rate of suspended particulate distribution (pm2.5, pm10 and tsp) in hamadan main intercity bus stations and its exposure rate

background: the objective of this study was to measure the total suspended particulate (tsp), pm 10 and pm 2.5 air particulates in the selected intercity bus stations located in the central square of hamadan, to review the distribution concentration of the air particulates content and to evaluate its possible health risk to the people who spent little time of their daily time in those places. methods: this was a descriptive and cross-sectional study. sampling was done systematically in six bus stations at different time intervals. a portable air sampler, sampled air at 10 liters per minute for suspended particulates (tsp and pm 10 ) measured at 1 meter height above the ground. for measuring pm 2.5 after the cyclone, fine particles were collected at a flow rate of 2 liters per minute onto a filter. the suspended particulate was collected on 47 mm mixed cellulose ester (mce) membrane filters, which must be weighed pre and post-exposure to determine the concentrations in micrograms/cubic meter. temperature, humidity and wind speed was measured at the sampling locations, and their averages were recorded. to analyze the data, we used statistical analysis pearson correlation coefficient using spss software to study the correlation between the concentration variation of the particulate distribution and humidity, temperature and wind speed as well. findings: the results obtained for tsp, pm 10 and pm 2.5 during the sampling period were 1220.9 ± 1418.5, 524.7 ± 217.5 and 386 ± 193.6 μg/m 3 , respectively. exposure to these pollutants as time weighted average were 50.872, 21.87 and 16.08 µg /m 3 , respectively that were lower than the standards set by the accredited organizations. there was no significant relationship between the concentration variation of the suspended particulate and wind speed and air temperature (p > 0.05); however, there was a significant relationship between the concentration variation of the suspended particulate and humidity (p < 0.05). pm 2.5 and pm 10 with total suspended particles had correlation coefficient of r 2 = 0.74 and r 2 = 0.78, respectively. conclusion: results of this study illustrated that there were particular concerns regarding potential human health impacts for people who spend considerable time at intercity bus stations or close to them. pedestrians and unofficial business employees are expected to be exposed to high concentrations of suspended particulate pollution because of longer contact time that applied in this study.