Principles of Air Quality Management - Chapter 2 docx

21 2 Effects of Air Pollution And what may be the cause of these troublesome effects, but the inspiration of this infernal vapour, accompaning the Aer, which … enters by several branches into the very Parenchyma, and substance of the Lungs, violating, in this passage, the Larynx and Epiglottis, … which, becoming rough and drye, can neither be contracted, or dilated for the due modulation of the Voyce. Fumifugium , 1661 The effects noted during the 1952 London Smog Disaster were obvious but not perceived — nearly 1000 deaths per day, where beforehand the normal death rate was a few hundred deaths a day at most. It was reported that the increase of deaths during the London smog siege was not noticed during the event, but the shortage of coffins and flowers was. Today we are much more aware of acute as well as long- term or chronic health effects. Air pollution was known to cause damage to the entire ecosystem even before Fumifugium was published. Such damage includes adverse effects on human health; damage to crops, vegetation, and forests; and finally, damage to materials that we all use. Our goal in this chapter is to review and evaluate the effects on human health of the different air contaminants. Then, we consider contaminants’ effects on veg- etation, crops, and finally, other materials. TIME EFFECTS AND SENSITIVITIES A CUTE VERSUS C HRONIC As seen during the London Smog Disaster, the immediate effect of the air pollution was acute — death. Only in the last few years has there been new research to show the long-term complications of air pollution that occurred months and years earlier. Initial estimates were that about 4,000 people had died as a result of the smog siege; now the epidemiological evidence indicates that about 12,000 died of complications over the course of 6 months following that event. There are two time-related categories of health effects. The first deals with acute effects, that is, those health effects that tend to act immediately on a specific target organ or point of entry into the human body. In the air pollution field, these points of entry are typically the eyes and the lungs, as they are in immediate contact with the ambient air. Burns and asphyxiation are other examples of acute health effects. It is possible for a contaminant to have an acute effect that is different from its chronic effect. 7099_book.fm Page 21 Friday, July 14, 2006 3:13 PM © 2007 by Taylor & Francis Group, LLC 22 Principles of Air Quality Management, Second Edition Chronic (Greek, chronos ) effects are those that refer to time functions of exposure. Thus, there may be long-term exposure or a long period between an exposure and the effect. In general, this latter term refers to a more specific concept, termed latency. S ENSITIVE P OPULATIONS The general population ranges from vigorously hearty individuals to those who are particularly susceptible to ambient pollutants. Table 2.1 lists those general population groupings that are considered sensitive to air pollution. In the London Smog Disaster, it was initially thought that only the elderly were affected. However, later research has shown that most of the deaths occurred in the 45–65-year-old age category. Within each of these general population groupings there may be some overlap of effects as well as the possibility of multiple sensitivities. Pregnancy is another consideration. It has been estimated that roughly 7% of the population already suffers from some forms of cardiovascular disease, with approximately 9% being susceptible to chronic respiratory diseases. Ten percent may be considered elderly, with possibly 20% being children under the age of 14 years. On the average, perhaps an additional 7% of the general population may be involved in some form of vigorous athletic activity. Again, although not exclusive, these numbers would indicate that perhaps half the total population in any location may have an existing sensitivity to air pollution. CRITERIA VERSUS NONCRITERIA AIR POLLUTANTS There are differences between how criteria and noncriteria pollutants act. Before evaluating specific pollutant effects, it is instructive to differentiate between these two groupings of air pollutants; Table 2.2 summarizes the differences. Lead, a criteria pollutant, is the exception to this discussion, as it is obviously toxic. In general, criteria pollutants have a known threshold dose, below which no adverse health effects are known to remain after cessation of exposure. With respect to carcinogens, there is no known threshold to which we can point with confidence. In comparison to the noncriteria or hazardous air pollutants (HAPs), which are