Desire Tshala-Katumbay1,2,3, Jean-Claude Mwanza4, Diane S. Rohlman5,6, Gladys Maestre7 & Reinaldo B. Oriá8
nature.com/brain-disorders
1Department of Neurology, Oregon Health & Science University, Portland, Oregon, 97239, USA. 2National Institute of Biomedical Research, 1197 Kinshasa I, Congo. 3Department of Neurology, University of Kinshasa, 825 Kinshasa XI, Congo. 4Department of Ophthalmology, University of North Carolina at Chapel Hill, North Carolina 27599, USA. 5Occupational and Environmental Health, The University of Iowa, Iowa 52242, USA. 6Oregon Institute of Occupational Health Sciences, Oregon Health and Science University, Portland, Oregon, 97239, USA. 7G. H. Sergievsky Center, Columbia University Medical Center, New York, New York 10032, USA. 8Department of Morphology and Institute of Biomedicine, Faculty of Medicine, Federal University of Ceara, Fortaleza 60020, Brazil. Correspondence should be addressed to D. T.-K. e-mail: tshalad@ohsu.edu.
Reports from the World Health Organization (WHO) indicate that the global burden of disease is determined by patterns of disease and disability in low- and middle-income countries (LMICs), which, predictably, have their own environmental signatures (http://www.who.int/healthinfo/global_burden_disease/about/en/). However, the effect of such signatures on both brain health and region or global disability-adjusted life years (DALYs) remains unknown and needs to be added to the agenda of global environmental health research. As for high-income countries, environmental health research programmes in LMICs must primarily focus on elucidating the entire range and source of exposures to define the human ‘exposome’ (the measure of all the exposures of an individual in their lifetime and how these exposures relate to health) relevant to brain health in LMICs. The research agenda should also include mechanistic and translational research, as well as capacity building to foster a new generation of environmental health scientists.
SCOPE
In this Review, we focus on environmental risk factors for brain diseases and conditions in LMICs (http://data.worldbank.org/about/country-and-lending-groups). An iterative search of the literature was conducted using PubMed to retrieve information related to environmental determinants and mechanisms of brain disease in LMICs. Additional opinion was obtained from interviews with leading environmental scientists and neuroscientists, as well as programme officers at the US National Institutes of Health and US National Institute of Environmental Health Sciences (NIEHS), and Fogarty International Center. This Review integrates the goals and approaches to environmental health research as per the NIEHS 2012–2017 strategic plan (https://www.niehs.nih.gov/about/strategicplan/).
ENVIRONMENTAL EXPOSURE AND BRAIN HEALTH
LMICs are home to around 80–85% of the world’s population1. Of these 5.8 billion people2, 1 billion remain in extreme poverty, living below the US$1.25 per day poverty line3. Around 3 billion people do not have piped drinking water in their home and 173 million people rely on the direct use of surface water. Without proper sanitation, about one billion continue to defecate in gutters, in the open bush or in open water bodies4. Wildfires and deforestation are commonplace and drought and floods, possibly due to climate change, degrade the existing farming systems and create food insecurity5–7. Armed conflicts and population displacements impose a toll on human life8. Industrial expansion coexists with an unprecedented rise in artisanal mining and unprotected labour9. In some instances, normal urbanization operations, such as road construction and quarantines (for example during Ebola outbreaks in the Democratic Republic of the Congo) have created conditions that exacerbated the risk of environmental exposure and brain disease10. Flawed regulations compounded by a lack of infrastructure set the stage for environmental degradation and pollution to pose serious threats — of a chemical or non-chemical nature — to human health. The degradation of local ecosystems leads to the creation of ‘microenvironments’ that have a high risk of harmful exposures, often resulting in unique challenges and increased risk of human disease.