The hidden threat of polluted air: physical inactivity
Article written by Katalin Tarr, András Lukács and Aydan Gurbanova, Clean Air Action Group, Hungary
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Largely due to motorised traffic, most public spaces in many cities are not suitable for pleasant and safe walking, cycling, and exercising due to the polluted air, noise, and lack of safe, enjoyable, and green areas. As a result, many people lead sedentary lifestyles, which is one of the main causes of various illnesses and premature deaths.
© Lola Aladzsits-Milus
According to the World Health Organisation (WHO), globally, nearly 1.8 billion adults are at risk of disease from not doing enough physical activity. In the EU, increasing physical activity to the minimum levels recommended by WHO would prevent 11.5 million new cases of non-communicable diseases (NCDs) by 2050, including 3.8 million cases of cardiovascular diseases, 3.5 million cases of depression, nearly 1 million cases of type 2 diabetes and more than 400 000 cases of different cancers. Meeting the target of 300 minutes of physical activity per week would prevent a further 16 million cases of NCDs. Physical inactivity is one of the main causes of overweight and obesity which are responsible for more than 1.2 million deaths annually in the 53 countries of the WHO European Region. In the U.S., sedentary lifestyle causes 200,000 premature deaths per year and contributes to low health outcomes and high healthcare costs compared to countries with similar economic performance.
Sedentary lifestyles also take a colossal financial toll: in the U.S., the average annual healthcare expenditures are 32% lower for those who achieve physical activity targets (USD 1,019) than for those who are sedentary (USD 1,349). According to the Centers for Disease Control and Prevention (CDC), the healthcare expenditure directly linked to sedentary lifestyles amounts to USD 117 billion per year. In Europe, too, the costs of physical inactivity are enormous: according to the UK’s Centre for Economic and Business Research (CEBR), widespread physical inactivity costs the European economy more than €80 billion a year.
Due to the widespread use of motor vehicles, people do far less physical activity than in earlier times. Many people are obviously reluctant to walk, bike, or do other forms of exercise – whether for daily transport, or leisure – in places where motor vehicles pollute the air, make noise, and occupy the scarce urban space. Parents are often afraid to let their children go out alone as the streets are no longer suitable and safe for pedestrian traffic. For example, according to the German Transport Club (VCD), in Germany, 79 % of the children living in streets with traffic calming, play outside while for children in streets with heavy traffic, this proportion is only 18%. Thus, as streets became unhabitable, people spent more and more time indoors, often sitting in front of the television and computer.
The same street in Budapest 60 years ago and today (Photos by courtesy of Árpád Kiss-Kuntler).
As public spaces have been more and more surrendered to motorised traffic, a vicious circle has begun: more and more people, who once walked or cycled for daily transportation have switched to driving cars. As car owners were able to commute longer distances, many of them moved to more remote locations to escape the polluted areas, further increasing daily car traffic, and its cascading negative effects – air pollution, noise, and an often-overlooked consequence: a less physically active and, therefore, less healthy lifestyle.
Several studies demonstrate the negative impact of car use on physical activity levels. For example, active daily transport results in significantly higher energy expenditure by the human body – not just through walking or cycling, but also when using public transport – as opposed to car use, where the body’s energy consumption barely exceeds that of resting levels. This was shown, for example, by a study in Cambridge, UK, which measured the energy consumed by the bodies of people who commute to work by car, walking, cycling or public transport. For one week, 182 adults used GPS and heart rate measurements to measure how much energy (MET) their bodies consumed during their commute to work. The measured energy expenditure was 1.28 MET for driving, 1.78 MET for bus travel, 4.61 MET for walking and 6.44 MET for cycling. Thus, the energy expenditure of commuters by car was therefore significantly lower than for other modes of transport.
The metabolic cost (MET) of different modes or combinations of modes of transport on the commute based on research in Cambridge, UK. (MET: Metabolic Equivalent of Task is the amount of energy the body consumes. One MET is the amount of oxygen consumed while sitting at rest, which is 3.5 ml O2 per kg body weight per minute. An example of how MET is calculated: a 70 kg person walking briskly burns these many calories in 1 hour: 6 MET=6 kcal/kg/hour; 6 kcal/kg/hour×70 kg=420 kcal/hour.)
An analysis of the health benefits of public transport by the Victorian Transport Policy Institute in Canada found that in the U.S., where the vast majority of the population lives a car-dependent lifestyle, fewer than half of the adult population do the moderate-intensity physical activity – such as brisk walking – of at least 22 minutes a day recommended by the U.S. Centers for Disease Control (CDC). However, the majority of public transit commuters do complete this recommended amount, walking an average of 19 minutes to and from stops, and they are also more willing to travel to destinations other than their daily commute by more active means without a car. This time is well above the US average of just 6 minutes per day!
A study in New York City, using pedometers and questionnaires, showed that commuters by train walked 30 percent more, walked 10 minutes or more frequently, and were four times more likely to take the recommended 10,000 steps per day to maintain health than commuters by car. Another study found that New York City residents have a much lower Body Mass Index (BMI) when they live in areas with higher densities of subway and bus stops, higher population density, and more diverse land use. (The Body Mass Index or BMI indicates the extent of obesity. It is calculated by dividing body weight in kilograms by the square of body height in metres.)
A study of the walking habits of 1,237 randomly selected adults in the Seattle and Baltimore metropolitan areas in the USA found that people who use public transport to get to work do on average 5-10 minutes more moderate-intensity physical activity per day and walk more to destinations around their homes and workplaces than people who drive, regardless of how pedestrian-friendly the neighbourhood is. A study in Atlanta also found that people who use public transport walk more and for longer distances and are more likely to meet physical activity recommendations than people who do not use public transport. The analysis showed that public transport users walk an average of 1.7 kilometres per day, which is roughly two-thirds of the recommended amount of physical activity and ten times as much as non-public transport users walk per day – just 160 metres. The predisposing effect of public transport use on walking was found across all income groups.
In a further study, the relationship between commuting patterns and changes in body mass index of nearly 6,000 adults aged 40-69 was followed over four years in Cambridge, England. The body mass index of those who switched from public transport to car increased by 0.3. Those who switched from car to public transport experienced a decrease by 0.3.
Australian researchers’ modelling suggests that increasing the frequency and multi-directionality of public transport in Melbourne, a low-density and sprawled city, would have significant health and economic benefits. It would improve the physical activity of the population (by an average of 6.4 METs per week), reduce body weight, increase the number of healthy life years, and reduce health costs.
Drawing from a large body of international research, the expert organizations have produced numerous studies on how to transform the structure and transport of cities to get people more physically active. For example, the WHO’s 96-page study Towards More Physical Activity in Cities: Transforming public spaces to promote physical activity recommends improving the conditions for walking and cycling as well as access to green areas and public transport. Overall, when considering the impacts of car-based lifestyles and cities, it is important to look beyond well-known issues like air and noise pollution, and traffic accidents. The less obvious consequences—such as the decline in daily physical activity and the resulting health risks—must also be acknowledged.