For a naturally occurring compound used in many products, Benzene can be a threat to the environment and to health.
Benzene is an aromatic hydrocarbon produced by burning natural products. It is a component of products derived from coal and petroleum, found in gasoline and other fuels. Benzene is used to manufacture plastics, detergents, pesticides, and other chemicals such as ethyl benzene, cyclohexane, nitrobenzene, chlorobenzenes and maleic anhydride.
The bad news: benzene is a known leukemia-causing carcinogen and people who work with or are exposed to benzene over a long period of time have a high risk of developing benzene-related illnesses, ranging from anemia to cancer. Research has shown that individuals have developed, and died from, leukemia when exposed to benzene for periods varying from five years to thirty years. Long-term (chronic) exposure can affect bone marrow and blood production.
Unfortunately, the odor of benzene does not provide adequate warning of its hazard and many blood disorders related to benzene exposure can occur without symptoms. Short-term exposure to high levels of benzene can cause drowsiness, dizziness, unconsciousness, and even death.
For these reasons, governments around the world mandate maximum allowable industrial exposure levels of benzene. The most common short-term exposure limit is 5 ppm (16 mg/m3 ) for any 15 minute period, developed by the US Occupational Safety and Health Administration (OSHA) as a Permissible Exposure Limit (PEL).
OSHA also specifies that “the employer shall assure that no employee is exposed to an airborne concentration of 1 ppm benzene in air as an 8-hour time-weighted average.” They also use “Action Levels” to indicate the level of a harmful or toxic substance which requires medical surveillance, increased industrial hygiene monitoring, or biological monitoring. The Action Level for benzene is just 0.5 ppm as an 8-hour time-weighted average (TWA). The US National Institute for Occupational Safety and Health (NIOSH) has even lower recommended exposure limits (RELs) of just 1 ppm over a 15-minute period and 0.1 ppm over 8 hours.
Employers have an obligation to select a monitoring method which meets the accuracy and precision requirements of the prevailing standard taking into account the unique local field conditions. The OSHA standard, for example, requires that the method of monitoring must have an accuracy, to a 95% confidence level, of not less than ±25% for concentrations of benzene greater than or equal to 0.5 ppm.
An effective way to monitor air is to use online mass spectrometry, which provides fast, multi-component gas analysis. One mass spectrometer (MS) can provide total plant coverage, monitoring a single sample point for benzene, toluene, ethyl benzene and xylenes (BTEX) in just 12 seconds, including stream settling time. Therefore, 60 sample points can be monitored in just 12 minutes, assuming all points are assigned equal priority. If some sample points are more important than others (because of a higher level of personnel activity or a higher risk of leaks) these can be assigned higher levels of priority, ensuring they are monitored more frequently.
It has been shown that mass spectrometers can provide broad coverage and rapid response when configured to monitor fugitive and point source emissions. An environmental mass spectrometer is engineered to help plants monitor fugitive emissions of toxic organic vapors, protecting workers and surrounding environment from hazardous exposure.
Experience has shown that the incidence of alarms tends to be high when the equipment is first installed but correction of accumulated leaks and improvements to standard operating procedures lead to a significant reduction in toxic emissions at the facility. The reliable nature of the technology and the flexible configuration options ensure that the cost of ownership remains low. The ability to measure benzene and other aromatics with ppb repeatability ensures that future environmental regulations for benzene will not compromise the installation.
For additional information, about mass spectrometers and their use in environmental monitoring of these hydrocarbons, read Continuous monitoring of benzene, toluene, ethyl benzene, and xylenes (BTEX) in air with the Thermo Scientific Sentinel PRO Environmental Mass Spectrometer
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