potentially numerous, there are only six criteria air pollutants. Other significant differences are that the gaseous criteria pollutants occur in the ambient air at the level of parts per million, whereas HAPs tend to reach the level of parts per billion. TABLE 2.1 Population Groups Sensitive to Air Pollution Population Group Percentage of Population Cardiovascular disease 7 Chronic respiratory disease 8.9 Elderly (>65 years of age) 9.6 Children (<14 years of age) 20 Athletic activities 7 Total 52.5 7099_book.fm Page 22 Friday, July 14, 2006 3:13 PM © 2007 by Taylor & Francis Group, LLC Effects of Air Pollution 23 Indeed, it has only been with the advent of modern technology that we have been able to regularly and routinely monitor these trace contaminants in the ambient air. The criteria pollutants are not bioaccumulated in tissues, whereas many HAPs do tend to bioaccumulate. Thus, HAPs may have significant effects on long-term health. The lung is the primary target organ for criteria pollutants (with the exception of carbon monoxide). The noncriteria or hazardous air pollutants, in contrast, have potentially many target organs. Human health effects data are readily available for the criteria pollutants because they have been studied not only in the ambient air (in some cases for over 100 years) but also in occupational exposures. With respect to the HAPs there is much less human health data available, particularly for dose–response relationships for carcin- ogens, mutagens, and teratogens. The effects of the criteria pollutants tend to last a period of minutes to months, whereas the HAPs tend to have long-term effects. Finally, the criteria pollutants exhibit more immediate or acute effects; HAPs tend to cause chronic health effects. C RITERIA A IR P OLLUTANT E FFECTS Of the criteria pollutants, ozone, sulfur dioxide, fine particulates, and nitrogen dioxide have both acute and chronic health effects. Carbon monoxide has acute effects only, whereas lead, being a toxic metal, has chronic effects (at ambient air levels). Ozone Ozone is a strong oxidizer that affects the respiratory system, leading to damage of lung tissues. Among the acute effects are cough and chest pain, eye irritation, headaches, lung function losses, and asthma attacks. Within the lung itself, there is damage to the ciliated cells. These cells are responsible for the clearance mechanism for particulate matter in the lungs. Figure 2.1a shows healthy lung tissue with active cilia, and Figure 2.1b shows lung TABLE 2.2 Criteria and Hazardous Air Pollutant Comparisons Criteria Pollutants* Hazardous Air Pollutants Few (6) Potentially numerous Not bioaccumulated Some may bioaccumulate Lung is primary target organ (except CO) Many target organs Human health effects readily available Human dose–response data rarely available Effects generally occur in from minutes to months Effects generally occur after long latent period (years) Primarily acute effects Primarily chronic effects * As regulated under the Clean Air Act, except lead. 7099_book.fm Page 23 Friday, July 14, 2006 3:13 PM © 2007 by Taylor & Francis Group, LLC 24 Principles of Air Quality Management, Second Edition tissue after exposure to ozone for an extended period of time. The damage to the cilia is apparent. In addition, ozone damages the alveoli cell membranes. These membranes are the individual air sacs in the lung in which the exchange of oxygen and carbon dioxide takes place between the air and the blood. Chronic exposures to elevated ozone levels are responsible for losses in immune system functions, accelerated aging, and increased susceptibility to other infections. In addition, because of its nature as an oxidizer, there are prospects for permanent loss of the alveoli cells. Sulfur Dioxide Sulfur dioxide has its own acute health effects, again with the lungs being the target organs. These adverse health effects include irritation and restriction of air passages. FIGURE 2.1a Healthy lung tissue with active cilia. 7099_book.fm Page 24 Friday, July 14, 2006 3:13 PM © 2007 by Taylor & Francis Group, LLC Effects of Air Pollution 25 There is reduced mucus clearance from the restricted air passages and chest tightness. Figure 2.2 shows, in an e-ray of the lung, the differences before and after exposure to sulfur dioxide. Under normal conditions, the lung passages are open; after expo- sure, the lung passages constrict in a response to SO 2 . This constriction also further aggravates other health conditions. Otherwise healthy individuals may also experience sore throats, coughing, and breathing difficulties, in addition to a noticeable odor at concentrations approaching 0.5 ppm. There are some indications of an increased