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Some of the environmental factors of risk to health such as unsafe drinking-water, insufficient sanitation, indoor air pollution, as well as infectious and non communicable disease are well known; others less so, such as climate change or the built environment.
The realization of just how much disease and ill health can be prevented by focusing on environmental risk factors should add a significant impetus to global efforts to encourage adapted preventive health measures through all available policies, strategies, interventions, technologies and knowledge.
Estimating the burden of disease that can be reduced by taking measures to decrease environmental risks to health is a key step in identifying and evaluating the most important priorities for targeted environmental action.
In 2012, the number of deaths attributable to the environment was estimated to be 12.6 million deaths per year. Such estimate supports the idea that sound environmental management can play a crucial role in protecting people’s health. The report’s findings result from a systematic process:
Experts were asked to provide a best estimate of the fraction of disease in the global population attributable to the reasonably modifiable environment.
This report presents the latest wide-ranging evidence on environment-disease links and their devastating impact on global health, and it detailed findings and assessment to show how improving the environment can promote health and well-being.
It provides a meta-synthesis of key evidence relating diseases and injuries to the environment, and approximates quantitative estimates of how much disease can be prevented by reducing the environmental risks1 to health. To this end, it uses a combination of approaches that includes comparative risk assessment (CRA), epidemiological data, illness transmission pathways, and expert opinion. More than 100 diseases and injuries are covered.
The report analyses and quantifies how different diseases are impacted by environmental risks, detailing the causes, the regions and most vulnerable populations, and highlights promising areas for immediate intervention and gaps where further research is needed to quantify the burden of disease for various environmental risk factors.
The realization of just how much disease and ill health can be prevented by focusing on environmental risk factors – with the evidence of what is achievable and needed – should add impetus to global efforts to encourage preventive health measures through all available policies, strategies, interventions, technologies and knowledge.
1 Environmental risks to health are defined in this study, as “all the physical, chemical and biological factors external to a person, and all related behaviours, but excluding those natural environments that cannot reasonably be modified.”
The health impacts due to the environment showed a slight improvement over the 10 years – between 2002 and 2012, the number of deaths attributable to the environment decreased from 13.3 to 12.6 million deaths per year, alongside a decrease in total deaths from 57.0 to 55.6 million deaths globally. The fraction of deaths attributable to the environment also slightly decreased, from 23.3% to 22.7% over the same period but up to 26% of all deaths in children under five years.
There was a significant reduction in environment-attributable deaths and disease burden in the communicable, infectious, parasitic, neonatal and nutritional categories. That same period saw an increase in attributable deaths and disease burden in the Non Communicable Diseases (NCD) category.
Total environmental deaths are unchanged since 2002, but show a strong shift to non communicable diseases mainly due to a global decline of infectious disease rates, and a reduction in the environmental risks causing infectious diseases. The main disease burden that could be prevented through healthier environments are stroke, ischaemic heart disease, diarrhoea and cancers. This environmentally-mediated disease burden is much higher in lower income countries, with the exception of certain non communicable diseases such as cardiovascular diseases and cancers, where the per capita disease burden is greater in the developed world. In children under age five, communicable diseases and injuries have the greatest preventive potential through environmental action. Certain exposure-disease links saw significant revisions in 2012 such as injuries from fire and hot substances. Globally however, the modifications were relatively limited in terms of the total disease burden.
Crucially, the report shows that many measures can be taken immediately to reduce the disease burden attributable to environmental determinants. Indeed, the report strongly supports the notion that the environment is a sound platform for good public, community and individual health. Examples include the promotion of safer household water storage and better hygiene measures, the use of cleaner fuels, safer and more judicious use and management of toxic substances at home and in the workplace, and occupational safety and health measures.
Actions need to come from all the sectors who make decisions that impact on environmental determinants of health. Actions by sectors such as energy, transport, agriculture and industry are vital, in cooperation with the health sector, to address the root environmental causes of ill health. To address the environmental causes of disease and injury the health sector should thus be repositioned to work more inter sectorally on coordinated health, environment and development policies, that can strengthen and sustain improvements to human well-being and quality of life via multiple social and economic co-benefits.
Finally, the direct and indirect impacts of emerging risks, such as climate change and ecosystem change, need to be tackled urgently, as they are set to become the most challenging risks populations will face in the coming decades.
There are some modifiable key elements for which quantitative links are now better evidenced to account for a large fraction of the global burden of diseases related to environmental risk factors.
It should be noted that many of the potential health implications of climate change, acting through food supply and migration, could unfortunately not be accounted for by the methods used in the report.
Eight main categories were considered:
The most important environmental risk factor is exposure to smoke from cookstoves, which was responsible for 33% of the disease burden of lower respiratory infections (in « disability-adjusted life year » or DALYs) in 2012. Among infections, lower respiratory infections include pneumonia, bronchitis and bronchiolitis, caused 935 000 deaths per year (in 2013). These infections are the most important cause of mortality in children, accounting for 18% of deaths in children under five. The fraction of upper respiratory infections and otitis attributable to environmental risks (including passive smoking) was estimated at 24% in low and middle-income countries, and 12% in high-income countries. Infectious diseases are also a major cause of deaths and diseases and these are detailed in the report.
