Keeping Pace with Science and Engineering Case Studies in Environmental Regulation (1993) / Chapter Skim
Currently Skimming:
The Dioxin TCDD: A Selective Study of Science and Policy Interaction
The Dioxin TCDD: A Selective Study of Science and Policy Interaction
Pages 221-242
The Chapter Skim interface presents what we've algorithmically identified as the most significant single chunk of text within every page in the chapter.
Select key terms on the right to highlight them within pages of the chapter.
From page 221... ...
activities relevant to that use; and setting state water quality standards for TCDD in the Clean Water Act. Figure 2 summarizes the sequence of events.
|
From page 222... ...
and 2,4,5-T. To investigate the possibility of a causal association between exposure to Agent Orange and birth defects, an extensive study was performed in male mice.
|
From page 223... ...
in Missouri - Concern about miscarriages in Alsea, Oregon - TCDD a carcinogen in laboratory studies - Love Canal - Alsea, Oregon II study associates miscarriages with herbicide spraying - Epidemiology study associates soft ~ tissue sarcoma in humans with I exposure to herbicides - Seveso 5-year report-no ill effects - Times Beach, Missouri buyout - Ad hoc expert committee advises EPA that linearized model for cancer is inappropriate - EPA scientific group recommends moderating , cancer risk estimate I - EPA SAB finds no new science data to support change in cancer risk estimate; critical of current cancer model - Banbury Conference supports a receptormediated event for dioxin activity - Fingerhut epidemiology study published - EPA initiates review of dioxin risks - P.L. 102-4, Agent Orange Act" enacted - IOM/NAS starts review of evidence associating herbicide exposure with disease in Vietnam veterans 1 1 980 1 ,_ _ ~, .
|
From page 224... ...
This CDC birth defects study was designed to determine if Vietnam veterans were fathering children with a higher incidence of birth defects. The potential risk factor being investigated was service in Vietnam, not TCDD exposure, per se, since there were no records that allowed such a distinction.
|
From page 225... ...
Another publication from the same group of Swedish investigators reported that there was no difference in the levels of TCDD or the pattern of other chlorinated dibenzodioxins and dibenzofurans in adipose samples collected from cancer (soft tissue sarcomas or lymphomas) patients classified as "exposed" to phenoxy herbicides and a group of controls that had no history of phenoxy acid herbicides (Nygren et al., 1986~.
|
From page 226... ...
In support of the contention of Collins et al., a study of 1,600 German chemical workers exposed to TCDD found no soft tissue sarcomas (Zober, 1990; Manz et al., 1991~. The German study did report an increase in deaths from all cancers, and respiratory cancers are a major contributor to the overall excess of cancer deaths.
|
From page 227... ...
changed this practice in estimating cancer risk in the United States on the assumption that there are no NOELs for carcinogens but that risk decreases with dose, reaching zero risk at zero dose. The choice of this specific risk estimation model called the no-threshold model, was strongly influenced by studies of cancer in experimental animals exposed to radiation, the best source of data available at that time.
|
From page 228... ...
Other federal agencies, such as the Food and Drug Administration and the Centers for Disease Control and Prevention, have also derived estimates of TCDD cancer risk using the same basic methods but, owing to differences in other scientific assumptions such as how to adjust for differences in size of mice, rats, and humans, their estimates have produced values that permit exposure levels that are, respectively, nine and four times higher than the EPA's estimate. Other countries have not elected to apply a linear multistage model as the standard means for estimating cancer risk.
|
From page 229... ...
In a separate activity, many scientists that were experts on the effects of dioxin expressed the opinion at a 1990 Banbury Conference that using traditional models for assessing cancer risk from dioxin is not appropriate; there was consensus that the known toxic effects of dioxin are receptor mediated. The Current EPA Reassessment On April 8, 1991, the EPA administrator announced that the agency would reassess the risks of exposure to TCDD and related compounds in light of significant advances that had occurred in the scientific understanding of the mechanisms by which dioxin becomes toxic, the health effects in animals and people, the pathways to human exposure, and the toxic effects of dioxin in the environment.
|
From page 230... ...
are inaccurate by more than two orders of magnitude or incorrectly predict for certain toxic effects, such as cancer potency. The dioxin reassessment was originally scheduled to be completed in the latter part of 1992; current estimates are that the revised assessment will be submitted to the EPA Science Advisory Board in the spring of 1993 and, in turn, their review will be transmitted to the administrator in late 1993.
|
From page 231... ...
