Conditions in the environment that have a negative impact on the health and well-being of a population are known as environmental hazards. These can be natural events, such as an overabundance of insects that destroys crops; a weather pattern that causes a drought or flood; or a sudden, violent disaster such as an earthquake or volcanic eruption. Environmental hazards can also be human-caused problems such as air and water pollution, chemical toxicity, or a poor use of resources that brings about environmental degradation. These events can have an immediate, devastating impact, or they can have more extended consequences. A famine, for example, might cause hundreds of thousands of people to starve to death over a number of months, or exposure to pollution might be associated with long-term health effects over several generations.