SECTION 1
INTRODUCTION
This is a report on the baseline activities and findings from the analyses of data collected from members of the 1,1,1-Trichloroethane (TCA) Subregistry of the Volatile Organic Compounds (VOCs) Registry. The VOCs Registry is part of the National Exposure Registry (NER), which were created and are being maintained by the Agency for Toxic Substances and Disease Registry (ATSDR).
In 1988, the policies and procedures proposed for the NER were reviewed extensively by several committees composed of independent scientists, state representatives, representatives of other federal agencies, and other interested people. The revised policies and procedures were published in the NER Policies and Procedures Manual (1). The VOCs Registry was one of the first registries to be established as part of the NER program. The NER currently contain four substance-specific registries (VOCs, Dioxins, Heavy Metals, and Radioactive Substances) (see Figure 1-1). The VOCs Registry currently contains three chemical-specific subregistries (Trichloroethylene, Benzene, and TCA).
The goals and objectives of the TCA Subregistry reflect those of the NER; specifically, the TCA Subregistry will be used to facilitate epidemiologic or health studies and surveillance and will provide information that can be used to assess the effects of exposure to TCA on a general population. In addition, the TCA Subregistry will enable federal, state, and local officials to provide exposed persons with timely, relevant information about TCA exposure, potential adverse effects related to that exposure, preventive measures, and therapeutic advances that were not understood when the TCA Subregistry was established. The methodology used to accomplish these goals follows the multisite concept.
The Policies and Procedures Manual (1) describes in detail all policies, procedures, and operational details pertinent to establishing the TCA and other subregistries of the NER. Specific topics from the policies and procedures document are reiterated in this report, where necessary, for clarity.
The objective of this report is to present the results of the statistical analyses comparing the reporting rates of registrants for specific health outcomes with national norms. The report is the third of a set of ongoing reports and publications that will summarize the latest VOCs Registry findings for specific subregistries and suggest specific hypotheses for future research. The research will focus on these and potentially other residential populations that have experienced similar exposures to VOCs. This report highlights some health outcomes and predictive variables that should be considered for analysis during future epidemiologic or health studies related to TCA exposure.
Section 2 of the report reviews the rationale for the selection of TCA as a primary contaminant for the NER and provides a discussion of the information available at the time of its selection on the toxicity of TCA, based on the related epidemiologic and toxicologic studies, as well as information on data gaps that subregistry-generated information could fill. In addition, Section 2 presents general information on the number of National Priorities List sites where TCA was found in 1995, as well as a detailed discussion of the site meeting the criteria for inclusion in the TCA
Figure 1-1.-Design of the National Exposure Registry.
Subregistry. Section 2 also provides descriptive and summary information on the environmental data and period of exposure.
This report provides an overview of the characteristics and health status of registrants who took part in this baseline effort. Section 3 includes a summary of the TCA Subregistry registrants data. Section 3 also includes a comparison of the TCA Subregistry data with national survey data files for smoking habits, demographic characteristics, and reported rates of adverse health outcomes; Section 4 includes the same information for the TCA Subregistry data collected for the first followup. Section 5 summarizes the findings of the report and discusses the findings in relationship to the published literature. Section 6 states the conclusions of the analysis of the TCA Subregistry baseline data and outlines future activities related to the TCA Subregistry.
SECTION 2
BACKGROUND OF THE 1,1,1-TRICHLOROETHANE SUBREGISTRY
SELECTION OF 1,1,1-TRICHLOROETHANE AS A PRIMARY CONTAMINANT
In keeping with the National Exposure Registry (NER) procedures for substance selection (1), the factors that led to the selection of 1,1,1-trichloroethane (TCA) included the prioritization of TCA on the Hazardous Substance Priority List (2); the ubiquitousness of TCA in the environment; the published evidence of TCA toxicity in worker populations and in toxicologic studies; and the paucity of information on low-level, long-term exposures to TCA. Each of these factors suggested that the NER could contribute significantly to the detection of an excess in adverse human effects, should they exist, following long-term, low-level exposure to TCA in the environment.
Environmental Information
TCA is a synthetic compound that is released to the environment as a result of anthropogenic activity (3). TCA is used as a solvent for adhesives (including food packaging adhesives), metal degreasing, and textile processing and is used in the manufacturing of pesticides, cutting fluids, aerosols, lubricants, cutting oil formulations, drain cleaners, shoe polishes, spot cleaners, printing inks, and stain repellents. TCA is emitted during use of items prevalent in the average home, such as liquid detergent, wallpaper glue, carpets, spray and solid insecticides, carpet glue, and chlorine bleach scouring powder.
TCA-contaminated groundwater was found at 59% (n = 380) of the National Priorities List (NPL) sites with TCA (Figure 2-1). Of these sites, 42% (n = 161) used private well systems, 19% (n = 72) had municipal systems, and 39% (n = 147) used both private and municipal systems to provide residents with drinking water (4).
The available literature indicates that TCA is toxic to humans and animals. A brief synopsis of the literature available in 1992, based on the Toxicological Profile for 1,1,1-Trichloroethane (3) follows. A more detailed discussion of the updated literature is given in Section 4.
Clinical symptoms associated with high-level exposure to TCA that have been reported in humans include hypotension, diarrhea and vomiting, central nervous system (CNS) depression, and dermal and ocular irritation (3). Mild hepatic effects can also occur in humans. Deaths have been attributed to cardiac arrhythmia and respiratory failure secondary to CNS depression. Effects reported in humans that also occur in animals include hypotension, cardiac arrhythmia, CNS depression, mild hepatic effects, and dermal irritation. Effects that have been observed in animals but not investigated in humans include mild developmental effects.
Immunological effects of TCA have not been reported in humans (Figure 2-2), and have not been studied extensively in animals (Figure 2-3). Acute inhalation exposures had no effect on survival from a bacterial pathogen challenge in mice. Histological evaluations of immune system tissues from rats and mice (including the lymph nodes, thymus, and spleen) have not revealed any lesions attributable to TCA exposure. However, more extensive studies of immune function would be required to adequately evaluate the immunotoxic potential of TCA in humans.
Figure 2-1.-Number and types of TCA sites in 1995.
Developmental effects of TCA in humans have not been reported. Mild embryotoxic effects were reported in rats and rabbits exposed to high concentrations of TCA by inhalation. Effects included decreased fetal weights, increased minor soft tissue and skeletal abnormalities, and delayed ossification. For one of these studies, developmental defects could have been associated with the significant maternal toxicity observed. Neither an inhalation study using a lower concentration nor a drinking water study found any developmental effects.
Reproductive effects of TCA in humans have not been reported. Histological evaluation of reproductive organs and tissues from male and female rats and mice revealed no lesions attributable to TCA exposure. More sensitive tests are required before a full evaluation of the potential for reproductive effects in humans can be made.
Although TCA was mutagenic in a few assays with Salmonella, induced chromosomal aberrations in a Chinese hamster ovary cell assay, and was positive in mammalian cell transformation assays, the existing genotoxicity data are largely negative. In addition, there is a possibility that positive results were produced by the stabilizers and not by TCA itself. Therefore, a firm conclusion regarding the genotoxic potential of TCA in humans is not possible.
Evidence for or against an association between exposure to TCA and cancer in humans has not been reported. Among animals, no effects were found in an inhalation study at exposure levels up to 1,500 parts per million (ppm). The results of an oral study indicated the TCA might have produced an increase in the occurrence of immunoblastic lymphosarcoma in rats. However, the biological and statistical significance of the results of the study were questionable because of the limitations of the study design.
There is also limited information on the role of TCA metabolites in the toxicity of the parent compound. Reactive metabolites are important in the carcinogenicity of other chloroethanes. Binding to deoxyribonucleic acid (DNA), which is correlated with carcinogenicity in chlorinated
Figure 2-2.-Existing information on human health effects of 1,1,1-trichloroethane (3).
Figure 2-3.-Existing information on health effects of 1,1,1-trichloroethane in animals (3).
ethanes, was weak in both in vivo and in vitro tests. Even weak binding, however, indicates an ability to interact with DNA. Cell biotransformation tests were positive for TCA. The results of these assays might have been confounded by the presence of stabilizing agents, however.
