Greenhouse Particulates References

The following references on greenhouse particulates were kindly supplied by Kathy Merrifield, Department of Botany and Plant Pathology, Oregon State University, Corvallis, OR 97331-2902. Thanks to Kathy for these which may be helpful to greenhouse operators dealing with soil materials, greenhouse workers, and the public.

Cormier, Y., L. P. Boulet, F. Berube-Genest. 1990. Effects of chronic organic dust exposure on respiratory function and airway responsiveness in peat moss factory workers. Arch. Environ. Health 45(1): 20-3.

Fifty-two males and 1 female, who were 19 to 62 y of age (median = 26), were employed at an eastern Quebec peat moss plant and were included in this study. Of these 53 workers, 29 were smokers, 5 were ex-smokers, and 19 had never smoked. The workers were divided by level of exposure into 4 groups: (1) group l--minimal exposure (N = 7); (2) group 2--light exposure (N = 7); (3) group 3--moderate exposure (N = 17); and (4) group 4--heavy exposure (N = 22). Chest radiographs and physical examinations were normal for all subjects. Only 1 subject had precipitins to Penicillium and Monocillium species isolated from the peat moss plant. Pulmonary function tests were normal and similar in all groups. Thirty-three subjects (20 smokers, 4 ex-smokers, and 9 nonsmokers) had chronic bronchitis; these symptoms were related to work exposure for 28 subjects. Bronchial responsiveness to methacholine was measured in 14 subjects who had persistent cough and sputum. No subject had evidence of airway hyper-responsiveness, i.e., PC20 metacholine less than 8 mg/ml. We concluded that the peat moss workers in our study showed no evidence of extrinsic allergic alveolitis; however, chronic exposure to organic dust leads to chronic cough and sputum production, which is not associated with significant lung impairment nor increase in nonspecific airway responsiveness.

Elmes, P. C. 1987. Perlite and other 'nuisance' dusts [editorial]. J. Roy. Soc. Med. 80(7): 403-4.

Cooper, W. C. and E. N. Sargent. 1986. Study of chest radiographs and pulmonary ventilatory function in perlite workers. J. Occup. Med. 28(3):99-206.

A review of chest films from 152 workers who had been employed five or more years in perlite mining or processing showed none with small opacities of profusion 1/0 or higher. There were 14 films with doubtful changes (0/1), but these showed no correlation with type or duration of employment. Pulmonary function was measured in 122 current employees from the same plants. Multiple regression analysis showed no significant association between years of employment in perlite and either forced vital capacity (FVC) or forced expiratory volume (FEVl). There was a significant association between pack-years of cigarettes and both measurements. In 66 workers tested in 1975 and again in 1983, there was an average annual decrease in FVC of 32 mL, with 26 mL predicted by the Knudson formula, which is based on nonsmokers. The average annual decrease in FEVl was 24 mL with 26 mL predicted. Comparison of groups with differing smoking patterns showed that the decreases in both FVC and FEVl were associated with smoking. The 28 men who had added four or more pack-years in the interval between tests showed decreases in FVC and FEVl of 44 mL/year and 31 mL/year, respectively, with 26 mL/year predicted for both groups. Those with less than four added pack-years (which included 26 nonsmokers) had decreases in FVC and FEVl of 23 mL/year and 19 mL/year with 26 mL/year and 27 mL/year predicted.

Cooper, W. C. 1975. Radiographic survey of perlite workers. J. Occup. Med. l7(5):304-7.

Chest roentgenograms of 240 perlite workers employed for 1 to 23 years in the industry, showed no evidence of pneumoconiosis associated with perlite exposures. One individual, found to have simple pneumoconiosis, and one found to have complicated pneumoconiosis, had formerly been diatomaceous earth workers. Since only 28 of the men had been in the industry over 15 years and only seven for 20 years or more, continued surveillance is essential to make sure that there are no effects with more prolonged exposures. Studies of pulmonary function of the individuals who have had relatively long exposures are needed to supplement radiographic evidence.

