Final answer:
Waterless hand antiseptics are most effective with a 70% alcohol concentration. Alcohols require water to denature proteins effectively and higher alcohol concentrations do not increase microbial inhibition. Option D.
Step-by-step explanation:
Waterless hand antiseptics are most effective when they contain a 70% alcohol concentration. Both ethyl alcohol (ethanol) and isopropanol (2-methylpropanol) have properties that kill bacteria and viruses, and they are the active ingredients in hand sanitizers. Hand sanitizers usually contain 60% to 80% of either ethanol or isopropanol.
Alcohol concentrations higher than 70% do not increase microbial inhibition; in fact, 100% alcohol solutions are less effective than 70% alcohol solutions because the rapid coagulation of surface proteins in higher concentrations prevents the alcohol from effectively penetrating the cells.
Additionally, alcohols require water to denature proteins effectively, meaning aqueous solutions are preferred.
Hand sanitizers often include glycerin or ethylene to keep the skin from drying out, as alcohols can dehydrate the skin upon application.
It is important to note that while alcohols are bactericidal, fungicidal, and may even be viricidal against enveloped viruses, they are not sporicidal and are volatilizing substances, which means their effectiveness is limited to the time immediately following application. So Option D.