How Air Pollution Can Harm Brain Health

It has long been rather stunning to me how careless many people are about air pollution. One of the most important things that people shouldn’t do is drive with their windows down in areas with significant traffic (and thus significant amounts of air pollution from vehicles). The motive for caring is rather simple — air pollution’s negative impact on brain health means possibly reduced performance on a variety of tasks, and that can negatively correlate with achieving life goals, which in turn is detrimental to human happiness and satisfaction.

Long thought to primarily harm the lungs and cardiovascular system, air pollution is now catching the attention of neuroscientists and toxicologists.

The buzz of a leaf blower and its gaseous fumes fill the air outside a lab facility at the University of Washington in Seattle. Inside the building, neurotoxicologist Lucio Costa is investigating how polluted air—such as garden tool exhaust—could be bad for the brain.

Next to the building sits a 5,500-watt diesel generator, enclosed in a metal box. Pipes carry the diesel exhaust—the same stuff emitted by diesel engines in vehicles and heavy equipment—into the facility, across an exposed ceiling and into a room where plastic cages of mice are stacked high against the wall. Tubes filter the diesel exhaust through the cages, Costa explains, in an effort to mimic the contaminated air you might breathe while sitting in traffic or living near a busy road.

After spending most of his career studying mercury, pesticides, and flame retardants, Costa knows well that many toxins in the environment can hurt the brain. But only in the last several years has the possibility of air pollution as a culprit crossed his mind. A growing body of literature on the topic inspired him to begin research in this diesel lab. “For a long time, I thought that air pollution was affecting mostly the lungs and the cardiovascular system and not the brain,” says Costa. “So I stayed away from any issue related to air pollution.”

Now, mounting evidence seems to link a variety of neurological problems to dirty air. Troubling recent findings include hallmarks of Alzheimer’s disease found in the brains of children living in Mexico City (1) and a nearly doubled risk of dementias for older women in highly polluted parts of the United States (2). Costa’s own research has identified autism-like social and behavioral issues in mice exposed to diesel exhaust (3). Today, Costa is among a growing cadre of biologists, toxicologists, and doctors raising the alarm over this pervasive yet overlooked menace to our memory, attention, and behavior.

A Global Threat

Although the coronavirus disease 2019 (COVID-19) pandemic and associated “shelter in place” policies have reduced fossil fuel use to offer a temporary respite from extreme pollution in some places, most countries face an ongoing epidemic of dirty air as a result of growing urban congestion and an uptick in climate-driven wildfires, among other factors. Indoor air pollution further plagues many of the world’s poorest communities. Around 3 billion people cook indoors over open fires or stoves fueled by wood, biomass, kerosene, or coal. In 2018, the World Health Organization (WHO) identified air pollution as the second-largest risk factor for noncommunicable disease worldwide. And the WHO’s stats don’t include the full range of neurological effects now being discovered, notes neurotoxicologist Deborah Cory-Slechta at the University of Rochester in New York.

Globally, more than 90 percent of people breathe air that fails to meet WHO standards. That includes an estimated four in 10 people in the United States, although efforts such as the US Clean Air Act and its amendments of 1990 have helped. Between 2000 and 2016, the average concentration of particulate matter (PM) with a diameter of less than 2.5 micrometers (PM2.5), tiny particles produced by combustion, fell by around 40 percent in the United States. But the country’s overall air quality has worsened since 2016. Partly to blame is a rise in wildfire smoke, which is now responsible for an estimated 40 percent of particulate matter pollution.

Yet cleaner, healthier air remains achievable, notes Dean Schraufnagel, a pulmonologist at the University of Illinois at Chicago. “There are no death certificates that say air pollution exposure,” he says. “But we know that air pollution affects every organ in the body. If we stop the air pollution at its source, we can get strikingly important health benefits.”

Schraufnagel, also the director of the Forum of International Respiratory Societies, points to one easy target: idling diesel-powered school buses. A 2019 study out of Georgia in the United States found that districts that retrofitted school buses to reduce diesel emissions reported significant increases in students’ English test scores as well as smaller improvements in math (4).

