Hummm. Not sure what to think.
Health Effects on Perlite Industry Workers
Perlite miners, and people occupied at perlite production plants or in industries that use perlite, are the most likely to be exposed to the material. Those groups of workers are the first that have been investigated for potential health effects related to perlite exposure. The first comprehensive study, performed by Cooper in 1975, is a radiographic survey of 285 workers from 10 facilities (including mining and expansion operations) in western U.S. states, whose tenure ranged from 1 to 23 years[1]. The researcher was able to review chest X-rays from 240 of the workers and found no individuals having definitive evidence of pneumoconiosis in the cohort other than two workers with prior histories of working with diatomaceous earth (DE). Consequently, he concluded that the results support the position that perlite does not produce pneumoconiosis while cautioning that exposures should be kept at or below nuisance dust levels and to maintain medical surveillance. No data were available at the time on the respirable crystalline silica content of the ores. One year later, Cooper published the results of another study of 117 workers from three plants in the San Luis valley of northern New Mexico and southern Colorado, involving one expansion facility and two perlite mining operations, whose occupational tenure ranged from 1 to 23 years (average of 7.9 years)[2]. After clinical examination and a review of the X-ray films, he again did not find any changes indicative of pneumoconiosis. In 1980, Cooper summarized the conclusion of all aforementioned studies in a workshop organized by the U.S. Environmental Protection Agency (EPA) having as topic the substitution of asbestos[3]. Later in 1983, Cooper & Sargent examined chest X-rays from 152 workers who had been employed five or more years in perlite mining and processing. Nearly all of these workers were exposed to dust levels beneath the OEL, but some (those engaged in bagging of expanded perlite) were exposed to dust levels above the OEL. The authors concluded that the chest films of workers with over 5 years of employment gave no indication that any of them was developing pneumoconiosis[4]. The studies of Cooper have been reviewed by Elmes who also confirmed that prolonged perlite exposure produces little if any X-ray change or loss of lung function[5].
In a separate study, Maxim, Niebo and McConnell reviewed and published two unpublished works of H.Weill that were reported by Tulane University[6]. The studies were entitled “Summary Report on Perlite Worker Survey”. These were reported in 1990 and 1994, respectively, and presented the results of pulmonary function, respiratory symptoms and chest X-rays studies of workers exposed to perlite. The 1990 study included workers from plants in New Mexico, Colorado and an expanding facility in Illinois. After examination of pulmonary function of 132 workers, and analysis of the chest X-rays of 147 workers, Weill concluded that there was no evidence of pneumoconiosis, and noted that “the working population is healthy, from a respiratory standpoint, not exhibiting undue respiratory symptoms, and having, on average, normal lung function”. The 1994 study included seven perlite production plants and 89 workers with an average duration of 7 years with some exposed as long as 26 years. Weill concluded that “This survey provides substantial reassurance that the currently employed workforce has, to date, been free of any evidence of a silicosis risk, or, indeed, any measurable adverse respiratory effects of perlite exposure”.
Studies have also been conducted of workers occupationally exposed to perlite in plants in Turkey. One of the difficulties of evaluating studies of perlite workers in Turkey is the high percentage of smokers in the population. Cigarette smoking is associated with several adverse effects in the lungs including chronic inflammation typical of chronic bronchitis, structural damage as seen with emphysema, functional impairment resulting in obstructive lung disease, radiographic abnormalities including irregular opacities, and lung cancer[6]. For example, Polatli et al. studied 36 perlite exposed and 22 unexposed (office) workers at a perlite plant in Menderes near Izmir (activities not stated)[7]. All of the considered people were smokers, while dust levels exceeded the OEL, thus assessment of the likely health effect in a well-controlled workplace is impossible. The authors concluded that a 12 year perlite exposure period did not lead to a decrease in mean pulmonary function tests (PFTs) nor exhibit any correlation between PFTs and duration of work in perlite areas. Thus, once again no negative health effects of perlite exposure were identified despite dust exposure levels exceeding the officially prescribed OELs.
The above studies of workers occupationally exposed to both perlite ore and expanded perlite, including some that were exposed to perlite dust at levels well above the present Occupational Exposure Levels (OEL), provide strong evidence that the health effects of occupational exposure to perlite dust are minimal.