1.
Bicycle
–
A bicycle, often called a bike or cycle, is a human-powered, pedal-driven, single-track vehicle, having two wheels attached to a frame, one behind the other. A bicycle rider is called a cyclist, or bicyclist, Bicycles were introduced in the 19th century in Europe and as of 2003, more than 1 billion have been produced worldwide, twice as many as the number of automobiles that have been produced. They are the means of transportation in many regions. They also provide a form of recreation, and have been adapted for use as childrens toys, general fitness, military and police applications, courier services. The basic shape and configuration of an upright or safety bicycle, has changed little since the first chain-driven model was developed around 1885. But many details have been improved, especially since the advent of modern materials and these have allowed for a proliferation of specialized designs for many types of cycling. The bicycles invention has had an effect on society, both in terms of culture and of advancing modern industrial methods. The word bicycle first appeared in English print in The Daily News in 1868, to describe Bysicles and trysicles on the Champs Elysées, the word was first used in 1847 in a French publication to describe an unidentified two-wheeled vehicle, possibly a carriage. The design of the bicycle was an advance on the velocipede, Other words for bicycle include bike, pushbike, pedal cycle, or cycle. In Unicode, the point for bicycle is 0x1F6B2. The entity 🚲, in HTML produces
2.
Cycling infrastructure
–
Cycling infrastructure refers to all infrastructure which may be used by cyclists. The manner in which the road network is designed, built. The cycling network may be able to provide the users with direct, convenient routes minimizing unnecessary delay, settlements with a dense road network of interconnected streets tend to be viable utility cycling environments. A bikeway is a lane, route, way or path which in some manner is specifically designed, bike lanes demarcated by a painted marking are quite common in many cities. Cycle tracks demarcated by barriers, bollards or boulevards are quite common in some European countries such as the Netherlands, Denmark and they are also increasingly common in other major cities such as New York City, Melbourne, Ottawa, Vancouver and San Francisco. Montreal and Davis, California, which have had segregated cycling facilities with barriers for several decades, are among the earliest examples in North American cities, some share the roadway with motor vehicles—bicycle boulevard, sharrow, advisory bike lane—or shared with pedestrians—greenway, shared use path. The term bikeway is largely used in North America to describe all routes that have designed or updated to encourage more cycling or make cycling safer. There is no usage of segregation, in some cases it can mean the exclusion of motor vehicles. Thus, it includes bike lanes with solid painted lines but not lanes with dotted lines and it includes cycle tracks as physically distinct from the roadway and sidewalk. And it includes bike paths in their own right of way exclusive to cycling, there have been a lot of studies on the safety of all types of bikeways. Proponents say that segregation of cyclists from fast or frequent motorized traffic is necessary to provide a safe, opponents point out the increased risk from various types of infrastructure including shared use paths. Different countries have different ways to define and enforce bikeways. Controversies have surrounded bikeways, particularly in North America and the United Kingdom, proponents argue that dedicated bike lanes have been implemented in many cities and are both popular and safe. Jurisdictions have guidelines around the selection of the right bikeway treatments in order make routes more comfortable, a buffered bike lane is typically a lane with a wide painted buffer to demarcate a larger gap between the cycle lane and other traffic. A physically marked and separated lane dedicated for cycling that is on or directly adjacent to the roadway, bike paths are paths with their own right of way dedicated to cycling, though in many cases shared with pedestrians and other non-motorized traffic. A greenway is a long, narrow piece of land, often used for recreation and pedestrian and bicycle user traffic, a shared use path supports multiple modes, such as walking, bicycling, inline skating and people in wheelchairs. A bicycle boulevard is a low speed street which has been optimized for bicycle traffic, bicycle boulevards discourage cut-through motor vehicle traffic but allow local motor vehicle traffic. They are designed to give priority to cyclists as through-going traffic, an advisory bike lane is a bike lane which motorists may legally encroach
3.
