Smog in our brains

By Kristen Weir

American Psychological Association 
July/August 2012, Vol 43, No. 7

Researchers are identifying startling connections between air pollution and decreased cognition and well-being.

That yellow haze of smog hovering over the skyline isn't just a stain on the view. It may also leave a mark on your mind.

Researchers have known since the 1970s that high levels of air pollution can harm both cardiovascular and respiratory health, increasing the risk of early death from heart and lung diseases. The effect of air pollution on cognition and mental well-being, however, has been less well understood. Now, evidence is mounting that dirty air is bad for your brain as well.

Over the past decade, researchers have found that high levels of air pollution may damage children's cognitive abilities, increase adults' risk of cognitive decline and possibly even contribute to depression.

"This should be taken seriously," says Paul Mohai, PhD, a professor in the University of Michigan's School of Natural Resources and the Environment who has studied the link between air pollution and academic performance in children. "I don't think the issue has gotten the visibility it deserves."     

      

Cognitive connections

Most research on air pollution has focused on a type of pollutant known as fine particulate matter. These tiny particles — 1/30th the width of a human hair — are spewed by power plants, factories, cars and trucks. Due to its known cardiovascular effects, particulate matter is one of six principal pollutants for which the Environmental Protection Agency (EPA) has established air quality standards.

It now seems likely that the harmful effects of particulate matter go beyond vascular damage. Jennifer Weuve, MPH, ScD, an assistant professor of internal medicine at Rush Medical College, found that older women who had been exposed to high levels of the pollutant experienced greater cognitive decline compared with other women their age (Archives of Internal Medicine, 2012). Weuve's team gathered data from the Nurses' Health Study Cognitive Cohort, a population that included more than 19,000 women across the United States, age 70 to 81. Using the women's address history, Weuve and her colleagues estimated their exposure to particulate matter over the previous seven to 14 years. The researchers found that long-term exposure to high levels of the pollution significantly worsened the women's cognitive decline, as measured by tests of cognitive skill.

Weuve and her colleagues investigated exposure to both fine particulate matter (the smallest particles, less than 2.5 micrometers in diameter) and coarse particulate matter (larger particles ranging from 2.5 to 10 micrometers in size).

"The conventional wisdom is that coarse particles aren't as important as fine particles" when it comes to human health, Weuve says. Previous studies in animals and human cadavers had shown that the smaller particles can more easily penetrate the body's defenses. "They can cross from the lung to the blood and, in some cases, travel up the axon of the olfactory nerve into the brain," she says. But Weuve's study held a surprise. She found that exposure to both fine and coarse particulate was associated with cognitive decline.

Weuve's results square with those of a similar study by Melinda Power, a doctoral candidate in epidemiology and environmental health at the Harvard School of Public Health. Power and her colleagues studied the link between black carbon — a type of particulate matter associated with diesel exhaust, a source of fine particles — and cognition in 680 older men in Boston (Environmental Health Perspectives, 2011). "Black carbon is essentially soot," Power says.

Power's team used black carbon exposure as a proxy for measuring overall traffic-related pollution. They estimated each man's black carbon exposure by cross-referencing their addresses with an established model that provides daily estimates of black carbon concentrations throughout the Boston area. Much like Weuve's results in older women, Power and colleagues found that men exposed to high levels of black carbon had reduced cognitive performance, equivalent to aging by about two years, as compared with men who'd had less black carbon exposure.

But while black carbon is a convenient marker of air pollution, it's too soon to say that it's what's causing the cognitive changes, Power says. "The problem is there are a lot of other things associated with traffic — noise, gases — so we can't say from this study that it's the particulate part of the air pollution that matters."

Still, the cumulative results of these studies suggest that air pollution deserves closer scrutiny as a risk factor for cognitive impairment and perhaps dementia.

