Instruct: Given a question, retrieve relevant passages that can help answer the question.
Query: What is the number one air pollutant?
The Air pollution is the release of chemicals and particulates into the atmosphere. Common gaseous pollutants include carbon monoxide, sulfur dioxide, chlorofluorocarbons (CFCs) and nitrogen oxides produced by industry and motor vehicles. Photochemical ozone and smog are created as nitrogen oxides and hydrocarbons react to sunlight. Particulate matter, or fine dust is characterized by their micrometre size PM to PM. The air in Karachi is rapidly polluted by automobile smoke, especially Rickshaws and Buses, industrial emissions, open burning of garbage, house fires, and other particles but the government and environment organizations seems non-serious to tackle the issue timely.
The two-stroke engines on rickshaws and motorcycles are one of the major polluters of air in Karachi and the rest of Pakistan. The two-stroke engines as well as defective or unturned vehicles are major polluters with carbon dioxide emissions. Two-stroke engines as well as defective vehicles using substandard lubricant are major emitters of sulfur dioxide and smoke. Automobiles operating on compressed natural gas and liquefied petroleum gas are major air polluters.
Air pollution, or suspended particulate matter locally generated from the increased number of automobiles in the area, from point sources such as factories, dust carried into the air by construction activity, and the contribution of similar pollutants from the Los Angeles area has regularly caused the Inland Empire to be at, or near, the bottom of many air quality ratings. In 2004, the EPA rated the San Bernardino-Riverside area as having the worst particulate air pollution in the United States (although the San Joaquin Valley in central California had the worst overall air pollution). Air pollution in the Los Angeles region is still an issue, although improvements have been made over the years. But the problem is exacerbated in the Inland Empire, which is surrounded by mountains on the north and the east. Prevailing winds move bad air eastward from Los Angeles, but once the pollution reaches the Inland Empire it cannot be carried further east as it becomes trapped by the mountains surrounding the region .
According to the American Lung Association's recent "State of the Air 2017" report, California is a leader in air pollution among other states, with the highest ozone levels. The top three cities in the country with the highest recorded levels of ozone (smog) levels were Los Angeles-Long Beach, Bakersfield, and Fresno-Madera. Salinas, California is the only city of California that reports no days of unhealthy air quality. While the air quality in California is significantly better in northern California, more than ninety percent of Californians live in counties with unhealthy air.
Many of the polycyclic aromatic hydrocarbons known to be tumorigenic or mutagenic are found in atmospheric aerosols, which is connected to the thermal rearrangement of polycyclic aromatic hydrocarbons in fast soot formation during combustion.
By 1964, the department had developed an AQI called the SCS Air Pollution Index (SCS API), combining measurements of sulfur dioxide (SO), carbon monoxide (CO), and coefficient of haze (also called smoke shade) into a single number. The city laboratory recorded the presence of those three pollutants measured in amount (by concentration in the air) and duration. SO and CO were measured by parts-per-million, or ppm, and smoke shade was measured in mppcf (millions of particles per cubic foot); the department continuously monitored these pollutant levels and recorded their hourly averages. The data for those three pollutants were combined into a single number using a weighted formula developed by department co-founder Moe Mordecai Braverman. The SCS API formula was:
Polycyclic aromatic hydrocarbons are primarily found in natural sources such as creosote. They can result from the incomplete combustion of organic matter. PAHs can also be produced geologically when organic sediments are chemically transformed into fossil fuels such as oil and coal. PAHs are considered ubiquitous in the environment and can be formed from either natural or manmade combustion sources. The dominant sources of PAHs in the environment are thus from human activity: wood-burning and combustion of other biofuels such as dung or crop residues contribute more than half of annual global PAH emissions, particularly due to biofuel use in India and China. As of 2004, industrial processes and the extraction and use of fossil fuels made up slightly more than one quarter of global PAH emissions, dominating outputs in industrial countries such as the United States. Wildfires are another notable source. Substantially higher outdoor air, soil, and water concentrations of PAHs have been measured in Asia, Africa, and Latin America than in Europe, Australia, the U.S., and Canada.
