Workplace Assessment of Naphtha Exposure in a

Journal of Environmental Science and Engineering, 5 (2011) 400-409

Workplace Assessment of Naphtha Exposure in a Tyre Manufacturing Industry I. Norazura1, 2, H. Zailina1, L. Naing3, 4, N. Rusli3, 5, H.H. Jamal6, 7 and J. Mohd. Hasni6 1. Department of Community Health, Faculty of Medicine and Health Sciences, University Putra Malaysia, Selangor 43400, Malaysia 2. Department of Technology Management, Faculty of Manufacturing Engineering and Technology Management, Universitiy Malaysia Pahang, Lebuh Raya Tun Razak, Gambang, Kuantan, Pahang 26300, Malaysia 3. School of Dental Sciences, University Sains Malaysia, Kelantan 16150, Malaysia 4. Institute of Medicine, University Brunei Darussalam, Jalan Tungku Link, Gadong BE 1410, Brunei Darussalam 5. School of Medicine and Health Sciences, Monash University, Johor Bahru 80100, Malaysia 6. Department of Community Health, Faculty of Medicine, University Kebangsaan Malaysia, Kuala Lumpur 56000, Malaysia 7. International Institute for Global Health, United Nation University, UKM Medical Centre, Kuala Lumpur 56000, Malaysia Received: November 19, 2010 / Accepted: January 17, 2011 / Published: April 20, 2011. Abstract: A qualitative and quantitative workplace assessment was carried out to determine naphtha exposure in a tyre manufacturing industry. A qualitative chemical health risk assessment was conducted to identify naphtha hazard at the workplace. Quantitative assessment using Portable VOC Monitor, Automatic Sampling Pump and personal air sampling pump was used to determine VOC concentrations, organic solvents, and individual air naphtha respectively. The risk rating of naphtha was estimated to be 5. The mean VOC concentration was in the range of 2.43 to 92.93 ppm. Repair area had the highest VOC concentration while the lowest was in the moulding area. Each work station had significant differences for VOC concentrations (p < 0.001). Laboratory analysis found various solvents including 2-methyl pentane, hexane, methyl cyclopentane, heptane, cyclohexane and toluene which were present in the liquid naphtha. Only xylene has been detected in the making and moulding areas with a range of 2 to 5 ppm. Meanwhile, the air naphtha concentrations of the exposed workers were significantly higher than those unexposed. The risk of naphtha exposure was qualitatively significant and not adequately controlled. Naphtha was detected in all work stations since it is the main solvent used. The “Repair Area” was significantly more contaminated than the other area. Key words: Environmental monitoring, risk assessment, volatile organic compound (VOC), naphtha, personal air sampling.

1. Introduction Majority of industrial solvents are volatile and the common term “volatile organic compounds (VOC)” covers an extensively large group of compounds. VOC is a class of organic compounds with boiling points from 50 to 100 ℃ up to 240-260 ℃ depending on the sampling and analytical techniques [1]. A high-capacity to dissolve lipid-soluble materials as Corresponding author: H. Zailina, professor, research field: occupational health risk assessment. E-mail: [email protected].

well as sufficient volatility to permit simple removal of the solvent is the major requirements for solvent applications in several industries. Industrial operations of a number of industries are closely related with the use of organic solvents, as an important group of industrial chemicals. Industrial solvents have a wide applications in the manufacture of a variety of products, for example cosmetics, detergents and soaps, drugs, dyes, pigments, explosives, fertilizers, inks, pesticides, paints, plastics, shoe, tyre and others. Thus, organic solvents play an important role in the rapid development

Workplace Assessment of Naphtha Exposure in a Tyre Manufacturing Industry

of the industrial sectors. Naphtha is an organic solvent which is classified as petroleum distillates group, obtained by fractional distillation of petroleum. Petroleum distillate is composed of several hundred aliphatic and aromatic hydrocarbons, used as cleansing agent, thinner, paint, adhesive, fuel and other applications especially in industrial setting. Basically, there are three types of naphtha which are used in industrial setting: coal tar naphtha (heavy), wood naphtha (intermediate) and petroleum naphtha (light). Naphthas are used as organic solvents for dissolving or softening rubber, oils, greases, bituminous paints, varnishes and plastics [2]. In tyre manufacturing industry, hydrotreated light naphtha made up of aliphatic hydrocarbon (n-hexane) and aromatic hydrocarbons (benzene, ethylbenzene) is used as an adhesive, cleansing as well as segregative agent [3]. In other rubber-based industry, it is demonstrated that extraction naphtha was among the predominant volatile compounds in the analysis of 4 brands of glue used as adhesives in repairing of rubber conveyer belts [4]. Therefore, this workplace assessment plus exposure assessment within the individual breathing zone is necessary as an early preventive measure of controlling or maintaining the acceptable level of contaminants concentrations.

