How many hours will it take a pathogen in the temperature danger zone to grow to levels high enough to make someone sick?

Pathogens can multiply rapidly when food is kept in the temperature danger zone, which is typically between 41°F (5°C) and 135°F (57°C). When food is held in this range, bacteria can double in number approximately every 20 minutes under optimal conditions.

To determine how long it takes to reach dangerous levels, it's important to understand that epidemiological studies suggest that food can become unsafe after about four hours in this temperature range. By this time, the bacterial load may be high enough to cause illness if consumed.

While pathogens can begin to proliferate in as little as one hour, significant levels that can lead to foodborne illness often take a longer duration to develop. Thus, the correct answer indicates that four hours is the typical point at which the risk of illness significantly increases due to the growth of microorganisms.