We have learned to think that genetics and personal choices determine our health. In contrast, the impact of living environment on human health has received little attention. Green living environment can provide holistic solutions to public health problems.
Also living environment affects human health
I have always been interested in human health. Initially, my interests were mainly in the appropriate amount of exercise, the best ratio of Omega 3 and 6 fats, and the reduction of harmful inflammation with an optimal diet. Today, I think more broadly: health is not just the result of our choices.
Towards the end of my biology studies, I was fascinated by the health effects of everyday chemicals. I ended up doing my master’s thesis on the environmental impact of the world’s most widely used agrochemical. I realized that our health is also affected by factors that are difficult or impossible for an individual to control. Exposure to some chemicals and air pollution are undeniably harmful to humans. But soon my understanding about the determinants of human health was further advanced.
A study published by Ilkka Hanski in 2012 showed that teenagers who grew up in green living environments developed less allergic sensitization. The protective effect appeared to relate to microbes present in green environments. Previously, I had not considered that the urbanization and westernization not only increase exposure to the risk factors of human health but also reduce exposure to the protective factors.
Nature is a strong health promoter
What is a healthy person like? More than 70 years ago, the World Health Organization defined health as not just the absence of disease but a holistic state of physical, mental and social well-being. Today, we know that nature supports all these aspects of health.
There are numerous examples about the health benefits produced by nature. Even a short trip to nature reduces blood pressure, heart rate and stress, a green view from the hospital window promotes the patient's healing, children's ability to concentrate increases in the lesson kept outdoors, social interaction between parent and child improves in green area, mental problems tend to occur less in rural areas than in cities, premature birth is less common in in green living environments, asthma and allergic diseases are less common in rural than in urban children.
Despite this strong evidence, I often face the underestimation of health benefits produced by nature. On the other hand, I understand the questioners, because our understanding of what is the biological cause behind natural health benefits is limited. This is probably because in nature people are simultaneously exposed to few risk factors of health and plenty of health-promoting factors. In nature, exposure to air pollution, noise, and light pollution decreases, while exposure to sunlight increases, exercise rises, and social relationships are maintained. This diversity of effects are challenging to study.
The invisible connection between nature and health
I am particularly interested in the invisible connection between nature and health. In Ilkka Hanski's study, natural microbes promoted health. Particularly extensive research evidence shows that increased exposure to natural microbes in rural areas, farms, and nature daycares supports the development of children’s immune systems.
However, in addition to microbes, there are other (almost) invisible factors in nature that affect health. Interesting example are allergens. We know that pollens, animal dander, and food molecules, known as allergens, can cause dangerous allergic reactions in those who are sensitive to them. However, studies have found that if people get exposed to those very early in life, allergens may protect against the development of hypersensitivity. For example, in rural areas, children are less sensitive to plant pollens than in urban areas.
There are often odors in natural environments. The scent of pine forest on a hot summer day is my personal favorite. Odors are generated by volatile organic compounds produced by plants. There is still little evidence of their health effects, but animal experiments have shown that they can reduce both stress and inflammation. It is possible that smelling and inhaling these compounds explains some of the health effects of nature.
Equally health living environments
People are not on an equal position regarding the healthiness of their living environment. For example, quitting smoking is more difficult if the nearest store is within walking distance of the home. Moreover, obesity researcher Aila Rissanen emphasizes that obesity is a product of our living environment. We have created an environment that does not make healthy choices, such as everyday exercise or good food choices, easy. Recognizing that an individual’s health is closely linked to the qualities of living environment, we can find new, effective ways to improve public health.
After listening the ideas of Rissanen, I was wondering how big is a role the reduced greenness of living environments in the increase of non-communicable diseases. People and green nature are less and less commonly in the same place, especially accidentally, while doing everyday activities. Nature has become a place where people must especially go. Organizing nature tours becomes more difficult if they require a lot of time and planning, perhaps also a car and affluence.
We know that a single visit in nature has an immediate impact on our well-being, but only regular and abundant visits in nature are enough to promote health in the longer term. For this reason, cities should rethink the suitable location of green areas. How much could we reduce the incidence of non-communicable diseases by making our living environments greener? On the other hand, nature outside living areas of humans is also important to our health. The fragmented natural areas in cities can only flourish for the benefit of man if the great network of nature is well outside of them. This is also ensured by Ilkka Hanski's nature network.
Jenni Lehtimäki Finnish Environment Institute
Jenni Lehtimäki, PhD, works as a Senior researcher at the Finnish Environment Institute. She did her dissertation together with Ilkka Hanski on the biodiversity hypothesis. Jenni continues to explore the topic and is looking for ways which enable a healthy living environment and lifestyle.