The havoc air pollution can wreak on the brain is also a new area of interest for Schraufnagel, whose research and clinical practice has long focused on lung disease. Today, he is working with international organizations to get air pollution on the minds of not just pulmonologists but also neurologists and other medical experts. “This should be a call to action,” adds Schraufnagel.

Air pollution is a cocktail of suspended gases, solids, and liquid particles. While this mix contains numerous hazardous ingredients, such as ozone, sulfur dioxide, and carbon monoxide, the component that appears most concerning for the brain is PM.

The US Environmental Protection Agency (EPA) regulates PM10 and PM2.5, defined as particles less than 10 and 2.5 micrometers in diameter, respectively. PM2.5, also known as fine particulate matter, generally comes from smoke, dust, and vehicle exhaust. Because PM2.5 is so tiny—30 times smaller than the width of the average human hair—it can remain airborne for long periods of time, infiltrate buildings, and penetrate the body. Ultrafine particles, which measure less than 0.1 micrometer across, may be even worse offenders. Yet the miniscule mass of these particles makes them difficult to monitor. They remain unregulated by the EPA.

Fine and ultrafine particulate matter tends to circumvent the mechanisms that the human body has evolved to deflect, detain, and destroy unwelcome visitors. “The health effects of air pollution are all about particle size,” says Cory-Slechta. Studies suggest that these tiny particles can even go up the nose and be carried straight to the brain via the olfactory nerve (5)—hence bypassing the blood–brain barrier. And they don’t travel alone. On their surfaces these particles carry contaminants, from dioxins and other chemical compounds to metals such as iron and lead. “PM is simply acting as a vector,” says Masashi Kitazawa, a molecular neuropathologist at the University of California, Irvine. “It might be a number of chemicals that get into the brain and act in different ways to cause damage.”

Because of their large surface area relative to their volume, the smallest particles are the biggest offenders. Cory-Slechta’s research has largely focused on lead and mercury, neurotoxic metals that are abundant in air pollution. “Ultrafine particles are like little Trojan horses,” she says. “Pretty much every metal known to humans is on these.”

Metal-toting particles that reach the brain can directly damage neurons. Both the particles themselves and their toxic hitchhikers can also cause widespread harm by dysregulating the activation of microglia, the immune cells in the brain. Microglia may mistake the intruders for pathogens, releasing chemicals to try to kill them. Those chemicals can accumulate and trigger inflammation. And chronic inflammation in the brain has been implicated in neurodegeneration (6).

Particles may also afflict the brain via the bloodstream. Research shows that small particles can slip through the plasma membrane of alveoli—the tiny air sacs in the lungs—and get picked up by capillaries. The particles are then distributed around the body in the blood. Although some of these particles may eventually breach the blood–brain barrier, a pollutant need not enter the brain to cause trouble there. The immune system can react to particles in the lung or bloodstream, too, triggering widespread inflammation that affects the brain.

Even an ingested particle could have indirect neurological effects, via the gut. Researchers now recognize strong connections between the gut microbiome and the brain (7), and studies show that delivering fine particles to the gut can cause systemic inflammation (8).

In January 2010, Cory-Slechta received a surprising request from some University of Rochester environmental medicine colleagues. Typically, the group researched the effects of air pollution on the lungs and hearts of adult animals. But they had just exposed a group of newborn mice and asked Cory-Slechta’s team to look at the brains.

At first she didn’t think much of the request. Cory-Slechta was much more concerned about deadly lead exposure in children, her research focus at the time. “I didn’t think of air pollution as a big problem for the brain,” she says. Then she examined the animals’ tissue. “It was eye-opening. I couldn’t find a brain region that didn’t have some kind of inflammation.”

Her team followed up with their own studies. In addition to inflammation, they saw classic behavioral and biochemical features of autism, attention-deficit disorder, and schizophrenia in mice exposed to pollutants during the first days after birth. The mouse brains had noticeably less white matter, particularly in the corpus callosum connecting the right and left cerebral hemispheres. In work published last November, Cory-Slechta’s group further linked short-term exposures to air pollution with impaired learning and memory in aged mice, based on measures of spontaneous movement, navigation of a maze, short-term object recognition, and the ability to discriminate odors (9). The concentrations of particulate matter used, she notes, “easily include sitting in traffic in major cities.”

