Evaluating environmental and human health risks from phosphorus flame retardants in South West England using One Health water-based epidemiology

Phosphorus flames retardants (PFRs) are ubiquitous in everyday household items and buildings and as a result have been frequently detected in domestic wastewater as well as environmental matrices. A One Health water-based epidemiology framework was employed to screen for and retrospectively quantify 7 PFRs and 5 metabolites in the Avon catchment (5 cities and towns with varying population sizes and industrial contribution, representing >75% of the whole catchment population) to understand key contributors to environmental burden and evaluate potential risks to public and environmental health. Of these 12 analytes, 11 were detected at quantifiable levels in at least one wastewater sample. Influent daily loads and population normalised daily loads were used to identify any spatiotemporal trends. For all PFRs, daily loads increased with population equivalents suggesting that this was a major driver of PFR burden in domestic wastewater. Due to limited information on the human excretion of PFRs, daily intake was estimated based on three excretion scenarios. Estimated daily intakes of tri-n‑butyl phosphate (TnBP) were generally higher than their reference doses. While potential risk to public health could not be comprehensively assessed, it showed the potential for WBE to be utilised as part of an early warning framework. Average river daily loads suggested a steady increase of PFRs along the Avon River likely due to wastewater discharge. For some PFRs, average daily loads were greater upstream than downstream of wastewater discharge suggesting that other sources, (e.g., surface run-off) were contributing to their environmental presence. Environmental risk assessment was carried out using a risk quotient (RQ) method. RQ values found were high for triphenyl phosphate (TPhP) and moderate for tris(2-butoxyethyl) phosphate (TBOEP) and TDCPP suggesting a potential risk to environmental health. This study showed the potential of using this framework, employing suspect screening and retrospective quantification, to holistically evaluate exposure within a catchment. It also highlighted, that different PFRs might constitute risks to humans and the environment, hence regulatory frameworks should consider One Health evaluation in decision making.