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Seven years ago, an Environmental Protection Agency statistician stunned researchers studying the effects of air pollution on health when he reported analyses indicating that as many as 60, 000 U. S. residents die each year from breathing federally allowed concentrations of airborne dust. This and subsequent studies figured prominently in EPA's decision last year to ratchet down the permitted concentration of breathable particles in urban air -- and in human airways.
At the time, many industrialists argued that they shouldn't have to pay for better pollution control because science had yet to suggest a plausible biological mechanism by which breathing low concentrations of urban dust might sicken or kill people.
Now, scientists at the University of Texas Houston Health Science Center describe how they uncovered what they think may be one of the basic elements of that toxicity.
On the alert for foreign debris, a community of white blood cells known as alveolar macrophages patrols small airways of the lung. When these cells encounter suspicious material, they identify it and send out a chemical clarion call to rally the immune system cells best suited to disabling and disposing of such matter.
The trick is to recruit only as many troops as are needed. If they call in too many, the lung can sustain inflammatory damage from friendly fire. Alongside the small troop of macrophages that stimulates defense measures, a larger squadron of macrophages halts immune activity when it threatens the host.
Andrij Holian and his coworkers in Houston have found that people with healthy lungs normally have 10 times as many suppressor macrophages as stimulatory ones. In people with asthma and other chronic lung diseases -- who face an increased risk of respiratory disease from inhaling urban dust -- that ratio may be only 3 to 1. The reason for the difference is not known.
In a report to be published in the March Environmental Health Perspectives, Holian's team describes test-tube studies of human alveolar macrophages. The macrophages showed no response to ask collected from the Mount St. Helen's eruption. However, when exposed to airborne dust from St. Louis and Washington, D. C. , most of the suppresser macrophages underwent apoptosis, or cellular suicide, while the stimulatory ones survived unaffected. Ash from burned residual oil, a viscous boiler fuel, proved even more potent at triggering suppressor cell suicides.
It this test-tube system models what's actually happening in the human lung, Holian told Science News, the different responses of the two classes of lung macrophages could result in an overly aggressive immune response to normal triggering events. Indeed, he says, it would be the first step in a cascade that can end in inflammatory lung injury. "We may one day be able to target this up stream event and prevent that injury."
"This is, I think, an important contribution to the overall story," says Daniel L. Costa of EPA's pulmonary toxicology branch in Research Triangle Park, N.C.
Studies by EPA suggest that certain metals -- especially iron, vanadium, nickel, and copper -- in smoke from combustion of fossil fuels trigger particularly aggressive inflammatory responses by lung cells. Costa says these metals play a "preminent" role in the toxicity of airborne particulates. When EPA researchers removed the metals, they also removed the toxicity, he says. Moreover, he notes, these metals tend to reside on the smallest water-soluble particles in urban air --the fraction targeted for more aggressive controls under the new rules.
John Vandenberg, assistant director of EPA's National Health and Environmental Effects Research Laboratory in Research Triangle Park, says Holian's results are "a nice complement to our studies."
This passage is mainly about ______.
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An education that aims at getting a student a certain kind of job is a technical education, justified for reasons radically different from why education is universally required by law. It is not simply to raise everyone's job prospects that all children are legally required to attend school into their teens. Rather, we have a certain conception of the American citizen, a character who is incomplete if he cannot competently asses how his livelihood and happiness are affected by things outside of himself. But this was not always the case, before it was legally required for all children to attend school until a certain age. It was widely acteristic of all industrialized countries, we came to accept that everyone is fit to be educated. Computer education advocates forsake this optimistic notion for a pessimism that betrays their otherwise cheery out-look. Banking on the confusion between educational and vocational reasons for bringing computers into schools, computer advocates often emphasize the job prospects of graduates over their educational achievement.
There are some good arguments for a technical education given the right kind of student. Many European schools introduce the concept of professional training early on in order to make sure children are properly equipped for the profession they want to join. It is, however, presumptuous to insist that there will only be so many jobs for so many scientists, so many businessmen, so many accountants. Besides, this is unlikely to produce the needed number of every kind of professional in a country as large as ours and where the economy is spread over so many states and involves so many international corporations.
