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Exposure Investigation Report


APPENDIX 1 - Dioxin Comparison Levels

Comparison values for dioxin-like compounds in blood serum are listed in Table 1. To derive these values, ATSDR pooled data from seven studies that measured dioxin levels in residents of the United States who had no known exposure to dioxins, other than normal background levels. The studies contained a total population of about 400 individuals. The blood samples were collected during the time period, 1995 to 1997. The National Center for Environmental Health in Atlanta, Georgia, conducted the laboratory analyses using gas chromatography/isotope dilution-high resolution mass spectroscopy.

In some samples, the concentrations of one or more congeners were reported as not detected. For the statistical summary of total TEQs across the eight studies, the concentration of a non-detected congener was assumed to be one-half of the analytical detection limit. In some of the studies, analytical data (including detection limits) for one or more congeners were missing in some individuals because of analytical difficulties. For these individuals, the TEQ concentration of the non-reported congener was assumed to be equal to the average TEQ for that congener for all other individuals in their study. Two congeners (123478D and 123678D) were not reported for any individuals for several of the studies. For the studies where these congeners were missing, the replacement value used was the average of the TEQ concentration for the congeners from studies where the congeners were reported.

The comparison levels in this report were based on a preliminary analysis of the available data. ATSDR will submit a more detailed report of these analyses and findings to a peer-reviewed, scientific journal for publication. The authors of this report acknowledge the assistance of Dr. Richard Canady in deriving the dioxin comparison values cited in this report.

APPENDIX 2: Comments received during the public comment period for ATSDR's Draft Exposure Investigation Report for Mossville, Calcasieu Parish, Louisiana (May 7, 1999)

Commentor Number 1

(1-1) We ask that this investigation not be limited to only dioxin. We want all of the other hundreds of chemicals we are exposed to, to have the same level of investigation. We are also concerned about how the mixing and accumulation of these many chemicals inside the body affect overall human health.

Response: It is not technically feasible to test for hundreds of chemicals. Efforts and resources have to be focused on testing for chemicals that pose the greatest health concern because of factors such as toxicity and risk of exposure. As stated in the Exposure Investigation (EI) report, ATSDR had evidence of increased exposure to dioxin in some residents of Calcasieu Parish and Mossville. This information prompted ATSDR to conduct biological and environmental testing for dioxins in Mossville.

A Mossville Public Health Response Workgroup has been formed to gather information on potentially exposed populations. ATSDR will continue to work with the community, the Louisiana Department of Health and Hospitals, the Louisiana Department of Environmental Quality, and the Environmental Protection Agency to identify communities at risk for possible exposures to dioxin or other environmental contaminants. If such communities or exposures are identified, additional testing may be conducted.

(1-2) Your cover letter and first page isolates and limits your investigation to Mossville only and then further limits the investigation to dioxin. Please provide us with the procedure and exact steps that we need to take in order for the rest of Calcasieu Parish to receive the same level of concern and investigation as Mossville. We thought we were following your process for all of Calcasieu, since the community member provided you with test results for all of Calcasieu Parish (the control samples were three times the national average). We were surprised to learn that only Mossville is being investigated and the rest of the Parish is being ignored.

We suggest composite blood samples be taken and tested from every facility that does blood work in Calcasieu Parish. Such as every hospital, nursing home, doctor's office, and school that perform blood work.

Response: A Mossville Public Health Response Workgroup has been formed to gather information on potentially exposed populations. ATSDR will continue to work with the community, State, and Federal agencies to identify communities at risk for possible exposures to environmental contaminants. If such communities are identified, additional testing may be conducted.

(1-3) We believe the air we breathe is a very significant means by which we are contaminated.

Response: ATSDR agrees that air contamination is an exposure pathway of potential health concern. ATSDR supports further investigations to characterize air contamination.

(1-4) We believe weather conditions in Calcasieu Parish cause most of the contaminants to be at ground level most of the nights causing our homes to be saturated in this toxic soup. At daylight the contaminants begin to rise.

We believe the wind rose will show that other parts of Calcasieu are exposed to more contaminants more of the time than Mossville.

Response: Although wind roses help scientists understand predominant wind directions, they do not define the dispersion and deposition of contaminants from sources. Modeling of the source would identify the locations that would be most significantly impacted. However, the sources have to be defined before scientists have confidence in the model's predictions.

(1-5) We do not believe that sufficient testing has been done relative to breast milk, soil, eggs and want more diversified sampling and testing. Testing of residue on window screens is suggested if you can find a window screen still intact.

Response: One of the purposes of the Mossville Public Health Response Workgroup is to discuss options for further characterization of environmental contamination.

(1-6) We want to be involved in helping the ATSDR to locate the sources of contaminants of concern. You tell us what you are looking for, and we will help you identify all of the sources.

Response: The Calcasieu community has been invited to participate in the Mossville Public Health Response Workgroup meetings. ATSDR encourages you to participate.

(1-7) We ask that the ATSDR continue to have public meetings in Calcasieu Parish

Response: The Mossville Public Health Response Workgroup will continue to hold meetings to discuss environmental health issues.

(1-8) We ask that the ATSDR not simply find an excuse for a dioxin source, close the investigation, and leave Calcasieu Parish as is suggested in reading in between the lines of the investigation.

Response: ATSDR will continue to work with the community and Federal and State agencies to resolve environmental health issues in Mossville and Calcasieu Parish.

Commentor Number 2

(2-1) I am pleased that ATSDR has acknowledged the existence of elevated blood dioxin levels in a portion of the Calcasieu population.

I am glad that ATSDR recommends minimizing exposure to environmental sources of dioxin.

I am encouraged that ATSDR recommends conducting additional environmental testing to identify possible sources of dioxin exposure in residents of Mossville.

I am discouraged at the apparent failure of ATSDR to realize that the original blood dioxin tests done in Calcasieu showed that Bayou d'Inde neighborhood people also carried a heavy burden of dioxin, and that even a "Calcasieu Background" or parish wide control sample consisting of 100 people's blood blended together showed almost triple the national average for the most dangerous dioxin, 2,3,7,8-tetrachlordibenzodioxin.

