Chapter-18
Air pollution
What isoutdoor air pollution?
Air lets our living planet breathe—it's the mixture of gases that fills the atmosphere, giving life to the plants and animals that make Earth such a vibrant place. Broadly speaking, air is almost entirely made up of two gases (78 percent nitrogen and 21 percent oxygen), with a few other gases (such as carbon dioxide and argon) present in absolutely minute quantities. We can breathe ordinary air all day long with no ill effects, so let's use that simple fact to define air pollution, something like this:
Air pollution is a gas (or a liquid or solid dispersed through ordinary air) released in a big enough quantity to harm the health of people or other animals, kill plants or stop them growing properly, damage or disrupt some other aspect of the environment (such as making buildings crumble), or cause some other kind of nuisance (reduced visibility, perhaps, or an unpleasant odor).
As with water pollution and land contamination, it's the quantity (or concentration) of a chemical in the air that makes the difference between "harmless" and "pollution." Carbon dioxide (CO2), for example, is present in the air around you at a typical concentration of less than 0.05 percent and breathing it in usually does no harm (you breathe it out all day long); but air with an extremely high concentration of carbon dioxide (say, 5–10 percent) is toxic and could kill you in a matter of minutes. Since Earth's atmosphere is very turbulent—many of us live in windy countries—air pollution will often disperse relatively quickly. In less enlightened times, factory operators thought that if they built really high smokestacks, the wind would simply blow their smoke away, diluting and dispersing it so it wouldn't be a problem. The only trouble was, Earth is a much smaller place than we think and pollution doesn't always disappear so conveniently.
NATURAL AIR POLLUTION
When we think of pollution, we tend to think it's a problem that humans cause through ignorance or stupidity—and that's certainly true, some of the time. However, it's important to remember that some kinds of air pollution are produced naturally. Forest fires, erupting volcanoes, and gases released from radioactive decay of rocks inside Earth are just three examples of natural air pollution that can have hugely disruptive effects on people and the planet.
Forest fires (which often start naturally) can produce huge swathes of smoke that drift for miles over neighboring cities, countries, or continents. Giant volcanic eruptions can spew so much dust into the atmosphere that they block out significant amounts of sunlight and cause the entire planet to cool down for a year or more. Radioactive rocks can release a gas called radon when they decay, which can build up in the basements of buildings with serious effects on people's health.
All these things are examples of serious air pollution that happen without any help from humans; although we can adapt to natural air pollution, and try to reduce the disruption it causes, we can never stop it happening completely.
Primarily air pollutants can be caused by primary sources or secondary sources. The pollutants that are a direct result of the process can be called primary pollutants. A classic example of a primary pollutant would be the sulfur-dioxide emitted from factories
Secondary pollutants are the ones that are caused by the inter mingling and reactions of primary pollutants. Smog created by the interactions of several primary pollutants is known to be as secondary pollutant.
UNNATURAL " types of air pollution
Anything people do that involves burning things (combustion), using household or industrial chemicals (substances that cause chemical reactions and may release toxic gases in the process), or producing large amounts of dust has the potential to cause air pollution.
Traffic
There are something like a half billion cars on the road today—one for every two people in rich countries such as the United States. Virtually all of them are powered by gasoline and diesel engines that burn petroleum to release energy. Petroleum is made up of hydrocarbons (large molecules built from hydrogen and carbon) and, in theory, burning them fully with enough oxygen should produce nothing worse than carbon dioxide and water. In practice, fuels aren't pure hydrocarbons and engines don't burn them cleanly. As a result, exhausts from engines contain all kinds of pollution, notably particulates (soot of various sizes), carbon monoxide (CO, a poisonous gas), nitrogen oxides (NOx), volatile organic compounds (VOCs), and lead—and indirectly produce ozone. Mix this noxious cocktail together and energize it with sunlight and you get the sometimes brownish, sometimes blueish fog of pollution we call smog, which can hang over cities for days on end.
TOXIC GASES
Sulfur dioxide: Coal, petroleum, and other fuels are often impure and contain sulfur as well as organic (carbon-based) compounds. When sulfur (spelled "sulphur" in some countries) burns with oxygen from the air, sulfur dioxide (SO2) is produced. Coal-fired power plants are the world's biggest source of sulfur-dioxide air pollution, which contributes to smog, acid rain, and health problems that include lung disease.
