Dr Deng Wenjing’s research on airborne endocrine-disrupting chemicals helps improve indoor environment

Dr Deng Wenjing, Associate Professor, Department of Science and Environmental Studies (SES), completed her BSc and MPhil in Environmental Science from Nanjing Agricultural University in Nanjing and holds two PhDs in Environmental Science awarded by the Hong Kong Baptist University and Sun Yat-sen University in Guangzhou.

Dr Deng has rich research experiences in emerging chemicals and their impact on children’s health, antibiotics and resistant genes in the environment and related health implications, and indoor air quality and its health impacts on students. In recent years, Dr Deng’s research focus has been on the study of endocrine-disrupting chemicals (EDCs) and their effects on people’s health. Her research has influenced the government’s policy formulation on indoor air quality, helping enhance the protection of public health and improve people’s well-being.

Apart from conducting research, she teaches courses related to environmental science, environmental education, solid waste management, and air pollution and its treatment. Dr Deng was named Outstanding Member of the Youth Working Committee of the Soil Science Society of China (SSSC) in 2023 to acknowledge her international academic impact and her potential to attain world-leading status in the field of environmental and soil science.

In this issue of FLASS FORWARD, Dr Deng shares with us some of her recent research projects, tips about keeping a productive research career and the joy of impacting society through her research works.

Dr Deng: EDCs are the acronym for endocrine-disrupting chemicals. As the name suggests, EDCs disrupt the regular functioning of our body's endocrine system. Human’s endocrine system produces and stores a whole array of hormones to regulate multiple body functions, including metabolism, reproduction, and growth. Disruptions to it could mean serious and harmful implications on human health.

Similar to natural hormones, EDCs can have effects on the human body even at very low doses. EDCs are prevalent in numerous daily products like plastic bottles, detergents, toys, personal care products, cosmetics, and pesticides. It has been proved that prolonged exposure to EDCs even at low levels can lead to different kinds of chronic diseases and disorders. The academic world is increasingly cognisant of the adverse consequences of EDCs on human health.

Dr Deng: It is widely recognised that children are more susceptible to EDCs than adults. Yet, learning how children are exposed to EDCs can be complicated as there are countless ways for them to be exposed to EDCs in real life. One of my recent research projects used the target and non-target analysis (NTA) to analyse urine samples obtained from 46 children and their parents in Hong Kong and Guangzhou so as to understand their EDC exposure levels. Through NTA, the study has identified a total of 1,069 compounds in the urine samples. More than 100 out of these 1,069 compounds are EDCs, including BP-type UV-filters, organophosphate flame retardants (PFRS), bisphenol A (BPA), and so forth.

Through questionnaires, we tried to find out from which channels the participating children absorbed these EDCs. There are notable regional differences between children from Guangzhou and Hong Kong, but the study found that common ways of EDC exposure among these children include breathing, consuming food, drinking water, and the use of sunblock. The study also showed that EDCs-containing objects like toys, flooring materials, and dust are possible sources.

One of the main findings of the study is lifestyle plays a large part in EDC exposure. For example, when children play on the floor, their hands would likely be in contact with dust. Without cleaning their hands adequately after playing, children might take in EDCs-containing dust into their bodies when consuming food or drinks.

The research team also discovered larger amount of caffeine in children’s urine samples from Hong Kong than Guangzhou. The study identified diet and toys as potential main sources of EDC exposure, though further studies are needed to confirm the sources. Detailed results are included in the recently published paper “Endocrine disrupting chemicals in children’s and their parents’ urine: Is the exposure related to the Chinese and Western lifestyle?”.

Dr Deng: Plasticizers, such as phthalates and bisphenol and their substitutes, are endocrine-disrupting chemicals widely used in plastics to make them more flexible and durable. Plastics are widely used for household products like pens, buckets, bags, bottles, flooring, and curtains. Meanwhile, the construction industry, packaging industry, automobile manufacturing, and even the medical field use a lot of plastics. As plastics are extensively used in our society, it is almost impossible for people to avoid exposing themselves to plasticizers.

As many traditional plasticizers are toxic, new plasticizers are introduced as alternatives. However, it has been found that these new plasticizers also have adverse effects on people’s health. My other study discovered that common plasticizers were found in urine and hair samples from kindergarten children and from samples of tap water, bottled water, and airborne particles in 17 Hong Kong kindergartens. The results suggested that local children were exposed to a wide range of plasticizers and their alternatives. The study revealed that we cannot underestimate the risk that kindergarten children take as they are exposed to plasticizers through the air they breathe, tap water they drink or dust they touch in the environment.

Dr Deng: Polybrominated diphenyl ethers (PBDEs) have been widely used as a flame retardant. As exposure to PBDEs has been proven to be associated with adverse health effects in both humans and wildlife, its use has been banned in recent years. As an alternative to PBDEs, organophosphate flame retardants (PFRs) have been increasingly used worldwide. However, recent research showed that PFRs can cause many adverse health problems, such as contact dermatitis, disruption of the endocrine system, reproductive toxicity, and even carcinogenic effects. My team and I conducted the first study about urinary PFRs in Hong Kong preschool children. This study showed that children's exposure to certain kinds of PFR may be underestimated and there is a need for further investigation of these aspects through large-scale surveys to scrutinise all possible routes of exposure.

Per-and-polyfluoroalkyl substances (PFAS) are EDCs used in kitchen utensils, fast food packaging, shampoos, and as water-proof materials for clothes. As a packaging material, it is even found in ice cream cones. As PFAS molecules are composed of chains of interlocked carbon and fluorine atoms, they are extremely stable and degrade very slowly in the environment. That means PFAS can continue to accumulate in the environment, like in drinking water and food. Through the bio-accumulation effect, PFAS becomes more concentrated when moving up in the food chain.