No mention of these facts was made in the exposure assessment. No mention was made of trying to minimize exposure of neighborhoods other than Mossville, nor of finding sources of exposure for any population other than Mossville.

Response: The test results referred to in this comment were discussed in a previous ATSDR Health Consultation (October 16, 1998). This consultation was referenced in the Exposure Investigation report. The purpose of the Exposure Investigation was to determine if there was evidence for increased exposure to dioxin in the Mossville community. ATSDR's Exposure Investigation was not intended to be a comprehensive survey of possible exposures throughout Calcasieu Parish. ATSDR anticipates that the Mossville Public Health Response Workgroup will discuss the feasibility of conducting additional environmental and biological testing for dioxin.

(2-2) I appreciate ATSDR's having responded to a request I made for a copy of Reference 6 by Needham et al: "Reference Range Data for Assessing Exposure to Selected Environmental Toxicants." The publication itself was confusing to me, though. I could not tell whether the reference ranges presented might have included data from populations which had some unusual dioxin exposures other than the occupational exposure mentioned.

It was interesting that the Needham publication pointed out that the outdated ranges could be high, something reinforced in your ATSDR discussion. I look forward to receiving a more up-to-date assessment of reference ranges which will make more rational any comparison of current Calcasieu blood dioxin levels with the reference ranges.

Table 1 shows a reference range of 36 to 58 ppt. 47 ppt would lie in the middle of that range but the Mossville population lies at 54.6 which is at the high end of the range. That would seem to indicate to me that the Mossville population as a whole could have elevated levels, not just the few that were singled out for discussion on page 7. Page 7 says that 12 of the 28 people exceeded the upper end of the range, but how many exceeded the national average?

The comparison with Tifton, Georgia where a pesticide plant operates was interesting but I do not know the history of that location, whether or not there was confirmed dioxin exposure of the neighborhood, and, if so or if not, what does that tell us about the Mossville exposures?

I did read the sentence on Page 8 that says that the Georgia and also the German situation mentioned "support the conclusion that blood dioxin levels in residents of Mossville are elevated compared to other populations" but if those two other places were tested because of known problems it would seem to emphasize, not just "support" the conclusion that Calcasieu has a definite problem.

Response: In the draft Exposure Investigation report, ATSDR recognized the limitations of the available dioxin reference ranges. Since the draft report was released, ATSDR has worked with the National Center for Environmental Health at the Centers for Disease Control and Prevention to develop updated dioxin comparison values. The text of the final report has been revised to incorporate updated comparison values.

(2-3) The single test of human milk was reassuring, but without more mothers being tested, and without knowing how many children the one mother had nursed and for how long, and even how long she had lived in Mossville and whether or not her exposure history is the same as any other mothers in Calcasieu, I think that it could be dangerous to leave the impression that we can all now be sure that there is not a problem in any Calcasieu mother's milk.

Response: ATSDR agrees that a single milk sample may not be representative of the community. ATSDR had agreed to do additional breast milk testing, but only one volunteer provided a sample.

(2-4) Page 9 had some worrisome wording, where the report speculates about the control egg having a relatively low reading instead of pointing out that the Mossville eggs were approximately double the control egg readings.

Response: The report specifically states, "The concentrations of dioxin detected in two chicken eggs from Mossville were about 2 times higher than the concentration of dioxin detected in an egg from a Kansas City supermarket." Supermarkets usually obtain eggs from commercial farmers who raise hens in indoor pens in a controlled environment. The dioxin levels detected in Mossville eggs were less than those detected in eggs from chickens that were allowed to forage outside in uncontaminated areas (See Table 3 and reference 15).

(2-5) The ATSDR recommendation for "additional environmental testing" is vague. Does that mean more human blood, milk, egg, and soil testing? Does it mean air samples? What does it mean and what does it not include?

Response: Environmental testing usually refers to environmental media such as air, soil, water, and sediment; however, it can also include food sources (e.g., fish, milk, and eggs) that people eat. ATSDR anticipates that the Mossville Public Health Response Workgroup will discuss the feasibility of conducting additional environmental sampling.

(2-6) I found it especially disconcerting to see a sentence on Page 8 that says: "The only confirmed health effects of dioxin exposure in humans are chloracne and transient mild hepatotoxicity." An article in the Journal of the National Cancer Institute, Vol. 91, No. 9, May 5, 1999, by Steenland et. al. says that "In 1997 the International Agency for Research on Cancer classified 2,3,7,8-tetrachlorodibenzo-p-dioxin (TCDD) as a group 1 human carcinogen..." The article goes on to say the authors' work has established a dose response relationship and also that now they cannot be sure that there is no risk for people with low exposure. Furthermore, the Steenland article talks of finding evidence of a connection between heart disease and TCDD exposure in chemical plant workers. (Please do not forget that I introduced ATSDR to a worker who told them of his personal experience with exposure and how he and almost all of the heavily-exposed workers he knew have come down with heart disease.)

When I read the "only confirmed health effects..." sentence I immediately began thinking of all the times we have heard petrochemical public relations people and LADHH spokespersons saying the same sort of thing, even when we knew how sick certain people had been made by particular exposures to environmental contaminants. We do not need more brushfire bureaucracy in Calcasieu, that got old years ago. I was surprised to see such a sentence in a report that, in other places sounded like it was on the right track.

