Anyone living in a big city that has taken a vacation to experience nature (e.g. a cabin in the woods) can often detect a stark contrast in air quality. In the big city, the air you’re breathing in often smells dull and polluted, and you may sense that it’s taking a toll on your health. In a naturalistic setting, the air you’re breathing in smells vibrant, stimulating the olfactory system in ways that the big city air never would, and reinvigorates your sense of wellbeing.
Many people can sense that their brain performs better when they’re breathing in clean oxygen from nature. Living in large cities with significant air pollution (e.g. New Delhi, Beijing, Lima) not only can increase your chances of developing lung cancer, but it can simultaneously damage your brain. Unfortunately, many people living in big cities often become desensitized to the air that they’re breathing in and/or never experience naturalistic contrast of high quality air.
After several years (or even months) of living in an environment with polluted air, the pollutants act as neurotoxins, damaging the brain and killing brain cells. This results in rapid cognitive decline, foggy thinking, and a sense that something is cognitively amiss. To avoid unintentionally damaging your brain with pollutants, it is best to be aware of the risks associated with inadvertent insufflation of these neurotoxins.
How Air Pollution Damages the Brain
There are a variety of ways in which air pollution inflicts damage on the brain. Air pollution is known to reduce volumetric measures of white matter, permanently impair cognitive development in children, and increase likelihood of neurodegenerative diseases like dementia. Moreover, many victims of air pollution ironically experience significant “brain fog” and have sensory processing deficits in smell, hearing and balance.
- Accelerated brain aging: Exposure to 2 mcg (micrograms) per cubic meter of fine-particulate matter is associated with a 0.32% reduction of brain volume. While this may not seem substantial, experts suggest that this amount is an approximate equivalent to one additional year of brain aging. Individuals exposed to 4 mcg per cubic meter of fine-particulate matter therefore would experience 2 years of accelerated brain aging.
- Behavioral changes: Some people experience significant behavioral changes as a result of exposure to air pollution. Behavior change may not be apparent overnight and tends to occur gradually with consistent exposure to pollutants. Individuals exposed to air pollution may act more impulsive, and have a difficult time correcting detrimental behaviors.
- Blood-brain barrier breakdown: The blood-brain barrier helps protect your brain from pathogens and limits entry of potential toxins. However, consistent exposure to air pollution causes the blood-brain barrier to gradually deteriorate. Deterioration of the blood-brain barrier can result in compromised immune function, poor information processing, and abnormal neuronal functioning. Breakdown of the blood-brain barrier is a sign of an aging brain and indicative of cognitive impairment.
- Brain volume loss: Studies have confirmed that exposure to air pollution results in losses of brain volume. The loss of brain volume experienced from exposure to an average amount of fine-particulate matter in a large city is roughly equivalent to an additional year of brain aging. It appears as though air pollution contributes to substantial losses in white matter, which serves as an insulator and transmits signals between various parts of the brain.
- Cognitive impairment: Regardless of age, regular exposure to ambient air pollution is known to cause working memory deficits and poorer cognitive performance. Cognitive impairment from air pollution is likely most notable among children without fully developed brains. That said, even among adults, exposure to pollutants can affect memory and attention.
- Developmental impairments: Another significant consequence associated with air pollution exposure is suboptimal neurocognitive development. The brains of children are highly sensitive to environmental inputs and are constantly being molded via synaptogenesis. Significant exposure to air pollution impairs brain development and literally may be rewiring the brain to become dumber.
- Intelligence (IQ) reduction: Certain studies assessed performance on IQ tests among individuals living in areas with high air pollution and compared the results to individuals from areas with low air pollution. After controlling for a variety of potential confounding factors, researchers determined that those living in areas with low air pollution had increased IQ scores. This is likely due to the fact that air pollution decreases brain volume and executive task performance.
- Mood disorders: There are a variety of factors that can contribute to mood disorders, one of which happens to be air pollution. Exposure to particulate matter is known to reduce brain volume and impair connectivity of various regions. Moreover, many mood disorders are associated with specific regional and structural deficits – both of which could be caused by air pollution.
- Neurodegeneration: Research has proven that exposure to air pollution increases biomarkers associated with Alzheimer’s and Parkinson’s disease such as: hyperphosphorylated tau protein, amyloid plaques, and α-Synuclein misfolding. Some speculate that risk significantly increases for developing a neurodegenerative disease when exposed to air pollution. In addition, it appears as though individuals with certain genes (e.g. the E4 allele of APOE) exposed to air pollution may experience more substantial and rapid neurodegeneration.
- Neuroinflammation: Air pollution is associated with significant increases in brain inflammation. Inflammation of the brain is associated with a variety of neurophysiological deficits including, cognitive decline, mood disorders, and neurodegeneration. It is thought that neuroinflammation contributes to the severity of a variety of neurological disorders. By minimizing exposure to air pollution, your chances of neuroinflammation are decreased.
