Could air pollution be damaging your mental health?

Another lovely day in east London. Image: Getty.

Between 1 and 8 January 2017, London breached its annual air pollution limits. In just a week, the city broke EU regulations that limit nitrogen dioxide (NO2) emissions, which are produced by diesel vehicles. It is a publishable, verifiable, undeniable scientific fact that this gas is connected to heart and breathing problems. The UK’s air is dirty, and it is prematurely killing us. But can it also make your life more difficult in the meantime?

DepressionanxietyAlzheimer’spoor academic performance – these are just some of the things that scientists have connected to air pollution in recent years. Research is relatively young, and it is dangerous to establish cause and effect too freely, but it now seems apparent that the smog affecting our bodies could also be affecting our brains.

“Our study found that those with higher exposures to fine particulate matter, a type of air pollution, were more likely to experience high anxiety symptom levels,” says Dr Melinda Power, a professor at George Washington University who warns against establishing causality too early. In 2015, Power published her research, which used data from 70,000 women in the Nurses’ Health Study who then filled out a survey on their anxiety levels. She discovered that fine particles in the air (which come from, among other things, cars and factories) were connected to increased anxiety levels, and that the more recent the exposure, the higher the level of anxiety experienced.

“As relatively little research has been done on the relationship between air pollution and mental health, further research is needed to confirm our findings,” she says, noting that women in more polluted areas may experience other stresses that caused their anxiety.  

When it comes to identifying a cause for the recent epidemic in mental health disorders, such as anxiety and depression, often simpler explanations get precedence in the media. The idea that social networks like Facebook “make us” depressed has been flying around for years. This is easy for individuals to identify as an affect on their mental health, if it is affecting them that way. But not many of us stop to consider how the invisible air around us might be affecting our mental health, and it is much harder to find any anecdotal evidence of whether this is the case. For more answers, we must turn to science’s most faithful research assistant: mice.

“We got into this research by accident,” says Dr Randy Nelson, a professor at the Ohio State University Wexner Medical Center. “I was walking across campus and saw a trailer that was being used to expose mice to particulate matter. The work was being directed by a cardiologist who had demonstrated that exposure to fine airborne particulate matter caused inflammation in the heart.

“It seemed reasonable to hypothesise that exposure to this type of air pollution would also cause inflammation in the brain and that is often associated with depression and cognitive impairments.”

Nelson and his team exposed mice to fine particle air pollution in the same high levels that are found in urban areas. They discovered that, after ten months, mice exposed to polluted air took longer to complete a maze task than mice exposed to filtered air. More incredibly, the “polluted” mice also exhibited depressive symptoms and “behaviour despair”, such as an unwillingness to swim when placed in water. Researchers at Duke University also found pregnant mice exposed to diesel exhaust had offspring who exhibited increased anxiety.

When I ask Nelson if rising levels of air pollution could be causing rising levels of depression, he says it is “possibly a contributing factor” and points towards other environmental factors – such as bright lights at night interrupting our circadian rhythms. Like Power, he feels that more research needs to be done before such wide-reaching conclusions can be drawn.

But just how much research will be enough to prompt us to act? In 2015, scientists at the University of Utah found a link between air pollution and suicide in middle-aged men. It is also already proven that air pollution affects our physical health, and Power notes that this, in turn, can affect us mentally. “Air pollution may be related to mental health, particularly anxiety, through effects on oxidative stress and systemic inflammation or through promotion or aggravation of chronic diseases,” she says. Put simply, being sick can make us depressed.


(Side note: according to the psychologist Dr Ken McLaughlin, the current “politics of fear” can also increase anxiety, so reading about air pollution also probably doesn’t help. Sorry about that.)

And yet while research about how air pollution affects mental health is in its infancy, there is significantly more information about the link between air pollution and cognitive health. Power has found that men with higher past exposures to traffic-related air pollution had worse cognitive functions. An extensive 2012 article by the American Psychological Association outlines the many studies in this area.

So where does that leave us? A spokesperson for the European Commission, which sets our air quality targets, says the World Health Organisation is now reviewing evidence about mental health, and new targets will take this into account. Power says more “big, high-quality, longitudinal studies are needed”, yet Andrea Lee, a healthy air campaigner for ClientEarth, says we need to act sooner rather than later. “As research continues in all of these areas, what is beyond doubt is that air pollution in the UK is above legal limits,” she says.

Whether they are linked or not, it now clear we are facing two public health emergencies that need more attention. Mental health disorders and air pollution can both prematurely rob us of our lives. Depression can feel like a black cloud that bears down on you from all angles, smothering your entire being. Coincidentally or not, so can smog.

Amelia Tait is a technology and digital culture writer at the New Statesman, where this article previously appeared.

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Here are the seven most extreme plants we’ve so far discovered

Artist's impression of Kepler-47. Image: NASA.

Scientists recently discovered the hottest planet ever found – with a surface temperature greater than some stars.

