Benzene is a colorless, sweet-smelling liquid that is a natural component of crude oil and a byproduct of various industrial processes. It is a highly volatile organic compound, widely used as an industrial solvent and a precursor chemical in the manufacture of plastics, resins, nylon, and synthetic fibers. Benzene is also found in gasoline and tobacco smoke, leading to widespread environmental and occupational exposure. Understanding the pathways by which this toxic chemical enters the human body is a major concern, particularly whether skin contact represents a significant route of exposure.
Benzene and the Skin Barrier
Yes, benzene can be absorbed through the skin, providing a pathway for the compound to enter the systemic circulation. The skin’s primary defense is the outermost layer, the stratum corneum, which acts as a lipid-rich barrier. Benzene is a nonpolar molecule with high lipid solubility, allowing it to readily interact with and dissolve into this fatty layer. This partitioning into the stratum corneum facilitates its passive diffusion across the skin layers and into the underlying tissues. Once it breaches the outer layer, the molecule moves quickly through the epidermis and dermis, where it encounters blood vessels and enters the bloodstream. This rapid absorption means that even brief contact with liquid benzene can contribute to the overall internal dose.
Variables Affecting Absorption Rate
The speed and amount of benzene absorbed through the skin are dependent on the conditions of exposure. A primary factor is the concentration of benzene in the liquid that contacts the skin, as higher concentrations generate a greater driving force for diffusion. The duration of contact is directly proportional to the total absorbed dose, meaning longer exposure allows a larger amount to penetrate. The physical integrity of the skin dramatically alters the absorption rate; damaged, cut, or abraded skin loses the protective function of the stratum corneum, leading to much faster uptake. Additionally, the vehicle in which benzene is dissolved influences the rate, as some organic solvents can temporarily disrupt the skin barrier, enhancing permeability. Increased skin temperature, often associated with physical activity or warm environments, can accelerate absorption by increasing blood flow near the surface.
Health Effects After Entering the Body
Once absorbed into the bloodstream, benzene is distributed throughout the body, tending to accumulate temporarily in fatty tissues due to its lipophilic nature. Systemic toxicity stems primarily from the metabolism of benzene, which occurs in the liver by the cytochrome P450 enzyme system, specifically CYP2E1. This process transforms the compound into toxic, reactive intermediate metabolites, such as benzene oxide and trans,trans-muconaldehyde. These metabolites damage the genetic material of cells and disrupt cellular processes. Acute, high-level exposure can cause central nervous system effects, including dizziness, headache, and drowsiness. The most concerning effects are chronic, long-term exposures, which classify benzene as a known human carcinogen. The primary target of chronic toxicity is the bone marrow, leading to suppressed blood cell production that can result in aplastic anemia, leukopenia, and various types of leukemia, especially acute myeloid leukemia (AML).
Comparing Exposure Routes and Prevention
While dermal absorption is a measurable route of entry, inhalation remains the most common route of exposure in occupational settings due to benzene’s volatility. Because benzene readily evaporates, airborne concentrations are often the primary concern for workers, especially when handling large volumes in poorly ventilated areas. However, when airborne concentrations are low, the relative contribution of dermal exposure from direct liquid contact becomes increasingly significant. Prevention measures must address both pathways to minimize the total absorbed dose. In industrial settings, the use of appropriate Personal Protective Equipment (PPE), such as chemical-resistant gloves, is necessary to prevent liquid contact. Adequate ventilation systems are required to control airborne vapor levels, adhering to regulatory standards for exposure limits. Immediate washing protocols are important to reduce the duration of contact, which is a major variable affecting the absorbed dose. Some experts recommend that the liquid concentration of benzene that triggers protective measures be reduced to as low as 0.01% to protect against the long-term cancer risk associated with chronic dermal exposure.