Spatial Distribution of Polycyclic Aromatic Hydrocarbons in Soil and Potential Human Health Risks within a Confirmed Cancer Cluster in the Greater Fifth Ward, Houston, Texas

The study assessed the occurrence, spatial distribution, and potential human health risks of polycyclic aromatic hydrocarbons (PAHs) within the Greater Fifth Ward, a residential area located in Northeast Houston. From July to November 2021, a complete canvas was done within the defined geographic boundary to collect surface soil samples from participants’ private yards. Using standard extraction and gas chromatography-mass spectrometry methods, the levels of x PAHs in each sample were quantified and used to calculate pyrogenic indices and evaluate PAH source apportionment. This information was used to calculate cancer risks based on the U.S. Environmental Protection Agency (U.S. EPA) Regional Screening Levels (RSLs) for residential soils. Of the 103 soil samples, at least 1 of the 16 EPA priority pollutant PAHs were detected in each sample. The total concentration of the 7 carcinogenic PAHs ranged from 9.9 to 40,290 ng/g (mean = 402 ng/g, standard deviation = 28,490). The RSLs showed that 7 of the 103 soil samples exceeded the U.S. EPA’s most conservative screening levels of 1.0 × 10^{− 6} and had values within the target range for remedial actions, however, only one of those sites was considered actionable. Findings from this study highlight the need for site-specific risk assessments in environmental justice communities with known legacy contaminants. The current PAH concentrations are likely lower than historical values due to remediation in nearby areas, as well as PAH volatilization, photooxidation, and microbial degradation. Additional research is needed to explore remediation strategies and direct links to human health.