Assessment of Welders Exposure to Carcinogen Metals from Manual Metal Arc Welding in Gas Transmission Pipelines, Iran

Article excerpt

Abstract

Background: Welding can produce dangerous fumes containing various metals especially carcinogenic ones. Occupational exposure to welding fumes is associated with lung cancer. Therefore, welders in Gas Transmission Pipelines are known as a high-risk group. This study was designed to determinate the amounts of metals Cr, Ni, and Cd in breathing zone and urine of welders and to assess the possibility of introducing urinary metals as a biomarker due to occupational exposure.

Methods: In this cross sectional study, 94 individuals from Gas Transmission Pipelines welders, Iran, Borujen in 2011 were selected and classified into 3 groups including Welders, Back Welders and Assistances. The sampling procedures were performed according to NIOSH 7300 for total chromium, nickel, and cadmium and NIOSH 7600 for Cr+6. For all participants urine samples were collected during the entire work shiftand metals in urine were determined according to NIOSH 8310.

Results: Back Welders and Assistances groups had maximum and minimum exposure to total fume and its elements, respectively. In addition, results showed that there are significant differences (P<0.05) between Welders and Back Welders with Assistances group in exposure with total fume and elements except Ni. Urinary concentrations of three metals including Cr, Cd and Ni among all welders were about 4.5, 12 and 14-fold greater than those detected in controls, respectively. Weak correlations were found between airborne and urinary metals concentrations (R2: Cr=0.45, Cd=0.298, Ni=0.362).

Conclusion: Urinary metals concentrations could not be considerate as a biomarker for welders' exposure assessment.

Keywords: Carcinogen metals, Gas transmission pipelines welders, Welding fume , Iran

Introduction

Natural gas is becoming one of the most widely used sources of energy in the world. Development of natural gas transmission network has crucial impact on the economy of gas-rich countries like Iran. The Natural Gas Industry Services include producing, moving, and selling gas. Moving gas is a very important process. It is divided into two classes: transmission and distribution. Transmission of gas means moving a large volume of gas at high pressures over long distances from a gas source to distribution centers (1, 2). Binding of the pipes is one of the most critical activities in the gas transmission, which is done with Manual Metal Arc Welding operation in Iran.

Electric Arc Welding is mostly used in several major industrial processes (3). It can produce dangerous fumes (a complex mixture of gases and oxides or salts of metals) that may be hazardous to the welder's health (4). The welding fume generated during the welding process possesses at least 13 metals, including manganese (mn), beryllium (Be), cadmium (Cd), chromium (Cr), cobalt (Co), copper (Cu), iron (Fe), lead (Pb), mercury (Hg), molybdenum (Mo), nickel (Ni), zinc (Zn), antimony (Sb), and vanadium (V) (5, 6).

Occupational exposure to welding fumes has been associated with an increased risk of lung cancer. According to the International Agency for Research on Cancer (IARC), Welding fumes are classified into group 2B (possibly carcinogenic to humans) (7). Nevertheless, nickel, cadmium, and chromium VI are three metals that were categorized as Class 1 IARC carcinogens in the early 1990s, based on sufficient evidence from experimental and epidemiological studies (8). These metals could interact directly with DNA and DNA replication, thus causing DNA damage (7, 9). In other mechanism, nickel and chromium species also stimulate cellular immune responses, while nickel and cadmium uptake can promote the release of active oxygen species (9).

Chronic exposure to soluble hexavalent chromium (Cr+6) result in bronchitis, asthma, ulceration and perforation of the nasal septum and liver and kidney damage in exposed workers (10). In addition, chromium (VI) compounds are Mutagenic in both prokaryotic and eukaryotic cells in vitro. …