Long-term spatiotemporal variation of benzo[a]pyrene in Japan: Significant decrease in ambient concentrations, human...

Area of Science:

• Environmental Science
• Public Health
• Toxicology

Background:

• Benzo[a]pyrene (BaP) is a known human carcinogen, but its health impacts at ambient exposure levels require further investigation.
• Understanding the spatiotemporal distribution of BaP is crucial for assessing public health risks.

Purpose of the Study:

• To estimate the long-term spatiotemporal variation of Benzo[a]pyrene (BaP) in Japan at a 1 km resolution.
• To provide accurate BaP distribution data for epidemiological studies on ambient exposure health effects.

Main Methods:

• Employed an ensemble machine learning approach to estimate annual BaP concentrations.
• Utilized predictors including criteria air pollutants, emissions, meteorological data, land use, and traffic variables.
• Validated model performance using location-based cross-validation, achieving R² of 0.693.

Main Results:

• Densely populated areas exhibited higher BaP levels and greater temporal reductions.
• Industrial areas showed persistently higher BaP concentrations.
• Population-weighted BaP decreased by approximately 70% from 0.44 ng m⁻³ in 2000 to 0.12 ng m⁻³ in 2018.
• The proportion of exposure below the 10⁻⁵ excess cancer risk level (0.12 ng m⁻³) reached 67% in 2018.

Conclusions:

• The study successfully mapped fine-resolution spatiotemporal BaP variations in Japan over two decades.
• Estimated reductions in BaP exposure correlate with decreased lung cancer incidence risk.
• The generated data is valuable for future epidemiological research on ambient BaP health impacts.