[…]

Research in Ontario, Canada, found that living farther away from a major road lowered the risk of developing dementia (13). A study of nearly 3,000 Barcelona schoolchildren found that those attending schools with more traffic pollution had slower cognitive development (14). And in the United States, a study found that living in locations where ambient particulate matter exceeded EPA recommendations nearly doubled women’s risk of developing dementia. When those researchers looked specifically at older women with two copies of the APOE4 gene variant, a strong genetic factor for Alzheimer’s disease, the dementia risk associated with living in those locations jumped almost threefold (2).

Prolonged Exposure to Air Pollution Linked to Negative Genetic Changes in Mice

Air pollution — consistently being shown to be a pretty significant issue to public health.

Prolonged exposure to particulate matter in air pollution in the Los Angeles Basin triggered inflammation and the appearance of cancer-related genes in the brains of rats, a Cedars-Sinai study has found.

While previous research has documented the association between air pollution and a variety of diseases, including cancer, the study found markers indicating certain materials in coarse air pollution — nickel, in particular — may play a role in genetic changes related to disease development, said Julia Ljubimova, MD, PhD.

Ljubimova, director of the Nanomedicine Research Center at Cedars-Sinai, is the lead author of the paper, published April 9 in Scientific Reports.

“This study, which looked at novel data gathered in the Los Angeles area, has significant implications for the assessment of air quality in the region, particularly as people are exposed to air pollution here for decades,” Ljubimova said.

Study: Personal Care Products Inhaled en Masse Contribute to Harmful Pollution “Rush Hour”

As if the air in much of the world wasn’t already polluted enough, this study reconfirms the importance of changing transportation systems to be far less dependent on fossil fuels and also the apparent importance of designing better personal care products.

When people are out and about, they leave plumes of chemicals behind them — from both car tailpipes and the products they put on their skin and hair. In fact, emissions of siloxane, a common ingredient in shampoos, lotions, and deodorants, are comparable in magnitude to the emissions of major components of vehicle exhaust, such as benzene, from rush-hour traffic in Boulder, Colorado, according to a new CIRES and NOAA study.

This work, published in the journal Environmental Science and Technology, is in line with other recent findings that chemical emissions from personal care products can contribute significantly to urban air pollution.

“We detected a pattern of emissions that coincides with human activity: people apply these products in the morning, leave their homes, and drive to work or school. So emissions spike during commuting hours,” said lead author Matthew Coggon, a CIRES scientist at the University of Colorado Boulder working in the NOAA Earth System Research Laboratory.

D5 Siloxane, short for decamethylcyclopentasiloxane, is added to personal care products like shampoos and lotions to give them a smooth, silky feeling. Siloxane belongs to a class of chemicals called volatile organic compounds (VOCs); once applied, they evaporate quickly. In the air, sunlight can trigger those VOCs to react with nitrogen oxides and other compounds to form ozone and particulate matter — two types of pollution that are regulated because of their effects on air quality and human health.

[…]

This study is part of an emerging body of research that finds emissions from consumer and industrial products are important sources of urban air pollution. A recent study in Science, led by CIRES and NOAA’s Brian McDonald, found that consumer and industrial products, including personal care products, household cleaners, paints, and pesticides, produced around half of the VOC emissions measured in Los Angeles during the study period.

Study: Cutting Carbon Emissions Sooner Would Likely Save Millions of Lives

There’s absolutely no positively justifiable reason that fossil fuels should still be used anywhere near their levels today, and this is another reason why.

As many as 153 million premature deaths linked to air pollution could be avoided worldwide this century if governments speed up their timetable for reducing fossil fuel emissions, a new Duke University-led study finds.

The study is the first to project the number of lives that could be saved, city by city, in 154 of the world’s largest urban areas if nations agree to reduce carbon emissions and limit global temperature rise to 1.5°C in the near future rather than postponing the biggest emissions cuts until later, as some governments have proposed.

Premature deaths would drop in cities on every inhabited continent, the study shows, with the greatest gains in saved lives occurring in Asia and Africa.