- Oxidative stress: Those living in areas with high amounts of air pollution tend to have greater levels of oxidative stress within the brain. This means that various reactive oxygen species accumulate as a result of exposure to pollutants (e.g. fine-particulate matter) and wreak havoc on your brain. Reactive oxygen species can contribute to neurodegeneration, cognitive impairment, stroke, and other pathologies.
- Sensory processing deficits: The ability to process smell, sounds, and maintain balance may be compromised with increased exposure to air pollution. Evidence suggests that children living in urban environments with high exposure to polluted air tend to have significant deficits in olfactory, auditory, and vestibular functioning compared to children living in areas without substantial air pollution.
- Stroke risk: There is an increased risk of silent strokes upon exposure to air pollution among the elderly. Assessments suggest that 2 micrograms (mcg) of fine-particulate matter pollution is associated with nearly a 50% increase in the likelihood of a silent-stroke. Silent strokes refer to strokes that appear on brain scans, but don’t have any overt symptoms.
Common Types of Air Pollution
Below is a list of some common types of air pollution. While outdoor air pollution is common in large cities, many people fail to consider that the inside of their homes and/or apartments are filled with indoor air pollutants. Both indoor and outdoor air pollution can compromise your physical health and damage your brain.
Outdoor Air Pollution
The EPA (Environmental Protection Agency) is required to set National Ambient Air Quality Standards for six of the most common air pollutants. These pollutants include: particulate matter, ozone (ground-level), carbon monoxide, sulfur oxides, nitrogen oxides, and lead. Despite efforts to maintain clean air, many people are still exposed to significant pollution, ultimately impairing their brain function.
- Particle Pollution: Particulate matter is considered a medley of tiny particles and drops of liquid. It consists of various acids (e.g. nitrates, sulfates, etc.), metals, dust particles, and other organic chemicals. Particulate matter under the size of 10 micrometers can easily travel through the throat and damage the lungs, and possibly the heart. Sources of particle pollution include: industries, power plants, and motor vehicles.
- Ozone (Ground-Level): Ground-level ozone is considered a potent air pollutant in that it is created by chemical reactions between nitrogen and volatile organic compounds under sunlight. Examples of things that can contribute to ground-level ozone include: manufacturing facility emissions, motor vehicle exhaust, chemical solvents, gasoline vapor, etc. Inhalation of ozone is associated with lung disease and asthma.
- Carbon monoxide: This is an odorless, colorless gas that is derived from combustion. In large cities, carbon monoxide pollution is more common. High levels of carbon monoxide can be fatal, but moderate levels will reduce oxygen to both your brain and heart, leading to physical and mental decline. The brain needs sufficient oxygen to operate at its best, but when exposed to carbon monoxide, it becomes incapacitated.
- Sulfur oxides: These are considered gasses that are commonly produced at power plants and industrial plants. Other sources of sulfur oxides include: metal extractions, trains using sulfur-based fuels, ships, and other equipment. Sulfur oxides can damage respiratory functions and elicit a variety of detrimental effects on the brain.
- Nitrogen oxides: These are considered reactive gasses that accumulate as a result of motor vehicle (bus, car, truck, etc.) emissions. Nitrogen oxides also form from power plants and usage of industrial equipment. It should be noted that nitrogen oxides facilitate the formation of ground-level ozone and particulate matter pollutants.
- Lead: This is a metal that is present naturally within the environment, but is also found within many manufactured products. In the past when gasoline contained “lead,” there was significantly more toxic exposure than these days. Lead was removed from gasoline, which is why you now see that all gasoline is sold as “unleaded.” That said, there is still lead in the air as a result of lead smelters and airplanes using lead gasoline.
Indoor Air Pollution
Most people are familiar with outdoor air pollution, but indoor air pollution is often ignored. In fact, many people don’t even consider the fact that the inside of their home and/or apartment could be polluted. What’s more unsettling is that most individuals are absolutely clueless that their aerosol sprays (e.g. hair spray), colognes / perfumes, candles, etc. – are a source of pollution.
Those scented “plug ins” that are supposed to serve as air fresheners often are a source of toxins. Those tiny little “clip on” scents that people place upon the air ventilation system within their cars are likely another source of neurotoxins. Something as simple as living in an apartment with poor air flow can cause particulate matter to accumulate, and ultimately impact your brain.
Pollution can come from second-hand smoke, burning of wood, a fresh coat of paint, adhesives, and more. Other common sources of indoor air pollution include: accumulation of radon gas (from the surface of the Earth), insulation (and other construction-related particles), as well as mold. Many people severely underestimate the implications of certain products (e.g. aerosol) on the short-term and long-term health of their brain.
Air Pollution Causes Brain Damage (Scientific Research)
Research suggests that living in cities with significant air pollution can have many deleterious effects, both acute and long-term. It should be emphasized that children and adolescents are at greatest risk of potentially life-altering neurological disorders associated with air pollution due to the fact that their brains’ aren’t fully developed. That said, regardless of whether you’re a child or an adult, living in constant pollution (indoor or outdoor) can promote permanent cognitive decline and other central nervous system (CNS) impairments.
