Toxic substances from coal energy: an overview.

Environmental concerns over increased coal consumption are fully justified by the past history of coal use. Although improved technology has provided some safeguards, increased utilization will require mining practices, emission control technologies, and waste disposal procedures that are not yet fully integrated into the routine use of the coal energy system. The Committee on Health and Evnironmental Effects of Increased Coal Utilization identified six critical environmental issues which are of concern: coal mine worker health and safety, reclamation of arid lands from surface mining, the health effects of coal combustion products, toxic trace elements in coal combustion wastes, acid fallout, and global effects of carbon dioxide in the atmosphere. This presentation addresses the first four of these issues.

Chemical contamination of water supplies.

Man-made organic chemicals have been found in drinking water for many years. Their numbers and varieties increase as our analytical capabilities improve. The identified chemicals comprise 10 to 20% of the total organic matter present. These are volatile or low molecular weight compounds which are easily identified. Many of them are carcinogenic or mutagenic. Chlorinated compounds have been found in untreated well water at levels up to 21,300 micrograms/L and are generally present at higher levels in chlorine-treated water than in untreated water. Aggregate risk studies for cancer are summarized. The most common sites are: bladder, stomach, colon, and rectum. Such studies cannot be linked to individual cases. However, they are useful for identifying exposed populations for epidemiologic studies. Five case-control studies were reviewed, and significant associations with water quality were found for: bladder cancer in two studies, colon cancer in three and rectal cancer in four. A large study by the National Cancer Institute found that there had been a change in the source of raw water for 50% of the persons in one area between the years 1955 and 1975. Such flaws in the data may preclude finding a causal relation between cancer and contaminants in drinking water. Large case-control and cohort studies are needed because of the low frequency of the marker diseases, bladder and rectal cancer. Cohort studies may be precluded by variations in the kinds of water contaminants. Definitive questions about these issues are posed for cooperative effort and resolution by water chemists, engineers, and epidemiologists.

Epidemiological studies of neurotoxic, reproductive, and carcinogenic effects of complex mixtures.

Neurotoxic, reproductive, and carcinogenic effects are potentially important health end points in epidemiological studies of complex mixtures, particularly when such mixtures contain volatile organic compounds or trace metals. Epidemiological studies of neurotoxicity often will require direct clinical, behavioral, and/or physiological testing of study subjects, because these effects are likely to be subtle and not identifiable as clearly defined diseases. Peripheral nervous system toxicity can be assessed by clinical neurologic examinations, by electrophysiological tests of nerve conduction, and by physiological tests of thresholds for neurosensory perception, though these tests require considerable standardization for use outside the clinical setting, and most of the available tests have not been assessed for their utility in detecting effects of neurotoxic exposures. Neurobehavioral effects of exposures to solvents, as examples of complex mixtures, have been studied widely; but batteries of tests are often used, and these have not been well standardized and are generally unfamiliar to most research investigators in this area. Recently standardized neurobehavioral test systems developed by the World Health Organization and by a U.S. group for use in field studies, show promise in detecting neurobehavioral effects at relatively low environmental exposures. Similarly, new and sensitive measures of disturbed reproductive function, such as time-to-conception and biochemical indices of early pregnancy loss, are affected by some low-concentration environmental agents; but those measures have not yet been applied to studies of complex mixtures.(ABSTRACT TRUNCATED AT 250 WORDS)

Review, discussion, and summary of epidemiological studies.