"Many dementias are often preceded by a long period of cognitive decline. But we don't know very much about how to prevent or delay dementia," Weuve says. If it turns out that air pollution does contribute to cognitive decline and the onset of dementia, the finding could offer a tantalizing new way to think about preventing disease. "Air pollution is something that we can intervene on as a society at large, through technology, regulation and policy," she says.

Young minds

Research is also finding air-pollution-related harms to children's cognition. Shakira Franco Suglia, ScD, an assistant professor at Boston University's School of Public Health, and colleagues followed more than 200 Boston children from birth to an average age of 10. They found that kids exposed to greater levels of black carbon scored worse on tests of memory and verbal and nonverbal IQ (American Journal of Epidemiology, 2008).

More recently, Frederica Perera, DrPH, at the Columbia University Mailman School of Public Health, and colleagues followed children in New York City from before birth to age 6 or 7. They discovered that children who had been exposed to higher levels of urban air pollutants known as polycyclic aromatic hydrocarbons while in utero were more likely to experience attention problems and symptoms of anxiety and depression (Environmental Health Perspectives, 2012). These widespread chemicals are a byproduct of burning fossil fuels.

Meanwhile Mohai, at the University of Michigan, found that Michigan public schools located in areas with the highest industrial pollution levels had the lowest attendance rates and the greatest percentage of students who failed to meet state testing standards, even after controlling for socioeconomic differences and other confounding factors (Health Affairs, 2011). What's worse, the researchers analyzed the distribution of the state's public schools and found that nearly two-thirds were located in the more-polluted areas of their districts. Only about half of states have environmental quality policies for schools, Mohai says, "and those that do may not go far enough. More attention needs to be given to this issue."

Although Michigan and Massachusetts may experience areas of poor air quality, their pollution problems pale in comparison to those of Mexico City, for example. In a series of studies, Lilian Calderón-Garcidueñas, MD, PhD, a neuropathologist at the University of Montana and the National Institute of Pediatrics in Mexico City, has investigated the neurological effects of the city's infamous smog.

In early investigations, Calderón-Garcidueñas dissected the brains of dogs that had been exposed to air pollution of Mexico City and compared them with the brains of dogs from a less-polluted city. She found the Mexico City dogs' brains showed increased inflammation and pathology including amyloid plaques and neurofibrillary tangles, clumps of proteins that serve as a primary marker for Alzheimer's disease in humans (Toxicologic Pathology, 2003).

In follow-up research, Calderón-Garcidueñas turned her attention to Mexico's children. In one study, she examined 55 kids from Mexico City and 18 from the less-polluted city of Polotitlán. Magnetic resonance imagining scans revealed that the children exposed to urban pollution were significantly more likely to have brain inflammation and damaged tissue in the prefrontal cortex. Neuroinflammation, Calderón-Garcidueñas explains, disrupts the blood-brain barrier and is a key factor in many central nervous system disorders, including Alzheimer's disease and Parkinson's disease. Perhaps more troubling, though, the differences between the two groups of children weren't just anatomical. Compared with kids from cleaner Polotitlán, the Mexico City children scored lower on tests of memory, cognition and intelligence (Brain and Cognition, 2008).

Brain changes

It's becoming clearer that air pollution affects the brain, but plenty of questions remain. Randy Nelson, PhD, a professor of neuroscience at the Ohio State University, is using mouse studies to find some answers. With his doctoral student Laura Fonken and colleagues, he exposed mice to high levels of fine particulate air pollution five times a week, eight hours a day, to mimic the exposure a human commuter might receive if he or she lived in the suburbs and worked in a smoggy city (Molecular Psychiatry, 2011). After 10 months, they found that the mice that had been exposed to polluted air took longer to learn a maze task and made more mistakes than mice that had not breathed in the pollution.

Nelson also found that the pollutant-exposed mice showed signs of the rodent equivalent of depression. Mice said to express depressive-like symptoms give up swimming more quickly in a forced swim test and stop sipping sugar water that they normally find attractive. Both behaviors can be reversed with antidepressants. Nelson found that mice exposed to the polluted air scored higher on tests of depressive-like responses.

