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Estimation of heavy metal exposure in workplace and health risk exposure assessment in steel industries in Iran
Measurement 102 (2017) 286–290
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Estimation of heavy metal exposure in workplace and health risk exposure assessment in steel industries in Iran Narjes Alsadat Mousavian a,⇑, Nabiollah Mansouri a, Farhad Nezhadkurki b a b
Department of HSE, Science and Research Branch, Islamic Azad University, Tehran, Iran Department of Environment, Yazd University, Yazd, Iran
a r t i c l e
i n f o
Article history: Received 22 June 2016 Received in revised form 20 September 2016 Accepted 10 February 2017 Available online 14 February 2017 Keywords: Inhalation PM measurement Steel industry Workplace
a b s t r a c t Measuring air pollutants such as heavy metals in the workplace, usually takes a long time, equipment and budget and due to variation in concentration, the results of short term researches are not reliable. To assess the health risk of workers in the smelting unit of an alloy steel factory to long term exposure to heavy metals, a simple, fast and less expensive method was used for evaluation with the combination of suspended dust analysis and PM10 measuring. The results showed that the highest and lowest concentration value was respectively recorded for Pb and Cd. Although, the average concentrations of heavy metals were lower than the recommended levels of occupational exposure, their occupational carcinogenic risks were different. The carcinogenic risk of Pb, Ni and Cd was low and acceptable, but was higher and unacceptable for Cr; therefore, using protective respiratory equipment and more efficient local ventilation was recommended. Ó 2017 Elsevier Ltd. All rights reserved.
1. Introduction Exposure assessment of heavy metals implies identifying and quantifying their sources, how they enter the human body and their adverse effects on human health [1]. The health risk is especially high for workers involved in smelting because of emissions of harmful pollutants such as heavy metals in the workplace. Hence, metal smelting is regarded as one of the most important anthropogenic heavy metal emission sources [2,3]. During the smelting process, heavy metals are evaporated from the metal matrix due low boiling point and high temperature [4]. In order to evaluate the health risk, further researches on dust exposure parameters are necessary to reduce the uncertainties associated in risk calculations [5]. Air pollution and cancer risk assessments were evaluated to determine the level of air pollution from particular metals in selected localities and the cancer potential as adverse effects on humans by observing metals over a period of time [6]. Suspended dust particles present in polluted air are known to cause adverse health effects in humans as they may be absorbed into the lung tissues while breathing. Moreover, harmful elements such as heavy metals in different forms, when inhaled or ingested, can cause serious health hazards to humans [7]. It is
⇑ Corresponding author. E-mail addresses: [email protected] (N.A. Mousavian), [email protected] (N. Mansouri), [email protected] (F. Nezhadkurki). http://dx.doi.org/10.1016/j.measurement.2017.02.015 0263-2241/Ó 2017 Elsevier Ltd. All rights reserved.
important to study air quality in areas around industries since significant releases of metals to the environment could represent a threat to local communities [8]. Risk calculations for exposure to heavy metals in Guangzhou, China with a simple exposure assessment model showed that the cancer risks of the bioavailable fractions of arsenic, chromium and cadmium were 3–33 times greater than the permissible levels, indicating serious health risks to the residents of this urban area [9]. Air pollutants in the workplace can gradually have undesirable effects on the health of workers. Industrial empowerment worsens the problem [10]. The concentration of some pollutants indoors can be greater than their concentration outdoors [11]. One of the major and important industries in pollutant emissions is the steel industry. Occupational health problems among workers in the steel industry have attracted the attention of investigators. In addition, the workers are sources of epidemiological studies for resident populations around steel industries. Workplace stress in iron and steel industry are numerous and typically include: inhalable agents (gases, vapors, dusts and fumes), working in confined spaces, lack of adequate ventilation, less occupational safety and health training and poor supervision over the use of personal protective equipment among others [12]. In the iron and steel industry, during the melting and casting operation, harmful pollutants such as gases, vapors, fumes, and smoke may be produced. The major pollutants are emitted during processes such as molding, mould drying, furnace preheating, Elec-
N.A. Mousavian et al. / Measurement 102 (2017) 286–290
