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Air Pollution

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  • The smaller the diameter of the particle, the greater its risk of health damage becomes, as these can easily pass deep into your lungs, causing well-known damage to your heart and lungs, as well as to your brain function
  • Older people living in areas with 15 micrograms per cubic meter or more of fine particulate matter had higher error scores (by 1.5 times) than those living in areas with no more than 5 micrograms per cubic meter
  • “Fine” particulate matter is generally defined as particles that are 2.5 micrometers or less
  • Long-term exposure to particulate matter air pollution has also been associated with significantly faster cognitive decline, including in measures of memory and attention span, in older adults
  • The most effective way to improve your indoor air quality is to control or eliminate as many sources of pollution as you can first, and then use a high-quality air filter

Air Pollution Linked to Cognitive Decline in Later Years

July 03, 2014 | 28,301 views
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By Dr. Mercola

You’re probably aware that air pollution affects your heart and lungs, but what about your brain? Like most environmental toxicants, air pollution does not discriminate in its targets… it hits your entire body, with effects on everything from behavior to brain health.

Air pollution, for instance, has been found to have a negative impact on brain development, possibly by causing blood vessels to constrict or causing toxic buildup in your brain.1

A new study published in the Journal of Gerontology has also highlighted the risks of air pollution on cognitive function in older adults, with equally damaging repercussions.2

Fine Particulate Matter Air Pollution May Harm Cognitive Function

Particulate matter is air pollution made up of extremely small particles or liquid droplets. Typically, it’s composed of any number of toxicants, including organic chemicals, metals, soil, or dust. The smaller the diameter of the particle, the greater its risk of health damage becomes, as these can easily pass into your lungs, causing well-known damage to your heart and lungs.

“Fine” particulate matter is generally defined as particles that are 2.5 micrometers or less. These particles may come from smoke (such as forest fires) as well as gases emitted from power plants, industries, and, of course, automobiles. For comparison, the US Environmental Protection Agency (EPA) considers any particles that are 10 micrometers or less as a potential health concern.3

There is growing evidence that fine particulate matter poses a risk to brain health and development, so researchers set out to look at its impact in older adults (those aged 55 and older).

They measured air pollution levels in participants’ neighborhoods, and found the average concentrations of particulate matter smaller than 2.5 micrometers (PM2.5) were 13.8 micrograms per cubic meter – a level higher than the EPA’s air quality standard (which is 12 micrograms per cubic meter).

Then, they assessed cognitive function in comparison to pollution levels and found that those living in the most polluted areas had worse cognitive function. Specifically, those living in areas with 15 micrograms per cubic meter or more of PM2.5 had higher error scores (by 1.5 times) than those living in areas with no more than 5 micrograms per cubic meter. According to the study’s co-author:4

“…particulate matter may affect cognitive function in older adults by its harmful effects on the cardiovascular system – which is connected to the brain through blood vessels - and possibly by directly acting on the brain itself.”

Air Pollution Linked to Accelerated Memory Decline, Behavior Problems

It’s becoming increasingly clear that toxicants in the air you breathe may significantly impact your brain at many stages of life. In 2012, a study revealed that long-term exposure to particulate matter air pollution (at sizes ranging from 2.5-10 micrometers) were associated with significantly faster cognitive decline, including in measures of memory and attention span, in 70- to 81-year-old women.

These are levels typically experienced by many individuals in the US…5 At the other end of the age spectrum, a study found that children exposed to traffic-related air pollution before their first birthday had a higher risk of hyperactivity at the age of 7.6

The research suggests that air pollution may cause damage in both the early and late stages of life. One study even found that “neurodegenerative disorders such as Alzheimer's may begin early in life with air pollutants playing a crucial role.”7

Fine Particulate Matter Also Increases Your Risk of Heart Attack

According to a German study presented at the EuroPRevent 2013 congress in Rome, long-term exposure to fine particulate matter air pollution is associated with atherosclerosis, or damage-induced thickening of the arteries.8

The results showed that small particulate matter and proximity to major roads were associated with aortic calcification, and for every increase in particle volume up to 2.4 micrometers, calcification increased by nearly 21 percent.9

Fine particle matter is believed to increase your cardiovascular disease risk by causing an imbalance in your autonomic nervous system (ANS), the part of your brain that is intricately involved in regulating biological functions such as blood pressure, blood sugar levels, clotting, and viscosity. There are actually quite a few mechanisms by which air pollution harms both your heart and your brain.

For starters, it’s known that exposure to one type of air pollution, ozone, may trigger inflammation of your vascular system, increasing risk factors associated with heart disease. Ozone exposure has also been linked to a change in heart rate variability and a reduction in the ability of blood clots to dissolve, both of which can lead to heart problems10 and potentially stroke.

Additional research published in the journal PLOS Medicine showed that, on average, the thickness of the carotid artery increased by 0.014 millimeters per year after other risk factors such as smoking were accounted for.11

Those who had higher levels of exposure to fine particulate air pollution experienced thickening of the inner two layers of the carotid artery (which supplies blood to your head) quicker than those exposed to lower levels of pollution.

