Precision machinery manufacturing industry in Taiwan continues to develop better and
finer precision manufacturing and processing techniques, but also constantly looking for new
materials to use, for higher precision and more efficient manufacturing. Precision machinery
manufacturing processes include metal components casting, manufacturing and machine
processing, during the operation may cause exposure to organic compounds, mineral dust and
oil mist. These new techniques and use of new materials may bring new hazards exposure risk
to workers. In order to reduce hazards exposure risk and protect workers, further investigation
of hazard exposure conditions and health risk assessment are needed.
This study completed a search and review related precision machinery manufacturing
hazards exposure literatures, and used questionnaires to investigate operation and raw
materials and hazardous materials used in precision machinery manufacturing industries. With
these data, we may have a better understanding to precision machinery manufacturing
industries’ status. And an environmental monitoring in work areas will be conducted, where
worker may expose to the possible hazards, such as organic compounds, mineral dust and oil
mist. The survey results, may help us to assess the health effects of workers exposed to
hazardous materials in precision machinery manufacturing industries.
The study performed air sampling in seven typical precision machinery manufacturers
in Taiwan. Overall, 216 area samplings and 131 personal samplings were completed in the
current study. The results showed that there are significant differences in VOCs concentration
levels among the seven manufacturers except for acetone. The highest total VOCs levels were
found in Plant F. The highest n-heptane levels were found in Plant E when compared with
other plants. In Plant A, the average concentrations of n-hexane and toluene were found to be
higher than those in other plants. The personal sampling results showed that concentrations of
n-hexane in Plant C, toluene in Plant D, and n-heptane in Plant F were higher than those in
other plants. Except for pentane and acetone, significant differences of other VOCs (organic
solvents) were found among the seven plants. The highest personal sampling total VOC levels
was found in Plant F and consistent with area sampling results. For 5 day continuous sampling
in Plant B, on the third day, the highest n-hexane concentration was found in the cleaning and
oil storage areas, whereas there was a descending trend of toluene concentration in the
sculpturing area. The highest concentration of n-heptane was found in the oil storage area. In
Plant D, the highest n-hexane level was found on the second day of the fabricating area, and
the highest level of toluene was found in the painting area. From the continuous sampling data,
there was no significant difference in VOCs levels during the weekdays. The total VOC
exposure concentration and 8 hours PEL-TWA ratios are below one; therefore, VOCs
exposure is within permissible limits.
The results can be used to check upon and verify chemical lists and for follow up
monitoring of VOCs exposure in the precision machinery manufacturing industry to prevent
hazardous level of VOC exposure in workers.
Seven factories (sampling done for a single day) and two factories (sampling done for
five continuous days) were studied. The concentrations of 2,5-HD did not exceed 5 mg/g
creatinine for ACGIH in all seven factories. The concentrations of methyl hippuric acid (MHA)
did not exceed 1.5 g/g creatinine for ACGIH. The maximum concentration of
benzylmercapturic acid was 33.7 μg/g creatinine at factory D before work started. The 2,5-
HD and the total MHA in urine samples of factory E had the highest concentration levels at
628.2 μg / g creatinine before work started and 124.77 mg/g creatinine after work ended.
In order to reduce the concentration level of organic compounds exposure in workers, it
is necessary to implement operational environmental control, local exhaust facilities,
occupational hygiene training and administration and provide suitable personal respiratory
protective equipment for workers.
The measurement results of environmental monitoring on workers exposure to oil mists
for 5 factories, indicated that worker personal time-weighted average exposures to oil mists
ranged from 0.02 to 0.48 mg/m3 with an overall mean of 0.21 mg/m3. Conversely, a level of
0.01 to 0.35 mg/m3, with an overall mean of 0.14 mg/m3, was found through monitoring
different areas. The oil mist to total particulate ratio on personal samples ranged from 0.08 to
0.89 mg/m3, averaging 0.53 mg/m3.
Additionally, a new analytical method for measuring “oil mist (from mineral oil-based
metalworking fluids)” was proposed based on the HSE MDHS 84 and NIOSH 5524 methods.
A few performance criteria were evaluated, including detecting only certain parts (including
limit of detection, the limit of quantitation, and analysis coefficient of variation) and sampling
only certain parts (including the oil extraction coefficient and sample stability). The results
fulfilled the requirements of the performance criteria and can serve as a reference method for
This study completed a survey of workers from seven precision machinery
manufacturing factories’ precision casting operations and their exposure to mineral dust.
Environmental monitoring (personal and area sampling) results showed, 77.2% (122 samples
out of 158 samples) of environmental monitoring samples’ respirable dust concentrations were
over 1/10 permissible exposure limits (PEL), 10.76% (17 samples out of 158 samples) of
environmental monitoring samples’ respirable dust concentrations were over PEL and 17.09%
(27 samples out of 158 samples) of environmental monitoring samples’ respirable dust
concentrations were over 1/2 PEL in these precision casting operations. Workers in dipping
and coating Processes, sintering, shell removal, sandblast and cutting areas had higher
respirable dust exposure concentrations. Dust in precision machinery manufacturing factories’
precision casting operations is very easy to spread, areas with higher respirable dust
concentrations should be separated from other working areas to prevent dust spreading. And
areas with higher respirable dust concentrations should have proper ventilation systems
personal protection equipment to lower dust exposure.
Finally, practices for controlling health hazards in precision machinery manufacturing
were proposed based on field surveys, environmental monitoring findings, and various
guidelines and can serve as reference for the precision machinery manufacturing and related
industries to prevent the occurrence of occupational diseases.
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