2015: A report published in 2015 suggested that inhalation of particulate matter has significant detrimental effects on the brain. Particulate matter that is considered ultrafine is small enough to make its way to the brain, and ultimately contribute to numerous neurological pathologies including: depression, stroke, neuroinflammation, oxidative stress, and neurodegeneration. Specifically, it was mentioned ambient air pollution can increase: hyperphosphorylated tau protein, amyloid plaques, and facilitate α-Synuclein misfolding.
Among animal models, exposure to particulate matter prompts a neurodegenerative and neuroinflammatory response. The combination of increased inflammation and reduction in brain volume results in many cognitive, behavioral, and functional deficits. Authors of this report suggest that air pollution can damage a person’s CNS (central nervous system) and permanently decrease quality of life.
- Source: http://www.ncbi.nlm.nih.gov/pubmed/25256239
2015: Another study from 2015 notes that air pollution likely acts as a neurotoxin, damaging the brain. This study analyzed a total of 2,715 children (between the ages of 7 and 10) from 39 schools located in Barcelona. All of these children were exposed to either high or low air pollution, and their cognitive development was tested (4 times each) with a computer-based assessment.
Researchers measured air pollution resulting from motor vehicle traffic including: particulate matter, nitrogen dioxide, and elemental carbon – both inside and outside the classroom. Cognitive function was tested with the “N-back” and other working memory tests. After adjusting for a variety of factors (age, sex, socioeconomic status, etc.), researchers determined that children in schools with higher pollution experienced poorer cognitive development than those in less polluted environments.
- Source: http://www.ncbi.nlm.nih.gov/pubmed/25734425
2015: A study published in 2015 documented that children exposed to urban air pollutants experience neuroinflammation and biomarkers associated with neurodegenerative diseases (e.g. Alzheimer’s). This study investigated how the APOE (apolipoprotein E) E4 allele influences brain development among children compared to the E3 allele. Specifically, researchers wanted to determine whether the allele differences altered brain development among those exposed to air pollution in Mexico City.
Results indicated that children with the E4 allele of APOE may be at increased risk of developing a Alzheimer’s disease if they are exposed to air pollution. This was evidenced by differences in white matter, attentional deficits, memory impairment, and poor scores on a verbal IQ test. This suggests that if you have certain genetics associated with neurodegenerative diseases, air pollution may act synergistically with these genes to increase your risk.
- Source: http://www.ncbi.nlm.nih.gov/pubmed/25633678
2015: Authors from a 2015 study suggested that “green space” is associated with superior physical and mental health. Increased exposure to “green space” is thought to improve cognitive function among children. Researchers conducted a study to determine whether exposure to green space has any significant impact on cognitive development of over 2,500 school children (aged 7 to 10) in Barcelona.
Measures of cognitive development were recorded at 3 month intervals for a period of 12 months. These measures included tests of working memory and attention. Green space was calculated based on satellite data. Results indicated that the children with the greatest “green space” had greater cognitive development compared to other children, in part due to the fact that the green space decreased air pollution.
- Source: http://www.pnas.org/content/112/26/7937.abstract
2015: A study from 2015 recruited 789 elderly women to determine whether APOE alleles influence cognitive function following exposure to air pollution. Researchers measured levels of particulate matter and nitrogen oxides and collected data on traffic-induced air pollution. Cognitive function was tested with the CERAD-Plus test to gauge the impact of air pollution and the APOE alleles.
Greater exposure to air pollution was associated with impaired cognitive function and performance. Among individuals with the E4 allele of APOE, it was documented that air pollution from traffic exposure had the most significant impact on cognitive function among elderly women.
- Source: http://www.ncbi.nlm.nih.gov/pubmed/26092807
2015: Researchers reported that millions of children in Mexico City often experience heightened levels of neuroinflammation, oxidative stress, and breakdown of the blood-brain barrier as a result of air pollutants. To better understand the effects of air pollution, researchers recruited 139 children and assessed various biomarkers. The goal was to determine differences between those exposed to low pollution versus high pollution.
Results indicated that high levels of air pollution can contribute to neuroinflammation and increases in biomarkers associated with neurodegenerative diseases like Alzheimer’s and Parkinson’s. Since air pollution can damage the blood-brain barrier, it is thought to detrimentally alter interactions between the brain and immune system. Authors of this research document the increasing importance of investigating air pollution’s impact on the mental health of children.
- Source: http://www.ncbi.nlm.nih.gov/pubmed/25147109
2015: A study focused on analyzing whether brain volume was influenced by exposure to fine particulate matter pollutants in elderly women. Researchers recruited 1,403 older women without neurodegenerative diseases and analyzed brains with MRI neuroimaging. They specifically focused on determining the volume of gray matter and white matter.
Estimates were made to determine particulate matter exposure, and various adjustments were made to rule out confounding factors. It was noted that women exposed to greater particulate matter had significant reductions in white matter volume. There was a correlation between total exposure to fine particulate matter and average volume of white matter.