Cooper, W. C. 1976. Pulmonary function in perlite workers. J. Occup. Med. l8(11):723-9.

Pulmonary function was studied in 117 men employed in three plants engaged in the mining and processing of perlite. Of these, 38 had been employed for ten years or more; 18 for 15 years or more and four men for 20 years or more. Review of chest films confirmed previous studies which showed no changes indicative of pneumoconiosis. Measurement of forced vital capacity (FVC) by Jones Pulmonor and by Collins 9-1iter spirometer did not show reductions correlated with length of exposure, after effects of cigarette smoking had been taken into account. There was instead a slight increase in FVC associated with years in the perlite industry. The distribution of individuals with FVC below 80% of predicted also showed no association with duration of perlite exposure. Although there were slight reductions in forced expiratory volume in one second (FEVl) and in FEVl/FVC% which were associated with years in the perlite industry and which could not be explained by cigarette smoking, these reductions were not statistically significant. In summary, the population of men available for study in the major perlite-producing area of the United States, who have worked for periods up to 23 years, showed no evidence of pneumoconiosis by chest radiography or by measurement of forced vital capacity. Nevertheless, continued control of dust to ensure exposures below nuisance dust levels is essential. Medical surveillance should also continue with records being retained for periodic reevaluation.

Addison, J. 1995. Vermiculite: a review of the mineralogy and health effects of vermiculite exploitation. Regul. Toxicol. Pharmacol. 21(3):397-405.

Vermiculite is a mica-type mineral that is being used in increasing quantities for insulation, in composite cements, and in horticulture. No serious health risks have been found resulting from the exposure to vermiculite alone nor are any anticipated in view of its long-term chemical durability, even with respect to fibers of vermiculite. Vermiculite ores may contain a variety of other minerals including asbestos, which, if present in significant quantities, could pose a health risk to producers and end users. A variety of regulations are in place that should prevent inadvertent exposure to asbestos in vermiculites, but great care is needed if true asbestos hazards are to be correctly identified. At the same time, vermiculites containing any of a variety amphibole minerals should not be excluded from use because of mistaken identification of these minerals as asbestos. A variety of test methods that have been developed are described and recommendations are made with respect to appropriate action levels for asbestos in vermiculites or other raw materials.

Srebro, S. H. and V. L. Roggli. 1994. Asbestos-related disease associated with exposure to asbestiform tremolite. Amer. J. Ind. Med. 26(6):809-19.

Tremolite is nearly ubiquitous and represents the most common amphibole fiber in the lungs of urbanites. Tremolite asbestos is not mined or used commercially but is a frequent contaminant of chrysotile asbestos, vermiculite, and talc. Therefore, individuals exposed to these materials or to end-products containing these materials may be exposed to tremolite. We have had the opportunity to do asbestos body counts and mineral fiber analysis on pulmonary tissue from five mesothelioma cases and two asbestosis cases with pulmonary tremolite burdens greater than background levels. There were no uncoated amosite or crocidolite fibers detected in any of these cases. Three patients were occupationally exposed to chrysotile asbestos; two patients had environmental exposures (one to vermiculite and one to chrysotile and talc) and one was a household contact of a shipyard worker. The tremolite burdens for the asbestosis cases were one to two orders of magnitude greater than those for the mesothelioma cases. Our study confirms the relationship between tremolite exposure and the development of asbestos-associated diseases. Furthermore, the finding of relatively modest elevations of tremolite content in some of our mesothelioma cases suggests that, at least for some susceptible individuals, moderate exposures to tremolite-contaminated dust can produce malignant pleural mesothelioma.

Heederik, D., J. de Cock, and E. Endlich. 1994. Dust exposure indices and lung function changes in longshoremen and dock workers. Amer. J. Ind. Med. 26(4):497-509.

