Indoor air quality
Indoor air quality is the air quality within and around buildings and structures. IAQ is known to affect the health and well-being of building occupants. Poor indoor air quality has been linked to Sick Building Syndrome, reduced productivity and impaired learning in schools. IAQ can be affected by gases, microbial contaminants, or any mass or energy stressor that can induce adverse health conditions. Source control and the use of ventilation to dilute contaminants are the primary methods for improving indoor air quality in most buildings. Residential units can further improve indoor air quality by routine cleaning of carpets and area rugs. Determination of IAQ involves the collection of air samples, monitoring human exposure to pollutants, collection of samples on building surfaces, computer modelling of air flow inside buildings. IAQ is part of indoor environmental quality, which includes IAQ as well as other physical and psychological aspects of life indoors. Indoor air pollution in developing nations is a major health hazard.
A major source of indoor air pollution in developing countries is the burning of biomass for heating and cooking. The resulting exposure to high levels of particulate matter resulted in between 1.5 million and 2 million deaths in 2000. Second-hand smoke is tobacco smoke. Second-hand tobacco smoke includes both a gaseous and a particulate phase, with particular hazards arising from levels of carbon monoxide and small particulates which get into the bronchioles and alveoles in the lung; the only certain method to improve indoor air quality as regards second-hand smoke is to eliminate smoking indoors. Radon is an invisible, radioactive atomic gas that results from the radioactive decay of radium, which may be found in rock formations beneath buildings or in certain building materials themselves. Radon is the most pervasive serious hazard for indoor air in the United States and Europe, is responsible for tens of thousands of deaths from lung cancer each year. There are simple test kits for do-it-yourself radon gas testing, but if a home is for sale the testing must be done by a licensed person in some U.
S. states. Radon gas enters buildings as a soil gas and is a heavy gas and thus will tend to accumulate at the lowest level. Radon may be introduced into a building through drinking water from bathroom showers. Building materials can be a rare source of radon, but little testing is carried out for stone, rock or tile products brought into building sites; the half life for radon is 3.8 days, indicating that once the source is removed, the hazard will be reduced within a few weeks. Radon mitigation methods include sealing concrete slab floors, basement foundations, water drainage systems, or by increasing ventilation, they are cost effective and can reduce or eliminate the contamination and the associated health risks. Radon is measured in picocuries per liter of a measurement of radioactivity. In the United States, the average indoor radon level is about 1.3 pCi/L. The average outdoor level is about 0.4 pCi/L. The U. S. Surgeon General and EPA recommend fixing homes with radon levels at or above 4 pCi/L.
EPA recommends that people think about fixing their homes for radon levels between 2 pCi/L and 4 pCi/L. These biological chemicals can arise from a host of means, but there are two common classes: moisture induced growth of mold colonies and natural substances released into the air such as animal dander and plant pollen. Mold is always associated with moisture, its growth can be inhibited by keeping humidity levels below 50%. Moisture buildup inside buildings may arise from water penetrating compromised areas of the building envelope or skin, from plumbing leaks, from condensation due to improper ventilation, or from ground moisture penetrating a building part. Something as simple as drying clothes indoors on radiators can increase the risk of exposure to Aspergillus - a dangerous mould that can be fatal for asthma sufferers and the elderly. In areas where cellulosic materials become moist and fail to dry within 48 hours, mold mildew can propagate and release allergenic spores into the air.
In many cases, if materials have failed to dry out several days after the suspected water event, mold growth is suspected within wall cavities if it is not visible. Through a mold investigation, which may include destructive inspection, one should be able to determine the presence or absence of mold. In a situation where there is visible mold and the indoor air quality may have been compromised, mold remediation may be needed. Mold testing and inspections should be carried out by an independent investigator to avoid any conflict of interest and to insure accurate results. There are some varieties of mold. However, exposure to hazardous levels of mycotoxin via inhalation is not possible in most cases, as toxins are produced by the fungal body and are not at significant levels in the released spores; the primary hazard of mold growth, as it relates to indoor air quality, comes from the allergenic properties of the spore cell wall. More serious than most allergenic properties is the ability of mold to trigger episodes in persons that have asth
Eutrophication, or hypertrophication, is when a body of water becomes overly enriched with minerals and nutrients which induce excessive growth of plants and algae. This process may result in oxygen depletion of the water body. One example is an "algal bloom" or great increase of phytoplankton in a water body as a response to increased levels of nutrients. Eutrophication is induced by the discharge of nitrate or phosphate-containing detergents, fertilizers, or sewage into an aquatic system. Eutrophication most arises from the oversupply of nutrients, most as nitrogen or phosphorus, which leads to overgrowth of plants and algae in aquatic ecosystems. After such organisms die, bacterial degradation of their biomass results in oxygen consumption, thereby creating the state of hypoxia. According to Ullmann's Encyclopedia, "the primary limiting factor for eutrophication is phosphate." The availability of phosphorus promotes excessive plant growth and decay, favouring simple algae and plankton over other more complicated plants, causes a severe reduction in water quality.
