Assessment of occupational exposure to crystalline silica during demolition of buildings in Tehran

The term "crystalline silica", refers to crystallized form of SiO2 and quartz,
as the most abundant compound in earth crust. I It can cause silicosis and lung cancer following
inhalation of large doses in course of occupational exposure. Silica exposure is unavoidable during
demolition of buildings and therefore it can lead to many problems for demolition workers’ health.
The aim of this study was the assessment of workers respiratory exposure with crystalline silica
during demolition of buildings in Tehran.
Methods: In this study, in order to assess the airborne crystalline silica exposure, four zones of
Tehran (west،east،south،center) were selected. Samples were collected on mixed cellulose filters, by
using filter holder at flow rate of 2 l/min for a maximum volume of 800 liters. After transferring the
samples to the laboratory, analysis of samples were performed using Visible absorption spectrometry
(at 420-820nm) according to theNIOSH method No. 7601.
Results: The higher average of exposure to crystalline silica with geometric mean of 0.185 mg/m3
was related to south area, and center area with GM 0.085 mg/m3 had the lowest exposure with
crystalline silica .The number of 48 samples (80%) of total samples were above the standard for
crystalline silica (ACGIH; 0.05mg/m3). The geometric mean of workers' exposure to crystalline
silica was in the range of 0/085-0/0185 mg/m3.
Conclusion: Based on the obtained results showing that the 80% of total samples were above the
recommended threshold limit value (0.05mg/m3) and considering the high potential of exposure to
crystalline silica during demolition of buildings,, control of dust emission during demolition projects
is required.