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Luchtvervuiling en geheugenverlies, hartaanval en beroerte*
Uit drie studies blijkt dat luchtvervuiling zorgt voor geheugenverlies en de kans op een hartaanval en beroerte duidelijk kan verhogen. De lucht in een drukke stad of vlakbij een drukke weg bevat veel toxische stoffen zoals ozon, koolmonoxide, stikstofdioxide, zwaveldioxide, fijnstof en ultra fijnstof. Uit de eerste studie, een analyse van 34 eerdere studies, blijkt dat al bij zeven dagen blootstelling aan vuile lucht de kans op een hartaanval duidelijk vergroot wordt. Uit een tweede studie waarbij 1.700 patiënten 10 jaar lang gevolgd werden blijkt dat op dagen als de luchtvervuiling door fijnstof een piek vertoont de kans op een beroerte 34% groter is. In de derde studie onder ruim 19.000 vrouwen, zeventigjarige die 14 jaar lang gevolgd werden blijkt luchtvervuiling een duidelijke achteruitgang te geven in het geheugen- en denkvermogen. In het ergste geval waren de vaardigheden 2 jaar sneller achteruit gegaan dan normaal. Volgens de onderzoekers merkt een individueel persoon dat verschil niet, doch op een hele bevolking zou schonere lucht kunnen leiden tot minder gevallen van dementie.
Short-Term Exposure to Most Major Air Pollutants Associated With Increased Risk of Heart Attack
Short-term exposure (for up to 7 days) to all major air pollutants, with the exception of ozone, is significantly associated with an increased risk of heart attack, according to a review and meta-analysis of previous studies appearing in the JAMA.
The potentially harmful effect of episodes of high air pollution on health has been suspected for more than 50 years. "In industrialized countries, cardiovascular disease is the leading cause of mortality and is associated with significant morbidity. These countries have high pollution levels. Since the 1990s, many epidemiological studies have demonstrated associations between air pollution levels and human health in terms of hospital admissions and overall mortality, including respiratory or cardiovascular mortality. However, the association between air pollution and near-term risk of myocardial infarction [MI; heart attack] remains controversial. Some studies have shown an association, while other studies have found either no association or association only for selected pollutants," according to background information in the article.
Hazrije Mustafic, M.D., M.P.H., of the University Paris Descartes, INSERM Unit 970, Paris, and colleagues conducted a systematic review and meta-analysis to examine the association between short-term exposure to air pollutants and the risk of heart attack, and to quantify these associations. The major air pollutants included in the analysis were ozone, carbon monoxide, nitrogen dioxide, sulfur dioxide, and particulate matter (PM) with an aerodynamic diameter of 10 μm (micrometers; PM10) or less and those 2.5 micrometers (PM2.5) or less.
The researchers conducted a search of the medical literature and identified 34 studies that met criteria for inclusion in the analysis, which indicated associations of statistical significance between all analyzed air pollutants and heart attack risk, with the exception of ozone. The subgroup analysis, based on study quality, yielded results comparable with those from the overall analysis.
The authors suggest a number of possible mechanisms for the associations found. "The first potential mechanism is inflammation. Studies have shown that levels of inflammatory markers such as C-reactive protein are higher as a result of exposure to air pollution. The second potential mechanism is abnormal regulation of the cardiac autonomic system. Several observational studies have linked high levels of air pollution with increased heart rate and decreased heart rate variability. The third possible mechanism is an increase in blood viscosity as a result of air pollution. This association can promote thrombus [blood clot] formation, accelerate the progression of atherosclerosis, and weaken the stability of atherosclerotic plaques."
The researchers acknowledge that the magnitude of association found in this study is relatively small compared with those of classic heart attack risk factors, such as smoking, hypertension, or diabetes. "Nevertheless, the population attributable fractions of each pollutant is not negligible because the majority of the population, including young and disabled patients, is exposed to air pollution, particularly in urban settings, and thus an improvement in air quality could have a significant effect on public health."
"In conclusion, our meta-analysis is the first to our knowledge to evaluate the quality and magnitude of associations between short-term exposure to major air pollutants and the risk of MI," the authors write. "Further research is needed to determine whether effective interventions that improve air quality are associated with a decreased incidence of MI."

Even Moderate Air Pollution Can Raise Stroke Risks
Air pollution, even at levels generally considered safe by federal regulations, increases the risk of stroke by 34 percent, Beth Israel Deaconess Medical Center researchers have found.
Writing in the Archives of Internal Medicine, researchers who studied more than 1,700 stroke patients in the Boston area over a 10-year period found exposure to ambient fine particulate matter, generally from vehicle traffic, was associated with a significantly higher risk of ischemic strokes on days when the EPA's air quality index for particulate matter was yellow instead of green.
Researchers focused on particles with a diameter of 2.5 millionths of a meter, referred to as PM2.5. These particles come from a variety of sources, including power plants, factories, trucks and automobiles and the burning of wood. They can travel deeply into the lungs and have been associated in other studies with increased numbers of hospital visits for cardiovascular diseases such as heart attacks.
"The link between increased stroke risk and these particulates can be observed within hours of exposure and are most strongly associated with pollution from local or transported traffic emissions," says Murray A. Mittleman, MD, DrPH, the study's senior author, a physician in the CardioVascular Institute at Beth Israel Deaconess Medical Center and an Associate Professor of Medicine at Harvard Medical School. "Any proposed changes in regulated pollution levels must consider the impact of lower levels on public health."
"Considering that almost everyone is exposed to air pollution and is at risk for stroke, that's actually a pretty large effect," adds Gregory Wellenius, ScD, the study's lead author and an Assistant Professor of Community Health at Brown University.
