Do suspended particles matter for wastewater-based epidemiology?

Area of Science:

• Environmental Chemistry
• Public Health
• Analytical Chemistry

Background:

• Wastewater-based epidemiology (WBE) relies on analyzing wastewater for public health insights.
• Sorption of target compounds onto suspended particulate matter (SPM) in raw wastewater is an underexplored limitation potentially causing underestimations in WBE.
• Previous research focused on limited analytes and small sample sizes, necessitating broader investigation.

Purpose of the Study:

• To comprehensively assess the sorption behavior of a wide range of WBE markers (pharmaceuticals, illicit drugs, lifestyle biomarkers) onto SPM.
• To evaluate the impact of sorption on WBE estimates and identify compounds requiring specific corrections.
• To investigate factors influencing compound partitioning, including physicochemical properties and wastewater characteristics.

Main Methods:

• A six-month monitoring campaign analyzed dissolved and particulate phases of raw wastewater.
• Pressurized liquid extraction and liquid chromatography coupled with tandem mass spectrometry were employed for analysis.
• Daily loads and distribution behavior of target compounds were assessed.

Main Results:

• Most WBE markers exhibited low sorption to SPM, supporting their reliability for WBE using dissolved-phase measurements.
• This study provides the first clear assessment of minimal sorption for tobacco and coffee biomarkers.
• Significant sorption was observed for 11 molecules (e.g., fluoxetine, THCCOOH, methadone), indicating a 'hidden load' that can bias WBE estimates without correction.
• Log D was a better predictor than log Kow for ionized compounds' sorption, but ineffective for neutral species.
• Wastewater dilution from urban runoff may increase compound affinity for SPM, while stable TOC levels suggest in-sewer organic deposits contribute to SPM composition.

Conclusions:

• While most WBE markers are suitable for analysis in the dissolved phase, specific compounds require correction for SPM sorption to ensure accurate WBE.
• The findings highlight the need to account for the partitioning behavior of certain pharmaceuticals, illicit drugs, and biomarkers in WBE.
• Further research is needed to elucidate the key parameters governing compound-SPM interactions and their implications for WBE accuracy.