sensitivity to sunlight resulting from acute exposures. For chronic effects, sulfur dioxide is responsible for immune system suppression and for an increased probability of bronchitis. The latter is of particular concern for individuals with emphysema. There are some indications that chronic exposure to sulfur dioxide may also act as a cancer promoter in addition to being an immune system suppressor. FIGURE 2.1b Lung tissue with damage to cilia after exposure to ozone for an extended period of time. 7099_book.fm Page 25 Friday, July 14, 2006 3:13 PM © 2007 by Taylor & Francis Group, LLC 26 Principles of Air Quality Management, Second Edition Particulate Matter Among the acute health effects of elevated concentrations of fine particulates are increases in mortality rate, increased incidence of asthma and bronchitis, and increased rates of infection in the respiratory system. These particulates also directly irritate the respiratory tract, constrict airways, and interfere with the mucus lining of the lung passages. Among the chronic effects of fine particulates are losses of lung capacity and lung damage, resulting from scarring caused when fine particulates are not cleared from the lung passages or alveoli. In addition, fine particulates act as carriers for toxic contaminants and, in particular, heavy metals. This occurs when the contam- inants exist in a fume or a vapor state and condense onto the fine particulates. In the alveolar regions, heavy metals may be absorbed into the blood and circulated to other parts of the body. Particulates, and in particular the fine-particulate fractions, are also responsible for visibility reduction. Visibility loss may be considered a psychological stress. Nitrogen Dioxide In addition to participating in the formation of photochemical ozone at ground level, nitrogen dioxide has its own particular health effects. The acute effects of nitrogen dioxide are both direct and indirect. The direct effects are damages to the cell membranes in the lung tissues as well as constriction of the airway passages. Asthmatics are, in particular, affected by these acute effects. The indirect effects are that nitrogen dioxide causes edema, or a filling of the intercellular spaces with fluid, which may develop into local areas of infection. FIGURE 2.2 The lung after (left) and before (right) exposure to sulfur dioxide. 7099_book.fm Page 26 Friday, July 14, 2006 3:13 PM © 2007 by Taylor & Francis Group, LLC Effects of Air Pollution 27 Among the chronic effects of long-term exposures to nitrogen dioxide is necrosis, a term for direct cell death. In addition, there is evidence that NO 2 causes a thickening of the alveolar walls of the lungs, which interferes with efficient oxygen and carbon dioxide exchange across those cell walls. There also appears to be a correlation with increased susceptibility to other lung diseases through chronic exposures. Some evidence indicates that when mice are exposed to nitrogen dioxide and injected with cancer cells, they develop more cancerous lung nodules than do mice who are injected with cancer cells but who breathe clean, filtered air. Other studies of NO 2 exposure on mice indicate that changes in lung tissue structure are similar to those that occur in human lungs in the early stages of emphysema. There also appears to be evidence that other target organs may be affected by nitrogen dioxide. The University of Southern California conducted experiments demonstrating that inhaling NO 2 enlarges the spleen and lymph nodes in mice. The spleen and lymph nodes are important organs in the body’s defense system. This finding indicates that the body’s immune system may be adversely affected by exposure to chronic levels of nitrogen dioxide. Carbon Monoxide Carbon monoxide affects health through binding with hemoglobin in the blood. Hemoglobin is the oxygen-carrying protein that is responsible for the oxygen and CO 2 exchanges necessary for life. When CO binds to hemoglobin, the blood loses its ability to transmit vital oxygen to all tissues of the body. At high levels of carbon monoxide, the potential exists for asphyxiation. In addition, impairment of perfor- mance, slow reflexes, fatigue, and headaches caused by the lack of oxygen in the brain are experienced. There are aggravated heart and lung disease symptoms with elevated readings of carbon monoxide, as well as impairments in the central nervous system and brain functions. The concerns about carbon monoxide are even greater at higher elevations, where the partial pressure of oxygen is lower and where many persons may already suffer from an inadequate oxygen supply. Lead Lead, being a toxic metal, acts in a different manner than the other criteria