Carbon monoxide: This highly dangerous gas forms when fuels have too little oxygen to burn completely. It spews out in car exhausts and it can also build up to dangerous levels inside your home if you have a poorly maintained gas boiler, stove, or fuel-burning appliance. (Always fit a carbon monoxide detector if you burn fuels indoors.)
Carbon dioxide: This gas is central to everyday life and isn't normally considered a pollutant: we all produce it when we breathe out and plants such as crops and trees need to "breathe" it in to grow. However, carbon dioxide is also a greenhouse gas released by engines and power plants. Since the beginning of the Industrial Revolution, it's been building up in Earth's atmosphere and contributing to the problem of global warming and climate change.
Nitrogen oxides: Nitrogen dioxide (NO2) and nitrogen oxide (NO) are pollutants produced as an indirect result of combustion, when nitrogen and oxygen from the air react together. Nitrogen oxide pollution comes from vehicle engines and power plants, and plays an important role in the formation of acid rain, ozone and smog. Like carbon dioxide, nitrogen oxides are also greenhouse gases (ones that contribute to global warming).
Volatile organic compounds (VOCs): These carbon-based (organic) chemicals evaporate easily at ordinary temperatures and pressures, so they readily become gases. That's precisely why they're used as solvents in many different household chemicals such as paints, waxes, and varnishes. Unfortunately, they're also a form of air pollution: they're believed to have long-term (chronic) effects on people's health and they also play a role in the formation of ozone and smog.
Particulates: These are the sooty deposits in air pollution that blacken buildings and cause breathing difficulties. Particulates of different sizes are often referred to by the letters PM followed by a number, so PM10 means soot particles of less than 10 microns (10 millionths of a meter or 10µm in diameter). In cities, most particulates come from traffic fumes.
Ozone: Also called trioxygen, this is a type of oxygen gas whose molecules are made from three oxygen atoms joined together (so it has the chemical formula O3), instead of just the two atoms in conventional oxygen (O2). In the stratosphere (upper atmosphere), a band of ozone ("the ozone layer") protects us by screening out harmful ultraviolet radiation (high-energy blue light) beaming down from the Sun. At ground level, it's a toxic pollutant that can damage health. It forms when sunlight strikes a cocktail of other pollution and is a key ingredient of smog (see box below).
Chlorofluorocarbons (CFCs): Once thought to be harmless, these gases were widely used in refrigerators and aerosol cans until it was discovered that they damaged Earth's ozone layer. We discuss this in more detail down below.
Unburned hydrocarbons: Petroleum and other fuels are made of organic compounds based on chains of carbon and hydrogen atoms. When they burn properly, they're completely converted into harmless carbon dioxide and water; when they burn incompletely, they can release carbon monoxide or float into the air in their unburned form, contributing to smog.
Lead and heavy metals: Lead and other toxic "heavy metals" can be spread into the air either as toxic compounds or as aerosols (when solids or liquids are dispersed through gases and carried through the air by them) in such things as exhaust fumes and the fly ash (contaminated waste dust) from incinerator smokestacks.
SMOG
Smog isn't the stuff that pumps from a car's tailpipe or drifts from a factory smokestack—it's the nasty brown or blue haze that builds up over a city as a result.
Smog (a combination of the words "smoke" and "fog") forms when sunlight acts on a cocktail of pollutant gases such as nitrogen and sulfur oxides, unburned hydrocarbons, and carbon monoxide; that's why it's sometimes called photochemical smog (the energy in light causes the chemical reaction that makes smog). One of the most harmful constituents of smog is a toxic form of oxygen called ozone, which can cause serious breathing difficulties and even, sometimes, death. When smog is rich in ozone, it tends to be a blueish color, otherwise it's more likely to be brown.
Although smog can happen in any busy city, it's a particular problem in places such as Los Angeles where the local climate (influenced by the ocean and neighboring mountains) regularly causes what's known as a temperature inversion. Normally, air gets colder the higher up you go but in a temperature inversion the opposite happens: a layer of warm air traps a layer of cold air nearer the ground. This acts like a lid over a cloud of smog and stops it from rising and drifting away. Largely because of their traffic levels, smog afflicts many of the world's busiest cities, including Athens, Beijing, Mexico City, Milan, and Tokyo.
Effects of Air pollution
1. Respiratory and heart problems: The effects of Air pollution are alarming. They are known to create several respiratory and heart conditions along with Cancer, among other threats to the body. Several millions are known to have died due to direct or indirect effects of Air pollution. Children in areas exposed to air pollutants are said to commonly suffer from pneumonia and asthma.