Phosphorus is a necessary nutrient for plants to live, is the limiting factor for plant growth in many freshwater ecosystems. Phosphate adheres to soil, so it is transported by erosion. Once translocated to lakes, the extraction of phosphate into water is slow, hence the difficulty of reversing the effects of eutrophication. However, numerous literature report that nitrogen is the primary limiting nutrient for the accumulation of algal biomass; the sources of these excess phosphates are phosphates in detergent, industrial/domestic run-offs, fertilizers. With the phasing out of phosphate-containing detergents in the 1970s, industrial/domestic run-off and agriculture have emerged as the dominant contributors to eutrophication. Cultural eutrophication is the process that speeds up natural eutrophication because of human activity. Due to clearing of land and building of towns and cities, land runoff is accelerated and more nutrients such as phosphates and nitrate are supplied to lakes and rivers, to coastal estuaries and bays.
Extra nutrients are supplied by treatment plants, golf courses, farms, as well as untreated sewage in many countries. When algae die, they decompose and the nutrients contained in that organic matter are converted into inorganic form by microorganisms; this decomposition process consumes oxygen. The depleted oxygen levels in turn may lead to fish kills and a range of other effects reducing biodiversity. Nutrients may become concentrated in an anoxic zone and may only be made available again during autumn turn-over or in conditions of turbulent flow; the dead algae and the organic load carried by the water inflows in to the lake settle at its bottom and undergoes anaerobic digestion releasing greenhouse gases like methane and CO2. Some part of methane gas is consumed by the anaerobic methane oxidation bacteria which in turn works as food source to the zooplankton. In case the lake is not deficit of dissolved oxygen at all depths the aerobic methane oxidation bacteria like Methylococcus capsulatus can consume most of the methane by releasing CO2 which in turn aid the production of algae.
Thus a self-sustaining biological process can take place to generate primary food source for the phytoplankton and zooplankton depending on availability of adequate dissolved oxygen in the water bodies which are subjected to higher organic pollution loads. Adequate dissolved oxygen in water bodies is crucial for fisheries production and elimination of green house gas emissions. Enhanced growth of aquatic vegetation or phytoplankton and algal blooms disrupts normal functioning of the ecosystem, causing a variety of problems such as a lack of oxygen needed for fish and shellfish to survive; the water becomes cloudy coloured a shade of green, brown, or red. Eutrophication decreases the value of rivers and aesthetic enjoyment. Health problems can occur. Human activities can accelerate the rate. Runoff from agriculture and development, pollution from septic systems and sewers, sewage sludge spreading, other human-related activities increase the flow of both inorganic nutrients and organic substances into ecosystems.
Elevated levels of atmospheric compounds of nitrogen can increase nitrogen availability. Phosphorus is regarded as the main culprit in cases of eutrophication in lakes subjected to "point source" pollution from sewage pipes; the concentration of algae and the trophic state of lakes correspond well to phosphorus levels in water. Studies conducted in the Experimental Lakes Area in Ontario have shown a relationship between the addition of phosphorus and the rate of eutrophication. Humankind has increased the rate of phosphorus cycling on Earth by four times due to agricultural fertilizer production and application. Between 1950 and 1995, an estimated 600,000,000 tonnes of phosphorus was applied to Earth's surface on croplands. Although eutrophication is caused by human activities, it can be a natural process in lakes. Eutrophy occurs for instance. Paleolimnologists now recognise that climate change and other external influences are critical in regulating the natural productivity of lakes; some lakes demonstrate the reverse process, becoming less nutrient rich with time.
