Meghan Hodges
Benzene is a highly flammable, colourless liquid with a distinct odour. It is a known carcinogen, causing harmful effects on bone marrow and decreasing red blood cell count, which can lead to anaemia. It is a natural compound, formed from sources such as forest fires and volcanoes, and is also a component of crude oil and gasoline. With its widespread use in various industries, benzene is a common air pollutant, particularly in indoor environments. The level of benzene in the air varies across different regions, with Asian countries exhibiting higher average benzene levels than European and North American countries. Given the absence of a known exposure threshold for benzene's risks, reducing indoor exposure is crucial, and adequate ventilation plays a vital role in mitigating its harmful effects.
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What You'll Learn
Benzene is a carcinogen
Benzene is a known human carcinogen, with sufficient evidence of carcinogenicity from studies conducted on humans. The International Agency for Research on Cancer (IARC) evaluated benzene in 2012 and concluded that there was enough evidence to prove its carcinogenicity in humans, based on a causal relationship with myeloid leukaemia/acute non-lymphocytic leukaemia.
Several cohort studies across various industries and geographical locations have found that occupational exposure to benzene increases the risk of developing cancer. In addition, studies on experimental animals have demonstrated that exposure to benzene causes cancer at multiple tissue sites in rodents. Oral exposure to benzene, for example, has been found to cause cancer of the Zymbal gland, oral cavity, lung, skin, and mammary gland in mice and rats.
Inhalation of benzene is also a cause for concern, as it has been linked to tumours in rats and a tendency towards lymphoid tumours in mice. The presence of benzene in the air is a significant issue, as it exists predominantly in the vapour phase and can remain in the atmosphere for extended periods, ranging from a few hours to days, and even up to two weeks. The lifetime of benzene in the air depends on environmental conditions and the presence of other pollutants.
The primary mode of degradation of benzene in the environment is through oxidation by hydroxyl radicals and subsequent removal by rain. However, other oxidants such as ozone and nitrate radicals also contribute to a lesser extent. The geometric mean of the range of estimates of the excess lifetime risk of leukaemia at an air concentration of 1 μg/m3 is 6 × 10−6. This risk decreases as the concentration of airborne benzene decreases.
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Natural and anthropogenic sources
Benzene is a colourless liquid with a distinct odour that evaporates quickly into the air. It is a known carcinogen, increasing the risk of leukaemia and other blood disorders. It is formed in nature and through human activities.
Natural Sources
Natural sources of benzene include emissions from volcanoes, forest fires, and plant volatiles. It is also a natural part of crude oil and gasoline.
Anthropogenic Sources
Anthropogenic sources of benzene include emissions from crude oil, gasoline, and industrial processes. Benzene is used in the manufacturing of plastics, resins, synthetic fibres, rubbers, dyes, detergents, drugs, and pesticides. Other sources include environmental tobacco smoke, automobile exhaust, automobile refuelling operations, and industrial emissions. Benzene may also be found in glues, adhesives, cleaning products, and paint strippers.
The air around hazardous waste sites, gas stations, and manufacturing plants that produce or use benzene can contain higher levels of benzene. Exposure to benzene can also result from the ingestion of contaminated food or water.
Indoor air generally contains higher levels of benzene than outdoor air. In modern buildings located near heavy traffic or other major outdoor sources of benzene, inlets for fresh air should be located on the least polluted side of the building.
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Benzene in indoor air
Benzene is a colourless, highly flammable liquid with a distinct odour. It is a known human carcinogen, with studies finding links between exposure to benzene and various types of cancer, including leukaemia.
Most human exposure to benzene occurs indoors, as levels are higher inside than outside, and people generally spend most of their time indoors. Attached garages are a major source of indoor benzene pollution, as vehicle exhaust and evaporative emissions from gas-powered equipment can enter the home. Additionally, smoking tobacco, using certain solvents for hobbies or cleaning, and using building materials that off-gas benzene can all contribute to indoor benzene levels.
Soil vapour intrusion is another way that benzene can enter indoor spaces. This occurs when benzene evaporates from a gasoline or fuel oil spill, enters the soil vapour, and migrates through building foundations into the indoor air.
To reduce exposure to benzene indoors, the following measures can be taken:
- Ensure proper sealing between the home and the garage, especially for any connecting doors.
- Install an exhaust fan in the attached garage.
- Avoid idling vehicles or starting gas-powered equipment in the attached garage.
- Do not smoke inside the home or the garage.
- Remove solvents, gasoline-powered tools, and engines from attached garages.