pollutants. It is a systemic toxicant and therefore damages a number of different target organs in the body. Because it is a metal, it is distributed throughout the body and can be responsible for central nervous system damage. Brain functions affected include behavioral changes, losses of muscle control and learning difficulties. These are the most important aspects of lead exposures. In addition, lead impacts certain key enzymes in the production of red blood cells, which brings on anemia. This is the most characteristic symptom of lead exposure in both children and adults. In addition, there is evidence of kidney damage, liver and heart damage, and damage to the reproductive organs. A combination of effects, including damage to enzyme systems, is possible in these target organs. 7099_book.fm Page 27 Friday, July 14, 2006 3:13 PM © 2007 by Taylor & Francis Group, LLC 28 Principles of Air Quality Management, Second Edition BASIC PRINCIPLES OF TOXICOLOGY A basic understanding of the elements of toxicology is important to understand air pollution health effects. The majority of this information deals with animal studies. Similarities and differences, of course, are drawn to epidemiology studies and to true human exposures in laboratory settings. S OURCES OF H EALTH E FFECTS I NFORMATION What we know about the effects of air pollution on people comes to us from three major sources. Each of these sources is needed to gain a good understanding of air pollution’s health effects. These three sources are animal studies, human exposure studies, and epidemiology. Animal effect studies are used to a large extent because we can control the conditions surrounding the animals. The animals used range from microbes to mice. We are also able to perform long-term (potentially generational) studies on test animals. This is a positive aspect because we are able to monitor and control conditions. Unfortunately, as a result of species differences noted later, the health effects for a given exposure to an air pollutant are not necessarily transferable to human beings. The second technique is to gather effects data by human exposure studies. These studies are performed under controlled conditions in a laboratory, using exposures of specific contaminants to real people; therefore, the results are directly transferable to different segments of the population. In one sense, this may provide us with the best data, as it is species specific. Such exposure studies are limited, however, because we cannot expose individuals to cancer-causing agents or to those that cause reproductive toxicity or other life-threatening contaminants. These studies are expen- sive and are generally limited to a maximum period of 8 hours. Therefore, no chronic effects may be studied. Likewise, we are not able to gain an understanding of subtle, or microcellular, effects that may occur through human exposure to various air contaminants. Epidemiology is another approach by which we are able to study human responses to air contaminants. This type of study may be done over long time periods. Thus, the data may allow for evaluations of chronic exposures. Also, we are dealing with real people. The limitations are that the researchers have a very limited control over significant variables involved, such as lifestyle, smoking habits, age, sleep patterns, nutrition, and so on. These studies also tend to be costly because a great deal of time must be spent observing individuals and accessing medical records over a period of years. It is important not to assume only one source of exposure when dealing with health data. Early assumptions made about air pollution and lead-based paint being the only sources of lead exposure in Southern California were recently found to be erroneous. It was discovered in 2004 that children with high blood lead levels were eating certain flavored candies from Mexico that were found to be significant sources of lead poisoning. Between 5% and 10% of all the candy tested was found to be over the federal regulatory lead level. 