Results indicated that white matter was noticeably reduced in the corpus callosum, frontal lobe, and temporal lobe. Researchers concluded that exposure to fine particulate matter contributes to white matter reductions in elderly women.
- Source: http://www.ncbi.nlm.nih.gov/pubmed/26075655
2014: An interesting report was published in 2014 hypothesizing the effect of air pollution exposure while exercising on cognitive function. Researchers noted that BDNF levels are associated with the psychological benefits of exercise such as cognitive enhancement; they are also associated with growth of new brain cells. Based on studies suggesting exercise is healthy for the brain, and evidence that air pollution damages the brain, authors concluded that aerobic exercise in a polluted city offsets the positive effect of exercise on cognition.
Therefore if you are exercising in a large city with polluted air, you may not be reaping the maximum benefit for your brain. Due to an increase in respiratory rate, you are likely breathing in significantly more pollutants than you would if you were walking. One may surmise that aerobic exercise in a large city may amplify deleterious effects associated with exposure to air pollution.
- Source: http://www.ncbi.nlm.nih.gov/pubmed/25119155
2014: A pilot study published in 2014 analyzed the effect of particulate matter-based air pollution on human cells. Specifically, cultures of human brain cells (microglia, neurons, and astrocytes) were exposed to ultrafine particulate matter and measures of biomarkers we recorded including to determine oxidative stress (based on reactive oxygen species) and neuroinflammation (based on proinflammatory cytokine TNF-Alpha). Results demonstrated that inflammation significantly increased based on TNF-alpha biomarkers.
Surprisingly, reactive oxygen species experienced a decrease when exposed to the particulate matter. This response is different than rodent cells, which experience an increase in reactive oxygen species when exposed to air pollution. In any regard, it appears as though neuroinflammation is a likely outcome upon exposure to particulate matter.
- Source: http://www.ncbi.nlm.nih.gov/pubmed/24999231
2014: A report published in 2014 suggested that ultrafine particulate matter is inhaled and may damage the brain. Among the most common sources of exposure to ultrafine particulate matter is traffic-emissions. Authors note that exposure to ultrafine particulate matter as a result of motor vehicle emissions is likely to evoke a neuroinflammatory response as well as increased oxidative stress.
References were mentioned to past research noting that air pollution, particularly from diesel exhaust may cause neurotoxicity. The air pollution induced neurotoxicity is thought to cause neurodegeneration and possibly neurodevelopmental disorders (e.g. autism spectrum disorder).
- Source: http://www.ncbi.nlm.nih.gov/pubmed/24524086
2014: One study sought to determine how metallic concentrations in household dust differed in hair samples of children. Researchers collected hair samples of children living in a mining area and children living in the suburbs. A total of 113 hair samples were collected from children in Bolivia, and behavior was assessed.
In the mining district, it appeared as though the children were exposed to a significant amount of metals via dust particles. Exposure to these dust particles resulted in notable behavioral differences compared to the children in the suburbs that were not exposed to significant amounts of metals via indoor dust. This suggests that indoor dust laden with metallic elements may have detrimental effects on behavior.
- Source: http://www.ncbi.nlm.nih.gov/pubmed/24762646
2013: Research published in 2013 discovered that children exposed to air pollution in Mexico City have impaired communication between the brain and immune system. This discovery was made by comparing various biomarkers in children exposed to high air pollution and comparing them to children exposed to low air pollution. Chronic exposure to air pollution resulted in systemic inflammation and neural immune response dysregulation.
Researchers speculate that millions of children end up with compromised neurophysiological functioning as a result of air pollution. It is important to increase awareness of how air pollution affects these children and implement policies to decrease exposure to pollutants.
- Source: http://www.ncbi.nlm.nih.gov/pubmed/24133408
2013: Lead is a well-established neurotoxin, and increased concentrations of lead within the bloodstream are thought to reduce intelligence (IQ) and cognitive performance. Researchers published a study in 2013 to determine whether levels of Lead within the blood affected IQ and academic performance. A total of 1,341 children from China participated in the study.
The level of Lead within the blood was assessed and intelligence tests were administered. Results indicated that children with high concentrations of Lead within the bloodstream had lower IQs than those with low levels. Academic performance was worse among the children with greater levels of Lead within their blood.
While Lead has become a less common in the U.S. as an air pollutant since its removal from gasoline, it may still be a problem in other countries. Inhalation of Lead particles clearly has a detrimental impact on cognitive function among children in poor and/or developing countries.
- Source: http://www.ncbi.nlm.nih.gov/pubmed/23734241
2012: Statistics suggest that children living in cities with high air pollution tend to have increased tau hyperphosphorylation and amyloid plaques. By comparison, children living in cities with low pollution tend to have no apparent tau hyperphosphorylation nor amyloid plaques. These biomarkers are associated with increased likelihood of developing a neurodegenerative disease (e.g. Alzheimer’s).
Researchers measured white matter hyperintensities (WMH) among children exposed to air pollution and those with low exposure to air pollution. White matter hyperintensities are linked to cognitive impairment and brain atrophy. MRIs and blood samples were collected from the children, and cognitive performance was assessed.
