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The affact of pollution on the brain

“Erythrocyte omega-3 index, ambient fine particle exposure and brain aging” by Cheng Chen, Pengcheng Xun, Joel D. Kaufman, Kathleen M. Hayden, Mark A. Espeland, Eric A. Whitsel, Marc L. Serre, William Vizuete, Tonya Orchard, William S. Harris, Xinhui Wang, Helena C. Chui, Jiu-Chiuan Chen, Ka He. Neurology. The problem of pollution is reaching crisis dimensions in most cities across the globe. Windham et al. (1435) indicate that scientists attribute the sharp increase in pollution levels to growing industrialization, rapid economic development, increasing traffic, and higher energy consumption levels. While many industrialized countries have made progress in controlling pollution over the last thirty years, air quality, especially in large cities in the developing world, worsen. Henn et al. (1) estimated that 9 out of 10 people worldwide breathe polluted air every day. Conversely, over 7 million people die every year due to pollution-related complications (Windham et al. 1445). Medical experts have associated pollution with cardiovascular morbidity and mortality (Paula et al. 351). However, the theory that air pollution harms the brain is gaining traction in the research community. Epidemiological studies conducted in recent years have shown that heavy metal pollution and air pollution disrupts normal brain development, leading to neurological disorders such as autism spectrum disorder, Alzheimer’s disease, neurodevelopment disorders, and Parkinson’s disease. Association between Pollution and the Brain Increased exposure to pollutants and toxic substances has long been suspected of causing brain damage from children’s developing brains to the mature adult brain (Paula et al. (353). A vast array of pollutants have been identified that can be classified broadly as metals and organic chemicals. Examples of organic chemicals that pollute the environment include carbon monoxide, nitrogen oxides, sulfur dioxide, greenhouse gases, particulate matter, and volatile organic compounds. Conversely, notable metals classified as toxic pollutants include manganese, lead, mercury, arsenic, and aluminum. Increased industrialization and motor vehicles have resulted in increased emission of both heavy metals and organic chemicals to the environment. Over 90 percent of the world’s population is currently exposed to at least one of these pollutants. 	Accordingly, epidemiological studies have ascertained that most of these pollutants cause toxicity in the brain. Paula et al. (353) are among the scholars who have attempted to examine the association between metals and the brain. The study focused mainly on empirical analysis of lead and manganese’s effect on nerve cells and neurobehavioral functioning. First, the authors acknowledged that over 50 million people are exposed to lead (Paula et al. 354). In the United States, over 300 children are exposed to lead every year. Lead pollution mainly comes from ore processing plants and piston-engine aircraft operating on leaded fuel. Some vehicles using leaded fuel also emit toxic lead gases into the atmosphere. Other notable sources include utilities, waste incinerators, and lead-acid battery manufacturers. Conversely, major sources of toxic manganese include emissions from iron production, mining and mineral processing, sewage sludge, and wastewater discharge. Emissions from the combustion of fossil fuels and fuel additives are also known to release manganese, which pollutes the air. Data obtained by Henn et al. (126) showed that manganese and lead are toxic to the brain. Prolonged exposure to high concentrations of manganese will result in neurological and neurobehavioral effects (Henn et al. 126). They associated long-term exposure to manganese with fumes’ inhalation in occupational settings (Henn et al. 126). Therefore, most people suffering from manganese toxicity are more likely to have inhaled it from work. However, increasing cases of people drinking water contaminated with manganese have also increased in the past few years. Accordingly, the study showed that lead exposure during childhood results in a durable loss of 6 to 7 points on IQ testing. Lead exposure also shortens attention span in children between 1 and 5 years old. Mullin et al. (1009) also examined the relationship between environmental pollutants and brain changes, focusing on manganese. However, the researchers used mice as the subjects in their study. Succinctly, the study was a randomized controlled trial, whereby a sample of 10 mice was exposed to manganese through oral admission of contaminated water for 21 days. Each mouse consumed 22 mg/kg per day for 21 days (Mullin et al. (1020). The rats in the control group were given pure water for 21 days. Accordingly, the study showed that oral manganese exposure induced a significant increase in the acoustic startle reflex’s amplitude. They also reported a significant increase in striatal DA and 3, 4-dihydroxyphenylacetic acid concentrations (Mullin et al., 1021). These changes were not reported in rats in the control group. In a similar study cited by the authors, neonatal rats exposed to manganese suffered neuronal degeneration and increased brain monoamine oxidase. 	