How Can You Escape Outdoor Air Pollution?

If you happen to live in a heavily polluted area, the best option is to move, but I realize that isn’t always a practical option. If you can’t move, pay attention to the Air Quality Index (AQI), released by the EPA to calculate five major air pollutants:

  • Ground-level ozone
  • Particulate matter
  • Carbon monoxide
  • Sulfur dioxide
  • Nitrogen dioxide

If the AQI in your area is high, it may be best to stay indoors as much as possible. At the very least, avoid exercising outdoors when air pollutants are high (such as during rush-hour traffic).

Your Indoor Air May Be Even More Polluted

The truth is, you can’t always escape outdoor air pollution, so it’s better to focus your attention on your immediate environment, which you have more, if not full, control over. Amazing as it sounds, indoor air can be 5 to 10 times more polluted than outdoors air!

This is because there's a lack of ventilation, so contaminants build up and stagnant air is re-circulated, further amplifying the problem. Common health problems that can be attributed to poor indoor air quality include:

Headaches Fatigue and lethargy
Depression Allergies
Poor concentration and forgetfulness Rashes
Stomach and digestive problems Neurological problems


The most effective way to improve your indoor air quality is to control or eliminate as many sources of pollution as you can first, before using any type of air purifier. This includes accounting for molds, tobacco smoke, volatile organic compounds from paints, aerosol sprays, and household cleaners, pesticides, phthalates from vinyl flooring and personal care products, pollutants from pressure-treated wood products, radon gas, and more (see tips below). The next step to take is free—simply open some windows. Of course, this can only take you so far, and works better if your outdoor air isn’t heavily polluted, but it's an important and simple step.

Next, since it is impossible to eliminate all air contaminants, one of the best things you can do is incorporate a high-quality air purifier. My recommendations for air purifiers have changed over the years, along with the changing technologies and newly emerging research. There are so many varieties of contaminants generated by today's toxic world that air purification manufacturers are in a constant race to keep up with them, so it pays to do your homework. At present, and after much careful review and study, I believe air purifiers using Photo Catalytic Oxidation (PCO) seem to be the best technology available.

Tips for Significantly Improving Your Air Quality

Aside from using an air purification system, there are a number of other steps you can take to take charge of your air quality and greatly reduce the amount of air pollutants generated in your home:

  • Vacuum your floors regularly using a HEPA filter vacuum cleaner or, even better, a central vacuum cleaner that can be retrofitted to your existing house if you don’t currently have one. Standard bag or bagless vacuum cleaners are another primary contributor to poor indoor air quality. A regular vacuum cleaner typically has about a 20-micron tolerance. Although that's tiny, far more microscopic particles flow right through the vacuum cleaner than it actually picks up! Beware of cheaper knock-offs that profess to have "HEPA-like" filters—get the real deal.
  • Increase ventilation by opening a few windows every day for 5 to 10 minutes, preferably on opposite sides of the house. This is important even in the extremes of summer and winter so you avoid pollution buildup.
  • Get some houseplants. Even NASA has found that plants markedly improve the air! For tips and guidelines, see my previous article “The 10 Best Pollution-Busting Houseplants.”
  • Take your shoes off as soon as you enter the house, and leave them by the door to prevent tracking in toxic particles.
  • Discourage or even better, forbid, tobacco smoking in or around your home.
  • Switch to non-toxic cleaning products (such as baking soda, hydrogen peroxide, and vinegar) and safer personal care products. Avoid aerosols. Look for VOC-free cleaners. Avoid commercial air fresheners and scented candles, which can outgas literally thousands of different chemicals into your breathing space.
  • Avoid powders. Talcum and other personal care powders can be problematic as they float and linger in the air after each use. Many powders are allergens due to their tiny size and can cause respiratory problems
  • Don't hang dry-cleaned clothing in your closet immediately. Hang them outside for a day or two. Better yet, see if there's an eco-friendly dry cleaner in your city that uses some of the newer dry cleaning technologies, such as liquid CO2.
  • Upgrade your furnace filters. Today, there are more elaborate filters that trap more of the particulates. Have your furnace and air conditioning ductwork and chimney cleaned regularly.
  • Avoid storing paints, adhesives, solvents, and other harsh chemicals in your house or in an attached garage.
  • Avoid using nonstick cookware, which can release toxins into the air when heated.
  • Ensure your combustion appliances are properly vented.
  • Make sure your house has proper drainage and its foundation is sealed properly to avoid mold formation. For more information about the health dangers of mold and how to address it, please see this previous interview with Dr. Jim Pearson.
  • The same principles apply to ventilation inside your car—especially if your car is new—and chemicals from plastics, solvents, carpet, and audio equipment add to the toxic mix in your car's cabin. That "new car smell" can contain up to 35 times the health limit for VOCs, "making its enjoyment akin to glue-sniffing."12

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