Final answer:
Household disinfectants with a 99.99% germ-killing claim are typically highly effective, with a phenol coefficient greater than 1.0. Surfaces may be coated with copper, nickel, or zinc to prevent transmission, while soaps are not disinfectants. Exposure to some pathogens is necessary for a robust immune system.
Step-by-step explanation:
When evaluating household disinfectants, it's important to understand their efficacy in killing microbes, such as bacteria and viruses. The claim that a disinfectant kills 99.99% of germs suggests that it is highly effective. This level of efficacy is often communicated by determining the phenol coefficient of the disinfectant, which compares its effectiveness to that of phenol. A coefficient greater than 1.0 indicates the disinfectant is more effective than phenol. In clinical settings, high-touch surfaces like doorknobs may be coated with metals like copper, nickel, or zinc to prevent microbial transmission.
However, not all solutions used for cleaning are disinfectants. For example, soaps are not classified as disinfectants but rather as cleansing agents. Moreover, certain substances, such as mercury-based compounds, have become less popular due to safety concerns. Chemical disinfectants may include chlorine bleach or other chlorine-containing products and they are incapable of achieving sterilization since certain microbes like endospores can survive the disinfection process.
For personal hygiene, compounds like isopropanol and ethanol are effective in inactivating many bacteria and viruses, and typically constitute 60% to 80% of hand sanitizers. Nonetheless, these agents do not achieve sterility — they reduce the number of microbes to a safer level, not completely eliminating them.
Despite the high efficacy of disinfectants, it's worth noting that complete avoidance of pathogens is neither possible nor desirable. Exposure to some level of pathogens is necessary to build and maintain a healthy immune system.