An environmental impact is defined as any change to the environment, whether adverse or beneficial, resulting from a facility’s activities, products, or services. In other words it is the effect that people's actions have on the environment. For example, when volatile organic compounds are released into the environment, the effect or impact is pollution in the form of smog, in this case being negative. It can go the other way, as a person picking up litter can have a beneficial impact on the local environment.
The primary impacts of concern in an energy dependent society often come as a result of our energy use. Burning hydrocarbons like coal and oil to provide us with useful energy results in the emission of carbon dioxide and other pollutants. Other activities causing harm include improper waste disposal to bodies of water and soil, accidental spills of chemicals, increased demand for resources as populations increase (especially due to consumerism), and much more. The impacts that these have on the environment have become clear and include:
There are many issues in the world that are causing one or more of these effects. The oil sands, for instance, are of great concern to many these days as they essentially contribute to each of the above impacts, see environmental impacts of oil sands.
The environmental impact a specific action may have can be analyzed using a life cycle assessment, which is the process of observing a product from its "cradle to grave" and determining the impacts associated with it at each step. These methods are somewhat subjective and resource intensive.
Process hazard analysis involves identifying and assessing potential impacts of unplanned hazardous materials. A team may rank the possible hazards and focus on preventing those that can cause the most harm.