The terms sanitization and sterilization both describe processes intended to control microbial contamination, yet they represent fundamentally different levels of biological cleanliness. While both are necessary for maintaining public health and safety across various settings, they are distinguished by their specific objective and the resulting microbial load. Sanitization aims to achieve a level of cleanliness deemed safe for general use, whereas sterilization is an absolute process designed to eliminate all forms of microbial life.
The Standard of Microbial Elimination
The core difference between these two processes lies in the degree of microbial killing they are designed to achieve. Sanitization is a process focused on reducing the number of microorganisms to a safe level established by public health standards. This is typically quantified as a 3-log reduction, meaning a 99.9% decrease in the population of disease-causing organisms. This reduction is considered sufficient for environments where the risk of infection is low, such as food preparation areas. Importantly, sanitization does not typically kill all types of pathogens, particularly the highly resistant bacterial spores.
Sterilization, by contrast, is the total destruction and removal of all viable microbial life, which includes bacteria, fungi, viruses, and the hardy bacterial spores. This process aims for an absolute standard, which is mathematically expressed using the Sterility Assurance Level (SAL). The standard SAL for sterilized medical devices is \(10^{-6}\), representing a one-in-a-million probability of a single surviving microorganism on an item. The concept of SAL highlights that the probability of survival is reduced to an extremely low, acceptable risk.
Common Processes and Agents
Sanitization methods often rely on mild heat or chemical agents that are safe for frequent use and rapid application. Common chemical sanitizers include chlorine solutions, such as diluted sodium hypochlorite, and Quaternary Ammonium Compounds (Quats). Quats typically work by disrupting the cell membrane of the microbes and are often applied to food-contact surfaces at about 200 parts per million (ppm). Chlorine solutions are used at concentrations around 50 to 100 ppm for sanitizing. These chemical concentrations are effective against vegetative bacteria and some viruses but are insufficient to destroy bacterial spores.
Sterilization requires intensive physical or chemical methods to guarantee the destruction of all microbial forms. The primary physical method is moist heat sterilization, commonly performed using an autoclave. This process uses pressurized saturated steam, often at 121°C (250°F) at 15 pounds per square inch (psi) above atmospheric pressure, maintained for at least 15 to 20 minutes. The high pressure allows the water to reach temperatures above its normal boiling point, rapidly denaturing and coagulating the structural proteins of all organisms. For items that cannot withstand extreme heat, chemical sterilants are used, such as ethylene oxide gas or vaporized hydrogen peroxide plasma. These agents penetrate packaging and objects, chemically inactivating all microorganisms.
Appropriate Settings for Use
The environment and the risk associated with an item’s use dictate whether sanitization or sterilization is required. This risk assessment is codified in healthcare settings by systems like the Spaulding Classification, which categorizes medical devices based on the potential for infection.
Sterilization is strictly mandated for items classified as “critical” because they penetrate sterile tissue or the vascular system. Surgical instruments, implanted medical devices, and cardiac catheters must be sterilized to achieve the \(10^{-6}\) SAL, as any microbial presence in these contexts could cause a catastrophic infection.
Sanitization is appropriate for “non-critical” items, which are devices or surfaces that only contact intact skin. Examples include blood pressure cuffs, stethoscopes, and general environmental surfaces like floors or countertops. In these low-risk settings, reducing the microbial load to a safe level is sufficient for preventing disease transmission.
Items falling between these two extremes are classified as “semi-critical,” such as endoscopes and respiratory therapy equipment, which contact mucous membranes or non-intact skin. These require a process known as high-level disinfection, which kills all microorganisms except for a small number of bacterial spores, demonstrating a level of pathogen control that approaches, but does not meet, the absolute standard of sterilization.