Metallic Mercury Vapour and Particulates Pollution in a Petrochemical Company

Introduction: Chlorine gas producting by mercury cell (chlor-alkali) is one of the most widely used methods. Leakage and vaporizing mercury from cells can cause occupational poisoning. Mercury is the most toxic non-radioactive heavy metal; therefore measurement of air concentration of this metal is very important. The aim of this research was measuring ambient air mercury concentration in a petrochemical company of Iran.

Materials and Methods: This research was a descriptive-cross sectional study. Air sampling performed using OSHA ID 140 method. Absorbent tubes contain Hydrar (number 226-17-1A) were used to absorb air mercury vapour. Based on this method, a profiler (cellulose ester filter, size 0.8 um) was used to measure mercury particles size and the filter was analysed using OSHA ID 145 method. Air sampling performed in workshop, control room, up and down floor of cells in the plant and the numbers of samples were 8, 8, 12 and 12, respectively. Sampling performed from several sections of each unit throughout working time. Concentration during work shift was stable. Then preparation was analysed in 253.7 nm wavelengths by cold vapour atomic absorption spectrophotometer (UNICAM model 929).

Results: Particulate air mercury concentration in workshop, control room, up and down floor of cells was 2.457±0.235, 9.945±0.930, 27.089±2.344, 18.745±1.016 mg/m³, respectively. Air vapour of mercury concentration was 46.685±3.653, 56.357±4.110, 81.267±2.818, 168.706±4.327 mg/m³ in workshop, control room, up and down floor of cells respectively. Because workers have been exposed to both type of mercury, the accumulative was carried out. Total mercury exposure in workshop, control room, up and down floor of cells were 49.143±3.882, 66.303±5.038, 108.357±5.034, 187.452±5.307 mg/m³, respectively.

Conclusion: Threshold Limit Values TLV and Time Weighted Average (TLV-TWA) recommended air exposure value for mercury as 50 mg/m³ by NIOSH. This study showed that concentration of mercury in air was higher than recommended level in all units, apart from workshop area. Further researches need to be carried out to find health and clinical side effects of high mercury pollution exposed subjects.