Biomedical subjects
I T Higgins
Publications and source records attributed to I T Higgins.
Effect of exposures to ambient ozone on ventilatory lung function in children.
This study was undertaken to determine if the ventilatory capacity of children is affected by hourly concentrations of ozone inhaled during their daily activity. Over a 3-wk period (June-July 1987) children who were attending a summer camp in the San Bernardino mountains of California performed spirometry up to three times per day during their stay at the camp. A total of 43 children were tested a total of 461 times. Ozone, oxides of nitrogen, sulfur dioxide, temperature, and relative humidity were measured continuously. Daily average measurements of total suspended particulate and the PM10 particulate fraction (less than or equal to 10 microns) were also made. Hourly ozone concentrations at the time of testing varied between 20 and 245 ppb. Regressions of each individual's FEV1 and FVC supported the view that high ozone levels reduced these lung function parameters. The average regression coefficient for FEV1 on ozone was -0.39 ml/ppb (SEM = 0.12) and for FVC -0.44 ml/ppb (SEM = 0.15), both of which were significantly different from zero. Statistical allowance for temperature and humidity increased the magnitude of these slopes. Nitrogen dioxide never exceeded 40 ppb during the time of testing and averaged 13 ppb. Sulfur dioxide's highest measurement was 8 ppb and often was at the limit of detection. Neither NO2 nor SO2 was considered in the statistical modeling. Data were divided based on whether each subject had been exposed to levels of ozone in excess of the National Ambient Air Quality Standard (NAAQS) during the several hours previous to being tested. Exposures exceeding the NAAQS indicated a significant negative relationship between ozone and FEV1, FVC, and PEFR. Data for nonexceedance periods did not indicate this negative relationship for any of the three lung function parameters, but it could not be determined if this was due to an absence of an ozone effect or to a combination of the increased variability and decreased size of this data subset. These data indicate that lung function changes on a daily basis relate in a negative fashion to ambient ozone levels. The magnitude of the changes are small and are reversed as ambient ozone decreases.
Reduction in risk of lung cancer among ex-smokers with particular reference to histologic type.
Reduction of the risk of lung cancer as a result of giving up smoking is examined according to the number of years of cessation from smoking and the number of cigarettes that were smoked per day before quitting smoking. Patients with histologically diagnosed lung cancer from 26 hospitals in six cities in the US were compared with controls matched for age, sex, race, time of diagnosis, and hospital. Smoking habits were recorded by trained interviewers using a questionnaire. In men, a fairly consistent reduction in risk with years of cessation for each category of cigarettes per day before giving up smoking was found. In women, however, a much less consistent pattern was observed. Analysis of the data by histologic type of lung cancer showed that among women, as among men, risk was less and declined more consistently in those with Kreyberg I cancers than in those with Kreyberg II tumors. The inconsistency was seen mainly in patients with Kreyberg II cancers, which were more common among women.
Lung cancer among cigar and pipe smokers.
The effect of pipe and cigar smoking on lung cancer risk is reviewed using data from an ongoing hospital-based, case-control study of smoking-related cancers. Data from 2,085 patients with histologically defined lung cancer and 3,948 matched controls interviewed between 1977 and 1984 were analyzed. Cigar and pipe smokers experienced much lower lung cancer risks than cigarette smokers. Risk, expressed as the odds ratio in current smokers of cigarettes only, was 16.0 times that of never smokers (95% confidence intervals, 12.2 to 20.9), 3.1 times that of cigars only (1.8 to 5.6), 1.9 times that of pipes only (0.8 to 4.3), and 2.5 times that of cigars and pipes (1.0 to 6.1). Risks were high in mixed smokers of cigars, pipes, or cigars and pipes, who also smoked cigarettes, odds ratio 10.5 (7.7 to 14.4). Among pipe and/or cigar smokers only, patients with lung cancer were more likely than controls to have been long-time smokers of 5 or more cigars or 5 or more pipefuls per day and to have inhaled. The odds ratio for those smoking 5 to 9 cigars or pipes per day was 3.2 and for those smoking 10 or more units 6.7. The odds ratio of those cigar or pipe smokers who inhaled was 12.3. The proportion of Kreyberg I cancers was higher in cigar and pipe smokers than in cigarette smokers.
The effects of kaolin on the lung.
We studied the prevalence of ventilatory impairment, chest symptoms, and radiographic abnormality in a selected sample of more than 2,000 kaolin workers from east central Georgia. The presence of ventilatory impairment was related to the presence of complicated pneumoconiosis, employment in clay calcining, and cigarette smoking. In those working with calcined clay, there was an increased prevalence of abnormality of the FEV1, but not the FVC, when compared to both wet and dry processors and which could not be explained by either cigarette smoking or the presence of pneumoconiosis. The magnitude of abnormality in the calcined clay workers was, however, unlikely to lead to disabling impairment. In workers with more than 3-yr tenure, there were 90 subjects with simple pneumoconiosis and 18 with complicated pneumoconiosis, yielding an adjusted prevalence of 3.2% and 0.63%, respectively, in the sample examined. Dry processing was associated with a greater risk of developing pneumoconiosis than wet processing.
