Noise and chemical solvents are serious health and safety concern among workers
in wooden furniture manufacturing (Fairfax, 1995, 1996).
The high noise-level emancipating from the use of many different types of machines
in the production process and the use of lacquers and paints, often the acid-curing
type, with high amounts of organic solvents (>50%), which is released to
the environment during the curing process, have strong effects on the workers
health and safety in the furniture factories (Eleftheriou,
2002; Thorud et al., 2005).
Noise sources in the furniture manufacturing factories includes: (1) Structural
vibration of machine frames, (2) aerodynamic turbulence of the rotating tools
and (3) dust and wood chips extraction system (Ratnasingam
and Scholz, 2008). Although, the factories and machinery (noise exposure)
regulation of 1989 of Malaysia, stipulates that the maximum permitted noise
exposure limit for workers in the woodworking industry should not exceed 90
dBA for 8 h period, its effectiveness to provide adequate hearing protection
to the workers remain debatable (Ratnasingam and Scholz,
2007; Anonymous, 2008). In woodworking environments,
where noise reduction measures implemented are often insufficient due to the
variable processing parameters, the use of hearing protection among workers
are highly recommended. Further, the woodworking industry is also, known to
be relatively low in investments into low-noise processing technologies and
tools, as hearing protection is often deemed as sufficient to safeguard the
workers hearing (Fairfax, 1995). Nevertheless, the reliability
of the noise exposure limit as stipulated in national regulations and the use
of hearing protection, as adequate protection for workers hearing remain debatable,
as reports on noise exposure of workers in the woodworking industry, particularly
wooden furniture manufacturing is relatively sparse (Ratnasingam
and Scholz, 2008).
On the other hand, chemical solvents exposure of workers is often from the
coating processes, using different types of lacquers such as nitrocellulose,
acid-curing, polyurethane and ultra-violet coatings to finish the wooden furniture.
In Malaysia, however, acid-curing lacquers have a predominant lead over other
types of coating materials, accounting for almost 75% of the market share (Anonymous, 2008). The acid-curing lacquers are based on alkyd and amino resins with a high
amount of organic solvents. The amino resins are urea-formaldehyde or melamine-formaldehyde
resins and the curing is initiated by an acid, usually p-toluene sulphonic acid,
which eventually releases some amount of the organic solvents and free formaldehyde
to the environment. Hence, during surface coating with acid-curing lacquers,
the workers in the furniture factories can potentially be exposed contemporarily
to both organic solvents and formaldehyde. Although, the occupational health
and safety Use and Standard of Exposure of Chemicals Hazardous to Health (USECHH)
regulations 2000 in Malaysia, stipulates the use and standard exposure of chemicals
hazardous to health, its effectiveness within the wooden furniture industry
in Malaysia remains unknown (Anonymous, 2008). Further, with continuous improvements
in coating materials which is likely to affect both exposure pattern and exposure
levels, it is important to establish the current industrial exposure levels
for chemical solvents from the acid-curing lacquers used.
Therefore, a study was conducted to determine the noise and chemicals exposure level among workers in the Malaysian wooden furniture manufacturing industry and evaluate the extent of hearing damage among the workers in the industry. The findings would possibly help identify measures that could mitigate noise and chemicals exposures faced by workers in the Malaysian wooden furniture industry.
MATERIALS AND METHODS
The study was carried out in 30 large-sized wooden furniture-manufacturing factories (i.e., larges factories are defined as those employing more than 100 workers, with an annual sales turnover in excess of US$ 10 million). The factories located throughout Peninsular Malaysia, were selected on the basis of their reportedly good health and safety records and also their voluntary consent to participate in the study. These factories were chosen from the membership listing of the Malaysian Furniture Industry Council. The study was carried out over a 5 months period, between May to September, 2009 and it was implemented in 4 distinct parts.
The first part of the study involved the evaluation of noise-level and noise-profile
in the sample factories. Noise-level measurements were made using a calibrated
portable sound level meter (UEI model DSM-101) as reported by Fairfax
(1996). The measurements were made by walking through the factories, while
continuously measuring the noise level using the portable sound level meter,
which was then analysed using the UEI acoustics software to depict the peak
noise levels and noise profile throughout the factory, as described by Kokkola
and Sorainen (2000).
The second part of the study involved the measurement of noise-level exposure of 1500 workers from the different machining sections, from the 30 furniture factories, using calibrated personal dosimeters, complying with BS6504 which, used the 90 dBA/8 h dose as the reference with a 3 dBA exchange rate. The workers, all of them from the rough milling and machining sections, were selected randomly after consultation with the respective factory management. The measurements provided an overall noise-level exposure experienced by these workers during their 8 h working shift.
The third part of the study quantified the possible noise-induced hearing problems among the workers, using audiometric tests on the same group of 1500 workers, which was carried out by two licensed audiologists, with the aid of audio-chambers and medical equipments capable of testing in the range of 500-8000 Hz in 500 Hz intervals. The measurements made provided an overall assessment of hearing problems due to noise among the workers in the wooden furniture manufacturing factories.