Children without white matter hyperintensities experienced inflammation as a result of air pollution; this was evidenced by various biomarkers. Those with white matter hyperintensities experienced increases in gray and white matter following exposure to air pollution. Authors concluded that cytokines and chemokines modulate responses to air pollution.
- Source: http://www.ncbi.nlm.nih.gov/pubmed/22531421
2012: Lead is an air pollutant that is well-known to have deleterious effects on brain development, intelligence, and cognitive function among individuals of all ages. Even low amounts of lead exposure can elicit detrimental neurodevelopmental effects, which are especially prominent among children. In the year 2000, the country of Taiwan banned “leaded gasoline” to minimize its effect as an environmental pollutant.
Researchers published a study in 2012 investigating the impact of low level exposure to Lead (Pb) among young children. Between 2001 and 2002 they recruited 430 Taiwanese pregnant women in their “third trimester” and administered questionnaires. Follow ups were conducted on the children to assess their neurodevelopment and cognitive performance.
To measure exposure to Lead, researchers collected blood samples and evaluated the amount of “whole blood” Lead as a biomarker. It was determined that even low levels of whole blood Lead resulted in lower IQs and cognitive deficits compared to other children of the same age. This study highlights that postnatal exposure to Lead such as via air pollution can provoke developmental abnormalities, delays, and cognitive impairments among children.
- Source: http://www.ncbi.nlm.nih.gov/pubmed/22280932
2012: It appears that even prenatal exposure to various pollutants can have significant implications for the neurodevelopment of an infant. A study conducted in 2012 investigated prenatal exposure to air pollutants including: PAH (polycyclic aromatic hydrocarbons) and ETS (environmental tobacco smoke). Researchers used the Wechsler Preschool and Primary Scale of Intelligence to determine IQ score when the children were 5 years of age.
A form of high-performance liquid chromatography was used to detect exposure to PAH, while ETS exposure was approximated based upon personal interviews. Following adjustment for confounds, exposure to PAH and ETS weren’t found to have significant effects on standard IQ. That said, it appeared as though measures of verbal IQ were notably lower in accordance with PAH and ETS exposure.
Authors concluded that PAH exposure (as a result of coal-burning plants) and environmental tobacco smoke may promote cognitive deficits in young children. Fortunately, the specific coal-burning plant considered in this study has since been shut down as a result of government health regulations.
- Source: http://www.ncbi.nlm.nih.gov/pubmed/22386727
2011: In 2011, it was reported that air pollution is associated with significant brain inflammation and increases likelihood of neurological disorders among both humans and animals. That said, researchers wanted to determine the outcomes associated with long-term, consistent exposure to airborne pollutants. For the study, they analyzed the CNS alterations as a result of exposure to diesel exhaust at a subchronic level.
Their goal was to determine the minimal amount of diesel exhaust it would take to prompt a neuroinflammatory and/or abnormalities of the CNS. The study involved using a total of 344 rats that were exposed to diesel exhaust as a result of inhalation over a 6 month term. Results indicated that subchronic diesel exhaust exposure increased biomarkers of TNF-alpha in nearly every region of the brain; the increase was most prominent in the midbrain area.
Other biomarkers were altered in the frontal lobes of mice and tau protein levels were elevated with increased exposure to diesel exhaust. Results suggest that subchronic exposure to diesel gasoline may elicit neurological changes associated with development of both Alzheimer’s and Parkinson’s disease. Prior to the noted increases in biomarkers, neuroinflammatory responses were apparent, suggesting that inflammation is apparent prior to protein increases.
- Source: http://www.ncbi.nlm.nih.gov/pubmed/21864400
2011: It was noted that exposure to significant air pollution prompts inflammatory and structural changes in the brains of children. A study in 2011 sought to determine links between brain growth patterns, cognitive dysfunction, and white matter hyperintensities (WMH) may stem from exposure to airborne pollutants. Researchers conducted baseline measures in children with MRI scans (to determine volume) and intelligence tests (to determine cognitive function).
Children from Mexico City were compared based on whether they were noted as having white matter hyperintensities (+) versus not having white matter hyperintensities (-) and were compared to controls from a city without pollutants. Researchers noted significant deficits in white matter volumes among children from Mexico City, regardless of white matter hyperintensities. These differences were most apparent in the bilateral temporal region and right parietal lobe.
The children living in Mexico City performed poorer on a spectrum of cognitive assessments compared to children in the low-pollution control group. Researchers concluded that air pollution exposure may alter the neurodevelopment of children and ultimately cause cognitive impairment. Therefore it is important to recommend taking action to minimize exposure to air pollution, particularly among children with developing brains.
- Source: http://www.ncbi.nlm.nih.gov/pubmed/22032805
2010: A study conducted in Poland involved determining whether prenatal exposure to air pollution in an urban environment may cause disordered behavior and neurological functioning. Specifically, researchers investigated exposure to PAH (polycyclic aromatic hydrocarbon) and intelligence among children at 5 years. They controlled for a variety of potential confounding factors that may also influence neurodevelopment.