Passive smoking in childhood. Respiratory conditions and pulmonary function in Tecumseh, Michigan.
The relationship of passive smoking to respiratory conditions and pulmonary function was assessed using a cross-sectional design in the defined population of Tecumseh, Michigan. The study population was made up of 3,482 children who were 0 to 19 yr of age at the 1962-1965 examination and for whom questionnaire information was available for both parents. Nearly 62% of children in this age group were exposed at the time of examination to at least 1 parent who smoked. Passive exposure to cigarette smoke was associated with an elevated prevalence of phlegm, wheeze, asthma, and chest colds among males and wheeze, bronchitis, and chest colds among females. Using logistic regression, offspring were shown to be 1.5 to 2.0 times more likely to have a respiratory condition if both their parents currently smoked than if both parents never smoked. FEV1, and FVC among males and Vmax50 among females were significantly lower by 5% in nonsmokers 10 to 19 yr of age whose parents were current smokers compared with similar offspring of never smoking parents. Respiratory conditions were generally more frequent and the level of lung function was generally lower for males from households where only mothers smoked compared with males from households where only fathers smoked, although sample size was limited. In females similar relationships were less consistent. Differences tended to be larger and more often significant for males than for females when respiratory symptoms and illnesses were examined.(ABSTRACT TRUNCATED AT 250 WORDS)
The effects of occupation and smoking on respiratory disease mortality.
The effects of occupation and smoking on respiratory symptoms and ventilatory lung function were examined in 1957 among random samples of men 25 to 34 and 55 to 64 yr of age from 4 occupational categories (miners, foundry workers, mixed dust and chemical workers, and non-dust-exposed workers) living in an industrial English town. Mortality has been established 20 yr after the initial survey. This report focuses on the effects of smoking, lung function, and respiratory symptoms among the older men. All-cause mortality was very similar in the nondusty, foundry, and mixed dust groups, but slightly lower in the miners and ex-miners. In contrast, smokers had 2 times the death rates of nonsmokers. There was consistency in the smoking effect within each occupational group. Poor lung function and to some extent bronchitic symptoms in 1957 were predictive of mortality by 1977, regardless of smoking habits. However, the effect of symptoms in the absence of concomitant poor lung function, though consistent, was small.
Exposure to diesel exhaust emissions and the risk of lung and bladder cancer.
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Some factors influencing interobserver variation in classifying simple pneumoconiosis.
Three experienced physician readers assessed the chest radiographs of 743 men from a coal mining community in West Virginia for the signs of simple pneumoconiosis, using the ILO U/C 1971 Classification of Radiographs of the Pneumoconioses. The number of films categorised by each reader as showing evidence of simple pneumoconiosis varied from 63 (8.5%) to 114 (15.3%) of the 743 films classified. The effect of film quality and obesity on interobserver agreement was assessed by use of kappa-type analytic procedures for measuring agreement on categorical data. Poor film quality and obesity both affected agreement adversely. Poor quality films were disproportionately frequent in obese individuals, as defined by the Quetelet index. On control of film quality by stratification, the effect of obesity on interobserver profusion agreement was no longer evident.
Air pollution and lung cancer: diesel exhaust, coal combustion.
In 1946, when the causes of lung cancer were much less well understood than they are now, a meeting was held by the British Medical Research Council to review hypotheses to explain the remarkable increase in the death rates from lung cancer and to determine strategy. Stocks came away from the meeting to study the community aspects of air pollution, which he did by extending his series of correlation studies, Kennaway to conduct studies of carcinogens in the air, and Hill to carry out a study of smoking in relation to lung cancer. It is now known, of course, that cigarette smoking is by far the most important cause of lung cancer and that about a dozen occupational exposures are also established as causes of this disease. There has been continuing uncertainty about the role of general air pollution. During the past few years, this uncertainty has been compounded with anxiety that the increasing use of diesel-powered vehicles might lead to a deterioration in air quality and, with it, an increase in the incidence of lung cancer. The purpose of this paper is to assess the current role of air pollution as a factor in lung cancer and specifically the contribution of diesel exhaust emissions to the incidence of that disease.
Risk of chronic obstructive pulmonary disease. Collaborative assessment of the validity of the Tecumseh index of risk.