In summary, the TCA Subregistry was created in response to the pervasiveness of TCA at the nation's waste sites; the relative lack of information on human health outcomes associated with long-term, low-level exposures to TCA in drinking water supplies; and the knowledge of adverse health outcomes among people experiencing different types of TCA exposure (for example, short-term exposures at high concentrations). Subsequent knowledge concerning TCA exposure and human health, available since the selection of TCA and the establishment of the TCA Subregistry of the VOCs Registry and discussed in Section 4, further supports the establishment and maintenance of a TCA Subregistry.
SELECTION AND DESCRIPTION OF THE TCA SUBREGISTRY SITE AND POPULATION
The site selection process used to develop subregistries for the NER is described in detail in the Policies and Procedures Manual (1).
During the site selection process, 380 potential sites were identified as having TCA as a contaminant of groundwater. After reviewing the sites with respect to specific criteria, the site described in this section was selected as most appropriate for inclusion in the TCA Subregistry. The criteria for selection included documentation of exposure levels and duration of exposure, identification and estimated size of the exposed population, identification of susceptible sub-populations, and identification of the number and levels of secondary contaminants. Sites where state and local officials supported development of the subregistry were given priority. Although not a criterion for selection, preference was given to sites with available hydrogeologic information in order to better characterize registrants' exposure.
One site was selected for inclusion in the TCA Subregistry of the VOCs Registry. The name of the site-as provided for in the Comprehensive Environmental Response, Compensation, and Liability Act of 1980 (5), amended by the Superfund Amendments and Reauthorization Act of 1986 (6)-is the Vestal Water Supply Well #1-1 site in Vestal, New York. It should be noted that this site used a public water system; therefore, for the purpose of this report, exposures for all registrants at the site were considered to be the same. Following is a summary of the site included in the TCA Subregistry of the VOCs Registry. This summary includes a brief description of the source of contamination, the period of documented contamination, and the contaminants detected during sampling.
Description of the TCA Subregistry Site
Vestal Water Supply Well #1-1 is located in Water District #1 of the Town of Vestal, Broome County, New York (Figure 2-4). The well was the primary of three wells (Figure 2-5) that supplied drinking water to approximately 9,000 residents in the western part of the town, as well as to residents in Water Districts #2, #8, and #9.
Figure 2-4.-Location of Vestal, New York.
Figure 2-5.-Vestal, New York, water districts.
In August 1978, the U.S. Environmental Protection Agency (EPA) conducted a community water supply survey of 66 systems in the state of New York. The Vestal system was included in this survey. TCA was detected in the distribution system at 1,600 parts per billion (ppb) (Table 2-1). On January 31, 1980, Well #1-2 was sampled for halogenated organic compounds; trichloroethylene and 1,1,1-trichloroethane were discovered. Because of the high level of halogenated compounds, in June 1980 the town began pumping Well #1-1 to waste in the nearby Susquehanna River. EPA determined that this action captured the contaminant plume and kept the contaminants from reaching the other two supply wells in the area. The site was placed on the National Priorities List in December 1982.
Table 2-1.—Contaminants for Well #1-1, Vestal, New York.
| Contaminant | Maximum Level (ppb)* |
|---|---|
| 1,1,1-Trichloroethane | 1,600.0 |
| Trichloroethylene | 470.0 |
| Benzene | 27.0† |
| Tetrachloroethylene | 6.1 |
| Chloroform | 35.0 |
| Dibromochloroethane | 7.0 |
| 1,1,2-Trichlorofluoromethane | 4.0 |
| Freon | 15.0 |
| Vinyl chloride | 2.0 |
| 1,1-Dichloroethylene | 8.0 |
| 1,1-Dichloroethane | 81.0 |
| 1,2-Dichloroethylene | 82.0 |
| 1,2-Dichloroethane | 1.8 |
| Trichloroethane | 86.0 |
| Chloroethane | 7.0 |
*ppb - parts per billion.
†The first reading for benzene was 43 ppb. However,
it was noted that benzene coeluted with trichloroethylene;
therefore, this reading was not included.
Businesses in the area east of Well #1-1 were implicated in the contamination. These businesses were gasoline service stations, a dry cleaner, automobile sales and services, automobile body shops, and small manufacturing plants. Although the exact businesses have changed in the last 35 years, the nature of the commercial community has not. Commercial development in the area began between 1944-1955, with the current level achieved between 1968-1977.
Given the information available on groundwater flow and industrial growth in the area, a conservative date for the start of contamination in Well #1-1 is 1969. The duration of exposure, and thus the time period of interest for the Subregistry, would be from January 1, 1969, until May 31, 1980.
On-Site Activities
In the spring of 1991, data collection for the TCA Subregistry began with face-to-face interviews with potential Subregistry members from the Vestal Well #1-1 site. People who were then residing or had previously resided at the addresses served by the TCA-contaminated well were considered to be "potential" registrants.
Preparations for on-site data collection included a mailing to potential registrants. The mailing contained a question-and-answer brochure with information about ATSDR and the NER. At that time, benzene was also of concern; therefore, the mailout also contained a chapter from the ATSDR Toxicological Profile for Benzene, which summarized all that was known about the association between benzene exposure and adverse health outcomes (7). This information packet was sent to residents before a public meeting about the NER and the data collection effort. Soon after the public meeting, interviewers began contacting residents at the designated household addresses in search of eligible Subregistry members.
For each Subregistry included in the NER, the selection process uses definitions of eligibility and exposure that incorporate three key components: (1) valid information that indicates the presence of the contaminant(s) of interest in one or more of the media of interest; (2) evidence, for a given individual, of an appropriate route(s) of exposure; and (3) evidence of indicated transmission from the contaminated source to the potential registrant during the period of exposure as verified by that individual. For example, in the case of the TCA Subregistry, the well water had to have been tested and validated for the presence of TCA. Also, the well water had to have been the sole source of water for drinking, bathing, or cooking for all individuals at the site residential addresses. Finally, a registrant would had to have reported using the TCA-contaminated well water for drinking, cooking, or bathing during the exposure period.
Each eligible person or a proxy for that person was administered the TCA Subregistry baseline questionnaire, which included a set of questions about health conditions that the registrant currently had or had ever had and that had been either confirmed or treated by a health practitioner. Each time the respondent reported the presence of one of these health conditions, a set of follow-up questions was asked about the date of first treatment by a physician, current treatment, prescribed medication, and hospitalization related to the condition.
Information on the identity of past residents at an exposure address was solicited from current residents and other knowledgeable persons (such as neighbors). Any names provided were traced by a professional tracing service. Individuals located were contacted by telephone to determine if they were eligible to participate; if so, their participation was solicited and, if they agreed, the core questionnaire was administered at that time.
Information on deceased eligible persons was obtained from a knowledgeable proxy (usually the spouse) and a death certificate was requested from the appropriate state office. Information on the cause of death, along with other pertinent information, is being extracted from the death certificates and coded as copies of death certificates are obtained from the states.
For the Vestal site, information was obtained for 3,665 persons (3,204 living and 461 deceased). The response rate (the percentage of those eligible who were contacted and agreed to participate) was 97%.
SECTION 3
COMPARISON OF THE TRICHLOROETHANE (TCA)
SUBREGISTRY DATA AND NATIONAL DATA
REGISTRANT DESCRIPTIVE DATA
Tables 3-1 and 3-2 contain information about the characteristics of the Trichloroethane (TCA) Subregistry members. The total TCA Subregistry has 3,665 members; 3,204 were alive at time of baseline data collection, 461 were deceased. Only those living at the time of the baseline interview are included in the analyses reported in this document. The response rate (the percentage of those eligible who were contacted and agreed to participate) was 97%. For the deceased registrants, the Agency for Toxic Substances and Disease Registry (ATSDR) is currently obtaining death certificates; when this effort is completed, pertinent information will be abstracted, a mortality file constructed, comparisons using the appropriate national norms made, and the results published.
Of the total living population (n = 3,204), 3,166 persons (98.8%) answered white to the race question; 38 persons (1.2%) answered other than white. The percentage of nonwhite people was significantly less than that for the comparison group-the 1990 National Health Interview Survey (NHIS) population. The analyses are, therefore, restricted (for both the Subregistry and NHIS files) to those answering white to race (n = 3,166). No further analyses were performed on the nonwhite groups because of the small numbers and the potential for violating the confidentiality of the respondents.
