Pollution atmosphérique : plus de 80 % des zones urbaines sont exposées à des niveaux dangereux
The Air You Breathe Can Kill You
"More than 80 percent of inhabitants of urban areas are exposed to unsafe levels of air pollution,” Stephen Hawking June 2016
As you will see below, things have gotten much worse.
Healthy adults are facing previously unsuspected threats from air pollution. Tiny particles can zoom through human lungs up to two times faster and penetrate more deeply than assumed before, a University of Delaware scientist says.
Children and the elderly are at even greater risk. "Smog kills perhaps partly because pollutant particles are so deeply deposited in our airways," says Anthony Wexler, a professor of mechanical engineering at the University of Delaware.
Scientists from around the world gathered in Atlanta to determine the best ways to measure this fine particulate matter that is polluting the nation's air, particularly in large urban areas. Atlanta's air pollution problems have halted several new highway construction projects that officials feared would increase already dangerous city smog levels.
Particulate matter, which is federally regulated, is created by the burning of coal and oil. Numerous studies link it to serious health problems. Fine particulate matter, called PM 2.5 because it is less than 2.5 microns in diameter - about 30 times smaller than the diameter of a human hair, includes soot, dust, aerosols, metals, and sulfates. These particles emitted by vehicles, factories, and industrial facilities contribute to the smog so common in American cities.
In the first of two studies initiated by the U.S. Environmental Protection Agency (EPA), about 60 scientists have converged at an Atlanta air quality research facility owned by Georgia Power. Scientists began measuring PM 2.5 around the clock at 7:00 am August 3 and will continue through 7:00 am September 1.
"We are trying to determine how to measure the concentration and composition of fine particulate matter in the atmosphere and the types of instruments best suited to do that," said Dr. William Chameides, a professor in the Georgia Institute of Technology's School of Earth and Atmospheric Sciences and head of the study. "We need to do this to understand the health effects and the sources, and to monitor compliance with EPA standards.”
" Smog causes problems in cities across the U.S., sometimes in hard to predict locales. In the nation's smog capital, Los Angeles residents are now enjoying one of their least polluted summers ever. The Los Angeles region has made it to mid-August without suffering a single full-scale smog alert - the first time that has happened since officials began tracking air quality.
Texas is promoting carpools to help combat air pollution. But in east Texas and along the Eastern Seaboard, residents are coping with some of the worst smog seasons on record. Texas City, near Galveston, Texas, has recorded the highest one-hour concentration of urban ozone so far this summer.
On August 6, the town had 0.206 parts per million of particulate matter, the equivalent of a Stage 1 smog alert. Today, the Dallas/Fort Worth area declared an Ozone Alert Action Day, warning of dangerous levels of air pollutants.
Air pollution may be even more dangerous than experts have suspected. A study by Wexler and Ramesh Sarangapani, expected to appear in the next "Journal of Aerosol Science," reveals how PM 2.5 particles penetrate buildings and people's airways more quickly and deeply than previously known.
"As people breathe," Wexler explains, "a clump of fine particles called a bolus will rapidly disperse throughout the lungs. At the terminal alveoli - little sacks at the end of each respiratory branch, where oxygen and carbon dioxide trade places with blood - these particles take up water and expand, much like a sponge, because of gyroscopic effects."
Mathematical models of these physical events - dispersion and hygroscopic expansion - suggest that "the smallest particles can sometimes penetrate almost two times farther into airways than we had suspected," Wexler says. That happens because the air in the center of a lung tube flows faster than the surrounding stream, Wexler explains.
Particle-laden air mixes with clean air at each intersection of the respiratory branches. All that secondary mixing "dramatically speeds the movement of these fine particles through the respiratory system," Wexler reports. The next step, Sarangapani says, is to further investigate why fine particles can be toxic to the lungs.
"With the current amount of knowledge available to us," he says, "I think that the EPA's current standards are a reasonable response. But, additional research is needed to identify the precise mechanisms involved in particulate toxicity." Professor Anthony Wexler calls air pollution a fast and invisible threat.
In 1997, the EPA set a new, tighter standard for PM 2.5, in response to studies associating exposure to air pollution with serious health problems. But trucking associations and other industry groups have challenged the new standards in federal court, preventing them from being implemented.
Earlier, two judges of a three-judge panel ruled that the new PM 2.5 standard was unconstitutional. The panel did not challenge the science on which the new standard is based and in fact, said there was ample scientific support for the new standard.
The Department of Justice is appealing the ruling. Health effects of smog include increased hospital admissions and emergency room visits, increased respiratory disease, decreased lung function, and changes in respiratory tract defense mechanisms. "Tens of thousands of elderly people die prematurely each year from exposure to ambient levels of fine particles," according to the EPA.
Because children breathe 50 percent more air per pound of body weight, compared to adults, they are more susceptible, especially if they suffer from asthma. Even adults can die from air pollution exposure, because of the way the particles act in the lungs. See more about this in Buildings and Oxygen Levels.
You catch more fish with a bigger net, move more dirt with a bigger shovel, grab more oxygen with larger, stronger lungs. While you are attending to changing your environment I strongly suggest that you develop your breathing to as good as it can get to help offset the damage from pollution and give yourself more energy and clarity to make sure that pollution goes away and stays away.