[…]

The new projections underscore the grave shortcomings of taking the lowest-cost approach to emissions reductions, which permits emissions of carbon dioxide and associated air pollutants to remain higher in the short-term in hopes they can be offset by negative emissions in the far distant future, said Drew Shindell, Nicholas Professor of Earth Sciences at Duke’s Nicholas School of the Environment.

“The lowest-cost approach only looks at how much it will cost to transform the energy sector. It ignores the human cost of more than 150 million lost lives, or the fact that slashing emissions in the near term will reduce long-term climate risk and avoid the need to rely on future carbon dioxide removal,” he said. “That’s a very risky strategy, like buying something on credit and assuming you’ll someday have a big enough income to pay it all back.”

Air pollution has also been found recently to have links to cognitive impairment in children.

Toxins from Air Pollution Damage Child Development and Disproportionately Affect Those in Poverty

Air pollution causes health damage that’s too often overlooked, and the research that’s coming out has been showing this more and more lately.

Schoolchildren across the US are plagued by air pollution that’s linked to multiple brain-related problems, with black, Hispanic and low-income students most likely to be exposed to a fug of harmful toxins at school, scientists and educators have warned.

The warnings come after widespread exposure to toxins was found in new research using EPA and census data to map out the air pollution exposure for nearly 90,000 public schools across the US.

“This could well be impacting an entire generation of our society,” said Dr Sara Grineski, an academic who has authored the first national study, published in the journal Environmental Research, on air pollution and schools.

Grineski and her University of Utah colleague Timothy Collins grouped schools according to their level of exposure to more than a dozen neurotoxins, including lead, mercury and cyanide compounds.

The research found that:

  • Only 728 schools achieved the safest possible score.
  • Five of the 10 worst polluted school counties have non-white populations of over 20%
  • The five worst polluted areas include New York, Chicago and Pittsburgh, as well as Jersey City and Camden in New Jersey. One teacher in Camden told the Guardian that heavy industry was “destroying our children”.

Cash-strapped authorities have routinely placed schools on the cheapest available land, which is often beside busy roads, factories or on previously contaminated sites. Teacher unions worry that the Trump administration’s enthusiasm for charter schools, championed by education secretary Betsy DeVos, will diminish federal intervention to reverse this.

The study found that pre-kindergarten children are attending higher risk schools than older students – a stark finding given the vulnerability of developing brains.

Pollution exposure is also drawn along racial lines. While black children make up 16% of all US public school students, more than a quarter of them attend the schools worst affected by air pollution. By contrast, white children comprise 52% of the public school system but only 28% of those attend the highest risk schools. This disparity remains even when the urban-rural divide is accounted for.

Schools with large numbers of students of colour are routinely located near major roads and other sources of pollution, with many also grappling with other hazards such as lead-laced drinking water and toxins buried beneath school buildings

Grineski said there were a range of consequences. “We’re only now realizing how toxins don’t just affect the lungs but influence things like emotional development, autism, ADHD and mental health,” she said. “Socially marginalized populations are getting the worst exposure. When you look at the pattern, it’s so pervasive that you have to call it an injustice and racism.”

The research is “important and is consistent with other localized information we’ve seen over the years,” according to Stephen Lester, science director of the Center for Health, Environment and Justice, who wasn’t involved in the study.

“Children are facing risks that will affect their ability to learn,” he said. “It’s a serious problem that needs a serious government response.”

As scientists have pieced together evidence showing the link between air toxins and neurological harm, American cities are still largely wedded to a legacy that has juxtaposed certain neighborhoods with heavy traffic and hulking industry.

Only a handful of states require that schools are not placed next to environmental hazards. In 2010, the EPA issued national guidelines on picking school locations but backed away from imposing mandatory buffer zones.

The guidelines were deemed voluntary “after a whole lot of pushback from various financial and political interests,” according to Lester, who was part of a group advising the EPA.

[…]

Scientific endeavour is uncovering a jumble of neurological reactions to air pollution, from early onset Alzheimers to schizophrenia. Much of this work is in its infancy, but scientists say there is well established evidence that children are far more susceptible to pollutants than adults, with potentially severe consequences for their development.

[…]

“Before, we might have labelled a kid with bad behaviour as just being a bad kid,” said Keith Benson, who taught history in the Camden school system before becoming the head of the local teacher’s union.