tric Arc Furnace (EAF) and discharge among others [13–15]. Metals such as cadmium, lead, zinc, mercury, manganese, nickel and chromium can be emitted from a furnace as dust, fume or vapor or may be absorbed by particulates [16]. Particulate matter (PM) due to its physicochemical properties is one of the most important pollutants in the air that has undesirable effects on human health. In particular, particle composition and hazardous chemical contents can cause damage to the health of an exposed person [17]. More recent studies have confirmed the role of heavy metals’ toxicity in PM [6,18,19]. The deleterious effects of heavy metals on human health have been demonstrated in many ways. Exposure to these pollutants causes acute and chronic toxicity and many diseases such as neurological disorders, food deficiency, hormone imbalance, obesity, abortion, cardiopulmonary disease, liver and kidney damage, allergies and asthma, chronic viral infections, reduction of body’s tolerance, infertility, anemia and fatigue, weakened immune system, genetic damage, premature aging, memory loss, osteoporosis, hair loss, insomnia and different kinds of cancer [2,20] and mental hypogenesis in children and death [21]. As Abdel-Rasoul et al. (2009) point out, frequently recorded health disorders among iron and steel industry workers include: respiratory (66%), skin problems (31%) and noise-related hearing impairment [22]. Dinis and Fiuza (2011) [1] posited that longterm exposure can cause slower progressive physical, muscular, and neurological degenerative processes. Allergies may also occur and repeated long term contact with some metals or their compounds may become carcinogenic. Liu et al. (2013) [23] reported the effect of outdoor air pollution in the vicinity of a steel plant on cardiovascular physiology in Sault Ste. Marie, Canada. There is evidence that exposure to irritating dust and fumes may also make steelworkers more susceptible to a reversible narrowing of the airways (asthma) which over time may become permanent [24,25]. Shrivastava (2009) [13] reported mortality from lung cancer in steel industry workers due to exposure to chromium and PAHs (Polycyclic Aromatic Hydrocarbons). In some studies, exposure data during melting in stainless steel manufacture was recorded as mean dust concentration of 2.3 ± 1.3 and 1.8 mg/m3. Also, Cr concentration in chemical dust composition was reported as 30 mg/m3 [26]. Aiming to evaluate exposure risk of workers to heavy metals such as lead (Pb), chromium (Cr), nickel (Ni) and cadmium (Cd) emitted from iron and steel processes, this study was conducted to assess the smelting unit of Iran Alloy Steel Industries (IASI) in 2012–13. This metallurgical industrial complex is located 25 km northwest of Yazd city, Iran. The smelting unit of IASI has 3 electric-arc type furnaces with an annual mean production of 352,000 tons of different kinds of steel. The factory utilizes first class iron slab along with ferrous metal scrap mainly from old automobile waste parts as its primary material in percentages based on availability and desired productions. The present study focused on the estimation of heavy metal exposure in workplace and health exposure risk assessment among workers of alloy steel factory of Iran. A simple and fast method have been applied in combination of suspended dust analysis and PM10 measuring-PM10 is particulate matter 10 mm or less in diameter. PM10 concentration has been measured in two separate seasons (winter and summer). Three samples of dust from various locations in saloon that have the highest dust concentration among all the section that there is not air current were selected and analysed. For obtaining average dust breathing, TSI device was used and various samples during one shift in different location were used and for assessment of health exposure risk we applied combination of formulas.
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2. Material and methods 2.1. Method of estimation It is obvious that the particulate containing heavy metals is probably available in the workplace area. The ground surface particulate matter (PM) is usually cleaned or resuspended due to different activities in the workplace, but there are some microsurfaces in far-to-reach areas inside the workplace which contain some suspended dust even for years. Passive sampling from these points and analyzing them for heavy metals content could give a more realistic conditions of dust composition (special pollutants) which the workers are exposed to during working hours. However, there is some uncertainty in the method especially unknown age of accumulated dust. It is obvious that the result of analyzing these types of dust composition can give more accurate composition of dust inhaled by workers over long working years than sampling over short periods for assessing their exposure. PM levels, which could penetrate the lungs can be measured by a size selective aerosol monitor and then multiplied by the average mean of PM10 mass at breathing height in the workplace and by composition percentage of any kind of dust content such as heavy metals to result in the concentration of that pollutant in the air of the workplace. It is shown in Eq. (1).