Response: As noted in the cited article, IARC indeed has classified 2,3,7,8-TCDD as a group 1 carcinogen based on limited human epidemiology data, sufficient animal data, and supplementary information on biological mechanisms. However, other agencies such as the EPA and NTP have designated TCDD as a possible or probable human carcinogen and concluded there is not sufficient evidence of carcinogenicity in humans to classify TCDD as a confirmed human carcinogen. Also, this group 1 designation applies only to TCDD; other dioxin-like compounds have not been similarly classified. The cited study by Steenland et al. demonstrates some of the methodological difficulties in determining health effects from dioxin. Steenland et al. did note increased risk of ischemic heart disease and cancer in the highest exposed cohort. However, they also noted that this exposure group likely had exposures that were 100-1000 times higher than the general population. Limitations identified by Steenland et al. in their study included the possibility of multiple chemical exposures in the study group and limited data regarding smoking. Also, the actual dioxin blood concentration in the cancer and heart disease cases was not known and was estimated using various assumptions. Steenland et al. noted that the association of cardiovascular morbidity and dioxin has not been consistent in previous studies.

There is little debate that exposure to dioxin causes chloracne or transient liver abnormalities. However, as discussed in the EI, the association of dioxin with other health effects remains unconfirmed due to study limitations regarding exposure assessment and inconsistent study results.

(2-7) Provide an up-to-date "reference range" or perhaps better yet, a table showing the United States average, and the world average for each dioxin like molecule, so we can better compare Mossville with other populations.

Provide a table showing all the Calcasieu analytical data collected so far in order that we can better compare Mossville with other populations.

Provide more information on the frequency of occurrence of elevated levels of each congener in non-Calcasieu areas known to have different types of sources so that we can be thinking about what sources might be causing the distribution of contamination we see in our parish's human sampling.

Response: The response to comment 2-2 addresses dioxin reference ranges.

For information on sources and environmental levels of dioxin-like compounds, please refer to published review documents: (1) ATSDR; Toxicological Profile for Chlorinated Dibenzo-p-Dioxins (update); December 1998. (2) EPA; Estimating Exposure to Dioxin-Like Compounds; Review Draft; Volumes II and III; June 1994.

(2-8) Recommend more testing:


Blood samples from the Bayou d'Inde Community (closer to possible major sources than Mossville and where blood evidence already exists showing problem of similar magnitude to that in Mossville).

Blood samples from West Mossville (more downwind from possible major sources than East Mossville, where ATSDR's samples were taken).

Blood samples from Town of Westlake (less downwind than East Mossville from possible major sources).

100 person composite blood samples from:

    (a) Life Share Blood Bank (a "healthy Calcasieu population)
    (b) Christus St. Patrick Hospital (to compare/contrast with the 1997 "Calcasieu Background sample)
    (c) Jennings American Legion Hospital (which should be beyond the range of the Calcasieu source)
    (d) High Hope Road Care Center (elderly population downwind from major possible sources)
    (e) Maplewood Middle School (young people near possible sources - high incidence of ADD)

Blood samples of occupationally-exposed individuals.

At least 5 more milk samples, parish wide


Fatty tissue from rats, 2 samples each, from all of the above locations plus North, Central, and South Lake Charles

Seafood samples, two each from Lake Charles, Prein Lake, and Moss Lake
   Crab - all soft tissue since all is used in some local recipes
   Catfish fillets
   Croaker fillets
   Whole menhaden

Craklins from hogs equidistant from Lake Charles to the North, South, East, and West


Analyses of dioxin like molecule concentration on surface and within (enclosed inside fullerene clusters) airborne particles upwind and downwind of suspected sources

Dioxin analyses of soot from major incinerator, furnace, flare, and kiln stocks.

Conduct a few tests in each medium for halogenated dioxin like molecules other than chlorinated, that is: brominated, iodinated, and fluoridated. (we know from the relative activities of the halogens that if there is a source of bromine, for example, the chlorodioxins could become bromodioxins. In the estuary there is a source of bromine and iodine, sea water, but no one has looked to see if there is lurking out there any significant amount of those other halodioxins. They may be out there, they may be in us. They may even be more actively harmful than the chlorodioxins. They may be part of the explanation for Calcasieu's health problems.

Response: The Mossville Public Health Response Workgroup will discuss the feasibility of conducting further biological and environmental testing.

(2-9) I recommend that government chemical engineers carefully study existing information to help zero in on all possible sources of halodioxin in Calcasieu.

Response: ATSDR agrees that additional studies are warranted to identify potential sources of dioxin exposure in Calcasieu Parish.

(2-10) I recommend that the Justice Departments offer a one-time, short window of opportunity for amnesty from criminal prosecution to any dioxin source that self-identifies.

Response: This recommendation is outside the scope of ATSDR's activities.

(2-11) Convene a conference of regional medical professionals to tell them what you have found, what to look for in patients, and what to do if they have dioxin-contaminated patients.

Response: A representative of ATSDR's Division of Health Education and Promotion is participating in the Mossville Public Health Response Workgroup, which can consider such proposals.

(2-12) Above all, if you do no further testing of other Calcasieu populations right away, it is imperative that you make clear that this report does not address the concerns that were raised by the 1997 blood sample B-26 from the Bayou d'Inde resident nor does it address the concerns that were raised by the 1997 blood sample of worker B-8, nor does it address the parish wide concerns that were raised by the 100-person composite from St. Patrick's hospital.

Response: The Exposure Investigation Report applies only to the Mossville community. The Mossville Public Health Response Workgroup may consider the feasibility of expanding the scope of the investigation.

Commentor Number 3

(3-1) The purpose section of the report should state that the investigation was limited to a small section of Mossville, the far eastern portion that is east of the KCS Railroad and did not consider the majority of the community, which resides west of the railroad. The limited section of Mossville considered is made up of the E. F. Gayle, Bel Air, and Lincoln Heights Subdivisions of Mossville.

Response: In the Methods section of the EI report, the geographical limits of the Mossville community included in the Exposure Investigation are explicitly stated.