This paper reviews and summarizes the epidemiological studies presented at the Symposium on the Health Effects of Acid Aerosols. Two studies of acute episodes examined different indicators of respiratory morbidity before, during, and after the January 1985 air pollution event in western Europe. In the U.K. no increase in respiratory morbidity, as reported by a group of general practitioners, was observed, but measured concentrations of air pollutants failed to substantiate the existence of an identifiable episode. In the Federal Republic of Germany, the air pollution episode was documented and was associated with a 10 to 25% increase in several indicators of respiratory and cardiovascular morbidity, but could not be attributed to acidic aerosols as such. In two further studies, investigators related day-to-day variations in air pollution with admissions to acute care hospitals in southern Ontario for respiratory disease over a 9-year period, and with daily mortality in London from 1963 to 1972. In the study of hospital admissions, significant correlations were observed with sulfate, ozone, and SO2 pollution, but the data were insufficient to isolate the separate or combined effects of these pollutants. In the London mortality analysis, the strongest correlations were observed for sulfuric acid levels of the prior day, but prefiltering of the mortality data may have dampened the true relationship, and age- and cause-specific analyses would have been desirable. Finally two reports on chronic effects of residence in high air pollution areas have thus far made little contribution to the evidence for an adverse effect of specific pollutants.

A study of acute respiratory disease in families exposed to different levels of Air pollution in the Great Salt Lake basin, Utah, 1971-1972 and 1972-1973.

The reported incidence of acute respiratory illness in families exposed to different concentrations of air pollution was studied during two consecutive school years. The purpose of the study was to determine the effect of increased exposure to sulfur dioxide and suspended particulate matter. In each of four study communities, the mothers of approximately 250 white families were contacted biweekly to obtain information regarding the occurrence of respiratory symptoms in each family member. Annual mean ambient sulfur dioxide concentrations in one community for the three years included in the study (1971-1973) were well above the current air quality standard of 80 micrograms/m3, while in the other three communities the annual sulfur dioxide concentrations were much lower (usually less than 40 micrograms/m3). Suspended particulate matter concentrations in high sulfur dioxide community were close to the limit designated by the annual standard (75 micrograms/m3) but actual exposures in the four communities probably were not excessive. Regression analyses of the data collected showed inconsistent associations between illness rates and educational attainment of the head of household, crowding in the home, bronchitis in parents or smoking of parents. However, once the effects of these factors were removed the adjusted rates showed little association with community of residence. It was concluded that the higher concentrations of sulfur dioxide in the Utah atmosphere could not be the cause of increases in acute respiratory illness in the exposed populations.

Do waste incinerators induce adverse respiratory effects? An air quality and epidemiological study of six communities.

The purpose of the study presented here was to simultaneously measure air quality and respiratory function and symptoms in populations living in the neighborhood of waste incinerators and to estimate the contribution of incinerator emissions to the particulate air mass in these neighborhoods. We studied the residents of three communities having, respectively, a biomedical and a municipal incinerator, and a liquid hazardous waste-burning industrial furnace. We compared results with three matched-comparison communities. We did not detect differences in concentrations of particulate matter among any of the three pairs of study communities. Average fine particulate (PM2.5) concentrations measured for 35 days varied across study communities from 16 to 32 micrograms/m3. Within the same community, daily concentrations of fine particulates varied by as much as eightfold, from 10 to 80 micrograms/m3, and were nearly identical within each pair of communities. Direct measurements of air quality and estimates based on a chemical mass balance receptor model showed that incinerator emissions did not have a major or even a modest impact on routinely monitored air pollutants. A onetime baseline descriptive survey (n = 6963) did not reveal consistent community differences in the prevalence of chronic or acute respiratory symptoms between incinerator and comparison communities, nor did we see a difference in baseline lung function tests or in the average peak expiratory flow rate measured over a period of 35 days. Based on this analysis of the first year of our study, we conclude that we have no evidence to reject the null hypothesis of no acute or chronic respiratory effects associated with residence in any of the three incinerator communities.

A mortality study of employees of the nuclear industry in Oak Ridge, Tennessee.