2. Global warming: Another direct effect is the immediate alterations that the world is witnessing due to Global warming. With increased temperatures world wide, increase in sea levels and melting of ice from colder regions and icebergs, displacement and loss of habitat have already signaled an impending disaster if actions for preservation and normalization aren’t undertaken soon.
INDOOR AIR POLLUTION
Numerous forms of indoor air pollution are possible in the modern home. Air pollutant levels in the home increase if not enough outdoor air is brought in to dilute emissions from indoor sources and to carry indoor air pollutants out of the home. In addition, high temperature and humidity levels can increase the concentration of some pollutants. Indoor pollutants can be placed into two groups, biologic and chemical.
Biologic Pollutants
Biologic pollutants include bacteria, molds, viruses, animal dander, cat saliva, dust mites, cockroaches, and pollen. These biologic pollutants can be related to some serious health effects. Some biologic pollutants, such as measles, chickenpox, and influenza are transmitted through the air. However, the first two are now preventable with vaccines. Influenza virus transmission, although vaccines have been developed, still remains of concern in crowded indoor conditions and can be affected by ventilation levels in the home.
Common pollutants, such as pollen, originate from plants and can elicit symptoms such as sneezing, watery eyes, coughing, shortness of breath, dizziness, lethargy, fever, and digestive problems. Allergic reactions are the result of repeated exposure and immunologic sensitization to particular biologic allergens.
Although pollen allergies can be bothersome, asthmatic responses to pollutants can be life threatening. Asthma is a chronic disease of the airways that causes recurrent and distressing episodes of wheezing, breathlessness, chest tightness, and coughing Asthma can be broken down into two groups based on the causes of an attack: extrinsic (allergic) and intrinsic (nonallergic). Most people with asthma do not fall neatly into either type, but somewhere in between, displaying characteristics of both classifications. Extrinsic asthma has a known cause, such as allergies to dust mites, various pollens, grass or weeds, or pet danders. Individuals with extrinsic asthma produce an excess amount of antibodies when exposed to triggers. Intrinsic asthma has a known cause, but the connection between the cause and the symptoms is not clearly understood. There is no antibody hypersensitivity in intrinsic asthma. Intrinsic asthma usually starts in adulthood without a strong family history of asthma. Some of the known triggers of intrinsic asthma are infections, such as cold and flu viruses, exercise and cold air, industrial and occupational pollutants, food additives and preservatives, drugs such as aspirin, and emotional stress. Asthma is more common in children than in adults, with nearly 1 of every 13 school-age children having asthma
AIR POLLUTION BY ENVIRONMENTAL TOBACCO SMOKE
Burning tobacco is the main source of indoor pollution in the developed world. Tobacco smoke contains about 4,000 chemicals including carcinogens, irritants and toxic gases. The health impact of breathing environmental tobacco smoke is well documented. Many potentially toxic gases are present in higher concentrations in sidestream smoke than in mainstream smoke and nearly 85% of the smoke in a room results from sidestream smoke. The particulate phase includes tar (itself composed of many chemicals), nicotine, benzene and benzo(a)pyrene. The gas phase includes carbon monoxide, ammonia, dimethylnitrosamine, formaldehyde, hydrogen cyanide and acrolein. Some of these have marked irritant properties and some 60 are known or suspected carcinogens (cancer causing substances). The Environmental Protection Agency (EPA) in the USA has classified environmental tobacco smoke as a class A (known human) carcinogen along with asbestos, arsenic, benzene and radon gas.[ Lee Jong-wook,2004 ,WHO]
Breathing other people's smoke is called passive, involuntary or secondhand smoking. The non-smoker breathes "sidestream" smoke from the burning tip of the cigarette and "mainstream" smoke that has been inhaled and then exhaled by the smoker. Secondhand smoke (SHS) is a major source of indoor air pollution..Aldicarp,chlorpyrifos and methyl bromide are highly toxic pestisides and commonly used to fumigate the soil prior to planting tobacco seedling. In 1997, over 5.5 million pounds of methyl bromide were applied to tobacco fields worldwide. The effects of these chemicals are not monitored generally but it is known that they leach into the soil and find their way into streams, rivers, and food chains. These substances may indirectly cause the genetic selection of pesticide-resistant mosquitoes or flies, making the control of diseases such as malaria much more difficult.[Lee Jong-wook,2004,WHO ]
In 1998, a report by the Independent Scientific Committee on Smoking and Health (SCOTH) reviewed the evidence on passive smoking and concluded that: “Smoking in public places should be restricted on the grounds of public health.” The report added that “Wherever possible, smoking should not be allowed in the work place.” A BMA(British medical association) report, “Towards smoke-free public places” published in December 2002, also called for a ban on smoking in public places. A survey by Action on Smoking and Health( ASH) in April 1999 revealed that about 3 million people in the UK are exposed to passive smoking in their places of work. A national survey commissioned by SmokeFree London found that over half of non-smoking employees (51%) are still exposed to tobacco smoke at work, with almost a third (31%) being exposed every day or most days. A survey commissioned by ASH found that 80% would support a law to require all enclosed workplaces to be smokefree. Public opinion surveys have shown widespread support for smoking restrictions in public places and this has been growing steadily in recent years.