(3-2) In the Background section of the draft report (page 1), ATSDR states "Mossville is located across the road from a large vinyl chloride monomer plant. Several flares at this facility intermittently burn unidentified waste materials. CONDEA Vista operates a manufacturing facility, adjacent to the Bel Air, E. F. Gayle, and Lincoln Heights subdivisions of Mossville, which includes a vinyl chloride (VCM) unit. There are no flares associated with the vinyl chloride unit. While the flares do exist at other units of our facility, none of them burn chlorinated hydrocarbons or any other materials, which contain chlorine. The VCM Plant does have two chlorinated compound incinerators which burn only gaseous vents from the VCM unit process. These are not hazardous waste incinerators, and no incineration of hazardous waste occurs at CONDEA Vista. Those incinerators have been sampled according to EPA methods and found to emit very low levels of dioxins and furans. These levels are less than 0.1 grams / year of total dioxin.

Response: This information was incorporated into the Exposure Investigation Report.

(3-3) The reference to black soot in the opening paragraph is based on anecdotal data, and should be more clearly noted as such. A much more likely source of soot deposition in the neighborhood is a refinery coker unit, which operates immediately southeast of the section of Mossville that was studied.

Response: The origin of the soot is unknown. The statement was deleted from the report.

(3-4) On page 2 of the draft report, the ATSDR report references the result of a study where the blood dioxin levels, of 11 residents of Calcasieu Parish was determined. It states that the individual with the highest blood serum dioxin level was a resident of Mossville. Were any of the other 10 individuals tested residents of Mossville? Where were the other residents from? What were their blood serum dioxin levels? What were the circumstances of this study and why are its results not included in this report?

Response: ATSDR did not conduct the study the commentor refers to. A private citizen gave ATSDR the analytical results from this study and limited demographic information for some of the participants. The data and information that ATSDR received were discussed in a previous Health Consultation, which is referenced in the Exposure Investigation Report. Copies of this report are available upon request. ATSDR's Exposure Investigation focused on Mossville and did not attempt to address possible exposures in other areas in Calcasieu Parish.

(3-4) The correct name of the Street referred to in the report as Vinyl Chloride Monomer Drive is "VCM Plant Road".

Response: The report was revised to reflect the commentor's information.

(3-5) No reason or explanation was given for the selection of the target area. The boundaries of the target area and those of an ongoing residential buyout, of part of the Mossville community as part of the settlement of a recent class action lawsuit are almost identical. This study and any future work should not be limited to this part of Mossville and should incorporate the entire Mossville community. This would give considerably more information on normal levels for the community and could provide information on sources of exposure It is inappropriate for ATSDR to construct a study that gives the appearance of supporting lawsuits and allegations resulting from those lawsuits.

Response: As stated in the EI report, the Mossville community was selected because: (1) Previous testing indicated a resident of the community had a high blood dioxin level. (2) The community is located in an area with a high concentration of chemical industries. (3) The community expressed a high level of health concern over possible exposure to environmental contamination. The selection of the EI target area was not influenced by lawsuits or property buyouts.

The Mossville Public Health Response Workgroup will discuss the feasibility of conducting additional environmental and biological testing for dioxin.

(3-6) Cigarette smoking has been identified as a source of PCDD. No mention of the smoking history of these individuals in the study has been included in the draft report. The report should include information on the smoking history of the entire group that were sampled and a comparison made between their cigarette use and dioxin levels.

Response: ATSDR did not obtain information on the smoking history of the participants. In Vietnam veterans, blood levels of 2,3,7,8 TCDD were not different in smokers vs. non-smokers. ATSDR is not aware of studies that have examined the impact of smoking on blood levels of other dioxin-like compounds. However, researchers have examined the impact of smoking on dioxin concentrations in breast milk. In one study, dioxin levels in breast milk from smokers and non-smokers were the same [H. Beck et al.; Chemosphere 25 (7-10) 1015-1020 (1992)]. In another study, dioxin levels in breast milk from smokers were reported to be lower than in breast milk from non-smokers. The authors of this study speculated that induction of metabolic enzymes in the smokers accounted for the lower dioxin levels [Furst et al.; Chemosphere 25 (7-10) 109-1038 (1992)].

(3-7) The second paragraph on page 7 states that "…in the 1980s, when dioxin exposures were likely higher than current exposures." A similar statement is in the last sentence of the fourth paragraph on the same page. This statement provides two distinct problems, if included in a scientific study. First, it is speculative as written and referenced, and should only be included in the report if it is identified as pure speculation. Second, if the statement can be determined to be true, then the identification of sources of exposure to the dioxins found become a significant problem, as the sources of the dioxin found may no longer exist.

Response: The final EI report cites references to document the statement that human exposures to dioxins have been decreasing since the 1980s. The updated comparison ranges for blood dioxin levels presented in the EI report provide further evidence for this decrease. Current body burdens of dioxin are likely the result of past as well as current exposures.

(3-8) The last paragraph on page 7 states that the source of the dioxins found in the study is not known. The section that follows discusses dioxin formation from combustion sources. The structure of this section gives the appearance that the ATSDR has concluded that the levels found were as a result of combustion. However the observed low levels of dioxin found in the soil would contradict the inferred connection expressed in this paragraph. If ATSDR has concluded the observed dioxin levels found are a result of combustion, it should be so stated in the conclusions with indication of the exposure pathway. If that conclusion has not been reached, the dioxin formation discussion should be moved to the background and the inferred connection removed.

Response: It has been well documented that the combustion of chlorinated organic materials is a major source of dioxin-like compounds in the environment. People may be exposed to dioxins released from combustion processes by inhalation of airborne dioxins, by ingestion of biota that have bioaccumulated dioxins from the environment, or by contact with dioxin contaminated environmental media (e.g., soil). ATSDR recommends that additional environmental testing be done to help determine if there are ongoing exposures to dioxin in Calcasieu Parish.

(3-9) The ATSDR should note that the study area is not in an incorporated area, not subject to open burning rules of municipalities, so yard fires, trash burning, etc. was not an uncommon occurrence in the area.

Response: The relative significance of residential trash burning as a source of environmental contamination is unknown.

(3-10) It is important to note the very low levels of dioxins found in Mossville soil. The conclusions should indicate that exposure from airborne emissions as a result of soil deposition appears to be a minimal route of exposure.