The exposure period in Vestal ended in 1980; therefore, all eligible people in the Vestal community were older than 10 years of age and, consequently, all registrants are 10 years of age or older. Table 3-1 indicates that, at baseline, 52% of the living registrants were female. Approximately 45% of the registrants were between the ages of 25 and 44 at the time of the baseline interview; 5% were between the ages of 10 and 17.
Among registrants who were 19 years of age or older, 94% had a high school diploma. Slightly more females than males had not completed high school (6% versus 5%). A higher percentage of males (40%) than females (29%) had completed college or some post-college education. About three-fourths (72%) of the male registrants who were 19 years of age or older were currently employed either full- or part-time, compared with 60% of the females.
Table 3-2 provides data on registrants' use of tobacco products. Of the registrants 18 years of age or older, 19% reported being current cigarette smokers (that is, they had smoked at least 100 cigarettes during their lifetime and smoked at time of data collection). Slightly more males than females (21% versus 18%) were current cigarette smokers. Fewer females than males (42% versus 52%) reported having ever smoked cigarettes (that is, were current smokers or had smoked at least 100 cigarettes in their lifetime). Overall, a small number of the registrants reported ever using other tobacco products: pipes (8%), cigars (7%), snuff (2%), and chewing tobacco (3%). Smoking rates for registrants are compared with national data later in this section.
Table 3-1.—Descriptive data for living registrants (white only).
| Variable | Males | Females | Total | |||
|---|---|---|---|---|---|---|
| N | (%) | N | (%) | N | (%) | |
| Number | 1,519 | (48) | 1,647 | (52) | 3,166 | |
| Age (years) £17 18-24 25-44 45-64 65-74 ³75 R* | 76 142 707 343 170 79 2 | (5) (9) (46) (23) (11) (5) (<1) | 71 128 709 401 198 133 7 | (4) (8) (43) (24) (12) (8) (1) | 147 270 1,416 744 368 212 9 | (5) (8) (45) (23) (12) (7) (<1) |
| Education (³19 years of age) Not high school graduate High school graduate Some college College graduate or more D† R* | 73 429 356 568 - 1 | (5) (30) (25) (40) - (<1) | 94 587 426 444 2 2 | (6) (38) (27) (29) (<1) (<1) | 167 1,016 782 1,012 2 3 | (6) (34) (26) (34) (<1) (<1) |
| Occupational status (³19 years of age) Currently employed Previously employed Never employed Missing | 1,032 391 4 - | (72) (27) (<1) - | 925 594 35 1 | (60) (38) (2) (<1) | 1,957 985 39 1 | (66) (33) (1) (<1) |
| Place of residence (at time of interview) On site Off site D† R* | 608 907 3 1 | (40) (60) (<1) (<1) | 738 907 2 - | (45) (55) (<1) - | 1,346 1,814 5 1 | (42) (57) (<1) (<1) |
| Type of interview Subject Proxy | 1,408 111 | (93) (7) | 1,525 122 | (93) (7) | 2,933 233 | (93) (7) |
*R-Refused to answer question.
†D-Response was don't know (usually proxy reporting).
Table 3-2.—Tobacco use for registrants 18 years of age or older (white only).
| Variable | Males | Females | Total | |||
|---|---|---|---|---|---|---|
| N | (%) | N | (%) | N | (%) | |
| Cigarettes Current smoker Ex-smoker Never smoked R* | 297 447 696 1 | (21) (31) (48) (<1) | 285 379 905 - | (18) (24) (58) - | 582 826 1,601 1 | (19) (27) (53) (<1) |
| Pipe Current smoker Ex-smoker Never smoked Other D† R | 21 223 1,194 - 2 1 | (2) (16) (83) - (<1) (<1) | - - 1,567 2 - - | - - (100) (<1) - - | 21 225 2,761 2 2 1 | (<1) (8) (91) (<1) (<1) (<1) |
| Cigars Current smoker Ex-smoker Never smoked Other D R | 41 176 1,221 - 2 1 | (3) (12) (85) - (<1) (<1) | - - 1,568 1 - - | - - (100) (<1) - - | 41 176 2,789 1 3 1 | (1) (6) (93) (<1) (<1) (<1) |
| Snuff Current user Ex-user Never used Other D R | 15 37 1,387 - 1 1 | (1) (3) (96) - (<1) (<1) | - - 1,568 1 - - | - - (100) (<1) - - | 15 37 2,955 1 2 1 | (<1) (1) (98) (<1) (<1) (<1) |
| Chewing tobacco Current user Ex-user Never used Other D R | 26 61 1,352 - 1 1 | (2) (4) (94) - (<1) (<1) | - - 1,568 1 - - | - - (100) (<1) - - | 26 62 2,920 1 1 1 | (<1) (2) (97) (<1) (<1) (<1) |
*R-Refused to answer question .
†D-Response was don't know (usually proxy reporting).
RATIONALE FOR THE COMPARISON OF THE TCA SUBREGISTRY DATA WITH NATIONAL DATA
This section includes comparisons of TCA Subregistry data with data from national surveys. These comparisons are consistent with NER objectives and goals, as stated in the Policies and Procedures Manual (1), which are to provide a preliminary assessment of the extent to which TCA Subregistry members might have an excess of adverse health conditions and to generate-rather than test-hypotheses about TCA exposure and health outcomes.
In addition to a comparison of the TCA Subregistry health data with national health data norms, this section includes comparisons of registrant demographic and smoking data with national data. The comparisons of demographic characteristics and smoking rates indicate the extent to which TCA Subregistry members are similar to the general population. These comparisons are important because both demographic characteristics and smoking are known to be correlated with or are probable causes of many adverse health conditions.
TCA Subregistry data were compared with data obtained from the 1990 NHIS (8). Subsets of the NHIS data were used in the comparisons with demographic, smoking, and health data components of the TCA Subregistry. The NHIS data were selected for comparison with the TCA Subregistry data for the same general reasons that the NHIS was selected for comparison with the NER. The NHIS is an appropriate comparison population because it is a subset of the residential, noninstitutionalized U.S. population, the population of interest for comparisons of the health status of the NER members. As of 1985, a stratified, multistage cluster sample design was used in the NHIS to obtain a representative sample of the target population; this information was used to create representative national norms. The NHIS, similar to the NER, consists of self-reported data that were obtained using face-to-face interviews.
Also, because of the similarity of the data collection instrument and methods used by the NHIS and the NER, the NHIS data were appropriate for the calculation of selected prevalence and incidence statistics and could be used for exploratory comparison with NER data for health outcomes. The weighting factors (9) provided by the National Center for Health Statistics (NCHS) were applied when using the data. The 1990 NHIS file used for selected comparisons in this report included approximately 155,000 respondents.
As was discussed in Section 2 of this report, members of the TCA Subregistry sample are located primarily in the Northeast United States (New York); others are located throughout other regions of the country. The influence of region on reported disease outcome rates for the TCA Subregistry, a concern when comparing the Subregistry reporting rates with the national rates reflected by the NHIS numbers, was explored. ATSDR's review of the NHIS regional rates for selected outcomes found no definitive evidence indicating that the overall health status of persons located in the Northeast region differed significantly from that of the general U.S. population. Rates for selected reported chronic conditions for the geographic regions Northeast, Midwest, South, and West (all races) are listed in an NCHS publication (8). Very few of the reported health rates were highest for the Northeast region and none were related to conditions reported in excess by the registrants. Therefore, differences between the TCA Subregistry file and the NHIS file were not expected to be and did not appear to be the result of regional differences.
METHODS OF DESCRIPTIVE VARIABLE COMPARISONS
Demographic Characteristics
The NHIS and TCA Subregistry samples were compared in terms of four demographic characteristics-sex, age, race, and education level-as well as cigarette smoking rates. Each of these variables is a potential correlate of health status.
