•Oxygen: Some pathogens require oxygen to grow, while others grow when oxygen is absent. Pathogens that grow without oxygen can occur in cooked rice, untreated garlic-and-oil mixtures, and temperature-abused baked potatoes.

•Moisture: Pathogens require moisture in food to grow. The amount of moisture available in food for this growth is called its water activity (aw). It is measured on a scale of 0.0 to 1.0, with water having a water activity of 1.0. Food with a water activity of .85 or higher is ideal for the growth of pathogens.