Response: The Exposure Investigation Report stated that the concentrations of dioxins detected in four soil samples do not pose a public health hazard. Air has not been tested, so ATSDR draws no conclusions as to whether inhalation exposures are a potential source of dioxin exposure.

(3-11) The 28 people tested lived in the same limited Mossville neighborhood. Additional testing needs to be done to determine if these 28 are representative of Calcasieu parish or the remainder of the Mossville community. It seems worthwhile to understand how Mossville results compare to dioxin levels in other Calcasieu Parish area neighborhoods and whether these results are above or below the area mean.

Response: The findings and conclusions of ATSDR's report apply only to the 28 individuals in the Exposure Investigation. ATSDR did not attempt to extrapolate these findings to other communities in Calcasieu Parish. Sufficient demographic data are not available to determine if the test population is representative of the entire Mossville community.

(3-12) ATSDR points out that most dioxin exposure is through the diet. It seems prudent to interview those who have been sampled, and those who will be in the future, to document dietary habits, smoking history and other lifestyle patterns. Making that information generally available (on a blind basis) will assist everyone involved to better understand the situation and formulate recommendations.

Response: In the general population, more than 90 percent of dioxin exposure is believed to be from dietary exposures. Whether this is also true for the Mossville population, particularly for those with elevated dioxin levels, has not been determined. Dioxin testing of locally grown, raised, or caught foods that are commonly eaten by residents of Mossville may help to resolve this issue. As discussed previously, the Mossville Public Health Response Workgroup will discuss the feasibility of further biological or environmental testing.

(3-13) Recommendation (1) should note the environmental testing pathways which should be examined to determine the source of dioxin exposure.

Response: The Mossville Public Health Response Workgroup will discuss the feasibility of additional environmental testing. Further environmental testing could include testing of ambient air and local food items.

(3-14) Recommendation (2) should note the possible environmental exposure pathways to be identified and avoided, such as smoking, for the benefit of the concerned citizens. ATSDR already has considerable data on the possible exposure pathways from earlier studies, and should include that knowledge either in the Recommendations or as an appendix.

Response: With regard to smoking as a source of dioxin exposure, see response to comment (3-6). ATSDR has not conducted any previous studies in Calcasieu Parish.

(3-15) Recommendation (6) should note that dietary habits and lifestyle were not considered in the study to determine possible environmental sources of dioxin.

Response: With the exception of the two chicken eggs that ATSDR tested, we are not aware of any data on possible dioxin contamination of local food items. ATSDR recommends that additional testing of local food items be conducted to help determine if there are ongoing dioxin exposures from dietary components.

Commentor Number 4

(4-1) We acknowledge the importance of the Exposure Investigation (EI) conducted by ATSDR. ATSDR selected an appropriate population for this initial study and developed a report that articulates many of the strengths and weaknesses of the "EI". We believe that such studies inform readers about potential exposures that might concern member company employees, staff, near neighbors, and others in the general community. We support this type of investigation and certain other similar activities that can enhance our knowledge of potential exposures. The report is clear and gives a generally balanced presentation of the findings.

We are pleased to learn that this initial study has shown that the blood levels are far below those that might cause clinical health effects. We also note that the soil and egg data do not support an argument that there has been significant environmental exposure.

We must respond to certain conclusions and recommendations of further study related to this population that are not supported by the data. The recommendations in the "EI" and the follow-up actions are not consistent with ATSDR's published criteria for conducting an exposure investigation. We believe that this study demonstrates that further investigation into this population is not necessary. Excess exposure to dioxin-like compounds has not been observed. Therefore, efforts to identify sources of dioxin exposure or actions to minimize exposure to environmental sources of dioxin are probably neither appropriate or needed.

Response: ATSDR concludes that there is evidence for increased exposure to dioxins in some residents of Mossville. The basis and rationale for this conclusion is discussed in the EI report. Therefore, it is prudent public health policy to identify sources of excess dioxin exposure and reduce exposure from those sources.

(4-2) We have some concerns about the methodology used to estimate risk in the "EI". ATSDR has adopted the toxicity equivalency factors (TEFs) approach. It must be acknowledged that there are many uncertainties regarding the ability to add PCB, chlorinated dibenzo-p-dioxin (CDD) and chlorinated dibenzofuran (CDF) toxicity. These chemicals are assumed additive through a single common mechanism, binding to the Ah receptor. Although that mechanism is generally accepted for some of the toxicity of TCDD and other highly active organochlorines, the TEF approach is, at best, a very rough approximation. The endpoints that have been used include are derived from different studies, with different endpoints of toxicity, and different species (van den Berg et al., 1998). The estimates are relatively imprecise. A recent reevaluation adjusted the TEF for specific congeners by as much as an order of magnitude.

The "EI" notes that the TEF values have been reassessed recently by an international body (van den Berg, 1998). Nevertheless, ATSDR used the old value so that they could be compared to the older studies that are being used as a reference point (ATSDR, 1999; ATSDR, 1998). Although it is understandable that they used the old numbers, it should be noted that some of the TEFs changed by an order of magnitude, and others were withdrawn altogether. This helps demonstrate the imprecision of this particular tool.

Response: ATSDR agrees that the TEF approach assumes a common mechanism of action for dioxin-like compounds. This approach has widespread acceptance both nationally and internationally, even though it is recognized that the TEFs are approximate rather than precise values.

The EI report does not estimate the risk for exposure to a CDD/CDF mixture. TEFs were used so that concentrations of dioxin congeners in different individuals and populations could be summed for comparative purposes.

Table 1 of the EI report compares the concentrations of individual dioxin congeners in Mossville residents and a comparison population. When comparing individual congeners, TEFs are not a factor. These data demonstrate that many of the dioxin congeners are elevated in Mossville residents, irrespective of TEFs.