Polycyclic aromatic hydrocarbons (PAHs) are aromatic hydrocarbons that consist of fused aromatic rings and do not contain heteroatoms or carry substituents. Naphthalene is the simplest example of a PAH. PAHs occur in oil, coal, and tar deposits, and are produced as byproducts of fuel burning (whether fossil fuel or biomass). As pollutants, they are of concern because some compounds have been identified as carcinogenic, mutagenic, and teratogenic. PAHs are also found in cooked foods. Studies have shown that high levels of PAHs are found, for example, in meat cooked at high temperatures such as grilling or barbecuing, and in smoked fish.
Although diesel locomotives generally emit less sulphur dioxide, a major pollutant to the environment, and greenhouse gases than steam locomotives, they are not completely clean in that respect. Furthermore, like other diesel powered vehicles, they emit nitrogen oxides and fine particles, which are a risk to public health. In fact, in this last respect diesel locomotives may perform worse than steam locomotives.
According to the European Cities Monitor 2010, Stockholm is the best city in terms of freedom from pollution. Surrounded by 219 nature reserves, Stockholm has around 1,000 green spaces, which corresponds to 30% of the city's area. Founded in 1995, the Royal National City Park is the world's first legally protected "national urban park". For a description of the formation process, value assets and implementation of the legal protection of The Royal National Urban Park, see Schantz 2006 The water in Stockholm is so clean that people can dive and fish in the centre of the city. In fact the waters of downtown Stockholm serve as spawning grounds for multiple fish species including trout and salmon. Regarding CO2 emissions, the government's target is that Stockholm will be CO2 free before 2050.
An aerosol is a suspension of fine solid particles or liquid droplets, in air or another gas. Aerosols can be natural or anthropogenic. Examples of natural aerosols are fog, dust, forest exudates and geyser steam. Examples of anthropogenic aerosols are haze, particulate air pollutants and The liquid or solid particles have diameters typically <1 μm; larger particles with a significant settling speed make the mixture a suspension, but the distinction is not clear-cut. In general conversation, "aerosol" usually refers to an aerosol spray that delivers a consumer product from a can or similar container. Other technological applications of aerosols include dispersal of pesticides, medical treatment of respiratory illnesses, and convincing technology. Diseases can also spread by means of small droplets in the breath, also called aerosols (or sometimes bioaerosols).
Organophosphate pesticides are one of the top causes of poisoning worldwide, with an annual incidence of poisonings among agricultural workers varying from 3-10% per country.
Common plants used to remediate indoor air pollutants include: English ivy ("Hedera helix"), Peace lily ("Spathiphyllum ‘Mauna Loa’"), Chinese evergreen ("Aglaonema modestum"), Bamboo palm ("Chamaedorea seifrizii"), and Chrysanthemum ("Chrysanthemum morifolium"). There are several studies that cite the plant microcosm as a mechanism to reduce indoor VOCs. Controls of just pots alone and just a tray of water suggest that it is the soil microcosm that provides the pollutant sink. The role of the plants is to establish and maintain the species specific root-zone microbial communities. This mechanism was first suggested by Wolverton et al. in 1985. Houseplants also aid in humidity, temperature, and noise control.
Many cellulosic biomass materials produce methane naturally. Methane is the main component of natural gas. Naturally occurring methane is often considered a source of pollution from landfills, dairy farms, and human waste sources. The EPA routinely issues rules to reduce the emission of methane from landfills and other sources.
On September 11, 2001, 19 terrorists associated with the Islamist militant group al-Qaeda hijacked four passenger jets in a series of suicide attacks on the United States, killing 2,996 people and injuring more than 6,000 others. Hijackers flew planes into two main towers of the World Trade Center, resulting in the collapse of three buildings of the World Trade Center complex, and the Pentagon, resulting in the partial destruction of the western side in the building. The resulting dust cloud due to the collapse of the World Trade Center covered Manhattan for days and contained thousands of tons of toxic debris, including asbestos and other known carcinogens. Another hijacked plane crashed into a field in Shanksville, Pennsylvania following an attempt by the passengers to retake control of the plane. No one in the airliners survived.
