The truth is out there ...
In reviewing current pulp bleaching and effluent treatment processes, the industry can clearly take pride in its accomplishments. In the United States, as a whole, it has met the requirements of the Cluster Rule to this point and substantially reduced toxics in pulp bleaching effluents.
The Cluster Rule includes prescribed procedures and levels to determine what is safe or toxic. Those are based on current knowledge and test methods. As we accumulate knowledge, those procedures and levels may change.
A scientific panel commissioned to evaluate the need to further restrict AOX discharges in British Columbia, Canada, reported in March 2002 that it had found no evidence to warrant further reductions (see http://www.aoxpanel.ca/ aoxpanelrev02.pdf.) Based partly on several sub-lethal toxicity studies, the panel did suggest that there could be significant environmental benefit from restricting black liquor discharges.
The panel also noted that many factors influence mill environmental performance and that regulatory standards can vary considerably from region to region. The U.S. Environmental Protection Agency guidelines require mills to measure most effluent discharges at the bleach plant. That means the limits "are more stringent than they would be if applied at the treated outfall." Sampling frequency also influences the results. "In Scandinavia, the effluent permits are frequently based on the annual average of relatively few analyses," the panel stated. "This effectively means that a limit of, say 1.5 kg AOX/ton pulp in Sweden is equivalent to a limit of daily maximum discharge of 2.55 kg/ton in Canada [where daily and monthly limits are set]."
Dioxins serve to illustrate the difficulty of determining toxicity. W.E. Harris nicely covered the topic in "Dioxins--an overview," an article in the April 1990 Tappi Journal (Vol. 73, No. 4, p. 267). He noted that there are 75 different chlorinated derivatives of dibenzo-p-dioxin. The most toxic is 2,3,7,8-TCDD. Other dioxins may be millions of times less toxic. Some species, such as guinea pigs, are more sensitive to exposure, with humans being among the least sensitive.
For the general population, there is only "dioxin," and dioxin is "bad" if it is present in any amount, even parts per trillion. Conversely, most people would say vitamins are "good," without realizing that many vitamins can be toxic at high dosages. They might also be surprised--or alarmed--by a recent California lawsuit claiming most chocolates contain excessive levels of lead and cadmium.
An accepted "truth" now is that cigarette smoke causes lung cancer, or that people who smoke are more likely to develop lung cancer. Do we know what components of cigarette smoke may trigger the cancer? Researchers have theories, but they are still working on a definitive answer.
Some people may have a genetic predisposition for certain forms of cancer. Whether or not they develop that cancer could depend on environmental factors. A factor in some cases might he exposure to a high level of a specific toxic element, it could be long-term exposure to a critical level, it could be diet, it could be chance.
The truth is, there is much to learn yet. Sometimes new information raises concerns about environmental safety. Sometimes those concerns are justified, sometimes they are not.
The truth is, we have significantly reduced the levels of toxic substances discharged by mills. We should be proud of the accomplishment, but we can not be content with those accomplishments.
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|Title Annotation:||Last Word|
|Author:||Meadows, Donald G.|
|Publication:||Solutions - for People, Processes and Paper|
|Date:||Jun 1, 2002|
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