(4-3) With such imprecision and uncertainty in the toxicity assessment, the potential differences in exposure reported in the "EI", if any, are simply insignificant. The data does not support a conclusion that the dioxin TEF levels in this study are elevated or warrant further study. ATSDR has presented mean and maximum concentrations for the Mossville residents and compared those values to the reference means in Table 1 (ATSDR, 1999). The Mossville mean toxicity equivalency quotient (TEQ) is within the range of the reference means. There is no evidence that the TEQ exposure is elevated. Even the highest blood levels are well below those that might cause adverse health effects. As ATSDR noted, "the only confirmed health effects of dioxin exposure in humans are chloracne and transient mild hepatotoxicity" (ATSDR, 1999). Such effects are observed only at the much higher blood levels than seen in the Mossville population. As noted by ATSDR, clinical effects are unlikely (ATSDR, 1999).

Response: In the final EI report, ATSDR compared the blood dioxin test results to updated comparison values. ATSDR concludes that there is evidence for increased exposure to dioxins in some Mossville residents.

(4-4) The study intentionally selected an older population. Thus, the blood serum levels could be the result of exposures that occurred years earlier. The failure of the egg or soil samples to show significant levels of dioxin TEQs confirm that the current exposures are not elevated, although it is a limited sample size.

Response: CDDs and CDFs have long biological half- lives. Therefore, ATSDR acknowledges that past exposures to dioxins could be a significant contributor to the body burden of dioxins.

The finding that egg and soil dioxin levels were not elevated does not exclude the possibility that exposures are occurring through other pathways or food sources.

(4-5) ATSDR has listed four criteria that it applies to decide when to conduct an exposure investigation (

    1. Whether it is likely that people have been exposed to a contaminant,
    2. Whether we need more information on the exposure,
    3. Whether an exposure investigation will provide that information, and
    4. Whether that investigation will affect public health decisions.

While we appreciate the inquiry under the first criteria as to whether or not an exposure was likely (i.e., there may have been an exposure to a contaminant), the data does not support a conclusion that an exposure occurred to these residents. The other criteria are not met in the assessment of the Mossville population. Additional data are not needed for the following reasons. First, the soil and egg data do not support an argument that there has been significant environmental exposure. Second, the initial study has not shown a meaningful elevation in blood levels compared to the reference studies. Third, the study has clearly shown that the blood levels are far below those that might cause clinical health effects. Finally, additional data are not needed because the findings, even if they confirmed the findings of this report, probably will not seriously affect public health decisions.

We conclude that this study supports the conclusion that no further assessment is required for this population.


(1) The finding that egg and soil dioxin levels were not elevated does not exclude the possibility that exposures are occurring through other pathways or food sources.

(2) ATSDR concludes that there is evidence for increased exposure to dioxins in some residents of Mossville. The basis and rationale for this conclusion are discussed in the EI report.

(3) ATSDR agrees that the blood dioxin levels detected in Mossville residents have not been demonstrated to cause adverse health effects in humans.

(4) Because of uncertainties regarding the health effects of dioxin, ATSDR considers it prudent to reduce preventable excess exposures to dioxin.

Commentor Number 5

(5-1) The report could be improved by an explanation of the origins and basis of this investigation. The October 25, 1998 ATSDR Health Consultation recommended the identification of possible exposure sources of dioxin in the three individuals with elevated blood dioxin levels and implementation of measures to reduce exposures. How did the investigation of 28 Mossville residents' blood dioxin levels come to be?

Response: See response to comment (3-5).

(5-2) The first paragraph under this heading has a number of statements that should be reviewed before release:

  • "Several flares ... burn unidentified waste materials." Is this factually accurate? Waste incineration occurs but of identified materials through permits for which information exists.

  • "Residents reported that black soot from these flares deposits on vegetation on their property ." If soot was observed or sampled then this might be of importance. Maybe a separate section needs to be added to the report that summarizes resident fears and concerns. Including this kind of information in the Background section leads the reader to believe that these concerns were given enough credibility that sampling was conducted to verify concerns.

Response: The EI Report was revised to incorporate information on the flares that was provided by commentor number 3.

Health concerns raised by the residents did contribute to ATSDR's decision to conduct an Exposure Investigation.

(5-3) "The individual with the highest blood serum level (104 pg of dioxin TEQs/gram lipid ...) was a resident of Mossville. The resident ..... it is suspected ... was exposed to dioxins from an unidentified environmental source." Why did results for this individual, and not the other two individuals, necessitate more extensive study? What was the basis for the suspected environmental source?

Response: The other individuals lived in different geographical areas. Because of resource limitations, ATSDR could only study one community. The reasons for selecting the Mossville community are discussed in the response to comment (3-5).

(5-4) There were a lot of explicit and implicit questions regarding the target population: Does this group of 28 statistically represent the population of Mossville [or elsewhere?]

Response: The findings and conclusions of ATSDR's report apply only to the 28 individuals in the Exposure Investigation. ATSDR did not attempt to extrapolate these findings to other communities in Calcasieu Parish. Sufficient demographic data are not available to determine if the test population is representative of the entire Mossville community.

(5-5) Why was this size group selected?

Response: The number of participants in the investigation was limited by budgetary considerations.

(5-6) What levels of blood-dioxin concentration were needed to determine if residents of Mossville were exposed?

We recognize that much of the above could not have been quantified before the study (and that is our point with these types of questions). An accurate depiction of the intended limited scope and purpose of the 'probe' study and its limitations needs to be described to minimize misinterpretation.

Response: An Exposure Investigation is a limited investigation to assess possible human exposure to hazardous substances in the environment. When significant exposures are identified, ATSDR may conduct a larger scale health study. Such a study would incorporate considerations of sample size, the need for control groups, and other epidemiological issues.

The conclusions of this EI apply only to the population tested. Sufficient demographic data are not available to determine if the population tested is representative of the greater Mossville community.

(5-7) Were blank and duplicate samples drawn?
What QA/QC measures were used?
What was expected verses measured variance or results?