Sex
The distribution of the male-female ratio was assessed on an age-specific basis. The proportion of males and females in each age category was based on the NHIS data and compared with the corresponding proportions in the TCA Subregistry. Each age-specific proportion in the TCA Subregistry was compared with the corresponding proportion in the NHIS by testing that the binomial proportion was equal to a specified theoretical value. No statistically significant differences were found between the two files for this variable.
Age
The descriptive comparisons of age used a 10-category measure. The regression analyses in this section involved a regrouping of age categories. An eight-category measure of age (combining the lower two and upper two groups) was used because of the sparsity of positive reports in some of the age strata. For the TCA Subregistry file, there were no registrants less than 10 years of age and the number of categories was reduced to seven.
It should be noted that because the health outcome analyses involved summarizing age- and sex-specific comparisons rather than analyzing age-adjusted summaries, whether the age distribution of the NHIS file matched the age distribution of the TCA Subregistry file was not directly relevant unless distribution differed within the age groups.
Race
Race is an established correlate of socioeconomic status (10) and health status (11). National data indicate that nonwhites have lower rates for cigarette smoking (12). For these reasons, race is a potential control variable for the comparisons of health status and smoking rates. However, as was discussed at the beginning of this section, there are too few nonwhites in the TCA Subregistry to use race as a variable; all analyses were restricted to registrants responding white to the race question.
Education Level
For education level (the highest level attained as reported by a respondent), the descriptive analyses included comparisons in which education level was measured as a seven-category ordinal variable (that is, 0 through 5 years, 6 through 8 years, 9 through 11 years, 12 years or the equivalent of a high school diploma, 13 through 15 years or some college, 16 years or the equivalent of a college degree, and 17 or more years).
For the regression analyses, education attainment was collapsed into four groups: 0 through 11 years, 12 years, 13 through 15 years, and 16 or more years. Because education is difficult to interpret as a surrogate for socioeconomic status for school-aged children, analyses involving adjustments for education were restricted to adults (19 years of age or older).
Cigarette Smoking
Rates for current and past smoking behaviors were compared across sex, age, and education attainment categories. A current smoker ("current rate") was defined as anyone who reported being a smoker at the time of the interview, and who had smoked at least 100 cigarettes in his or her lifetime. Past smoking behavior ("ever" rates) was assessed by calculating the rates for people who had ever smoked at least 100 cigarettes during their lifetime. People who had ever smoked included both current and ex-smokers. For the NHIS, only one adult per household was asked the smoking-related questions; for the NER, all adults were asked. This lack of comparability precluded using smoking as a factor in the model in the statistical analysis.
METHODS OF COMPARING HEALTH OUTCOMES
Question Comparability
TCA Subregistry and NHIS data were compared for health conditions reported by respondents. Such comparisons were preceded by an assessment of the comparability of NHIS and TCA Subregistry health condition questions. The questions about health conditions in these two surveys differed in three respects: restrictions on the source of diagnosis; the time frame of occurrence or treatment; and, in some cases, the wording of the health condition. A discussion of each potential source of variation in health condition questions follows. The NHIS health-related questions are presented in Appendix A; the TCA Subregistry health-related questions are in Appendix B.
Source of Diagnosis
TCA Subregistry questions about health conditions specified that the source of diagnosis had to have been a "physician or other medical provider". This qualification was intended to minimize self-diagnoses or the biased reporting of health problems by registrants who might have had a greater awareness of health because of their known exposure and publicity related to the exposure. The NHIS questions did not include any type of qualification concerning the source of diagnosis. Therefore, if all other factors were equal or similar, an increased reporting by NHIS respondents when compared with the registrants might be expected. The increases would be expected to be greater for health conditions often self-diagnosed (for example, arthritis, hearing impairment, and some respiratory problems).
Time Frame
As was the case for all components of the NER, the TCA Subregistry baseline questions about health conditions asked about diagnoses of or treatment for conditions from the point of birth through the date of the interview ("Has a physician or other medical provider ever told you/SUBJECT that you/he/she/ had or treated you/SUBJECT for CONDITION?"). Only one time frame was addressed: ever had (registrant's lifetime). Respondents who reported "yes" to this question were also asked whether the registrant was ever treated for the condition, when the registrant was first treated for the condition, and whether the registrant was currently being treated for the condition.
The NHIS questionnaire included questions that focused on three time frames-ever had the condition, had the condition within the last 12 months, or currently had the condition. With the exception of heart disease, only one time frame was used to create a response rate for any given health condition. The NHIS data for heart disease rate reflects a composite of responses to heart-related questions that were asked in both the "ever had" and "12-month" time frames. The NHIS questionnaire asked whether respondents had ever had the heart conditions rheumatic, congenital, or coronary heart disease; angina pectoris; myocardial infarction; or any other heart attack. The NHIS questionnaire further asked whether in the last 12 months respondents had had a damaged heart valve; tachycardia or rapid heart beat; heart murmur; or other heart trouble. In addition, for some heart-related questions, a positive response was discarded if the respondent did not answer positively to one or more other selected questionnaire items (13). A comparable response rate could not be created for the heart-related questions in the NER file; therefore, a comparison to national norms could not be made for the heart condition variable.
For the other health conditions, the time frames were standardized to make the NHIS and TCA Subregistry rates directly comparable. Table 3-3 provides a comparison of NHIS and TCA Subregistry questions in terms of the time frame for each health condition. One NHIS health condition question, the effects of a stroke, was asked and the rate calculated in the context "have you ever had". The questions and time frames for the Subregistry and NHIS matched on this condition.
Eleven of the NHIS questions were asked in the time frame "within the last 12 months". For hypertension, the NHIS 12-month response rate was calculated using the "ever had" positive responses; however, the positive response was retained in the file only if the respondent also answered positively to one or more of nine other selected questionnaire items (13). This additional restriction might have reduced the NHIS response rate for this condition. For these 12 health conditions (see Table 3-3), the TCA Subregistry time frames for comparison were adjusted. In the TCA Subregistry, a health condition was defined as occurring "within the last 12 months" if (1) the reported date of first treatment was within the 12 months preceding the interview or (2) the subject was receiving treatment at the time of the baseline interview. This adjustment could have resulted, however, in an underestimation of these 12 conditions for TCA Subregistry data for the following reason. A year or more before the baseline interview, a registrant might have been told that he or she had (or was treated for) one of these 12 health conditions, but was not being treated at the time of the interview. If so, such a registrant would not have been included in the rates for these 12 health conditions.
Three health conditions in the NHIS questionnaire were asked about in terms of the time frame "do you now have". These conditions were speech impairment, hearing impairment, and mental
Table 3-3.—Comparison of time frames for health condition questions.
| (TCA Subregistry Conversion from "ever had") | NHIS* Time Frame for Condition | ||
|---|---|---|---|
| "ever had" | "in the last 12 months" | "now have" | |
| "Ever had" (same) | Stroke | ||
| "In the last 12 months" ("Ever had" and "currently have" or date of first treatment within last 12 months) | Cancer, rash, anemia, kidney disease, urinary tract disorders, ulcer, liver problems, asthma, respiratory problems and allergies, diabetes, arthritis, hypertension | ||
| "Now have" ("Ever had" and "currently have") | Speech impairment, hearing impairment, mental retardation | ||
*National Health Interview Survey
retardation. The time frame for the comparable TCA Subregistry health conditions was adjusted by counting only registrants who reported that they were "currently receiving treatment" for one of these three conditions. Again, if all other factors were equal or the same, an increased reporting by the NHIS respondents when compared with the TCA registrants would have been expected.
Health Conditions
TCA Subregistry and NHIS questions were also compared in terms of the phrasing of health conditions. As Table 3-4 indicates, some health conditions matched exactly, others did not. An ATSDR panel of scientists and physicians determined matches for the TCA Subregistry health conditions and specific NHIS conditions (ICD-9 codes [14], or NHIS condition recodes [8]).
The nine health conditions in Class A of Table 3-4 either matched exactly or the TCA Subregistry version was inclusive of the NHIS version. That is, the NHIS wording of the health condition and the NHIS classification of the condition in the recodes were the same as or paralleled closely the corresponding TCA Subregistry item. As Table 3-4 indicates, nine health conditions were in Class A. Class B included seven health conditions that did not match as closely, but were considered to be sufficiently similar for the purposes of the NHIS and TCA Subregistry comparisons.