The main difference between natural and anthropogenic eutrophication is that the natural process is slow, occurring on geological time scales. Eutrophication is a common phenomenon i
Pesticides are substances that are meant to control pests, including weeds. The term pesticide includes all of the following: herbicide, insecticides nematicide, piscicide, rodenticide, insect repellent, animal repellent and fungicide; the most common of these are herbicides which account for 80% of all pesticide use. Most pesticides are intended to serve as plant protection products, which in general, protect plants from weeds, fungi, or insects. In general, a pesticide is a chemical or biological agent that deters, kills, or otherwise discourages pests. Target pests can include insects, plant pathogens, molluscs, mammals, fish and microbes that destroy property, cause nuisance, or spread disease, or are disease vectors. Along with these benefits, pesticides have drawbacks, such as potential toxicity to humans and other species; the Food and Agriculture Organization has defined pesticide as: any substance or mixture of substances intended for preventing, destroying, or controlling any pest, including vectors of human or animal disease, unwanted species of plants or animals, causing harm during or otherwise interfering with the production, storage, transport, or marketing of food, agricultural commodities and wood products or animal feedstuffs, or substances that may be administered to animals for the control of insects, arachnids, or other pests in or on their bodies.
The term includes substances intended for use as a plant growth regulator, desiccant, or agent for thinning fruit or preventing the premature fall of fruit. Used as substances applied to crops either before or after harvest to protect the commodity from deterioration during storage and transport. Pesticides can be classified by target organism, chemical structure, physical state. Biopesticides include biochemical pesticides. Plant-derived pesticides, or "botanicals", have been developing quickly; these include the pyrethroids, nicotinoids, a fourth group that includes strychnine and scilliroside. Many pesticides can be grouped into chemical families. Prominent insecticide families include organochlorines and carbamates. Organochlorine hydrocarbons could be separated into dichlorodiphenylethanes, cyclodiene compounds, other related compounds, they operate by disrupting the sodium/potassium balance of the nerve fiber, forcing the nerve to transmit continuously. Their toxicities vary but they have been phased out because of their persistence and potential to bioaccumulate.
Organophosphate and carbamates replaced organochlorines. Both operate through inhibiting the enzyme acetylcholinesterase, allowing acetylcholine to transfer nerve impulses indefinitely and causing a variety of symptoms such as weakness or paralysis. Organophosphates are quite toxic to vertebrates and have in some cases been replaced by less toxic carbamates. Thiocarbamate and dithiocarbamates are subclasses of carbamates. Prominent families of herbicides include phenoxy and benzoic acid herbicides, triazines and Chloroacetanilides. Phenoxy compounds tend to selectively kill broad-leaf weeds rather than grasses; the phenoxy and benzoic acid herbicides function similar to plant growth hormones, grow cells without normal cell division, crushing the plant's nutrient transport system. Triazines interfere with photosynthesis. Many used pesticides are not included in these families, including glyphosate; the application of pest control agents is carried out by dispersing the chemical in a solvent-surfactant system to give a homogeneous preparation.
A virus lethality study performed in 1977 demonstrated that a particular pesticide did not increase the lethality of the virus, however combinations which included some surfactants and the solvent showed that pretreatment with them markedly increased the viral lethality in the test mice. Pesticides can be classified based upon their biological mechanism application method. Most pesticides work by poisoning pests. A systemic pesticide moves inside a plant following absorption by the plant. With insecticides and most fungicides, this movement is upward and outward. Increased efficiency may be a result. Systemic insecticides, which poison pollen and nectar in the flowers, may kill bees and other needed pollinators. In 2010, the development of a new class of fungicides called; these work by taking advantage of natural defense chemicals released by plants called phytoalexins, which fungi detoxify using enzymes. The paldoxins inhibit the fungi's detoxification enzymes, they are believed to be greener.