Elizabeth, New Jersey
–
Elizabeth is both the largest city and the county seat of Union County, in New Jersey, United States. As of the 2010 United States Census, the city had a population of 124,969. The population increased by 4,401 from the 120,568 counted in the 2000 Census, which had in turn increased by 10,566 from the 110,002 counted in the 1990 Census. For 2015, the Census Bureaus Population Estimates Program calculated a population of 129,007, in 2008, Elizabeth was named one of Americas 50 Greenest Cities by Popular Science magazine, the only city in New Jersey selected. Elizabeth, originally called Elizabethtown and part of the Elizabethtown Tract, was founded in 1664 by English settlers. The town was not named for Queen Elizabeth I as many people may assume and she was the daughter of Philippe de Carteret II, 3rd Seigneur de Sark and Anne Dowse. The town served as the first capital of New Jersey, after independence, it was from Elizabethtown that George Washington embarked by boat to Manhattan for his 1789 inauguration. There are numerous memorials and monuments of the American Revolution in Elizabeth, on March 19,1857, the city became part of the newly created Union County. Portions of the city were taken to form Linden Township on March 4,1861, the first major industry, the Singer Sewing Machine Company came to Elizabeth and employed as many as 2,000 people. In 1895, it saw one of the first car companies, the Electric Boat Company got its start building submarines for the United States Navy in Elizabeth, New Jersey, beginning with the launch of USS Holland in 1897. These pioneering naval craft were developed at Lewis Nixons Crescent Shipyard in Elizabeth between the years 1896–1903, Elizabeth grew in parallel to its sister city of Newark for many years, but has been more successful in retaining a middle-class presence and was mostly spared riots in the 1960s. On September 18,2016, a backpack holding five bombs was discovered outside NJ Transits Elizabeth train station, one bomb detonated accidentally when a bomb squad robot failed to disarm the contents of the backpack, no one was hurt. Police were initially unsure if this event was related to bombs in Seaside Park, New Jersey and Manhattan that had exploded the previous day. According to the United States Census Bureau, the city had an area of 13.464 square miles. Elizabeth is bordered to the southwest by Linden, to the west by Roselle and Roselle Park, to the northwest by Union and Hillside, to the east the city is across the Newark Bay from Bayonne in Hudson County and the Arthur Kill from Staten Island, New York. Unincorporated communities, localities and place names located partially or completely within the township include Elizabethport, the city of Elizabeth has several distinct districts and neighborhoods. Midtown also occasionally known as Uptown, is the commercial district. It includes the First Presbyterian Church and St. Johns Episcopal Church, the First Presbyterian Church was a battleground for the American Revolution
4.
Urban sprawl
–
In addition to describing a particular form of urbanization, the term also relates to the social and environmental consequences associated with this development. In Continental Europe the term peri-urbanisation is often used to denote similar dynamics and phenomena, There is widespread disagreement about what constitutes sprawl and how to quantify it. For example, some commentators measure sprawl only with the number of residential units per acre in a given area. But others associate it with decentralization, discontinuity, segregation of uses, the term urban sprawl is highly politicized, and almost always has negative connotations. It is criticized for causing environmental degradation, and intensifying segregation and undermining the vitality of existing urban areas, due to the pejorative meaning of the term, few openly support urban sprawl as such. The term has become a cry for managing urban growth. Definitions of sprawl vary, researchers in the field acknowledge that the term lacks precision and he argued that a better way to identify sprawl was to use indicators rather than characteristics because this was a more flexible and less arbitrary method. He proposed using accessibility and functional space as indicators. Ewings approach has been criticized for assuming that sprawl is defined by negative characteristics, what constitutes sprawl may be considered a matter of degree and will always be somewhat subjective under many definitions of the term. The following characteristics are associated with sprawl, This refers to a situation where commercial, residential, institutional and industrial areas are separated from one another. Consequently, large tracts of land are devoted to a use and are segregated from one another by open space, infrastructure. The degree to which different land uses are mixed together is used as an indicator of sprawl in studies of the subject. Job sprawl is another land use symptom of urban sprawl and car-dependent communities, spatial mismatch is related to job sprawl and economic environmental justice. Job sprawl has been documented and measured in various ways and it has been shown to be a growing trend in Americas metropolitan areas. The Brookings Institution has published articles on the topic. In 2005, author Michael Stoll defined job sprawl simply as jobs located more than 5-mile radius from the CBD, and measured the concept based on year 2000 U. S. Census data. These two authors used three geographic rings limited to a 35-mile radius around the CBD,3 miles or less,3 to 10 miles and this compares to the year 1998 -23. 3%,34. 2%, and 42. 5% in those respective rings. The study shows CBD employment share shrinking, and job growth focused in the suburban and exurban outer metropolitan rings, Sprawl is often characterized as consisting of low-density development
5.