Predictors of chronic obstructive pulmonary disease (COPD) have been identified in the prospective epidemiologic study of the population of Tecumseh, Michigan. Risk of developing COPD within 10 yr can be estimated from a profile that includes as risk factors age, sex, cigarette smoking habits, and forced expiratory volume in one second (FEV1). The index of risk placed 63% of male incidence cases and 64% of female incidence cases in the top 10% of the risk distribution and 81% of male and 86% of female COPD cases in the top 20% of the risk distribution for Tecumseh. The validity of the Tecumseh index of risk for other populations was determined in a collaborative investigation of data collected in longitudinal epidemiologic studies in Baltimore, Boston, Framingham, Louisiana, Staveley, and Tucson. The extent to which the risk model fitted these data sets was assessed by comparing predicted (or expected) onsets of COPD in each population with observations made in each study. The predictors of COPD identified in Tecumseh were shown to be the most important risk factors in the other populations as well. The goodness-of-fit of the index was satisfactory overall. In all populations, a high risk score was associated with an increased incidence of COPD, thus confirming the predictive ability of the risk index. The Tecumseh index of risk provides a practical method for developing a risk profile from answers to standard questions and simple tests of lung function. Risks are greatest for heavy cigarette smokers with reduced lung function, lower in smokers who stop smoking or reduce their cigarette consumption, and lowest of all in nonsmokers with above average lung function.(ABSTRACT TRUNCATED AT 250 WORDS)
Epidemiological research on the relationship to exposure of diesel emissions and the development of respiratory cancer. Meeting report.
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What is an adverse health effect?
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Mortality of Reserve Mining Company employees in relation to taconite dust exposure.
Analysis of mortality among men who were employed by Reserve Mining Company from 1952 to 1976 has been carried out. Follow-up was conducted with standard methods, including searches by the Social Security Administration. Occupational exposures to dust were based on personal samples taken over the past five years by the industrial hygiene department of the company. Smoking habits were obtained by mailed questionnaires or telephone interviews. A modified life table method was used to compare death rates of the employees with those expected for white males in the state of Minnesota. Comparisons were also made with US rates for white males. The results showed that the death rates for all causes were significantly below expectation. Deaths from malignant diseases were marginally below those expected for the state. Exposures to total dust, to silica dust, or to fiber were low. There was no relationship between mortality and estimated lifetime dust exposures, nor was there any suggestion that deaths from malignant neoplasms were increased after 15 to 20 years latency. In contrast, there was a strong relationship between smoking habits and mortality from all causes, from cardiovascular diseases, and from cancer. This study does not suggest any increase in cancer mortality from taconite exposure.
The relevance in adults of air-flow obstruction, but not of mucus hypersecretion, to mortality from chronic lung disease. Results from 20 years of prospective observation.
From 1954 to 1961, pulmonary function was assessed in 2,718 British men by forced expiratory maneuvers, and mucus hypersecretion and smoking habits were assessed by questionnaires. In 20 to 25 yr of follow-up, 104 men (all of whom had smoked) died of chronic obstructive pulmonary disease (COPD). The risk of death from COPD was strongly correlated with the initial degree of air-flow obstruction. Among men with similar initial air-flow obstruction, however, age-specific COPD death rates were not significantly related to initial mucus hypersecretion, supporting the concept that air-flow obstruction and mucus hypersecretion are largely independent disease processes. A moderate relationship existed between initial mucus hypersecretion and subsequent lung cancer mortality, but it is not known whether this was due solely to a common correlation of both conditions with the effective degree of exposure of the large bronchi to causative factors such as tobacco smoke.
"Asbestos in drinking water and cancer incidence in the San Francisco Bay area".
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Level of education, level of income, and level of fatness in adults.
Socioeconomic status is systematically related to the level of fatness, and therefore the incidence of obesity, in a total community survey of nearly 5,000 adults. Among males with more than 12 years of schooling, the average thickness of 4 fatfolds is 10% greater, amounting to about 2 kg of total fat, than those with 8 years or less of education. In females, however, the opposite trend is observed, those in the higher educational group averaging 20% thinner fatfolds, or about 5.5 kg total fat, than females in the lower educational group. These findings confirm the need for standards of obesity that take socioeconomic status into account.
Epidemiology of lung cancer in the United States.
This paper has reviewed the temporal and spatial distribution of lung cancer in the United States. Some of the personal characteristics which are important determinants of this type of cancer and which need to be considered in assessing the role of environmental air pollution have also been considered. Recent studies which have attempted to relate lung cancer mortality to possible arsenic exposure or to levels of benzo[a]pyrene in different places are noted. While an urban effect is undoubted, it is still not certain that it is due to carcinogenic pollutants in the air. Although there may be exceptional areas, environmental air pollution probably contributes only a very small fraction to the effect of cigarette smoking on this type of cancer.