2. Materials and Methods Pre-assessment using Chemical Health Risk Assessment (CHRA) concept was applied to identify naphtha hazard as well as to assess naphtha exposure among workers in a tyre manufacturing industry in Malaysia. This consisted of determining the degree of naphtha hazard, assessing the exposure and evaluating the existing control measures. This exposure assessment was implemented by considering the following factors: (i) the likelihood of contact of the work unit with naphtha; (ii) how naphtha is released into the work environment; (iii) the method of handling naphtha; (iv) the way naphtha enters the body; (v) the

401

frequency and duration of exposure and (vi) the intensity or magnitude of each exposure. Since the exposure level can be influenced by the adequacy of control measures at the workplace, the existing control measures were assessed whether they are adequate or not in terms of their suitability, use, effectiveness and maintenance [5]. A walk-through survey was initially done to observe the working environment of the plant and workers’ job activities throughout the tyre manufacturing process to identify various monitoring stations involving naphtha used for the environmental monitoring in this industry. Area sampling was carried out using direct reading sampler namely Portable VOC Monitor (MiniRAE 2000), Model PGM 7600 using a Photo-Ionization Detector to monitor volatile organic compound (VOC), while Automatic Sampling Pump Model ASP-2000 (SampleRAE) was used to monitor the selected organic solvents [6]. It gives real time measurements and activates alarm signals whenever the exposure exceeds preset limits. This area sampling was carried out in several work areas using naphtha. The monitoring was conducted in each work area for 15 minutes. The protocol for sampling activities was carried out according to NIOSH/JICA [7]. Work area units using naphtha, its distribution and action as well as work areas of workers were identified. Sampling points were carried out on the intersections of horizontal and vertical lines at an interval of six meters throughout the industry. Air samples were measured at 100 cm above the floor for 15 minutes each by using direct reading samplers. Sampling was conducted during work operations. A bulk sample of liquid naphtha was collected for detailed analysis of organic solvents using Gas Chromatography Mass Spectrometry (GC-MS). The organic solvent analysis was carried out using the NIST Standard Reference Database 1A, NIST/EPA/NIH Mass Spectral Library (NIST 98) and NIST Mass Spectral Search Program Version 1.6 [8]. Personal air sampling pump was used for the active

402


sampling of naphtha as recommended in guidelines on monitoring of airborne contaminant [9]. The determination of time-weighted average (TWA) concentrations of naphtha in the worker’s breathing zone was made using a charcoal tube (100/50 mg sections, 20/40 mesh) as an absorbent. According to NIOSH Manual of Analytical Methods #1500 [10], ends of the sampler was broken before sampling and was attached to personal air sampling pump Model PAS-500 with flexible tubing. Then, the personal pump was attached to worker’s lapel throughout an 8-hour work shift for 2 hours. Samples were collected at a maximum flow rate of 0.2 liter/minute (TWA) until a maximum collection volume of 4 liters was reached. After 2 hours sampling, the samplers were capped with plastic caps and packed securely for shipment before analyzing in the laboratory For the laboratory analysis, the concentration of air naphtha from the sorbent tube was analyzed by using gas chromatography with flame ionization detector (GC/FID). This laboratory analysis was carried out in Industrial Hygiene Analytical Laboratory according to the standard methods adopted from NIOSH Manual of Analytical Methods #1500 [10].

