Endocrine-disrupting chemicals are prevalent in our environment. Dr Josef Köhrle, Senior Professor of Molecular Endocrinology and Editor-in-Chief of Environmental Endocrinology, discusses with Lorna Rothery the urgent need for stronger actions to address the potential health risks posed by these chemicals
Q. What are EDCs, and how prevalent are they in our environment?
Endocrine-disrupting chemicals (EDCs) are prevalent in our environment, consumer products, and food. These compounds can interfere with hormone systems in various ways. For example, they may affect hormone synthesis in glands or cells, disrupt the distribution of hormones throughout the body to target tissues, and interfere with cellular actions via hormone receptors. Additionally, they can influence hormone metabolism, which includes the activation and deactivation of both active and inactive hormones.
It is important to note that not all chemicals affecting hormone systems qualify as endocrine disruptors. For a chemical to be classified as an endocrine-disrupting compound, there must be a clear link between exposure and adverse effects on the exposed organism. There are also suspected endocrine-disrupting compounds for which definitive proof of their effects on humans or ecosystems is still lacking, highlighting the need for ongoing research in this area.
EDCs can be categorized based on their chemical properties, particularly their persistence in the environment. This includes short-lived versus long-lived substances. Long-lived compounds, often referred to as persistent organic pollutants (POPs) or ‘forever chemicals,’ do not break down easily and can remain in the environment for decades. As a result, we may still be exposed to some EDCs that were banned ten or 20 years ago, such as DDT, certain polychlorinated biphenyls (PCBs), and some phthalates.
These long-lasting chemicals can accumulate in ecosystems and impact not only humans but also various life forms, particularly animals in both aquatic and terrestrial environments. They often build up in the food chain. Furthermore, these chemicals can accumulate in the human body, particularly in fat cells (adipose tissue), as many EDCs are lipophilic and insoluble in water.
This is a significant concern because recent research has also detected these long-lived EDCs in polar regions. They are now widely distributed throughout the ecosystem, potentially affecting individuals of all ages, meaning it is likely that many of us are contaminated to some extent. While this contamination may not cause immediate health issues, the long-term effects remain uncertain.
In many situations, we no longer have human control groups for studies involving unexposed individuals. Thus, it can be said that everyone is affected by some EDCs. However, we must be cautious in asserting that this exposure has an immediate health impact, as we do not yet know the specific levels at which health effects truly begin, whether acutely or chronically.
There are several types of EDCs to be aware of. These include bisphenols, such as bisphenol A, and phthalates. Additionally, there are various halogenated hydrocarbons, which can be further classified into fluorinated, chlorinated, and brominated compounds. For instance, chlorinated compounds include polychlorinated biphenyls (PCBs) and dioxins, while brominated compounds, particularly brominated flame retardants, are a significant concern and are increasingly prevalent.
Moreover, it is essential to recognise that we are not only exposed to single chemicals at a time; instead, we encounter mixtures of various substances in our daily lives. These mixtures are often found in everyday products. This complexity makes it challenging to establish causal links between exposure and adverse health effects, especially when compared to controlled experimental animal studies, where cause-and-effect relationships can be more clearly identified.
Q. Could you explain the common routes of exposure and the potential impact of EDCs on the human body?
Many factors influence the effects of exposure to certain chemicals; these can vary based on where you live, your age, and your occupation. For example, workers in environments such as greenhouses or gardening may experience significant occupational exposure to pesticides, some of which are endocrine-disrupting chemicals (EDCs). For the average person, the highest exposures are likely to come from bisphenols, phthalates, and per- and polyfluoroalkyl substances (PFAS). These substances are now commonly found throughout Europe, with certain areas showing heightened levels of exposure, in our food and drinking water, for example. Producers of drinking water in cities face significant difficulties in removing contaminants, as they have already reached levels that may cause or facilitate the origin of diseases. Our skin is affected by body care products, such as hygiene products, cosmetics, and UV protection, as well as clothes that contain chemicals like EDCs for various purposes, including water repellence or similar effects.
Micro- and nano-plastics are becoming a substantial and significant source of EDC exposure because many plastics contain some or a mixture of EDCs. When we are exposed, the question is whether there is harm.
May there be harm, or do we know that there is harm? We have clear evidence that EDCs specifically interfere with the developmental processes of our body and organs during early life. This primarily affects the development and function of the male and female reproductive systems. EDC exposure also has a major impact on the development and organisation of our central nervous system, specifically the brain, with adverse effects on cognitive function, including a decrease in IQ, as well as behavioural impacts. Another significant area that has yet to receive extensive research is the structural and energy metabolism of our body, especially regarding the reproductive system and brain development. Exposure to EDCs in the womb may predispose individuals to metabolic disturbances such as obesity and diabetes, leading to further metabolic issues in adulthood.
The group of EDCs interfering with energy metabolism has, in turn, acquired a sub-name. They are called metabolic disruptors. We know a great deal about bisphenols, their effects on the function of beta cells and insulin secretion, as well as many other substances, such as phthalates. This exposure, especially during development, has led to a hypothesis that has been known for at least three or four decades: the so-called DOHaD hypothesis (Developmental Origins of Health and Disease). We know now that this is happening. We have both association data and epidemiological evidence for humans, along with strong and convincing causal data from animal studies. Additionally, we have mechanistic insights into how these chemicals affect the endocrine system, supported by in vitro and cell culture research. Therefore, we cannot dismiss this issue; it is a legitimate concern that these chemicals can impact our health. Certain population subgroups are affected more significantly than others. For instance, vulnerable groups include pregnant women and their children, lactating women, and individuals with genetic makeups that may increase their susceptibility to the adverse effects of endocrine disruptors or other chemicals.
