Friend and Board Member of Black Swan, Professor Michael Depledge of the University of Exeter shares his research and thoughts on how our environments influence our health and wellbeing. 

Introduction: The Great Transition

In contemporary societies, concerns centre on having a job, generating an income, having an enjoyable lifestyle and avoiding dangers such as terrorism and crime. Much less attention is paid to risks posed by progressive global and local environmental change. Forty thousand years ago, the natural environment played a dominant role in the daily lives of ancient humans. Environmental circumstances were overwhelmingly important in determining survival. Each day people awoke in nature, obtained their food and water from surrounding ecosystems, used nearby natural resources to meet immediate needs and for trading, and faced up to environmental threats from wildlife, infectious diseases, natural toxins, storms, earthquakes, droughts, floods, etc. The intimate interconnections between the environment, human health and wellbeing were obvious and all encompassing; and so it has remained throughout almost all of history. Only over the last 200-300, during the period of industrial development referred to as the “Great Transition”, has widespread awareness of our dependency on the environment gradually diminished1. Recent testaments to this are that public opinion surveys show that in western societies, environment and climate issues are of relatively low interest or concern, compared to the economy, cybercrime, terrorism and infectious diseases. Interestingly, the latter topic is seldom even perceived as an environmental threat, even though it may have deep environmental roots.

Another key feature of the “Great Transition” is that the technological advances led to an unprecedented surge in the growth of the human population. For most of human history there have been around ½ billion people on Earth, but by the early 1800s, the population had risen to 1 billion for the first time. Over the following 215 years it has climbed to ca. 7.3 billion 2. This change coincided with an unprecedented rise in global economic activity. Use of energy and natural resources increased exponentially and waste production escalated uncontrollably. Growth was and is, so extreme that it has led to dramatic changes in the natural world. For example, the use of fossil fuels has resulted in massive greenhouse gas emissions that have driven climate change, while habitat destruction and the overexploitation of animals and plants has caused huge losses of biodiversity. As chemical production has intensified to meet our demands for pesticides, pharmaceutical and industrial products, widespread pollution has occurred. With regard to the latter, over the last 75 years production of chemicals has increased 2500 times, with associated increases in exposure of the human population to an ever widening variety of substances, in an infinite number of mixtures.

Demographic change and its consequences

Despite numerous examples of the damaging effects of human-generated environmental change on our health and wellbeing (e.g. heavy metal and pesticide poisoning, nuclear accidents, extreme weather events associated with climate change), the average lifespan of most people worldwide has increased. Indeed, it has been pointed out that we are the longest lived, healthiest, wealthiest people ever to have existed3. But this does not reveal the whole story, and it may not represent an accurate view of what to expect in the future.

There is mounting evidence that levels of environmental chemicals in our bodies are increasing with age, both in terms of the amounts and varieties of toxic contaminants. As we live longer, we are accumulating higher pollutant concentrations in our bodies than ever before4.

There are even suggestions that the chemicals we accumulate will eventually limit further increases in lifespan. Whether or not this is true, there is a rapidly growing body of scientific data demonstrating associations between specific chemicals and changes in the incidence of particular diseases. For example, accumulation of some heavy metals have been associated with impaired neurological development in children, while the plasticiser, bisphenol A (BPA) has been linked to a higher risk of type 2 diabetes, heart attacks and strokes5. Perfluorinated compounds, such as PFOA which is found in items such as non-stick frying pans, appear to be linked to thyroid disorders6 and pesticides exposures may be associated with the development of type 2 diabetes7. Very many other examples could e mentioned, but it is important to emphasise that while these associations exist, very often the causative mechanisms involved remain obscure. It is reasonable nonetheless to pose the question “is exposure to environmental chemicals resulting in changes in the incidence and patterns of diseases on global scales?”

To return to an earlier point, although we may be living longer, the quality of our lives continues to be affected by a wide range of diseases, creating disability, reducing our wellbeing and generating an increasing financial burden as treatment costs soar. Diseases such as diabetes, depression and dementia have all been linked to some degree to exposure to environmental triggers.

