Effects of Air Pollution

   

 

 
 

In this chapter you will learn:

bullet Why the study of health effects of air pollution is important?
bullet In how many ways can the effects be categorized into? Explain them.
bullet What are the various effects of criteria pollutants?
bullet What are the ill-effects of various chemicals on humans, plants and animals?
bullet What are heavy metals and explain the effects of them?
bullet What is the procedure followed in the calculation of diameters?
bullet What is web screening interface?

Every year, some 64,000 people may die prematurely from cardiopulmonary causes linked to particulate air pollution, according to an analysis conducted by NRDC. In the most polluted cities, lives are shortened by an average of one to two years. The following table gives an idea of the numbers involved in terms of the early deaths that can be attributed to pollution, in various forms.

U.S. City # of Early Deaths
Los Angeles 5873
New York 4024
Chicago 3479
Philadelphia 2599
Detroit 2123
Source: Air and Atmosphere
 

The Research Program at the Health Effects Institute (HEI)  has addressed many important questions about the health effects of a variety of pollutants, including carbon monoxide, methanol, diesel exhaust particles, nitrogen oxides, and ozone. To read about the ongoing research in these areas Click Here.
 
The study of the health effects of air pollution becomes imperative because depending on which air toxics an individual is exposed to, these health effects can include damage to the immune system, as well as neurological, reproductive (e.g., reduced fertility), developmental, and respiratory problems. The susceptibility of certain population groups to the toxic or non-toxic exposures, such as the elderly and children has to be given special consideration. Moreover air pollution, induces early fatigue, and effectively an overall reduction in efficiency and potential even in the otherwise healthy human beings. This can slacken the progress of a nation, its economy and commerce. Thus, the government spends voluminous amounts of money and carries out extensive research in agencies such as the Environmental Protection Agency, to understand the implications of pollution on human health and take appropriate corrective measures.
 
 

Why study health effects?

     An average person breathes 22,000 times a day and takes in 16 kg of air each day, which implies that individuals cannot live without air for more than five minutes. The purpose of this section is to review and discuss the effects of different air pollutants covered in the course. Contaminated air is a major culprit in most of the health effects associated with humans, animals, plants, microbes or other living matter. Damage to materials is also important while studying the effects.

 The effect of an air pollutant is a measurable or perceivable detrimental change. These effects could be synergistic, additive, potentate or antagonistic. The explanation of these terms is as follows:
 
 

Synergistic Combined effect of pollutants is worse than the simple sum of effects of individual pollutants
Additive Combined effect of pollutants is the same as the sum of effects of  individual pollutants
Potentate Toxic substance made worse by presence of non toxic substance
Antagonistic Effect of toxic substance lessened by presence of non-toxic substance.
 
 

    The precise effect of pollutants on health is virtually difficult to obtain, because individual differences in humans are significant. The effects depend on the genetic make - up, health, history of exposure, preconditioning and pollutant reaction time. The health studies are generally conducted to develop cause and effect  relationships.
 
 

How effects are studied?

The studies can be classified into three groups:

1. Human Exposure Studies:

These are based on the occupational or accidental exposures resulting in adverse effects. The studies also include subjects exposed to atmospheric pollutants in uncontrolled conditions. For example, truck drivers, traffic policemen, and individuals working in toll booths are used for determining cause and effect relationships.
Data collected from major air pollution episodes are used to establish a relationship between air pollution and reported diseases.

To visit the US EPA's Human Studies Division, page, Click Here.

2.   Laboratory Research/ Animal Studies:

This is conducted on animals or cells or biochemical systems. Actual exposure experiments are carried out. Different types of animals are critically studied under controlled conditions of concentrations and dosages. This provides immense information regarding the mode of various pollutants and their effects. Statistical analysis is rigorously used. The problem, however is that the extrapolation of these results to the human population is not precise. Moreover, one can only test one cause and effect relationship at a time.

3. Epidemiological Studies:

In epidemiological studies, the relationship between the distribution of specific diseases in a human population and possible causes are determined. The studies focus on communities. A typical study uses hospital records, morbidity records and mortality records. To avoid misinterpretation, the population under study must be carefully observed for smoking habits, occupational exposures and any other factor that might prejudice the results of the study. The studies are not repeatable and often have no control over timing and other variables.

