition between phases according to temperature, particle loading and organic carbon content. In the atmosphere, PAHs may exist in both gas and particle phases, undergoing long-range transport and transformation by oxidants such as hydroxyl radicals, ozone and nitrogen oxides. In aquatic and terrestrial systems, PAHs adsorb to organic matter and fine particulates, bioaccumulate in organisms and biomagnify through food webs. Many PAHs and their derivatives exhibit mutagenic and carcinogenic properties, posing risks to human health and ecosystems. Monitoring and regulation of PAH inputs have driven advances in analytical chemistry, while remediation strategies—ranging from physical or chemical treatments to bioremediation—are under active development. A global perspective emphasises hotspots near urban centres and industrial sites, deep-sea and polar environments as emerging sinks, and links to climate-driven changes in source strength and degradation pathways.

Research from Nature Portfolio

Recent investigations have characterised nitro-PAHs in urban and interior environments, quantifying potent mutagens such as 2-nitrobenzanthrone and 3-nitrobenzanthrone in fine particulate matter. These studies delineate source contributions from diesel exhaust, wood combustion and photochemical formation, apply multivariate statistics to resolve formation routes, and assess inhalation cancer risk through concentration measurements and toxic equivalency factors. Findings emphasise the importance of gas-phase reactions and heterogeneous chemistry in generating nitro-derivatives and underscore the need for targeted monitoring of these high-potency contaminants.

Polycyclic Aromatic Hydrocarbons in Environmental Systems publication trend

The graph below shows the total number of articles in polycyclic aromatic hydrocarbons in environmental systems across all publications each year (not limited to Nature Index journals).

Technical terms

Polycyclic aromatic hydrocarbons (PAHs): Organic compounds with multiple fused aromatic rings, notable for persistence and toxicity.

Nitro-PAHs: Nitrated derivatives of PAHs produced by atmospheric oxidation or combustion, often more mutagenic than parent compounds.

Bioaccumulation: The process by which organisms absorb and concentrate chemicals from their environment and food.

Photochemical transformation: Chemical alteration of compounds under the influence of sunlight and atmospheric oxidants.

Bioremediation: Use of living organisms or enzymes to break down or sequester environmental contaminants.

References

1. Organic matter degradation causes enrichment of organic pollutants in hadal sediments. Nature Communications (2023).
2. Revisiting the analytical determination of PAHs in environmental samples: An update on recent advances. Trends in Environmental Analytical Chemistry (2023).
3. Occurrence of the potent mutagens 2- nitrobenzanthrone and 3-nitrobenzanthrone in fine airborne particles. Scientific Reports (2019).
4. Polycyclic Aromatic Hydrocarbons: Sources, Toxicity, and Remediation Approaches. Frontiers in Microbiology (2020).
5. Chemical reactivity and long-range transport potential of polycyclic aromatic hydrocarbons – a review. Chemical Society Reviews (2013).
6. Toxicities of Polycyclic Aromatic Hydrocarbons for Aquatic Animals. International Journal of Environmental Research and Public Health (2020).
7. Atmospheric chemistry of gas-phase polycyclic aromatic hydrocarbons: formation of atmospheric mutagens.. Environmental Health Perspectives (1994).