Environmental factors play a surprisingly large role in the disease burden with which humankind must cope.

Figure 1. Global Deaths and Disability-Adjusted Life Years Attributable to the Environment. Source: Prüss-Ustün et al, 2016.

In 2012, 12.6 million deaths worldwide (22.7% of all deaths) were attributable to environmental causes, as were 596 million disability-adjusted life years (DALYs) (21.8% of all DALYs)*. (Figure 1) So says a report issued in 2016 by the World Health Organization. I reviewed some of the report’s findings in the previous post. In this post, I turn to its findings regarding specific disease conditions.

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Figure 2. Source: Prüss-Ustün et al, 2016.

The report authors found that 13 types of diseases or disease groups had the highest preventable disease burden from environmental risks. Figure 2 shows the raw number of DALYs attributable to environmental factors by disease group. Cardio-vascular diseases account for the largest disease burden worldwide, causing 119 million DALYs in 2012, some 60% more than unintentional injuries, the second largest category. Road injuries were counted separately from unintentional injuries, however. I suspect that road injuries are mostly unintentional (though road conditions and driving habits may sometimes argue otherwise). If you combine the two categories, then accidents account for 105 million DALY’s just slightly less than cardio-vascular diseases.

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Figure 3 shows the same data, but in a different way. For each of the disease groups, it shows the percentage of total cases that can be attributed to the environment. Thus, 57% of all diarrheal diseases can be attributed to environmental causes, the highest fraction. Fifty percent of all unintentional injuries have environmental causes (I think this means that they can be attributed to unsafe conditions that could be remedied, like working in the diamond mines of the Ivory Coast).

Many of the conditions shown in Figures 1 and 2 are disease groups. Looking at specific individual conditions, the report found that fully 76% of fires and burnings could be attributed to environmental conditions, as could 73% of drownings and 57% of diarrheal diseases. The data start to sound almost like public safety or public health issues, as opposed to what we typically think of as “environmental” here in America. And perhaps, in many parts of the world, that is exactly right.

Figure 4. Recommended Actions by Disease Group. Source: Prüss-Ustün et al, 2016.

The authors make recommendations regarding which environmental interventions they thought would be most likely to significantly reduce the burden of environmentally caused disease for each of the 13 disease groups. The recommendations are shown in Figure 4. For those conditions most relevant in the United States (cardio-vascular disease and cancer) it is interesting to see that, along with second-hand smoke, household and ambient air pollution were thought to be important. I’ve discussed the progress Missouri has made in improving its ambient air quality several times, most recently here. We often ignore indoor air quality when we discuss air pollution, however. I don’t know how you would measure it across millions of buildings, but it is a very important environmental issue. If anybody knows about studies of indoor air pollution across Missouri or across the USA, please let me know.

I’ll try to bring all of this home to Missouri a little bit in the next post.

*Disability-Adjusted Life Year (DALY). Disability-adjusted life year is a measure used to estimate the number of years lost to early death, combined with the number of years lost to disability. To determine the number of years lost to death for an individual, subtract the age of death from the normal life expectancy. The result represents the number of years lost to death. For disabilities, subtract the age at which the disability occurred from normal life expectancy, then multiply the result by a “disability factor,” which represents the severity of the disability. The result represents the years lost to disability. Add the years lost to death and the years lost to disability, and you have the disability-adjusted life years (DALYs) for that individual. Do this calculation for every individual in the group, and sum the results across the group, and you have the DALYs for the group.

Sources:

Prüss-Ustün, A., J. Wolf, C. Corvalán, R. Box, and M. Neira. 2016. Preventing Disease Through Health Environments: A Global Assessment of the Burden of Disease from Environmental Risks. WHO Press: Geneva. Downloaded 5/3/2017 online from http://www.who.int/quantifying_ehimpacts/publications/preventing-disease/en.