Downtown Newark
–
Downtown Newark, officially known as the Central Business District, is an unincorporated community and neighborhood within the city of Newark in Essex County, New Jersey, United States. Downtown Newark is Newarks central business, retail, and cultural district and it is located at a bend in the Passaic River. Downtown is the site of the original Puritan settlement of Newark, the first settlers, led by Robert Treat, landed not far from the present site of the New Jersey Performing Arts Center. The intersection of Broad and Market Streets, known as Four Corners was once considered the busiest intersection in the nation, most of Newarks office buildings are located in this area. In the post-World War II era, downtown seemed to be moving north during the New Newark architectural period, since the 1967 riots, it has been shifting slightly east in the direction of Newark Penn Station, the Gateway Center and the Passaic River. Downtown is also home to Seton Hall University School of Law and Aljira and it was once home to a Chinatown neighborhood centered on Mulberry Arcade, which was off of Mulberry Street, near Lafayette and Green Streets. The $375 million Prudential Center, home to the New Jersey Devils, opened on October 25,2007, at the time, the arena was the New York metropolitan areas first all-new professional sports venue in over two decades. Though it has a number of buildings of architectural significance. The buildings range from four to 35 stories tall presenting indiscriminate architecture, much of the citys retail and commercial developments are centered on Broad Street and Market Street. The intersection of the two streets, known as Four Corners is widely considered to be one of the busiest in the state, both Broad Street and Market Street are a bustle of activity crowded with numerous shops. Broad Street has many street vendors as well, at night however the streets are vacant and shops are closed. The City of Newark is committed to turning downtown into a 24-hour city, the former Hahnes and Lefcourt buildings are going to be converted into condominiums beginning in 2005. Rutgers–Newark has built a six hundred bed dorm on Central Avenue, an old office building on Clinton Street has already successfully been converted to luxury lofts. Additionally,1180 Raymond across from Military Park - Newarks second tallest building - completed a $150 million conversion to apartments in 2006. Most buses pass through Downtown and it is a shopping district of most Newark area residents. Washington Street Station, Penn Station, Military Park Station and all the stops on the Newark Light Rail serve the downtown area, interstate 280 lies just north of Downtown, running parallel to New Jersey Transit rail operations. The Main Library is on Washington Park and served by the Newark Light Rail, triangle Park List of tallest buildings in Newark Newark Downtown District website Newark Visitors Center Living Downtown Master Plan 2008 Bagli, Charles V. Investors Bet on Revival for Troubled Newark, investors Bet on Revival for Troubled Newark New York Times 1998 Newark A City of Optimism and Progress New York Times 1913 Elements of Urbanism 2008 GoNewark website
6.