A typical epidemiological study involves the collection, compilation and analysis of data such as the kind illustrated in the table below which was taken from an epidemiological study of the lung cancer mortality rates in women.

 
Source : US EPA document
http://www.epa.gov/nceawww1/ets/pdfs/appendc.pdf

 

Effects of Criteria Pollutants

Acute and chronic effects have been documented from the exposure of sulfur dioxide, particulate, ozone and nitrogen dioxide. CO has acute effects only. The effects of lead are chronic in nature at ambient levels.

1. Sulfur dioxide (SO2) :

Humans:

SO2 is an irritant gas which can easily get oxidized to sulfur trioxide and in the presence of water, these can form sulfurous and sulfuric acid. The health problems related to the mucous membrane and respiratory tract are due to sulfate aerosols. Significant portions of inhaled SO2 is removed in the mouth, throat and nose because of solubility of SO2 in watery fluids. Healthy individuals could experience sore throat, cough, shortness of breath and fatigue. Chronic effects of SO2 include increased probabilities of bronchitis,  "colds" of long duration and suppression of immune system. The London smog of December 1952, that resulted in 4000 deaths is a real example of the extreme hazard caused by SO2.
Plants:
SO2 produces two types of injury on leaves and plants - acute and chronic depending on concentration and period of exposure. The acute injury is characterized by the killing of marginal or interveinal areas of the leaf. Chronic injury is caused by the slow, long continued absorption of sub lethal amounts of  gases.
Materials:
SO2 absorbed by leather is converted to H2SO4 which deteriorates the leather. Deposition of sulfurous and sulfuric acids formed during the exposure on the metallic parts of equipment, building roofs, etc. results in corrosion which in turn results in heavy economic losses. SO2 can tarnish silver and copper contacts with sulfide films.
Paints contain a pigment and a vehicle, which enhance the attractiveness of the surface. However SO2 can damage the protective covering and expose the underlying layer to attack.
2. Hydrocarbons :

Humans:

The health effects of hydrocarbons have been noted in occupational exposures to tetra methyl lead, benzene, etc.
Hydrocarbon vapors can cause health effects. Inhaling formaldehyde can cause irritation. It is a major contributor to eye and respiratory irritation caused by photochemical smog.
Plants:
Ethylene causes injury to the leaves of sensitive plants. Effects are epinasty, chlorosis, curling, leaf abscission and growth retardation.

However, hydrocarbon is not a criteria pollutant, because, it  is predominant only during disasters such as photochemical smog, etc.

3. Ozone :

Humans :

Ozone is produced by natural and manmade volatile organic compounds (VOCs). Naturally occurring VOCs don't produce enough ozone to cause substantial adverse effects. In fact the atmospheric ozone helps in preventing harmful ultra violet rays from reaching the earth's surface.
Ozone and other oxidants may cause an irritant action in the respiratory tract reaching even deeper than SO2. Ozone disturbs the biochemical balance in the lung tissue by shifting the enzyme activity, chemical activity and cellular activity. Healthy individuals may respond to ozone by decreasing the volume of air brought into the lungs at concentrations of 0.1 to 0.15 ppm. Young children, aged or sick people are at a greater risk to adverse health effects of ozone than others. Other acute effects are cough and chest pain, eye irritation, headaches and asthma attacks. Ozone and other oxidants may cause at least temporary physiological and pathological changes in humans.
Chronic effects include losses in immune system functions, accelerated aging and increased susceptibility to other infections.
Plants:
Ozone causes more plant damage in the US than any other air pollutant. Ozone concentrations below 0.2 ppm can be phytotoxic and can cause flecks on the upper surfaces, premature aging and suppressed growth. Higher concentrations i.e. above 0.2 ppm can cause leaf bleaching, necrosis and bleaching.
In general it can damage forests and crops and be aesthetically displeasing, resulting in heavy economic losses.
Materials:
Ozone attacks the double bonds in the hydrocarbon polymer compounds, used in rubber. The side walls of the tyres and various forms of electrical insulation are especially affected. The degree of damage depends upon the nature of elastometric compound, elastometric stress, exposure duration, ozone concentration, rate of ozone contact with material and temperature. In fact tyre manufacturers add a special anti - ozone compound to all tyres sold in areas having a high ozone content. Ozone also fades fabrics.
To read the EPAs fact sheet on the health and environmental effects of ground level ozone Click Here.

