The World Health Organization reports that “indoor air pollution from solid fuel use is responsible for almost 2 million annual deaths and 2.7% of the global burden of disease. This makes this risk factor the second biggest environmental contributor to ill health, behind unsafe water and sanitation. Acute lower respiratory infections, in particular pneumonia, continue to be the biggest killer of young children and cause more than 2 million annual deaths. (World) In many communities like Libby, Montana, woodstove heating is a large contributor to wintertime pollution. Because wood burning typically occurs in residential areas, the intake fraction of pollutants inhaled to pollutants emitted was comparable to that of traffic pollution. To address this, Libby conducted a woodstove exchange program that encouraged residents to replace older stoves with newer, cleaner burning models. In all, 90% of woodstoves were replaced or removed. Concentrations of woodstove pollutants have been reduced by 20% - 64% during the November to February period. Additionally, preliminary analysis across the four winter seasons following the exchange shows decreased reporting of childhood wheeze. (Giles) Numerous interventions have been found that reduce indoor air pollution and the associated health effects. These interventions target the source of the pollution, the living environment and the behavior of the user. For instance, the largest reductions can be realized by transitioning from solid fuels to alternative fuel sources that are cleaner and more efficient. Other examples include using improved stoves, improving ventilation and drying wood before burning it to reduce smoke. (World) Ozone still remains an issue because emission and transport of ozone precursors still takes place. The reduction of ozone levels from vehicles has been offset in some parts of the country because of the increase in miles driven. Changes in vehicle engine and exhaust systems and the change of gasoline composition has allowed reductions in ozone. (Lioy) Traffic-related air pollution is an important source of primary and secondary pollutants. In 2003 London initiated a congestion charge scheme (CCS) to address traffic congestion. While the objective was to reduce the traffic congestion in the central city zone, air pollution reduction was a potential co-benefit. The benefits of the CCS on the traffic congestions side were modest and temporary; however, the CCS led to an increase of 183 years of life per 100,000 citizens. More recently, London has initiated an LEZ designed specifically to target air pollution. Heavy-duty diesel vehicles, larger vans, and buses must pay a daily charge to travel through the LEZ. (Giles) Targeting specific sources that contribute significantly to air pollution is an important strategy in improving air quality. For instance, Dublin, Ireland banned the sale of coal in 1990 ban on the sale of coal as a result of heavy black smoke and sulfur dioxide in the air. Within 6 years of the ban, smoke levels had decreased 70% and sulfur dioxide decreased by 35%. Total mortality also decreased by 6% As expected, the largest effects were seen for respiratory and cardiovascular deaths, with decreases of 16% and 10% respectively. (Giles) One of the ways to reduce air pollution emission associated with commuting is to ride a bicycle instead of taking a car. Those trips that are shorter than three miles have been identified as a good target for this shift. It is suggested that bicycling could reduce the vehicle miles travelled in the United States by 0.8 – 1.8%. Potential improvements to public health could result from reduced pollution as well as increased physical activity. (Jarjour) Natural gas produces less pollution than than coal or oil, but getting the fuel out of the ground can be a dirty process. Hydraulic fracturing, or fracking, has raised concerns about toxic air pollutants. The U.S. Environmental Protection Agency (EPA) enacted new air pollution regulations in April 2012 Compliance with the new regulations is expected to greatly reduce emissions of methane and volatile organic compounds (VOCs), particularly from new fracked natural gas wells. (Weinhold) The U.S. Environmental Protection Agency issued a draft report in 2011 that stated the best explanation for a polluted aquifer in Wyoming was hydraulic fracking. The report stated that "the presence of these compounds is consistent with migration from areas of gas production." Amy Mall, a fracking expert at the Natural Resources Defense Council, said the report "underscores the urgent need to get federal rules and safeguards on the books to help protect all Americans from the dangers of fracking." The report sharply contradicts industry claims that fracking has never contaminated drinking water. (Gardner) “Point sources [from industry, municipal sewers, power plants, etc.] have been relatively easy to manage through a command-and-control structure, but things are different today,” Stokes adds. Nonpoint source pollution, which can originate from a city street, suburban lawn or farming operation, has become the primary source of impairment to the nation’s waterways. Protecting rivers, streams and lakes from this type of pollution has proven to be difficult. (Anderson) Decades ago, it wasn’t hard to pinpoint the water pollution problems plaguing the nation. They were too dramatic and obvious to miss. “Lake Erie was considered a dead lake, rivers around the United States used to catch fire, and there were waterways you could literally walk across because of the scum and floating debris,” recalled Allan Stokes, the CEO of America’s Clean Water Foundation. (Anderson) Sediments are soil particles that are carried in water and can settle on the bottoms of lakes. Excessive settlement can impact the gravel beds used by spawning fish as well as lower the storage capacity of lakes and reservoirs. Suspended sediments can cause water to be cloudy causing sight-feeding fish to have difficulty finding food. They can also degrade the quality of drinking water thereby increasing the cost of water treatment. (Brown) Nutrients such as nitrogen and phosphorous are essential in aquatic ecosystems. At high levels, they can lead to excessive algae growth, deplete the dissolved oxygen level in the water, and can alter the species composition. Nutrient concentrations in streams draining farmland were nine times higher than those draining forests. Agricultural fertilizer and livestock manure have been found to be the primary sources of nutrients in streams. Residential areas introduce landscape fertilizers, pet wastes and septic leachate.(Brown) Toxics are chemicals that, at low levels, can damage animals and plants. These include heavy metals such as mercury, lead, cadmium and arsenic. Mining is a great source of heavy metal pollutants in the water supply when metal sediments are washed out by heaving rain. Vehicle traffic and thermoelectric-power-plant emissions are also a source of acidic precipitation that makes it way to the streams. Toxics can also include some pesticides used in farming at a rate one thousand times the level they are used in foresting, pharmaceuticals used for domestic animals. (Brown)