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Biomedical subjects

R G Ames

Publications and source records attributed to R G Ames.

At least 37 records · Page 2Linked to original sources
PubMed1984

Mobility of diesel versus non-diesel coal miners: some evidence on the healthy worker effect.

Workers who are particularly susceptible to the effects of their occupational exposure, from the perspective of the healthy worker effect, soon leave the workplace. The result of this mobility, called survival bias, is that cross sectional studies based on the survivors underestimate the true risk of occupational exposures. Two questions are addressed in this empirical study of the "survival bias" component of the "healthy worker" effect. Do miners with respiratory impairment or symptoms disproportionately leave jobs that have a potentially harmful respiratory exposure? And does the presence of an additional potentially harmful respiratory exposure, in this case diesel emissions, accelerate the rate of mobility for miners with respiratory impairment or symptoms? No confirmation was found for the survival effect in a study of 738 diesel and 420 non-diesel US underground coal miners. No additional increment in mobility was associated with exposure to both coal mine dust and diesel emissions.

Adolescent↗
PubMed1984

Respiratory impairment and symptoms as predictors of early retirement with disability in US underground coal miners.

A five-year prospective study of 1,394 United States underground coal miners was undertaken to study the effects of respiratory impairment on the rate of early retirement with disability (ERD). Using a logistic regression analysis, ERD was found to be related to reported persistent phlegm after adjustment was made for other respiratory symptoms, respiratory function measurements, cigarette smoking, and some demographic characteristics. No prediction of ERD occurred for spirometrically determined measures of respiratory function. The data thus give limited support to the hypothesis that early retirement with disability in underground coal miners can be predicted prospectively by measures of respiratory symptoms.

Coal Mining↗
PubMed1983

Gastric cancer and coal mine dust exposure. A case-control study.

Based on evidence that coal miners have elevated gastric cancer mortality rates, a case-control study was developed to assess the gastric cancer risk of coal mine dust exposure. Forty-six cases of US white male gastric cancer deaths from NIOSH coal miner cohorts were individually matched by age to controls. From these data we show that a statistically elevated gastric cancer risk exists for miners who have prolonged exposure to coal mine dust and prolonged exposure to cigarette smoke. Coal workers' pneumoconiosis, a disease defined in terms of coal dust deposition in the lungs, was not found to be a gastric cancer risk.

Coal Mining↗
PubMed1983

Role of nitrosation in the mutagenic activity of coal dust: a postulation for gastric carcinogenesis in coal miners.

The mutagenicity of coal dust solvent extracts with and without nitrosation was studied using the Salmonella/microsome assay system. Coal dust solvent extracts were either non-mutagenic or very weakly mutagenic with S9 activation. High mutagenic activities, however, were found when extracts of bituminous, subbituminous, and lignite coal dusts were reacted with nitrite under an acidic condition. Formation of mutagens from coal dust extracts by nitrosation was highest at pH 3.2 and decreased with increasing pH in the reaction mixture. Mutagenic activity appeared to be independent of metabolic activation. The mutagens formed from nitrosation of coal dust extracts induced frameshift mutations. The results reported here may have possible implications for the explanation of an elevated incidence of gastric cancer in coal miners.

Coal↗
PubMed1983

Gastric cancer in coal miners: an hypothesis of coal mine dust causation.

An hypothesis is proposed to explain the elevated incidence of gastric cancer among coal miners. Inhaled coal mine dust, especially the larger particles, is cleared from the lung and tracheobronchial tree by mucociliary function, swallowed, and introduced into the stomach. Organic and/or inorganic materials in the dust can undergo intra-gastric nitrosation and/or interaction with exogenous chemicals to form carcinogenic compounds which in turn may lead to precancerous lesions, which may subsequently develop into gastric cancer. This sequence of events, however, depends upon occupational exposures as well as life-style features and individual genetic predisposition.

Coal↗
PubMed1983

The role of the lung in stomach carcinogenesis: a revision of the Meyer hypothesis.

Meyer et al. present an hypothesis postulating an essential opposition between lung cancer and stomach cancer based upon the interaction between cigarette smoking, respiratory impairment, and exposure to airborne carcinogens. Their theory is that respiratory impairment serves as a gate to determine whether carcinogenic airborne particulate is retained in the lungs to produce lung cancer or is cleared and swallowed to produce stomach cancer. This paper examines the foundations of the Meyer hypothesis, identifies particle deposition patterns as a crucial Meyer omission, and presents a reformulated theory based upon both particle deposition and particle retention.

Carcinogens↗
PubMed1983

Lung cancer, stomach cancer, and smoking status among coal miners. A preliminary test of a hypothesis.

This paper presents an empirical test of the hypothesis of Meyer et al, who propose inhaled carcinogens to be a risk for both stomach and lung cancer, stomach cancer occurring in persons with nonimpaired lungs and lung cancer occurring in persons with impaired lungs. Based upon a case-referent study comparing 46 white male coal miners who died from stomach cancer in the United States with age-matched miners who died from lung cancer and with reference miners who died from other cancers or from noncancer, nonaccident causes, the present study failed to confirm the Meyer hypothesis. The data suggest a reverse relationship than that postulated, namely, that airway obstruction may be a precondition for stomach cancer and normal pulmonary function a precondition for lung cancer. Different dust agents were found to be involved with cancers at the different sites. For coal miners with airway obstruction, greater years of coal mine dust exposure were found to pose a slightly elevated stomach cancer risk (odds ratio 3.64, not significant), while, for miners with normal ventilatory function, cigarette smoking posed a disproportionately elevated lung cancer risk (odds ratio 7.00, not significant).

Adult↗
PubMed1982

Acute respiratory effects of exposure to diesel emissions in coal miners.

A study was conducted to determine if acute respiratory effects, measured in terms of changes in forced vital capacity (FVC), forced expiratory volume in one second (FEV1), and maximal expiratory flow rate at 50% of forced vital capacity (Vmax50), were related to exposure to diesel emissions in coal miners. Sixty coal miners exposed to diesel emissions and 90 miners not exposed were tested before and after a work shift for ventilatory function changes. Significant work shift decrements in ventilatory function did occur in miners in both groups who smoked cigarettes, but there were no significant differences in the ventilatory function changes between those miners exposed to diesel emissions and those not exposed either in the aggregate or under control by smoking status.

Adult↗
PubMed1982

The detection of thoracic abnormalities using posterior-anterior (PA) vs PA and oblique roentgenograms.

A reading trial was conducted as part of the 1978 Bay Area Asbestos Screening Project to evaluate the utility of adding oblique-view roentgenograms to standard posterior-anterior (PA) views. Chest films from a sample of 555 workers with histories of long-term asbestos exposure were read twice as PA and twice as PA + oblique sets, providing a basis for assessing reliability through intrareader, interreader, and intermethod agreement. The ancillary use of oblique view films resulted in higher rates of detection of asbestos-related abnormalities than with PA films alone, but the increased rates were gained at the expense of reliability in the interpretation process. Depending on the source of this unreliability, which requires further study, different remedial actions might be indicated. A reader's lack of experience could indicate the need for additional training, the use of several readers, an average over several reader judgements, or the development of standards for evaluating obliques. If, on the other hand, no way is found to reduce the unreliability, the use of oblique films in routine screening programs ought to be discouraged on the basis of measurement theory, since reliability is a prerequisite to validity.

Asbestos↗
PubMedDate not supplied

Does coal mine dust present a risk for lung cancer? A case-control study of U.S. coal miners.

This paper evaluates the relationship between the risk of lung cancer mortality and coal mine dust exposure under control by cigarette smoking status. Two case-control studies based on 317 white male lung cancer mortality cases are presented. A one-to-one matched-case design allows examination of the risk of coal mine dust exposure and cigarette smoking. A two-to-one matched-case design was employed to examine the lung cancer risk of coal mine dust exposure independent of cigarette smoking. Based upon these data, no evidence of a coal mine dust exposure-lung cancer risk was found, although the expected increased risk for lung cancer in cigarette smokers was observed. There was no evidence of an interactive effect between cigarette smoking and coal mine dust exposure.

Coal Mining↗
PubMedDate not supplied

Chronic respiratory effects of exposure to diesel emissions in coal mines.

A 5-yr prospective design was employed to test the hypothesis that exposure to diesel emissions leads to chronic respiratory effects among underground coal miners. Changes in respiratory function and development of chronic respiratory symptoms were measured during a 5-yr study period (i.e., 1977 to 1982) in 280 diesel-exposed and 838 control miners from Eastern and Western United States underground coal mines. Spirometry measures of respiratory function included forced expiratory volume in 1 sec (FEV1.0), forced vital capacity (FVC), and forced expiratory flow rate at 50% of FVC (FEF50). Chronic respiratory symptom measures, which included chronic cough, chronic phlegm, and breathlessness, were obtained by questionnaires, as were smoking status and occupational history. Based upon these data, the pattern of evidence did not support the hypothesis either in an age-adjusted comparison of diesel vs. nondiesel miners or in an internal analysis by cumulative years of diesel exposure.

Adult↗
PubMedDate not supplied

Effect of chlorine dioxide water disinfection on hematologic and serum parameters of renal dialysis patients.

A study of the blood chemistry parameters of 20 renal dialysis patients was undertaken when a local water district introduced chlorine dioxide (CIO2) as a disinfectant at the filtration plant headworks for 12 months without informing the renal dialysis clinic in the area of this potentially adverse change. Due to data limitations, including changes in clinical laboratories and lack of pre-exposure data for some patients, the analysis was focused on 17 patients for whom data was produced by the same clinical laboratory, for 3 months of pre-exposure and 1 month of exposure. Least-squares means of each parameter by CIO2 levels of 0.0 and 1.0 mg/L at the treatment plant were adjusted for age, sex, and creatinine. Water purification at the clinic included passing the water through granular activated carbon, filtration by 5-mu filters, and the use of reverse osmosis. Chlorination products measured at the clinic after this purification and prior to preparation of the dialysate consisted only of chlorite at the 0.02-0.08 mg/L level. No evidence of CIO2-induced anemia was found, nor were any other biologically significant responses observed. Study limitations include several potentially important hematologic parameters which were not measured, the small sample size, and three clinical laboratory changes.

Blood↗
PubMedDate not supplied

Occupational illnesses from cholinesterase-inhibiting pesticides among agricultural applicators in California, 1982-1985.

California pesticide illness investigation reports involving toxicity category I or II organophosphate and carbamate pesticide exposures among agricultural pesticide applicators were reviewed for the years 1982-1985. The pesticides associated with each illness were recorded, and the exposures were classified as chronic, short-term, or accidental. Illnesses were associated with a range of pesticides, including both organophosphates and carbamates in both toxicity categories I and II. Approximately 19% of the illnesses were due to accidents. Overall, the analysis identified a need for improving occupational health surveillance and the regulations governing worker health and safety.

Accidents, Occupational↗
PubMedDate not supplied

Acute health effects of community exposure to cotton defoliants.

In September and October of 1987, the California Department of Health Services responded to community complaints by investigating the relationship between health symptoms and community exposure to cotton defoliants. Symptoms experienced during the 1987 cotton defoliation season by 232 residents of cotton-growing communities were compared with symptoms of 175 residents of non-cotton-growing agricultural communities. Fatigue, eye irritation, rhinitis, throat irritation, nausea, and diarrhea were statistically elevated in rates adjusted for age, sex, and race and were reported 60-100% more frequently by respondents living or working near sprayed cotton fields than by the comparison group. These symptom rate elevations were substantially unchanged even after adjustment by a model of potentially confounding factors that included cigarette smoking, chronic illness, and some additional demographic variables.

Defoliants, Chemical↗
PubMedDate not supplied

Acute health effects from community exposure to N-propyl mercaptan from an ethoprop (Mocap)-treated potato field in Siskiyou County, California.

A 145-acre potato field adjacent to Dorris, California, was treated with ethoprop (Mocap) to control nematodes. Ethoprop releases n-propyl mercaptan, a highly odorous and volatile gas, as a degradation product of the pesticide. An epidemiological investigation was undertaken by the California Department of Health Services because community residents sought medical attention for odor-related illness. Elevated health effects were found among those who reported smelling a strong odor (n-propyl mercaptan has a characteristic onion-like odor). In a logistic regression analysis, the most highly elevated 6-wk health effect incidence risks, expressed as odds ratios (ORs) adjusted for age, sex, and current cigarette smoking status, were for headache (OR = 5.08), diarrhea (OR = 3.80), runny nose (OR = 5.31), sore throat (OR = 3.58), burning/itching eyes (OR = 5.64), fever (OR = 3.59), hay fever attacks (OR = 3.50), and asthma attacks (OR = 6.0). Based upon these elevated health effects, it is recommended that human exposures to n-propyl mercaptan be minimized to the extent practicable.

Adult↗
PubMedDate not supplied

Community exposure to a paraquat drift.

A mixture of paraquat and water was applied, by helicopter, to agricultural fields near a residential community and near an associated commercial complex. Drift from the application passed directly over the community, which resulted in resident complaints to the local county agricultural department. A community survey was undertaken to determine what health consequences, if any, resulted from the drift. A comparison of 2-wk self-reported symptom rates between the exposed community and three historical control communities indicated that 10 symptoms were elevated significantly at p < .05: cough, diarrhea, eye irritation, headache, nausea, rhinitis, throat irritation, trouble breathing, unusual tiredness, and wheezing. An internal comparison, which predicted symptom rates by an index of paraquat exposure (smelling an unusual odor in the prior 2-wk period), indicated fever (relative risk [RR] = 11.97) and nausea (RR = 3.75) to have elevated relative risks. Odor perception also predicted the report of a greater than the average number of symptoms. Based upon these findings, it was concluded that these residents probably did experience an increase in health symptoms from the drift. It is recommended that paraquat not be sprayed near residential communities.

California↗