In addition to the heart disease outcome, for six other health conditions on the TCA Subregistry questionnaire there were no parallel items in the NHIS questionnaire. These conditions pertained to symptoms including "frequent periods of fatigue or tiredness"; "frequent periods of nausea"; "seizures, tremors, spells, or epilepsy"; "weakness or paralysis or numbness in the arms or legs"; "frequent periods of anxiety, nervousness, or depression"; and "frequent or severe headaches."
Unlike some of the national health surveys (15), environmental studies commonly ask about symptoms as well as health outcomes. Data on these symptoms, while not directly comparable with
Table 3-4.—Comparison of the Trichloroethane (TCA) Subregistry and National Health Interview Survey (NHIS) health questions.
| Q#* | Wording in TCA Survey | National Health Interview Survey Definition | NHIS Chronic Recodes† | ICD-9§ |
|---|---|---|---|---|
| Class A¶ | ||||
| 6 | High blood pressure (hypertension) | Essential hypertension Hypertensive heart disease Hypertensive renal disease Hypertensive renal and heart disease | C508 | 401-05 |
| 8 | Kidney disease | Kidney stones Kidney infections Other kidney trouble | C409-11 | 592 590 581-3 593 |
| 10 | The effects of stroke | Cerebrovascular disease | C509 | 430-38 |
| 14 | Liver problems | Liver disease, including cirrhosis | C302 | 571-2 573.0, .3-.9 |
| 15 | Asthma, emphysema, or chronic bronchitis | Same | C601-2 609 | 490-1 492 493 |
| 16 | Other respiratory allergies or problems such as hay fever | Hay fever Allergic rhinitis without asthma | C603 | 477 |
| 17 | Diabetes | Same | C403 | 250 |
| 22 | Hearing impairment | Deaf - both ears Other hearing impairment | C203-4 | X05 X06-9 |
| 25 | Mental retardation | Same | C208 | X19 |
| Class B** | ||||
| 3 | Cancer | Some cancers queried directly; other ascertained indirectly | 140-208 | |
| 5 | Skin rashes, eczema, or other skin allergies | Psoriasis Dermatitis Dry (itching) skin | C112-4 | 696 690-94 698.9 |
| 7 | Anemia or other blood disorders | Anemia of any kind | C404 | 280-85 |
| 9 | Urinary tract disorders, including prostate trouble | Disorders of the bladder (other than bladder infections) Diseases of prostate | C413-14 | 594.1 596 600-602 (except 601.4) |
Table 3-4.—Continued.
| Q#* | Wording in TCA Survey | National Health Interview Survey Definition | NHIS Chronic Recodes† | ICD-9§ |
|---|---|---|---|---|
| Class B** | ||||
| 13 | Ulcers, gallbladder trouble, or stomach or intestinal problems | Gallbladder stones Gastric, duodenal, or peptic ulcer Abdominal hernia Gastritis and duodenitis Disease of esophagus Other functional disorders of stomach or digestive system (not indigestion) Enteritis and colitis Spastic colon Diverticula of intestines Other stomach and intestinal disorders (not constipation) | C301 C303 C303-8 C310-3 C315 | 574 530-7 550-3 555 556 558 560-562 564.1 569 787 |
| 18 | Arthritis, rheumatism, or other joint disorders | Arthritis Rheumatism Gout Sciatica (and lumbago) Intervertebral disc disorders Bone spur and tendinitis Disorders of bone or cartilage Bursitis | C101-7 C109 | 711.0, .9 712.8-.9 714-16 720.0 721 729.0 724,.2-.3 722, 726 727.0, .2-.9 730.0-.3, .9 731.0, .2 732-3 |
| 20 | Speech impairment | Stammering and stuttering Other speech impairment | C205-6 | X10 X11 |
| No Match | ||||
| 19 | Rheumatic fever, heart disease, or other heart problems | Rheumatic fever Ischemic heart disease Heart rhythm disorders Congenital heart disease Other select heart diseases | C501-7 | 390 392-9 410-4 427.0-.6, .8-.9 785.0-.2 745-6 415-7 420.9 421.0, .9 422.9 423-4 425.0-.5, .9 426, 428 429.0-.6, .8-.9 |
*Question in TCA Subregistry questionnaire.
†Chronic Recodes, NHIS, Public Use Data Tape Documentation (9).
§ICD-9 is the International Classification of Diseases, 9th Revision, World Health Organization (WHO) (14).
¶Class A indicates questions match exactly or closely.
**Class B indicates questions are similar.
NHIS data, are important in assessing the impact of the environment on health and will be useful for comparisons with past and current epidemiologic environmental studies, as well as for future longitudinal studies. Symptom response rates were compared in intrafile exposure groups.
The TCA Subregistry questionnaire was used to record information on all types of cancer via an open-ended question. The NHIS questionnaire, however, was used to obtain direct information on only some types of cancers, such as skin, stomach, intestinal, colon, rectal, lung, breast, and prostate cancer; information on other cancers was obtained indirectly from the respondent through information on hospital stays, doctor visits, and restricted activity. The NHIS question is worded, "In the last 12 months, did anyone in the family have ... cancer?" The time frame restriction and the possible restriction on the types of cancers reported makes this comparison with the TCA registrant data questionable and the interpretation tenuous.
Statistical Analysis of Health Data
The statistical analyses performed treated the NHIS population as a standard population and applied the age- and sex-specific prevalence or period prevalence rates obtained from the NHIS data to the corresponding age- and sex-specific denominators in the TCA Subregistry. The observed age- and sex-specific numerators for the TCA Subregistry were compared with the expected numerators based on the NHIS rates.
This one-sample approach ignored sampling variability in the NHIS data because of the large size of the NHIS database relative to the TCA Subregistry data file. Treating the NHIS versus TCA Subregistry comparison as a two-sample problem might have resulted in a dramatic underestimation of the variability associated with the TCA Subregistry data if any pooled variance estimates were used.
For the NHIS data set, methods established by the NCHS for estimating rates were used (9). That is, the complex sampling design of the NHIS was accounted for when computing health condition rates. Numerators for a given sex-age stratum were computed by summing the cross product of the "condition weight" and the "basic final weight" for people who were asked the appropriate "condition list" and responded positively for the condition of interest. Because the presence of cancer could be ascertained from several sources within the NHIS questionnaire, stratum-specific numerators were computed by summing the "basic final weight" for all people with cancer. Denominators were obtained from the NHIS "person" records by summing the "basic final weight" for all people in a particular stratum.
All health outcomes were analyzed in the following manner. Taking the NHIS as the standard population, weighted age- and sex-specific prevalence or period prevalence rates were constructed. These "standard" rates were applied to the corresponding TCA Subregistry denominators to obtain expected counts in each age and sex stratum. Standardized relative risks-the ratios of observed-to-expected age- and sex-specific counts-were modeled using Poisson regression in the Generalized Linear Interactive Modeling program (13). The Poisson regression approach is described in Breslow and Day (16). In the Poisson regression analysis, the null model was specified as log(observed) = log(expected) + grand mean. By adding terms for the age and sex effects to the null model and computing likelihood ratio statistics (by subtracting deviances of nested models), the homogeneity of the stratum-specific ratios was assessed; that is, it was determined whether the overall relative risk or the age-, sex-, or age, sex-specific ratios must be presented. Confidence intervals for the observed-to-expected ratios (collapsed at the appropriate level) were generated using exact methods; the observed counts were assumed to follow the Poisson distribution.
To take education into account, each analysis was repeated for adults (aged 19 years or older) using age-, sex-, and education-specific rates. Problems arose with the inclusion of all factors in the model; numerous cell sizes were very small or zero. In some cases, the model did not converge; in others, the zero cells made the results suspect and interpretation tenuous. Therefore, for most outcomes, the inconclusive models were not considered valid and the results are not reported here.
Statistical Analysis of Cancer Data
For the cancer health outcome, cancer incidence data from the National Cancer Institute's Surveillance, Epidemiology, and End Results (SEER) (17) program and NHIS data were used to generate expected numbers of events for comparison with the TCA Subregistry observed numbers. The SEER data can be used to generate rates that are strictly a measure of incidence (new cases in a particular year) and include all reported cancers. To make the TCA Subregistry database comparable and to generate similar rates for comparison, the year of first treatment was used as the date of onset or the year of "new case."