Since before 2000 BC, humans have utilized pesticides to protect their crops. The first known pesticide was elemental sulfur dusting used in ancient Sumer about 4,500 years ago in ancient Mesopotamia; the Rig Veda, about 4,000 years old, mentions the use of poisonous plants for pest control. By the 15th century, toxic chemicals such as arsenic and lead were being applied to crops to kill pests. In the 17th century, nicotine sulfate was extracted from tobacco leaves for use as an insecticide; the 19th century saw the introduction of two more natural pesticides, derived fr
A wetland is a distinct ecosystem, inundated by water, either permanently or seasonally, where oxygen-free processes prevail. The primary factor that distinguishes wetlands from other land forms or water bodies is the characteristic vegetation of aquatic plants, adapted to the unique hydric soil. Wetlands play a number of functions, including water purification, water storage, processing of carbon and other nutrients, stabilization of shorelines, support of plants and animals. Wetlands are considered the most biologically diverse of all ecosystems, serving as home to a wide range of plant and animal life. Whether any individual wetland performs these functions, the degree to which it performs them, depends on characteristics of that wetland and the lands and waters near it. Methods for assessing these functions, wetland ecological health, general wetland condition have been developed in many regions and have contributed to wetland conservation by raising public awareness of the functions and the ecosystem services some wetlands provide.
Wetlands occur on every continent. The main wetland types are swamp, marsh and fen. Many peatlands are wetlands; the water in wetlands is either brackish, or saltwater. Wetlands can be non-tidal; the largest wetlands include the Amazon River basin, the West Siberian Plain, the Pantanal in South America, the Sundarbans in the Ganges-Brahmaputra delta. The UN Millennium Ecosystem Assessment determined that environmental degradation is more prominent within wetland systems than any other ecosystem on Earth. Constructed wetlands are used to treat municipal and industrial wastewater as well as stormwater runoff, they may play a role in water-sensitive urban design. A patch of land that develops pools of water after a rain storm would not be considered a "wetland" though the land is wet. Wetlands have unique characteristics: they are distinguished from other water bodies or landforms based on their water level and on the types of plants that live within them. Wetlands are characterized as having a water table that stands at or near the land surface for a long enough period each year to support aquatic plants.
A more concise definition is a community composed of hydric soil and hydrophytes. Wetlands have been described as ecotones, providing a transition between dry land and water bodies. Mitsch and Gosselink write that wetlands exist "...at the interface between terrestrial ecosystems and aquatic systems, making them inherently different from each other, yet dependent on both."In environmental decision-making, there are subsets of definitions that are agreed upon to make regulatory and policy decisions. A wetland is "an ecosystem that arises when inundation by water produces soils dominated by anaerobic and aerobic processes, which, in turn, forces the biota rooted plants, to adapt to flooding." There are four main kinds of wetlands – marsh, swamp and fen. Some experts recognize wet meadows and aquatic ecosystems as additional wetland types; the largest wetlands in the world include the swamp forests of the Amazon and the peatlands of Siberia. Under the Ramsar international wetland conservation treaty, wetlands are defined as follows: Article 1.1: "...wetlands are areas of marsh, peatland or water, whether natural or artificial, permanent or temporary, with water, static or flowing, brackish or salt, including areas of marine water the depth of which at low tide does not exceed six metres."
Article 2.1: " may incorporate riparian and coastal zones adjacent to the wetlands, islands or bodies of marine water deeper than six metres at low tide lying within the wetlands." Although the general definition given above applies around the world, each county and region tends to have its own definition for legal purposes. In the United States, wetlands are defined as "those areas that are inundated or saturated by surface or groundwater at a frequency and duration sufficient to support, that under normal circumstances do support, a prevalence of vegetation adapted for life in saturated soil conditions. Wetlands include swamps, marshes and similar areas"; this definition has been used in the enforcement of the Clean Water Act. Some US states, such as Massachusetts and New York, have separate definitions that may differ from the federal government's. In the United States Code, the term wetland is defined "as land that has a predominance of hydric soils, is inundated or saturated by surface or groundwater at a frequency and duration sufficient to support a prevalence of hydrophytic vegetation adapted for life in saturated soil conditions and under normal circumstances supports a prevalence of such vegetation."
Related to this legal definitions, the term "normal circumstances" are conditions expected to occur during the wet portion of the growing season under normal climatic conditions, in the absence of significant disturbance. It is not uncommon for a wetland to be dry for long portions of the growing season. Wetlands can be dry during the dry season and abnormally dry periods during the wet season, but under normal environmental conditions the soils in a wetland will be saturated to the surface or inundated such that the soils become anaerobic, those conditions will persist through the wet portion of the growing season; the most important factor producing wetlands is flooding. The duration of flooding or prolonged soil saturation by groundwater determines whether the resulting wetland has aquatic, marsh or swamp vegetation
Food and Agriculture Organization
The Food and Agriculture Organization of the United Nations is a specialized agency of the United Nations that leads international efforts to defeat hunger. Serving both developed and developing countries, FAO acts as a neutral forum where all nations meet as equals to negotiate arguments and debate policy. FAO is a source of knowledge and information, helps developing countries in transition modernize and improve agriculture and fisheries practices, ensuring good nutrition and food security for all, its Latin motto, fiat panis, translates as "let there be bread". As of August 2018, The FAO has 197 member states, including the European Union and The Cook Islands, the Faroe Islands and Tokelau, which are associate members; the idea of an international organization for food and agriculture emerged in the late 19th and early 20th century advanced by the US agriculturalist and activist David Lubin. In May–June 1905, an international conference was held in Rome, which led to the creation of the International Institute of Agriculture by the King of Italy Victor Emmanuel III.
In 1943, the United States President Franklin D. Roosevelt called a United Nations Conference on Food and Agriculture. Representatives from forty-four governments gathered at The Homestead Resort in Hot Springs, Virginia, US, from 18 May to 3 June, they committed themselves to founding a permanent organization for food and agriculture, which happened in Quebec City, Canada, on 16 October 1945 with the conclusion of the Constitution of the Food and Agriculture Organization. The First Session of the FAO Conference was held in the Château Frontenac in Quebec City from 16 October to 1 November 1945. World War II ended the International Agricultural Institute, though it was only dissolved by resolution of its Permanent Committee on 27 February 1948, its functions were transferred to the established FAO. From the late 1940s on, FAO attempted to make its mark within the emerging UN system, focusing on supporting agricultural and nutrition research and providing technical assistance to member countries to boost production in agriculture and forestry.
During the 1950s and 1960s, FAO partnered with many different international organizations in development projects. In 1951, FAO's headquarters were moved from DC, United States, to Rome, Italy; the agency is directed by the Conference of Member Nations, which meets every two years to review the work carried out by the organization and to Work and Budget for the next two-year period. The Conference elects a council of 49 member states that acts as an interim governing body, the Director-General, that heads the agency. FAO is composed of eight departments: Agriculture and Consumer Protection, Biodiversity and Water Department and Social Development and Aquaculture, Corporate Services and Technical Cooperation and Programme Management. Beginning in 1994, FAO underwent the most significant restructuring since its founding, to decentralize operations, streamline procedures and reduce costs; as a result, savings of about US$50 million, €35 million a year were realized. FAO's Regular Programme budget is funded by its members, through contributions set at the FAO Conference.
This budget covers core technical work and partnerships including the Technical Cooperation Programme, knowledge exchange and advocacy, direction and administration and security. The total FAO Budget planned for 2016–2017 is USD 2.6 billion. The voluntary contributions provided by members and other partners support mechanical and emergency assistance to governments for defined purposes linked to the results framework, as well as direct support to FAO's core work; the voluntary contributions are expected to reach US$1.6 billion in 2016–2017. This overall budget covers core technical work and partnerships, leading to Food and Agriculture Outcomes at 71 per cent; the world headquarters are located in Rome, in the former seat of the Department of Italian East Africa. One of the most notable features of the building was the Axum Obelisk which stood in front of the agency seat, although just outside the territory allocated to FAO by the Italian Government, it was taken from Ethiopia by Benito Mussolini's troops in 1937 as a war chest, returned on 18 April 2005.
