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Air Pollution Leads to “Huge Reduction” in Intelligence

Natalie Frank, a Ph.D. in clinical psychology, specializes in pediatric psychology and behavioral health.


According to a 2018 study, air pollution leads to a “huge reduction” in intelligence. The impact of breathing high levels of pollution regularly is “equivalent to having lost a year of education,” the study finds. As worrisome as the effects of pollution, a well-known health hazard, are on physical health, this research suggests that the damage of air that is poisonous to the body goes deeper than that, damaging the brain as well. The research, conducted in China, is relevant for people all over the world. Estimates suggest that 95% of the global population is currently breathing air that is dangerous to their health and well-being.

What Is Air Pollution?

Air pollution occurs when excessive amounts of dangerous or harmful substances, including gases, particulates, and biological molecules, find their way into the air. There are two general categories of air pollution that create problems for people and the environment: primary air pollution and secondary pollutants.

Primary Air Pollution

Primary air pollution consists of pollutants that are fully formed when they enter the atmosphere. Examples of primary air pollution include:

  • Carbon oxides include carbon monoxide (CO) and carbon dioxide (CO2). Carbon monoxide is toxic to plants, animals, and people. CO and CO2 are both greenhouse gases. Rising levels of carbon dioxide in the atmosphere can lead to destructive weather patterns, harm to the oceans, alteration of species migration, negative impacts on agriculture, and deadly health effects. These types of pollution are particularly dangerous in that they are colorless, odorless gases that require special devices to detect.
  • Lead is a heavy metal that was once used in paint, the inside of pipes, and car fuels. Lead can cause brain damage and blood poisoning.
  • Volatile organic compounds (VOCs) are also considered the be primary air pollution. These are hydrocarbons such as methane, another greenhouse gas that is growing because of humans, chlorofluorocarbons, which has negatively affected the ozone layer, and dioxin, a negative byproduct of chemical products that is harmful to people and animals.

Secondary Pollutants

Secondary pollutants are formed by pollutants coming together and react in the atmosphere. Secondary pollutants include:

  • Nitrogen oxides are produced when nitrogen and oxygen come together and are caused to react by high temperatures. This happens in heated car exhaust gas and the emissions from power plants or factories.
  • Sulfur oxides develop when sulfur created by burning coal and sulfur trioxide include sulfur dioxide (SO2) and sulfur trioxide (SO3) combine and enter the atmosphere. Sulfur oxides are part of acid rain.
  • Particulates are particles like volcanic ash and dust. They come from combustible fossil fuels and lead to smog. Smog can lead to the development and exacerbation of asthma, cardiac disease, respiratory illness, and cancer.
  • Ozone develops when hydrocarbons and nitrogen oxides combine in the presence of sunlight

The Burden of Toxic Air

It is no surprise that the poorest communities are hit the hardest by air pollution. The difference between the most and least polluted countries is growing rapidly. These findings were reported from a comprehensive study of global air pollution. Cities and urban areas are the most dangerous places for polluted air and these areas are home to the majority of the world’s population.

This means that billions of people are exposed to unsafe air. Developing countries are the ones with the highest rates of toxic air. Yet this isn’t the whole story. In rural areas, the risk of air pollution is greatest indoors resulting from burning solid fuel, where it is concentrated. Over 33 percent of the world’s people are exposed to bother indoor and outdoor air pollution. Air pollution is now the fourth highest cause of death worldwide after diet, smoking, and high blood pressure. It is considered to be the largest environmental health risk

How Does Air Pollution Affect Health?

For more than 30 years, environmental studies have been determining the effects of polluted air on the human body. There are a wide variety of physical problems that are associated with exposure to air pollution including asthma, bronchitis, emphysema, and other respiratory illnesses, decreased lung function, cardiovascular disease, birth defects, premature birth and other adverse pregnancy outcomes, Alzheimer's and other forms of dementia and death. The WHO has determined that air pollution is cancer-causing in humans.

Those most susceptible to developing major health problems from air pollution exposure are:

  • Individuals with heart disease, coronary artery disease or congestive heart failure

  • Individuals with lung diseases such as asthma, emphysema or chronic obstructive pulmonary disease (COPD)
  • Pregnant women
  • Individuals who work outdoors
  • Older adults
  • Children under age 14
  • Athletes and others who exercise vigorously outdoors

How Does Pollution Affect the Brain?

Previous studies have demonstrated that children and young adults are particularly at risk for inflammation of brain tissue and disruption of the blood-brain barrier as the result of long-term exposure to toxic air. The effects on the brain are not limited to the young. There is a growing body of evidence that suggests that air pollution may be a major cause of Alzheimer's and Parkinson's.

It has been indicated that pollution particles from burning fossil fuels may enter the brain through the nasal nerve. These particles may have heavy metal neurotoxins attached to them, which kill neurons directly. They can also cause by triggering a continuous immune response in the brain. This can lead to a buildup of amyloid-beta plaques typically seen in people prior to the onset of Alzheimer’s or dementia state (Calderón-Garcidueñas, Calderón-Garcidueñas, Torres-Jardón, Avila-Ramírez, Kulesza, & Angiulli, 2015).

