Decline in bacterial-related deaths because of water chlorination, milk pasteurization, sewage treatment, vaccinations, antibiotics, isolation of patients. Works for all microbes at right temp. D = time for 1 log drop in bacterial numbers: 1d = 10% survivors, 2d = 1% Factors affecting heat sterilization: moist heat better than dry heat more penetrating, matrix, medium effects, ph effects, solute effects, higher temp, faster killing, ex. Pasteurization reduces microbial numbers in milk, juices, other heat-sensitive foods kills pathogens, improves shelf life. Radiation ionizing: high energy like x and gamma rays, generates ions or reactive metabolites from molecules struck by radiation particles, damages dna and proteins, sterilize medical devices, food. Non-ionizing typically ultraviolet induces dna damage: cannot penetrate solids or liquids, used to disinfect exposed surfaces. Depth filter trap particles within network, like paper, asbestos, glass. Membrane filter polymers blocks passage of particles like sieve. Nucelopore filter polycarbonate films very small holes sieve-like.