CAlong term ¼ PM10mass X %Adust
ð1Þ
where CAlong term: is concentration of pollutant A for long term exposure in mg/m3; PM10 mass: is average mean concentration of PM10 in the breathing zone workplace air; %A Dust: is the mass percentage of pollutant A in suspended dust. 2.2. Sampling and analyses The smelting unit in the IASI includes 3 main EAF with an average of 130 workers, which work in 3 separate shifts in a big unified saloon. Although a local ventilation system evacuates the huge amount of polluted emission from the furnaces, usually the air inside the saloon is dusty and impure. Based on the presence of workers in their work stations, 21 points were selected as fixed stations for measuring PM10. PM10 concentration was measured at selected stations at about 170 cm height breathing zone, with 5 min measuring time for each station. The measuring program was carried out 4 times within 2 h interval during daily work shifts and was repeated for two separate seasons (winter and summer) using a DustTruk Aerosol Monitor, TSI-8520. In order to analyse heavy metals including Pb, Cr, Ni and Cd, three samples of suspended dust from 21 locations in the workplace and near the fixed stations were collected in glass dishes. The other samples were collected from different locations. This diversity in site selection for the dust sample collection caused the result to be near the real pollution rate that exists in the workplace during the study period. Dust samples were thoroughly mixed and then extracted with nitric acid using ISO9588 analysis method. To minimize errors and eliminate the effect of interference of probable contamination in the extraction process, two control samples were used during extraction according to the U.S. National Institute for Occupational Safety and Health guideline (NIOSH) [27]. The heavy metals content of extracted solutions was analysed using the Atomic Absorption Spectrophotometer Varian Spectra Model 100/200 by acetylene-air flame. To initially assess the health risk of exposure to heavy metals, the Average Daily Intake (ADI) of each heavy metal via direct inhalation was determined using Eq. (2) [1], as follows:
ADI ¼ ðCA IR ET EF ED 0:001Þ=ðBW AT 365Þ
ð2Þ
288
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where ADI = the average daily intake of the contaminant via direct inhalation (mgkg1day1); CA = the total air concentration over exposure duration (mgm3); IR = the inhalation rate (m3h1) = 20 m3d1 for adults; ET = the exposure time (hd1) = 8 hd1; EF = the exposure frequency (dy1) = 180 dy1; ED = the exposure duration (y); 0.001 = the unit conversion factor (lgmg1) and conversion factor (daysyear1). Heavy metal concentration of collected dust from inside the saloon was measured in lgl1 and then converted to lgm3. Initially, concentration of metal in 50 cc of extracted solution was obtained. For example, the concentration of cadmium was 0.0096 mgl1 which became 0.00048 mgl1 in 50 cc of extracted solution. This amount of metal was in 0.1 mg of the dust sample. As the average mean value of PM10 inside the saloon was 0.611 mgm3, Cd concentration in the saloon was estimated to be 1.5 mgm3. The Incremental lifetime cancer risk (ILCR) was estimated using Eq. (3) [6] thus:
ILCR ¼ ADI ICPF
ð3Þ
where: ILCR = Incremental lifetime cancer risk; ICPF = inhalation cancer potency factor, which signifies the carcinogenic potential of the distinct pollutant; Table 1 shows the inhalation cancer potency factor for studied metals presented by the California Environmental Protection Agency [6]. Acceptable carcinogenic risk for occupations is 0.00001, i.e. one in 100,000 people. In the next step, Eq. (4) was used to calculate non-carcinogenic risk [28].
Noncancerous Hazard Quotient ðHQ Þ ¼ ADI=RFD
ð4Þ
where RFD = reference dose at (mgkg1day1) Therefore, HQ 1 suggests unlikely adverse health effects, whereas HQ > 1 suggests the probability of adverse health effects. The inhalable RFD rate can be obtained using Eq. (5) according to RFC [29]. 1
RFDi ðmg kg
1
day Þ ¼ ðRFC InHRÞ=Bw
ð5Þ 3
where RFC = Reference concentrations at mgm ; InHR = inhalable rate at m3d1 = 20 m3d1; Bw = average body weight in kg = 70 kg The values of calculated RFCs and RFD are presented in Table 2. 3. Results and discussion In most studies through descriptive methods and under consideration some aspects and effects or with measuring pollutants by personal sampling method during a shift, had estimated pollutant values and their risk assessment in the iron and steel industry, whereas they ignore time and process changes over the years of performance of workers in the workplace. But performed procedure in this study, is on the basis of measuring and computation. In used method in this article, with the help of special environmental samples and measuring their metal contents, we have tried to
Table 1 Inhalation cancer potency factor for desired metals presented by California EPA. Metal
ICPF (mgkg1day1)
Cd Ni Pb Cr
15 0.91 0.042 510
calculate the average value of exposure of workers to heavy metals during the years of work in the melting saloon more precisely and to do a risk assessment on the basis of this data. The average respirable aerosols, PM10, inside the workplace were 0.611 ± 0.343 mg/m3 with a total range of 0.434–0.973 mg/ m3. Whereas, Rafiei et al. (2008) evaluated the levels of the indoor respirable particulate matter in Ahwaz Rolling and Pipe Mills Company, Iran a range from 1.65 to 7.64 mg/m3 [30]. As can be seen, the results of this study are much lower than the obtained averages from Rafiei et al.’ research. Separate means for summer and winter were 0.575 ± 0.308 and 0.647 ± 0.342 mg/m3, respectively. The overall PM10 concentration during winter was higher than summer because the smelting saloon doors and windows are usually closed in winter due to the cold weather which led to lower natural ventilation and high concentration of pollutants inside the workplace. The