Several benzophenones, bisphenols and polyphenols are also EDCs that attract much attention in the scholarly world. Among them, benzophenones (BPs) type UV-filters are widely used in sun creams. Apart from UV protection, BPs are also widely used as fragrance retention agents or in cosmetics, shampoos, or skin-moisturising products. Studies have indicated that certain types of BPs could cause reproductive and developmental toxicity. One of my research projects suggested that BP-type UV-filters and other types of UV-filters which are widely used in recent years are also ubiquitous in children's urine samples, tap water, and distilled bottled water in Hong Kong. Although the estimated health risks of UV-filters in Hong Kong children are relatively low, the health effects of low-dose and long-term exposure to these chemicals cannot be neglected.

Dr Deng: The academic world is moving fast today. Thousands and thousands of research projects appear in the pipeline every day. Researchers need to have a sharp and adaptive mind to keep up with the times. While we need to understand how our field is developing, we also need to have a clear mind about our own strengths such that we can adhere to a research direction that leverages our experiences and at the same time aligns with the current development trend.

Chemistry is an old discipline. Over the past one hundred years, chemists have carried out research on a wide range of topics, including studies of heavy metals, new materials, and fossil fuels. However in the past few decades, more and more chemistry research has been devoted to the study of EDCs. Every now and then, there are new ideas emerging in the research of EDCs. To understand the latest trends regarding EDCs research, researchers must read extensively and keep close communications with their peers. Through these readings and communications, researchers know the pulse of the field as well as understand the latest concerns of society. In the process, researchers stimulate each other and brainstorm new ideas for doing research.

In a nutshell, researchers need to open their eyes to know what is going on in the field. Researchers need a sharp brain to grasp the trend of research and an adaptive mind to adjust their research so that they can ride on the trend.

Dr Deng: On the other hand, academic research is as big as an ocean. Floating on the ocean aimlessly will exhaust all your energy without reaching any ground. To sail forward in the big ocean, you need to know your direction. In the academic ocean, you need to focus on a few research topics and treat them as the very means for your survival. In my case, I focus my research on environmental pollution, chemical pollution, and toxicology. In recent years, I have spent most of my time on research projects on EDCs. While I keep myself updated with the latest trends in these fields and adjust my research plans accordingly, I won’t change to new fields.

In a word, stick to your direction with a simple mind throughout the journey. Otherwise, it is going to get you nowhere.

Dr Deng: It is almost like a cliché to underline that a strong passion for your work can keep you focused. I like doing research in environmental studies. I like teaching students too. And I see teaching and research works complement each other for I can use my research findings in my teaching. My strong interest in research and teaching directs my attention to my work. When arriving at the office, I prepare myself to concentrate on my work which I like so much.

Of course, I also have moments when my mind is wandering. I think it is natural for human beings, including scholars, to experience such moments now and then. There are also times we get depressed when our research progress is less than satisfactory, and difficulties arise. Just let the mind wander and relax for a while. However, continuous mind wandering will lead us off track from our original path. We need to build a composed and resilient character in the face of adversity. These traits help us become focused again.

While people’s attention spans dwindle in the world of social media, we need to be very patient in the world of research. For instance, you need to read several hundred journal articles before you can prepare and submit a good proposal. It takes many years even for a well-designed, well-funded research project to breed results. It is not a good habit to change your research focus when you are waiting for results and when you see other research projects have produced promising outcomes.

Dr Deng: International collaboration is one of the key components of internationalisation at any institution. While international collaborations are built on a network of good relationships, it takes a long time to build the trust necessary for a good relationship. Colleagues at FLASS should spend efforts to build their networks as early as possible in their academic careers.

Professor Ying Guang-guo from the Environmental Research Institute of South China Normal University and Professor Adrain Covaci from the Antwerp University of Belgium are two of my major academic collaborators. We have joined efforts in many research projects and co-published many papers. As we have known each other for more than ten years, there is a strong trust between us. Whenever I seek help from Professor Ying and Professor Covaci, they are willing to offer it. When I invite them to work collaboratively, they quickly understand my research ideas. Because of mutual trust and the fact that we think alike when conducting research, we can easily agree on the framework of cooperation and the division of labor.

Dr Deng: Every time, I see my research results get published in international journals, I feel a strong sense of satisfaction. This means your research efforts are recognised by the academic circle and you are bringing impact on the academic world. As an experimental chemist, most of my research efforts are dedicated to laboratory work. It also brings me happiness when I find that my new methods for doing laboratory work are adopted by other researchers.

Producing positive social impact also gives me joy. Most urban dwellers spend more than 70%, even up to nearly 90% for some Hong Kong people, of their time in indoor environments. That’s why indoor pollution is closely related to our health. My colleagues and I at SES have carried out many research projects on EDCs and indoor air quality, and have held many talks to share our findings. These research works have provided policymakers with valuable insight into indoor environments and helped them formulate appropriate preventive strategies, such as identifying the main pollution sources and regulating the usage of common plasticizers and other EDCs.

When the Hong Kong government issued a new Indoor Air Quality (IAQ) guidance in December 2022, it incorporated many of our suggestions. We will conduct further studies on how changes in the lifestyle of students and in school policies can reduce students’ EDC exposure. When we establish more findings, we will make a concrete proposal to the concerned government departments.

We are collaborating with Belgian researchers to investigate children’s EDC exposure in Hong Kong and Europe. We hope the joint research will promote discussions to find possible exposure routes, thus formulating better health policies related to EDCs and leading to a better school environment in the future. We hope these studies can ultimately help establish guidelines for the usage of EDCs in Hong Kong and Belgium.