A group of Dutch harbor workers involved in loading and unloading bulk products from sea vessels such as coal, cokes, and some other products like alumina, borax, phosphate ore, and vermiculite was studied. Exposures were characterized by personal and environmental monitoring. This information was subsequently used to estimate several dust exposure indices and to study relationships with lung function variables and respiratory symptoms. Average respirable dust exposure levels ranged from 0.3-4.0 mg/m3. Workers involved in unloading products from sea vessels were exposed to the highest dust levels. Supervisors and workers with tasks in the dock had an intermediate to low exposure. Office workers had the lowest exposure to respirable dust. Inhalable dust levels were considerably higher and average exposures ranged from 0.3-80 mg/m3. The ranking of occupational titles by inhalable dust exposure was almost identical to the rank order of respirable dust levels. Workers with higher current and cumulative dust exposures tended to have a lower lung function, and only shortness of breath had a statistically significant relationship with current and cumulative inhalable dust exposure. In general, relationships between lung function and inhalable dust levels tended to be somewhat stronger in terms of statistical significance, because inhalable dust is an estimate of dust deposition in the upper airways and lung function is a measurable parameter of airway obstruction in that region. However, the differences with respirable dust were minimal, and variability in dust exposure levels was extremely large for this population. It was concluded that harbor workers involved in unloading ships containing coal and various kinds of ore can be exposed to high dust levels. Relationships between dust exposure and lung function illustrate that these exposures are a respiratory hazard. Our finding that inhalable dust levels have a somewhat stronger relationship with lung function level than respirable dust levels deserves further attention.

Vacek, P. M. and J. C. McDonald. 1991. Risk assessment using exposure intensity: an application to vermiculite mining. Brit. J. Ind. Med. 48(8):543-7.

Estimation of exposure-response relations from epidemiological data is complicated by the fact that exposures usually vary in intensity over time. Cumulative exposure indices, which do not separate the effects of intensity and duration, are commonly used to circumvent this problem. In this paper the estimation of relative risk for specific ranges of exposure intensity from such data is considered using existing statistical methods for fitting multivariate relative risk models. This has the advantage that it does not assume that exposure intensity and duration have equivalent effects on risk. It also throws light on the possible existence of a threshold. The procedure was applied to data from a cohort of 406 vermiculite miners to examine the lung cancer risk associated with exposure to fibrous tremolite, which contaminated the vermiculite. The pattern of exposure-response differed substantially from that obtained using a cumulative exposure index to assess risk.

Merchant, J. A. 1990. Human epidemiology: a review of fiber type and characteristics in the development of malignant and nonmalignant disease. Environ. Health Perspec. 88:287-93.

Consideration of the human epidemiology of diseases arising from exposure to naturally occurring and man-made mineral fibers encompasses the several forms of asbestos (chrysotile, crocidolite, amosite, anthophyllite, tremolite-actinolite), other naturally occurring silicates (talc, sepiolite, erionite, attapulgite, vermiculite, and wollastonite), and man-made mineral fibers (glass continuous filament, glass/rock/slag insulation wools, ceramic and other refractory fibers, and glass microfibers). The diseases arising from exposures to some of these fibers include pleural thickening (plaques, diffuse pleural thickening, and calcification), pulmonary fibrosis, lung cancers, mesothelioma of the pleura and peritoneum, and other cancers. Risk factors important in assessing these diseases include assessment of latency, duration of exposure, cumulative exposure, fiber origin and characteristics (length and diameter), other possible confounding occupational or environmental exposures, and smoking. Methodological issues commonly presenting problems in evaluation of these data include assessment of the adequacy of environmental exposures, particularly in regard to fiber identification, distribution, and concentration over the duration of exposure, and the adequacy of study design to detect health effects (disease frequency, latency, and cohort size). Research priorities include further assessment and standardization of pleural thickening relative to fiber exposure, uniform mesothelioma surveillance, further epidemiological assessment of certain silicate and man-made mineral fiber cohorts with emphasis given to assessment of tremolite and small diameter glass and ceramic fibers. Further assessment of possible health risks of the general public should await improved definition of relevant fiber exposure in ambient air.

McDonald, J. C., A. D. McDonald, P. Sebastien, and K. Moy. 1988. Health of vermiculite miners exposed to trace amounts of fibrous tremolite. Brit. J. Ind. Med. 45(9):630-4.