As the hunt for planets outside our own solar system continues, we have discovered many other worlds with extreme features. And the ongoing exploration of our own solar system has revealed some pretty weird contenders, too. Here are seven of the most extreme.

The hottest

How hot a planet gets depends primarily on how close it is to its host star – and on how hot that star burns. In our own solar system, Mercury is the closest planet to the sun at a mean distance of 57,910,000km. Temperatures on its dayside reach about 430°C, while the sun itself has a surface temperature of 5,500°C.

But stars more massive than the sun burn hotter. The star HD 195689 – also known as KELT-9 – is 2.5 times more massive than the sun and has a surface temperature of almost 10,000°C. Its planet, KELT-9b, is much closer to its host star than Mercury is to the sun.

Though we cannot measure the exact distance from afar, it circles its host star every 1.5 days (Mercury’s orbit takes 88 days). This results in a whopping 4300°C – which is hotter than many of the stars with a lower mass than our sun. The rocky planet Mercury would be a molten droplet of lava at this temperature. KELT-9b, however, is a Jupiter-type gas giant. It is shrivelling away as the molecules in its atmosphere are breaking down to their constituent atoms – and burning off.

The coldest

At a temperature of just 50 degrees above absolute zero – -223°C – OGLE-2005-BLG-390Lb snatches the title of the coldest planet. At about 5.5 times the Earth’s mass it is likely to be a rocky planet too. Though not too distant from its host star, at an orbit that would put it somewhere between Mars and Jupiter in our solar system, its host star is a low mass, cool star known as a red dwarf.

Freezing but Earth-like: ESO OGLE BLG Lb. Image: ESO/creative commons.

The planet is popularly referred to as Hoth in reference to an icy planet in the Star Wars franchise. Contrary to its fictional counterpart, however, it won’t be able to sustain much of an atmosphere (nor life, for that matter). This because most of its gases will be frozen solid – adding to the snow on the surface.

The biggest

If a planet can be as hot as a star, what then makes the difference between stars and planets? Stars are so much more massive than planets that they are ignited by fusion processes as a result of the huge gravitational forces in their cores. Common stars like our sun burn by fusing hydrogen into helium.

But there is a form of star called a brown dwarf, which are big enough to start some fusion processes but not large enough to sustain them. Planet DENIS-P J082303.1-491201 b with the equally unpronounceable alias 2MASS J08230313-4912012 b has 28.5 times the mass of Jupiter – making it the most massive planet listed in NASA’s exoplanet archive. It is so massive that it is debated whether it still is a planet (it would be a Jupiter-class gas giant) or whether it should actually be classified as a brown dwarf star. Ironically, its host star is a confirmed brown dwarf itself.

The smallest

Just slightly larger than our moon and smaller than Mercury, Kepler-37b is the smallest exoplanet yet discovered. A rocky world, it is closer to its host star than Mercury is to the sun. That means the planet is too hot to support liquid water and hence life on its surface.

The oldest

PSR B1620-26 b, at 12.7bn years, is the oldest known planet. A gas giant 2.5 times the mass of Jupiter it has been seemingly around forever. Our universe at 13.8bn years is only a billion years older.

Artist’s impression of the biggest planet known. Image: NASA and G. Bacon (STScI).

PSR B1620-26 b has two host stars rotating around each other – and it has outseen the lives of both. These are a neutron star and a white dwarf, which are what is left when a star has burned all its fuel and exploded in a supernova. However, as it formed so early in the universe’s history, it probably doesn’t have enough of the heavy elements such as carbon and oxygen (which formed later) needed for life to evolve.


The youngest

The planetary system V830 Tauri is only 2m years old. The host star has the same mass as our sun but twice the radius, which means it has not fully contracted into its final shape yet. The planet – a gas giant with three quarters the mass of Jupiter – is likewise probably still growing. That means it is acquiring more mass by frequently colliding with other planetary bodies like asteroids in its path – making it an unsafe place to be.

The worst weather

Because exoplanets are too far away for us to be able to observe any weather patterns we have to turn our eyes back to our solar system. If you have seen the giant swirling hurricanes photographed by the Juno spacecraft flying over Jupiter’s poles, the largest planet in our solar system is certainly a good contender.

However, the title goes to Venus. A planet the same size of Earth, it is shrouded in clouds of sulfuric acid.

The ConversationThe atmosphere moves around the planet much faster than the planet rotates, with winds reaching hurricane speeds of 360km/h. Double-eyed cyclones are sustained above each pole. Its atmosphere is almost 100 times denser than Earth’s and made up of over 95 per cent carbon dioxide.

The resulting greenhouse effect creates hellish temperatures of at least 462°C on the surface, which is actually hotter than Mercury. Though bone-dry and hostile to life, the heat may explain why Venus has fewer volcanoes than Earth.

Christian Schroeder is a lecturer in environmental science and planetary exploration at the University of Stirling.

This article was originally published on The Conversation. Read the original article.