These changes were recorded on day 15 and day 30 of the study. Each rat was exposed to 0.31 mg Mn/kg per day in water for 60 days (Mullin et al., 1023). Similar studies conducted on humans have also yielded comparable results. Therefore, with the increasing processing of iron production and mineral processing, the problem of overexposure to manganese and other toxic metal fumes is expected to increase significantly. More people will suffer from brain damage because of overexposure to these metals in occupational settings. Other studies, however, have focused on the study of general air pollution on the central nervous system. These studies mainly acknowledge that air pollution contains toxic organic chemicals such as sulfur dioxide, nitrous oxides, and carbon monoxide, among other gases, which are highly toxic when released to the environment. For example, in their study of air pollution’s effect on the central nervous system, Power et al. (235) found out that air pollution affects various parts of the brain. The parts affected by air pollution include the cerebral white matter, basal ganglia, and cortical gray matter. Equally, in a population-based sample using magnetic resonance imaging (MRI) to study findings of cerebral white matter lesions and infarcts, Power et al. (237) showed that exposure to traffic-related air pollution is associated with a significant prevalence of vascular brain findings. On the other hand, Costa (1) investigated how polluted air could be bad for the brain. She acknowledges in her study that many toxins currently being released in the environment harm the brain. However, the research community has only gained an interest in studying the possibility of air pollution as a culprit in brain damage in recent years (Costa 3). Accordingly, Costa (3) mentioned that she was inspired by the growing body of literature in this area inspired him to begin her research. Correspondingly, in her study, she focused on assessing the effects of Mexico City air on mice (Costa 5). She observed that Mexico City residents, especially those living in southwestern Mexico City, are overexposed to heavy-duty diesel engine emissions (Costa 5). Therefore, she collected the air from the region, exposing a sample of mice to it. The mice used in the study showed autism-like social and behavioral issues (Costa 23). After their exposure to diesel exhaust during early postnatal life, the mice demonstrated lower reelin levels. Reelin is a protein highly essential for brain development. A similar mechanism leads to autism in humans. To this extent, Costa (7) concluded that air pollution might harm memory, behavior, and attention. On the contrary, Rylander and Vesterlund (1) studied the effect of carbon monoxide intoxication on the fetus. The study utilized the case study design, with Rylander and Vesterlund (1) examining the autopsy findings in nine fetal CO poisoning cases. Postmortem examination of the fetuses revealed severe damage to the grey matter. One of the notable cases the authors studied included a 23-year-old woman in her pregnancy’s 24th week. The woman suffered a gas accident, which left her unconscious for over 3100 hours (Rylander and Vesterlund 10). The woman abruptly gave birth to the child after six weeks. The child breathed spontaneously, dying 2 hours later. The results of the postmodern examination showed severe damage to the gray matter. The damage was particularly seen in the brain stem’s nuclei, the cerebral cortex’s necroses, the tegmental nuclei, the pontine peduncular, and the midbrain nuclei (Rylander and Vesterlund 9). Like most studies analyzed above, Rylander and Vesterlund (13) concluded that environmental pollutions have damaging effects on the brain. As such, most of these studies recommend that policymakers introduce legislation that reduces the toxic pollutants that affect the brain. Association between Pollution and Neurological Disorders Most studies investigating the association between pollution and the brain have also linked pollution with some brain diseases. Studies agree that individuals living in high-pollution areas during childhood and adolescence experience an increased risk of brain damage. Cases of people suffering from diminished mental capacity have also been reported in most of the studies conducted in the past few years. Some of the notable brain diseases associated with pollution include autism spectrum disorder, Alzheimer’s disease, neurodevelopment disorders, and Parkinson’s disease. Autism Spectrum Disorder Several studies, using various methods for estimating exposure, have