As of 2011, approximately 18,000 people have received medical treatment for illnesses related to toxic dust from the World Trade Center site. A study of rescue workers released in April 2010 found that all those studied had impaired lung functions, and that 30–40% were reporting little or no improvement in persistent symptoms that started within the first year of the attack. In 2011 a major research study showed significant long term medical and psychological effects among first responders to the World Trade Center site. These effects include elevated levels of asthma, sinusitis, Gastroesophageal reflux disease and posttraumatic stress disorder.
, medical authorities concluded that 1,140 people who worked, lived, or studied in Lower Manhattan at the time of the attack have been diagnosed with cancer as a result of "exposure to toxins at Ground Zero". It has been reported that over 1,400 9/11 rescue workers who responded to the scene in the days and months after the attacks have since died. At least 11 pregnancies were lost as a result of 9/11.
Catalytic combustion is a chemical process which uses a catalyst to speed desired oxidation reactions of a fuel and so reduce the formation of undesired products, especially pollutant nitrogen oxide gases (NO) far below what can be achieved without catalysts. The process was discovered in the 1970s at Engelhard Corp.
Polycyclic aromatic hydrocarbons (PAHs, also polyaromatic hydrocarbons or polynuclear aromatic hydrocarbons) are hydrocarbons—organic compounds containing only carbon and hydrogen—that are composed of multiple aromatic rings (organic rings in which the electrons are delocalized). The simplest such chemicals are naphthalene, having two aromatic rings, and the three-ring compounds anthracene and phenanthrene.
The common allotrope of elemental oxygen on Earth, , is generally known as oxygen, but may be called "dioxygen", "diatomic oxygen", "molecular oxygen", or "oxygen gas" to distinguish it from the element itself and from the triatomic allotrope "ozone," . As a major component (about 21% by volume) of Earth's atmosphere, elemental oxygen is most commonly encountered in the diatomic form. Aerobic organisms utilize atmospheric dioxygen as the terminal oxidant in cellular respiration. The ground state of dioxygen is known as triplet oxygen, O, because it has two unpaired electrons. The first excited state, singlet oxygen, ""O has no unpaired electrons and is metastable.
The amount of oxygen in the atmosphere has fluctuated over the last 600 million years, reaching a peak of about 30% around 280 million years ago, significantly higher than today's 21%. Two main processes govern changes in the atmosphere: Plants use carbon dioxide from the atmosphere, releasing oxygen. Breakdown of pyrite and volcanic eruptions release sulfur into the atmosphere, which oxidizes and hence reduces the amount of oxygen in the atmosphere. However, volcanic eruptions also release carbon dioxide, which plants can convert to oxygen. The exact cause of the variation of the amount of oxygen in the atmosphere is not known. Periods with much oxygen in the atmosphere are associated with rapid development of animals. Today's atmosphere contains 21% oxygen, which is great enough for this rapid development of animals.
Many studies have shown that painting is what generates almost half dangerous waste at a shipyard due to using high-pressure equipment to wash or remove any unwanted material that is on it like rust. Which will eventually make its way to the water and creates water pollution to the environment. Once these have compromised the surface of the hull the ship must go to the shipyard for maintenance. In a study in 2011 samples of sediments were collected from two sites in coastal marine area of Yongho Bay, one from the shipyard yard and the other 500m away. These results had analyzed that both samples contained metals that included Al, Fe, Li, V, Cr, Mn, Ni, Cu, Zn, As, Cd, Sn, and Pb. In addition, it had been confirmed that the concentration was higher in the first sample that was by the shipyard then the sample taking 500m away and was due to paint fragments applied to the steel ship hulls.