The 2002 British government commissioned survey of smoking attitudes found that 86% of respondents (including 70% of smokers) agreed that smoking should be restricted at work and a similar proportion favoured smoking restrictions in restaurants. The survey also revealed that a majority of people supported smoking restrictions in pubs.
The WHO Framework Convention on Tobacco Control, which was adopted in May 2003 by WHO’s 192 member States, is intended as a common framework in which countries can work together to address the challenge that tobacco use represents at the global level. Tobacco use has also a development dimension..Tobacco causes around 13 500 deaths per day .Half of children are exposed to tobacco smoke at home. 47.5% of men smoke and 10.3% of women smoke. A cigarette is the only legally available consumer product that kills through normal use 2000: Business: market share: World's largest tobacco companies: 1. China national tobacco company 31% [china has 385 million smokers] 2. Philip Morris 17% 3. British American tobacco (bat) 13% 4. Rjr reynolds 6% 1999: consumption: China annual cigarette volume: around 1.6 trillion cigarettes US: around 415 billion sticks.Japan: 327 billion russia: 257 billion Germany: 140 billion India: just under 100 billion. Brazil: 97 billion 1999: consumption: about 10 million americans smoke cigars. In the year 2004 the Central Govt of India passed a legislation on advertisement, production, trade and sale of tobacco and tobacco products .banning the advertisement of tobacco & tobacco products on Tv, newspapers and media from 01 May 2004 Reason tobacco leaves contain an alkaloid nicotine which is lethal ,carcinogen and causes addiction. Table 1 Indoor air standards of nicotine; Table2 Toxic levels of nicotine. [Encyclopedia of Clinical Toxicology & Handbook of Environmental Data on Organic Clinical Data Vol 2] .
GREEN TOBACCO SICKNESS (GTS)
Tobacco growers are susceptible to an occupational illness known as green tobacco sickness. This is caused by the absorption of nicotine through the skin from contact with wet tobacco leaves. Symptoms of green tobacco sickness include nausea, weakness, dizziness and abdominal cramps, and fluctuations in blood pressure and heart rates. It is not known exactly now many tobacco workers are affected by green tobacco sickness but one study of migrant workers in North Carolina USA suggests that 41% of the workers get the illness at least once during harvest season. [SCOTH 1998].
EFFECT OF CHEWING TOBACCO ON THE HUMAN BODY
Tobacco use is a major preventable cause of premature death and of several general diseases. In addition to cigarette, pipe, cigar and bidi smoking, betel quid chewing (pan), guhtka use and other traditional forms of tobacco have several effects in the mouth. Tobacco is a risk factor for oral cancer, oral cancer recurrence, adult periodontal diseases and congenital defects such as cleft lip and palate in children. Tobacco suppresses the immune system's response to oral infection, compromises healing oral surgical and accidental wounding, promotes periodontal degeneration in diabetics and adversely affects the cardiovascular system. Moreover, tobacco greatly increases the risk when used in combination with alcohol or areca nut. Most oral consequences of tobacco use impair quality of life be they as simple as halitosis, as complex as oral birth defects, as common as periodontal disease or as troublesome as complications during wound healing.
