Blood is classified as a biohazard because it can transmit infectious agents that threaten human health. This danger stems from the microorganisms it may harbor, known as bloodborne pathogens. Because it is impossible to know the infectious status of any human blood without testing, it must be handled with extreme caution, making universal precautions a necessity.
The Core Threat: Bloodborne Pathogens
The danger in blood stems from its potential to carry bloodborne pathogens, which are viruses or bacteria that cause serious diseases in humans. The three pathogens of greatest concern in occupational exposure settings are the Hepatitis B Virus (HBV), the Hepatitis C Virus (HCV), and the Human Immunodeficiency Virus (HIV). These viruses target vital systems, leading to severe, chronic, and sometimes fatal conditions.
Hepatitis B and C viruses primarily attack the liver, potentially leading to chronic infection, cirrhosis, or liver cancer. HBV is particularly robust and can remain infectious on environmental surfaces, even in dried blood, for up to seven days. HCV is considered the most common bloodborne infection in the United States and is a leading cause of chronic liver disease.
HIV is more fragile and survives only briefly outside the body, but it attacks and weakens the immune system, making the host vulnerable to other infections. Because these pathogens can survive outside the body for varying periods, contaminated surfaces pose a risk. While testing minimizes the risk of infection through blood transfusions, the hazard remains in uncontrolled settings like accidents, crime scenes, or medical waste handling.
How Transmission and Exposure Occur
For a bloodborne pathogen to transmit, contaminated blood must find a route into the bloodstream of a new host. This process is categorized into three main routes of occupational exposure. The most common route is percutaneous injury, which involves a puncture or cut from a contaminated sharp object like a needle, scalpel, or broken glass.
Exposure can also occur through contact with mucous membranes found in the eyes, nose, or mouth, where splashes or sprays of infected blood provide a direct path for the pathogen to enter. The third route is contact with non-intact skin, meaning skin that has cuts, abrasions, or dermatitis.
The risk of transmission depends on the volume of blood, the concentration of the pathogen, and its viability outside the body. Although dried blood is less infectious than fresh blood, caution is warranted because viruses like HBV can persist for a full week. This persistence necessitates that cleanup and disposal procedures address both liquid and dried blood residues.
Regulatory Classification and Safe Handling
Strict guidelines govern the handling of blood and related materials. The foundation of these guidelines is “Universal Precautions,” which mandates that all human blood and certain body fluids be treated as if they are known to be infectious for HIV, HBV, and other pathogens. This approach eliminates the need to determine a source’s infection status before taking protective action.
The Occupational Safety and Health Administration (OSHA) enforces the Bloodborne Pathogens Standard, requiring employers to implement specific controls to protect workers. These controls include engineering controls, such as using safer medical devices like needleless systems, and work practice controls, such as prohibiting the manual recapping of needles. Training, personal protective equipment (PPE), and a readily available Hepatitis B vaccine series are also mandatory elements of the standard.
Materials contaminated with blood require specialized disposal, often signified by the internationally recognized biohazard symbol. Contaminated non-sharp waste, such as blood-saturated gauze, must be placed in designated leak-proof containers, typically lined with red biohazard bags. Sharps, including needles, scalpels, and broken glass, must be discarded immediately into rigid, puncture-resistant sharps containers to prevent accidental injury and exposure.