But, for a small group of students, professional training might be the way to go since well-developed skills, all other factors being equal, can be the difference between having a job and not. Of course, the basics of using any computer these days are very simple. It does not take a life-long acquaintance to pick up various software programs. If one wanted to become a computer engineer, that is of course, an entirely different computer skills are only complementary to the host of great skills that are necessary to becoming any kind of professional. It should be observed, of course that no school, vocational or not, is helped by a confusion over its purpose.
The author thinks the present rush to put computers in the classroom is ______.
Ironically, now that photography is securely established as a fine art, many photographers find it pretentious or irrelevant to label it as such. Serious photographers variously claim to be finding, recording, impartially observing, witnessing events, exploring themselves -- anything but making works of art. They are no longer willing to debate whether photography is or is not a fine art, except to proclaim that their own work is not involved with art. It shows the extent to which they simply take for granted the concept of art imposed by the triumph of Modernism: the better the art, the more subversive it is of the traditional aims of art.
Photographers' disclaimers of any interest in making art tell us more about the harried status of the contemporary notion of art than about whether photography is or is not art. For example, those photographers who suppose that, by taking pictures, they arc getting away from the pretensions of art as exemplified by painting remind us of those Abstract Expressionist painters who imagined they were getting away from the intellectual austerity of classical Modernist painting by concentrating on the physical act of painting. Much of photography's prestige today derives from the convergence of its aims with those of recent art, particularly with the dismissal of abstract art implicit in the phenomenon of Pop painting during the 1960's. Appreciating photographs is a relief to sensibilities tired of the mental exertions demanded by abstract art. Classical Modernist painting -- that is, abstract art as developed in different ways by Picasso, Kandinsky, and Matisse -- presupposes highly developed skills of looking and a familiarity with other paintings and the history of art. Photography, like Pop painting, reassures viewers that art is not hard; photography seems to be more about its subjects than about art.
Photography, however, has developed all the anxieties and self-consciousness of a classic Modernist art. Many professionals privately have begun to worry that the promotion of photography as an activity subversive of the traditional pretensions of art has gone so far that the public will for get that photography is a distinctive and exalted activity -- in short, an art.
The author is concerned with ______.
We can learn from the text that art critics have a history of______.
Opinion polls are now beginning to show a reluctant consensus that, whoever is to blame and whatever happens from now on, high unemployment is probably here to stay. This means we shah have to find ways of sharing the available employment more widely.
But we need to go further. We must ask some fundamental questions about the future of work. Should we continue to treat employment as the norm？ Should we not rather encourage many other ways for serf-respecting people to work？ Should we not create conditions in which many of us can work for ourselves, rather than for an employer？ Should we not aim to revive the household and the neighbourhood, as well as the factory and the office, as centres of production and work？
The industrial age has been the only period of human history in which most people's work has taken the form. of jobs. The industrial age may now be coming to an end, and some of the changes in work patterns which it brought may have to be reversed. This seems a daunting thought. But, in fact, it could offer the prospect of a better future of work. Universal employment, as its history shows, has not meant economic freedom.
Employment became widespread when the enclosures of the 17th and 18th centuries made many people dependent on paid work by depriving them of the use of the land, and thus of the means to provide a living for themselves. Then the factory system destroyed the cottage industries and removed work from people's homes. Later, as transport improved, first by rail and then by road, people commuted longer distances to their places of employment until, eventually, many people's work lost all connection with their home lives and the places in which they lived.
Meanwhile, employment put women at a disadvantage. In preindustrial times, men and women had shared the productive work of the household and village community. Now it became customary for the husband to go out to pay employment, leaving the unpaid work of the home and family to his wife. Tax and benefit regulations still assume this norm today, and restrict more flexible sharing of work roles between the sexes.
It was not only women whose work status suffered. As employment became the dominant form. of work, young people and old people were excluded -- a problem now, as more teenagers become frustrated at school and more retired people want to live active lives.
All this may now have to change. The time has certainly come to switch some effort and re sources away from the utopian goal of creating jobs for all, to the urgent practical task of helping many people to manage without full times jobs.
Recent opinion polls show that ______.
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