Salāmat-i kār-i Īrān (May 2020)
Quantitative health risk assessment of respiratory exposure to 1,3-Butadiene in a petrochemical industry
Abstract
Background and aims: In recent decades, air quality in different work environments has been a major concern. It is clear that the chemical materials used in industries have a profound effect on the quality of workplace air. In 1942, the number of identified chemicals was about 600,000, in 1947 it was about 4 million, and in 2011 it was about 18 million, while the number of new chemical compounds increased from 1,000 to 2,000 annually. Many people around the world are exposed to a variety of chemicals in the various working environments. Exposure to these substances can lead to numerous health and carcinogenic effects on individuals. Among these substances, volatile organic compounds are one of the main contributors to air pollution and due to high vapor pressure, high evaporation rate and rapid release into the environment, many people are exposed and consequently have irreversible effects on their health in various occupations. Petrochemical industry is one of the industries where workers are exposed to high levels of chemical pollutants in their respiratory air. One of the hazardous volatile organic compounds used in workplaces, including petrochemicals, is 1,3-butadiene (molecular formula: C4H6). 1,3-Butadiene is a colorless gas with smells like gasoline. Many international agencies and government organizations, including the International Agency for Research on Cancer (IARC), have identified this chemical as a human carcinogen by inhalation and placed it in Group 1 of carcinogens. Health effects of this compound include stimulation of the nervous system, eyes, nose, airways, asthma, fatigue, low blood pressure, and heart rate as well as atrophy in the ovaries. Today, many international organizations, including the World Health Organization (WHO) and the US Environmental Protection Agency (USEPA), consider the use of quantitative risk assessment methods as the legal basis for chemical compounds. Generally, the health risk assessment process involves several steps, first identifying the existing hazards, then measuring the individualchr('39')s exposure, finally determining the relevant factors and measuring and evaluating the individualchr('39')s exposure to a particular substance, using different risk assessment methods, graphs, and dose-response values, the probability of adverse effects in the population is calculated. Therefore, due to the deleterious effects of the 1,3- butadiene on the health of those working in the petrochemical industry, and the lack of similar studies in Iran to assess the health risk of the respiratory exposure to 1,3-butadiene in the petrochemical industry, the present study aimed to assess the health risk of occupational exposure to 1,3-butadiene vapors in a petrochemical industry in Iran. Methods: This cross-sectional study was conducted in the petrochemical industry that producing copolymer ABS (acrylonitrile, butadiene, styrene) in Iran in 2018. To determine the respiratory exposure of participants to 1,3-butadiene, NIOSH 1024 method was used. Samples were collected by surface adsorption using adsorbent tubes containing activated charcoal of coconut (600 mg) and manufactured by SKC UK. It should be noted that similar exposure groups were used to assess individual exposure. Sample Size for research according to the proposed model of the National Institute of Occupational Safety and Health (SEG) and based on the number of workers in each occupational exposure group, were estimated 150 samples of 50 workerschr('39') respiratory air. At the sampling site, both sides of the sampling tube were broken and connected to an individual sampling pump made by SKC and calibrated using a soap bubble flowmeter at a flow rate of 200 ml/min according to the sampling method. After sampling, the content of activated charcoal in both front (400 mg) and rear (200 mg) sections of the sample tube was transferred to separate 5-ml vials. Then, by using the optimal NIOSH 1024 method, the extraction of the analyte was carried out by using 4-ml methylene chloride as an extraction solvent. Finally, 1μl of the sample with a 10μl gas-tight syringe manufactured by Hamilton Company was injected into the Gas Chromatography-Flame Ionization Detector (GC-FID) (model CP-3800 gas chromatograph and FID detector, Varian Technologies, Japan). Assessment of occupational exposure to 1,3-butadiene: In the present study, the occupational exposure limit for 1,3-butadiene (TLV - TWA) was 2 ppm (4.42 mg/m3) based on values reported by the American Conference of governmental Industrial Hygienists (ACGIH). In the present study, occupational exposure index was calculated for each individual. Because the TLV-TWA values are provided with the assumption of working 8-hours a day and 5-days per week, if the working hours per week were more than 40 hours, the TLV-TWA value was corrected by using the Brief and Scala model. health risk assessment of occupational exposure to 1,3-butadiene: The quantitative risk assessment methodology proposed by the US Environmental Protection Agency (USEPA) has been used to assess the health risk of exposure to 1,3-butadiene. Hazard Quotient (HQ) index was used to calculate the health risk of occupational exposure to 1,3-butadiene. Health risk is defined as the ratio of chronic daily intake for non-carcinogenic effects to the reference dose. Chronic daily intake (CDI) indicates exposure to a mass of matter per unit of body weight and time in a relatively long period. Inhalation reference dose was derived from the inhalation reference concentration (RfC). Inhalation reference concentration was 2 × 10-3 mg.m-3 for 1,3-butadiene according to Integrated Risk Information System (IRIS) databank. In the present study, information such as exposure duration, body weight, exposure time, and exposure frequency was collected using a questionnaire. The average inhalation rate ranged from 15.7 to 16 cubic meters per day depending on the age of the participants, according to the values presented in the EPA exposure factors handbook. The average lifetime was 70 years. Finally, data analysis was performed using IBM SPSS Statistics Version 25. Descriptive statistics (mean, standard deviation and frequency) were presented. Kruskal-Wallis test and Spearmanchr('39')s correlation coefficient were used at the significant level of 0.05. Results: The mean respiratory exposure to 1,3-butadiene during work shift among all participants was 560.82 ± 811.36 µg.m-3 and in all cases, it was below the corrected occupational exposure limit based on job characteristics. Also, the mean exposure index among all subjects was calculated to be 0.198 ± 0.25 and in all cases, it was lower than the permitted level. The results showed that the highest average respiratory exposure was in the safety and fire-fighting station worker. the average concentration of 1,3-butadiene in the workerschr('39') respiratory air in the safety and fire-fighting station was 1791.42 μg.m-3. After the safety and fire-fighting station workers, the highest average concentration of 1,3-butadiene was in the respiratory air of workers in the dryer, compound 1, laboratory, poly-butadiene latex and compound 2 units with exposure index values of 0.38, 0.277, 0.256, 0.223 and 0.189 respectively. Mean and standard deviation of hazard quotient among all participants was 10.82 ± 14.76. It was found that 60% of all exposed workers were in the unacceptable health risk level and 40% were in the acceptable risk level. The highest average of HQ was related to the safety and fire-fighting station workers with a value of 36.57. After the mentioned unit, the highest value of calculated HQ was observed in the dryer, laboratory, compound 2, installation and compound 1 with the values of 18.51, 16.01, 12.23, 11.57 and 10.82 respectively. The lowest HQ in the present study was obtained in the workers of packing, mechanical repair and coagulation units with the values of 0.18, 0.58 and 1.39 respectively. Among all examined units, the average non-carcinogenic risk values in the packing and mechanical repair units were lower than the permissible limit (HQ < 1.0). Conclusion: The results of the present study demonstrated that the health risks associated with exposure to 1,3-butadiene in most of the workers (60%) were in the unacceptable health risk level. Therefore, application of suitable control strategies such as design and implementation of appropriate dilution and local ventilation systems due to the non-standardization of all existing ventilation systems in the industry to reduce the level of respiratory exposure of workers to 1,3-butadiene vapors and consequently, the reduction in the amount of health risk caused by exposure to this compound and the use of quantitative health risk assessment methods as a basis for judging the levels of respiratory exposure to hazardous compounds (especially carcinogens due to their high potential risk rates) and prioritizing the various units for the control measures is essential.
