Respiratory Morbidity Associated with Long-Term Occupational Inhalation Exposure to High Concentrations of Hydrated Calcium Sulfate Dust

Despite wide application of hydrated calcium sulfate, possible respiratory effects of long-term occupational exposure to high concentrations of this chemical have only been investigated in a limited number of epidemiological studies. This study is undertaken to examine this issue, more thoroughly. This cross-sectional study is carried out at a local gypsum plant in Shiraz, capital of Fars province situated in south western Iran. All exposed subjects (20 male workers) and 20 healthy non-exposed male individuals as the referent group are investigated. Prevalence of respiratory symptoms among the studied subjects is evaluated and they undergo spirometry test (twice for the exposed group and once for the unexposed employees). Moreover, to assess the extent to which workers are exposed to gypsum dust and using standard methods, inhalable and respirable fractions of this compound are measured in different dusty worksites. Average airborne concentration of inhalable dust fraction is estimated to be 24 ± 14.76 mg/m3 which is higher than the recommended threshold limit value (TLV) for this chemical. Respiratory symptoms such as phlegm, wheezing and dyspnea are significantly more prevalent in exposed subjects than in non-exposed employees (p < 0.05). The results of ventilatory function tests (pre- shift) don’t show any significant differences between both groups. However, some post-shift parameters of ventilatory function such as FVC, FEV1 and FEV1/FVC ratio are significantly lower than those of preshift and referent group. Exposure to high atmospheric concentrations of gypsum dust is associated with a significant increase in the prevalence of respiratory symptoms along with acute reversible significant decreases in some parameters of ventilatory function.