Benzene exposure has serious health effects. The American Petroleum Institute (API) stated in 1948 that "it is generally considered that the only absolutely safe concentration for benzene is zero." The US Department of Health and Human Services (DHHS) classifies benzene as a human carcinogen. Long-term exposure to excessive levels of benzene in the air causes leukemia, a potentially fatal cancer of the blood-forming organs, in susceptible individuals. In particular, Acute myeloid leukemia or acute non-lymphocytic leukaemia (AML & ANLL) is not disputed to be caused by benzene. IARC rated benzene as "known to be carcinogenic to humans" (Group 1).
Outdoor air may contain low levels of benzene from tobacco smoke, wood smoke, automobile service stations, the transfer of gasoline, exhaust from motor vehicles, and industrial emissions. About 50% of the entire nationwide (United States) exposure to benzene results from smoking tobacco or from exposure to tobacco smoke.
Vapors from products that contain benzene, such as glues, paints, furniture wax, and detergents, can also be a source of exposure, although many of these have been modified or reformulated since the late 1970s to eliminate or reduce the benzene content. Air around hazardous waste sites or gas stations may contain higher levels of benzene. Because petroleum hydrocarbon products are complex mixtures of chemicals, risk assessments for these products generally focus on specific toxic constituents. The petroleum constituents of primary interest to human health have been the aromatic hydrocarbons (i.e., benzene, ethylbenzene, toluene, and xylenes). OSHA requires that a mixture "shall be assumed to present a carcinogenic hazard if it contains a component in concentrations of 0.1% or greater, which is considered to be a carcinogen.
The short term breathing of high levels of benzene can result in death, while low levels can cause drowsiness, dizziness, rapid heart rate, headaches, tremors, confusion, and unconsciousness. Eating or drinking foods containing high levels of benzene can cause vomiting, irritation of the stomach, dizziness, sleepiness, convulsions, and death.
The major effects of benzene are manifested via chronic (long-term) exposure through the blood. Benzene damages the bone marrow and can cause a decrease in red blood cells, leading to anemia. It can also cause excessive bleeding and depress the immune system, increasing the chance of infection. Benzene causes leukemia and is associated with other blood cancers and pre-cancers of the blood.
Human exposure to benzene is a global health problem. Benzene targets liver, kidney, lung, heart and the brain and can cause DNA strand breaks, chromosomal damage etc. Benzene causes cancer in both animals and humans. Benzene was first reported to induce cancer in humans in the 1920s. The chemical industry claims it wasn't until 1979 that the cancer-inducing properties were determined "conclusively" in humans, despite many references to this fact in the medical literature. Industry exploited this "discrepancy" and tried to discredit animal studies which showed benzene caused cancer, saying that they weren't relevant to humans. Benzene has been shown to cause cancer in both sexes of multiple species of laboratory animals exposed via various routes.
Some women who breathed high levels of benzene for many months had irregular menstrual periods and a decrease in the size of their ovaries. It is not known whether benzene exposure affects the developing fetus in pregnant women or fertility in men.
Animal studies have shown low birth weights, delayed bone formation, and bone marrow damage when pregnant animals breathed benzene.
Benzene has been connected to a rare form of kidney cancer in two separate studies, one involving tank truck drivers, and the other involving seamen on tanker vessels, both carrying benzene-laden chemicals.
Exposure to benzene
Workers in various industries that make or use benzene may be at risk for being exposed to high levels of this carcinogenic chemical. Industries that involve the use of benzene include the rubber industry, oil refineries, coke and chemical plants, shoe manufacturers, and gasoline-related industries. Downstream petroleum industry operations include the following categories: refinery, pipeline, marine, rail, bulk terminals and trucks, service stations, underground storage tanks, tank cleaning, and site characterization and remediation.
In 1987, OSHA estimated that about 237,000 workers in the United States were potentially exposed to benzene, but it is not known if this number has substantially changed since then.