overall PM10 concentration- 0.311 mg/m3- in our study was lower than those measured by Koponen et al. (1980) [31] and Huvinen et al. (1993) [32] in similar factories that manufactured stainless steel which were 2.3 ± 1.3 and1.8 mg/m3, respectively [25]. Pal Singh et al. (2013) [33] also reported an average suspended particulate matter of about 24.8 mg/m3 among steel workers and Owoade et al. (2009) [34] measured mass concentration levels of PM10 from 86 to 8765 lg/m3 in a scrap iron and steel smelting industry in Lagos, Nigeria. Analysing 3 passive samples of dust gathered from all around the workplace showed mean percentages of Pb, Cr, Ni and Cd as 7.36, 6.55, 3.76 and 0.26%, respectively. Multiplying heavy metals percentages by total average of PM10 concentration measured at inside stations (Eq. (1)) resulted in long term heavy metals concentrations which, along with their occupational exposure standards are presented in Table 3. Comparing average concentrations of heavy metals with occupational exposure levels recommended by the Iranian Environmental and Occupational Health Center (IEOHC) and threshold limit values (TLVs) determined by the American Conference of Governmental Industrial Hygienists (ACGIH) showed that the concentrations of all metals were lower than the allowable levels. Lead and cadmium had the highest and the lowest mean concentrations of 45 and 1.5 mgm3, respectively. This was similar to the result of Triger et al.’s (1989) [35] study, which estimated the exposure to Cd and Pb in PM from steel industries to be more than any other elements. Owoade et al. (2009) [34] also showed that the Pb content of workplace air in a scrap iron and steel smelting industry was highest among other toxic metals. Nevertheless, the concentration of chromium in this study was higher than that measured by Cross et al. (1999) [26]. To assess the health risk of exposure to the studied heavy metals, the ADI, cancer risk from inhalation and non-carcinogenic effect or HQ of the metals were calculated using Eqs. (2)(4) and are presented in Table 4. Daily exposure to the studied metals, from the lowest to the highest were Cd < Ni < Pb = Cr. However, considering the acceptable carcinogenic risk for occupations, 0.00001, it is concluded that exposure to Cr via respiration in the IASI smelting workshop is accompanied with high carcinogenic risk whereas exposure to Pb, Ni and Cd were within acceptable carcinogenic levels. Similar results can be seen in similar researches by Sitas et al. (1989) [36] which showed an increased risk of lung cancer among casting workers compared with the general population and Pal Singh (2013) [33] who showed an increased risk of lung cancer among workers in the iron and steel industry. Contrary to this result, Adaramodu et al. (2012) predicted that Cd and Zn from e-waste, surface dust samples pose serious health risks to workers than other heavy metals such as Cr, Pb and Fe [37]. Also, Buranatrevedh (2010) showed that six types of metals (Al, Mn, Mg, Cu, Zn, Fe) just have non-carcinogenic risk in an aluminum production industry [38].
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N.A. Mousavian et al. / Measurement 102 (2017) 286–290 Table 2 RFCs and RFD for desired metals. Row 1 2 3 4 a b c
RFCs (mgm3)
Elements Cd Cr Pb Ni
Reference a
0.00002 0.0001 0.0015 0.00065
CAL EPA IRISb EPA OAQPSc CAL EPA
Selected metals
Concentration
ACGIH TLVa
2000 1998 2003 2000
0.0000057 0.000028 0.00043 0.00018
Pb Cr Ni Cd
45 40 23 1.5
50 50 50 2
Acknowledgements
IEOHC (2011)
This study was carried out with financial and moral support from the Iran Alloy Steel Company as the authors sincerely thank its management and respectable staff for their cooperation.
50 50 100 10
References
8-h TWAb
a
Calculated RFD (mgkg1d1)
California Environmental Protection Agency. Integrated Risk Information System. The Office of Air Quality Planning and Standards.
Table 3 Respirable concentration of Pb, Cr, Ni and Cd and recommended levels for occupational exposure (mgm3) in IASI, 2012–13.
b
Year
Threshold Limit Value. Time Weighted Average.
Table 4 Cancer risk and non-carcinogenic risk of Pb, Cr, Ni and Cd in IASI, 2012–13. Heavy metal
ADI (mgkg1d1)
Cancer risk from inhalation
HQ
Pb Cd Ni Cr
1 105 5 107 7 106 1 105
4 107 7 106 6 106 0.005
0.02 0.09 0.04 0.3
To assess the non-cancer health effect of exposure to heavy metals, the amount of HQ for all elements should be lower than 1. It means that the non-carcinogenic levels reported for the studied metals were not reasonable. The overall result of heavy metal exposure risk assessment was the same as the US National Institute of Occupational Health and Safety (2013) [39] view point, which showed the iron and steel industry as one of industries having the highest risk with its workers potentially exposed to high amounts of airborne chromium (VI). To minimize the risk of airborne particles containing Cr, the use of protective respiratory equipment such as PI or PII grade dust mask and more efficient local ventilation was recommended.
4. Conclusion This study was applied to workers who are exposed to heavy metals (Ni, Pb and Cd) in Iran Alloy Steel Company for estimation of heavy metal exposure in workplace and health exposure risk assessment. For obtaining this aim, at first PM10 concentration was obtained by extraction of 176 samples from 21 points in fixed stations and using of TSI-8520. The samples were extracted in one working shift and in two seasons (winter and summer). Also, three dust samples in 170 cm breathing height zone in different places were collected and analysed for Ni, Pb and Cd percentages. The results have shown that exposure to Ni, Pb and Cd in IASI melting saloon had very low carcinogenic risk, but exposure to Cr at unacceptable levels showed carcinogenic risk. Also, the studied metals showed weak non-carcinogenic effects. Hence, Cr should be considered a more hazardous occupational pollutant for steel workers.