The fourth part of the study involved air sampling at the surface coating departments
of the 30 wooden furniture factories. All the factories were applying the coating
materials by spray equipment, which was also the most widely used method in
the Malaysian industry (Anonymous, 2008). The air sampling
was carried out over three subsequent days in the surface coating departments
of the factories on a total of 85 workers selected randomly from the surface
coating departments (including sprayers, handlers and general workers), with
a total of 500 parallel samples of solvents and formaldehyde collected over
an average sampling time of 30 min, throughout the 8 h shift of the workers.
The solvents were sampled using charcoal sampling tubers (SKC 226-01) supplied
by Dorset, UK, while, formaldehyde was sampled using silica sampling cartridges
supplied by Millipore Corp., USA. The sampling tubes were placed at the collar
of the workers close to the breathing zone, to ensure representative sampling
of exposure levels. After sampling, the tubes were stored at -20°C until
desorption and analysis. Industrial exposure to organic solvents most often
consists of exposure to a complex mixture of solvent vapours. When, two or more
solvents with similar toxicological effects are present, the combined exposure
rather than the individual exposures is determined, which is often referred
to as additive effect (Thorud et al., 2005).
The concentration of the additive effect of the various solvents and formaldehyde
in the sampling cartridges were determined by external standard calibration
using the 3 M organic vapour monitors and the GMD 570 formaldehyde diffusive
sampler, respectively, as described in the study by Thorud
et al. (2005) and Anonymous (2008). The data
were then handled by using the statistical package SPSS version 11.0 on a personal
computer, to extract and present the results accordingly.
The results of this study are presented in four parts.
Part I: Average noise levels in the Malaysian furniture industry: The
average noise-levels recorded in the Malaysian wooden furniture manufacturing
industry is shown in Table 1. It is apparent that the highest
noise-level of 130 dBA was recorded in the rough milling sections of the furniture
factories, while in the machining section, only the high-speed router recorded
noise-levels higher than the permissible 90 dBA. The rough milling section,
involving heavy-duty wood machining operations such as the moulding, ripping
and planning are regarded as machines emitting high levels of noise (Ratnasingam
and Scholz, 2007). The relatively large stock removal using large capacity
drive motors explain the high levels of noise experienced in the rough milling
section of the wooden furniture factories. On the other hand, the noise levels
in the machining section were lower due to lower stock removals during the machining
operations and also the use of drive motors of smaller capacities (Ratnasingam
and Scholz, 2008).
Part II: Noise level exposure of workers: The personal dosimeter results,
expressed as percentage of 90 dBA/8 h dose, are shown in Table
2. The results showed that 43% of the workers involved in the study were
exposed to higher dose than the permissible one, while the balance 57% were
exposed to a less dose, which is quite similar to the reports by Fairfax
(1996) and Kokkola and Sorainen (2000). The workers
in the rough milling sections of the
wooden furniture factories exposed to the higher noise levels than the permissible one, compared to their counterparts in the machining sections, clearly reflects the need for the provision of hearing protection to these workers.
Part III: Noise induced hearing problems among workers: The results of the audiometric tests from this study are expressed as Noise-Induced Permanent Threshold Shift (NIPTS). It is apparent that 25.8% of the workers in this study have a slight handicap with permanent threshold shift between 30 and 40 dB, while 8.9% of the workers have significant handicap with permanent threshold shift greater than 40 dB. The percentage of workers having no hearing handicap is 65.3% (Table 2). These results imply that the noise levels in the wooden furniture factories can significantly impair workers hearing and hence, the use of hearing protection and job-rotation among the workers must be strictly implemented, in order to ensure a hearing conservation program within the industry.
Part IV: Chemical solvents and formaldehyde exposures: A summation of
the chemical solvents and formaldehyde measurements is presented in Table
3. Since, the solvent exposure occurred as complex mixtures of several solvents,
the solvents exposures were calculated as additive effects, as described by
Thorud et al. (2005). The average of all chemical
solvents measurements was 1.43 ppm, while formaldehyde measurements averaged
1.93 ppm. The predominant chemical solvents detected in the vapours were ethanol
and ethyl acetate (Table 3) although, the proportions of the
various chemical solvents will vary according to the formulation of the coating
material (Thorud et al., 2005). The average measurements
for all solvents and formaldehyde found in this study exceeded the occupational
exposure limit, as stipulated in the existing Malaysian regulations for chemical
exposure. Although, during the surface coating operations the workers used personal
face mask, it proved to be insufficient to prevent exposure to the high levels
of solvents and formaldehyde, as the breakthrough of the chemical solvents increased
to 56% after 3 h of use, suggesting the need for the use of high quality air-purifying
masks with charcoal filters (Anonymous, 2008).
in wooden furniture manufacturing
represent average values of the 30 factories surveyed. WP: Wear protection,
HPDW: Have protection, but do not wear, DHP: Dont have protection
Induced Permanent Threshold Shift (NIPTS) among workers
based on the workers sample population of 1500
exposure in the wooden furniture industry
based on a sampling size of 500
The limited numbers of spot measurements at both inside and outside the masks
suggest that the suitability of such masks in minimizing chemical solvents exposure
is highly in doubt, as it has a reasonably high breakthrough rate after several
hours in use.