Water and soil contamination are important pathways of concern for transmission of benzene contact. In the US alone there are approximately 100,000 different sites which have benzene soil or groundwater contamination. In 2005, the water supply to the city of Harbin in China with a population of almost nine million people, was cut off because of a major benzene exposure. Benzene leaked into the Songhua River, which supplies drinking water to the city, after an explosion at a China National Petroleum Corporation (CNPC) factory in the city of Jilin on 13 November.
In March 2006, the official Food Standards Agency in Britain conducted a survey of 150 brands of soft drinks. It found that four contained benzene levels above World Health Organization limits. The affected batches were removed from sale. (See also benzene in soft drinks).
Benzene exposure limits
The United States Environmental Protection Agency has set a maximum contaminant level (MCL) for benzene in drinking water at 0.005 mg/L (5 ppb), as promulgated via the National Primary Drinking Water Regulations. This regulation is based on preventing benzene leukemogenesis. The maximum contaminant level goal (MCLG), a nonenforceable health goal that would allow an adequate margin of safety for the prevention of adverse effects, is zero benzene concentration in drinking water. The EPA requires that spills or accidental releases into the environment of 10 pounds (4.5 kg) or more of benzene be reported to the EPA.
The US Occupational Safety and Health Administration (OSHA) has set a permissible exposure limit of 1 part of benzene per million parts of air (1 ppm) in the workplace during an 8-hour workday, 40-hour workweek. The short term exposure limit for airborne benzene is 5 ppm for 15 minutes. These legal limits were based on studies demonstrating compelling evidence of health risk to workers exposed to benzene. The risk from exposure to 1 ppm for a working lifetime has been estimated as 5 excess leukemia deaths per 1,000 employees exposed. (This estimate assumes no threshold for benzene's carcinogenic effects.) OSHA has also established an action level of 0.5 ppm to encourage even lower exposures in the workplace.
The National Institute for Occupational Safety and Health (NIOSH) revised the Immediately Dangerous to Life or Health (IDLH) concentration for benzene to 500 ppm. The current NIOSH definition for an IDLH condition, as given in the NIOSH Respirator Selection Logic, is one that poses a threat of exposure to airborne contaminants when that exposure is likely to cause death or immediate or delayed permanent adverse health effects or prevent escape from such an environment [NIOSH 2004]. The purpose of establishing an IDLH value is (1) to ensure that the worker can escape from a given contaminated environment in the event of failure of the respiratory protection equipment and (2) is considered a maximum level above which only a highly reliable breathing apparatus providing maximum worker protection is permitted [NIOSH 2004]. In September 1995, NIOSH issued a new policy for developing recommended exposure limits (RELs) for substances, including carcinogens. Because benzene can cause cancer, NIOSH recommends that all workers wear special breathing equipment when they are likely to be exposed to benzene at levels exceeding the REL (10-hour) of 0.1 ppm. The NIOSH STEL (95 min) is 1 ppm.
American Conference of Governmental Industrial Hygienists (ACGIH) adopted Threshold Limit Values (TLVs) for benzene at 0.5 ppm TWA and 2.5 ppm STEL.
Under New Jersey's Right-to-Know law, respiratory protection for benzene is discussed. As stated, improper use of respirators is dangerous. Respirators should only be used when there is a written respiratory program in place as described in the OSHA Respiratory Protection Standard (29 CFR 1910.134).[45] The employer is to develop and implement a written respiratory protection program with required worksite-specific procedures and elements for required respirator use. This program must be administered by a suitably trained program administrator. Employers must use the assigned protection factors (APF) listed in Table 1 of 29 CFR 1910.134 to select a respirator that meets or exceeds the required level of employee protection. Applicable to benzene:
If there is a potential for exposure to 0.1 ppm, a NIOSH-approved half face respirator must be worn with an organic vapor cartridge (APF 10).
If there is a potential for exposure to 0.5 ppm, a NIOSH-approved full face respirator must be worn with an organic vapor cartridge (APF 50).
Where the potential exists for exposure to over 5 ppm, a NIOSH-approved air-supplied respirator with a full facepiece operated under pressure-demand or other positive-pressure mode must be used (APF 1,000).