An analysis was conducted of 27,982 deaths among 106,020 persons employed at four Federal nuclear plants in Oak Ridge, Tennessee, between 1943 and 1985. The main objectives were to extend the evaluation of the health effects of employment in the nuclear industry in Oak Ridge to include most workers who were omitted from earlier studies, to compare the mortality experience of workers among the facilities, to address methodological problems that occur when individuals employed at more than one facility are included in the analysis, and to conduct dose-response analyses for those individuals with potential exposure to external radiation. All-cause mortality and all-cancer mortality were in close agreement with national rates. The only notable excesses occurred for white males for lung cancer [standardized mortality ratio (SMR) = 1.18, 1,849 deaths] and non-malignant respiratory disease (SMR = 1.12, 1,568 deaths). A more detailed analysis revealed substantial differences in death rates among workers at the Oak Ridge plants. Evaluation of internally adjusted log SMRs using Poisson regression showed that workers employed only at Tennessee Eastman Corporation or K-25 and at multiple facilities had higher death rates than similar workers employed only at X-10 or Y-12, and that the differences were primarily due to non-cancer causes. Analysis of selected cancer causes for white males indicated large differences among the workers at the different facilities for lung cancer, leukemia and other lymphatic cancer. Dose-response analyses for external penetrating radiation were limited to a subcohort of 28,347 white males employed at X-10 or Y-12. Their collective recorded dose equivalent was 376 Sv. There was a strong "healthy worker effect" in this subcohort-all-cause SMR = 0.80 (4,786 deaths) and all-cancer SMR = 0.87 (1,134 deaths). Variables included in the analyses were age, birth cohort, a measure of socioeconomic status, length of employment, internal radiation exposure potential and facility. For external radiation dose with a 10-year lag, the excess relative risk was 0.31 per Sv (95% CI = -0.16, 1.01) for all causes and 1.45 per Sv (95% CI = 0.15, 3.48) for all cancer. The estimated excess relative risk for leukemia was negative but imprecisely determined. A preliminary dose adjustment procedure was developed to compensate for missing dose but not other dosimetry errors. Results of the analyses using the adjusted doses suggest that the effect of missing dose is an upward bias in dose-response coefficients and test statistics.

Micronuclei and other nuclear anomalies in buccal smears: methods development.

Laboratory work aimed at improving the epidemiologic utility of an innovative genotoxicity assay is described. The exfoliated cell micronucleus assay involves microscopic analysis of epithelial smears to determine the prevalence of micronucleation, an indicator of structural or numerical chromosome aberrations. While the assay holds promise for the study of epithelial carcinogens, it is hampered by the fact that exfoliated cells are moribund and undergo degenerative phenomena that can produce extranuclear objects difficult to distinguish from classical micronuclei. Modifications in the protocol were assessed in sample buccal smears from several study populations: radiotherapy patients, nonusers of tobacco, and snuff users. Refinements in micronucleus scoring criteria and the inclusion of other nuclear anomalies in the scoring system are proposed. We demonstrate that our criteria are successful in detecting excess micronucleation in positive controls. We also provide evidence that other nuclear anomalies are at least as common as micronucleation and that therefore there is the potential for extensive misclassification. Reliability was assessed in duplicate readings.

Respiratory function as measured by peak expiratory flow rate and PM10: six communities study.

This Six Communities Study conducted at six communities in southwestern North Carolina investigates the respiratory health status of residents whose households are located near an incinerator. This diary study makes it possible to estimate the daily variation of pulmonary function measured as peak expiratory flow rate (PEFR) related to 24-h mean PM10 levels, which were observed at each monitoring station placed in the six study communities, as a surrogate exposure measure of outdoor air pollution. Observations of PEFR among participants in each community were analyzed to determine how they varied according to the degree of exposure to ambient pollutants as well as to other cofactors including, sex, age, respiratory hypersensitivity, hours spent outdoors within the area of the selected community, and surrogate measures for indoor air pollution exposure (vacuum use and experience of air irritants at work). The findings revealed that respiratory hypersensitivity status is a predictor of declining PEFR. PM10 concentrations measured in each study area did not seem to be related to the variations of respiratory health as measured by PEFR. This study did not show any difference in respiratory health between subjects of an incinerator community and those of its comparison community. Even though this community-based study with free-living subjects shows negative findings on the relationship between respiratory health and PM10, it is worth noting that these findings must be interpreted cautiously because exposure estimation based on monitoring of ambient air likely results in misclassification of true exposure levels.