Response: The analyses were conducted by isotope dilution-high resolution mass spectroscopy. The NCEH laboratory, which conducted the analyses, runs a spiked sample after every third sample as a control. The results of the spiked sample must be within two standard deviations of the expected value or the test samples are rerun. Detailed information on QA/QC procedures including blanks and spiked samples is contained in the published methodology (D.G. Patterson et al.; Determination of Specific Polychlorinated Dibenzo-p-Dioxins and Dibenzofurans in Blood and Adipose Tissue by Isotope Dilution-High-Resolution Mass Spectrometry; Environmental Carcinogen Method of Analysis and Exposure Measurement; 299-332, 1991). Copies of this reference are available upon request.

It is not practical to collect and test duplicate blood samples because of the large volume of blood required and the cost of dioxin analyses.

(5-8) It would be helpful if a blank copy of the consent form was included in the report (many of the residents are suspicious of what really binds participants to confidentiality).

Response: ATSDR staff obtained the informed consent of the participants prior to enrolling them in the investigation. The participants were required to sign a standard consent form that was approved by ATSDR's Associate Administrator for Science. The consent form states that ATSDR may not provide individual test results to the public. A blank copy of the consent form is available upon request.

(5-9) The histogram is a good attempt to display the spread of data but it could be improved by adding the expected distribution. The differences would point out how far out of 'kilter' the Mossville results might be. We realize that statistics are not firm in the area of dioxin in humans so perhaps instead of hard lines, bands would be more appropriate. Also, the graph should use consistent x axis units.

In the final EI Report, ATSDR provides the mean, median and 95th percentile of the dioxin concentrations in a comparison population. These statistical benchmarks can be used to interpret the blood dioxin levels detected in Mossville residents.

(5-10) There needs to be a better explanation of why a 100 ppt blood dioxin level is a threshold of concern (e.g. Why not use 200 ppt as point for further study?)

ATSDR did not identify 100 ppt as a threshold of concern; it is simply a convenient demarcation point for discussion and comparative purposes.

(5-11) Does Table 1 compare to the October 1998 table?

Response: The comment refers to ATSDR's health consultation of October 16, 1998. (See response to comment 2-1.) The EI was intentionally limited to Mossville so that potential exposures that were common to residents in a small geographic area could be evaluated.

(5-12) The reference range was based on comprehensive survey of published studies which you say were carried out in the1980s. There are published studies (Patterson, D.G. et al, 1994) that were carried out in the 1990s, were these studies evaluated and compared to the 1980s studies? If currently the range is expected to be lower, which could be true, how much lower do you think it will be to make any difference in the conclusions?

Response: The Patterson study [D.G. Patterson et al.; Environ Health Perspectives, Vol 102 Suppl 1 195-204 (1994)] measured 2,3,7,8-TCDD levels in adipose tissue samples collected in 1984 or 1986 from autopsies on 28 people with no exposure histories.

Other CDDs, CDFs, and co-planar PCBs were measured in adipose tissue from only 5 individuals, one of whom was acknowledged to be above normal. ATSDR does not believe it is appropriate to use these data to define dioxin TEQ ranges in the general population.

(5-13) The reference range should be emphasized to be the range of means and not the whole distribution of the data. It will be more meaningful to compare the distribution of the reference reported values to the distribution of the 28 Mossville residents dioxin blood results. If the reference mean range is between 36 - 58 ppt, doesn't this mean that there should be some values in the higher end to calculate this average. According to Patterson, D.G. et al 1994 data, the data suggest to be log-normally distributed. Other data also showed to be log-normally distributed. In this case it is not so unusual to see some individuals in the general population to have dioxin blood levels of 3 to may be 4 times the average value. This might especially be true since the average age of Mossville participants was 58 (sic, 53). Therefore, comparing the high end values from Mossville residents to the average reference value could be criticized as inexact. We are concerned that the data does not clearly indicate whether or not individuals living in the Mossville area are unusually exposed.

Response: In the draft Exposure Investigation report, ATSDR recognized the limitations of the available dioxin reference ranges. Since the draft report was released, ATSDR has worked with the National Center for Environmental Health at the Centers for Disease Control and Prevention to review updated data for dioxin levels in United States residents. The final report has been revised to incorporate updated comparison values. These comparison values support the conclusion that dioxin levels in the EI participants are elevated.

(5-14) The inclusion of prior studies was very informative. Two studies were used as reference values, one was the German study and the other is the Tifton, Georgia study. The German study which you indicate showed that the average dioxin TEQ level was 41 ppt compares very well with the Schecter (1991) study on a pool of blood samples collected from Germans. Schecter (1991) found that the level of dioxin in blood of Germans (41 ppt dioxin TEQs) compared very well also with a pool of blood samples collected from North America value which was 42 ppt dioxin TEQs. However, these values did not include the PCB dioxin-like compounds. Does the German study and the number you cited include the PCB dioxin-like compounds?

Response: The Tifton study included co-planar PCBs in the dioxin TEQs; the German study did not. More recent data from Germany (1996) indicated an average blood dioxin level of 16 ppt (O. Papke; Environ Health Perspectives 106 (2) 723-731 (1998)).

(5-15) For the Tifton, Georgia study, the Patterson D.G. (1994) study was also done on 28 individuals from Atlanta Georgia. His data fits a log-normal distribution which showed that individuals could have values 3 to 4 times the average value.

Response: The Patterson study measured 2,3,7,8-TCDD levels in adipose tissue samples collected in 1984 or 1986 from autopsies on 28 people with no exposure histories. In their statistical analyses, the authors excluded one individual "whose levels were obviously above normal U.S. background levels." Of the 27 remaining 2,3,7,8-TCDD values, the maximum value was 2.3 times the mean.

CDDs, CDFs, and co-planar PCBs were measured in adipose tissue from only 5 individuals, one of whom was acknowledged to be above normal. No conclusions can be drawn from such a limited sample size.