Utility cycling
–
Utility cycling encompasses any cycling done simply as a means of transport rather than as a sport or leisure activity. It is the original and most common type of cycling in the world, Utility or transportational cycling generally involves travelling short and medium distances, often in an urban environment. It includes commuting, going shopping and running errands, as well as heading out to see friends and it also includes economic activity such as the delivering of goods or services. Velotaxis can also provide a transport service like buses and taxicabs. Utility cycling is known to have social and economic benefits. In the Chinese city of Beijing alone, there are a four million bicycles in use. As of 2000, there were an estimated 80 million bicycles in Japan, accounting for 17% of commuter trips, the development of the safety bicycle was arguably the most important change in the history of the bicycle. It shifted their use and public perception from being a toy for sporting young men to being an everyday transport tool for men—and, crucially. By the start of the 20th Century, cycling had become an important means of transportation, bicycling clubs for men and women spread across the U. S. and across European countries. Cycling steadily became more important in Europe over the first half of the twentieth century, automobiles became the preferred means of transportation. Over the 1920s, bicycles gradually became considered childrens toys, for most of the twentieth century, the great majority of cycling in the UK took place on roads Utility bicycles have many standard features to enhance their usefulness and comfort. Chain guards and mudguards, or fenders, protect clothes and moving parts from oil, front-mounted wicker or steel baskets for carrying goods are often used. Rear luggage carriers can be used to carry such as school satchels. Panniers or special luggage carriers enable the transport of goods and are useful for shopping, parents sometimes add rear-mounted child seats and/or an auxiliary saddle fitted to the crossbar to transport children. Trailers of various types and load capacities may be towed to increase cargo capacity. In many jurisdictions bicycles must be fitted with a bell, reflectors, protective rain gear is often an essential part of the utility cyclists wardrobe, especially in countries with high rainfall levels. Many different factors combine to influence levels of utility cycling, in developing economies, a large amount of utility cycling may be seen simply because the bicycle is the most affordable form of vehicular transport available to many people. In richer countries, where people can have the choice of a mixture of transport types, in developed countries cycling has to compete with, and work with, alternative transport modes such as private cars, public transport and walking
7.
Grid plan
–
The grid plan, grid street plan or gridiron plan is a type of city plan in which streets run at right angles to each other, forming a grid. In the context of the culture of ancient Rome, the grid method of land measurement was called centuriation. The grid plan dates from antiquity and originated in multiple cultures, by 2600 BC, Mohenjo-daro and Harappa, major cities of the Indus Valley Civilization, were built with blocks divided by a grid of straight streets, running north-south and east-west. Each block was subdivided by small lanes, the cities and monasteries of Gandhara, dating from the 1st millennium BC to the 11th century AD, also had grid-based designs. Islamabad, the capital of Pakistan since 1959, was founded on the grid-plan of the nearby ruined city of Sirkap. A workers village at Giza, Egypt, housed a rotating labor force and was out in blocks of long galleries separated by streets in a formal grid. Many pyramid-cult cities used a common orientation, an axis from the royal palace. Hammurabi was a king of the Babylonian Empire who made Babylon one of the greatest cities in antiquity and he rebuilt Babylon, building and restoring temples, city walls and public buildings, and building canals for irrigation. The streets of Babylon were wide and straight, intersected approximately at right angles, the tradition of grid plans is continuous in China from the 15th century BC onward in the traditional urban planning of various ancient Chinese states. Guidelines put into form in the Kaogongji during the Spring and Autumn period stated. Three gates on each side of the lead into the nine main streets that crisscross the city. Teotihuacan, near modern-day Mexico City, is the largest ancient grid-plan site in the Americas, the citys grid covered eight square miles. Perhaps the most well-known grid system is spread through the colonies of the Roman Empire. The archetypal Roman Grid was introduced to Italy first by the Greeks, with such information transferred by way of trade, although the idea of the grid was present in Hellenic societal and city planning, it was not pervasive prior to the 5th century BC. However, it slowly gained primacy through the work of Hippodamus of Miletus, the concept of a grid as the ideal method of town planning had become widely accepted by the time of Alexander the Great. His conquests were a step in the propagation of the grid plan throughout colonies, some as far-flung as Taxila in Pakistan, that would later be mirrored by the expansion of the Roman Empire. The Greek grid had its streets aligned roughly in relation to the points and generally looked to take advantage of visual cues based on the hilly landscape typical of Greece. The Etruscan people, whose territories in Italy encompassed what would eventually become Rome and it was based on Greek Ionic ideas, and it was here that the main east-west and north-south axes of a town could first be seen in Italy
8.