Estimation of particulate matter from visibility in Bangkok, Thailand.

Lack of daily data on airborne particles has been a common problem in an air pollution research. To deal with this problem, a regression model was developed to estimate daily PM10 concentration using visibility in Bangkok from 1992 to 1997, based on 1092 visibility/PM10 pair-observations on low humidity days (humidity < or = 76.5%). Visibility was significantly and inversely associated with PM10 (r = 0.71), after adjusting for minimum temperature and winter indicator variable. The R2 of the model was 0.51.

Prevalence and consequences of asthma and wheezing in African-American and White adolescents.

PURPOSE: To describe the functional consequences of health care utilization for wheezing symptoms and diagnosed asthma in a multiracial school-based population. METHODS: Wheezing symptoms and physician-diagnosed asthma were measured in 2059 eighth graders with the International Study of Asthma and Allergies in Children video questionnaire. The sample site population was 40% African-American, 53% White, and 49% girls. Thirty-two percent of the children were on the free school lunch program. Adolescents self-reported their wheezing symptoms and physician diagnosis in response to the video wheezing scenes. They also answered questions on activity limitations, school attendance, and sleep disturbances owing to their wheezing symptoms. Multiple logistic regression was used to calculate odds ratios and adjust for potential confounders. RESULTS: Nine percent of the adolescents reported physician-diagnosed asthma with current symptoms and 27% reported current wheezing with no diagnosis of asthma. Physician-diagnosed asthmatics and wheezers were 2.6 (95% confidence interval [CI] 1.9, 3.6) and 1.8 (95% CI 1.4, 2.2) times more likely, respectively, to miss school days because of wheezing symptoms than asymptomatic adolescents. Diagnosed asthmatics were 7.8 (95% CI 5.5, 11.2) times and wheezers 4.7 (95% CI 3.5, 6.1) times more likely to have sleep disturbances than asymptomatic adolescents. Diagnosed asthmatics were 49 (95% CI 30.0, 79.8) times and wheezers 4.8 (95% CI 3.0, 7.5) times as likely to report a clinic visit for wheezing than asymptomatic adolescents. African-Americans had similar prevalence of wheezing, compared with Whites, although African-Americans were 1.4 (95% CI 1.1, 1.9) times as likely to have physician-diagnosed asthma. Girls were twice as likely to report physician-diagnosed asthma and wheezing symptoms as were boys. CONCLUSIONS: Adolescents with wheezing experienced functional consequences comparable to those of adolescents with physician-diagnosed asthma. Although wheezers may have less severe asthma than diagnosed asthmatics, the functional consequences of wheezing are likely to impair school performance and limit activity.

Respiratory health effects from occupational exposure to wood dusts.

Occupational exposure to wood dusts has been well established as a cause of nasal cancer, dermatitis, and pneumonites from molds growing in wood chips. With the exception of studies on western red cedar asthma, there is a dearth of information on the respiratory toxicity of wood dust exposure. This paper reviews the clinical and epidemiologic literature and identifies the specific woods (with botanical names) and their respiratory disease correlates, including pulmonary function declines, chronic and acute symptoms, and impaired mucociliary transport.

Micronuclei in epithelial cells from sputum of uranium workers.

The cytogenetic effects of exposure to radon progeny and cigarette smoke were assessed with the exfoliated-cell micronucleus assay among 99 uranium workers. Cells with micronuclei were determined in one sputum specimen from each worker. Exposure to radon progeny and smoking habits were classified from interview data collected at the same time as the sputum specimens. Underground miners were considered exposed to radon progeny, and the other workers were considered unexposed. Neither radon progeny exposure nor cigarette smoking had any appreciable effect on the prevalence of cells with micronuclei; the crude prevalence ratios for the two groups were 1.0 (95% confidence interval 0.7-1.4) and 0.9 (95% confidence interval 0.6-1.3), respectively. The effects of radon and smoking were not confounded by each other or by age, nor were they synergistic. These findings cast doubt on the use of sputum-based micronucleus assay in epidemiologic studies of other populations exposed to occupational or environmental lung carcinogens.