EFFECT OF PASSIVE SMOKING ON THE HUMAN BODY
Some of the immediate effects of passive smoking include eye irritation, headache, cough, sore throat, dizziness and nausea. Adults with asthma can experience a significant decline in lung function when exposed, while new cases of asthma may be induced in children whose parents smoke. Short term exposure to tobacco smoke also has a measurable effect on the heart in non-smokers. Just 30 minutes exposure is enough to reduce coronary blood flow. [Otsuka R., 2001]
In the longer term, passive smokers suffer an increased risk of a range of smoking-related diseases. Non-smokers, who are exposed to passive smoking in the home, have a 25 per cent increased risk of heart disease and lung cancer.] A major review by the Government-appointed Scientific Committee on Tobacco and Health (SCOTH 1998) concluded that passive smoking is a cause of lung cancer and ischaemic heart disease in adult non-smokers, and a cause of respiratory disease, cot death, middle ear disease and asthmatic attacks in children. A more recent review of the health impacts of passive smoking by the International Agency for Research on Cancer (IARC) noted that “the evidence is sufficient to conclude that involuntary smoking is a cause of lung cancer in never smokers”.[ UNCTAD, 2004 ]
Whilst the relative health risks from passive smoking are small in comparison with those from active smoking, because the diseases are common, the overall health impact is large. The British Medical Association has conservatively estimated that secondhand smoke causes at least 1,000 deaths a year in the UK. However, the true figure is likely to be much higher. Professor Konrad Jamrozik of Imperial College London estimated that domestic exposure to secondhand smoke causes at least 3,600 deaths annually from lung cancer, heart disease and stroke combined, while exposure at work leads to approximately 700 deaths from these causes. Jamrozik also estimates 49 deaths – or about 1 a week – from exposure at work in the hospitality trades. In the population aged 65 or older, passive smoking is estimated to account for 16,900 deaths annually. 9,700 are due to stroke, where current evidence of health effects is weakest.
.[Jamrozik Konrad (2004) ].
Almost half of all children in the UK are exposed to tobacco smoke at home. Passive smoking increases the risk of lower respiratory tract infections such as bronchitis, pneumonia and bronchiolitis in children. One study found that in households where both parents smoke, young children have a 72 per cent increased risk of respiratory illnesses. Passive smoking causes a reduction in lung function and increased severity in the symptoms of asthma in children, and is a risk factor for new cases of asthma in children. Passive smoking is also associated with middle ear infection in children as well as possible cardiovascular impairment and behavioural problems.
Infants of parents who smoke are more likely to be admitted to hospital for bronchitis and pneumonia in the first year of life. More than 17,000 children under the age of five are admitted to hospital every year because of the effects of passive smoking. Passive smoking during childhood predisposes children to developing chronic obstructive airway disease and cancer as adults. Exposure to tobacco smoke may also impair olfactory function in children. A Canadian study found that passive smoking reduced children’s ability to detect a wide variety of odours compared with children raised in non-smoking households. Passive smoking may also affect children’s mental development. A US study found deficits in reading and reasoning skills among children even at low levels of smoke exposure.[ Hackshaw AK et al.,1997]
Scientists from Canada reported finding evidence of cigarette smoke in fetal hair, the first biochemical proof that the offspring of non-smoking mothers can be affected by passive cigarette smoke. Smoking during pregnancy can harm the baby .[Fielding, JE and Phenow ,KJ,1998].
There is a rise in impotency in men with a nicotine addiction .Women with smoking husbands are unable to conceive .number of still births are more in cases of smoking fathers . Exposure to passive smoking during pregnancy is an independent risk factor for low birth weight. A recent study has also shown that babies exposed to their mother’s tobacco smoke before they are born grow up with reduced lung function Parental smoking is also a risk factor for sudden infant death syndrome (cot death).
Lung cancer, which was rare before the 20th century, increased dramatically by the 1930s. The American Cancer Society and other organizations initiated studies comparing deaths among smokers and nonsmokers over a period of several years. All such studies found increased mortality among smokers, both from cancer and other causes The American Cancer Society estimates that cigarettes are responsible for about 431,000 deaths in the United States each year. Lung cancer accounts for about 30 percent of all cancer deaths in the United States, and smoking accounts for nearly 90 percent of lung cancer deaths. The risks of dying from lung cancer are 23 times higher for male smokers and 13 times higher for female smokers than for nonsmokers. Additionally, smokers are at increased risk for many other types of cancer. The National Cancer Center (NCC) South Korea officially confirmed that smoking causes lung cancer .[UNCTAD,2004]
In addition to the health risks posed by using pesticides[aldicarb and chlorpyrifos, Methyl bromide,an ozone-depleting chemical A study published in the British Medical Journal suggests that previous studies of the effects of passive smoking on the risk of heart disease may have been under-estimated. The researchers found that blood cotinine levels among non-smokers were associated with a 50-60% increased risk of heart disease. [EPA,1992]
Nicotine causes thickening of blood. nicotine increases chlorestrol deposistion. [Law Mr et al.(1997)]
For those who do not inhale, tobacco smoke does not reach the lungs in the same quantity as it does in cigarette smokers. Therefore, the risk of death from lung cancer is not as high as it is for cigarette smokers, but is still several times higher than the risk for non-smokers.
