This article has been reviewed according to Science X's editorial process and policies. Editors have highlighted the following attributes while ensuring the content's credibility: Environmental pollutants containing chlorine or bromine have been widely studied, but compounds containing both elements have remained largely unexplored. Researchers have now detected bromochloropyrene in industrial soils and harbor sediments, investigated its breakdown under simulated sunlight, and measured its activity through a biological receptor linked to toxic effects.
The findings reveal distinct environmental and biological properties, highlighting the need to investigate other mixed-halogen pollutants and improve future environmental monitoring and risk assessment. Halogenated polycyclic aromatic hydrocarbons (HPAHs) are pollutants produced by combustion and found in soil and sediment. Some contain halogen atoms, such as chlorine or bromine.
These compounds can persist and affect biological systems. However, research has largely examined compounds containing either chlorine or bromine, leaving those with both elements poorly understood. Addressing this challenge, a research team led by Professor Takeshi Ohura, along with graduate student Natsuki Nasuda from the Graduate School of Agriculture, Meijo University, Japan, and Dr.
Guruge, senior researcher from the Division of Hygiene Management Research, National Institute of Animal Health, National Agriculture and Food Research Organization, synthesized a reference standard of bromochloropyrene (BrClPy)—a representative halomix—and analyzed surface soils from 20 sites along Tokyo Bay and sediments from three sites in Nagoya Port, Japan. They tested its stability under simulated sunlight and ability to activate the aryl hydrocarbon receptor (AhR). Their findings were published in the journal Emerging Contaminants.
BrClPy was detected in 10 of the 20 soil samples, at a mean concentration of 0.13 nanograms per gram. It was also found in one of the three sediment samples, where the mean concentration was 0.42 nanograms per gram. In soil, BrClPy concentrations were strongly correlated with brominated pyrene compounds, suggesting that its formation may be more closely linked to bromination-related processes than to chlorinated pyrene.
This hybrid behavior suggests that hetero-halogenation produces emergent properties not predictable from either chlorine- or bromine-substituted PAHs alone. Laboratory tests showed that BrClPy was less stable under simulated sunlight than chlorinated pyrene, with photostability approximately twofold lower than that of 1-chloropyrene. As it broke down, it mainly lost bromine, producing 1-chloropyrene; the researchers did not observe the corresponding product formed by losing chlorine.
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