All of the pregnant women participating in the study were considered non-smokers and “healthy.” During pregnancy, a questionnaire was administered and air samples were collected to determine air quality. In addition, blood samples were collected from babies at time of delivery. Following baseline measures, 214 children were followed until the age of 5.
These children were given a nonverbal reasoning ability test called the Raven Colored Progressive Matrices (RCPM). Results indicated that greater exposure to PAH resulted in significantly decreased scores on the RCPM assessment, suggesting lower nonverbal reasoning skills. Researchers went as far as to estimate that IQ decreased by 3.8 points among those prenatally exposed to PAH.
- Source: http://www.ncbi.nlm.nih.gov/pubmed/20406721
2009: A similar study was conducted among pregnant African-American and Dominican-American women in New York City. Researchers sought to determine exposure to PAH by assessing air quality of the women during pregnancy. Follow ups with 249 children were conducted at age 5.
All of the children were assessed for intelligence using the Wechsler Preschool and Primary Scale of Intelligence (Revised). After adjusting for a variety of confounds, it was discovered that prenatal PAH exposure was associated with significantly reductions in both full-scale and verbal IQ. Estimates suggest that IQ scores were 3 to 5 points lower among the mothers exposed to significant airborne PAH.
This demonstrates that air pollution can affect cognitive development among children even in the United States, with New York City as an example. Pregnant mothers should be especially concerned with minimizing exposure to environmental air pollution in effort to maximize the neurodevelopmental potential of their children.
- Source: http://pediatrics.aappublications.org/content/124/2/e195.abstract
2009: An array of animal research has discovered that exposure to particulate matter (particularly “ultrafine”) can cause brain inflammation. This particulate matter is inhaled via respiration and is transmitted from the upper respiratory tract directly to the brain, where it can accumulate and cause damage. Brain inflammation is associated with nearly every serious neurological disorder.
A study conducted in 2009 sought to determine whether long-term exposure to ultrafine atmospheric particulate matter could facilitate neurodegeneration in the form of mild cognitive impairment (MCI) – a condition that often leads to Alzheimer’s. Researchers recruited 399 elderly women who lived for 20+ years at the same address. Estimates were calculated for particulate matter concentrations and traffic-related particulate matter.
All 399 women were administered a test to detect mild-cognitive impairment (MCI). Researchers noticed specifically that exposure to traffic-related particulate matter exposure was associated with mild cognitive impairment. Authors go as far as to suggest that particulate matter exposure may increase risk of Alzheimer’s disease.
- Source: http://www.ncbi.nlm.nih.gov/pubmed/19733348
2008: Researchers published a study in 2008 determining whether living in cities with high air pollution is associated with neuroinflammation and/or neurodegeneration. They focused on measuring various biomarkers in the brains of healthy children and young adults that died unexpectedly. Biomarker measures included: mRNA cyclooxygenase-2, interleukin-1beta, and CD14 in specific regions of the brain.
A total of 12 brains were from areas of low air pollution exposure, while 35 brains were from high pollution areas. Results indicated among brains highly exposed to air pollution, the measures of: cyclooxygenase-2, interleukin-1beta, and CD14 had significantly increased. Moreover, blood-brain barriers were disrupted, inflammation was evident, and oxidative stress had increased.
Researchers could literally see the accumulation of particulate matter within neurons (brain cells) of those that were highly exposed to pollution. Biomarkers that increase likelihood of developing neurodegenerative diseases like Alzheimer’s and Parkinson’s were noted even among children in the environment with significant air pollution. This study portrays the alarming consequences associated with living in a pollution-filled city.
- Source: http://www.ncbi.nlm.nih.gov/pubmed/18349428
2008: It is known that exposure to air pollutants increase risk of a variety of neurological conditions. Researchers suspected that one major risk associated with exposure to significant pollutants is that of brain cancer. They conducted a study to determine whether there was a relationship between air pollution in the form of petrochemicals and increased incidences of brain cancer.
Researchers collected records of all brain cancer fatalities in Taiwan spanning from 1995 to 2005. They also collected data of petrochemical pollutant exposure based on each of the individuals’ living address. It was discovered that those living in areas with high amounts of petrochemical air pollution had the highest risk of developing brain cancer compared to those in areas with minimal petrochemical air pollutants.
- Source: http://www.ncbi.nlm.nih.gov/pubmed/18214804
2008: Past research has documented that brain inflammation results from exposure to air pollution in Mexico City. This inflammatory response doesn’t only occur among humans, but is apparent among canines. Researchers conducted more research to determine the effects of ambient air pollution on a total of 55 children from Mexico City compared to 18 children living in a low polluted city.
All were assessed with MRI neuroimaging and administered psychometric tests. MRI scans were also conducted on 7 healthy canines exposed to air pollution in Mexico City. The brains of these canines indicated an increase in frontal lesions, neuroinflammation, and accumulated deposits of particulate matter.