Pharmaceutical Fears

Another factor that has contributed to increased longevity is the enormous progress that has been made in the use of pharmaceuticals. A wide variety of diseases can now be treated successfully, or better still, avoided through the use of drugs. Examples include a range of cancers, cardiovascular disease, respiratory diseases and metabolic disorders. There have even been calls for all the older members of the population (e.g. the over 50s), to be given a combination of drugs to ward off hypertension, diabetes and strokes in later life (the so-called “Polypill”). Here again, demographic change may result in some unintended consequences. It is noteworthy that if the number of different pharmaceuticals currently used is considered in relation to different age groups in society, then a very steep rise in usage is observed in the over 50s. In Western Europe, North America and Japan, it is particularly clear that populations are ageing in ways that are increasing the proportion of senior members in our societies. Taking these two trends together, it seems certain that overall pharmaceutical use will grow rapidly over the next 10-20 years8. Furthermore, when medicines are taken, they are often not wholly broken down in our bodies. The metabolites that are generated remain biologically active. Consequently, a significant proportion of drugs and their residues are excreted into the sewage system. Most sewage treatments do not break down the pharmaceutical waste products which are then are discharged into the environment, potentially causing ecological damage. The human waste pharmaceutical load is added to the environmental pharmaceutical load arising from their use in veterinary medicine, animal husbandry and fish farming. It has been estimated that about half of the pharmaceuticals in the environment enter via this latter route. The overall availability of pharmaceuticals around the world is also increasing rapidly as licenses restricting manufacture expire. New generic medicines can be produced very cheaply and are readily available in China, India, South America and elsewhere, where they can be bought freely over the counter, without a prescription. Whether pharmaceutical residues reach environmental concentrations that pose threats to humans and wildlife is a controversial issue. Some suggest that levels will be too low to produce biological effects. However, there is already evidence to the contrary (see below).

As well as general concern, there is one specific pharmaceutical issue that is generating great alarm. Antibiotics used in the treatment of infectious diseases are losing their effectiveness as bacteria and other microbes develop resistance to them. The consequences for medical practice are enormous. Simple infections will no longer be readily treatable. This is widely regarded as a problem generated in health care settings where antibiotic resistant organisms emerge due to the widespread use of antimicrobial agents. However, it may be that resistant organisms are also being selected out in the environment, following low level exposure to antibiotic residues. If this is the case, it represents another challenge that we must deal with9. The Chief Medical Officer of the United Kingdom has identified antibiotic resistance as a serious global threat on a scale similar to that of climate change. By 2050 it is estimated that up to 10 million people may die each year from this cause.

It is not just humans who may experience adverse effects from pharmaceuticals in the environment. There are also threats to a range of wildlife species. For example, residues from the use of contraceptive pills passing through the sewerage system into rivers have resulted in the feminisation of fish with damaging ecological consequences. Similarly, the anti-inflammatory drug, diclofenac, used in the treatment of cattle on the Indian subcontinent, has led to the deaths of an estimated 3 million vultures.

Emerging technologies: the case of nanomaterials

The perceived need to generate ever more economic activity around the World drives innovation and the creation of new technologies. One that has emerged strongly over the last 20 years is nanotechnology. The discovery that the properties of the bulk form of chemicals are transformed on the nanoscale, opened up exciting possibilities for producing new materials than can be used to develop a wide variety of new products and devices. This includes an array of new cosmetics and sunscreens, fuel additives, medicines, paints, water purification devices and fabrics10. More than ca. 3000 products that are now widely available that contain nanomaterials. So far the manufacturers claim that nanomaterials pose little risk to humans or the environment. However, they fail to point out that current methods for testing the toxicity of nanomaterials are inadequate and unreliable. This prompted the Organisation for Economic Cooperation and Development (OECD), with the backing of many industrialised nations, to embark on a programmes to develop more appropriate, effective, accurate tests. Currently, environment agencies are unable to routinely measure and monitor nanomaterials in the environment or in animals (including humans) or plants, because routine analytical techniques are not widely available. Consequently, we have little idea as to where nanomaterials accumulate in our ecosystems, or how they interact with other chemicals, or how long they persist, or what their ultimate fate will be. We are simply unable to determine whether or not they pose a significant threat. In the meantime, the number of uses of nanomaterials is increasing rapidly.

The scenario described above is often repeated when new materials and technologies emerge. Great excitement about the innovations that a technology promises are tempered over time by concerns about what threats the technology might pose to the ecosystems and human health. As research proceeds, knowledge accumulates providing the basis for regulations, allowing benefits to be realised and damaging effects to be avoided or minimised. As Linkov and Satterstrom have pointed out however, 10-15 years often elapse between the emergence of a new technology and its effective regulation and safe management11. During the interim period, the public are often inadequately protected from potential health threats.

Benefits from the environment for human health and wellbeing.