- Maintain adequate ventilation.
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Health effects of benzene exposure
Benzene is a colourless or light-yellow liquid chemical with a sweet smell that evaporates quickly into the air. It is a proven carcinogen, with the ability to damage different components of the biosphere. Long-term exposure to high levels of benzene in the air can cause acute myeloid leukaemia (AML), a blood-related cancer. Other types of leukaemia associated with benzene exposure include acute lymphocytic leukaemia (ALL), chronic lymphocytic leukaemia (CLL), multiple myeloma, and non-Hodgkin lymphoma.
The Department of Health and Human Services (DHHS) and the International Agency for Research on Cancer (IARC) classify benzene as "carcinogenic to humans". The US Environmental Protection Agency (EPA) also classifies benzene as a known human carcinogen.
In addition to the risk of cancer, long-term exposure to benzene can affect the bone marrow, the soft, inner parts of bones where new blood cells are made. This can lead to a decrease in red blood cells, resulting in anaemia and causing individuals to feel weak and tired. Some studies have also found that long-term exposure to benzene might harm reproductive organs. Irregular menstrual cycles and ovary shrinkage have been observed in women who breathed in high levels of benzene for many months. However, it is unclear if benzene directly caused these effects.
Short-term exposure to high levels of benzene can also have adverse health effects. Breathing in high doses of benzene can impact the nervous system, leading to drowsiness, dizziness, headaches, tremors, confusion, and even unconsciousness. Consuming foods or drinks contaminated with high levels of benzene can cause vomiting, stomach irritation, dizziness, sleepiness, convulsions, and rapid heart rate. In extreme cases, inhaling or ingesting very high levels of benzene can be fatal. Exposure to benzene liquid or vapour can irritate the skin, eyes, and throat, and direct contact with the skin can cause redness and blistering.
Overall, benzene exposure poses significant health risks, and it is essential to minimise indoor and outdoor exposure levels as much as possible.
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Benzene air quality standards
Benzene is a colourless, highly flammable liquid with a distinct odour. It is a proven carcinogen, with exposure linked to acute and chronic nonlymphocytic leukemia, chronic lymphocytic leukemia, and non-cancer risks like headaches, dizziness, and eye and skin irritation.
The World Health Organization (WHO) has published guidelines for indoor air quality, which include recommendations for benzene levels. According to the WHO, there is no known exposure threshold for the risks of benzene exposure, so it is important to reduce indoor exposure levels as much as possible. This can be achieved by reducing or eliminating human activities that release benzene, such as smoking tobacco, using certain solvents, and using building materials that off-gas benzene. Adequate ventilation is also important, with fresh air inlets ideally located on the least polluted side of the building.
Literature comparing air quality standards for benzene and their monitoring methods is limited. However, one study found that only 53 out of 193 United Nations member states have ambient air quality standards for benzene, and even in those cases, the standards were often not protective of public health. The preferred method of analysis, Gas Chromatography and Mass Spectroscopy, is not cost-effective and is unsuitable for real-time continuous monitoring.
Data suggests that the average benzene level in the ambient air of Asian countries is approximately 3.5 times higher than indoor levels, while the ratio of outdoor to indoor benzene levels in European and North American countries is much lower, at 1.2 and 7.7, respectively. These findings will be useful for policymakers when revising future air quality guidelines.
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Frequently asked questions
Benzene is a colourless liquid with a distinct odour. It is highly flammable and has a low boiling point, causing it to evaporate quickly. It is a known carcinogen and can cause serious health issues.
Benzene is released into the air through both natural and human-made processes. Natural sources include volcanoes and forest fires. Human-made sources include crude oil, gasoline, cigarette smoke, and industrial processes. It is also used in the manufacturing of plastics, resins, and synthetic fibres.
Long-term exposure to high levels of benzene in the air can lead to leukemia, a type of blood cancer. It can also cause anemia by reducing red blood cell production in bone marrow. Benzene can harm the immune system, increasing the risk of infections. Additionally, it has been linked to irregular menstrual cycles and reduced ovary size in women.
Currently, only 53 out of 193 United Nations member states have established ambient air quality standards for benzene. This includes the member states of the European Union. However, even in countries with standards, the regulations are often inadequate to protect public health.
To reduce the risk of benzene exposure, it is important to minimise indoor activities that release benzene, such as smoking tobacco or using certain solvents. Adequate ventilation and fresh air are crucial. If you are near a benzene release, it is important to follow the instructions of emergency teams, which may include evacuating the area or seeking medical attention immediately.