Q. What protective steps can individuals take to mitigate their exposure to EDCs and also reduce their impact?
Before I answer this question, we need to consider the other side of the issue and the second part of the question, which cannot be overlooked. What must regulatory authorities, policymakers, society, and producers of these products do to minimise environmental and human exposure? We cannot place the entire burden on individuals and consumers!
A significant European project, called Human Biomonitoring for the EU (HBM4EU), has been running for the past ten to 15 years across Europe, monitoring chemical exposure, including not only EDCs but a variety of other compounds. The findings reveal a spectrum of exposure across Europe, with various groups experiencing differing levels of exposure. One key lesson from this study is that regulation can effectively reduce exposure. When regulations are enforced, they work.
However, we also face the challenge of new, unregulated compounds entering the market, which can lead to increased exposure to these substances. We need to address this issue carefully; we must not simply replace one harmful substance with another. For example, while we may ban one type of bisphenol, we might inadvertently allow others, such as bisphenol S and bisphenol F, which are equally harmful or even worse than the original compound.
What we know from the HBM4EU study, which the project leaders have communicated over the past two years since the evaluation was released, is that individuals can reduce their exposure to EDCs by 30% to possibly even 50% through changes in daily life, behaviour, and attitudes. There are many well-publicised recommendations, supported by NGOs and official health regulatory institutions.
To reduce your exposure, one leading suggestion is to minimise plastic use in daily life, as plastic is a significant source of EDCs. Additionally, nano- and microplastics pose unknown risks to both the endocrine system and overall health. It is also advisable to avoid body care products, cosmetics, and clothing that contain EDCs.
The consumption of ultra-processed foods and meat significantly contributes to exposure to EDCs and microplastics. To reduce this risk, it’s advisable to prepare meals at home, use glass or metal containers, and avoid kitchenware with water-repellent coatings that may contain and release EDCs during their use. Increasing plant-based food intake, ideally organic, can also be beneficial.
Food production and consumption must become public issues, necessitating regulatory changes. While individual action is important, it can’t be the only solution. Regulatory and consumer pressure must be applied to producers to develop EDC-free alternatives, which is achievable with current technology.
Consumer safety should be prioritised. Tools like the ToxFox app in Germany can help identify products containing EDCs. However, there is a need for harmonisation among eco-labels to guide informed consumer choices. Consumer activism has previously led to positive changes, such as the removal of bisphenol A (BPA) from baby bottles.
Scientists agree that if a group of chemicals is classified as EDCs, they should all be banned and reconsidered before any substitutes are approved. Strict regulations are essential, especially as discussions about loosening restrictions are ongoing in Europe. The EU’s REACH (Registration, Evaluation, Authorisation, and Restriction of Chemicals) process must be revised to better protect public health, preventing any rollback of existing laws regarding EDCs in various products. EDCs should be treated with the same seriousness as other substances of very high concern (SVHC), such as carcinogens, with no exemptions allowed.
Q. Where should future research focus to develop a comprehensive response to EDCs? What actions should be taken at the policy level?
There is a critical need for more research and regulation on EDCs, particularly in understanding their specific properties. Testing EDCs requires evaluation in intact organisms since the endocrine system functions properly only in this context. In vitro methods can help prioritise and screen the most hazardous compounds, but they should be viewed as preliminary tools. After initial screening, further characterisation is necessary using simple model organisms.
It’s vital to demonstrate both adverse and non-adverse effects within living systems and to develop better methods for assessing complex mixtures. This is especially crucial since EDCs can have effects at very low concentrations. We need to study the effects of EDCs at very low concentrations, as these effects can be additive, synergistic, or even antagonistic when mixed. To understand these mixture effects, we must have reliable and validated methods in place.
Additionally, more research is needed on how these EDCs can act in a transgenerational manner. For instance, when a pregnant woman is exposed to these chemicals, three generations – herself, her baby, and the reproductive cells of that baby – are affected simultaneously. We must develop models to test for these transgenerational effects, which can be long- lasting and persistent. This research also requires us to explore novel mechanisms of action, such as epigenetic changes that alter chromatin structure in response to exposure.
Furthermore, it’s essential to address the debates surrounding classical toxicology testing. Hormones do not follow a linear dose-response relationship. In my decades of experience working with hormones, I have observed that their effects often exhibit non-monotonic patterns, such as U-shaped, J-shaped, or inverse U-shaped responses.
Very low or very high concentrations of hormones may both lead to similar adverse effects, whereas an optimal concentration might have minimal impact. Currently, we cannot confidently extrapolate from exposure studies or epidemiological research to determine whether a lower concentration is inactive, especially when combined with other endocrine-disrupting chemicals present at lower levels. There can be additive and synergistic effects that we have yet to explore fully. Testing these interactions requires time and high-quality experimental models, many of which have not been validated.
Validated animal and cell-based models exist for studying, for example, the reproductive system and hormones, but these methods are often insensitive, and their ability to reliably predict risks to human health is debated. In addition, validated methods for assessing the thyroid hormone system, brain development, metabolism, and female fertility are either less reliable or entirely lacking. Validating these processes through OECD guidelines can take ten to 15 years, but we don’t have that time, as exposure to EDCs continues. We have enough data to justify reducing EDC exposure.
We need sound, publicly validated data from governments and health authorities rather than relying on internet sources or misinformation. The chemical industry often pressures regulatory bodies, emphasising economic growth over public health, but this cannot come at the expense of our wellbeing or the ecosystem. Chemical industry, scientists, and manufacturers need to identify and develop chemicals and products that are more sustainable and safe. Innovation, environmental and health-oriented developments in this area could give Europe a major competitive edge versus the US and China!
Many species are threatened by EDCs, alongside other crises such as global warming. This issue is complex and affects not only our health but also future healthcare systems, amid challenges such as obesity and urbanisation. We must take this issue seriously.