A small cohort of 194 men with low exposure to fibrous tremolite (mean 0.75 f/ml y) in the mining and milling of vermiculite in South Carolina experienced 51 deaths 15 years or more from first employment. The SMR (all causes) was 1.17 reflecting excess deaths from circulatory disease. There were four deaths from lung cancer and 3.31 expected (SMR 1.21, 95% CI 0.33-3.09). Three of the four deaths were in the lowest exposure category (less than 1 f/ml y); no death was attributed to mesothelioma or pneumoconiosis. These findings contrast with those in Montana where the vermiculite ore was heavily contaminated with fibrous tremolite. A radiographic survey of 86 current and recent South Carolina employees found four with small parenchymal opacities (greater than or equal to 1/0) and seven with pleural thickening. These proportions were not higher than in a non-exposed group and much lower than had been observed in Montana. Examination of sputum from 76 current employees showed that only two specimens contained typical ferruginous bodies, confirming low cumulative fiber exposure. Any possible adverse effects of work with vermiculite, minimally contaminated with fibrous or non-fibrous tremolite, were thus beyond the limits of detection in this workforce.

Amandus, H. E., R. Althouse, W. K. Morgan, E. N. Sargent, and R. Jones. 1987. The morbidity and mortality of vermiculite miners and millers exposed to tremolite-actinolite: Part III. Radiographic findings. Amer. J. Ind. Med. 11(1):27-37.

A study was conducted to estimate the exposure-response relationship for tremolite-actinolite fiber exposure and radiographic findings among 184 men employed at a Montana vermiculite mine and mill. Workers were included if they had been employed during 1975-1982 and had achieved at least 5 years tenure at the Montana site. Past fiber exposure was associated with an increased prevalence of parenchymal and pleural radiographic abnormalities. Smoking was not significantly related to the prevalence of small opacities. However, the number of workers who had never smoked was small, and this prevented measurement of the smoking effect. Under control for smoking and age, the prevalence of small opacities was significantly greater for vermiculite workers with greater than 100 fiber/cc-years exposure than for comparison groups (cement workers, blue collar workers, and coal miners) who had no known occupational fiber exposure. A logistic model predicted an increase of 1.3% in the odds ratio for small opacities at an additional exposure of 5 fiber-years.

Amandus, H. E. and R. Wheeler. 1987. The morbidity and mortality of vermiculite miners and millers exposed to tremolite-actinolite: Part II. Mortality. Amer. J. Ind. Med. 11(1):15-26.

The vermiculite ore and concentrate of a mine and mill located near Libby, Montana was found to be contaminated with a fiber of the tremolite/acetinolite series. A study was conducted to estimate the exposure-response relationship for mortality for 575 men who had been hired prior to 1970 and employed at least 1 year at the Montana site. Individual cumulative fiber exposure (fiber-years) was calculated. Results indicated that mortality from nonmalignant respiratory disease (NMRD) and lung cancer was significantly increased compared to the U.S. white male population. For those workers more than 20 years since hire, the standard mortality rate (SMR) for lung cancer (ICDA 162-163) was 84.7, 225.1, 109.3, and 671.3 for less than 50, 50-99, 100-399, and more than 399 fiber-years respectively. Corresponding results for NMRD (ICDA 460-519) were 327.8, 283.5, 0, and 278.4. Based on a linear model for greater than 20 years since hire, the estimated percentage increase in lung cancer mortality risk was 0.6% for each fiber-year of exposure. At 5 fiber-years, the estimated percentage was 2.9% from an unrestricted (nonthreshold) linear model and 0.6% from a survival model.

Amandus, H. E., R. Wheeler, J. Jankovic, and J. Tucker. 1987. The morbidity and mortality of vermiculite miners and millers exposed to tremolite-actinolite: Part I. Exposure estimates. Amer. J. Ind. Med. 11(1):1-14.