To find out more about the underlying cause of those behavioral changes, Nelson compared the brains of mice that had been exposed to dirty air with brains of mice that hadn't. He found a number of striking differences. For starters, mice exposed to particulate matter had increased levels of cytokines in the brain. (Cytokines are cell-signaling molecules that regulate the body's inflammatory response.) That wasn't entirely surprising, since previous studies investigating the cardiovascular effects of air pollution on mice had found widespread bodily inflammation in mice exposed to the pollution.

More surprisingly, Nelson also discovered physical changes to the nerve cells in the mouse hippocampus, a region known to play a role in spatial memory. Exposed mice had fewer spines on the tips of the neurons in this brain region. "Those [spines] form the connections to other cells," Nelson says. "So you have less dendritic complexity, and that's usually correlated with a poorer memory."

The changes are alarming and surprising, he says. "I never thought we'd actually see changes in brain structure."

Nelson's mice experienced quite high levels of pollution, on par with those seen in places such as Mexico City and Beijing, which rank higher on the pollution scale than U.S. cities. It's not yet clear whether the same changes would occur in mice exposed to pollution levels more typical of American cities. Another limitation, he notes, is that the animals in his study were genetically identical. Nelson says he'd like to see similar studies of wild-type mice to help tease out whether genetic differences might make some people more or less vulnerable to the effects of pollution. "I would suspect there are people who are wildly susceptible to this and people who are less so, or not at all," he says.

Few studies have investigated connections between depression and air pollution, but Nelson's wasn't the first. A study by Portuguese researchers explored the relationship between psychological health and living in industrial areas. They found that people who lived in areas associated with greater levels of air pollution scored higher on tests of anxiety and depression (Journal of Environmental Psychology, 2011).

Back in Ohio, Nelson plans to study how much — or how little — pollution is necessary to cause changes in the brain and behavior. He's also beginning to look at the effects of air pollution on pregnant mice and their offspring. Though more research is needed to fully understand how dirty air impairs the brain, he says, the picture that's emerging suggests reason for concern.

In the United States, the Environmental Protection Agency reviews the scientific basis for particulate matter standards every five years or so, and completed its last review in 2009.

To date, the EPA hasn't factored psychological research into their standards assessments, but that could change, according to a statement the EPA provided to the Monitor. "Additional research is necessary to assess the impact of ambient air pollutants on central nervous system function, such as cognitive processes, especially during critical windows of brain development. To this end, as the number of … studies continue to increase and add to the weight of overall evidence, future National Ambient Air Quality Standards assessments will again assess and address the adequacy of existing standards."

In the meantime, says Weuve, there's not much people can do to protect themselves, short of wearing special masks, installing special filtration systems in their homes and offices or moving to cities with less airborne pollution. "Ultimately, we're at the mercy of policy," she says.

The good news, Nelson says, is that the mental and cognitive effects of air pollution are finally beginning to receive attention from the mental health research community. "We sort of forget about these environmental insults," says Nelson. "Maybe we shouldn't."

The World According to Monsanto

Pollution, Corruption, and the Control of the World's Food Supply

A film (2008) by: Marie-Monique Robin 

Dr. Vandana Shiva, Indian environmental activist and anti-globalization author: “There's nothing they are leaving untouched: the mustard, the okra, the bringe oil, the rice, the cauliflower. Once they have established the norm: that seed can be owned as their property, royalties can be collected. We will depend on them for every seed we grow of every crop we grow. If they control seed, they control food, they know it – it's strategic. It's more powerful than bombs. It's more powerful than guns. This is the best way to control the populations of the world.”

The story starts in the White House, where Monsanto often got its way by exerting disproportionate influence over policymakers via the “revolving door”. One example is Michael Taylor, who worked for Monsanto as an attorney before being appointed as deputy commissioner of the US Food and Drug Administration (FDA) in 1991. While at the FDA, the authority that deals with all US food approvals, Taylor made crucial decisions that led to the approval of GE foods and crops. Then he returned to Monsanto, becoming the company’s vice president for public policy.