7099_book.fm Page 28 Friday, July 14, 2006 3:13 PM © 2007 by Taylor & Francis Group, LLC Effects of Air Pollution 29 D OSE –R ESPONSE Toxicity tests, and what we learn from them, are at the heart of understanding health effects. Because it is illegal to expose people to suspected toxicants, other species are used to quantify the effects that may be expected from exposure to hazardous or toxic substances. A generalized dose–response curve is seen in Figure 2.3, which illustrates the response of test animals to a chemical. From this dose–response curve, one may determine the LD 50 for those animals to that chemical. (LD 50 is the lethal dose for 50% of the test animals.) Of particular importance is the shape of the curve and the implications thereof. First, it is an S-shaped curve, which indicates that effects are different for incremental changes in dose. Second, it does not go through the origin (zero response at zero dose). This indicates that the true effect at very low doses is unknown (or zero for some minimal dose). These important points are examined in detail later. For the lower dashed line in the figure, one may see that there is essentially no response until some low-level dose is reached, at which point the effect becomes truly observable. This is the threshold concept and is observed for virtually all materials. The upper dashed line is a linear extrapolation between the lower test points and the origin on the curve. This extrapolation presumes that there will always be a response for a given dose. All other extrapolations are based on assumptions on the part of the investigator. Major species differences do exist, and they present the biggest problem in trying to extrapolate dose–response information to all dosage levels. Absorption rates, metabolic activity, and excretion rates are all included in the differences between species. Individual differences in the same species can have a dramatic effect on the response of the test animal. Habitat (e.g., aquatic vs. terrestrial) is also important, and such features as genetic traits, sex and hormones, nutrition, and age of the test animals in some degree also give a scatter in the response data to a given dose. After microbes, mice and rats are used. This is because they are cheap, have a relatively short life span, and are mammals. FIGURE 2.3 Generalized dose–response curve showing low dose extrapolations. 100 50 Dose Response 7099_book.fm Page 29 Friday, July 14, 2006 3:13 PM © 2007 by Taylor & Francis Group, LLC 30 Principles of Air Quality Management, Second Edition The four most important parameters in comparing dose–response curves and attempting to draw conclusions are species, dose, time period, and endpoint or response chosen. The biggest problems in interpretation are related to interspecies differences in response to any given chemical. ROUTES OF EXPOSURE The four major routes of exposure to hazardous chemicals are inhalation, ingestion, dermal absorption, and injection. Within the environmental field, the last is a minor route of exposure to environmental contaminants compared with the other three. Because injection is most often used with experimental animals, the results of experiments using animal tests may not be comparable with the effects from other routes of exposure. I NHALATION Inhalation, the major route of entry involved when dealing with air pollutants, involves the intake of airborne chemicals during breathing. The solubility of the material in the blood affects the degree of its absorption. Once in the blood via the lungs, it goes directly to the brain and the rest of the body. The most common example of environmental exposure via inhalation is the absorption of carbon monoxide through smoking. Carbon monoxide has several hundred times greater binding affinity for hemoglobin than oxygen does. Hemoglo- bin is the iron-based organic compound that is responsible for all oxygen transport in the blood. Oxygen is “bound” by hemoglobin and is later given up by hemoglobin to the tissues. When oxygen is displaced irreversibly by carbon monoxide, the transport phenomenon is not able to function, and oxygen starvation of cells begins. The retention of airborne particulates that are, or that may carry, toxic elements or chemicals is highly dependent on particle size because of the structure of the human lung. The smaller sizes penetrate deeper and have a greater effect. RESPONSE TO AIRBORNE CHEMICALS Chemical agents have a different effect on different member organs of the body depending on the dose and route of exposure. Chemicals target specific organs depending on oil or fat solubility, the effect that the chemical may have on enzyme activity, or physical interruption of the transmission of electrical impulses. Table 2.3 lists a variety of systemic poisons that influence different target organs in the human body by type of chemical or hazardous substance. The hepatotoxic agents, such as carbon tetrachloride, primarily affect the liver, whereas nephrotic agents (halogenated hydrocarbons) affect the kidneys. The neurotoxic agents that affect the nerve system include methyl alcohol, carbon monoxide, heavy metals, and organometallic compounds. The hematopoietic toxins affect the blood or blood cells and consist of aromatic compounds such as benzene, phenols, aniline, and toluidine. 