PATERNAL SMOKING AND CHILDHOOD CANCERS
A putative association between cancer in children and paternal smoking at the time of their conception has been proposed in studies based on the Oxford Survey of Childhood Cancers and a large case-control investigation from Shanghai. The Committee examined the published papers and certain limitations were noted, but it was agreed that there were plausible hypothetical mechanisms whereby paternal smoking at the time of conception could induce an increase in cancers in the offspring.
There are many changes found in the histological type of lungs which causes the changes in lung cancer incidences in the several part of the world. Squamous and small cell carcinomas, arising from the larger bronchi, are traditionally associated with smoking, but relative and absolute increases in the incidence of adenocarcinomas of the lung have been increasingly recognised. A recent study from Switzerland demonstrates rising incidence rates for adenocarcinomas in both younger men and women in the early 1990s, the rates being more than 3-fold higher than for squamous carcinomas in the same groups. This alteration in histological pattern almost certainly reflects changes in the pattern of exposure of bronchial tissues to tobacco-associated carcinogens. Smokers of modern low-tar filtered cigarettes tend to compensate by increasing the number and depth of puffs, the peripheral parts of the lung are thus more exposed to larger amounts of tobacco-associated carcinogens, and it is in the peripheral parts of the lung that adenocarcinomas develop. The diagnostic and therapeutic implications of an increase in lung adenocarcinomas are likely to be considerable. [EPA(1999) California].Table 3[analysis of lower respiratory illness in children]
CIGARS AND CIGARETTES
A cigar is defined, as "any roll of tobacco wrapped in leaf tobacco or in any substance containing tobacco," while a cigarette is "any roll of tobacco wrapped in paper or any substance not containing tobacco." Most cigars are made up of a single air-cured or dried burley tobacco. Cigar tobacco leaves are first aged for about a year and then fermented in a multi-step process that can take from 3 to 5 months. Fermentation causes chemical and bacterial reactions that change the tobacco and give cigars a different taste and smell from cigarettes. Cigars come in different sizes, some as small as a cigarette (called a cigarillo), others much larger. Large cigars typically contain between 5 and 17 grams of tobacco. It is not unusual for some premium brands to have as much tobacco in 1 cigar as in a whole pack of cigarettes. Large cigars can take between 1 to 2 hours to smoke.While the reasons people smoke cigars are varied, the fact is, like cigarettes, cigars can become addictive. Nicotine is the substance in tobacco that causes addiction. Most cigars have as much nicotine as several cigarettes. If cigar smokers inhale, nicotine is absorbed as rapidly as it is with cigarettes. For those who do not inhale, it is absorbed more slowly through the lining of the mouth. People who use smokeless tobacco absorb nicotine the same way. Both inhaled and non-inhaled nicotine are highly addictive. [Table 4 Ingredients of a cigarette]
Cigar smoking increases your risk of death from several cancers, including cancer of the lung, oral cavity (lip, tongue, mouth, throat), oesophagus (the tube connecting the mouth to the stomach), and larynx (voice box). If you inhale, cigar smoking appears to be linked to death from cancer of the pancreas and bladder, as well. Carcinogens in cigar smoke include the following: benzene , aromatic amines (especially carcinogens such as 2-naphthylamine and 4-minobiphenyl) ,vinyl chloride ,ethylene oxide,arsenic ,chromium ,cadmium ,nitrosamines ,polynuclear , aromatic hydrocarbons . [NIDA FACTS 2006]
THE CIGARETTE TEST METHOD
Cigarette ratings for "tar," nicotine and carbon monoxide are currently determined by machine testing conducted in accordance with a methodology adopted by the Commission in 1967. The "tar" and nicotine testing program was intended to provide smokers seeking to switch to lower "tar" cigarettes with a single, standardized measurement with which to choose among the then-existing brands.
Over the past 30 years that the current system has been in place, there have been dramatic decreases in the machine-measured "tar" and nicotine yields of cigarettes. Since 1968, the average sales-weighted machine-measured "tar" yield has fallen fr