3. Results

Table 1 Application of naphtha in several work units. Work process Application of naphtha used Cut plies for bead fillers To separate the stuck plies Assemble ply cut into To separate stuck plies pocket To apply on bead surface To apply on the tread joint before consolidating To be used during turn back of Making raw cover pockets To apply on pocket surface before application of treads/sidewall To decoy the raw cover from the former To spray onto surface of raw cover Orbi stripping prior to application of orbistrip compound To clean or wipe raw cover before Raw cover moulding loading and curing To be used during cleaning or Spraying cover wiping raw cover at bead region before sending for moulding (1) Repair or rework on To wipe the tyre after ironing defective tyres To clean or wipe finished repaired (2) Buffing defective tyre area of the tyre To clean the buffed spots Table 2 Hazard rating for naphtha. *Physical *Classification *Risk *Skin form of hazard phrases notation R36, R45 R48/20/21, Yes Liquid Toxic R62 R65, R67

Hazard rating 4

*Source: MSDS, 2006. Table 3 Magnitude and exposure ratings for naphtha*.

3.1 Chemical Health Risk Assessment Observation through a walk-through survey showed that tyre manufacturing process uses naphtha as a main raw material during mixing, making, repairing and finishing processes. Table 1 shows the use of naphtha in several work units. Results from the workplace assessment based on the qualitative Chemical Health Risk Assessment (CHRA) [5] process showed that hazard rating (HR), magnitude rating (MR), and exposure rating (ER) were 4, 5, and 5 respectively (Tables 2 and 3). From the risk matrix table, the risk rating (RR) of naphtha exposure for this qualitative estimation was 5, and was concluded as significant and not adequately controlled (C3). This assessment was based on the observation during storage, movement,

Suitable and Maintenance effective testing and Yes/No examination Eyes None No Skin Thermaprene glove No Yes Inhalation Fan No Yes Ingestion Safe work practice Yes Yes *Frequency of entry = 4-7 hr/shift; degree of chemical release = high; degree of contact/inhale = high; MR = 5; ER = 5. Routes of Existing controls entry

handling and using, transportation and disposal of naphtha. Naphtha is stored at the central material store, transferred to the naphtha booth as an intermediate area of storage before used by serviceman using specified container. The degree of chemical release was found to be high as naphtha were kept beside worker in uncovered container. The degree of chemical absorbed

403


was also high due to heavy work. As reported, there were cases of chemical splashes. Assessing exposures during normal operation or spillage, leaks or accidental entry into the body were considered. 3.2 Occupational Profile Further statistical analysis based on questionnaires was carried out to compare the occupational exposure and other related factors between the exposed and unexposed groups. More than half of the exposed group (86.5%) worked in shift (Table 4) since the production line operated for 24 hours. There were 3 shifts which were scheduled by the management division. This working shift was significantly different between the exposed and unexposed groups (p < 0.001). It was also found a significant difference in terms of the type of work handling as well as the nature of work between both groups (p = 0.002 and p < 0.001 respectively). Respondents in both groups mainly performed their job activities manually; 58.8% for the exposed group while 41.2% for the unexposed group. However, in term of the nature of work, the percentage of doing moderate work was the highest (81.7%) among the exposed group. Meanwhile, the unexposed group performs mainly the light work (84.5%). From the 119 exposed group, 47.9% of them were exposed to naphtha for more than 4 hours during their work shift, while 52.1% were exposed for less than 4 hours along their daily working shift.

Table 4 Working condition of respondents. Variable

Exposed group (N = 119) Freq. (%)

Unexposed 2 a χ group (df) (N = 72) Freq. (%)

p

Shift work Yes 96 83 (86.5) 13 (13.5) 47.95 < 0.001*** No 95 36 (37.9) 59 (62.1) (1) Type of work handling Manual 148 87 (58.8) 61 (41.2) 9.90 0.002** Semi37 32 (86.5) 5 (13.5) (1) automatic Nature of work Light 58 9 (15.5) 49 (84.5) 83.61 < 0.001*** Moderate 93 76 (81.7) 17 (18.3) (2) Heavy 37 34 (91.9) 3 (8.1) a Chi-square test for independent; ** Significant at p < 0.01; *** Significant at p < 0.001. Table 5 Perception on naphtha exposure in the workplace. Variable

n

Exposed group (N=119) Freq. (%)

Unexposed 2 a χ group (df) (N=72) Freq. (%)

