Abstract This study was set out to characterize size distributions of oil mists in three workplace atmospheres of the forming, threading, and heat treatment in a fastener manufacturing industry and to assess their exposures to workers。 Particle size segregating samplings were conducted on the workplace atmospheres of the three selected industrial processes by using the modified Marple 8-stage cascade impactor (m-Marple)。 We found that mass median aerodynamic diameter (MMAD) of the fine mode and coarse mode fell to the range 0。309–0。501 µm and 8。16–13。0 µm, respectively。 The fractions of inhaled particles exposed to different regions of the respiratory tracts found that the alveolar region was consistently higher than both head and tracheobronchial regions in all three studied exposure groups。 Personal inhalable oil mist samplings were conducted on workers in the three selected processes revealed their exposure levels as: threading workers (2。11 mg/m3) > forming workers (1。58 mg/m3) > heat treatment workers (0。0801 mg/m3)。 The estimated respirable exposure concentrations for both forming and threading workers (1。34 mg/m3 and 1。40 mg/m3, respectively) were higher than the level known for “increased risk of pulmonary injury” (0。20 mg/m3) suggesting that appropriate control measures should be taken to reduce their exposures to the oil mists of the respirable fraction immediately。83825

Keywords: Fastener manufacturing industry; Oil mist; Particle size distribution; Exposure assessment; Workplace atmosphere

1。Introduction

Based on the Taiwan governmental statistics in 2002, there were ∼1270 fastener manufacturers and in totalemployed with ∼37,000 employees in the whole country。 The total fas- tener production rates increased from ∼451,000 tons/year in 1991 to ∼1,269,000 tons/year in 2003 accounting for ∼14% world production。 The manufacture of fasteners involves seven

important industrial processes, including the wire drawing, forming, threading, cleaning, heat treatment, surface treatment,

∗ Corresponding author at: Department of Environmental and Occupational Health, Medical College, National Cheng Kung University, 138 Sheng-Li Road, Tainan 70428, Taiwan。 Tel。: +886 6 2353535x5806; fax: +886 6 2752484。

E-mail address: pjtsai@mail。ncku。edu。tw (P。-J。 Tsai)。

and packaging and shipping。 Among them mineral oil-based metalworking fluids (MWFs) are used in forming, threading, heat treatment processes for cooling, lubricating, and corrosion inhibition purposes and hence might result in the emission of oil mist to the workplace atmosphere and lead to the exposures of workers [1,2]。

Currently, an 8 h time-weighted-average permissible expo- sure limit of 5 mg/m3 for oil mist (mineral) is widely adopted by many agencies in the world, including US Occupational Safety and Health Administration (OSHA), US National Insti- tute of Occupational Safety and Health (NIOSH), UK Health and Safety Executive (HSE), American Conference of Govern- mental Industrial Hygienists (ACGIH), and Taiwan government, with the exception of Japan Occupational Health Association (JOSH) with a lower permissible exposure limit (=3 mg/m3)。

0304-3894/$ – see front matter © 2006 Elsevier B。V。 All rights reserved。 doi:10。1016/j。jhazmat。2006。12。036

Here, it should be noted that the above limit values are simply designated for regulating workers’ “total” oil mist exposures。 To date, it is well known that the so-called “total” aerosols can neither reflect all aerosols existing in the workplace atmosphere (i。e。, true total aerosols), nor the fractions of aerosols inhaled by workers [3]。

Epidemiological and animal studies have indicated that oil mist exposures might result in the laryngeal cancer [4], asthma [5], bronchial hyper-responsiveness [6], lipoid pneumonia [7], lung cancer [8], and many other respiratory illnesses [9,10]。 These suggest that oil mist exposures to different regions of the respiratory tract might lead to different health effects [11]。 These also imply that, to meet a comprehensive exposure assess- ment purpose, we need to measure not only for those oil mists inhaled into the respiratory tract, but also, to estimate their exposure to different regions of the respiratory tract。 In 1997, NIOSH proposed an 8 h-time-weighted-average exposure level of 0。4 mg/m3 for an oil mist exposure to the thoracic region [12]。 Kennedy et al。 found the occurrence of significant cross-shift decrements in FEV1 while workers were exposed to oil mists with aerodynamic diameter less than 9。8 µm with exposure lev- els greater than 0。20 mg/m3 [13]。 The above information further confirms the importance to measure particle size distributions of oil mists in order to assess their exposures to different regions of the respiratory tract。