Thanks to these intimate links between Monsanto and government agencies, the US adopted GE foods and crops without proper testing, without consumer labeling and in spite of serious questions hanging over their safety. Not coincidentally, Monsanto supplies 90 percent of the GE seeds used by the US market.

Monsanto’s long arm stretched so far that, in the early nineties, the US Food and Drugs Agency even ignored warnings of their own scientists, who were cautioning that GE crops could cause negative health effects. Other tactics the company uses to stifle concerns about their products include misleading advertising, bribery and concealing scientific evidence.

More on Monsanto:

- Thousands march against GMO's, Monsanto across Canada 
- March against Monsanto, May 24, 2014
- Huffington Post, Monsanto 

Earth at 350

By: Bill McKibben

Even for Americans, constitutionally convinced that there will always be a second act, and a third, and a do-over after that, and, if necessary, a little public repentance and forgiveness and a Brand New Start--even for us, the world looks a little Terminal right now.

It's not just the economy. We've gone through swoons before. It's that gas at $4 a gallon means we're running out, at least of the cheap stuff that built our sprawling society. It's that when we try to turn corn into gas, it sends the price of a loaf of bread shooting upwards and starts food riots on three continents. It's that everything is so inextricably tied together. It's that, all of a sudden, those grim Club of Rome types who, way back in the 1970s, went on and on about the "limits to growth" suddenly seem... how best to put it, right.

All of a sudden it isn't morning in America, it's dusk on planet Earth.

There's a number--a new number--that makes this point most powerfully. It may now be the most important number on Earth: 350. As in parts per million (ppm) of carbon dioxide in the atmosphere.

A few weeks ago, our foremost climatologist, NASA's Jim Hansen, submitted a paper to Science magazine with several co-authors. The abstract attached to it argued--and I have never read stronger language in a scientific paper--"if humanity wishes to preserve a planet similar to that on which civilization developed and to which life on earth is adapted, paleoclimate evidence and ongoing climate change suggest that CO₂ will need to be reduced from its current 385 ppm to at most 350 ppm." Hansen cites six irreversible tipping points--massive sea level rise and huge changes in rainfall patterns, among them--that we'll pass if we don't get back down to 350 soon; and the first of them, judging by last summer's insane melt of Arctic ice, may already be behind us.

So it's a tough diagnosis. It's like the doctor telling you that your cholesterol is way too high, and if you don't bring it down right away, you're going to have a stroke. So you take the pill, you swear off the cheese, and, if you're lucky, you get back into the safety zone before the coronary. It's like watching the tachometer edge into the red zone and knowing that you need to take your foot off the gas before you hear that clunk up front.
 

In this case, though, it's worse than that because we're not taking the pill and we are stomping on the gas--hard. Instead of slowing down, we're pouring on the coal, quite literally. Two weeks ago came the news that atmospheric carbon dioxide had jumped 2.4 parts per million last year--two decades ago, it was going up barely half that fast.

And suddenly, the news arrives that the amount of methane, another potent greenhouse gas, accumulating in the atmosphere, has unexpectedly begun to soar as well. Apparently, we've managed to warm the far north enough to start melting huge patches of permafrost and massive quantities of methane trapped beneath it have begun to bubble forth.

And don't forget: China is building more power plants, India is pioneering the $2,500 car, and Americans are converting to TVs the size of windshields that suck juice ever faster.

Here's the thing. Hansen didn't just say that, if we didn't act, there was trouble coming; or, if we didn't yet know what was best for us, we'd certainly be better off below 350 ppm of carbon dioxide in the atmosphere. His phrase was: "...if we wish to preserve a planet similar to that on which civilization developed." A planet with billions of people living near those oh-so- floodable coastlines. A planet with ever more vulnerable forests. (A beetle, encouraged by warmer temperatures, has already managed to kill ten times more trees this year than in any previous infestation across the northern reaches of Canada. This means far more carbon heading for the atmosphere, and apparently dooms Canada's efforts to comply with the Kyoto Protocol, already in doubt because of its decision to start producing oil for the US from Alberta's tar sands.)