Both the TCA Subregistry and the SEER program are complete enumerations for data on an entire population. In the first case, the TCA Subregistry is the population of citizens with documented environmental exposure to TCA; in the latter case, SEER is the population of all (invasive) cancer cases in the 10 geographic areas constituting the SEER study area. Neither involves probability-based sampling. Thus, comparisons that were made are descriptive rather than inferential in nature and lend themselves directly to deterministic decision making. The sparsity of the data for specific cancers in each age category, particularly the younger age groups, precludes statistical comparisons for specific cancers or even for specific age groups. The rates for total cancers by sex and year reported were calculated. No statistical comparisons were made; the observed and expected values are provided.
RESULTS OF DESCRIPTIVE COMPARISONS
This section provides a discussion of the comparability of descriptive data for the TCA Subregistry file and the NHIS file. The results of this section were used to plan the subsequent analyses of the health outcome data. That is, the results were used to determine what variables were appropriate to include as covariates in modeling the health outcome comparisons.
Demographics
Race
In the NHIS sample, 18.0% of the participants were nonwhite. In the TCA Subregistry sample, 1.2% (n = 38) of the registrants were nonwhite. Given this difference in the proportion of nonwhites and the diversity of races reported among those reporting race as nonwhite in the TCA Subregistry, all nonwhite participants from the NHIS and TCA Subregistry data were excluded from the analysis reported in this and subsequent sections of the report. The statistical analyses were performed on the 3,166 living, TCA-exposed, white registrants. The small number and diversity of the nonwhite subpopulation (and also the potential for violating confidentiality) precluded conducting any analyses of this subpopulation.
Age
Table 3-5 shows the percentage of people in each age group. As expected, the percentages in some age groups were affected by the timing of data collection relative to the exposure period. For example, the percentage of people in the 17 years of age or younger group was less for the TCA Subregistry than for the NHIS sample; there were no registrants in the group 0 through 9 years of age. This result is consistent with ATSDR's knowledge about the demographics of the TCA site. The exposure period ended more than 10 years before data collection and precluded the eligibility of young children (that is, children born after the exposure period ended). Table 3-6 provides a comparison of the age-specific sex distribution of males in the TCA Subregistry and NHIS samples (the proportion of females can be calculated as one minus the proportion of males), and the corresponding p values for the differences between the TCA Subregistry and NHIS proportions. Table 3-6 indicates that the proportion of males (and females) did not differ statistically significantly between the TCA Subregistry and NHIS samples for any of the age groups examined. Nine of the registrants refused to answer this question (2 males and 7 females); therefore, the sample size is decreased by 9 when age is a factor in the statistical analyses.
Table 3-5.—Comparison of National Health Interview Survey (NHIS) and Trichloroethane (TCA)
Subregistry population age groups (white only).
| Age Group (Years) | NHIS | TCA Subregistry | |
|---|---|---|---|
| % of Total | Number | % of Total | |
| All | 100.0 | 3157* | 100.0 |
| £4 | 7.2 | 0 | 0.0 |
| 5 - 9 | 7.1 | 0 | 0.0 |
| 10 - 17 | 10.4 | 147 | 4.7 |
| 18 - 24 | 9.8 | 270 | 8.6 |
| 25 - 34 | 17.2 | 645 | 20.4 |
| 35 - 44 | 15.5 | 771 | 24.4 |
| 45 - 54 | 10.6 | 409 | 12.9 |
| 55 - 64 | 9.0 | 335 | 10.6 |
| 65 - 74 | 8.0 | 368 | 11.7 |
| ³75 | 5.2 | 212 | 6.7 |
*9 refused to answer this question.
Table 3-6.—Comparison by age group of percentage of white males for the Trichloroethane (TCA)
Subregistry and National Health Interview Survey (NHIS) populations.
| Age (Years) | TCA Subregistry | NHIS* | p value† |
|---|---|---|---|
| 0-4 | --- | 0.52 | --- |
| 5-9 | --- | 0.52 | --- |
| 10-17 | 0.52 | 0.51 | p = 0.92 |
| 18-24 | 0.53 | 0.49 | p = 0.24 |
| 25-34 | 0.50 | 0.50 | p=0.94 |
| 35-44 | 0.50 | 0.50 | p=0.84 |
| 45-54 | 0.47 | 0.49 | p=0.51 |
| 55-64 | 0.44 | 0.48 | p=0.26 |
| 65-74 | 0.46 | 0.45 | p=0.58 |
| ³75 | 0.37 | 0.37 | p=0.94 |
*Cell values are proportions of total males in age group.
†The p values are two-sided.
Education Level
The summary statistics for education attainment are provided in Table 3-7. For both males and females, the overall difference in the age-specific education level of people aged 19 years or older was statistically significant at the p £0.05 level. These overall differences were attributable to a smaller proportion of TCA Subregistry members in the 0 through 11 years of education category (especially among younger adults), and a greater proportion who had at least a college degree compared with the NHIS sample. These findings indicate that the TCA Subregistry participants had attained a higher level of education than the NHIS population. This difference could modify the comparison of health outcome rates in that the TCA Subregistry population might be expected to have fewer outcomes related to lower socioeconomic factors. Therefore, not including the factor in the statistical model would not have increased the number of positive findings.
Cigarette Smoking
Table 3-8 provides comparative information on current and past cigarette use for people 18 years of age or older. Smoking rates are indicated for TCA Subregistry members, all NHIS respondents, and the NHIS Northeast regional subpopulation. As can be seen, the smoking rates-
Table 3-7.—Education level attained for Trichloroethane (TCA) Subregistry and National Health
Interview Survey (NHIS) populations (white, 19 years of age or older).
| Age (Years) | NHIS Education Level (years) | TCA Subregistry Education Level (years) | ||||||
|---|---|---|---|---|---|---|---|---|
| 0-11 | 12 | 13-15 | 16+ | 0-11 | 12 | 13-15 | 16+ | |
| Males and Females | ||||||||
| All | 19.5 | 38.9 | 20.8 | 20.8 | 5.6 | 34.1 | 26.3 | 34.0 |
| 19 - 25 | 15.1 | 40.9 | 32.3 | 11.8 | 3.4 | 29.4 | 45.4 | 21.8 |
| 26 - 45 | 11.8 | 39.0 | 22.6 | 26.7 | 1.3 | 27.0 | 28.7 | 43.0 |
| 46 - 64 | 21.1 | 40.6 | 17.1 | 21.1 | 4.4 | 41.3 | 20.4 | 33.8 |
| ³65 | 39.8 | 34.7 | 12.7 | 12.7 | 18.9 | 45.8 | 17.3 | 18.0 |
| Males | ||||||||
| All | 19.5 | 36.6 | 20.3 | 23.7 | 5.1 | 30.1 | 25.0 | 39.8 |
| 19 - 25 | 16.3 | 42.2 | 30.8 | 10.7 | 3.9 | 28.6 | 40.9 | 26.6 |
| 26 - 45 | 12.3 | 37.4 | 21.8 | 28.5 | 1.4 | 24.9 | 26.8 | 46.9 |
| 46 - 64 | 21.6 | 35.2 | 16.8 | 26.5 | 3.2 | 33.7 | 19.7 | 43.5 |
| ³65 | 40.2 | 31.3 | 12.1 | 16.5 | 18.9 | 41.4 | 16.5 | 23.3 |
| Females | ||||||||
| All | 19.5 | 41.0 | 21.2 | 18.2 | 6.1 | 37.8 | 27.5 | 28.6 |
| 19 - 25 | 13.8 | 39.6 | 33.7 | 12.9 | 2.9 | 30.2 | 50.4 | 16.5 |
| 26 - 45 | 11.3 | 40.5 | 23.3 | 24.9 | 1.1 | 29.1 | 30.6 | 39.2 |
| 46 - 64 | 20.7 | 45.7 | 17.5 | 16.1 | 5.5 | 47.9 | 21.1 | 25.5 |
| ³65 | 39.5 | 37.2 | 13.2 | 10.1 | 18.9 | 49.1 | 18.0 | 14.0 |
Note: Education data were missing for five registrants.