Amyloid-beta plaques have also been found in the brains of children in cities with serious air pollution. Other types of brain damage, such as vasculature and leaky blood-brain barriers have also been found in these children (Calderón-Garcidueñas, Leray, Heydarpour, Torres-Jardón, & Reis, 2016). While the greater resiliency provides some protection against the severe types of brain disorders seen in older adults, these kinds of damage are associated with lowered IQ.

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In some cities like Beijing, China people wear masks to avoid air pollution.

In some cities like Beijing, China people wear masks to avoid air pollution.

Air Pollution Leads to Drop in Intelligence

The study conducted in China found that high pollution levels were associated with significant drops in test scores in language and arithmetic. The average scores were found to be equivalent to a loss of one year of education. These findings are consistent with those of previous studies, which showed that previous air pollution had a negative effect on children’s cognitive abilities.

“Polluted air can cause everyone to reduce their level of education by one year, which is huge,” said Xi Chen at Yale School of Public Health, a member of the research team. “But we know the effect is worse for the elderly, especially those over 64, and for men, and for those with low education. If we calculate the loss for those, it may be a few years of education.”

Previous research has found that air pollution harms achievement and performance in students in limited areas of the world, but this is the first to assess people of all ages and to compare genders.

Regarding age, the reduction in intelligence was greatest for those over 64 years of age. This has serious consequences as this is the time we make many important decisions, especially financial ones.

Other studies have found that air pollution was associated with high death rates in people with mental disorders, increased risk of mental illness in children, and increased risk of dementia.

The 2018 study, published in the journal Proceedings of the National Academy of Sciences, examined language and arithmetic tests that were conducted as part of the China Family Panel Studies. Over 20,000 people across the country were evaluated over the course of five years, and their results were compared with levels of nitrogen dioxide and sulfur dioxide pollution.

Results indicated that the longer people were exposed to toxic air, the greater the reduction in intelligence. Language skills were impacted more severely than mathematical skills, with men showing greater overall reductions than women. Some hypothesis that this is due to differences in how male and female brains function.

Though further tests need to be conducted, it is believed that air pollution was the cause of the drop in intelligence and not just being a correlation. Researchers attribute part of the problem to the fact that toxic air is associated with oxidative stress, neuroinflammation, and neurodegeneration.

The study longitudinal such that the same subjects were followed over time, so factors such as genetic differences that might account for the findings were controlled for. The scientists also controlled for the normal decline in cognition that occurs with age and ruled out other factors such as the tendency of participants to be more impatient, impulsive in answering, or uncooperative on the days when pollution was exceptionally high.

Air pollution was also found to have short-term effects that could have important ramifications for important events in a person’s life, such as when students must take critical exams on days with high pollution. The effect is likely cumulative with and increase in pollution by 1 mg over several years might lead to a several month loss in intelligence.

How Can I Protect Myself From Air Pollution?

Though there isn’t much you can do to completely avoid air pollution, there are some things you can do to help protect yourself from the effects.

  • Avoid walking or exercising along busy streets.
  • Check air pollution levels daily and refrain from going outside as much as possible when these levels are high.
  • When pollution is high, stain indoors with an air conditioner running that has a clean filter.
  • When pollution is high, avoid activity to decrease heavy breathing and intake of the pollutants.
  • In some cities where smog can reach dangerous levels, tight-fitting masks should be worn to seal out as much of the pollutants as possible. Surgical masks, handkerchiefs, and the like are ineffective as the air gets around them.
  • In some countries, relatively inexpensive air quality monitors can be purchased and mounted on the outside of the house to measure air pollution so you can keep track of the levels.
  • Replace wood-burning fireplaces with natural gas ones.
  • Don't allow anyone to smoke in your home.
  • Use the recycled air feature in your car, rather than the vents to cool off in the car
  • Replace gas-powered machines, like lawn mowers and leaf blowers, with electric or battery-powered ones.
  • Install a home air filter that blocks air pollution.

Summary and Conclusions

In China, although air pollution is being cleaned up, it is still over three times higher than the World Health Organization limits. Realizing the impact of air pollution on the health of its citizens, China, home to several of the cities with the greatest amount of toxic air pollution, has been attempting to fight against pollution for the past seven years.

Road traffic makes the largest contribution to air pollution in residential areas. Governments need to act together to agree to remove heavy polluting vehicles from the streets.

There is clearly no easy solution to this problem, especially given the years that we have been attempting to control air pollution, which may have made a dent but not much more. It is difficult to form a universal position on cleaning up the environment when the problem can’t always be seen or felt. Adding to this, Government and other world leaders are often more interested in protecting national resources than something that can’t be controlled at the borders.

Focusing on how cleaning up air pollution may increase human capital and help the workforce could help influence the development of more impactful measures for curbing pollution. Human capital is one of the most significant driving forces of economic growth worldwide. If governments understand that the human capital of their nation is at risk because of air pollution, this might be an added incentive to clean up the air.


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This content reflects the personal opinions of the author. It is accurate and true to the best of the author’s knowledge and should not be substituted for impartial fact or advice in legal, political, or personal matters.

© 2018 Natalie Frank

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