Air pollution is insidious. It doesn't respect borders and can travel thousands of miles. In fact, much of the smog experienced on the west coast of the U.S. is
the result of pollution produced in Asian countries — at times outpacing whatever decreases the U.S. achieves.1 The Lancet Commission on air pollution and health found:2
“Pollution is the largest environmental cause of disease and premature death in the world today. Diseases caused by pollution were responsible for an estimated 9 million premature deaths in 2015 — 16% of all deaths worldwide — three times more deaths than from AIDS, tuberculosis, and malaria combined and 15 times more than from all wars and other forms of violence.”
The World Health Organization used measurements of outdoor sources of air pollution from transport vehicles, industrial activity and coal-powered plants to determine that 92% of the global population is breathing polluted air.3 Many of the health effects are from fine particulate matter measuring less than 2.5 micrometers (PM2.5).
When most people think about the health issues associated with air pollution, respiratory conditions are the first to spring to mind, but your lungs are not the only system affected by air pollution.
And, when you consider the global statistics for air pollution, the total picture is really quite disturbing: Concentrations of PM2.5 exceeded 10 micrometers per meters cubed (µg/m3) for 91% of the world, higher than the annual mean set by WHO.4
But, global stats aside, did you know that pollution in your own backyard may be responsible for more health concerns than you’ve imagined?
Living Near Busy Roads Raises Risk of Neurological Diseases
A recent study published in Environmental Health has found a link between living close to a busy road and the development of non-Alzheimer’s dementia and Parkinson's disease.5
The researchers collected data from residents ages 45 to 84 in the Metro area of Vancouver, Canada. Their goal was to evaluate associations between living close to a busy road, exposure to air pollution and the effect of noise and green areas on the development of neurological conditions.
They defined closeness to a busy road as less than 50 meters (164 feet) from a major road, or less than 150 (492 feet) from a highway. According to Weiran Yuchi, one researcher on the study, the data confirmed associations between green space protection and air pollution hazards:6
“For the first time, we have confirmed a link between air pollution and traffic proximity with a higher risk of dementia, Parkinson's, Alzheimer's and MS at the population level.
The good news is that green spaces appear to have some protective effects in reducing the risk of developing one or more of these disorders. More research is needed, but our findings do suggest that urban planning efforts to increase accessibility to green spaces and to reduce motor vehicle traffic would be beneficial for neurological health.”
The researchers used data collected from 1994 to 1998 and from 1999 to 2003, and estimated air pollution exposure based on postal code data. During the follow-up period there were 13,170 people with dementia, 4,201 with Parkinson's, 1,277 with Alzheimer's Disease and 658 with multiple sclerosis. It appeared that those who lived near major roads unfortunately had an increased risk of dementia by 14% and of Parkinson’s disease by 7%.7
When the research data included green space like parks, it appeared to have a protective effect on health. Michael Brauer, Ph.D., another study researcher proposed the reason, saying:8
“For people who are exposed to a higher level of green space, they are more likely to be physically active and may also have more social interactions. There may even be benefits from just the visual aspects of vegetation.”
Incidence of Neurological Diseases on the Rise
The researchers were interested in the connections between air pollution and neurological diseases, as many of these conditions are leading causes of disability in high income countries, and the costs connected with these diseases are rising. Health conditions that fall under this umbrella term are disorders that affect the peripheral and central nervous systems.9
An analysis of data from the Global Burden of Diseases, Injuries, and Risk Factors Study (GBD) 2016 was done to estimate the burden of neurological disorders.10 The researchers used estimates of disability-adjusted life-years (DALYs) for several neurological diseases, including dementia, Parkinson's disease, stroke and motor neuron diseases.
The data were pulled from 195 countries. After analysis they found “neurological disorders were the leading cause of DALYs (276 million [95% UI 247–308]) and second leading cause of deaths (9.0 million [8.8–9.4]).” The researchers’ interpretation of the data was that:11
“Globally, the burden of neurological disorders, as measured by the absolute number of DALYs, continues to increase. As populations are growing and ageing, and the prevalence of major disabling neurological disorders steeply increases with age, governments will face increasing demand for treatment, rehabilitation, and support services for neurological disorders.”
The study results were also the subject of a 232-page report by the WHO12 in which they expanded on estimates and projections and the public health aspects of 10 neurological conditions, including risk factors, gaps in treatment and cost of care. They warn:
“The Global Burden of Disease study, the ongoing international collaborative project between WHO, the World Bank and the Harvard School of Public Health, has produced evidence that pinpoints neurological disorders as one of the greatest threats to public health.
A clear message emerges that unless immediate action is taken globally, the neurological burden is expected to become an even more serious and unmanageable problem in all countries.”
Just How Deadly Is Air Pollution?
Fine particulate matter (PM) from outdoor air pollution can also increase the risk of depression in children. One meta-analysis of 14 studies13 discovered that an “increase in ambient PM of 2.5 μm was strongly associated with increased depression risk in the general population,” They also found a “marginal risk of suicide.”