[edit] Exposure monitoring
Airborne exposure monitoring for benzene must be conducted in order to properly assess personal exposures and effectiveness of engineering controls. Initial exposure monitoring should be conducted by an industrial hygienist or person specifically trained and experienced in sampling techniques. Contact an AIHA Accredited Laboratory for advice on sampling methods.
Each employer who has a place of employment where occupational exposures to benzene occur shall monitor each of these workplaces and work operations to determine accurately the airborne concentrations of benzene to which employees may be exposed. Representative 8-hour TWA employee exposures need to be determined on the basis of one sample or samples representing the full shift exposure for each job classification in each work area. Unless air samples are taken frequently, the employer does not know the concentration and would not know how much of a protection factor is needed.
In providing consultation on work safety during oil clean-up operations following the Deepwater Horizon accident, OSHA has worked with an number of other government agencies to protect Gulf cleanup workers. OSHA partnered with the NIOSH to issue "Interim Guidance for Protecting Deepwater Horizon Response Workers and Volunteers" and recommend measures that should be taken to protect workers from a variety of different health hazards that these workers face.[49] OSHA conceded that it recognizes that most of its PELs are outdated and inadequate measures of worker safety. In characterizing worker exposure OSHA instead relies on more up-to-date recommended protective limits set by organizations such as NIOSH, the ACGIH, and the American Industrial Hygiene Association (AIHA), and not on the older, less protective PELS. Results of air monitoring are compared to the lowest known Occupational Exposure Limit for the listed contaminant for purposes of risk assessment and protective equipment recommendations.
Biomarkers of exposure
Several tests can determine exposure to benzene. Benzene itself can be measured in breath, blood or urine, but such testing is usually limited to the first 24 hours post-exposure due to the relatively rapid removal of the chemical by exhalation or biotransformation. Most persons in developed countries have measureable baseline levels of benzene and other aromatic petroleum hydrocarbons in their blood. In the body, benzene is enzymatically converted to a series of oxidation products including muconic acid, phenylmercapturic acid, phenol, catechol, hydroquinone and 1,2,4-trihydroxybenzene. Most of these metabolites have some value as biomarkers of human exposure, since they accumulate in the urine in proportion to the extent and duration of exposure, and they may still be present for some days after exposure has ceased. The current ACGIH biological exposure limits for occupational exposure are 500 μg/g creatinine for muconic acid and 25 μg/g creatinine for phenylmercapturic acid in an end-of-shift urine specimen.
Molecular toxicology
The paradigm of toxicological assessment of benzene is slowly shifting towards the domain of molecular toxicology as it allows understanding of fundamental biological mechanisms in a better way. Glutathione seems to play an important role by protecting against benzene induced DNA breaks and it is being identified as a new biomarker for exposure and effect.[55] Benzene causes chromosomal aberrations in the peripheral blood leukocytes and bone marrow explaining the higher incidence of leukemia and multiple myeloma caused by chronic exposure. These aberrations can be monitored using fluorescent in situ hybridization (FISH) with DNA probes to assess the effects of benzene along with the hematological tests as markers of hematotoxicity.[56] Benzene metabolism involves enzymes coded for by polymorphic genes. Studies have shown that genotype at these loci may influence susceptibility to the toxic effects of benzene exposure. Individuals carrying variant of NAD(P)H:quinone oxidoreductase 1 (NQO1), microsomal epoxide hydrolase (EPHX) and deletion of the glutathione S-transferase T1 (GSTT1) showed a greater frequency of DNA single-stranded breaks.
Summary
According to the Agency for Toxic Substances and Disease Registry (ATSDR) (2007), benzene is both an anthropogenically produced and naturally occurring chemical from processes that include: volcanic eruptions, wild fires, synthesis of chemicals such as phenol, production of synthetic fibers and fabrication of rubbers, lubricants, pesticides, medications, and dyes. The major sources of benzene exposure are tobacco smoke, automobile service stations, exhaust from motor vehicles, and industrial emissions; however, ingestion and dermal absorption of benzene can also occur through contact with contaminated water. Benzene is hepatically metabolized and excreted in the urine. Measurement of air and water levels of benzene is accomplished through collection via activated charcoal tubes, which are then analyzed with a gas chromatograph. The measurement of benzene in humans can be accomplished via urine, blood, and breath tests; however, all of these have their limitations because benzene is rapidly metabolized in the human body into by-products called metabolites.