Ozone exposure and daily mortality in Mexico City: a time-series analysis.

Daily death counts in Mexico City were examined in relation to ambient ozone levels during 1990-1992 for the purpose of investigating the acute, irreversible effects of air pollution, with emphasis on ozone exposure. Air pollution data were obtained from nine monitoring stations operated by the Departamento del Distrito Federal. Mortality data were provided by the Instituto Nacional de Estadística, Geografía, e Informática. Increases in numbers of deaths were positively associated with elevated air pollution levels on the same day and on the previous day. The magnitude of the increases was small but statistically significant, after Poisson regression models were used to adjust for temperature and long-term trends. In models using data for a single pollutant, the "crude" ratio for total mortality associated with an increase of 100 parts per billion (ppb)* in one-hour maximum ozone concentration was 1.029 (95% CI 1.015, 1.044). A moving average of ozone showed a stronger association (rate ratio [RR] = 1.048, 95% CI 1.025, 1.070), and excess mortality (an increase in the number of deaths, relative to the average on days with low pollution levels) was more evident for persons over 65 years of age. Separate analyses of the effect of elevated ozone for different areas of the city showed similar results, but they were not statistically significant. Other pollutants also were related to mortality. The RR was 1.075 (95% CI 0.984, 1.062) per 100-ppb increase for sulfur dioxide and 1.049 (95% CI 1.030, 1.067) per 100 micrograms/m3 increase in total suspended particulates (TSP) when these pollutants were considered in separate models. However, when all three pollutants were considered simultaneously, only TSP remained associated with mortality, indicating excess mortality of 5% per 100 micrograms/m3 increase [RR = 1.052, 95% CI 1.034, 1.072]. The excess mortality associated with TSP is consistent with that observed in other cities in America and Europe. This study provides some evidence that ozone is associated with all-cause mortality and with mortality among the elderly after controlling for long-term cycles. However, ozone levels exhibited little or no effect on mortality rates when other air pollutants were considered simultaneously. Particulate matter appeared to be an important pollutant; it independently predicted changes in mortality. Nevertheless, because of the complexity and variability of the mixtures to which people are exposed, it is difficult to attribute the observed effects to a single pollutant. The technical feasibility and scientific validity of isolating the effect of single pollutants in such complex mixtures requires further research and careful consideration. Given the large population living in and exposed to ambient air pollution in Mexico City and other metropolises throughout the world, these small but significant associations of mortality with air pollution indices are of public health concern.

Health effects of waste incineration: a review of epidemiologic studies.

There is an increasing trend toward using incineration to solve the problem of waste management; thus, there are concerns about the potential health impact of waste incineration. A critical review of epidemiologic studies will enhance understanding of the potential health effects of waste incineration and will provide important information regarding what needs to be investigated further. This study reviews the epidemiologic research on the potential health impact of waste incineration. Previous studies are discussed and presented according to their study population, incinerator workers or community residents, and health end points. Several studies showed significant associations between waste incineration and lower male-to-female ratio, twinning, lung cancer, laryngeal cancer, ischemic heart disease, urinary mutagens and promutagens, or blood levels of certain organic compounds and heavy metals. Other studies found no significant effects on respiratory symptoms, pulmonary function, twinning, cleft lip and palate, lung cancer, laryngeal cancer, or esophageal cancer. In conclusion, these epidemiologic studies consistently observed higher body levels of some organic chemicals and heavy metals, and no effects on respiratory symptoms or pulmonary function. The findings for cancer and reproductive outcomes were inconsistent. More hypothesis-testing epidemiologic studies are needed to investigate the potential health effects of waste incineration on incinerator workers and community residents.

Waste incineration and pulmonary function: an epidemiologic study of six communities.