The data indicating TCDD's potential for causing birth defects and other forms of developmental abnormalities in laboratory studies led to the 1970 decision by the U.S. Department of Agriculture, the agency that then regulated pesticides in the United States, to eliminate many domestic uses of 2,4,5-T, including homeowner use and use on food crops.
|
From page 232... ...
On the recommendation of an advisory committee, the Department of Veterans Affairs (VA) currently compensates veterans that served in Vietnam if they develop chloracne or soft tissue sarcoma.
|
From page 233... ...
The report is to be issued in the latter part of 1993 and will provide scientific and medical information for the Secretary of Veterans Affairs to consider when making determinations about compensation. Clean Water Act Section 303 of the Clean Water Act requires states to adopt water quality standards to protect the public health or welfare and enhance the quality of water.
|
From page 234... ...
· In 1974, studies in Missouri revealed that waste oil, applied to dirt roads and horse arenas to suppress dust, contained TCDD and was responsible for sickness and death in horses and possibly accounted for illness in two youngsters (Carter et al., 1975~. In 1982 an entire town, Times Beach, Missouri, was purchased by the state and federal government, who stated the action was necessary as a result of TCDD contamination that occurred through the application of waste oil to unpaved streets.
|
From page 235... ...
In some instances, scientific data on adverse effects were persuasive for policymakers and in other instances scientific doubt or uncertainty as to adverse effects resulted in hesitancy to establish or change policy. Courtney and colleagues reported in 1969 and 1970 that TCDD could cause birth defects in animals.
|
From page 236... ...
Specifically, the negative results from the CDC birth defects study persuaded Congress not to compensate Vietnam veterans for children born with birth defects. In the Agent Orange class action suit, brought on behalf of Vietnam veterans against manufacturers, the presiding judge, Judge Jack Weinstein, in summing up the evidence stated, "no laboratory nor epidemiologic evidence exists at this time that is sufficient to link deaths or birth defects to parental exposures to herbicides while serving in Vietnam" (Gough, 1986, pp.
|
From page 237... ...
This action under the Clean Water Act, as well as prompting the dioxin reassessment process described above, suggests that the EPA's rigid institutional commitment to a narrow modeling approach for assessing cancer risks may have been weakened. If so, EPA may become more receptive to review and use of newer knowledge.
|
From page 238... ...
A debate continues on the "proper" interpretation of human epidemiology data regarding cancer. From a policy perspective, this is not a major issue; the debate is not going to yield a definitive answer; thus, based on animal data, TCDD will continue to be viewed as a human carcinogen.
|
From page 239... ...
Legislation calling for a National Academy of Sciences report on current scientific understanding underscores the continuing unease and uncertainty regarding the scientific facts as well as the desire that the data and scientific judgments may guide a VA policy that fairly responds to the health concerns and afflictions of Vietnam veterans. REFERENCES Air Force Health Study.
|
From page 240... ...
1981. On the relation of soft tissue sarcoma, malignant lymphoma, and colon cancer in phenoxy acids, chlorophenols and other agents.
|
From page 241... ...
1989. Elevated body burdens of 2,3,7,8-tetrachlorodibenzodioxin in adipose tissue of United States Vietnam Veterans.
|
From page 242... ...
1987. Soft tissue sarcoma and non-Hodgkin's lymphoma in relation to phenoxy herbicide and chlorinated phenol exposure in Western Washington.
|
Key Terms
This material may be derived from roughly machine-read images, and so is provided only to facilitate research.
More
information on Chapter Skim is available.