OSHA regulates levels of benzene in the workplace. The maximum allowable amount of benzene in workroom air during an 8-hour workday, 40-hour workweek is 1 ppm. Because benzene can cause cancer, NIOSH recommends that all workers wear special breathing equipment when they are likely to be exposed to benzene at levels exceeding the recommended (8-hour) exposure limit of 0.1 ppm.
Biological oxidation and carcinogenic activity
One way of understanding the carcinogenic effects of benzene is by examining the products of biological oxidation. Pure benzene, for example, oxidizes in the body to produce an epoxide, benzene oxide, which is not excreted readily and can interact with DNA to produce harmful mutations.
Safety Description
EC Safety phrases are extensively used in the world, in data sheets of chemicals. The codes
have the following meanings:
S1 Keep locked up.
S2 Keep out of the reach of children.
S3 Keep in a cool place.
S4 Keep away from living quarters.
S5 Keep contents under ... (there follows the name of a liquid).
S6 Keep under ... (there follows the name of an inert gas).
S7 Keep container tightly closed.
S8 Keep container dry.
S9 Keep container in a well-ventilated place.
S12 Do not keep the container sealed.
S13 Keep away from food, drink and animal foodstuffs.
S14 Keep away from ... (a list of incompatible materials will follow).
S15 Keep away from heat.
S16 Keep away from sources of ignition.
S17 Keep away from combustible material.
S18 Handle and open container with care.
S20 When using, do not eat or drink.
S21 When using do not smoke.
S22 Do not breathe dust.
S23 Do not breathe vapour.
S24 Avoid contact with skin.
S25 Avoid contact with eyes.
S26 In case of contact with eyes, rinse immediately with plenty of water and seek medical
advice.
S27 Take off immediately all contaminated clothing.
S28 After contact with skin, wash immediately with plenty of soap-suds.
S29 Do not empty into drains.
S30 Never add water to this product.
S33 Take precautionary measures against static discharges.
S35 This material and its container must be disposed of in a safe way.
S36 Wear suitable protective clothing.
S37 Wear suitable gloves.
S38 In case of insufficient ventilation, wear suitable respiratory equipment.
S39 Wear eye / face protection.
S40 To clean the floor and all objects contaminated by this material, use .... (there follows
suitable cleaning material).
S41 In case of fire and / or explosion do not breathe fumes.
S42 During fumigation / spraying wear suitable respiratory equipment.
Safety Description
S43 In case of fire use ... (there follows the type of fire-fighting equipment to be used.)
S45 In case of accident or if you feel unwell, seek medical advice immediately (show the
label whenever possible.)
S46 If swallowed, seek medical advice immediately and show this container or label.
S47 Keep at temperature not exceeding...
S48 To be kept wet with (there follows a material name).
S49 Keep only in the original container.
S50 Do not mix with ...
S51 Use only in well ventilated areas.
S52 Not recommended for interior use on large surface areas.
S53 Avoid exposure - obtain special instructions before use.
S56 Dispose of this material and its container at hazardous or special waste collection point.
S57 Use appropriate container to avoid environmental contamination.
S59 Refer to manufacturer / supplier for information on recovery / recycling.
S60 This material and its container must be disposed of as hazardous waste.
S61 Avoid release to the environment. Refer to special instructions / safety data sheets.
S62 If swallowed, do not induce vomitting; seek medical advice immediately and show this
container or label.
S1/2 : Keep locked up and out of the reach of children.
S24/25 : Avoid contact with skin and eyes.
S36/37 : Wear suitable protective clothing and gloves.
S36/37/39 : Wear suitable protective clothing, gloves and eye/face protection.
S37/39 : Wear suitable gloves and eye/face protection.
Risk Codes
Chemical data sheets available in many countries now contain codes for certain "risk phrases",
shown as R23, R45 etc. These risk phrase codes have the following meanings:
R1 Explosive when dry.