Aerosol mass spectrometry is the application of mass spectrometry to aerosol particles. Aerosol particles are defined as solid and liquid particles suspended in a gas (air), with size range of 3 nm to 100 μm in diameter. Aerosol particles are produced from natural and anthropogenic sources, through a variety of different processes that include; wind-blown suspension, and combustion of fossil fuels and biomass. Analysis of aerosol particles is important because of their major impacts on the global climate change, visibility, regional air pollution and human health. Aerosol particles are very complex in structure and can contain thousands of different chemical compounds within a single particle. Due to this complexity the instrumentation used to analysis these particles must have the ability to separate based on size and in real-time provide information on their chemical composition. To meet these requirements for analysis, mass spectrometry instrumentation is used and they provide high sensitivity and the ability to detect a wide molecular mass range. Aerosol mass spectrometry can be divided into two categorizes; off-line and on-line. Off-line mass spectrometry is performed on collected particles. On-line mass spectrometry is performed on particles introduced in real time.
Air quality regulation must identify the substances and energies which qualify as "pollution" for purposes of further control. While specific labels vary from jurisdiction to jurisdiction, there is broad consensus among many governments regarding what constitutes air pollution. For example, the United States Clean Air Act identifies ozone, particulate matter, carbon monoxide, nitrogen oxides (NO), sulfur dioxide (SO), and lead (Pb) as "criteria" pollutants requiring nationwide regulation. EPA has also identified over 180 compounds it has classified as "hazardous" pollutants requiring strict control. Other compounds have been identified as air pollutants due to their adverse impact on the environment (e.g., CFCs as agents of ozone depletion), and on human health (e.g., asbestos in indoor air). A broader conception of air pollution may also incorporate noise, light, and radiation. The United States has recently seen controversy over whether carbon dioxide (CO) and other greenhouse gases should be classified as air pollutants.
While transnational pollution between the United States and Canada has decreased many Canadians still say they contend with polluted air as a result of drifting pollution from the U.S. In 2006 the government of Ontario announced that "5,000 premature deaths caused by smog in the province every year can be attributed to air pollution that crosses the Canada-U.S. border." Additionally, the then (2006) mayor of Halifax, Peter Kelley, also proclaimed "over 50 per cent of air pollutants over New Brunswick and Nova Scotia are from the U.S. For us, we're trying to deal with what's coming our way, but also what we generate here as well." In an attempt to combat the pollution a petition was created. In 2006 the petition was filed by thirteen Canadian municipalities to the U.S. Environmental Protection Agency calling for a reduction in coal-fired plants.
The AP 42 Compilation of Air Pollutant Emission Factors is a compilation of emission factors of air pollutants, in other words numbers which relate the quantity of a pollutant released into the ambient air with a certain activity. This compilation was first compiled and published by the US Public Health Service in 1968. In 1972, it was revised and issued as the second edition by the US Environmental Protection Agency EPA. 
In 1985, the subsequent fourth edition was split into two volumes: Volume I has since included stationary point and area source emission factors, and Volume II includes mobile source emission factors. Volume I is currently in its fifth edition and is available on the Internet. 
Volume II is no longer maintained as such, but roadway air dispersion models for estimating emissions from onroad vehicles and from non-road vehicles and mobile equipment are available on the Internet.
Toxic air pollutants are the suspected cause of major illnesses and issues with reproductive problems. These pollutants stay in the environment for long periods, which can affect all living things and start a chain of negative events. In particular, smokestacks and automobiles are the two main sources of toxic air pollutants. When refueling, the gases turn into vapor that leak into the air. "Before the 1990 Clean Air Act Amendments, EPA regulated air toxics one chemical at a time." The EPA now regulates pollutants by categories of industries because they release more than one chemical at a time. Some of the categories are, chemical plants, incinerators, dry cleaners, and manufacturers of wood furniture. Since the 1990 Clean Air Act, air toxics from large industries have already been reduced by 70 percent.