Researchers determined that children exposed to air pollutants had poorer performance on cognitive tasks – both “fluid” and “crystallized.” Over half of the children from Mexico City demonstrated white matter lesions within the prefrontal cortex. It is speculated that air pollutants from Mexico City damage the prefrontal cortex and promote cognitive impairment in otherwise healthy children.
- Source: http://www.ncbi.nlm.nih.gov/pubmed/18550243
2007: It was noted that individuals residing in Mexico City are exposed to significant ground-level ozone and ultrafine particulate matter. Even dogs living in Mexico City have been discovered to have significant neuroinflammation and neurodegeneration (similar to Alzheimer’s). Among residents of Mexico City (regardless of age), biomarkers such as COX2, IL-1beta, and ABeta 42 accumulate in the frontal cortex as a result of air pollution.
Due to the fact that Alzheimer’s disease is associated with both brain inflammation and accumulation of ABeta 42, it is not farfetched to hypothesize that exposure to air pollution could cause Alzheimer’s disease. In addition, exposure to air pollution may amplify risk and/or rapidity of neurodegeneration among those already experiencing mild-cognitive impariment.
- Source: http://www.ncbi.nlm.nih.gov/pubmed/17325984
2004: More research highlights the fact that dogs exposed to air pollution experience neuroinflammation and Alzheimer’s-like brain changes. A study published in 2004 investigated whether individuals living in cities with significant levels of air pollution experienced neuroinflammation. To assess inflammation, they documented COX2 expression and beta-amyloid 42 (ABeta 42).
A total of 19 brains were evaluated with tissue autopsies, 9 were from cities with low pollution, while the remaining 10 were from polluted cities. It was determined that individuals from cities with high air pollution had greater COX2 expression in multiple regions (the frontal cortex and hippocampus) and greater accumulation of beta-amyloid 42. This suggests that the brain is susceptible to inflammation and preclinical symptoms of neurodegeneration as a result of air pollution.
- Source: http://www.ncbi.nlm.nih.gov/pubmed/15513908
2003: A study published in 2003 discussed the implications of air pollution among dogs living in Mexico City. Authors of the study note that air pollutants enter the body via the respiratory tract and are capable being transmitted from the respiratory tract to the brain. To determine the effects of air pollutants on the brain of dogs in Mexico City, researchers measured various biomarkers including: NFkappaB p65, iNOS, COX2, APP, ABeta 42, APOE, MT1, and MT2.
A total of 40 young dogs (mongrels) were assigned to live in a high-pollution (26) or low pollution environment (14). Results indicated that pollutants of Nickel and Vanadium were noted within various regions of the brains. Dogs exposed to significant pollution had greater levels of nearly every aforementioned biomarker (e.g. COX2, APP, ABeta 42, etc.) compared to the dogs living in cities with low pollution.
Evidence indicated that the dogs displayed brain changes similar to preclinical Alzheimer’s pathology in humans. The greater the exposure to air pollutants, the more substantial the neurological abnormalities. Moreover, it appears as though respiratory and olfactory barriers as a result of pollution results in greater future exposure and heightened inflammation.
- Source: http://www.ncbi.nlm.nih.gov/pubmed/14692621
2002: Another study conducted on canines (mongrels) in Mexico City sought to assess whether air pollution resulted in variations in the expression of unhealthy biomarkers. Specifically, the study assessed NF-kappaB, iNOS, cortical structures, and subcortical structures from mongrel canines. A total of 32 mongrels from Mexico City were assessed and compared to 8 mongrels from a low pollution city (Tlaxcala).
It was noted that the dogs exposed to pollutants in Mexico City experienced significant increases in NF-kappaB, and iNOS biomarkers. In addition, it appeared the blood-brain barrier was damaged (and altered), cortical neurons had experienced degeneration, and white matter cells were being destroyed. In addition, APOE deposits and other plaques had also increased – indicating that early-onset Alzheimer’s may result from air pollution.
- Source: http://www.ncbi.nlm.nih.gov/pubmed/12051555
1996: It is well-known that cigarette smoke is toxic and full of carcinogens. In 1996, researchers investigated whether smoking cigarettes during pregnancy would influence intelligence of the newborn children. Two samples of children were compared: one from mothers who smoked during pregnancy and the other from non-smoking mothers.
All children were assessed with the Wechsler scale to measure their intelligence. After considering various confounds, it was determined that smoking during pregnancy decreased intelligence by approximately 15 IQ points. Researchers speculate that the pollutants from smoking cigarettes penetrate the placental barrier and detrimentally impact the neurodevelopment of the fetus.
- Source: http://www.ncbi.nlm.nih.gov/pubmed/9216801
How to Avoid Air Pollution and Maintain Brain Health
The aforementioned research should provide you with a sense of urgency to avoid air pollution. Those who aren’t avoiding air pollution run the risk of neuroinflammation, impaired cognitive function, and increased risk of neurodegeneration. Below are some suggestions to help you maximize your air quality and minimize the likelihood of air pollution-induced neurological pathologies
Consciously choose your residence
Many people live in large, crowded urban cities with significant air pollution. Some people may have lived in these cities for their entire lives, while others may gravitate towards these cities for job opportunities. While large cities certainly have plenty of job opportunities, they also have significant air pollution.
