<p>There are about 10 million new cases of cognitive impairment diseases&#xa0;yearly, affecting 50 million people worldwide. Cognitive impairment is partly explained by pollutant exposure, with air pollution as one of the risk factor for dementia. Here we review the relationships between cognitive impairment and pollutant exposure, with focus on pollutant types, the entry of pollutants into the brain, symptoms and therapeutical drugs. Pollutants comprise solid and particulate compounds, organic and inorganic pollutants, bacteria, biotoxins and viruses. Symptoms include oxidative stress, neuroinflammation, aberrant cell death, and effects on the gut-brain axis. Cognitive impairment could be cured and prevented with antioxidants, anti-inflammatory compounds, inhibitors and activators, probiotics, and a healthy lifestyle. We present epidemiological evidence linking pollutants to cognitive impairment, and underlying neurotoxicity mechanisms. The olfactory mucosa and olfactory bulb pathway appears as the major route for pollutants entry into the brain parenchyma, which explains the strong epidemiological link between airborne pollutants and cognitive impairment. Oxidative stress and neuroinflammation trigger aberrant programmed cell death, including autophagy, apoptosis, and ferroptosis.</p>