The foregoing discussion has focussed mainly on health threats arising in the environment. However, the natural world also represents an important resource that can be employed in our efforts to foster improvements in public health. The World Health Organisation has identified obesity and mental health disorders as the two great contemporary epidemics that must be tackled now and in the coming years. In western societies (and in many other regions of the World) this reflects, in part, a reduction in time spent outdoors, being physically active and experiencing natural settings (parks, river and canal walks, lakes, seashores, woodland, countryside, etc.). Evidence from a wide range of studies suggests that being in or near to nature helps individuals to meet daily exercise requirements and also contributes to stress reduction, and lowering of blood pressure and heart rate. Depressive disorders are the leading cause of disability in middle to high income countries, rendering mental health and wellbeing a critical modern public health issue. This trend appears to be related to increased urbanisation, as ca. 80% of people in the world’s more developed nations now reside in towns and cities. Natural spaces aid stress reduction, so reduced access makes matters worse12. Delving deeper into this issue reveals that spending time near water (ponds, rivers, canals, lakes and seashores) is especially beneficial for health and wellbeing. For example, a study in the UK found that, allowing for confounding factors, self-reported health was best in individuals living within a few kilometres of the coast 13 .This effect was particularly pronounced in poorer socio-economic groups.

In another study, moving to greener urban areas was related to sustained improvements in mental health, suggesting that environmental policies to expand urban green and blue space may generate sustainable public health benefits. These findings, together with those of many other smaller studies, provide a weight of evidence in support of the view that time spent in natural settings can indeed lead to improvements in health and wellbeing, at least in temperate regions. A variety of initiatives based on this evidence have been launched, such as the establishment of “green” and “blue” gyms. These involve encouraging those who would not normally spend much time outdoors, to participate in new activities such as gardening and hiking, or in the case of blue gyms, swimming, surfing and kayaking as well as coastal walks and rockpool rambles. Although the mechanisms by which benefits are derived are still only partially understood, data is accumulating that suggests that benefits can be substantial, both for individuals and populations. A systematic review of studies revealed that outdoor exercise carries with it additional benefits for mental health compared to exercising indoors. Research in this area is gathering pace, but there is much still to do. Larger studies capturing health benefits need to be performed rigorously using robust experimental designs. Objective comparisons with other pursuits and their potential health benefits also need to be performed. Recently those engaged in evaluating the economic value of natural capital (i.e. forests, seashores, countryside) have turned their attention to the value of nature in relation to health, and associated reductions in the costs of health care provision. This is an important initiative since economic factors strongly influence policy decisions. If the use of natural settings can be shown to be directly linked to improvements in health, and reduced use of costly healthcare services, then no doubt policymakers will make greater efforts to reconnect the public with nature. Other research has also begun looking at the non-economic value of nature for health and wellbeing. This is vital because many aspects of life that people value are difficult to quantify economically, such as their feelings about wildlife, or beautiful natural settings, or walking in a forests or on a seashore. These non-economic values must be taken into account during policymaking. Developing a means of doing so may help in improving wellbeing and protecting mental health.


In summary, the environments in which we live play a major role in determining our health and wellbeing. In the past, public health researchers have tended to focus on local environmental conditions, including exposure to pathogens and to local sources of chemical pollution. However, in recent years, the influence of global issues such as climate change, biodiversity loss, insidious low level chemical pollution, pharmaceuticals in the environment and the emergence of antibiotic resistant microorganisms demand more attention. All of these threats must be considered in relation to the lifecourse, and to demographic change, most notably, the ageing and urbanisation of populations in many industrialised nations. The intimate relationships that humans have had with natural environments throughout evolution has been gradually weakened over the last 200-300 years, but emerging evidence suggests that spending sufficient time in nature may help to combat many of the problems that are linked to contemporary lifestyles, including obesity and psychiatric disorders. The widespread realisation that human health and wellbeing fundamentally depends on living in sustainable environments, with access to aesthetically pleasing, biodiverse, green and blue spaces, is an important step in the further evolution of human societies.

Note: a version of this article will appear in the Journal of the Japanese Society of Travel Medicine (2016).


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Michael Depledge is Professor of Environment and Human Health at the University of Exeter Medical School, England. He has a PhD in marine biology, a DSc for his work in toxicology and is a Fellow of the Royal College of Physicians. He worked on environmental pollution problems before developing an interest in radiation and drug toxicity in cancer patients. He served as the Chief Scientist for the Environment Agency until 2006, before establishing the European Centre for Environment and Human Health. Michael is an advisor to the UK Government (DEFRA), the World Health Organisation and the Board of Black Swan.