رئوس مطالب

  • چکیده
  • کلیدواژه ها
  • مقدمه
  • مواد و روش ها
  • وسایل اندازه گیری ازون
  • اندازه گیری ROS
  • تجزیه و تحلیل آماری
  • نتایج
  • بحث
  • سطوح O3
  • سطوح ROS و ذرات
  • سطوح ROS و O3
  • مفاهیم

Abstract

Many toxic substances including heavy metals, ozone, carbon monoxide, carbon dioxide, and nitrogen oxides are generated during welding. Ozone (O3) is a strong oxidant that generates reactive oxygen species (ROS) in tissue, and ambient ROS exposure associated with particles has been determined to cause DNA damage. Ozone is produced within 30 seconds during welding. However, the length of time that O3 remains in the air after welding is completed (post-welding) is unknown. The current study aimed to assess the distributions of ambient ROS and O3 before the start of welding (pre-welding), during welding, and after welding. The highest O3 levels, equal to 195 parts per billion (ppb), appeared during welding. Ozone levels gradually decreased to 60 ppb 10 minutes after the welding was completed. The highest ROS level was found in samples taken during welding, followed by samples taken after the welding was completed. The lowest ROS level was found in samples taken before the welding had started. Ozone and ROS levels were poorly correlated, but a similar trend was found for O3 and ROS levels in particles (μM/mg). Although particles were not generated after welding, ROS and O3 still persisted for more than 10 minutes. Meanwhile, because O3 continues after welding, how long the occupational protective system should be used depends on the welding materials and the methods used. In addition, the relationship between metal fumes and ROS generation during the welding process should be further investigated.

Keywords: - - - -

Results

Distribution of O3 Levels Before, During, and After Welding

The pre-welding O3 levels were equal to 20 parts per billion (ppb). They rose to a maximum level of 195 ppb (range, 20–195 ppb) 5 minutes after the welding started, (Fig. 1)., then decreased gradually to 80 ppb 3 minutes after welding, and finally fell to 50 ppb 10 minutes after welding. The average O3 levels were 20.9 ppb before welding, 155.1 ppb during welding, 65.8 ppb 10 minutes after welding, and 39.2 ppb 65 minutes after welding (Fig. 2). The O3 levels during and after welding were significantly higher than the pre-welding levels (P < 0.05).

Distribution of Particle Levels Before, During, and After Welding

The particle levels in the samples taken during welding were significantly higher (p < 0.05; average, 8,097 lg/m3) than the pre-welding (405.8 lg/m3) and post-welding (289.3 lg/m3) levels (Fig. 3). The pre- and post-welding levels were not significantly different.

Distribution of ROS Levels Before, During, and After Welding

The highest ROS levels were found in the samples taken during welding (average, 5.19 lM/m3). The second highest levels were found after welding (average, 1.43 lM/m3), and the lowest levels were found before welding (average, 0.58 lM/m3) (Fig. 4) The ROS levels during welding were significantly higher than the pre- and post-welding levels (p < 0.05).

Correlation of ROS and Particle Levels

A significant correlation between ROS and particle levels was found only for post-welding (r = 0.764; p = 0.016) (Table 1).

O3 and ROS Levels

The average O3 level increased when welding started, then decreased gradually until 10 minutes after welding. The trend was consistent when O3 levels were compared with ROS levels in particles (lM/mg). The ROS levels (lM/m3), however, were not correlated with the O3 levels (Fig. 5).

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