|
|
|
|
 |
|
Related Products and Services |
|
|
 |
2-Health Effects of Benzene
|
|
What are the main health hazards associated with breathing in benzene?
What happens when benzene comes into contact with my skin?
Can benzene hurt my eyes?
What happens if benzene is accidentally swallowed (enters the digestive system)?
What are the long term health effects of exposure to benzene?
Will benzene cause cancer?
Will benzene cause any problems with my reproductive system?
Will benzene cause effects on the fetus/unborn baby?
Will benzene act in a synergistic manner with other materials (will its effects be more than the sum of the effects from the exposure to each chemical alone)?
Is there potential for benzene to build-up or accumulate in my body?
What are the main health hazards associated with breathing in benzene? Short-term exposure causes depression of the central nervous system (CNS), marked by drowsiness, dizziness, headache, nausea, loss of coordination, confusion and unconsciousness. No effects are expected at 25 ppm. Exposure to 50 to 150 ppm produces headache, and tiredness. Nose and throat irritation have also been reported following short-term exposure. A period of feeling excited or giddy may precede the onset of other symptoms. Exposure to approximately 20,000 ppm for 5 to 10 minutes may result in death. In general, blood and immune system effects have not been documented in humans following short-term exposures, although these effects have been seen in animals. A 1992 report describes blood system effects in workers exposed to high levels of benzene (estimated to be above 60 ppm) for several days. The workers were also exposed to other chemicals at the same time. In addition to CNS symptoms experienced during the exposure, 9 of the 15 workers had at least 1 blood system abnormality when followed up 4 months later. One year later, 6 workers still had changes in the blood system (numerous large granular lymphocytes). What happens when benzene comes into contact with my skin? Animal evidence has shown that benzene is moderately irritating. Human studies have demonstrated that absorption of liquid benzene or its vapours occurs only to a small extent, but can contribute to overall exposure. There are no reports of skin sensitization. Can benzene hurt my eyes? The vapour can be irritating to the eyes. Animal evidence indicates that splashes of benzene in the eyes will be moderately irritating but will not cause permanent injury. What happens if benzene is accidentally swallowed (enters the digestive system)? Benzene is readily absorbed following ingestion producing CNS depression with symptoms as described under inhalation. There are no human reports of blood or immune system effects resulting from ingestion, although these effects have been observed in animal experiments. In one case report, accidental ingestion and/or attempted suicide with benzene produced pneumonitis (probably caused by aspiration of benzene into the lungs) as one of the symptoms. Based on this observation, the physical properties (viscosity and surface tension) and the fact that benzene is a petroleum distillate, benzene can probably be aspirated. Aspiration is the inhalation of a material into the lungs during ingestion or vomiting. Severe lung irritation, damage to the lung tissues and death may result. What are the long term health effects of exposure to benzene? SKIN : Prolonged or repeated contact causes redness, dryness, cracking (dermatitis) due to the defatting action of this solvent. BLOOD AND BLOOD-FORMING ORGANS: Although there are limitations to some of the numerous studies, it is conclusive that benzene causes a serious condition where the number of circulating red blood cells (erythrocytes), white blood cells (leukocytes) and clotting cells (thrombocytes) is reduced (pancytopenia). At this stage, effects are thought to be readily reversible. However, continued exposure can result in aplastic anemia or leukemia. Benzene also damages the bone marrow, where new blood cells are produced, resulting in aplastic anemia, which can lead to leukemia. Typical effects of benzene on the blood system were observed in one study where 217 workers were exposed to 30 to 210 ppm for 3 months to 17 years. Two studies have shown that low level exposures (less than 1.4 ppm) for long periods of time (up to 21 years) have not resulted in any blood effects. IMMUNE SYSTEM : Studies of workers have found changes in the immune system, which are at least partially related to the changes in the blood system discussed above. NERVOUS SYSTEM: Two limited studies (there was exposure to other chemicals and exposure levels were not well established) suggest that benzene may cause effects on the peripheral nerves and/or spinal cord. Symptoms included an increased incidence of headaches, fatigue, difficulty sleeping and memory loss among workers with significant exposures. Will benzene cause cancer? The International Agency for Research on Cancer (IARC) has concluded that there is sufficient evidence for carcinogenicity to humans. The overall IARC evaluation is Group 1 - carcinogenic to humans. The National Toxicology Program (NTP) has determined that benzene is a substance known to be carcinogenic. The American Conference of Governmental Industrial Hygienists (ACGIH) has designated benzene as a confirmed human carcinogen (A1). There are common limitations in the human studies because exposures usually cannot be accurately assessed, the numbers of cases is small and frequently there is exposure to other chemicals. However, there are so many case reports and epidemiologic studies of exposed workers, that a causal relationship between benzene exposure and leukemia has been clearly established. Benzene exposure has also been associated with cancer of the lymph system (lymphoma), lung cancer and bladder (urothelial) cancer. There is one study with low level exposures. The median levels of exposure between 1952 and 1978 were 0.14 ppm for refinery workers and 0.53 ppm for benzene-related units. There were no leukemia deaths in the group and there was no increase in any type of cancer, compared to a similar group or the general population of the United States. Will benzene cause any problems with my reproductive system? Although there are concerns that historical, high occupational exposures to benzene may be related to menstrual and reproductive problems in women, the available studies have too many limitations to draw any conclusions. Limited animal evidence suggests that benzene may affect reproductive organs at exposure levels which also cause significant toxicity. Will benzene cause effects on the fetus/unborn baby? Benzene crosses the placenta but there is no conclusive evidence that it affects the fetus. Most of the studies had limitations such as poor exposure assessment, exposure to other chemicals and a small number of cases. In a case study of one woman exposed to benzene during two pregnancies (at levels producing severe maternal toxicity), both children were healthy and did not have chromosomal alterations. In another study, 14 children of female workers exposed to benzene and other organic solvents did have chromosomal changes. There was no discussion of maternal toxicity nor birth defects. Animal evidence indicates that benzene is not teratogenic, but is fetotoxic at exposure levels which also resulted in mild maternal toxicity. Will benzene act in a synergistic manner with other materials (will its effects be more than the sum of the effects from the exposure to each chemical alone)? Studies with animals have shown that ethanol increases the blood system changes caused by benzene. Exposure to toluene slows the rate of clearance of benzene by competing for metabolic pathways. Is there potential for benzene to build-up or accumulate in my body? Benzene is readily absorbed by inhalation or ingestion and is rapidly distributed throughout the body, particularly in fatty tissues. Metabolism occurs primarily in the liver and to a lesser extent in the bone marrow, producing intermediates which account for the toxicity of benzene. In humans, the half life is 1 to 2 days. Accumulation is not expected for benzene or its metabolites. Benzene is primarily exhaled through the lungs, unchanged or excreted as metabolites in the urine.
 |
Document last updated on December 22, 1997
Copyright ©1997-2008 Canadian Centre for Occupational Health & Safety
|
|