“Now we are thinking about it another way. There’s no telling how much potential has been lost because of environmental issues, how many hopes were stunted because these kids were not close to clear air and water.”

Air Pollution Exposure to Adults Over 60 is Found to Cancel Health Benefits of Exercise for Them

Reason #5533 for the world to use energy sources other than fossil fuels.

Exposure to air pollution on city streets is enough to counter the beneficial health effects of exercise in older adults, according to new research.

The findings, published in The Lancet, show that short term exposure to air pollution in built up areas like London’s busy Oxford Street can prevent the positive effects on the heart and lungs that can be gained from walking.

According to the research, led by Imperial College London and Duke University, the findings add to the growing body of evidence showing the negative impacts of urban air pollution on cardiovascular and respiratory health. The authors say the effects could potentially apply to other age groups as well and highlight the need for stricter air quality limits and greater access to green spaces.

Previous research has found that diesel exhaust fumes, particularly fine particulate matter air pollution, has been associated with an increased risk of cardiovascular disease and death, and can cause a worsening of diseases of the airways, such as asthma.

The latest study, funded by the British Heart Foundation, is the first to show the negative effects on healthy people, people with a chronic lung condition linked with smoking called Chronic Obstructive Pulmonary Disease (COPD), and those with coronary heart disease — which affects the supply of blood to the heart.

“These findings are important as for many people, such as the elderly or those with chronic disease, very often the only exercise they can do is to walk,” said senior author Fan Chung, Professor of Respiratory Medicine and Head of Experimental Studies Medicine at National Heart & Lung Institute at Imperial College London. “Our research suggests that we might advise older adults to walk in green spaces, away from built-up areas and pollution from traffic,” he added.

$240 Billion Worth of Yearly Costs for U.S. Weather Extremes Worsened by Climate Change

The economic costs will continue becoming worse until global heating is addressed vigorously. The cost of $240 billion is about a fifth of the U.S. government’s discretionary spending per year.

Weather extremes and air pollution from burning fossil fuels cost the United States $240 billion a year in the past decade, according to a report on Wednesday that urged President Donald Trump to do more to combat climate change.

This year is likely to be the most expensive on record with an estimated $300 billion in losses from Hurricanes Harvey, Irma and Maria and a spate of wildfires in western states in the past two months, it said.

“The evidence is undeniable: the more fossil fuels we burn, the faster the climate continues to change,” leading scientists wrote in the study published by the non-profit Universal Ecological Fund.

Costs to human health from air pollution caused by fossil fuels averaged $188 billion a year over the past decade, it estimated, while losses from weather extremes such as droughts, heat waves and floods averaged $52 billion.

Trump could curb the $240 billion costs, equivalent to 1.2 percent of U.S. gross domestic product, by revising his plans to promote the U.S. coal industry and to pull out of the 195-nation Paris climate agreement, it said.

 “We are not saying that all (weather extremes) are due to human activity, but these are the sort of events that seem to be increasing in intensity,” co-author Robert Watson, a former head of the U.N. panel of climate scientists, told Reuters.

Higher ocean temperatures, for instance, mean more moisture in the air that can fuel hurricanes.

And, in a sign of increasing risks, there were 92 extreme weather events that caused damage exceeding $1 billion in the United States in the decade to 2016, against 38 in the 1990s and 21 in the 1980s.

The combined cost of extreme weather and pollution from fossil fuels would climb to $360 billion a year in the next decade, the study said. Trump’s pro-coal policies could mean more air pollution, reversing recent improvements in air quality.

Last month, the U.S. Environmental Protection Agency accused scientists who linked record extreme rainfall from Tropical Storm Harvey to man-made climate change as trying to “politicize an ongoing tragedy.”

Wednesday’s study has been in the works for months, said co-author James McCarthy, professor of Oceanography at Harvard University. He said there was widening evidence that a shift from fossil fuels made economic sense.

“Why is Iowa, why is Oklahoma, why is Kansas, why is Texas investing in wind energy? Not because they are interested in sea level rise or ocean temperatures but because it’s economically sensible,” he told Reuters.