(5-16) The first conclusion may not be statistically supportable with the evidence available from only 28 samples. Would the following clarifications be consistent with ATSDR's understanding of the information?

The average concentration of dioxin TEQs in blood samples from the participants was within the expected range for the reference population. The level was found at the upper end of the reference range but this may have been a result of such factors as the increased average age of the participants, diet, as well as environmental factors. The current reference range could be lower but the impact of these factors could result in the same conclusion.

Response: ATSDR's interpretation of the results is provided in the EI report.

Commentor Number 6

Commentor Number 6 submitted a document that contained numerous graphs that are an inherent part of the comments. Therefore, a photocopy of this document is included. ATSDR's responses to the comments are provided at the end of the document.

The commentor's photocopy was not available in electronic format for conversion to HTML at the time of preparation of this document. To obtain a hard copy of the document, please contact:

Agency for Toxic Substances and Disease Registry
Division of Health Assessment and Consultation
Attn: Chief, Program Evaluation, Records, and Information Services Branch, E-56
1600 Clifton Road NE, Atlanta, Georgia 30333

(6-1) ATSDR agrees that the dioxin congener profile of the mean and median values from the Mossville population and from the Mossville resident with the highest dioxin TEQ level have similarities.

(6-2) The EI report provides evidence that dioxin levels in humans have been decreasing since the 1980s. Since the NHATS samples were collected in 1987, these data are not an appropriate reference range for recently obtained results. In addition, the NHATS data were for adipose tissue, not blood. For the CDDs and CDFs, the ratio of blood plasma to adipose tissue levels were reported to vary from 0.83 to 2.0 [A. Schecter et al.; Chemosphere 20 951 (1990)]. Therefore, adipose tissue data from 1987 are not appropriate reference standards for blood samples collected in 1998.

As discussed in the EI report, the concentrations of some of the dioxin congeners (e.g., the tetra, penta, and hexa dioxins) are elevated relative to the comparison population. Therefore, ATSDR does not agree with the statement that the dioxin fingerprint of Mossville residents is the same as the national average.

(6-3) ATSDR explicitly states that the source of dioxin exposure in the Mossville residents is not known -- hence our recommendation for further environmental testing. Furthermore, the route of exposure is not known -- i.e., whether residents are directly exposed to environmental dioxins in air, soil, etc. or whether exposure is from eating contaminated biota.

The EI Report notes that blood levels of 12378D and 1234/678D were elevated in some Mossville residents. Known sources of these compounds, as reported in the literature, are listed. The EI report cites published references to substantiate the statement that these compounds have been detected in the combustion products of PVC materials, as well as from other sources.

(6-4) ATSDR is not convinced that the dioxin congener fingerprint of the source and the dioxin fingerprint in the blood of an exposed person would be the same. Dioxin congeners may degrade in the environment at different rates (weathering) or transported through the environment at different rates. In addition, dioxin congeners may be taken up and bioaccumulated by biota at different rates. For example, the biotransfer factors for dioxins in soil to chicken eggs varies 24-fold among the CDDs and 44-fold among the CDFs [F. Schuler et al.; Chemosphere 34 (4) 711-718 (1997) ]. In this study, the lower chlorinated dioxins and furans were more readily bioaccumulated that the higher chlorinated species. Similarly, the transfer of dioxins in soil or air to cow's milk is highly dependent on the specific congener [P. Furst et al.; Chemosphere 27 1349-1457 (1993)].

In addition, variability in the human absorption, metabolism, and excretion of dioxin congeners may further blur the fingerprint. For example, the estimated blood half-lives of the various CDDs and CDFs in humans varies from 3.0 to 19.6 years [ D. Flesch-Janys et al.; J Toxicol Env Health 47 363-378 (1996)].

Therefore, the dioxin fingerprint in the source may not match the dioxin fingerprint in a human blood sample. This would be particularly true if humans were indirectly exposed to dioxins from eating contaminated biota.

(6-5) Air sampling for dioxin would provide the most direct and unequivocal evidence to address the question of whether there is a current airborne source of dioxins in the community.

(6-6) Response: In the draft Exposure Investigation report, ATSDR recognized the limitations of the available dioxin reference ranges. Since the draft report was released, ATSDR has worked with the National Center for Environmental Health at the Centers for Disease Control and Prevention to develop updated dioxin comparison levels. The text of the final report has been revised to incorporate updated comparison levels.

(6-7) ATSDR is not aware of any data to support the speculation that blood dioxin levels as high as 329 ppt can be found in the background population without any unusual local source.

In the revised EI report, ATSDR compared the blood dioxin test results from Mossville residents to comparison levels derived from U.S. residents who were tested in the past several years. The mean, median, and 95th percentile concentrations of dioxins in the EI participants and comparison populations were reported so that statistical comparisons could be made.

(6-8) This statement reiterates issues that were previously discussed in comments 6-2, 6-3, and 6-4.

(6-9) ATSDR agrees that additional environmental sampling is needed to identify possible source(s) of dioxin.

ATSDR has released data that can be disclosed in accordance with our Confidentiality Agreement with the participants.

Commentor Number 7

(7-1) I am pleased that ATSDR has come into my back yard and found exposure and your recommendation to identify and stop the sources.

I would like to see a study done on the employees of the plants in question and find out why there has been an epidemic of heart bypass operations and so many early deaths.

Response: ATSDR has no authority to investigate exposures to hazardous substances in the workplace. Health concerns over occupational exposures should be referred to the Occupational Safety and Health Administration or the National Institute of Occupational Safety and Health.

(7-2) I would like the Agency for Toxic Substances and Disease Registry to realize the chemical exposure is Calcasieu Parish wide and not only in Mossville. I want all the people to be put into a safe atmosphere and environment.

I am extremely grateful that ATSDR has come to Calcasieu.

Response: ATSDR is aware that other communities in Calcasieu Parish are concerned over possible exposures to environmental contamination. ATSDR has solicited community participation in the Mossville Public Health Response Workgroup, which will discuss how to address these concerns.

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