There is increasing evidence that the quality of our homes and cities is a critical determinant of cardiovascular disease, diabetes and lung conditions. As urbanization and economic change occur globally, whether we live in a house free of dust in a city with open parks and traffic regulations, or in a dusty tenement building next to a major road, seems critically correlated with our likelihood for having shortened life expectancy, poor nutrition, heart disease and lung problems. In this week’s blog post, we look at some of the mechanisms relating the “built environment”—our human-made surroundings of daily living—to the risk of illness. We ask the question: can we do for our hearts and lungs what the Bauhaus movement did for functional design?

Indoor air quality

If Dwell Magazine had a feature edition on designing a healthy home, they’d have to tackle the major issue of indoor air quality. Much research on the built environment’s impact on health was revealed through a series of studies on asthma among children living in low-income public housing units in the United States. Poor indoor air quality resulting from dust and dirt in public housing units was a major cause of emergency room visits during the 1980’s and 90’s among these children, leading to new programs for housing quality checks and maintenance, which we featured in a previous post.

A parallel concern about indoor air quality has been highlighted in the global health realm because of “dirty cookstoves”—the wood-burning stoves that many people in Asia, Africa and Latin America use to cook food indoors. Most people who use these stoves don’t live in an area where it’s easy to cook outside, or don’t have the funds to convert to a gas-burning stove, so wood smoke (just like from a campfire) accumulates in the home, where (usually) a woman is cooking for several hours a day, sometimes with a child strapped to her back. The studies on this cause of indoor air pollution reveal that the wood smoke significantly impairs the immune system; an Indian study found that those exposed are 2.5 times more likely to experience tuberculosis, and infants are 2.2 times more likely to acquire a respiratory tract infection, one of the leading causes of death among children worldwide. Lung cancer and emphysema have been similarly observed to increase in frequency among users of these wood-burning stoves, and the particulate matter from them acts as an eye irritant, leading to a 1.3-fold increase in the risk of cataracts among those exposed.

In part due to the work of Professor Kirk Smith and others at Berkeley, improved stoves have been designed and deployed in a number of countries. See here for some of the representative designs. Costs for construction and installation of improved stoves typically range from $1.20 to $5 per unit. Even developing better ventilation without a new stove can improve outcomes, as evidenced by the use of simple chimneys.

Environments built for activity

More recently, the continued rise of obesity has led to a series of research studies on how urban design, both in individual homes and in larger neighborhoods, can critically determine whether people will engage in physical activity to counteract the impact of living increasingly sedentary lifestyles in front of computer or television screens.

One of the principal challenges to encouraging physical activity has been to create urban spaces that are conducive to, and safe for, walking or biking. A variety of people have created “walkability” scores to assess how easy it is to avoid major roads and access clear walking paths in a neighborhood. The safety of walking and biking seems to be a critical determinant of whether people will engage in these activities, especially in low-income neighborhoods and in areas with heavy road traffic.

In the past, zoning laws were used to prevent mixed use of land, such that living and working and playing in the same spaces was nearly impossible; in fact, public health practitioners supported such zoning to reduce the spread of tuberculosis and separate homes and schools from toxic chemicals spewing out of abattoirs and tanneries. The growth of the suburbs then followed with the invention of the automobile to separate people from work and play even further. But newer studies show that a focus on making urban environments more hospitable for living (rather than focusing on suburban development) can improve physical activity outcomes and subsequent cardiovascular disease; mixed-use neighborhoods (those with shops, homes and businesses in one area) have more destinations worth walking to, and seem to reduce crime while promoting exercise. This may also be because of greater access to fitness centers and changes in social dynamics to encourage healthier eating, according to two studies showing that the significantly lower obesity rates in mixed use areas were not just a result of physical activity improvements.

Living in a neighborhood with higher crime is also associated with less desire to get out of the house to do physical activity and increased coronary heart disease prevalence even after controlling statistically for individual-level income. The ability of children to play safely outside is a critical determinant of whether their parents will let them do so, and subsequently whether they develop obesity. These and other related principles have been captured in the “new urbanism” and “Smart Growth” movements.

Food environments: access is necessary, but maybe not sufficient

Concordant with the research on physical activity is research on nutrition. We discussed food desserts in a previous post, in which we described how limited access to healthy foods and supermarkets makes it difficult for many people to defer junk food at the neighborhood gas station instead of traveling far for a healthy meal.

But new research also suggests that while better access may be necessary for improved nutrition, it may not be sufficient to change people’s consumption patterns. Even as more nutritious food has become a focus of city programs, there is evidence that people have not converted over to it, perhaps because the almost ‘addictive’ nature of junk food. Something else is going on socially that explains why increased access to supermarkets doesn’t seem to be sufficient to improve nutrition. Curtailing neighborhood fast food outlet density, for example, doesn’t have as much impact as we had assumed in the past, and similarly improving supermarket availability doesn’t seem to confer as much benefit as we thought. Actually promoting change in what food people select, after facilitating access, seems to be the next step, but this requires further investigation into variables like what economic and social factors are playing into individual-decision making (like food taxes, which we discussed in a previous post).

Back to basic infrastructure

While the social factors affecting food purchasing are difficult to tackle in urban design, an even more difficult challenge is class politics. In his legendary book Planet of Slums (which we highly recommend as essential reading for anyone concerned with public health), Mike Davis reviews the evidence that rapid and unprecedented urbanization is leading most people to live in high-concentrated living environments. In this context, it’s important not to get carried away in thinking that all healthy design should focus on the needs of sedentary people in high-income countries. About one billion people still live in slums today, and the basic infrastructure needed to support a healthy life in these communities is sorely lacking.

As revealed by the Sinai fire in Nairobi last September, slums are regularly haunted by the fact that they are built as shantytowns—essentially as perpetual occupations of the poor over the only land they’re allowed to live on. As a result of their essentially un-planned design and undesirable land characteristics, dangers lurk around every corner in these communities. Electrical lines and (in the case of the Nairobi disaster) oil pipelines are directly next to living spaces, posing grave dangers for injury. In the Nairobi pipeline disaster, 75 people were killed and 112 badly burned after an oil pipeline leaked and exploded, setting sewage on fire and hurling exploding vapor through makeshift homes that directly abutted the line. Many politicians assumed that pushing people out of this kind of environment—rather than building better infrastructure within the slum—would solve the problem. After Nairobi’s fire, dozens of slum homes were razed by bulldozer in an attempt by the government to claim they were protecting people from further harm; those displaced by the bulldozing occupied an already-settled area, worsening crowding, violence and a provoking a deadly stampede.

But when there’s nowhere else to go, the question is not how to push people off the land, but how to make the land more hospitable. The most common focus for such infrastructure improvement is, unsurprisingly, sewer systems and water quality. One of the more inspiring movements in this realm is “Community Led Total Sanitation” (CLTS). Rather than creating standardized toilet designs, providing hardware subsidies, developing educational modules, and spending money on the other usual development junk, the CLTS approach has been a social movement around…well… shit. The approach is to facilitate communities to analyze their own defecation patterns and problems (sometimes with embarrassed guffaws), present the findings to each other through community forums, and move into the realm of community-driven intervention. Sometimes the work fails, but a lot of times it’s succeeded in overcoming local and regional politics and building some real sanitation infrastructure.

The CLTS successes in Bangladesh, for example, highlight for us that not all design comes from thought experiments among elite architects. Kamal Kar, one of the pioneers of the movement, reminds us that some guts and commitment are needed to design our homes and communities in a participatory manner, and that we might import insights from programs like CLTS into our higher-income countries: