A hazard is anything with the potential to cause harm, injury, illness, damage to property, or environmental degradation, such as a slippery floor, a toxic chemical, a moving machine part, or a natural event like a flood. Hazards are potential sources of damage, while risk is the likelihood that harm will occur from that hazard, meaning controlling exposure (like putting up a barrier) reduces the risk even if the hazard remains. Hazards can be natural (earthquakes), anthropogenic (pollution), or biological (bacteria).