“We already know that air pollution is bad for people's health, with numerous physical health risks ranging from heart and lung disease to stroke and a higher risk of dementia. Here, we're showing that air pollution could be causing substantial harm to our mental health as well, making the case for cleaning up the air we breathe even more urgent.
We found quite consistent results across the studies we reviewed that analysed the relationship between long-term air pollution exposure and depression, even after adjustment for many other factors which could explain the association. The association seems to be similar in magnitude to those that have been found for some physical health impacts of particulate matter, such as all-cause mortality.”
As you might expect, once particulate matter has entered your body it doesn't just affect your mood, but can affect cognitive performance.16 In a report in PNAS, researchers found that cutting particulate matter in China could increase both verbal and math test scores in men as they age.
They wrote the damage that this kind of pollution causes may create an increased financial burden since seniors require cognitive ability to make decisions important to their future. But still, even though researchers have known there are systemwide effects from breathing air pollution, they admit the mechanism by which this happens is still not well-defined.
One unique, although small, study sought to begin answering this question. The data showed how air pollution may affect your blood vessels and heart muscle. Using human participants and animals, scientists evaluated how inhaled microscopic particles travel throughout the body in the bloodstream.17 The study method and results were well-described in a press release:18
“In the new study, 14 healthy volunteers, 12 surgical patients and several mouse models inhaled gold nanoparticles, which have been safely used in medical imaging and drug delivery. Soon after exposure, the nanoparticles were detected in blood and urine. Importantly, the nanoparticles appeared to preferentially accumulate at inflamed vascular sites, including carotid plaques in patients at risk of a stroke.”
The affinity to areas of the vascular system that were damaged or inflamed may help explain past research and data showing exposure to air pollution also increases your risk of vascular disease and heart disease.
Busy Roads Also Contribute to Pedestrian Deaths
The risk of disability and death from living near busy streets is not limited to air pollution. The Governors Highway Safety Association (GHSA)19 has found the number of deaths from car-pedestrian accidents has grown by 35% from 2008 to 2017.
However, the report also found the number of deaths from other traffic accidents went down 6%. The report links the rising number of fatal pedestrian accidents to such things as:20
- A greater number of light trucks and SUVs on the road
- The number of fatalities involving SUVs rising at a faster rate than those involving passenger cars, which are still involved in more fatalities than other vehicles
- A higher number of nighttime accidents
- An increase in population growth linked to an overall increase in the number of fatalities from one year to the next
- The growth of smartphone use, a source of distraction while walking
The largest number of accidents happened on local streets in 2017. Although smartphones are a distraction to drivers and pedestrians, the GHSA report was unable to make a definitive link between phones and accidents. They wrote that police investigators may not accurately capture distractions by smartphones in their reports.
Walking goes a long way toward reducing your risk of health conditions associated with inactivity. One of the best ways to reduce your risk of injury is to not use any device that distracts you from your surroundings. Here are several more ways to protect your safety:
Walk with reflective clothing at dusk and after
Put reflective strips on your bike — and your pet if they’re with you
Don’t assume a driver sees you; try to make eye contact with the driver
Carry ID with your emergency contact information
Let others know where you'll be going and when to expect you back
Stay in well-lit areas
Stay alert to your environment at all times
Walk facing oncoming traffic and stick to sidewalks when available
Keep the volume of your music down to hear traffic noise
Pollution Levels in Your Car May Rise to Dangerous Levels
While living near a busy street raises your chronic exposure to air pollution, driving on busy highways every day can also increase your vulnerability. In a study published in Environmental Science Processes and Impacts,21 research revealed how dangerous it is to ride in your car through heavy traffic.
The New York Times reported the average person commuted for 50 hours in 2015.22 To understand what this time in your vehicle means to your health, a study done in England may make it clear. In this study, data on air pollution inside cars was gathered in “a typical English town.” Researchers analyzed how changing the ventilation settings in the car air exchange system may change the concentration of PM1, PM2.5 and PM10 inside the vehicle.23
The cars drove in a loop over 6 kilometers (3.7 miles) during which they passed through 10 intersections. The data suggested car ventilation systems were more efficient at removing larger particulate matter and the amount of PM10 deposited in the lungs when the windows were open was “up to seven times that for pedestrians at the TIs [traffic intersections].” The researchers concluded:24
- The concentration of particulate matter in the car was affected by the rate of air exchange in the car
- The concentrations were up to 40% higher for PM10 and 16% higher for PM2.5 at intersections
- During stop-and-go traffic, the amount of particulate matter in the car was dependent on traffic speed
- During delayed conditions, intersections increased the amount of particulate matter in the car
- The highest reduction in particulate matter happened when the windows were closed, and the fan was switched to the off position
Based on these results, it’s recommended you roll up your windows and set the ventilation to recirculation when you’re in heavy traffic or stopping frequently at red lights. If you do that, though, it’s important to also remember newer cars are more airtight, so you may experience a buildup of carbon dioxide.
This may mean the car begins to feel “stuffy” and may affect cognitive performance while driving. To prevent this from happening, experts recommend you switch the ventilation to bring in air from outside for one to two minutes every 10 to 15 minutes to facilitate air exchange, while still minimizing over exposure to air pollution.25
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