This article first appeared in the St. Louis Beacon: June 3, 2008 - This week, the Senate began considering legislation to combat global warming. A carbon dioxide emissions “cap-and-trade” system, it seems to have little chance of becoming law. It is, however, a welcome sign that our government is beginning to come to grips with a problem that has the entire world worried. In this week’s column I would like to step back and consider the science behind the mess we’ve gotten ourselves into. We as a nation cannot hope to implement the sort of changes necessary to achieve a sustainable world if we as citizens do not clearly understand the nature of the problem we face.
So, how did we get into this mess? In a nutshell, we grew into it. The 20th century was characterized by the unbridled use of resources to fuel growth, with no thought to pollution or future scarcity. If we are going to deal with global warming, it seems to me important that we take a careful, detailed and unvarnished look not only at global warming, but at other ways we are modifying our planet. How we have successfully dealt with other problems may suggest how we could best approach this one.
Our planet is changing in many undesirable ways as we enter the new century, some very obvious, others less so. I would like to examine four. They are by no means the only problems the global ecosystem faces, but a close look at them reveals common elements that I suspect apply very broadly. The four sorts of global change I would like to consider are: 1. the ozone hole; 2. acid rain; 3. global warming; and 4. unsuspected chemical pollution. The first two represent problems that we have solved, the last two, not. Thus the comparison can be very instructive.
1. THE OZONE HOLE. It is useful to start with the ozone depletion story, as several aspects will prove important in other global change problems. Here the story starts with a scientific invention in the 1920s, a class of miracle chemicals called chlorofluorocarbons (CFCs) soon used worldwide as coolants in air conditioners and refrigerators, as the gas in aerosol dispensers, and as the foaming agent in Styrofoam. Very stable, almost all the CFC molecules made for 80 years are still around.
Where are they? Released into earth’s atmosphere. Then atmospheric scientists reported in the 1980s that the accumulating CFCs were depleting the earth’s ozone shield. By now, after 20 years, the drop in ozone worldwide is more than 3 percent, and has led to a 20 percent increase in lethal melanoma skin cancer. Fortunately, the world community has acted in a concerted way to phase out the manufacture of most CFCs. The situation now appears to be improving, and computer models suggest the Antarctic ozone hole should recover in another 50 years.
The problem in a nutshell: chemical pollution, allowed because the chemical (CFCs) was felt to be harmless.
2. ACID RAIN. A very similar picture is seen when we consider another form of worldwide atmospheric pollution, that which leads to acid rain and snow. Here the scientific innovation was the invention in Britain in the mid-1950s of tall smokestacks. When high-sulfur coal is burned in power plants with such tall stacks, the stinky smoke with its high concentrations of sulfur dioxide is delivered high into the atmosphere, its stench undetectable at ground level. Winds disperse and dilute it, carrying the sulfates far away.
The problem, of course, is that the sulfates are not in fact harmless chemicals. In the atmosphere SO2 (sulfur dioxide ) combines with H2O (water) to form H2SO4 (sulfuric acid). By 1970, scientists began reporting that these acids were having drastic effects far downwind. Lakes and forests in northern Europe and in the eastern United States and Canada were literally dying, the acid killing the soil fungi called mycorrhizae needed by tree roots to live. Over 1.4 million acres of forest have been affected. In recent years, clean air legislation has gone a long way toward improving the situation, with chemical “scrubbers: being installed on smokestacks.
The problem in a nutshell: chemical pollution, allowed because the chemical (SO2) was felt to be harmless.
3. GLOBAL WARMING. In recent years, the most talked-about aspect of planet modification has been climate change, more simply and directly referred to as global warming, the direct result of another form of worldwide atmospheric pollution. The scientific advance that has led to global warming was the industrial revolution: more than two centuries of widespread burning of fossil fuels (coal, oil, gasoline, all of them the highly compressed remains of ancient plants) to obtain energy. Fossil fuels are the remains of plants that have been squashed under high pressure for a long time. A plant body is composed largely of woody stuff -- what a chemist calls cellulose and hemicellulose -- basically, molecules that are long chains of sugars linked together like pearls on a necklace. All that is left after all that squishing are short bits, a black gooey mix we call petroleum.
The burning of petroleum and the so-called fossil fuels made from it is a process a chemists calls “oxidation”-- in essence, the energy of their many C-H chemical bonds is released as heat, and the left-over carbon molecules (C) are combined with oxygen gas (O2) to form carbon dioxide (CO2). As the decades passed, the levels of CO2 released into earth’s atmosphere continually increased.
The unanticipated problem is that CO2 is a greenhouse gas -- The C-O chemical bonds absorb longer wavelengths of sunlight, readmitting them as heat, much as the glass of a greenhouse does. If our earth did not have CO2 in its atmosphere, it would be much colder here -- about minus 20 degrees C, instead of today’s plus 15 degrees C. But we are now getting too much of a good thing.
Current estimates are that increases in the amounts of greenhouse gases like CO2 may increase average global mean temperatures as much as 4 degrees in this century, an enormous amount that will raise sea levels as ice caps and glaciers melt, will alter global rain patterns, and will seriously affect agriculture.