7099_book.fm Page 30 Friday, July 14, 2006 3:13 PM © 2007 by Taylor & Francis Group, LLC [...]... The reaction of SO2 with copper results in the familiar green coating of copper sulfate that forms on the surface of copper-coated materials © 20 07 by Taylor & Francis Group, LLC 7099_book.fm Page 42 Friday, July 14, 20 06 3:13 PM 42 Principles of Air Quality Management, Second Edition Because nonferrous metals are used to form electrical connections in electronic equipment, corrosion of such connections... “Smoking only” conditions had a death rate of 123 per 100,000 person years When cigarette smoking was present in addition to asbestos exposure, the death rate climbed to over 600 per 100,000 person years © 20 07 by Taylor & Francis Group, LLC 7099_book.fm Page 36 Friday, July 14, 20 06 3:13 PM 36 Principles of Air Quality Management, Second Edition TABLE 2. 5 Synergism of Asbestos and Smoking Group Control... of the guard cells determines the pore diameter and regulates the rate of gas exchange for CO2 and H2O It is through these © 20 07 by Taylor & Francis Group, LLC 7099_book.fm Page 38 Friday, July 14, 20 06 3:13 PM 38 Principles of Air Quality Management, Second Edition stomata that pollutant gases enter and react with the tissues of the leaf The ambient temperature, humidity, and carbon dioxide levels... Germany The implication of acidic deposition of some type is, in part, a result of the fact that decline of conifers is © 20 07 by Taylor & Francis Group, LLC 7099_book.fm Page 39 Friday, July 14, 20 06 3:13 PM Effects of Air Pollution 39 associated with increasing altitude Mountain regions are more likely to experience acidic fogs or cloud droplets for over one-third of the year Leaching of the nutrients from... limestone-based friezes and sculptures caused by acidic gases © 20 07 by Taylor & Francis Group, LLC 7099_book.fm Page 41 Friday, July 14, 20 06 3:13 PM Effects of Air Pollution 41 FIGURE 2. 5 Damage to limestone-based friezes caused by acidic gases Metal Corrosion The corrosion of metal in industrialized areas represents one of the most ubiquitous effects of atmospheric pollutants When iron-based metals... consciousness) consist of ketones, aliphatic alcohols, and double-bonded or “ether” types of organic compounds THE LUNGS Of all of the body organs, the lungs are the most quickly affected by air contaminants This is because the lungs are in constant contact with the environment Also, the lungs have a surface area of 70–100 m2, as opposed to the skin, at 2 m2, or the intestinal tract, at about 10 m2 This is an... particles down to the 0.5 µm range Particles smaller than 0.05 µm will be exhaled When speaking of particle size, the aerodynamic particle size is the reference, not the physical particle size © 20 07 by Taylor & Francis Group, LLC 7099_book.fm Page 32 Friday, July 14, 20 06 3:13 PM 32 Principles of Air Quality Management, Second Edition Sinuses Nasal cavity Adenoids Tonsils Tongue Pharynx Epiglottis Larynx... air pollutant A well-documented case of such a teratogenic effect is that of the birth defects found in children of women who ingested thalidomide-containing sleeping pills in the early 1960s This effect was noted only when the pregnant women took thalidomide © 20 07 by Taylor & Francis Group, LLC 7099_book.fm Page 37 Friday, July 14, 20 06 3:13 PM Effects of Air Pollution 37 on the 12th day following... alveoli, or tiny air sacs, may lose their elasticity as a result of the repeated impact of the particles and of the scarring action of gases, paints, or solvents © 20 07 by Taylor & Francis Group, LLC 7099_book.fm Page 33 Friday, July 14, 20 06 3:13 PM Effects of Air Pollution 33 Emphysema is one result of this damage There are approximately 20 0 million alveoli in the average lung; however, they do not... presence of moisture, acid aerosols, or acid precipitation The reaction of sulfuric acid with carbonate building stones results in the formation of CaSO3 · 2H2O and CaSO4 · 2H2O (gypsum), both of which are soluble in water These effects are not limited to the surface of the material, as water transports acids into the interior of the stone The soluble salts produced by this process may precipitate . 7099_book.fm Page 27 Friday, July 14, 20 06 3:13 PM © 20 07 by Taylor & Francis Group, LLC 28 Principles of Air Quality Management, Second Edition BASIC PRINCIPLES OF TOXICOLOGY A. regulated under the Clean Air Act, except lead. 7099_book.fm Page 23 Friday, July 14, 20 06 3:13 PM © 20 07 by Taylor & Francis Group, LLC 24 Principles of Air Quality Management, Second Edition . (<14 years of age) 20 Athletic activities 7 Total 52. 5 7099_book.fm Page 22 Friday, July 14, 20 06 3:13 PM © 20 07 by Taylor & Francis Group, LLC Effects of Air Pollution 23 Indeed,