Archive for the ‘Living Downstream’ Category

No matter how improved or what they are called, incinerators present two problems that landfills do not. First, incinerators only transform garbage; they don’t provide a final resting place for it. There remains the question of where to put the ashes. Second, these cavernous furnaces create, out of the ordinary garbage they are stoked with, new species of toxic chemicals. In addition to producing electricity, they generate hazardous waste….

Moreover, the process of burning concentrates into the ash whatever hazardous materials are present in the original refuse. Heavy metal, such as mercury, lead, and cadmium, for example, are not destroyed by fire. Occurring as ingredients in household batteries, lightbulbs, paints, dyes, and thermometers, they are absolutely persistent. Air pollution control depends on the ability of an incinerator’s cooling chambers to condense these metals onto fine particles, which are then caught in special filters.

Once again, the irony of trade-offs becomes readily apparent: the less air pollution, the more toxic ash. An incinerator burning eighteen boxcars of trash per day, for example, produces about ten truckloads of ash per day. The trucks must then rumble out onto the highways, hauling their poisonous cargo through all kinds of weather. Once ensconced in special burying grounds, incinerator ash, of course, presents a hazard to groundwater.

The second problem is more an issue of chemistry than physics. Somewhere between the furnaces and the top of the stack, on the slippery surfaces of fly ash particles, in the crucible of heating and cooling, carbon and chlorine atoms rearrange themselves to create molecules of dioxins and their closely related organochlorine allies, the furans.

There are many dozens of dioxins and furans, but, as with snowflakes, their individual chemical configurations are all variations on a theme. Recall that benzene consists of a hexagonal ring of carbon atoms. This ring can then be studded with chlorine atoms. Two chlorinated benzene rings bonded directly together form a polychlorinated biphenyl, a PCB. By contrast, two chlorinated benzene rings held together by a single atom of oxygen and a double carbon bond are called a furan. A pair of chlorinated benzene rings linked by two oxygen atoms form a dioxin. There are 135 furans and 75 dioxins, each with a different number and arrangement of attached chlorines.

Dioxins and furans behave similarly in the human body, and they all to some degree elicit the set of biological effects described earlier. The most poisonous by far, however, is the dioxin known as TCDD. This particular molecule bears four chlorine atoms, each bonded to an outer corner. Because these points of attachment are located on the carbon atoms numbered 2,3,7, and 8, its full name is a mouthful. 2,3,7,8-tetrachlorodibenzo-p-dioxin. Imagine looking down from an airplane window at a pair of skydivers in a free fall, both hands joined together. Their geometry provides a reasonable impersonation of a TCDD molecule: the divers’ linked arms represent the double oxygen bridge, their bodies the benzene rings, and their splayed, outstretched legs the four chlorine atoms.

TCDD is scary because it is so stable. The symmetrical arrangement of its chlorine legs prevents enzymes–ours or any other living creature’s–from breaking TCDD apart. In human tissues, TCDD has a half-life of at least seven years. As we shall see, this particular geometry also allows TCDD admission into a cell’s nucleus and access to its DNA.

Ascertaining dioxin’s contribution to human cancers is one of the more frustrating challenges for public health researchers. Because dioxin is so potent at such vanishingly small levels, exposure is expensive to measure. Because it is so widely distributed, there remain no populations to serve as unexposed controls. Because dioxin so often rides the coattails of other carcinogens, confounding factors abound. U.S. military personnel exposed to Agent Orange in Vietnam, for example, were simultaneously exposed to 2,4-D and dioxin-contaminated 2,5,5-T, as noted in Chapter Three.

Animal studies provide a complex set of clues. In the laboratory, dioxin is an unequivocal carcinogen. As the dioxin researcher James Huff once noted, “In every species so far exposed to TCDD….. and by every route of exposure, clear carcinogenic responses have been found.” These include cancers of the lung, mouth, nose, thyroid gland, adrenal gland, lymphatic system, and skin. Dioxin also causes liver cancer in rats and mice, but it does so more often in females. Female rats whose ovaries have been removed, however, tend not to develop liver cancer when exposed to dioxin. On the other hand, they are far more likely to succumb to lung cancer. Clearly, an organism’s own internal hormones modulate dioxin’s carcinogenic powers, but through some unclear means.
(Portions from pages 215 – 223)

For more on the book by Sandra Steingraber click on the link below.

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This study is important because it raises questions about drinking water standards. This study was referenced in Living Downstream by Sandra Steingraber

The exhaled breath of people who had recently showered contained elevated levels of volatile organic compounds. In fact, a ten-minute shower or a thirty minute bath contributed to a greater internal dose of these volatile compounds than drinking half a gallon of tap water. Showering in an enclosed stall appears to be contribute to the greatest dose, probably because of the inhalation of steam.

The particular route of exposure profoundly affects the biological course of the contaminant within the body. The water that we drink and use in cooking passes through the liver first and is metabolized before entering the bloodstream. A dose received from bathing is dispersed to many different organs before it reaches the liver. The relative hazards of each pathway depend on the biological activity of the contaminant and its metabolic breakdown product, as well as on the relative sensitivity of the various tissues exposed along the way.

The bathing studies raise additional questions about drinking water standards. Once again, we see how narrow the purview of these regulations is. The environmental scientists Clifford Weisel and Wan-Kuen Jo, the authors of the 1996 study, pointedly explained:

Traditional approaches for evaluating exposure to and adverse health effects from contaminants in tap water have assumed that ingestion is the major route of exposure….Furthermore, the ingestion of two liters of water has been used to estimate the health risk associated with waterborne chemical contaminants and the establishment of drinking water standards without quantifying the doses received from other routes. This practice can lead to an underestimation of the potential health risk.

page 198

Living Downstream by Sandra Steingraber

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Benzo[a]pyrene – Living Downstream by Sandra Steingraber

Benzo[a]pyrene causes cancer in a simple, direct way. Nearly all living things have in common a group of cellular enzymes responsible for detoxifying and metabolizing possibly harmful chemical invaders. When this enzyme group encounters benzo[a]pyrene, it inserts oxygen into the foreign molecule, the first step toward breaking it down. However, in a strange twist of fate, this addition activates benzo[a]pyrene rather than detoxifies it. The altered molecule now has the ability to bond tightly to a strand of DNA — that is, to one of the cell’s chromosomes along which lie the organism’s genes. A chemical invader so attached is called a DNA adduct, and it has the power to alter the structure of the DNA strand and cause a genetic mutation. If uncorrected, this type of damage can become a crucial step leading to the formation of cancer. Page 136

Benzo(a)pyrene (a polycyclic aromatic hydrocarbon reproductive [see below], formed when oil or gasoline burns) – Irritation to eyes and skin, cancer, possible effects.

– Taken from the Training Marine Oil Spill Response Workers under OSHA’s Hazardous Waste Operations and Emergency Response Standard

Coal tar itself is classified as a known carcinogen, but because humans are almost always exposed to its constituent ingredients in mixtures, the data from human studies are inadequate to so classify benzo[a]pyrene individually.

Chemical Profile for Coal Tar from Scorecard

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