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Measurement journal homepage: www.elsevier.com/locate/measurement
Estimation of heavy metal exposure in workplace and health risk exposure assessment in steel industries in Iran Narjes Alsadat Mousavian a,⇑, Nabiollah Mansouri a, Farhad Nezhadkurki b a b
Department of HSE, Science and Research Branch, Islamic Azad University, Tehran, Iran Department of Environment, Yazd University, Yazd, Iran
a r t i c l e
i n f o
Article history: Received 22 June 2016 Received in revised form 20 September 2016 Accepted 10 February 2017 Available online 14 February 2017 Keywords: Inhalation PM measurement Steel industry Workplace
a b s t r a c t Measuring air pollutants such as heavy metals in the workplace, usually takes a long time, equipment and budget and due to variation in concentration, the results of short term researches are not reliable. To assess the health risk of workers in the smelting unit of an alloy steel factory to long term exposure to heavy metals, a simple, fast and less expensive method was used for evaluation with the combination of suspended dust analysis and PM10 measuring. The results showed that the highest and lowest concentration value was respectively recorded for Pb and Cd. Although, the average concentrations of heavy metals were lower than the recommended levels of occupational exposure, their occupational carcinogenic risks were different. The carcinogenic risk of Pb, Ni and Cd was low and acceptable, but was higher and unacceptable for Cr; therefore, using protective respiratory equipment and more efficient local ventilation was recommended. Ó 2017 Elsevier Ltd. All rights reserved.
1. Introduction Exposure assessment of heavy metals implies identifying and quantifying their sources, how they enter the human body and their adverse effects on human health [1]. The health risk is especially high for workers involved in smelting because of emissions of harmful pollutants such as heavy metals in the workplace. Hence, metal smelting is regarded as one of the most important anthropogenic heavy metal emission sources [2,3]. During the smelting process, heavy metals are evaporated from the metal matrix due low boiling point and high temperature [4]. In order to evaluate the health risk, further researches on dust exposure parameters are necessary to reduce the uncertainties associated in risk calculations [5]. Air pollution and cancer risk assessments were evaluated to determine the level of air pollution from particular metals in selected localities and the cancer potential as adverse effects on humans by observing metals over a period of time [6]. Suspended dust particles present in polluted air are known to cause adverse health effects in humans as they may be absorbed into the lung tissues while breathing. Moreover, harmful elements such as heavy metals in different forms, when inhaled or ingested, can cause serious health hazards to humans [7]. It is
⇑ Corresponding author. E-mail addresses: [email protected] (N.A. Mousavian), [email protected] (N. Mansouri), [email protected] (F. Nezhadkurki). http://dx.doi.org/10.1016/j.measurement.2017.02.015 0263-2241/Ó 2017 Elsevier Ltd. All rights reserved.
important to study air quality in areas around industries since significant releases of metals to the environment could represent a threat to local communities [8]. Risk calculations for exposure to heavy metals in Guangzhou, China with a simple exposure assessment model showed that the cancer risks of the bioavailable fractions of arsenic, chromium and cadmium were 3–33 times greater than the permissible levels, indicating serious health risks to the residents of this urban area [9]. Air pollutants in the workplace can gradually have undesirable effects on the health of workers. Industrial empowerment worsens the problem [10]. The concentration of some pollutants indoors can be greater than their concentration outdoors [11]. One of the major and important industries in pollutant emissions is the steel industry. Occupational health problems among workers in the steel industry have attracted the attention of investigators. In addition, the workers are sources of epidemiological studies for resident populations around steel industries. Workplace stress in iron and steel industry are numerous and typically include: inhalable agents (gases, vapors, dusts and fumes), working in confined spaces, lack of adequate ventilation, less occupational safety and health training and poor supervision over the use of personal protective equipment among others [12]. In the iron and steel industry, during the melting and casting operation, harmful pollutants such as gases, vapors, fumes, and smoke may be produced. The major pollutants are emitted during processes such as molding, mould drying, furnace preheating, Elec-