Although, this study is based on a limited number of wooden furniture factories,
it is tailored to be representative to assess noise and chemical solvents exposures
in the wooden furniture industry, which is predominated by the large manufacturers
(Ratnasingam and Scholz, 2008). Thus, this study provides
a useful evaluation of noise and chemical solvents exposures in the Malaysian
wooden furniture industry, which has not been previously reported (Anonymous,
2008). The results of the study provides evidence to support the fact that
noise-levels in the wooden furniture manufacturing industry, especially in the
rough-milling operations, is generally higher than the permissible limit. The
machines with high cutting rates, such as the moulder, surface planer and rip-saw,
explained the high noise-levels recorded (Ratnasingam and
Scholz, 2008). The high stock removal rates (often in excess of 1.0 mm)
using drive motors of large capacities to produce high cutter-block revolutions
results in high noise levels. Further, the labour intensive operations in the
rough milling section, explained the high percentage of the workers in the wooden
furniture factories exposed to high noise-levels. Inevitably, these workers
would experience a hearing handicap, as shown by the shift in the Noise-Induced
Permanent Threshold Shift (NIPTS). The study also demonstrates that very little
attention is currently given to protecting the hearing of the workers surveyed,
as only 33% of the workers who need hearing protection habitually, wear hearing
In terms of chemical solvents and formaldehyde exposure the results of the study revealed that the current exposure levels exceeds the occupational exposure limits stipulated in the national standard, suggesting that there is a need to enforce stricter the standards to ensure lower exposure levels (Anonymous, 2008). Further, the personal face masks provided to the workers is insufficient to protect them from chemical solvents and formaldehyde exposure, which may seriously affect their health and safety. In this context, masks with charcoal filter or masks with supplies of pressurised air is highly recommended for workers in the surface coating departments to minimize the exposure to chemical solvents and formaldehyde (Thorud et al., 2005).
Compared to their counterparts in Europe and Scandinavian countries, the study
revealed that workers in the Malaysian wooden furniture industry are exposed
to higher noise and chemical solvents levels than the permissible standards
(Vinzents and Laursens, 1993; Lazarus,
2003; Fernandez et al., 2009) and without
stricter enforcement of the existing occupational safety and health regulations
in Malaysia, this trend that compromises the workers safety and health is expected
to continue. The higher standard of safety and health among workers in the European
and Scandinavian countries could be attributed to the stricter enforcement of
the related laws (Ratnasingam and Scholz, 2008). Further,
the higher chemical solvents exposure in the Malaysian wooden furniture industry
as reflected in this study can also be attributed to the use of different grade
of coating materials, which is emits higher Volatile Organic Compounds (VOC),
while being of lower cost. The low cost phenomenon prevalent in the Malaysian
wooden furniture industry also explains the slow adoption of environmental friendly
manufacturing practices, which encourages the use of coating materials with
lower VOCs, as reported by Ratnasingam and Wagner (2009).
Industrial implications: This study shows that the present occupational
safety and health standards, with regards to noise and chemical solvents, are
breached in the wooden furniture manufacturing industry. Further, the implementation
and enforcement of these regulations within the industry has been relatively
weak and hence, the overall status of the workers health and safety is
compromised within the industry (Rampal and Nizam, 2006).
The low-cost economy so, prevalent within the Malaysian wooden furniture industry
also implies that workers welfare is often overlooked, while the focus is primarily
on cost competitiveness (Ratnasingam and Scholz, 2008).
Although, workers health and safety has a strong bearing on overall labour
productivity, the results from this study shows that efficient and environmental
friendly manufacturing practices is not widely practiced within the Malaysian
wooden furniture industry, as reported previously by Ratnasingam
and Wagner (2009). In essence, effective and efficient law enforcement is
vital in ensuring the compliance to the existing Occupational Safety and Health
(OSH) law in Malaysia. Nevertheless, all stakeholders also need to share this
responsibility, as the workers safety and health will significantly affect the
labour productivity, which in turn governs the overall business profitability
(Arezes and Miguel, 2008). Nevertheless, to re-examine
the reliability of the existing standards on noise and chemical solvents exposures
in the Malaysian wooden furniture industry to minimize workers safety and health
concerns, a more comprehensive and in-depth study of the industry may be necessary
to draw safe conclusions.
This study on the noise and chemical solvents exposured in the Malaysian wooden furniture industry reveals that the workers are exposed to levels higher than the Permissible Exposure Level (PEL). The high noise and chemical solvents exposure suggested that protective gadgets must be provided to all workers and its wearing must be made compulsory to minimize exposure. Nevertheless, the current protective gadgets do not provide the necessary protection to the workers hence, better quality safety protection gadgets is apparently needed for the workers within the wooden furniture industry. It is also apparent that the existing occupational safety and health regulations must be implemented and enforced strictly to ensure compliance within the wooden furniture manufacturing industry, which it turn will boost labour productivity, thereby enhancing competitiveness.
The authors wish to thank Dr. Stephen Laurent of Safety Engineering Inc., in Singapore for his assistance with the analysis of the air samples and also for extending the use of all noise and chemical solvents measurement equipments.