We're the ones who kicked off the warming; now, the planet is starting to take over the job. Melt all that Arctic ice, for instance, and suddenly the nice white shield that reflected 80 percent of incoming solar radiation back into space has turned to blue water that absorbs 80 percent of the sun's heat. Such feedbacks are beyond history, though not in the sense that Francis Fukuyama had in mind.

And we have, at best, a few years to short-circuit them--to reverse course. Here's the Indian scientist and economist Rajendra Pachauri, who accepted the Nobel Prize on behalf of the Intergovernmental Panel on Climate Change last year (and, by the way, got his job when the Bush Administration, at the behest of Exxon Mobil, forced out his predecessor): "If there's no action before 2012, that's too late. What we do in the next two to three years will determine our future. This is the defining moment."

In the next two or three years, the nations of the world are supposed to be negotiating a successor treaty to the Kyoto Accord. When December 2009 rolls around, heads of state are supposed to converge on Copenhagen to sign a treaty--a treaty that would go into effect at the last plausible moment to heed the most basic and crucial of limits on atmospheric CO₂.

If we did everything right, says Hansen, we could see carbon emissions start to fall fairly rapidly and the oceans begin to pull some of that CO₂ out of the atmosphere. Before the century was out we might even be on track back to 350. We might stop just short of some of those tipping points, like the Road Runner screeching to a halt at the very edge of the cliff.

More likely, though, we're the Coyote--because "doing everything right" means that political systems around the world would have to take enormous and painful steps right away. It means no more new coal-fired power plants anywhere, and plans to quickly close the ones already in operation. (Coal-fired power plants operating the way they're supposed to are, in global warming terms, as dangerous as nuclear plants melting down.) It means making car factories turn out efficient hybrids next year, just the way we made them turn out tanks in six months at the start of World War II. It means making trains an absolute priority and planes a taboo.

It means making every decision wisely because we have so little time and so little money, at least relative to the task at hand. And hardest of all, it means the rich countries of the world sharing resources and technology freely with the poorest ones, so that they can develop dignified lives without burning their cheap coal.

That's possible--we launched a Marshall Plan once, and we could do it again, this time in relation to carbon. But in a month when the President has, once more, urged us to drill in the Arctic National Wildlife Refuge, that seems unlikely. In a month when the alluring phrase "gas tax holiday" has danced into our vocabulary, it's hard to see (though it was encouraging to see that Clinton's gambit didn't sway many voters). And if it's hard to imagine sacrifice here, imagine China, where people produce a quarter as much carbon apiece as we do.

Still, as long as it's not impossible, we've got a duty to try. In fact, it's about the most obvious duty humans have ever faced.

A few of us have just launched a new campaign, 350.org. Its only goal is to spread this number around the world in the next eighteen months, via art and music and ruckuses of all kinds, in the hope that it will push those post-Kyoto negotiations in the direction of reality.

After all, those talks are our last chance; you just can't do this one light bulb at a time. And if this 350.org campaign is a Hail Mary pass, well, sometimes those passes get caught.

We do have one thing going for us: this new tool the web, which at least allows you to imagine something like a grassroots global effort. If the Internet was built for anything, it was built for sharing this number, for making people understand that "350" stands for a kind of safety, a kind of possibility, a kind of future.

Hansen's words were well-chosen: "a planet similar to that on which civilization developed." People will doubtless survive on a non-350 planet, but those who do will be so preoccupied, coping with the endless unintended consequences of an overheated planet, that civilization may not.

Civilization is what grows up in the margins of leisure and security provided by a workable relationship with the natural world. That margin won't exist, at least not for long, this side of 350. That's the limit we face.

From The Nation, May 12, 2008.