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tric Arc Furnace (EAF) and discharge among others [13–15]. Metals such as cadmium, lead, zinc, mercury, manganese, nickel and chromium can be emitted from a furnace as dust, fume or vapor or may be absorbed by particulates [16]. Particulate matter (PM) due to its physicochemical properties is one of the most important pollutants in the air that has undesirable effects on human health. In particular, particle composition and hazardous chemical contents can cause damage to the health of an exposed person [17]. More recent studies have confirmed the role of heavy metals’ toxicity in PM [6,18,19]. The deleterious effects of heavy metals on human health have been demonstrated in many ways. Exposure to these pollutants causes acute and chronic toxicity and many diseases such as neurological disorders, food deficiency, hormone imbalance, obesity, abortion, cardiopulmonary disease, liver and kidney damage, allergies and asthma, chronic viral infections, reduction of body’s tolerance, infertility, anemia and fatigue, weakened immune system, genetic damage, premature aging, memory loss, osteoporosis, hair loss, insomnia and different kinds of cancer [2,20] and mental hypogenesis in children and death [21]. As Abdel-Rasoul et al. (2009) point out, frequently recorded health disorders among iron and steel industry workers include: respiratory (66%), skin problems (31%) and noise-related hearing impairment [22]. Dinis and Fiuza (2011) [1] posited that longterm exposure can cause slower progressive physical, muscular, and neurological degenerative processes. Allergies may also occur and repeated long term contact with some metals or their compounds may become carcinogenic. Liu et al. (2013) [23] reported the effect of outdoor air pollution in the vicinity of a steel plant on cardiovascular physiology in Sault Ste. Marie, Canada. There is evidence that exposure to irritating dust and fumes may also make steelworkers more susceptible to a reversible narrowing of the airways (asthma) which over time may become permanent [24,25]. Shrivastava (2009) [13] reported mortality from lung cancer in steel industry workers due to exposure to chromium and PAHs (Polycyclic Aromatic Hydrocarbons). In some studies, exposure data during melting in stainless steel manufacture was recorded as mean dust concentration of 2.3 ± 1.3 and 1.8 mg/m3. Also, Cr concentration in chemical dust composition was reported as 30 mg/m3 [26]. Aiming to evaluate exposure risk of workers to heavy metals such as lead (Pb), chromium (Cr), nickel (Ni) and cadmium (Cd) emitted from iron and steel processes, this study was conducted to assess the smelting unit of Iran Alloy Steel Industries (IASI) in 2012–13. This metallurgical industrial complex is located 25 km northwest of Yazd city, Iran. The smelting unit of IASI has 3 electric-arc type furnaces with an annual mean production of 352,000 tons of different kinds of steel. The factory utilizes first class iron slab along with ferrous metal scrap mainly from old automobile waste parts as its primary material in percentages based on availability and desired productions. The present study focused on the estimation of heavy metal exposure in workplace and health exposure risk assessment among workers of alloy steel factory of Iran. A simple and fast method have been applied in combination of suspended dust analysis and PM10 measuring-PM10 is particulate matter 10 mm or less in diameter. PM10 concentration has been measured in two separate seasons (winter and summer). Three samples of dust from various locations in saloon that have the highest dust concentration among all the section that there is not air current were selected and analysed. For obtaining average dust breathing, TSI device was used and various samples during one shift in different location were used and for assessment of health exposure risk we applied combination of formulas.
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2. Material and methods 2.1. Method of estimation It is obvious that the particulate containing heavy metals is probably available in the workplace area. The ground surface particulate matter (PM) is usually cleaned or resuspended due to different activities in the workplace, but there are some microsurfaces in far-to-reach areas inside the workplace which contain some suspended dust even for years. Passive sampling from these points and analyzing them for heavy metals content could give a more realistic conditions of dust composition (special pollutants) which the workers are exposed to during working hours. However, there is some uncertainty in the method especially unknown age of accumulated dust. It is obvious that the result of analyzing these types of dust composition can give more accurate composition of dust inhaled by workers over long working years than sampling over short periods for assessing their exposure. PM levels, which could penetrate the lungs can be measured by a size selective aerosol monitor and then multiplied by the average mean of PM10 mass at breathing height in the workplace and by composition percentage of any kind of dust content such as heavy metals to result in the concentration of that pollutant in the air of the workplace. It is shown in Eq. (1).
CAlong term ¼ PM10mass X %Adust
ð1Þ
where CAlong term: is concentration of pollutant A for long term exposure in mg/m3; PM10 mass: is average mean concentration of PM10 in the breathing zone workplace air; %A Dust: is the mass percentage of pollutant A in suspended dust. 2.2. Sampling and analyses The smelting unit in the IASI includes 3 main EAF with an average of 130 workers, which work in 3 separate shifts in a big unified saloon. Although a local ventilation system evacuates the huge amount of polluted emission from the furnaces, usually the air inside the saloon is dusty and impure. Based on the presence of workers in their work stations, 21 points were selected as fixed stations for measuring PM10. PM10 concentration was measured at selected stations at about 170 cm height breathing zone, with 5 min measuring time for each station. The measuring program was carried out 4 times within 2 h interval