The vermiculite ore and concentrate of a mine and mill near Libby, Montana, was found to be contaminated with fibrous tremolite-actinolite. Of 599 fibers (length greater than 5 microns and width greater than 0.45 micron) counted in eight airborne membrane filter samples, 96% had an aspect ratio greater than 10 and 16% had an aspect ratio greater than 50. Additionally, 73% of the fibers were longer than 10 microns, 36% were longer than 20 microns, and l0% were longer than 40 microns. Estimates of exposure before 1964 in the dry mill were 168 fibers/cc for working areas, 182 fibers/cc for sweepers, 88 fibers/cc for skipping, and 13 fibers/cc for the quality control laboratory. In 1964-1971, exposure estimates for these areas were 33, 36, 17, and 3 fibers/cc, respectively. Estimates of exposures in the mine before 1971 ranged from 9-23 fibers/cc for drillers and were less than 2 fibers/cc for nondrilling jobs. All 8-hr TWA job exposure estimates decreased from 1972-1976, and from 1977-1982 were less than 1 fiber/cc.

Moatamed, F., J. E. Lockey, and W. T. Parry. 1986. Fiber contamination of vermiculites: a potential occupational and environmental health hazard. Environ. Res. 41(1) :207-18.

Vermiculite ores from Montana, Virginia, and South Africa have been analyzed for the presence of amphibole contamination. Fibrous actinolite was found in unexpanded Montana vermiculite ore at a maximum concentration of 2.0%. The fibers persisted in the expanded ore at a maximum concentration of 0.6%. Actinolite was also found in the Virginia vermiculite ore but at a lower concentration and mostly as cleavage fragments with low length-to-width ratios. South African ore contained rare anthophyllite fibers also with low length-to-width ratios. Vermiculite ores have the potential for amphibole contamination and can represent potential health hazards without proper occupational and environmental control measures.

McDonald, J. C., P. Sebastien, and B. Armstrong. 1986. Radiological survey of past and present vermiculite miners exposed to tremolite. Brit. J. Ind. Med. 43(7):445-9

Chest radiographs taken by a standard technique were obtained from 173 current employees (164 men, 9 women) of a vermiculite mine in Montana, from 80 of 110 past employees resident within 200 miles, and from 47 men from the same area without known exposure to dust. In 43 of the 80 and 24 of the 47 an earlier chest x ray film was retrieved from the hospital archives. All 367 films were assessed blind and independently by three experienced readers using the ILO 1980 classification. Median radiographic assessment scores were analysed in relation to estimated cumulative exposure to the amphibole fibers that contaminate the vermiculite. Logistic regression analyses showed independent effects of age, smoking, and exposure on the prevalence of small opacities and of age and probably of exposure on pleural thickening. Overall, the data suggest that by retirement age the increase in prevalence of small opacities (greater than or equal to 1/0) lies between 5% and 10% per 100 f/ml years. This gradient may be somewhat steeper than for chrysotile miners and millers, but not much so.

McDonald, J. C., A. D. McDonald, B. Armstrong, and P. Sebastien. 1986. Cohort study of mortality of vermiculite miners exposed to tremolite. Brit. J. Ind. Med. 43(7):436-44.

A cohort of 406 men employed before 1963 for at least one year in a vermiculite mine in Montana was followed up until July 1983. The vermiculite ore as fed to the mill contained 4-6% of amphibole fiber in the tremolite series. Vital status was established in all but one of the 406 and death certificates were obtained and coded for 163 of the 165 men who died. Compared with white men in the United States, the cohort experienced excess mortality from all causes (SMR 1.17), respiratory cancer (SMR 2.45), non-malignant respiratory disease (SMR 2.55) 1 and accidents (SMR 2.14) . Four deaths were from malignant mesothelioma (proportional mortality 2.4%) . Compared with Montana death rates, the SMR for respiratory cancer was somewhat higher (3.03) . Man-year analyses of respiratory cancer and estimated cumulative exposure gave a relation that did not depart significantly from linearity. The results of this and case-referent analyses indicate an increased risk of mortality from respiratory cancer in this cohort of about l% for each fiber year of exposure. In relation to estimated exposure the mortality experienced by the cohort from both lung cancer and mesothelial tumors was higher than in chrysotile mining.