Table 3-8.—Reported rates of cigarette smoking for the Trichloroethane (TCA) Subregistry and
National Health Interview Survey (NHIS) populations (white only).
| Age Group | TCA Subregistry Rates (%) | NHIS Rates (%) | |||||
|---|---|---|---|---|---|---|---|
| All | Northeast Region | ||||||
| N | Current* | Ever† | Current | Ever | Current | Ever | |
| ³18 years All Males Females | 3,009 1,440 1,569 | 19.3 20.6 18.2 | 46.8 51.7 42.3 | 25.3 27.6 23.3 | 51.7 59.8 44.2 | 23.6 25.9 21.8 | 52.0 58.8 45.9 |
| 18-25 years All Males Females | 321 168 153 | 17.1 16.7 17.6 | 25.2 23.2 27.5 | 26.8 27.8 25.8 | 38.2 38.6 37.9 | 27.6 27.6 27.6 | 39.6 37.8 41.2 |
| 26-34 years All Males Females | 594 296 298 | 24.1 24.7 23.5 | 41.1 38.2 44.0 | 29.8 31.0 28.6 | 48.8 51.4 46.3 | 28.7 30.2 27.3 | 50.6 52.6 48.7 |
| ³35 years All Males Females | 2,094 976 1,118 | 18.3 20.1 16.8 | 51.7 60.7 43.9 | 23.5 26.3 21.0 | 55.7 67.9 45.0 | 21.3 24.0 19.0 | 55.0 65.6 46.1 |
*Reported currently smoking.
†Reported having smoked more than 100 cigarettes in lifetime.
both current and ever rates-were lower for both the male and female registrants when compared with the NHIS national rates. The registrants' rates were also lower than the NHIS Northeast regional rate.
Table 3-9 shows the rates of reported current cigarette smoking by education attainment levels. As with the NHIS rates, TCA Subregistry rates (current smokers) are correlated with highest level of education attainment. It should be noted that within each age-education level, with few exceptions, the NHIS rates were either equal to or exceeded the TCA Subregistry rates. The exception was the 18 through 34 years of age group with a high school diploma-the registrant rate was slightly higher than the NHIS population rate. Since the smoking rates were lower, with minor deviations, for the TCA Subregistry population, the omission of smoking as a covariate had the potential to moderate any excess reporting of health outcomes by registrants.
Table 3-9.—Current smoking rates (percentage) by education attainment for the Trichloroethane
(TCA) Subregistry and National Health Interview Survey (NHIS) populations (white only).
| Age Group | Education Level Attained | |||||||
|---|---|---|---|---|---|---|---|---|
| No High School Diploma | High School Graduate | Some College | College Graduate* | |||||
| TCA Subregistry | NHIS | TCA Subregistry | NHIS | TCA Subregistry | NHIS | TCA Subregistry | NHIS | |
| ³18 years All Males Females | 16.2 17.4 15.2 | 31.8 36.1 28.1 | 26.4 29.5 24.1 | 29.7 33.1 27.0 | 22.0 25.1 19.5 | 23.0 25.6 20.7 | 10.9 11.6 9.9 | 13.5 14.3 12.4 |
| 18-25 years All Males Females | 17.6 15.8 20.0 | 42.2 44.1 40.2 | 31.1 31.1 31.1 | 30.4 30.1 30.6 | 12.8 12.7 12.9 | 18.7 19.7 17.8 | 6.3 7.3 4.3 | 7.8 7.9 7.8 |
| 26-34 years All Males Females | 37.5 20.0 66.7 | 48.9 49.1 48.7 | 40.7 42.0 39.5 | 38.3 41.1 35.6 | 28.2 30.9 25.8 | 25.0 26.1 24.0 | 9.4 10.1 8.7 | 11.0 11.0 11.0 |
| ³35 years All Males Females | 14.8 17.7 12.6 | 26.7 31.6 22.7 | 22.7 26.0 20.5 | 26.5 30.6 23.6 | 22.4 26.5 19.0 | 23.8 27.4 20.4 | 11.8 12.6 10.8 | 15.0 16.0 13.6 |
*May be additional years post-bachelor degree.
RESULTS OF HEALTH OUTCOME COMPARISONS
A summary of the reporting rates for health conditions for the TCA Subregistry file and the NHIS file is provided in Table 3-10 (percentages by age groups are shown in Appendix C for the TCA Subregistry). At the time of the interview, if a registrant reported having been told that he or she had cancer or had been treated for cancer by a health care provider, additional questions were
Table 3-10.—Comparison of the Trichloroethane (TCA) Subregistry and National Health Interview
Survey (NHIS) participants reporting health condition (white only).
| Condition | TCA Subregistry | NHIS | ||
|---|---|---|---|---|
| Male (%)* | Female (%) | Male (%) | Female (%) | |
| Hypertension† | 11.0 | 12.8 | 10.2 | 11.9 |
| Stroke§ | 2.0 | 2.1 | 1.3 | 1.1 |
| Diabetes† | 3.0 | 3.3 | 2.2 | 2.6 |
| Kidney disease† | 0.7 | 1.1 | 1.1 | 1.6 |
| Urinary tract disorders† | 3.8 | 4.1 | 1.6 | 1.3 |
| Skin rashes† | 6.3 | 7.8 | 5.4 | 8.2 |
| Anemia and other blood disorders† | 0.7 | 5.3 | 0.4 | 2.3 |
| Asthma, emphysema† | 4.2 | 6.1 | 8.5 | 10.5 |
| Respiratory allergies† | 6.2 | 10.6 | 9.0 | 10.3 |
| Stomach problems, ulcers† | 4.1 | 6.4 | 6.3 | 8.9 |
| Liver problems† | 0.2 | 0.6 | 0.3 | 0.3 |
| Arthritis† | 5.1 | 10.6 | 14.0 | 19.5 |
| Mental retardation¶ | 0.1 | 0.2 | 0.7 | 0.5 |
| Speech impairment¶ | 0.1 | 0.2 | 1.1 | 0.7 |
| Hearing impairment¶ | 2.8 | 2.6 | 12.6 | 8.3 |
*Percentage of subpopulation (white only) reporting positively.
†Indicates time frame is "last 12 months."
§Indicates time frame is "ever had."
¶Indicates time frame is "now have."
asked about the type(s) of cancer. Although multiple types of cancers might have been reported, only one primary type of cancer was assigned to each registrant. The summary table entries and data analysis are based on the reported primary cancers; the number of secondary cancers is also included in the tables. A summary of the TCA Subregistry population's reporting rates for specific cancers (total population and by sex) is shown in Table 3-11 for the "ever had" time frame and Table 3-12 for the "within the last 12 months" time frame. The "within the last 12 months" time frame
Table 3-11.—Summary of the Trichloroethane (TCA) Subregistry reporting rates for cancer (primary
site), "ever had" time frame (white only).
| Cancer > | Sex | Total | |||||||
|---|---|---|---|---|---|---|---|---|---|
| Male | Female | ||||||||
| N* | % | N* | % | N* | % | ||||
| None | 1,438 | 94.7 | 1,535 | 93.2 | 2,973 | 93.9 | |||
| Lip, oral, pharynx | 1 | <0.1 | 0 | 0.0 | 1 | <0.1 | |||
| Digestive system | 9 | 0.6 | 13 | (1) | 0.8 | 22 | (1) | 0.7 | |
| Respiratory system | 4 | (1) | 0.3 | 3 | (1) | 0.2 | 7 | (2) | 0.2 |
| Skin | 33 | (4) | 2.2 | 33 | (2) | 2.0 | 66 | (6) | 2.1 |
| Breast | 0 | 0.0 | 19 | (3) | 1.2 | 19 | (3) | 0.6 | |
| Genital organs | 18 | (3) | 1.2 | 34 | (2) | 2.1 | 52 | (5) | 1.6 |
| Urinary organs | 3 | 0.2 | 2 | 0.1 | 5 | 0.2 | |||
| Lymphatic tissues | 3 | 0.2 | 2 | 0.1 | 5 | 0.2 | |||
| Leukemia | 2 | (1) | 0.1 | 1 | < 0.1 | 3 | (1) | 0.1 | |
| Other | 8 | (1) | 0.5 | 5 | (1) | 0.3 | 13 | (2) | 0.4 |
| Total cancers | 81 | (10) | 5.3 | 112 | (10) | 6.8 | 193 | (20) | 6.1 |
*The numbers in parentheses are number of reported secondary sites.