during daily work shifts and was repeated for two separate seasons (winter and summer) using a DustTruk Aerosol Monitor, TSI-8520. In order to analyse heavy metals including Pb, Cr, Ni and Cd, three samples of suspended dust from 21 locations in the workplace and near the fixed stations were collected in glass dishes. The other samples were collected from different locations. This diversity in site selection for the dust sample collection caused the result to be near the real pollution rate that exists in the workplace during the study period. Dust samples were thoroughly mixed and then extracted with nitric acid using ISO9588 analysis method. To minimize errors and eliminate the effect of interference of probable contamination in the extraction process, two control samples were used during extraction according to the U.S. National Institute for Occupational Safety and Health guideline (NIOSH) [27]. The heavy metals content of extracted solutions was analysed using the Atomic Absorption Spectrophotometer Varian Spectra Model 100/200 by acetylene-air flame. To initially assess the health risk of exposure to heavy metals, the Average Daily Intake (ADI) of each heavy metal via direct inhalation was determined using Eq. (2) [1], as follows:
ADI ¼ ðCA IR ET EF ED 0:001Þ=ðBW AT 365Þ
ð2Þ
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where ADI = the average daily intake of the contaminant via direct inhalation (mgkg1day1); CA = the total air concentration over exposure duration (mgm3); IR = the inhalation rate (m3h1) = 20 m3d1 for adults; ET = the exposure time (hd1) = 8 hd1; EF = the exposure frequency (dy1) = 180 dy1; ED = the exposure duration (y); 0.001 = the unit conversion factor (lgmg1) and conversion factor (daysyear1). Heavy metal concentration of collected dust from inside the saloon was measured in lgl1 and then converted to lgm3. Initially, concentration of metal in 50 cc of extracted solution was obtained. For example, the concentration of cadmium was 0.0096 mgl1 which became 0.00048 mgl1 in 50 cc of extracted solution. This amount of metal was in 0.1 mg of the dust sample. As the average mean value of PM10 inside the saloon was 0.611 mgm3, Cd concentration in the saloon was estimated to be 1.5 mgm3. The Incremental lifetime cancer risk (ILCR) was estimated using Eq. (3) [6] thus:
ILCR ¼ ADI ICPF
ð3Þ
where: ILCR = Incremental lifetime cancer risk; ICPF = inhalation cancer potency factor, which signifies the carcinogenic potential of the distinct pollutant; Table 1 shows the inhalation cancer potency factor for studied metals presented by the California Environmental Protection Agency [6]. Acceptable carcinogenic risk for occupations is 0.00001, i.e. one in 100,000 people. In the next step, Eq. (4) was used to calculate non-carcinogenic risk [28].
Noncancerous Hazard Quotient ðHQ Þ ¼ ADI=RFD
ð4Þ
where RFD = reference dose at (mgkg1day1) Therefore, HQ 1 suggests unlikely adverse health effects, whereas HQ > 1 suggests the probability of adverse health effects. The inhalable RFD rate can be obtained using Eq. (5) according to RFC [29]. 1
RFDi ðmg kg
1
day Þ ¼ ðRFC InHRÞ=Bw
ð5Þ 3
where RFC = Reference concentrations at mgm ; InHR = inhalable rate at m3d1 = 20 m3d1; Bw = average body weight in kg = 70 kg The values of calculated RFCs and RFD are presented in Table 2. 3. Results and discussion In most studies through descriptive methods and under consideration some aspects and effects or with measuring pollutants by personal sampling method during a shift, had estimated pollutant values and their risk assessment in the iron and steel industry, whereas they ignore time and process changes over the years of performance of workers in the workplace. But performed procedure in this study, is on the basis of measuring and computation. In used method in this article, with the help of special environmental samples and measuring their metal contents, we have tried to
Table 1 Inhalation cancer potency factor for desired metals presented by California EPA. Metal
ICPF (mgkg1day1)
Cd Ni Pb Cr
15 0.91 0.042 510
calculate the average value of exposure of workers to heavy metals during the years of work in the melting saloon more precisely and to do a risk assessment on the basis of this data. The average respirable aerosols, PM10, inside the workplace were 0.611 ± 0.343 mg/m3 with a total range of 0.434–0.973 mg/ m3. Whereas, Rafiei et al. (2008) evaluated the levels of the indoor respirable particulate matter in Ahwaz Rolling and Pipe Mills Company, Iran a range from 1.65 to 7.64 mg/m3 [30]. As can be seen, the results of this study are much lower than the obtained averages from Rafiei et al.’ research. Separate means for summer and winter were 0.575 ± 0.308 and 0.647 ± 0.342 mg/m3, respectively. The overall PM10 concentration during winter was higher than summer because the smelting saloon doors and windows are usually closed in winter due to the cold weather which led to lower natural ventilation and high concentration of pollutants inside the workplace. The overall PM10 concentration- 0.311 mg/m3- in our study was lower than those measured by Koponen et al. (1980) [31] and Huvinen et al. (1993) [32] in similar factories that manufactured stainless steel which were 2.3 ± 1.3 and1.8 mg/m3, respectively [25]. Pal Singh et al. (2013) [33] also reported an average suspended particulate matter of about 24.8 mg/m3 among steel workers and Owoade et al. (2009) [34] measured mass concentration levels of PM10 from 86 to 8765 lg/m3 in a scrap iron