1. INTRODUCTIONBenzene (also known as benzol) is a colorless, highly flammable liquid with a sweet odor. It evaporates very quickly in the air and partly dissolves in water. Most people can begin to smell benzene in the air at around 60 ppm air and recognize it as benzene at 100 ppm. It was first discovered and extracted for coal tar in the 1980s, and then for oil due to its surge in demand. Since then, various industries have used benzene to make other chemicals, such as styrene, cumene and cyclohexane. Benzene is also an important ingredient in the manufacture of certain types of rubbers, lubricants, dyes, detergents, medicines and pesticides. Therefore, people employed in these industries may be exposed to benzene in the air at levels well above the levels normally encountered by the general population. [1]Concerns about potential health effects resulting from benzene exposure, such as bone marrow depression leading to anemia, leukopenia, and thrombocytopenia, as well as a decrease in circulating blood cells, have been reported. Additionally, laboratory studies in humans and animals have indicated that benzene exerts its effect by damaging the genetic material of cells. Benzene is therefore classified as a confirmed human carcinogen. [2] In Singapore, every employer has the responsibility to take reasonably practicable measures to ensure that no one at work is exposed to benzene above the permissible exposure level (PEL) specified in the regulations. The prescribed permissible exposure limit (long term) for benzene is 1 ppm over an 8-hour workday and 40-hour workweek. [3] These exposure standards are generally established based on a risk assessment using data obtained from human and/or animal health effects studies. [4]Thus, this...... middle of article...... [8] Animal and human studies provide clear evidence of a causal relationship between occupational exposure to benzene that leads to aplastic anemia.Lan et al. [7] reported that bone marrow toxicity was detected in a group of workers after several months of exposure to benzene present in the air at a concentration equal to or less than 1 ppm. Therefore, the local PEL setting should be modified to the ACGIH-recommended TLV-TWA of 0.5 ppm to minimize the potential for adverse health effects posed by occupational exposure. Alternatively, the entire world should adopt a single, internationally agreed system such as the Globally Harmonized System (GHS). ) under the auspices of the United Nations. GHS allows the country to adopt a single, unilateral system, reduce duplicate testing and evaluation of chemicals, facilitate trade in chemicals where hazards can be properly assessed and identified on an international basis.. [15]