R2 Risk of explosion by shock, friction, fire or other source of ignition.
R3 Extreme risk of explosion by shock, friction, fire or other sources of ignition.
R4 Forms very sensitive explosive metallic compounds.
R5 Heating may cause an explosion.
R6 Explosive with or without contact with air.
R7 May cause fire.
R8 Contact with combustible material may cause fire.
R9 Explosive when mixed with combustible material.
R10 Flammable.
R11 Highly flammable.
R12 Extremely flammable.
R13 Extremely flammable liquefied gas
R14 Reacts violently with water.
R15 Contact with water liberates extremely flammable gases.
R16 Explosive when mixed with oxidizing substances.
R17 Spontaneously flammable in air.
R18 In use, may form inflammable/explosive vapour-air mixture.
R19 May form explosive peroxides.
R20 Harmful by inhalation.
R21 Harmful in contact with skin.
R22 Harmful if swallowed.
R23 Toxic by inhalation.
R24 Toxic in contact with skin.
R25 Toxic if swallowed.
R26 Very toxic by inhalation.
R27 Very toxic in contact with skin.
R28 Very toxic if swallowed.
R29 Contact with water liberates toxic gas.
R30 Can become highly flammable in use.
R31 Contact with acids liberates toxic gas.
R32 Contact with acid liberates very toxic gas.
R33 Danger of cumulative effects.
R34 Causes burns.
R35 Causes severe burns.
R36 Irritating to eyes.
R37 Irritating to respiratory system.
R38 Irritating to skin.
Risk Codes
R39 Danger of very serious irreversible effects.
R40 Limited evidence of a carcinogenic effect.
R41 Risk of serious damage to the eyes.
R42 May cause sensitization by inhalation.
R43 May cause sensitization by skin contact.
R44 Risk of explosion if heated under confinement.
R45 May cause cancer.
R46 May cause heritable genetic damage.
R47 May cause birth defects
R48 Danger of serious damage to health by prolonged exposure.
R49 May cause cancer by inhalation.
R50 Very toxic to aquatic organisms.
R51 Toxic to aquatic organisms.
R52 Harmful to aquatic organisms.
R53 May cause long-term adverse effects in the aquatic environment.
R54 Toxic to flora.
R55 Toxic to fauna.
R56 Toxic to soil organisms.
R57 Toxic to bees.
R58 May cause long-term adverse effects in the environment.
R59 Dangerous to the ozone layer.
R60 May impair fertility.
R61 May cause harm to the unborn child.
R62 Risk of impaired fertility.
R63 Possible risk of harm to the unborn child.
R64 May cause harm to breastfed babies.
R65 Harmful: may cause lung damage if swallowed.
R66 Repeated exposure may cause skin dryness or cracking.
R67 Vapours may cause drowsiness and dizziness.
R68 Possible risk of irreversible effects.
R20/21 : Harmful by inhalation and in contact with skin.
R20/21/22 : Harmful by inhalation, in contact with skin and if swallowed.
R20/22 : Harmful by inhalation and if swallowed.
R21/22 : Harmful in contact with skin and if swallowed.
R23/24/25 : Toxic by inhalation, in contact with skin and if swallowed.
R23/25 : Toxic by inhalation and if swallowed.
R26/27/28 : Very toxic by inhalation, in contact with skin and if swallowed.
R26/28 : Very toxic by inhalation and if swallowed.
R36/37 : Irritating to eyes and respiratory system.
R36/37/38 : Irritating to eyes, respiratory system and skin.
Risk Codes
R36/38 : Irritating to eyes and skin.
R37/38 : Irritating to respiratory system and skin.
R42/43 : May cause sensitization by inhalation and skin contact.
R48/22 : Harmful: danger of serious damage to health by prolonged exposure if swallowed.
R50/53 : Very toxic to aquatic organisms, may cause long-term adverse effects in the
aquatic environment.
R51/53 : Toxic to aquatic organisms, may cause long-term adverse effects in the aquatic
environment.
R52/53 : Harmful to aquatic organisms, may cause long-term adverse effects in the aquatic
environment.
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