Diarrhoeal diseases are one of the main contributors to global child mortality, (20% of all deaths in children under five years) with a large proportion caused by faecal-oral pathogens. The predominant route of transmission depends on the pathogen, local infrastructure (access to appropriate sanitation and safe water) and human behaviour. Among other infectious agents, dengue fever is the most rapidly spreading mosquito-borne viral disease in the world. There is considerable underreporting and misclassification in the surveillance of dengue cases. One recent estimate indicates 390 million dengue infections per year. It has been shown that the extension of piped drinking-water to rural communities (which lead households to increase water storage in containers for longer periods of time) without due attention to the reliability of services has been conducive to the spread of dengue transmission from urban to rural zones.
For asthma, total environmental exposures were estimated to account for 44% and the estimate for environmental exposures did not include outdoor exposure to pollen, as this is not realistically modifiable. Unintentional poisonings considered in the report (estimated to cause 193 000 deaths annually) include poisonings by chemicals or other noxious substances, including drugs, and toxic vapours and gases. The attribution of unintentional poisonings to occupational exposure to toxic chemicals was estimated to amount to 14%. It was estimated that 68% (50–87%) of poisonings in adults were attributable to occupation or the environment, and 85% (60–99%) in children. Despite safety measures, some poisonings from accidental drug overuse or negligence will still occur, even when chemical safety measures are implemented and adequate information/education provided and these poisonings were not considered related to occupation or environment.
A series of factors, not directly considered as « environmental factors » in the sense given in this report were not considered:
Similarly, social determinants such as lack of piped water, damp housing, and sanitation coverage have not been included, even if some social determinants of health are closely linked to and if they mediate exposure to environmental risk factors. These social determinants are functions of the circumstances in which people live, work and grow; largely shaped by the distribution of resources and power.
The report also identified and summarized the main links between diseases and injuries and the environment, as well as potential areas for intervention from various categories of diseases: infectious and parasitic diseases, neonatal and nutritional conditions, non communicable diseases, risk factors for non communicable diseases in other areas but related to the environment, unintentional injuries (such as road traffic accidents, unintentional poisonings) or Intentional injuries.
Environment-health interventions are based exactly on the SDGs principles and, as evidenced in this report, can make a significant contribution towards achieving the SDGs and improving life and health for all at all ages.
Indeed, within the 17 Sustainable Development Goals (SDGs), agreed by heads of state at the UN General Assembly in September 2015, there are clear health-related targets, but these sit alongside environmental and other sectoral areas that strongly influence determinants of health. Critically, the 169 targets are geared towards establishing relevant and effective links that can bring about the transformational change required, without leaving anyone behind.
A change in perception to view the environment as an essential element of health protection, while adequately preserving it, would greatly benefit people’s health. The determinants of diseases linked to the environment often lie within the sphere of action of sectors other than health or environment. The environment should be viewed as a key element for health protection and reduction of health inequalities, and placed at the centre of primary prevention. Reducing the environmental burden of death and disease is entirely possible through cost-effective interventions. Creating and maintaining healthy environments should thus be a priority of primary prevention and reinforce the public health principle. As social determinants are closely linked to, and mediate exposure to environmental risk factors, they need to be systematically integrated into risk monitoring and policy planning in order to reduce health inequalities.
However, to be most effective and sustainable these measures need to be designed and implemented holistically and action is needed at all levels of governance, as local action can be a key determinant in shaping the local use of resources and management of health determinants. Through their local scope and democratic nature, municipalities are natural leaders of local environment and health planning. The Sustainable Development Goals, offer here opportunities to make a lasting contribution.
Coordinating and acting across sectors will be necessary, as many different sectors play a crucial role (e.g. energy, industry/manufacturing, water and sanitation, agriculture, housing, transport) in determining environmental risks and conditions. It is estimated, for example, that 42% of the global malaria burden could be prevented by environmental management, although the fraction amenable to environmental management varies by region.
More specifically, attention should be drawn to:
The report underlines that a large part of this analysis is based on surveys of expert opinion and, like many such analyses, the uncertainties of such estimates are relatively large. Also, the overall impact of some sectors, such as energy or transport) have not been taken into account and this, too, may lead to an underestimate of the global health burden attributable to modifiable environmental factors.
The data and methods underlying the health statistics for the previous and current editions have undergone major modifications. The best available scientific evidence together with approximations and expert evaluations for knowledge gaps were combined to provide up-to date estimates. Nevertheless expert opinion generally reflects the evidence in the literature, which may not be homogeneous, can be region-specific, or incomplete.
Out of 133 diseases or injuries or their groupings considered, 101 had significant links with the environment, 92 of which have been quantified, at least partially. To calculate the fraction of disease attributable to a risk factor for any defined population, compiled or estimated population attributable fractions were multiplied by the corresponding WHO disease statistics by disease or injury, country, sex and age group, for deaths and disability-adjusted life year (DALYs).
For 2012, the effect of water and sanitation was only estimated for low- and middle-income countries, and only the effects of main risk factors were taken into account. Also, fewer infectious diseases were included in the 2012 estimation of the consequences of malnutrition (they did not re-evaluate the diseases linked to malnutrition but only the link between environment and malnutrition).
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