Bridging the gap between environment and health – exposure assessment of potentially harmful agents in soil

Our current understanding of soil exposure in the UK population is extremely limited. The current risk assessment paradigm makes large assumptions based on very uncertain data to estimate direct exposures via soil ingestion or dust inhalation. Because these are direct routes of exposure, these pathways have the potential to represent significant exposures in comparison to better characterized exposure pathways. Thus, in order to improve accuracy of risk assessments, more attention needs to be paid to these exposure pathways. Public Health England have recognized these important needs and have initiated an Environmental Public Health Tracking (EPHT) programme that aims to explore and develop a methodology for addressing environmental hazards that delivers integrated, local and national surveillance of those hazards, exposure assessment, and relating health effects of environmental exposures to those hazards. This PhD will be closely aligned to the EPHT programme.
Aims & Potential Outcomes
This study aims to begin to better characterize human exposures from potentially harmful agents in soil, both direct (i.e. ingestion/inhalation of soil) as well as indirect (i.e. via uptake into food crops). This project will utilize study populations included in the EPHT programme. This PhD will provide evidence necessary to estimate any health burden related to such hazards and exposures, informs responses to new exposures, and supports the on-going development of environmental epidemiology and toxicology in PHE.
Methods/Approach
This project provides a student with the opportunity to become involved in a large public health initiative such as EPHT. This project will build on previous soil exposure work undertaken by Hooda, as well as dietary exposure work undertaken by Hough and Leonardi as part of an EU FP5 project (ASHRAM). The proposed project will have three main activity strands:
Activity 1: Experimental study to evaluate soil ingestion within PHEs EPHT study populations – The exact methodology is dependent on the EPHT programme which has not yet reached a decision on where the next field investigation will take place, they are however committed to the continuation of this work and the successful student would be involved in finalizing the field investigation which will include collaboration with BGS for soil sampling, PHE for toxicology, and (potentially) NHS if e.g. fecal samples are used (see below). Engagement with EHPT and the field study team will therefore form a significant part of the PhD itself. This model has already been successfully implemented by PHE with a PhD project looking into arsenic in private water supplies. Regardless of final study population, the PhD will focus on infants and children as these groups tend to experience higher soil exposure. Sampling is likely to include hand wipes of infants, personal dust samplers, conserved tracer analysis of faecal samples (easier for infants using diaper samples), vacuuming and analysis of house dust. It is expected that study design would take 6 – 12 months, with 12 – 18 months for sample collection.
Activity 2: Analysis of soil samples from Activity 1 to determine specific exposures – Soil samples will be taken as appropriate during Activity 1. As described above, samples may be in the form of hand wipes, or dust samples. As well as these, surface soil samples will be taken from identified play or work areas such as gardens, allotments, parks, etc. All samples will be analysed for a range of important toxicants (e.g. As, Cd, Hg, Pb, Phthalates, PAHs, PBDEs, PCBs). The results of activities 1 and 2 will be used to estimate exposures to these toxicants via direct ingestion/inhalation of soil.
Activity 3: Develop a methodology to translate soil information into dietary exposures – The extent of this activity will depend on progress of Activities 1 and 2. Using dietary and recipe data collated as part of EU FP5 ASHRAM, a methodology will be developed that attempts to translate soil information into estimates of dietary exposure. This methodology could then be applied to the soil data collected during Activity 2. While the data from ASHRAM will not relate to the EPHT study population, demonstrating this methodology will show how such an analysis could be carried out on EPHT populations in the future.