Before you blindly accept living in a large city, you may want to consider the fact that the air quality may be poor. Should you choose to live in a large city, it’s really a matter of time before ultrafine particulate matter and other airborne toxins are inhaled and transmitted from your respiratory tract to your brain. They accumulate within your brain, promoting neurodegeneration and expediting development of Alzheimer’s.
You may want to think twice about where you live and look up the air quality. Sometimes looking up the air quality may not be as helpful as giving the air a “sniff” – if it doesn’t smell fresh or smells polluted, it may have deleterious effects on your brain. Choose a residence with low traffic-related pollution and clean air.
Get your air tested (and cleaned)
There are many independent companies that will test the air quality inside and outside your home to determine whether it is within a safe range for breathing. While it is relatively easy to determine outdoor air quality, indoor air quality is often difficult to determine. Many people use sprays, candles, and other “fresheners” that are laden with chemicals.
These chemicals may be of a pleasant odor, but may be damaging your brain each time they are inhaled. Indoor air shouldn’t have any significant amounts of mold, lead, or radon. If you suspect that you may have mold, it is best to get an ERMES test, which compares the density of mold particles within your home to those outside.
If you live in an area with low pollution, you can easily open your windows to “air out” your house of any chemicals and circulate fresh air. Those living in an urban environment may run the risk of inhaling unpleasant exhaust and other noxious intoxicants each time they attempt to “air out” their homes. If you suspect that your home is full of a particular pollutant, your best bet is to test for it.
The presence of indoor plants is helpful for filtering out certain pollutants that may be floating through the air. Plants are known to promote cleaner air and reduce exposure to indoor air pollution. Therefore it may be beneficial to maximize the number of indoor plants you can accommodate within your home.
There is even evidence that having desk plants at work can improve mood and substantially increase productivity. It is estimated that plants are capable of removing nearly 90% of volatile organic compounds (VOCs) from the air every 24 hours. Various VOCs in your home could include: benzene, formaldehyde, and trichloroethylene (all of which are found in man-made materials).
Indoor plants can purify the air by literally pulling contaminants into their soil. Once they are pulled into the soil, microorganisms within the root system convert the volatile organic compounds into food that helps the plant grow. As a rule of thumb, some sources suggest having approximately one large plant (6″ to 8″ diameter) for every 100 square feet.
Plant trees in your yard
Assuming you have a yard, one of the best ways to clean up the air is to plant trees. When we breathe, our body inhales oxygen and exhales carbon dioxide. Trees replenish our supply of fresh air by absorbing carbon dioxide and producing oxygen.
In addition, trees are able to intercept air pollutants such as carbon monoxide, ground-level ozone, and sulfur dioxide. Intercepting these pollutants results in cleaner, more purified air. Due to the fact that air pollution is linked to a variety of neurological disorders, it makes logical sense that living near trees is linked to increased less antidepressant prescriptions.
In addition to absorbing air pollution, trees are also able to filter fine particulate matter from the air by trapping it within their leaves and bark. Ultrafine particulate matter is considered extremely damaging to the brain, especially when inhaled over the long-term. Therefore an increased number of trees in your yard could help mitigate the problem.
Spend time in nature
If you cannot escape your residence within a smog-filled city, do your best to escape whenever possible. Find a local nature park and/or visit a place with cleaner air than your current residence. Spend as much time within this cleaner environment as possible as this will help you minimize inhalation of ultrafine particulate matter that would occur at your urban residence.
There is increasing evidence to suggest that nature is beneficial for a person’s mental health. It is clear that inhalation of air pollution results in suboptimal mental health and brain functioning. Therefore, certain beneficial effects of nature on mental health may be a result of increased inhalation of purified air and/or improved air quality in a naturalistic setting.
Avoid indoor air contaminants
I want to emphasize the importance of avoiding chemical products (e.g. cosmetic sprays) that are chock-full of toxic chemicals. These sprays may “smell good” to your average person, but there are clear concerns associated with inhalation of these chemicals. Do your best to minimize usage of any sprays, regardless of whether they’re for cleaning or cosmetic purposes if you want to maintain healthy indoor air.
Should you end up using any indoor spray, it is best to do it near a ventilation system that rapidly filters out the airborne chemicals. Opening the windows for increased natural airflow may help eradicate your house of “chemical smells” should they accumulate as a result of contaminant usage. Unfortunately, many individuals are ignorant to the long-term consequences of aerosol sprays, perfumes, wall “plug ins,” and cleaning products.
Have you been exposed to air pollution?
If you’ve been exposed to acute and/or long-term air pollution, feel free to share whether you believe it has had a significant impact on your mental health. To help others understand your situation, discuss how long you were exposed to air pollution, the severity of the pollution, and whether you developed any neurological conditions. Also mention the specific type of air pollution to which you were exposed (if you are aware of it).