This study investigated the chronic effects of emissions from three different waste incinerators on pulmonary function of both healthy and sensitive subjects with chronic respiratory symptoms. Participants were 8-80 years old, not currently smoking, and living in one of three communities each with an incinerator or one of three matched comparison communities. In total, 1018 subjects underwent a spirometric test once a year during 1992-1994. Exposure was assessed by three methods: living in an incinerator community; distance from the incinerator; and an incinerator exposure index, a function of the distance and direction of each subject's residence to the incinerator, days downwind, and average time spent outdoors. The results generally showed no statistically significant association between pulmonary function and these three incinerators, adjustment for gas oven/range use at home, length of residency, and smoking history in the mixed linear models. Two significant associations were that exposure to the hazardous waste incinerator in 1994 and to the municipal waste incinerator in 1993 were related to poor forced vital capacity. Sensitive subjects were not more adversely affected by incineration emissions than were hay fever or normal subjects. Possible explanations for the negative findings are low exposure levels and bias due to nondifferential misclassification of exposures.

Agricultural chemical use and congenital cleft lip and/or palate.

A case-control study utilizing vital records and ecologic, surrogate exposure measures was conducted in Iowa and Michigan. The study hypothesis anticipated an excess risk of clefts among fetuses exposed during the peak agricultural chemical use period (April through November) coincident with their first trimester of gestation. To examine this hypothesis, multiple regression techniques were used to aid identification of potential confounders; additional analyses, stratified on the potential confounders, were performed using two chemical exposure indices. The major findings of these analyses suggest: (1) an agricultural chemical effect (using the multiple exposure index) controlling for season of conception; (2) no independent effect of season of conception (thus the null hypothesis is not rejected); and (3) little chemical/season interaction. These results imply that if exposures to agricultural chemicals are, in fact, risk factors for clefts, an expanded model that accounts for multiple pesticidal exposures may be more sensitive than consideration of season of exposure, as originally hypothesized.

Acute respiratory illness in families exposed to nitrogen dioxide ambient air pollution in Chattanooga, Tennessee.

The incidence of acute respiratory illness in families in Chattanooga, Tennessee was studied in 1972 and 1973 to determine if residents of a formerly high nitrogen dioxide exposure community continued to experience a high incidence of illness after ambient air concentrations of the pollutant had been reduced substantially. Illness data were collected by telephone at 2-wk intervals and illness rates per 100 person weeks of observation were contrasted with air pollution concentrations measured no more than 3.2 km from the home. Data were contrasted by communities designated as high, intermediate, or low pollution exposure. In 1972, higher rates of respiratory illness continued to occur in the designated high pollution area. These were associated with current higher short-term concentrations of nitrogen dioxide even though the long-term mean concentrations of the pollutant were little higher than those in the low pollution area. It was not possible to attribute the excesses in illness to specific pollutants or to specific exposure periods. However, reduction of the illness rate in 1973 associated with a strike at the primary source industry that curtailed nitrogen dioxide pollution in the high exposure community suggested that the short-term exposure may be more important than long-term exposure.

The incidence and severity of acute respiratory illness in families exposed to different levels of air pollution, New York metropolitan area, 1971-1972.

The incidence and severity of acute respiratory disease was studied in families in three New York communities with different ambient levels of SO2 and particulate air pollution. Upper, lower, and total respiratory disease rates in fathers, mothers, and school children tended to be higher in the communities with higher pollution levels. Similar higher rates, however, were not observed among preschool children. Regression analyses were used to adjust rates for socioeconomic status, parental smoking, chronic bronchitis in parents, and possible indoor pollution resulting from the use of a gas stove for cooking. After these adjustments the community differences were still significant (P less than .01), for schoolchildren. The indoor pollution related to gas stoves was a significant covariate among children. The effects of smoking were inconsistent. It was not possible to attribute the higher rates observed to any specific pollutant, since both SO2 and particulate matter levels were higher in the high pollution communities, nor was it possible to attribute the excesses to current levels of exposure or to a residual effect of previous higher exposure concentrations. The fact that young children did not follow the pattern suggests the latter. It was concluded, however, that current or previous exposures to the complexity of air pollutants in New York City was at least partially responsible for increased incidences of acute respiratory disease.