Researchers analyzed the medical records of more than 1,700 patients who went to the hospital for treatment of confirmed strokes between 1999 and 2008. They matched the onset of stroke symptoms in each patient to hourly measurements of particulate air pollution taken at the nearby Harvard School of Public Health's environmental monitoring station.
The team was able to estimate the hour the stroke symptoms first occurred, rather than relying on the more coarse measure of when patients were admitted to the hospital. They also included only strokes confirmed by attending neurologists, rather than relying on more vague insurance billing codes.
Meanwhile, Harvard's hourly measurements of pollution within 13 miles of 90 percent of the stroke patients' homes allowed for close matching in time of exposure and stroke onset.
"We think that this study is novel in that it has high-quality data on both air pollution exposure and stroke diagnosis," Wellenius says.
The team was able to calculate that the peak risk to patients from pollution exposure occurs 12-14 hours before a stroke. That information may be useful to researchers who want to trace how PM2.5 might be working in the body to increase the likelihood of stroke.
They also found that black carbon and nitrogen dioxide, two pollutants associated with vehicle traffic, were closely linked with stroke risk, suggesting that pollution from cars and trucks may be particularly important.
Stroke is a leading cause of long-term disability and the third leading cause of death in the United States. An estimated 795,000 Americans suffer a new or recurrent stroke every year, resulting in more than 135,000 deaths and 829,000 hospital admissions.
The finding that days of moderate air quality substantially elevate stroke risk compared to days of good air quality suggest that the Environmental Protection Agency may need to strengthen the language it uses to describe the health consequences of moderate air quality, researchers say.
"In partnership with NIEHS, EPA funded this research advancing our understanding of air pollution and health effects," said Dan Costa, ScD, DABT, Interim National Program Director for Air Climate & Energy Research in U.S. Environmental Protection Agency Office of Research and Development Research.
"In 2009, EPA published an Integrated Science Assessment concluding a causal relationship exists between PM2.5 and cardiovascular impacts, including strokes. Dr. Wellenius and colleagues' study is the first to show that the onset of stroke can occur with less than a day's exposure to fine PM. Highly relevant research such as this informs the PM2.5 standards and protects human health."
Researchers estimate reducing PM2.5 pollution by about 20 percent could have prevented 6,100 of the 184,000 stroke hospitalizations in the northeastern United States in 2007.
While researchers acknowledge results need to be replicated in other cities, they note that Boston is considered to have relatively clean air.
"The levels of PM2.5 in Boston are lower than those seen in many in other parts of the country, yet we still find that within these moderate levels the risk of stroke is higher on days with more particles in the air," Mittleman says.
In addition to Wellenius and Mittleman, co-authors include Mary R. Burger, MD, and Gottfried Schlaug, MD, MPH of BIDMC, Brent A. Coull. PhD, Joel Schwartz, PhD, Helen Suh, ScD, Petros Koutrakis, PhD, of the Harvard School of Public Health and Diane R. Gold, MD, of Brigham an d Women's Hospital.
The study was supported by National Institute of Environmental Health Sciences and the Environmental Protection Agency. One or more of the authors are currently receiving or have received funding from the Health Effects Institute of Boston; the Electric Power Research Institute of Palo Alto, CA; the EPA and the National Institutes of Health.

Air Pollution Linked to Cognitive Decline in Women
A large, prospective study led by a researcher at Rush University Medical Center indicates that chronic exposure to particulate air pollution may accelerate cognitive decline in older adults. The results of the study will be published in the Archives of Internal Medicine, one of the JAMA/Archives journals.
In the study, women who were exposed to higher levels of ambient particulate matter (PM) over the long term experienced more decline in their cognitive functioning over a four-year period. Higher levels of long-term exposure to both coarse PM (PM2.5-10) and fine PM (PM2.5) were associated with significantly faster cognitive decline.
PM air pollution consists of small particles suspended in the air. Particles that are less than 2.5 microns in diameter, which is 1/30th the width of human hair, are called fine PM and particles larger than 2.5-10 microns is called coarse PM.
These associations were present at levels of PM exposure typical in many areas of the United States.
There are few recent studies that analyze air pollution and cognitive function in older adults, but this is the first study to examine change in cognitive function over a period of time and whether exposure to the size of particulate matter is important.
Jennifer Weuve, MPH., ScD, assistant professor of the Rush Institute of Healthy Aging and the principal investigator of the study, along with her colleagues, evaluated air pollution, both coarse and fine, in relation to cognitive decline in older women using a study population from the Nurses' Health Study Cognitive Cohort, which included 19,409 U.S. women ages 70 to 81 for a 14-year period going back as far as 1988.
"Our study explored chronic exposure to particulate air pollution in relation to decline in cognitive functioning among older women," said Weuve. "Very is little known about the role of particulate matter exposure and its association with cognitive decline."
Exposure to particulate air pollution is associated with cardiovascular risk, which itself may play a role in causing or accelerating cognitive decline.
"Unlike other factors that may be involved in dementia such as diet and physical activity, air pollution is something we can intervene on as a society at large through policy, regulation and technology," said Weuve.
"Therefore, if our findings are confirmed in other research, air pollution reduction is a potential means for reducing the future population burden of age-related cognitive decline, and eventually, dementia," said Weuve.
The studies were supported by grants from the National Institute of Environmental Health Sciences, National Cancer Institute and the U.S. Environmental Protection Agency.
Jennifer Weuve, MPH, ScD, is an assistant professor of internal medicine at the Rush Medical College and the Rush Institute for Healthy Aging, Rush University Medical Center.
Co-authors of the study include Robin Puett, MPH, PhD of University of Maryland School of Public Health, Joel Schwartz, PhD, and Francine Laden, MS, ScD, and Francine Grodstein, ScD, of the Harvard School of Public Health, and Jeff Yanosky, MS, ScD of Penn State University College of Medicine. (Maart 2012)