Neurological effects of ambient air pollution
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Ambient air pollution is a global health problem and it is an important factor associated with morbidity and mortality worldwide. In high-income countries air pollution was associated with 2.5% of all deaths, making it the eighth leading risk factor for mortality(Narayan, Ali et al. 2010). Cardio respiratory effects and mechanisms have been extensively investigated. There is also mounting evidence that exposure to air pollution can cause stroke-related sickness and death. However, little is known regarding neurological effects. Air pollutants are substances in the air that can cause harm to humans and the environment. They arise in different forms like gasses, solid particles and liquid droplets. They are also divided in pollutants from natural sources in the environment, like volcanic activity and forest fires (when started by lightning) and pollutants that are man-made or anthropogenic. The most investigated air pollutants that have an adverse health effect are particulate matter (PM), ground level ozone (O3), black carbon (BC) and nitrogen dioxide (NO2). These pollutants can enter the brain via different pathways, including diffusion trough the lung epithelial and vascular endothelial layers, via the neuronal olfactory nerve and through disrupting the blood brain barrier by inducing oxidative stress and the expression of pro-inflammatory molecules. Several groups have found associations between exposure to ambient air pollutants and neuro-degenerative effects and cognitive function, both in toxicology studies and epidemiology studies. The aim of this review is to give some information about the exposure to ambient air pollutant and the adverse effects on the function of the brain. It will include studies on the effect on development due to prenatal or early childhood exposure as well as studies that investigated the effect of air pollution exposures on the adult cognition function.