Regional Office for Africa, in Accra, Ghana Regional Office for Asia and the Pacific, in Bangkok, Thailand Regional Office for Europe and Central Asia, in Budapest, Hungary Regional Office for Latin America and the Caribbean, in Santiago, Chile Regional Office for the Near East, in Cairo, Egypt Sub-regional Office for Central Africa, in Libreville, Gabon Sub-regional Office for Central Asia, in Ankara, Turkey Sub-regional Office for Eastern Africa, in Addis Ababa, Ethiopia Sub-regional Office for Mesoamerica, in Panama City, Panama Sub-regional Office for North Africa, in Tunis, Tunisia Sub-regional Office for Southern Africa and East Africa, in Harare, Zimbabwe Sub-regional Office for the Caribbean, in Bridgetown, Barbados Sub-regional Office for the Gulf Cooperation Council States and Yemen, Abu Dhabi Sub-regional Office for the Pacific Islands, in Apia, Samoa Liaison Office for North America, in Washington, DC Liaison Office with J
SahysMod is a computer program for the prediction of the salinity of soil moisture and drainage water, the depth of the watertable, the drain discharge in irrigated agricultural lands, using different hydrogeologic and aquifer conditions, varying water management options, including the use of ground water for irrigation, several crop rotation schedules, whereby the spatial variations are accounted for through a network of polygons. Application references: There is a need for a computer program, easier to operate and that requires a simpler data structure most available models. Therefore, the SahysMod program was designed keeping in mind a relative simplicity of operation to facilitate the use by field technicians and project planners instead of specialized geo-hydrologists, it aims at using input data that are available, or that can be estimated with reasonable accuracy, or that can be measured with relative ease. Although the calculations are done numerically and have to be repeated many times, the final results can be checked by hand using the formulas in this manual.
SahysMod's objective is to predict the long-term hydro-salinity in terms of general trends, not to arrive at exact predictions of how, for example, the situation would be on the first of April in ten years from now. Further, SahysMod gives the option of the re-use of drainage and well water and it can account for farmers' responses to waterlogging, soil salinity, water scarcity and over-pumping from the aquifer, it offers the possibility to introduce subsurface drainage systems at varying depths and with varying capacities so that they can be optimized. Other features of SahysMod are found in the next section; the model calculates the ground water levels and the incoming and outgoing ground water flows between the polygons by a numerical solution of the well-known Boussinesq equation. The levels and flows influence each other mutually; the ground water situation is further determined by the vertical groundwater recharge, calculated from the agronomic water balance. These depend again on the levels of the ground water.
When semi-confined aquifers are present, the resistance to vertical flow in the permeable top-layer and the overpressure in the aquifer, if any, are taken into account. Hydraulic boundary conditions are given as hydraulic heads in the external nodes in combination with the hydraulic conductivity between internal and external nodes. If one wishes to impose a zero flow condition at the external nodes, the conductivity can be set at zero. Further, aquifer flow conditions can be given for the internal nodes; these are required when a geological fault is present at the bottom of the aquifer or when flow occurs between the main aquifer and a deeper aquifer separated by a semi-confining layer. The depth of the water table, the rainfall and salt concentrations of the deeper layers are assumed to be the same over the whole polygon. Other parameters can within the polygons according to type of crops and cropping rotation schedule; the model returns seasonal outputs. The number of seasons per year can be chosen between a maximum of four.
One can distinguish for example dry, cold, irrigation or fallow seasons. Reasons of not using smaller input/output periods are: short-term inputs would require much information, which, in large areas, may not be available. For example, it need not be a major constraint to the design of appropriate soil salinity control measures when a certain salinity level, predicted by SahysMod to occur after 20 years, will in reality occur after 15 or 25 years. Many water balance factors depend on the level of the water table, which again depends on some of the water-balance factors. Due to these mutual influences there can be non-linear changes throughout the season. Therefore, the computer program performs daily calculations. For this purpose, the seasonal water-balance factors given with the inpu] are reduced automatically to daily values; the calculated seasonal water-balance factors, as given in the output, are obtained by summations of the daily calculated values. Groundwater levels and soil salinity at the end of the season are found by accumulating the daily changes of water and salt storage.