Dead end (street)
–
A dead end, also known as a cul-de-sac, is a street with only one inlet/outlet. While historically built for reasons, one of its modern uses is to calm vehicle traffic. The term dead end is understood in all varieties of English, some of these are used only regionally. In the United States and other countries, cul-de-sac is often not a synonym for dead end and refers to dead ends with a circular end. See below for regionally used terms, Dead ends existed in towns and cities long before the automotive 20th century, particularly in Arab and Moorish towns. The earliest example was unearthed in the El-Lahun workers village in Egypt, the village is laid out with straight streets that intersect at right angles, akin to a grid, but irregular. Dead-end streets appeared also during the period of Athens and Rome. The 15th century architect and planner Leon Battista Alberti implies in his writings that dead-end streets may have been used intentionally in antiquity for defense purposes, the same opinion is expressed by an earlier thinker, Aristotle, when he criticized the Hippodamian grid. But for security in war the opposite, as it used to be in ancient times, for that is difficult for foreign troops to enter and find their way about when attacking. In the UK, their existence is implied by an 1875 law which banned their use in new developments. In the earlier periods, traffic was excluded from residential streets simply by gates or by employing the cul-de-sac and it was in the UK that the cul-de-sac street type was first legislated into use, with The Hampstead Garden Suburb Act 1906. Unwins applications of the cul-de-sac and the related crescent always included pedestrian paths independent of the road network, the 1906 Act defined the nature of the cul-de-sac as a non-through road and restricted its length to 500 feet. Garden cities in the UK that followed Hampstead, such as Welwyn Garden City all included culs-de-sac, the US Federal Housing Authority recommended and promoted their use through their 1936 guidelines and the power of lending development funds. In Canada, a variation of Stein’s Radburn 1929 plan that used crescents instead of culs-de-sac was built in 1947 in Manitoba, Wildwood Park, Winnipeg, the Varsity Village and Braeside, subdivisions in Calgary, Alberta also used the Radburn model in the late 1960s. Although dead end streets, i. e. Doxiadis has additionally argued their important role in separating man from machine, originally unplanned dead ends have been created in the centers of cities that are laid on a grid by blocking through traffic. A recent variation of limiting traffic is the closure by using retractable bollards which are activated by designated card holders only. However, not only do they stop cars, they also stop ambulances and other emergency vehicles, Dead ends are created in urban planning to limit through-traffic in residential areas. This design improvement, which selectively excludes one mode of transport while permitting others and its application retains the dead ends primary function as a non-through road, but establishes complete pedestrian and bicycle network connectivity
9.
Subdivision (land)
–
Subdivision is the act of dividing land into pieces that are easier to sell or otherwise develop, usually via a plat. The former single piece as a whole is known in the United States as a subdivision. If it is used for housing it is known as a housing subdivision or housing development. Subdivisions may also be for the purpose of commercial or industrial development, in the United States, the creation of a subdivision was often the first step toward the creation of a new incorporated township or city. Contemporary notions of subdivisions rely on the Lot and Block survey system and this was followed by publication of the Standard City Planning Enabling Act in 1928. It includes resubdivision and, when appropriate to the context, relates to the process of subdividing or to the land or territory subdivided, the intention is to cover all subdivision of land where the immediate or ultimate purpose is that of selling the lots or building on them. A subdivision does not need to be sold, in whole or in part, a subdivision plat approved by a local planning commission, once recorded in a registry of deeds, is generally deemed to have created the parcels of land identified on the plat itself. The problem of division of property was identified by the SCPEA in the footnote to the definition of subdivision. In some jurisdictions, a division of property does not constitute a legal subdivision for purposes of separate conveyancing of the subdivided parcels. Interpretations of this vary among American jurisdictions, in the Philippines, subdivisions are areas of land that have been subdivided into individual residential plots. Whereas some subdivisions comprise exclusive gated communities, others are merely demarcations denoting a specific neighborhood, some subdivisions may conduct autonomous security, or provide basic services such as water and refuse management. Most subdivisions are governed by associations made up of members who are residents of the subdivision, in the Philippines, subdivisions are also known as villages. In Alberta, subdivision is the dividing of a parcel of land into two or more parcels, each to be given a separate title. Subdivision is also used for existing lot line adjustments, exceptions may occur with parcels of land that contain more than one quarter section, a river lot, a lake lot, or some settlement lots created prior to July 1,1950
10.
