Ireland Beautiful, and the Bay Area Stormwater Management Agencies Association, have focused educational efforts on youth littering. Negligent or lenient law enforcement contributes to littering behavior. Other causes are inconvenience, entitlement and economic conditions. A survey of dumping in Pennsylvania found that the largest number of illegal dumps were in townships without municipal trash hauling. The same report also cites unavailability of curbside trash and recycling service, shortage of enforcement, and habit as possible causes. The presence of litter invites more littering. Two-stage process model The two-stage process model of littering behavior describes the different ways in which people litter. The model was proposed by Chris Sibley and James Liu and differentiates between two types of littering: active and passive. The theory has implications for understanding the different types of litter reduction interventions that will most effectively reduce littering in a given environment. The theory states that, all things being equal, passive littering will be more resistant to change because of two psychological processes: 1. diffusion of responsibility that increases as the latency between when an individual places litter in the environment and when they vacate the territory, and 2. forgetting, which is also more likely to occur at longer delays between when an individual places litter in the environment and when they vacate the territory. Life cycle Litter can remain visible for extended periods of time before it eventually biodegrades, with some items made of condensed glass, styrofoam or plastic possibly remaining in the environment for over a million years. About 18 percent of litter, usually traveling through stormwater systems, ends up in local streams, rivers, and waterways. Uncollected litter can accrete and flow into streams, local bays and estuaries. Litter in the ocean either washes up on beaches or collects in ocean gyres such as the Great Pacific Garbage Patch. About 80 percent of marine debris comes from land-based sources. Some litter that is collected can be recycled, however degraded litter cannot be recycled and eventually degrades to sludge, often toxic. The majority of litter that is collected goes to landfills. Effects Litter can have a detrimental impact on humans and the environment in different ways. Effects on humans Hazardous materials encapsulated within tires and other items of illegally dumped rubbish can leach into water sources, contaminate the soil and pollute the air. Tires are the most often dumped hazardous waste. In 2007 the United States generated 262