The link between the health of the population and its environment is a fact that hardly anyone calls into question, yet at the same time, the specific effects of environmental factors on human health remain unknown. To what extent is our health affected by the environmental conditions in which we live?

Several studies conducted halfway through the last century confirmed that the environmental component is responsible for approximately 25% of morbidity and mortality worldwide. This percentage of environmental factors is lower in more developed countries and higher in developing countries. In addition, studies produced by the World Health Organisation (WHO) on the various risk factors continue to include environmental factors as one of the main agents contributing towards health.

What are the environmental factors that influence or exert an impact on our health?

Environmental factors that influence disease and health have been changing over time. Today, in a developed country like the Basque Country, environmental factors are those related to the quality of the water we consume or use to take a shower, the quality of the air both outside (traditional atmospheric pollutants mainly produced by traffic, industry...) and inside (pollutants arising from the materials used for construction, paints, varnishes or products we use for cleaning surfaces or even for personal hygiene), soil pollution...

And then there are the thousands of chemicals on the market that are widely used in industry and in the manufacture of textiles, materials, hygienic products... We are exposed to all of them through our diet, through the creams, soaps and so on that we use. They reach us in very small quantities, but we are exposed to many substances.

Right now, endocrine disruptors constitute a highly significant group within chemical substances. The World Health Organisation (WHO) itself considers them to be a key element to be studied, to find out whether or not they have an impact, what effects they produce and how to deal with them from the perspective of prevention. In both public and environmental health, it is essential to know in order to try to prevent.

Endocrine disruptors are currently a significant group and are subject to an internationally established priority...

Yes, that’s correct. They aren’t the only ones, but the effect of disruptors is regarded as significant because, to put it more dramatically, it has to do with the very survival of the species. An endocrine disruptor is a substance that acts like a hormone, so it may be able to disrupt the hormonal balance within the body, and hormone balance is essential in the physiology, survival and development of any organism. These substances that act in the way hormones do may be impacting the sexual differentiation of an organism, adolescence, fertility, sperm quality and quantity...

And what are the health problems caused by environmental factors?

Since there are biological, microbiological, chemical, physical and environmental factors, they are associated with almost every type of disorder. Endocrine disruptors, for example, may be a risk factor in hormone-dependent cancers such as breast, testicular or prostate cancer. But environmental factors, on the whole, may cause cardiovascular disease, diabetes, skin disease, respiratory disease, alterations in the neuropsychological development of children... Several studies show that even in pregnancy, a mother's exposure to environmental risk factors may lead to alterations in the neuropsychological development of her child.  However, we would argue that they do not cause as many infectious diseases, since the transmission of infectious diseases through food and water has been greatly reduced by improved water treatment technologies, improved food handling and cold chains, etc.

How could we take care of our health in the face of these environmental factors?

The linchpin is knowledge. Finding out what a high, low or acceptable health risk is and what disorders each element is related to. As I said before, our main strategy is prevention, so that these exposures do not occur, and if they do occur and are at a sufficient level to cause deterioration or disease, because it does not always have to be the case, and necessitate clinical treatment. But, I repeat, what we must try to do is not to let these risk factors accumulate and try to prevent them from causing a disease or disorder in the first place.

To find out, to inform professionals and the general public and to promote or force certain things not to be carried out or to strongly advise against the use of certain substances. There are many strategies. We have a clear example of what we are talking about: tobacco. Tobacco has been and probably remains one of the main risk factors in our society. Apart from knowledge and the very decision to change behaviour, the increase in the price of tobacco and the prohibition of its consumption in all public places have been the key elements in improving or at least reducing tobacco consumption.

There are other environmental factors...

Yes, there are. The city itself, for example, is a factor that may lessen or increase the environmental exposures to which we are exposed. Green and blue surfaces, such as the sea, rivers and lakes are elements that can contribute towards health because they reduce other environmental exposures, such as noise or air pollution, improve people's connection in meetings and socialisation; at the same time, they can prevent the onset of mental illnesses such as anxiety, depression etc.

The Summer Course ended with a roundtable discussion on Effects of the city and the social context on human health, which you chaired. Today, most people live in cities. What should a city be like to live a healthy life?

A city is not just something built on a surface; it is something that includes urban development together with the population that lives in it, their culture, political convictions, socio-economic conditions... The city has architectural and urban components, but also biological, social, cultural and anthropological ones. So, the best context of what is healthy may not be exactly the same in one environment as in another.

Living close to green or blue environments (sea, rivers, lakes,...) can act as an anti-stress component, regulate undesirable environmental exposures, restore cognitive functions, encourage de-stressing or provide a space to come into contact with nature. This means that city design can improve our health. It can lead to more or less walkability, to more or fewer green and blue environments, it can encourage taking physical exercise, it can facilitate our motivation...

What is a healthy city?

A healthy city is one that promotes health through actions that exert a strong influence on health, e.g. urban planning, air quality, housing, education, equity,... A healthy city has to be a city that allows the development not only of individuals but of the group as a whole.

The Covid-19 lockdown is a prime example. Didn't the person who had a garden or a terrace feel better? Didn't that person feel better when his or her windows looked onto green spaces rather than onto inner courtyards? It has to be an enabling space that promotes personal and collective development and is committed to health.

How healthy are our cities?

Gasteiz is an internationally-recognised healthy city. A model city in terms of urban planning, green environments, etc. The city with the most green spaces and the best environmental quality is undoubtedly Gasteiz. Probably, the characteristics of Donostia, due to its location on the coast, its size and cleanliness, would put it in an intermediate position. And, finally, Bilbao just because of its very size, density and its industrial history. The problems of the urban environment and pollution do not occur exclusively in cities; it is curious, but as in most towns in the Basque Country, everything is mixed within the same kilometre: roads, industry, green spaces, housing and parks... Our environment is complex.