Economic transitions in the era of globalization warrant a fresh look at the neurological risks associated with environmental change. These are driven by industrial expansion, transfer and mobility of goods, climate change and population growth. In these contexts, risk of infectious and non-infectious diseases are shared across geographical boundaries. In low- and middle-income countries, the risk of environmentally mediated brain disease is augmented several fold by lack of infrastructure, poor health and safety regulations, and limited measures for environmental protection. Neurological disorders may occur as a result of direct exposure to chemical and/or non-chemical stressors, including but not limited to, ultrafine particulate matters. Individual susceptibilities to exposure-related diseases are modified by genetic, epigenetic and metagenomic factors. The existence of several uniquely exposed populations, including those in the areas surrounding the Niger Delta or north western Amazon oil operations; those working in poorly regulated environments, such as artisanal mining industries; or those, mostly in sub-Saharan Africa, relying on cassava as a staple food, offers invaluable opportunities to advance the current understanding of brain responses to environmental challenges. Increased awareness of the brain disorders that are prevalent in low- and middle-income countries and investments in capacity for further environmental health-related research are positive steps towards improving human health. This article has not been written or reviewed by Nature editors. Nature accepts no responsibility for the accuracy of the information provided.

Endemoepidemic neurodegenerative diseases putatively caused by food toxins have been reported around the globe with no clear understanding of their pathogenetic mechanisms. These diseases include the amyotrophic lateral sclerosis/parkinsonism dementia complex among the Guamanians; neurolathyrism among Europeans, Indians, and populations of the Horn of Africa; and tropical ataxic neuropathy or konzo among sub-Sahara Africans.1,2 We focus on the molecular determinants of susceptibility to konzo, a poorly known self-limited and irreversible upper motor neuron disease (spastic paraparesis) highly prevalent in Congo-Kinshasa, Mozambique, Tanzania, Central African Republic, Angola, and Cameroon. The main clinical picture consists of a symmetrical, permanent, and irreversible spastic paraparesis with no signs of sensory or genitourinary impairments.2,3 Severely affected individuals may present with a tetraparesis and pseudobulbar signs. The disease konzo was named after a fetish used by the “Yaka” population of Congo-Kinshasa. The World Health Organization has adopted the following epidemiologic criteria for the disease: 1) an abrupt onset (<1 week) of weakness in legs and a nonprogressive course of the disease in a formerly healthy person, 2) a symmetrical spastic abnormality when walking and/or running, and 3) bilaterally exaggerated knee and/or ankle jerks without signs of disease of the spine. The authors thank the population of Congo-Kinshasa for their participation in the current research project. The authors are grateful to Dr. Jean-Jacques Kaniki Vundu, Kahemba District Health Officer, DRC, and Ali Rosine, Institut National de Recherches Biomédicales, Kinshasa, DRC, for their technical support. The following contributors have significantly participated in the design and implementation of the research program: M. Bumoko, MD (Department of Neurology, University of Kinshasa, Congo-Kinshasa); S. Sombo, MD (Department of Neurology, University of Kinshasa, Congo-Kinshasa); K. Kambale, BSc (Department of Basic Sciences, University of Kinshasa, Congo-Kinshasa); N. Masukano, MD (Ministry of Health, Congo-Kinshasa); S. Ngeleza, MD, MPH (School of Public Health, University of Kinshasa, Congo-Kinshasa); K. Kashama, MD (Department of Neurology, University of Kinshasa, Congo-Kinshasa); P. Büscher, PhD (Tropical Institute of Medicine, Antwerp, Belgium); M. Mashako, MD, PhD (Ministry of Higher Education, Congo-Kinshasa); S. Westaway, PhD (Department of Neurology, Oregon Health & Science University, Portland, OR); and L. David, PhD (Proteomic Core, Oregon Health & Science University, Portland, OR). IRB approval was obtained from Oregon Health & Science University, Michigan State University, and the Government of Congo-Kinshasa.