(Table 3-12) is comparable to the NHIS time frame; the 12-month rates were used in the statistical comparisons of the data files.
Controlling for Age and Sex
Table 3-13 provides a summary of the results of the NHIS and TCA Subregistry file comparison using Poisson regression analysis. For each health outcome, the table indicates the likelihood ratio statistics with the associated degrees of freedom and p values for the effects of age (categorized into eight levels) and sex, based on a model containing age and sex. The residual deviance and the associated degrees of freedom are also given as a global lack-of-fit measure for this model, which specifies multiplicative effects of the age (i) and sex (j) ratios Oij/Eij. For each outcome, the age- and sex-specific numerators Oij were obtained from the TCA Subregistry data,
Table 3-12.—Summary of the Trichloroethane (TCA) Subregistry reporting rates for cancer (primary site), "within last 12 months" time frame (white only).
| Cancer | Sex | Total | ||||||
|---|---|---|---|---|---|---|---|---|
| Male | Female | |||||||
| N* | % | N* | % | N* | % | |||
| None | 1,483 | 97.6 | 1,608 | 97.6 | 3,091 | 97.6 | ||
| Lip, oral, pharynx | 0 | 0.0 | 0 | 0.0 | 0 | 0.0 | ||
| Digestive system | 3 | 0.2 | 3 (1) | 0.2 | 6 | (1) | 0.2 | |
| Respiratory system | 3 | 0.2 | 3 (1) | 0.2 | 6 | (1) | 0.2 | |
| Skin | 15 | (1) | 1.0 | 12 | 0.7 | 27 | (1) | 0.9 |
| Breast | 0 | 0.0 | 7 (1) | 0.4 | 7 | (1) | 0.2 | |
| Genital organs | 6 | 0.4 | 10 | 0.6 | 16 | 0.5 | ||
| Urinary organs | 2 | 0.1 | 1 | <0.1 | 3 | 0.1 | ||
| Lymphatic tissues | 1 | <0.1 | 1 | <0.1 | 2 | 0.1 | ||
| Leukemia | 2 | (1) | 0.1 | 0 | 0.0 | 2 | (1) | 0.1 |
| Other | 4 | 0.3 | 2 | 0.1 | 6 | 0.2 | ||
| Total cancers | 36 | (2) | 2.4 | 39 (3) | 2.4 | 75 | (5) | 2.4 |
*The numbers in parentheses are the numbers of reported secondary sites.
while the expected numerators Eij were based on the suitably person-weighted age- and sex-specific ratios from the NHIS data. For the purpose of detecting structure in these age- and sex-specific ratios, a significance level of 0.05 was adopted.
As is shown in Table 3-13, the model was adequate and neither age nor sex was a statistically significant predictor in the models for the health outcomes speech impairment; kidney disease; skin rashes; mental retardation; cancers; and asthma, emphysema, or chronic bronchitis (p > 0.10). For the health outcome respiratory allergies or problems such as hay fever, the effects of sex were statistically significant; the effects of age were not. For the outcomes hypertension, hearing impairment, and stomach problems, statistically significant variations in the ratios were seen as a function of age but not of sex. In addition to age effects, statistically significant sex effects were seen for urinary tract disorders and arthritis, rheumatism, or other joint disorders. The multiplicative model for anemia exhibited statistically significant lack of fit, suggesting that the effects of age
Table 3-13.—Summary of Poisson regression modeling.
| Condition | Age/Sex* | Sex/Age* | Residual Deviance (p value) | df | ||
|---|---|---|---|---|---|---|
| LR Stat† (p value) | df§ | LR Stat (p value) | df | |||
| Skin rashes | 6.53 (p = 0.37) | 6 | 2.07 (p = 0.15) | 1 | 9.66 (p = 0.14) | 6 |
| Arthritis | 13.95 (p = 0.03) | 6 | 9.43 (p £ 0.01) | 1 | 9.68 (p = 0.14) | 6 |
| Mental retardation¶ | 5.62 (p = 0.47) | 6 | 1.83 (p = 0.18) | 1 | 1.95 (p = 0.92) | 6 |
| Speech impairment | 3.82 (p = 0.70) | 6 | 1.56 (p =0.21) | 1 | 4.91 (p = 0.56) | 6 |
| Hearing impairment | 19.61 (p £ 0.01) | 6 | 1.99 (p = 0.16) | 1 | 5.79 (p = 0.45) | 6 |
| Liver problems¶ | --- | --- | --- | -- | --- | - |
| Stomach problems, ulcers** | 13.41 (p = 0.04) | 6 | 0.89 (p = 0.34) | 1 | 3.48 (p = 0.75) | 6 |
| Anemia and blood disorders** |
5.93 (p = 0.43) | 6 | 0.01 (p = 0.93) | 1 | 39.14 (p£ 0.01) | 6 |
| Diabetes** | --- | --- | --- | -- | --- | --- |
| Kidney disease | 4.03 (p = 0.67) | 6 | 0.12 (p = 0.73) | 1 | 7.98 (p = 0.24) | 6 |
| Urinary tract disorders** | 29.32 (p £ 0.01) | 6 | 4.45 (p = 0.03) | 1 | 6.26 (p = 0.39) | 6 |
| Hypertension** | 27.66 (p £ 0.01) | 6 | 0.37 (p = 0.54) | 1 | 5.85 (p = 0.44) | 6 |
| Stroke** | --- | --- | --- | -- | --- | --- |
| Respiratory allergies | 6.92 (p = 0.33) | 6 | 10.08 (p £ 0.01) | 1 | 8.57 (p =0.20) | 6 |
| Cancer | 10.77 (p = 0.10) | 6 | 0.33 (p = 0.56) | 1 | 3.52 (p = 0.74) | 6 |
| Asthma, emphysema | 7.56 (p = 0.27) | 6 | 0.19 (p = 0.66) | 1 | 4.34 (p = 0.63) | 6 |
*Indicates order of inclusion in the model.
†LR Stat - Likelihood Ratio Statistic.
§df - degrees of freedom.
¶Indicates no model constructed.
**Indicates some infinite estimates obtained.
depended on sex for these outcomes. Because of the sparseness of the data, an adequate model could not be constructed for the liver outcome; models also could not be constructed for the outcomes diabetes and stroke.
Table 3-14 summarizes the observed and expected numbers and their ratios for each of the health conditions considered separately. The results for age- and sex-specific analyses are provided in Appendix D. For the descriptive analysis, a ratio of 0/0 was considered to be undefined. For models in which the sex effect was not statistically significant, summary estimates based on the
Table 3-14.—Summary of observed and expected health outcomes using multivariate models.
| Condition | Observed | Expected | Risk Ratio | 99% CI* |
|---|---|---|---|---|
| Arthritis, rheumatism, and other joint disorders |
253 | 693.41 | 0.37 | 0.31, 0.43 |
| Speech impairment | 4 | 21.62 | 0.19 | 0.03, 0.58 |
| Hearing impairment | 86 | 412.18 | 0.21 | 0.16, 0.27 |
| Kidney disease | 29 | 50.38 | 0.58 | 0.34, 0.91 |
| Urinary tract disorders |
125 | 58.29 | 2.15 | 1.68, 2.69 |
| Hypertension | 378 | 458.56 | 0.82 | 0.72, 0.94 |
| Respiratory allergies | 269 | 341.82 | 0.79 | 0.67, 0.92 |
| Asthma, emphysema | 164 | 296.57 | 0.55 | 0.45, 0.67 |
| Anemia and other blood disorders |
99 | 48.04 | 2.06 | 1.57, 2.66 |
| Diabetes | 101 | 99.57 | 1.01 | 0.77, 1.31 |
| Liver | 13 | 10.76 | 1.21 | 0.52, 2.37 |
| Mental retardation | 5 | 14.71 | 0.34 | 0.07, 0.96 |
| Skin rashes |