The proposed study will combine in vitro bioassay, target/non-target chemical analysis, population survey, and risk assessment. Eventually, the investigation will provide a reference for setting guidelines for usage of EDCs in Hong Kong and Belgium to safeguard the population.

Endocrine disrupting chemicals (EDCs) have been deemed by the World Health Organization as one of the most serious environmental health problems in the 21st century. EDCs have effects at extremely low doses just like natural hormones in regulating bodily functions. Low-level and long-time exposure to EDCs has been shown to cause more subtle, chronic, and long-lasting effects. Young children are more likely to be sensitive than adults and suffer from the adverse effects of EDCs because of children’s continuing development and behavioral activities. Therefore, there is increasing global concern on the chemical body burden of EDCs on children.

Urinary EDCs can directly signify the amount of internal exposure to EDCs, which has been consistently found to be at high levels in children from national monitoring programmes in Europe, USA, Canada and Japan. Our previous studies in 2017 showed that EDCs were ubiquitous in indoor environment and urine samples in kindergarten and primary schools of Hong Kong. However, the key contributors and determinants to exposure, as well as exposure pathways remain to be explored. In addition, the predicted children’s body burden by exposure to EDCs that cling to indoor dust and air particles was estimated as lower than that for urinary readings, indicating that the actual risks associated with EDCs may be substantially underestimated. Hence, it is necessary for further studies in Hong Kong. Considering the great concerns and solid research foundation of EDCs and EDA in Europe, we will collaborate with Belgian researchers to investigate the key contributors to exposure to EDCs in children both in Hong Kong and in Europe. This will help to intercompare the results and allow for discussions to find the possible exposure routes in order to develop future health policies related to EDCs.

However, the body burden to children and effects of EDCs around the world still remain poorly understood because the large number of emerging EDCs and environmental abiotic/biotic samples are often contaminated with complex mixtures of many chemicals. In order to regulate the usage of EDCs, it is necessary to find out the key contributors, because of the large number of emerging EDCs (over 100,000 chemicals are currently in use and several hundreds of chemicals have already been identified to be EDCs). Chemical-based risk assessments do not provide any prioritisation or hazard information, while biological tests do not provide any structural information about the bioactive compound. The solution to testing for EDCs is effect-directed analysis (EDA) which has been designed to overcome the shortcomings of the chemical based tests and biological tests. EDA is a valuable tool to reduce the complexity of environmental abiotic/biotic samples, and it can deftly incorporate in vitro/vivo bioassay, sample fractionation, and target/non-target analysis to identify key environmental pollutants in complex matrices.

In this study, urine samples of primary school children between 3-12 years old in Hong Kong and Belgium will be sampled. Bisphenol A, phthalates, organophosphate flame retardants (OPFRs), perfluoroalkyl substances (PFASs) and their metabolites which are rated as high exposure and high production volume EDCs are selected as targets. Urine samples are to be first fractionated to reduce complexity, then in vitro estrogen/thyroid receptor bioassay will be used to identify the active fractions and to guide the targets and non-targets. Afterwards the targets will be analysed by LC-triple quadrupole MS techniques (LC-QQQ-MS). Considering that only ten to hundreds EDCs have been included in the priority lists for regular chemical monitoring, if the key contribute EDCs cannot be found by target analysis, non-target analysis using LC-quadrupole-time-of-flight MS techniques (LC-QTOF-MS) will be used. Finally, the suspected EDCs will be confirmed by re-establishing their dose-response relationships and establishing the potency balance. The results of this study will assist in the identification of the species and amount of EDCs in the body burden of children in Hong Kong and Belgium.

In conclusion, to study exposure to EDCs in the child population of Hong Kong and Belgium, the proposed study will combine in vitro bioassay, target/non-target chemical analysis, population survey, and risk assessment. Eventually, the investigation will provide a reference for setting guidelines for usage of EDCs in Hong Kong and Belgium to safeguard the population.