Fused grid
–
The fused grid is a street network pattern first proposed in 2002 and subsequently applied in Calgary, Alberta and Stratford, Ontario. It represents a synthesis of two known and extensively used network concepts, the grid and the Radburn pattern, derivatives of which are found in most city suburbs. Both concepts were self-conscious attempts to organize urban space for habitation, the grid was conceived and applied in the pre-automotive era of cities starting circa 2000 BC and prevailed until about 1900 AD. Both these patterns appear throughout North America, Fused refers to a systematic recombination of the essential characteristics of each of these two network patterns. Modern urban planners generally classify street networks as either organic or planned, planned networks tend to be organized according to geometric patterns, while the organic networks are believed to emerge from spontaneous, unorganized growth. Architectural historian Spiro Kostof writes that The word grid is a convenient, gridiron in the US implies a pattern of long narrow blocks, and checkerboard a pattern of square blocks. In addition to the angle being a key characteristic, a second attribute of equal importance is its imputed openness. Loosely interpreted, the grid can be applied to plans such as the Vitruvian octagonal plan for an ideal city, resembling a spider web. These are all grids in that a regularly spaced armature leaves recurring openings and this intuitive explanation leaves the question of pre-grid and post grid non-rectilinear city patterns to be better understood, particularly those on plane territory such as Marrakech. Another potential influence may have been exerted by the second frequent user of city streets – horses, horses also tend to move in a straight line, particularly at trotting, canter or galloping pace. The need for speed is accentuated by city size, distances to the functions at the centre increase and, consequently. Speed in turn implies straight lines and it is plausible that the drivers for rectilinear layouts may have been mans horses, mules, and carts as much as man himself, spurred by the growth of settlements. Radburn now denotes a street network configuration and it signifies a departure from the strict orthogonal geometry and regularity of the grid and a distinct approach to laying out new districts. As a system, it can be described more accurately as a network that has a characteristic hierarchy of streets as distinct from identical streets intersecting at regular intervals. Its derivatives and idiosyncratic imitations are often characterized as cul-de-sac and loop patterns highlighting the distinguishing street types that are used systematically in this network, a second term equally uncharacteristic is suburban. Suburban is also devoid of geometric descriptors of the pattern and these shorthand expressions conceal the variety of patterns that emerged in the 20th century that are decidedly neither grids nor Radburn and the system aspect of the pattern. The patterns systematic use of the cul-de-sac and loop is decidedly linked to automotive mobility as a means of controlling and guiding its flow, the Radburn pattern is a complex system, more than a series of identical orthogonal city blocks in a linear progression. To facilitate the discussion, the name Radburn-like or Radburn-type will be used in the subsequent sections, the first known criticism of the grid was put forward on the grounds of defence that became irrelevant following the prevalence of the cannon
11.