Global efforts to abate CO2 emissions have so far been thwarted by the failure of major industrial powers like the United States to cooperate, and by lack of inclusion of fast developing countries like China and India. That the U.S. Senate has awoken to the need for action is a very encouraging sign.
The problem in a nutshell: chemical pollution, allowed because the chemical (CO2) was felt to be harmless.
4. UNSUSPECTED CHEMICAL POLLUTION. The pollution of the world’s air and water by industrial and agricultural wastes is not a new story. Automobile-induced smog in big cities is certainly not new. When the problem became acute in California and other parts of the United States, legislation putting catalytic converters onto car exhausts went a long way toward solving the problem. The more serious problem, as I see it, isn’t this sort of chemical pollution, where the effect is obvious and the issue is effective policy. The more serious problem is chemical pollution where the effects are not obvious. I want to discuss just one, as it provides a good example of just how scary this sort of pollution can be: breast cancer and a chemical called bisphenol A.
An estimated 213,000 new cases of invasive breast cancer occurred in the United States during 2007, less than 2,000 of them among men – more than 99 percent of the new breast cancer victims were women. Similarly, of 40,870 breast cancer deaths that year, all but 460 of them were women. It is impossible not to wonder, why so few men? An obvious answer would be that men don’t have breasts, but men do have breast tissue, it just isn’t as developed as a woman’s. So, we are back to the same question: Why so few men?
While 5 percent of breast cancers are due to inherited genetic mutations (BRCA1 and BRCA2), the cause of 95 percent -- the overwhelming majority -- remains a mystery. Hormone differences seem the most promising place to start, as the female sex hormone estrogen controls breast development in women; men, by contrast, lack physiologically significant amounts of estrogen. A logical suggestion is that in breast-cancer patients the effect of estrogen on breast cells is being altered by exposure to a so-called “endocrine disruptor.” Endocrine disruptors are man-made chemicals that mimic hormones. By sheer chance, their molecules are perfectly shaped to fit particular hormone receptors. In this case, the culprit would be a chemical mimic of estrogen that promotes cancerous growth in breast cells.
One logical candidate is bisphenol A (BPA), a molecule that, like estrogen, has carbon rings at each end tipped with OH groups. Used to form the plastic packaging of many foods and drinks, as well as the clear plastic liners of metal food and beverage cans, BPA is a chemical to which all of us are exposed daily. Six billion pounds are produced worldwide each year.
It has been known since 1938 that BPA promotes excess estrogen production in rats. Alarmingly, in 1993 (15 years ago!) BPA was shown to have the same effects on human breast cancer cells growing in culture. What was alarming was that the effect could be measured at concentrations as low as 2 parts per billion, not much above the levels to which we humans are routinely exposed.
Does BPA in fact induce breast cancer? Dr. Ana Soto of Tufts University School of Medicine did a simple experiment in 2006 to find out, exposing laboratory rats to BPA and looking for evidence of increased breast cancer. She found that exposure to even low levels of bisphenol A induced ductal hyperplasias (precursors of breast cancer) in her laboratory rats, suggesting the rather alarming conclusion that BPA, a chemical to which we are all exposed every day, may indeed cause breast cancer.
While the study is small and a rat is not a human, a new draft report released this spring by the National Toxicology Center of the National Institutes of Health says low levels of exposure to BPA can also cause changes to mammary gland tissue in human infants, indicating potential long-term risks of breast cancer in humans as well. Acting on the precautionary principle, Canada has banned BPA. Most government-funded breast cancer research in the United States has focused on the search for more effective breast cancer treatments; far less money is spent on searching for the causes of breast cancer. More should be.
The problem in a nutshell: chemical pollution, allowed because the chemical (BPA) was felt to be harmless.
You can see the pattern emerging from these four examples of planet modification. Each is the result of chemical pollution, allowed because the chemical was felt -- mistakenly -- to be harmless.
Tomorrow, with this general picture as a background, this column will discuss the role science has to play in addressing these sorts of problems,and others we have not yet recognized.
'On science'
George B. Johnson is bringing his "On Science" column to the St Louis Platform. This column, which appeared for several years in the Post-Dispatch, looks at scientific issues and explains them in an accessible manner. There is no dumbing down in Johnson's writing, rather he uses analogy and precise terms to open the world of science to others.
Johnson, Ph.D., professor emeritus of biology at Washington University, has taught biology and genetics to undergraduates for more than 30 years. Also professor of genetics at Washington University’s School of Medicine, Johnson is a student of population genetics and evolution, renowned for his pioneering studies of genetic variability.
He has authored more than 50 scientific publications and seven texts, including "BIOLOGY" (with botanist Peter Raven), "THE LIVING WORLD" and a widely used high school biology textbook, "HOLT BIOLOGY."
As the founding director of The Living World, the education center at the St Louis Zoo, from 1987 to 1990, he was responsible for developing innovative high-tech exhibits and new educational programs.
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