and steel smelting industry in Lagos, Nigeria. Analysing 3 passive samples of dust gathered from all around the workplace showed mean percentages of Pb, Cr, Ni and Cd as 7.36, 6.55, 3.76 and 0.26%, respectively. Multiplying heavy metals percentages by total average of PM10 concentration measured at inside stations (Eq. (1)) resulted in long term heavy metals concentrations which, along with their occupational exposure standards are presented in Table 3. Comparing average concentrations of heavy metals with occupational exposure levels recommended by the Iranian Environmental and Occupational Health Center (IEOHC) and threshold limit values (TLVs) determined by the American Conference of Governmental Industrial Hygienists (ACGIH) showed that the concentrations of all metals were lower than the allowable levels. Lead and cadmium had the highest and the lowest mean concentrations of 45 and 1.5 mgm3, respectively. This was similar to the result of Triger et al.’s (1989) [35] study, which estimated the exposure to Cd and Pb in PM from steel industries to be more than any other elements. Owoade et al. (2009) [34] also showed that the Pb content of workplace air in a scrap iron and steel smelting industry was highest among other toxic metals. Nevertheless, the concentration of chromium in this study was higher than that measured by Cross et al. (1999) [26]. To assess the health risk of exposure to the studied heavy metals, the ADI, cancer risk from inhalation and non-carcinogenic effect or HQ of the metals were calculated using Eqs. (2)(4) and are presented in Table 4. Daily exposure to the studied metals, from the lowest to the highest were Cd < Ni < Pb = Cr. However, considering the acceptable carcinogenic risk for occupations, 0.00001, it is concluded that exposure to Cr via respiration in the IASI smelting workshop is accompanied with high carcinogenic risk whereas exposure to Pb, Ni and Cd were within acceptable carcinogenic levels. Similar results can be seen in similar researches by Sitas et al. (1989) [36] which showed an increased risk of lung cancer among casting workers compared with the general population and Pal Singh (2013) [33] who showed an increased risk of lung cancer among workers in the iron and steel industry. Contrary to this result, Adaramodu et al. (2012) predicted that Cd and Zn from e-waste, surface dust samples pose serious health risks to workers than other heavy metals such as Cr, Pb and Fe [37]. Also, Buranatrevedh (2010) showed that six types of metals (Al, Mn, Mg, Cu, Zn, Fe) just have non-carcinogenic risk in an aluminum production industry [38].
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N.A. Mousavian et al. / Measurement 102 (2017) 286–290 Table 2 RFCs and RFD for desired metals. Row 1 2 3 4 a b c
RFCs (mgm3)
Elements Cd Cr Pb Ni
Reference a
0.00002 0.0001 0.0015 0.00065
CAL EPA IRISb EPA OAQPSc CAL EPA
Selected metals
Concentration
ACGIH TLVa
2000 1998 2003 2000
0.0000057 0.000028 0.00043 0.00018
Pb Cr Ni Cd
45 40 23 1.5
50 50 50 2
Acknowledgements
IEOHC (2011)
This study was carried out with financial and moral support from the Iran Alloy Steel Company as the authors sincerely thank its management and respectable staff for their cooperation.
50 50 100 10
References
8-h TWAb
a
Calculated RFD (mgkg1d1)
California Environmental Protection Agency. Integrated Risk Information System. The Office of Air Quality Planning and Standards.
Table 3 Respirable concentration of Pb, Cr, Ni and Cd and recommended levels for occupational exposure (mgm3) in IASI, 2012–13.
b
Year
Threshold Limit Value. Time Weighted Average.
Table 4 Cancer risk and non-carcinogenic risk of Pb, Cr, Ni and Cd in IASI, 2012–13. Heavy metal
ADI (mgkg1d1)
Cancer risk from inhalation
HQ
Pb Cd Ni Cr
1 105 5 107 7 106 1 105
4 107 7 106 6 106 0.005
0.02 0.09 0.04 0.3
To assess the non-cancer health effect of exposure to heavy metals, the amount of HQ for all elements should be lower than 1. It means that the non-carcinogenic levels reported for the studied metals were not reasonable. The overall result of heavy metal exposure risk assessment was the same as the US National Institute of Occupational Health and Safety (2013) [39] view point, which showed the iron and steel industry as one of industries having the highest risk with its workers potentially exposed to high amounts of airborne chromium (VI). To minimize the risk of airborne particles containing Cr, the use of protective respiratory equipment such as PI or PII grade dust mask and more efficient local ventilation was recommended.
4. Conclusion This study was applied to workers who are exposed to heavy metals (Ni, Pb and Cd) in Iran Alloy Steel Company for estimation of heavy metal exposure in workplace and health exposure risk assessment. For obtaining this aim, at first PM10 concentration was obtained by extraction of 176 samples from 21 points in fixed stations and using of TSI-8520. The samples were extracted in one working shift and in two seasons (winter and summer). Also, three dust samples in 170 cm breathing height zone in different places were collected and analysed for Ni, Pb and Cd percentages. The results have shown that exposure to Ni, Pb and Cd in IASI melting saloon had very low carcinogenic risk, but exposure to Cr at unacceptable levels showed carcinogenic risk. Also, the studied metals showed weak non-carcinogenic effects. Hence, Cr should be considered a more hazardous occupational pollutant for steel workers.
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