Physical exercise
–
Physical exercise is any bodily activity that enhances or maintains physical fitness and overall health and wellness. Frequent and regular physical exercise boosts the immune system and helps prevent diseases of such as cardiovascular disease, type 2 diabetes. Childhood obesity is a global concern, and physical exercise may help decrease some of the effects of childhood. Some care providers call exercise the miracle or wonder drug—alluding to the variety of benefits that it can provide for many individuals. Aside from the advantages, these benefits may include different social rewards for staying active while enjoying the environment of one’s culture. Many individuals choose to exercise publicly outdoors where they can congregate in groups, socialize, in the United Kingdom two to four hours of light activity are recommended during working hours. The goal of aerobic exercise is to increase cardiovascular endurance, examples of aerobic exercise include cycling, swimming, brisk walking, skipping rope, rowing, hiking, playing tennis, continuous training, and long slow distance training. Anaerobic exercise, which includes strength and resistance training, can firm, strengthen, and tone muscles, as well as improve bone strength, balance, examples of strength moves are push-ups, pull-ups, lunges, and bicep curls using dumbbells. Anaerobic exercise also include training, functional training, eccentric training, Interval training, sprinting. Flexibility exercises stretch and lengthen muscles, activities such as stretching help to improve joint flexibility and keep muscles limber. The goal is to improve the range of motion which can reduce the chance of injury, Physical exercise can also include training that focuses on accuracy, agility, power, and speed. Sometimes the terms dynamic and static are used, dynamic exercises such as steady running, tend to produce a lowering of the diastolic blood pressure during exercise, due to the improved blood flow. Conversely, static exercise can cause the pressure to rise significantly. Some studies indicate that exercise may increase life expectancy and the quality of life. People who participate in moderate to high levels of exercise have a lower mortality rate compared to individuals who by comparison are not physically active. Moderate levels of exercise have been correlated with preventing aging by reducing inflammatory potential, the majority of the benefits from exercise are achieved with around 3500 metabolic equivalent minutes per week. A lack of physical activity causes approximately 6% of the burden of disease from coronary disease, 7% of type 2 diabetes, 10% of breast cancer. Overall, physical inactivity causes 9% of premature mortality worldwide, individuals can increase fitness following increases in physical activity levels
12.
Air pollution
–
Air pollution occurs when harmful substances including particulates and biological molecules are introduced into Earths atmosphere. It may cause diseases, allergies or death in humans, it may cause harm to other living organisms such as animals and food crops. Human activity and natural processes can both generate air pollution, indoor air pollution and poor urban air quality are listed as two of the worlds worst toxic pollution problems in the 2008 Blacksmith Institute Worlds Worst Polluted Places report. According to the 2014 WHO report, air pollution in 2012 caused the deaths of around 7 million people worldwide, an air pollutant is a substance in the air that can have adverse effects on humans and the ecosystem. The substance can be particles, liquid droplets, or gases. A pollutant can be of natural origin or man-made, pollutants are classified as primary or secondary. Primary pollutants are usually produced from a process, such as ash from a volcanic eruption, other examples include carbon monoxide gas from motor vehicle exhaust, or the sulfur dioxide released from factories. Secondary pollutants are not emitted directly, rather, they form in the air when primary pollutants react or interact. Ground level ozone is a prominent example of a secondary pollutant, some pollutants may be both primary and secondary, they are both emitted directly and formed from other primary pollutants. Substances emitted into the atmosphere by human activity include, Carbon dioxide - Debate continues over whether carbon dioxide should be classified as an atmospheric pollutant, because of its role as a greenhouse gas it has been described as the leading pollutant and the worst climate pollution. Against this it is argued that carbon dioxide is a component of the atmosphere, essential for plant life. This question of terminology has practical effects, for example as determining whether the U. S. Clean Air Act is deemed to regulate CO2 emissions, CO2 increase in earths atmosphere has been accelerating. Sulfur oxides - particularly sulfur dioxide, a compound with the formula SO2. SO2 is produced by volcanoes and in industrial processes. Coal and petroleum often contain sulfur compounds, and their combustion generates sulfur dioxide, further oxidation of SO2, usually in the presence of a catalyst such as NO2, forms H2SO4, and thus acid rain. This is one of the causes for concern over the impact of the use of these fuels as power sources. Nitrogen oxides - Nitrogen oxides, particularly nitrogen dioxide, are expelled from high temperature combustion and they can be seen as a brown haze dome above or a plume downwind of cities. Nitrogen dioxide is a compound with the formula NO2