In some cases the program may detect that the time step must be taken less than 1 day for better accuracy. The necessary adjustments are made automatically; the model permits a maximum of 240 internal and 120 external polygons with a minimum of 3 and a maximum of 6 sides each. The subdivision of the area into polygons, based on nodal points with known coordinates, should be governed by the characteristics of the distribution of the cropping, irrigation and groundwater characteristics over the study area; the nodes must be numbered. With an index one indicates whether the node is external. Nodes can be changed from internal to external or vice versa. Through another index one indicates whether the internal nodes have an unconfined or semi-confined aquifer; this can be changed at will. Nodal network relations are to be given indicating the neighboring polygon numbers of each node; the program calculates the surface area of each polygon, the distance be
Air pollution occurs when harmful or excessive quantities of substances including gases and biological molecules are introduced into Earth's atmosphere. It may cause diseases and death to humans. Both human activity and natural processes can generate air pollution. Indoor air pollution and poor urban air quality are listed as two of the world's worst toxic pollution problems in the 2008 Blacksmith Institute World's Worst Polluted Places report. According to the 2014 World Health Organization report, air pollution in 2012 caused the deaths of around 7 million people worldwide, an estimate echoed by one from the International Energy Agency. An air pollutant is a material in the air that can have adverse effects on the ecosystem; the substance can be liquid droplets, or gases. A pollutant can be of man-made. Pollutants are classified as secondary. Primary pollutants are produced by processes such as ash from a volcanic eruption. Other examples include carbon monoxide gas from motor vehicle exhausts or sulphur dioxide released from the factories.
Secondary pollutants are not emitted directly. Rather, they form in the air when primary pollutants interact. Ground level ozone is a prominent example of secondary pollutants; 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 – Because of its role as a greenhouse gas it has been described as "the leading pollutant" and "the worst climate pollution". Carbon dioxide is a natural component of the atmosphere, essential for plant life and given off by the human respiratory system; 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 forms about 410 parts per million of earth's atmosphere, compared to about 280 ppm in pre-industrial times, billions of metric tons of CO2 are emitted annually by burning of fossil fuels. CO2 increase in earth's atmosphere has been accelerating.
Sulfur oxides – sulphur dioxide, a chemical compound with the formula SO2. SO2 is produced in various industrial processes. Coal and petroleum contain sulphur compounds, their combustion generates sulphur dioxide. Further oxidation of SO2 in the presence of a catalyst such as NO2, forms H2SO4, thus acid rain; this is one of the causes for concern over the environmental impact of the use of these fuels as power sources. Nitrogen oxides – Nitrogen oxides nitrogen dioxide, are expelled from high temperature combustion, are produced during thunderstorms by electric discharge, they can be seen as a plume downwind of cities. Nitrogen dioxide is a chemical compound with the formula NO2, it is one of several nitrogen oxides. One of the most prominent air pollutants, this reddish-brown toxic gas has a characteristic sharp, biting odor. Carbon monoxide – CO is a colorless, toxic yet non-irritating gas, it is a product of combustion of fuel such as natural coal or wood. Vehicular exhaust contributes to the majority of carbon monoxide let into our atmosphere.
It creates a smog type formation in the air, linked to many lung diseases and disruptions to the natural environment and animals. In 2013, more than half of the carbon monoxide emitted into our atmosphere was from vehicle traffic and burning one gallon of gas will emit over 20 pounds of carbon monoxide into the air. Volatile organic compounds – VOCs are a well-known outdoor air pollutant, they are categorized as either non-methane. Methane is an efficient greenhouse gas which contributes to enhanced global warming. Other hydrocarbon VOCs are significant greenhouse gases because of their role in creating ozone and prolonging the life of methane in the atmosphere; this effect varies depending on local air quality. The aromatic NMVOCs benzene and xylene are suspected carcinogens and may lead to leukemia with prolonged exposure. 1,3-butadiene is another dangerous compound associated with industrial use. Particulate matter / particles, alternatively referred to as particulate matter, atmospheric particulate matter, or fine particles, are tiny particles of solid or liquid suspended in a gas.
In contrast, aerosol refers to gas. Some particulates occur originating from volcanoes, dust storms and grassland fires, living vegetation, sea spray. Human activities, such as the burning of fossil fuels in vehicles, power plants and various industrial processes generate significant amounts of aerosols. Averaged worldwide, anthropogenic aerosols—those made by human activities—currently account for 10 percent of our atmosphere. Increased levels of fine particles in the air are linked to health hazards such as heart disease, altered lung function and lung cancer. Particulates are related to respiratory infections and can be harmful to those suffering from conditions like asthma. Persistent free radicals connected to airborne fine particles are linked to cardiopulmonary disease. Toxic metals, such as lead and mercury their compounds. Chlorofluorocarbons – harmful to the ozone layer; these are gases which are released from air conditioners, aerosol sprays, etc. On release into the air, CFCs rise to the stratosphere.
Here they come in contact with other gases and