Globally, approximately 1 in 4 human deaths is due to “environmental” factors

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Human sovereignty over the environment is a double-edged sword. For example, on the one hand, advances in science and technology have reduced the number of deaths from infectious diseases worldwide. But on the other hand, some of the pollution has been linked to chronic diseases that erode both our health and our lifespan. Reducing exposure to harmful environmental factors is a major goal of global public health. But there is some confusion about what “environmental” means in other countries.

A team of international researchers, in collaboration with the World Health Organization, recently attempted to assess the share of the global burden of disease directly attributable to environmental risks. Their findings were published in the Public Health Journal.

First, the authors identified what they considered an environmental risk (emphasis added):

For the purposes of this study, the environment includes exposure to pollution and chemicals (eg, air, water, soil, products), physical exposures (eg, noise, radiation), built environment (eg, housing, land use, infrastructure), other anthropogenic changes (e.g. climate change, vector breeding grounds), associated behaviors and working environment. Excluded are lifestyle factors and behaviors that have little or no relationship to the physical environment such as diet, tobacco or alcohol consumption, environments that cannot reasonably be modified (for example wetlands, pollen), or social conditions and unemployment.

Using these general criteria, the authors combined a systematic review of the literature with other less empirical data (such as disease transmission routes but also opinions) to create causation with 133 different diseases and injuries in 2012. In the figure below, the leading causes of death and disability are shown, along with the fraction they believe is attributable to their notion of environmental causes.

Overall, about 56 million people died in 2012. Of these, the authors estimate that 12.6 million people (23%) died prematurely due to what they call environmental hazards. For example, 42% and 35% of strokes and ischemic heart disease, respectively, were related to indoor/outdoor air pollution, lead exposure, work-related stress, and more. (Remember that lifestyle factors such as diet and smoking are not considered “environmental”.) Similarly, 20% of cancers are correlated with pollution, ionizing radiation and exposure to “chemicals”, although they did not specify which ones. (Click here for a table showing diseases and their associated environmental risks.)

The 12.6 million* deaths caused by the environment break down as follows:

8.2 million: non-communicable diseases
2.5 million: infectious, parasitic, neonatal and nutritional diseases
2.0 million: Injuries

From a public health strategy perspective, deaths from infection and lack of adequate nutrition would likely be the “easiest” to deal with. It is certainly simpler to provide people with good food and medicine (which can happen on a timescale of months or years) than to build sewage systems or clean up the environment (which can take years or even decades).

Obviously, the limitation of a study like this is that it relies heavily on estimates and extrapolations and possibly on selection bias in defining the environment, and on the experts they chose to use in addition to the systematic review. Given the inherent difficulty of the task, approximation may be the only way to do it. The fact that the team’s results are similar to those they got from another study they conducted 10 years ago leads them to believe this lends credibility to the method they have. chosen.

The bottom line is that while we all must die, we shouldn’t die from preventable causes. What they are is up for debate.

Update (Sept 26, 2016 3:55 PM PST): There are two issues with this article. First of all, the authors’ definition of the word “environmental” is quite broad since it includes features such as infrastructure. For example, it is unclear how the authors could reliably classify drownings as having environmental or non-environmental causes. Their methodology can be used to overestimate the number of deaths due to environmental hazards. Second, assuming their figures are correct, the authors’ estimate that 1 in 4 deaths worldwide is attributable to environmental hazards is likely due primarily to developing countries. In many parts of the world, for example, people still burn wood or even feces inside their homes for warmth. Obviously, the environmental conditions are much better in the developed world, like in the United States or Europe. It would be quite difficult to imagine that 25% of deaths are due to environmental factors in advanced countries.

Source: A. Prüss-Ustün et al. “Diseases from unhealthy environments: an updated estimate of the global burden of disease attributable to environmental determinants of health.” Public health j. Published September 12, 2016. doi: 10.1093/pubmed/fdw085

*Note: rounding error gives a sum of 12.7 million.

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