Glenn, R., H. Amandus, J. Hankinson, M. Petersen, and M. Pickett-Harner. 1986. ORD--NIOSH prevention strategy and selected research. Amer. Ind. Hyg. Assoc. J. 47(11):674-80.

Hessel, P. A. and G. K. Sluis-Cremer. 1989. Prediction equations for lung function in black industrial workers at Palabora Mining Company. South Afr. Med. J. 76(10):548-9.

In the course of a study on the health effects of vermiculite, 653 black rural industrial workers had their lung function measured. Since the study revealed no health effects of their industrial environment, the group was used to determine prediction equations for black men. Vital capacity, forced vital capacity, forced expiratory volume in 1 second, and peak flow were appreciably higher than the predicted values for blacks in the USA. The predicted values were, however, lower than those reported for white non-smokers but significantly higher than those reported for a non-smoking group of black miners in South West Africa/Namibia.

Amandus, H. E. 1987. Prevalence of radiographic small opacities in vermiculite miners [letter]. Amer. J. Ind. Med. 12(2):227-8.

Lockey, J. E., S. M. Brooks, A. M. Jarabek, P. R. Khoury, R. T. McKay, A. Carson, J. A. Morrison, J. F. Wiot, and H. B. Spitz. 1984. Pulmonary changes after exposure to vermiculite contaminated with fibrous tremolite. Amer. Rev. Respir. Dis. 129(6):952-8.

Workers exposed to vermiculite contaminated with fibrous tremolite were surveyed for the presence of respiratory symptoms by questionnaire, and for pneumoconiosis by chest radiograph. Pulmonary function was measured by spirometry and single-breath carbon monoxide diffusing capacity (DLCOsb). Fiber exposure indexes, expressed as fiber/ml-yr, were derived for each worker from available industrial hygiene data and work histories. The estimated cumulative exposure for the work force ranged from 0.01 to 39 fiber/ml-yr. Discriminant analysis demonstrated significant correlates with shortness of breath and pleuritic chest pain to cumulative fiber exposure. The radiographic changes were limited to pleural changes and involved 4.4% of the population. Parametric and discriminant analysis demonstrated a significant correlation with radiographic changes and cumulative fiber exposure. There were no correlations between spirometry or DLCOsb and fiber exposure. Exposure to vermiculite contaminated with fibrous tremolite can cause pleural changes in occupationally exposed workers. This is supported by the previously identified 12 cases of benign pleural effusions in this working population and the association of pleural radiographic changes and pleuritic chest symptoms with cumulative fiber exposure. The lack of significant parenchymal radiographic, spirometric, and DLCOsb changes most likely reflects the low cumulative fiber exposure.

Lockey, J. E. 1981. Nonasbestos fibrous minerals. Clin. Chest Med. 2(2):203-18.

Levin, L. and P. W. Purdom. 1983. A review of the health effects of energy conserving materials. Amer. J. Public Health 73(6):683-90.

The energy conservation movement has promoted both greater use of insulating materials and the reduction of heat losses by sealing air leaks. The release of volatile or airborne materials from the installation of these building materials under these conditions has resulted in an exacerbated indoor air pollution with the potential for certain health and safety hazards. Consequently, a comparative review of the health and safety hazards, exposure standards, and regulatory action associated with the more commonly used insulating materials with particular respect to current energy conservation measures was undertaken. The materials reviewed included asbestos, urea-formaldehyde foam, polyvinyl chloride, cellulosic insulations, fibrous glass, mineral wool, and vermiculite. Although no longer used, the past installation of asbestos in a friable form is the greatest potential health hazard. The exposure to formaldehyde gas from its release from urea-formaldehyde foam has elicited subjective complaints of sensory irritation and unresolved controversy and regulatory action regarding its toxicity to humans. Lesser health problems have been associated with the more widely used fibrous glass and mineral or rock wools.

Hayward, S. B. and G. R. Smith. 1984. Asbestos contamination of vermiculite [letter]. Amer. J. Public Health 74(5):519-20.

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