reported links between air pollution and the risk of autism. Windham et al.’s (2006) study on the relationship between autism spectrum disorder and increased exposure to hazardous air pollutants is one of the recently published studies showing a significant link between air pollution and the risk of autism. Windham et al. (2006) conducted their study in the San Francisco bay area, California, using a sample of 284 children with autism and 657 controls. The researchers used census track-based estimates derived by the Environmental Protection Agency (EPA) for 19 hazardous air pollutant chemicals (Windham et al. 2016). Compared to children in the lowest two quartiles, children in the top quartile of exposure to heavy metals and chlorinated solvents had a 50 percent chance of developing autism. Some of the compounds that Windham et al. (1438) associated with autism included vinyl chloride and trichloroethylene. They also associated heavy metals such as mercury, nickel, and cadmium with autism in children (1439). In tandem with this, they reported that diesel particulate matter increased the risk of developing autism. Nonetheless, Windham et al. (1439) specified that they based the exposures in their study on modeled estimates of HAPs in census tracts of birth residence that pertained to those locations two years after the birth (Windham et al. 1440). For this reason, the study did not capture prenatal exposure. Equally, studies conducted in West Virginia and North Carolina have reported a significant link between air pollutants and elevated risk of autism. Notable pollutants identified in these studies include mercury, diesel, beryllium, styrene, and nickel. These studies agree that proximity to major freeways during gestation increases the risk of autism. To this extent, Windham et al. (1440) recommended that pregnant women should avoid settling near major freeways, as they are likely to be exposed to air pollutants that would affect their children’s brain development. Accelerated Neural Aging Some studies have associated exposure to several toxic pollutants with neurodegenerative diseases such as Amyotrophic lateral sclerosis (ALS), Parkinson’s disease, Alzheimer’s disease, and multiple sclerosis. Power et al. (235) demonstrate that individuals exposed to heavy metal pollutants will display signs of these diseases at an earlier age. Power et al. (235) also conducted a systematic review of existing studies to find the link between various pollutants with neurodegenerative disease. Most of the studies reviewed showed a consistent positive link between exposures to at least one pollutant and Alzheimer’s disease (Power et al., 235). The disease causes a loss of memory and odd behavior in some older people. Aluminum is one of the notable heavy metal pollutants linked with Alzheimer’s disease. The study showed that people living or working in regions where aluminum fumes are abundant in the air. The study also showed that people living in areas with high particulate matter levels in the air are at risk of developing multiple sclerosis. Multiple sclerosis is a chronic, inflammatory demyelinating that emerges when chronic inflammation compromises oligodendrocytes. The myelin sheath is easily destroyed when oligodendrocytes are destroyed. As Power et al. (239) show, pollutants such as lead will facilitate the destruction of the myelin sheath because they compromise the oligodendrocytes. Once the myelin sheath has been destroyed, signs of multiple sclerosis begin to manifest. Conversely, Parkinson’s disease emerges when the brain experiences a shortage of dopamine (Henn et al., 126). As dopamine levels drop with advancing Parkinson’s disease, levels of the neurotransmitter glutamate rise. Glutamate over-stimulates certain receptors, causing premature death. Henn et al. (126) showed that heavy metal pollutants such as manganese cause dopamine deficiencies. As such, people exposed to manganese are at risk of developing Parkinson’s disease at an early age (Henn et al. 126). Besides, manganese is associated with increasing glutamate levels, which, as highlighted in the previous section, is associated with premature death in people with Parkinson’s disease. To this extent, pollutant results in the early onset of Parkinson’s disease and lead to premature death in people who have developed the disease. Conclusion Epidemiological studies conducted in recent years have shown that heavy metal pollution and air pollution have adverse effects on brain development. In brief, pollutants disrupt normal brain development, leading to neurological disorders such as autism spectrum disorder, Alzheimer’s disease, neurodevelopment disorders, and Parkinson’s disease. Exposure to heavy metal and air pollutants is becoming a persistent problem. Therefore, policymakers should introduce legislation that focuses on minimizing these pollutants to help prevent their effects on the brain. Reference: