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Biomedical subjects

M D Attfield

Publications and source records attributed to M D Attfield.

At least 37 records · Page 2Linked to original sources
PubMed1993

Longitudinal and cross sectional analyses of exposure to coal mine dust and pulmonary function in new miners.

The association between exposure to dust and pulmonary function was studied by longitudinal and cross sectional analyses in a group of United States underground coal miners beginning work in or after 1970. Quantitative estimates of exposure to respirable coal mine dust were derived from air samples taken periodically over the entire study period. The cohort included 977 miners examined both in round 2 (R2) (1972-5) and round 4 (R4) (1985-8) of the National Study of Coal Workers' Pneumoconiosis. Multiple linear regression models were developed for both cross sectional (pulmonary function at R2 and R4) and longitudinal (change in pulmonary function between R2 and R4) analyses with exposure partitioned into pre-R2 and post-R2 periods and controlled for covariates including smoking history. The results indicate a rapid initial (at R2) loss of FVC and FEV1 in association with cumulative exposure of the order of 30 ml per mg/m3-years. Between R2 and R4 (about 13 years) no additional loss of function related to dust exposure was detected although the percentage of predicted FVC and FEV1 did decline over the period. After some 15 years since first exposure (at R4), a statistically significant association of cumulative exposure with FEV1 of about -5.9 ml per mg/m3-years was found. These results indicate a significant non-linear effect of exposure to dust on pulmonary function at dust concentrations present after regulations took effect. The initial responses in both the FVC and FEV1 are consistent with inflammation of the small airways in response to exposure to dust.

Adult↗
PubMed1992

Exposure-response relationships for coal mine dust and obstructive lung disease following enactment of the Federal Coal Mine Health and Safety Act of 1969.

Underground U.S. coal miners were studied cross-sectionally for the association of respirable coal mine dust exposure with pulmonary function and symptoms of airways obstruction. The study group included 1,185 miners participating in Round 4 of the National Study of Coal Workers' Pneumoconiosis who had started mining in or after 1970 when comprehensive exposure regulations first came into effect. Quantitative estimates of cumulative exposure, derived using respirable dust measurements taken by the Mine Safety and Health Administration over the entire study period, were used in linear and logistic regression models on indicators of pulmonary function and chest symptoms while controlling for smoking status, pack-years, and other potential confounders. Statistically significant associations between log cumulative exposure and decrements in FVC, FEV1, and FEV1/FVC were observed. In logistic models, statistically significant associations of cumulative exposure with increasing prevalence of FEV1 and FEV1/FVC less than 80% predicted and symptoms including chronic phlegm, chronic bronchitis, breathlessness, wheeze, and wheeze with shortness of breath were found. It is concluded that exposures to respirable coal mine dust present in U.S. mines since 1970 continue to affect respiratory health in underground miners.

Adult↗
PubMed1992

Some observations on the variation in height coefficients in prediction equations for forced vital capacity.

Intercept and height coefficients in prediction equations for forced vital capacity (FVC) are highly correlated and highly variable, due in part to the small coefficient of variation of height (4%). This degree of imprecision and relationship was observed among the coefficients of a set of 26 unrelated published prediction equations, and appeared to dominate any systematic differences between them in methodology and technique. The findings indicate that care needs to be taken when using equations for predicting the FVC of people at the extremes of height. They also demonstrate the need for careful planning in the design of studies intended for the compilation of prediction equations, including provision for sufficient numbers of observations. Support is also given to the use of a composite formula based on the averaging of many individual prediction equations. The results are applicable to other similar and commonly used lung function equations (e.g. that for forced expiratory volume in 1 second, FEV1) that employ height as a predictor variable.

Adult↗
PubMed1992

The derivation of estimated dust exposures for U.S. coal miners working before 1970.

A number of reports on the prevalence of coal workers' pneumoconiosis in U.S. coal miners have been published, yet very little is known about the relationship between dust exposure and pneumoconiosis levels in the U.S. This report describes the derivation of cumulative dust exposure estimates by back-extrapolation of data processed by the Mine Safety and Health Administration after 1970 by using a ratio of dust concentrations based on information collected during environmental surveys at certain U.S. mines by the Bureau of Mines between 1968 and 1969. Cumulative personal dust exposure estimates were calculated by using occupational histories obtained from the miners and job-specific estimates of dust concentration. In other reports, the resulting estimated exposures have been shown to correlate well with various measures of respiratory morbidity.

Adult↗
PubMed1992

Exact expressions for the bias and variance of estimators of the mean of a lognormal distribution.

Exact mathematical expressions are given for the bias and variance of the arithmetic and maximum likelihood estimators of the first moment (mean) of a lognormal distribution. On the basis of these exact expressions, and without the need for simulation, statistics on the bias and variance have been computed for a range of sample sizes and geometric standard deviations. The results reaffirm that an unbiased maximum likelihood estimator exists that has minimum variance. Contrary to some recent recommendations, this is the preferred estimator if the data truly come from a lognormal distribution.

Analysis of Variance↗
PubMed1992

An investigation into the relationship between coal workers' pneumoconiosis and dust exposure in U.S. coal miners.

The National Study of Coal Workers' Pneumoconiosis (NSCWP) is a large, continuing epidemiologic study of the respiratory health of U.S. coal miners. By using information from the study, prevalence of coal workers' pneumoconiosis (CWP) was related to indexes of dust exposure obtained from research and compliance sampling data. Clear relationships between prevalences of both simple CWP and progressive massive fibrosis (PMF) and estimated dust exposure were seen. Additional effects independently associated with coal rank (% carbon) and age were also seen. Logistic model fitting indicated that between 2% and 12% of miners exposed to a 2-mg/m3 dust environment in bituminous coal mines would be expected to have Category 2 or greater CWP after a 40-yr working life; PMF would be expected for between 1.3% and 6.7%. The risks for anthracite miners appeared to be greater. There was a suggestion of a background level of abnormality, not associated with dust exposure, but increasing with age. Although there are certain weaknesses in the data used to derive these exposure estimates, the results are in general agreement with, but somewhat greater than, some recent findings for British coal miners.

Adult↗
PubMed1992

Pulmonary function of U.S. coal miners related to dust exposure estimates.

This study of 7,139 U.S. coal miners used linear regression analysis to relate estimates of cumulative dust exposure to several pulmonary function variables measured during medical examinations undertaken between 1969 and 1971. The exposure data included newly derived cumulative dust exposure estimates for the period up to time of examination based on large data bases of underground airborne dust sampling measurements. Negative associations were found between measures of cumulative exposure and FEV1, FVC, and the FEV1/FVC ratio (p less than 0.001). In general, the relationships were similar to those reported for British coal miners. Overall, the results demonstrate an adverse effect of coal mine dust exposure on pulmonary function that occurs even in the absence of radiographically detected pneumoconiosis.

Adult↗
PubMed1992

Epidemiological data on US coal miners' pneumoconiosis, 1960 to 1988.

OBJECTIVES: Statistics on prevalence of pneumoconiosis among working underground coal miners based on epidemiologic data collected between 1960 and 1988 are presented. The main intent was to examine the time-related trend in prevalence, particularly after 1969, when substantially lower dust levels were mandated by federal act. METHODS: Data from studies undertaken between 1960 and 1968 were collected and compared. Information for the period 1969 to 1988 was extracted from a large ongoing national epidemiologic study. Tenure-specific prevalence rates and summary statistics derived from the latter data for four consecutive time intervals within the 19-year period were calculated and compared. RESULTS: The results indicate a reduction in pneumoconiosis over time. The trend is similar to that seen in a large radiologic surveillance program of underground miners operated concurrently. CONCLUSIONS: Although such factors as x-ray reader variation, changes in x-ray standards, and worker self-selection for examination may have influenced the findings to some extent, adjusted summary rates reveal a reduction in prevalence concurrent with reductions in coal mine dust levels mandated by federal act in 1969.

Adult↗
PubMed1992

Surveillance data on US coal miners' pneumoconiosis, 1970 to 1986.

OBJECTIVES: Statistics on prevalence of pneumoconiosis among working underground coal miners from data collected as part of a large national radiographic surveillance program between 1970 and 1986 are presented. The main intent was to examine the time-related trend in prevalence over this period, which coincides with historically low dust levels mandated by federal act. METHODS: Tenure-specific prevalence rates and summary statistics derived from them for four consecutive time intervals within the 16-year period were calculated and compared. RESULTS: The results indicate a reduction in pneumoconiosis over the life of the program. This trend is similar to that seen in epidemiologic studies undertaken concurrently. CONCLUSIONS: Although low participation in the surveillance program and other problems complicate the findings, it appears that reductions in dust exposure mandated by federal act in 1969 have led to lower prevalence of pneumoconiosis among underground coal miners.

Bias↗
PubMed1992

British data on coal miners' pneumoconiosis and relevance to US conditions.

OBJECTIVES: The current primary federal dust standard for US underground coal miners of 2 mg/m3 respirable dust is based on British epidemiological information on exposure-response derived in 1969. Since then, much new information has become available. This paper reviews and compares the available information as it relates to the US mining situation. METHODS: Recent exposure-response information on pneumoconiosis and dust exposure derived by British researchers was employed to estimate working-life risks of pneumoconiosis for miners exposed to 2 mg/m3. RESULTS: It is estimated that close to 9% of underground coal miners who work for 40 years in a 2 mg/m3 environment would develop pneumoconiosis (category 1 or greater). Progressive massive fibrosis would develop in 0.7%. CONCLUSIONS: There are unresolved questions relating to the validity of extrapolating findings on British mines and miners to the US and also in predicting disease levels at the low end of the dust exposure spectrum. Given the data available, current information suggests miners who are employed for a working life-time at the current federal dust limit of 2 mg/m3 are still at risk of developing pneumoconiosis.

Bias↗
PubMed1992

The NIOSH B reader certification program. An update report.

Physicians trained in the use of the International Labour Office system for classification of radiographs of pneumoconioses who pass a competence test administered by the National Institute for Occupational Safety and Health are designated as B readers. The current certification and recertification examinations for qualification under the NIOSH B reader program are described. Details of the rationale and format of each examination are given, and information on candidates' scores provided for the years 1987-1990.

Certification↗
PubMed1990

Evidence that the P2x purinoceptor of the smooth muscle of the guinea pig vas deferens is an ATP4- receptor.

In solutions containing Mg2+ and Ca2+, ATP is in equilibrium between the tetrabasic form (ATP4-) and its bidentate coordination complexes, i.e., MgATP2- and CaATP2-. We sought evidence to determine whether contractions of the smooth muscle of the guinea pig vas deferens to ATP are in response to ATP4- or its bidentate complexes. Contractions to ATP were elicited in seven modified Krebs-Henseleit solutions containing varied concentrations of free and total Mg2+ and Ca2+ to alter the concentration of ATP4- at given ATPtotal concentrations. As the concentration of Mg2+ increased the concentration of ATP required to stimulate contraction to an equivalent degree also increased. Regardless of the free or total Mg2+ and Ca2+ concentrations, response magnitude was generally correlated with [ATP4-]. This suggests that ATP4- is the agonist at the P2x purinoceptor of the guinea pig vas deferens. The potency of ATP4- is high; the threshold, occurring at approximately 1 nM ATP4-, is 1000-fold less than that for norepinephrine. The implications of ATP4- as agonist are discussed in relation to adenine nucleotide potency, metabolism and P2 purinoceptor classification.

Adenosine Triphosphate↗
PubMed1987

Spirometry variability criteria--association with respiratory morbidity and mortality in a cohort of coal miners.

To clarify the association between spirometry variability and respiratory morbidity and mortality, the authors analyzed data for miners examined in the first round of the National Coal Study, 1969-1971, and they compared groups of miners who failed with those who met each of two spirometry variability criteria: a 5% criterion recommended by the American Thoracic Society, and a 200 ml criterion used in prior research studies. Compared with miners who met the 5% criterion (the best two forced vital capacities must be within 5% or 100 ml of one another), the group that failed had a lower mean for forced expiratory volume in one second (FEV1), and odds ratios for cough, phlegm, wheeze, shortness of breath, and death of 1.75, 1.67, 1.76, 2.71, and 1.30, respectively. The findings for the 200 ml criterion (the best two FEV1s must be within 200 ml of one another) were somewhat different. The group that failed versus the group that met this criterion had a higher mean for FEV1, and odds ratios for cough, phlegm, wheeze, shortness of breath, and death of 1.13, 1.07, 1.15, 1.43, and 0.94, respectively. Although the findings differ for the two criteria, the findings demonstrate that increased spirometry variability is associated with poorer health.

Adult↗
PubMed1985

Longitudinal decline in FEV1 in United States coalminers.

Changes in ventilatory function measurements of United States miners who had participated in two surveys held nine years apart were analysed in relation to smoking habits, dust exposure, and other factors. The results showed trends similar to those reported among British miners. Loss of FEV1 over time and found to be related to smoking (0.1 litre excess decline in current smokers compared with those who had never smoked over 11 years) and to occupational exposure (0.036-0.084 litres over 11 years, depending on the index used). The results offer confirmation of the relationship between work in coal mines and loss in ventilatory function observed in British miners, and also seen in cross sectional studies.

Adult↗
PubMed1985

Effects of a two-year inhalation exposure of rats to coal dust and/or diesel exhaust on tension responses of isolated airway smooth muscle.

This study was performed to determine whether chronic inhalation exposure of rats to levels of coal dust (CD) and/or diesel exhaust (DE) similar to those experienced by underground miners affects the pharmacologic characteristics of the animal's airway smooth muscle. Animals were exposed for 2 yr to CD alone (2 mg/m3 of respirable particulates), DE alone (2 mg/m3 of respirable particulates), or CD and DE (CD + DE) in combination (1 mg/m3 CD plus 1 mg/m3 DE). Concentration-response relationships for tension changes induced with acetylcholine, 5-hydroxytryptamine, potassium chloride, and isoproterenol were assessed in vitro on isolated preparations of rat airway smooth muscle (trachealis). Compared with control animals, the maximal contractile responses to acetylcholine of tissues from CD-, DE-, and CD + DE-exposed animals were significantly increased; the effects of CD and DE exposure were additive. The CD + DE exposure, but not the individual treatments, resulted in a significant increase in the maximal relaxation response elicited by isoproterenol; this interaction may have resulted from the addition of, or the synergism between, the nonsignificant effects of CD and DE alone. No treatment altered the sensitivity (EC50 values) of the muscles to the agonists used. The results indicate that chronic exposure to CD, DE, and CD + DE produces differential modifications in the behavior of rat airway smooth muscle. These findings may have some bearing on humans exposed to these substances.

Administration, Intranasal↗
PubMed1983

Sampling for airborne fungi: a statistical comparison of media.

Four broad spectrum media employed for enumeration of fungi from air were compared to determine which would yield the highest number of colony forming units when simultaneously sampling air from the same environment. The four media tested were: Inhibitory Mold Agar, Littman Oxgall Agar, Rose Bengal-Streptomycin Agar, and Sabouraud Dextrose Agar. The number of colony forming units produced on the media were compared by an incomplete four-factor factorial design (day, time, sampler and medium). Analysis of variance of the data indicated that highly significant variation was associated with collection medium and different sampling days. Comparisons among the media were performed by Duncan's multiple range test which demonstrated significantly lower values on Littman Oxgall as compared to the other media. There was no significant difference in the number of colonies produced on Rose Bengal-Streptomycin Agar, Inhibitory Mold Agar, and Sabouraud Dextrose Agar. For a number of reasons, Rose Bengal-Streptomycin Agar is our medium of choice for broad spectrum aeromycological sampling.

Air Microbiology↗