IN a new report on dioxin, the United States Environmental Protection Agency (EPA) treads carefully in attributing human health problems to this highly toxic substance.
The 2,000-page study released on Sept. 13 is completely satisfying to neither environmentalists nor the industries tied to the controversial chemical compounds often associated with the Vietnam herbicide Agent Orange and the evacuation of Times Beach, Mo., 10 years ago.
But the EPA's assessment, which involved more than 100 scientists over a three-year period, reaffirms ``with greater confidence'' earlier government findings that dioxin is a ``probable human carcinogen.''
In addition, according to EPA assistant administrator Lynn Goldman, there is ``a stronger body of evidence'' to suggest that dioxin also may result in developmental, reproductive, and immunity problems.
The EPA describes its report as ``the most exhaustive scientific review of a single compound ever undertaken by the agency.'' It will not be complete for another year, however, by which time the EPA hopes to have gathered more information from government and private sources as well as conducted a scientific peer review.
Dioxins are a family of 75 chemical compounds resulting inadvertently from combustion, the manufacture of certain chemicals, the chlorine bleaching of pulp and paper, and other industrial processes.
Many US companies whose products have been linked to dioxin continue to be critical of EPA findings, but some are actively working to eliminate the controversial chemical from their businesses.
The day before the EPA report was issued, Louisiana-Pacific Corporation announced that it had eliminated dioxin discharges at two of its three pulp mills in the US by removing chlorine or chlorine compounds from its bleaching process. At present, European mills are ahead of their US counterparts in producing chlorine-free paper.
Early this year, the US-Canadian International Joint Commission called ``exposure to persistent toxic substances ... the most significant problem facing the Great Lakes region,'' and it called upon both governments to end the use of chlorine in manufacturing.
While the total amount of dioxins produced each year in the United States is fairly small - 30 pounds by government estimates -
the EPA describes it as ``highly toxic'' and therefore ``a significant environmental pollutant.''
According to Dr. Goldman, municipal and medical-waste combustion account for most known dioxin emissions. The problem for humans occurs when airborne dioxins enter the food chain through plants and then the fat of animals.
Response to the EPA report has been mixed.
IN an analysis on behalf of the National Cattlemen's Association, a group of scientists from Texas A&M University state that the ``EPA's conclusions are based frequently on incomplete, extremely limited, or outdated data that severely comprise the scientific integrity of the report.''
For example, according to this analysis, EPA failed to account for lower beef consumption by Americans in recent years and for the trend toward leaner beef.
Other affected industries responded critically as well.
``We strongly believe that there is a need to bring more conclusive scientific information to the process,'' said Brad Lienhart, managing director of the Chlorine Chemistry Council (an arm of the Chemical Manufacturers Association).
A recent study by the environmental group Greenpeace, on the other hand, finds that ``EPA's list neglects dozens of dioxin sources that have been identified in the scientific literature and government reports and underestimates actual emissions from incinerators.''
``As a result,'' Greenpeace charges, ``the agency's list accounts for only 10 to 50 percent of the 25,000 grams of dioxin that EPA estimates are deposited into the environment each year.''
Sierra Club president J. Robert Cox called the EPA's report ``potentially as significant as the 1964 Surgeon General's report on smoking and public health.'' Other environmental leaders say there now is enough evidence to treat dioxin like lead and remove all sources of human exposure.
While the EPA's Dr. Goldman acknowledges ``significant data gaps that are critical to our understanding and effective management of dioxin,'' the federal government is moving on several fronts to control the chemical.
Earlier this month, EPA administrator Carol Browner announced proposed air standards for municipal-waste incinerators that would reduce dioxin emissions by 95 to 99 percent. Similar regulations for medical-waste incinerators will be proposed early next year. The EPA also has identified dioxin as a key contaminant at two dozen of the Superfund toxic waste sites most needing attention. And as part of its Clean Water Act program, the Clinton administration proposed effluent- limitation guidelines for mills that create dioxin in the bleaching process of pulp and paper manufacture.