Smell of chemical Yes 96 79 (82.3) 17 (17.7) No 68 26 (38.2) 42 (61.8) Not sure 27 14 (51.9) 13 (48.1) Worry about own health and safety Yes 86 68 (79.1) 18 (20.9) No 74 30 (40.5) 44 (59.5) Not sure 26 19 (73.1) 7 (26.9) Feel better outside workplace Yes 73 57 (78.1) 16 (21.9) No 39 20 (51.3) 19 (48.7) No diff. 75 42 (56.0) 33 (44.0) Smoking habit Yes 110 71 (64.5) 39 (35.5)

3.3 Individual Factors Table 5 shows the factors related to the individual safety and health concern on the exposure to naphtha. Most of them (66.4%) were affected by the smell of chemical in their work environment. More than half gave the negative perception on their current health status (57.1%). A total of 57 (47.9%) respondents felt better outside the workplace. In addition, the perception of the exposed group was significantly different than the unexposed group (at least p = 0.004). Nevertheless, both groups had poor habit such

n

No

71

44 (62.0) 27 (38.0)

p

34.36 < 0.001*** (2)

26.64 < 0.001*** (2)

11.05 0.004** (2)

0.12 (1)

0.725

a

Chi-square test for independent; ** Significant at p < 0.01; *** Significant at p < 0.001.

as smoking. Both groups had high percentage of smokers (exposed group = 59.7%; unexposed group = 54.2%) and the mean number of cigarette smoked daily showed no significant difference. 3.4 Environmental Air Monitoring Environmental air monitoring using direct reading

404


sampler was carried out in several work stations that involved naphtha application (Table 6). It was shown that this industry was exposed to volatile organic compound (VOC) since all work stations had environmental concentration of at least 4.00 ppm, with the median of 5.20 (IQR 8.25) ppm (Table 7). There were significant differences in VOC concentrations between the work stations (p < 0.001) (Table 8). The “repair” area had the highest VOC concentration while the “moulding” area had the lowest VOC. Laboratory analysis of a bulk sample of liquid naphtha found a variety of the mixtures of organic solvents such as 2-methyl pentane, hexane, methyl cyclopentane, heptane, cyclohexane and toluene which were present in Table 9. In the contrary, only 3 organic solvents namely n-hexane, benzene and methyl benzene were cited in the Material Safety Data Sheet (Table 10). N-hexane represented the highest concentration (10.00-30.00%) as compared to others. Surprisingly, only xylene had been detected mainly in the making and moulding areas with the range of 2 to 5 ppm (Table 11). 3.5 Personal Air Sampling Personal exposure assessment was carried out among the workers from each work stations. Respondents Table 6 industry. Work unit

Monitoring stations in tyre manufacturing

Function/task Make the layers of plystock onto the wheel 1. Making I rim to maintain the shape of the tyre to form the uncured tyres. Make the layers of plystock onto the wheel 2. Making II rim to maintain the shape of the tyre to form the uncured tyres. Rolling of the uncured rubber onto a sheet of 3. Plystock fabric to form a continuous sheet of rubber preparation coated fabric and then these sheets are cut by (pocket) the cutter into appropriate lengths and at the proper angle. Trim the finished tyres, to remove excess 4. Repair rubber and doing inspection of the finished tyres for defects and repairs. Spraying tyres with mold release agents to 5. Cover spray prevent them from sticking to the curing presses. Tyres are cured or vulcanized in molds under 6. Moulding heat and pressure to produce the final product.

Table 7 Volatile organic compound (VOC) concentrations at various locations in the tyre manufacturing industry. Station name Making I Making II Plystock preparation (pocket) Repair Cover spray Moulding

VOC concentrations (ppm) (sample period = 15 minute/station) Minimum Maximum Mean (s.d) 2.40 31.80 9.27 (8.35) 6.10 16.40 9.82 (3.03) 2.50

32.10

2.20 3.00 1.10

546.10 18.30 4.00

5.63 (7.47) 92.93 (153.63) 8.55 (4.85) 2.43 (0.91)

Table 8 Comparing VOC concentrations between work stations in the tyre manufacturing industry. Work station Making I Making II Plystock preparation (pocket) Repair Cover spray Moulding a

n Median (IQR) X2 statistic (df)a P valuea 15 4.80 (9.10) 40.83