4. Nitrogen Dioxide:

Humans :

The direct acute effects of nitrogen dioxide are damages to the cell membranes in the lung tissues and constriction of the lungway passages. The indirect effects include edema or a filling of the intercellular spaces with fluid. Nitrogen dioxide can cause occupational diseases. Manufacture of nitric acid, exposure of farmers to silage, that has had high nitrate fertilization, and electric arc welding. Mining, where nitrogen compounds are used as explosives, is also an example. Eye and nasal irritation and pulmonary discomfort are also common between concentrations between 15 to 25 ppm.
Plants :
Nitrogen dioxide causes growth retardation and leaf bleaching in plants.
Material :
Nitrogen dioxide causes fading of textile dyes.
5. Carbon monoxide :

Humans :

Carbon monoxide has a great affinity for the hemoglobin in the blood and combines with blood to form carboxyhemoglobin.  This reduces the ability of hemoglobin to carry oxygen to the body tissues. The effect of carbon monoxide intoxication is similar to that of anemia or hypoxia. Most of the low level CO exposures affect the central nervous system. A possible explanation for this is the reduction of O2 supply to the brain. CO is highly toxic above 1000 ppm and may be responsible for heart attacks and a high mortality rate, especially in the metropolitan areas, where CO abounds. Under acute conditions, it may result in death.
Under ambient conditions, CO intoxication is likely to aggravate existing conditions. Behavior is not significantly impaired by concentrations of carbon monoxide, which are below NAAQS. The new born and unborn are also affected by carbon monoxide. The ambient levels in highly polluted urban areas are associated with lower birth weight and increased death of newborns.
The principal reason for controlling carbon monoxide emissions is to protect the health of the unborn, newborn, aged, and infirm.
6. Lead :

Humans :

In urban atmospheres, lead is emitted chiefly from automobiles. It can cause gastro intestinal damage, weakness, loss of appetite and vomiting. It can damage the kidney and the liver.
Pre- school children and women of child bearing age are at risk due to high exposure of lead. The lead exposure could cause abnormalities in fertility and pregnancy and retard the mental development in children.
Schwartz and Pitcher (1989) pointed out that removing lead from gasoline in the US has apparently reduced the mean blood level of the population by over 50%.
Animals :
Animals have sudden convulsions, paralysis of the digestive tract. Cattle experience the nervous symptoms like grinding of teeth and rapid chewing of cud. Horses have a complete loss of appetite, lethargy and death.

To read about the effects of lead poisoning in children go to http://www.epa.gov/iaq/pubs/lead.html

For additional information on lead, go to the OSHA web site on Lead at http://www.osha-slc.gov/SLTC/lead/index.html

 7. Particulate Matter:

Humans :

Generally particles which are greater than or equal to 10 micrometers in size collect in the upper part of the respiratory tract, those between 1 to 10 micrometers in size collect in the middle part of the respiratory system i.e. the tracheobronchial region, while the particles with a size of less than 1 micrometer collect in the remote portions of the lungs - the air sacs (or alveoli). Particles with a diameter of to 1 micrometer, can be captured by the  phagocytes and eliminated. The particles with diameters of 1/2 micrometer or less float in the air sac and are expelled with the next breath or two.  Nasal hair and warm, humid conditions of nasal passages act together to remove particles. Particles collect moisture as they move through moist air of upper respiratory region, making them heavier and causing them to strike walls of throat, nose etc. They are eliminated by sneezing, coughing, nose blowing, and spitting, or by the digestive system.
  However if the particles are larger than that, they attach themselves to the respiratory tract or skin, etc. and cause mild to severe health effects. Small particles can adsorb sulfur dioxide and with water form acid containing particles which irritate the respiratory system and damage the cells that line the system. For example, the naturally produced pollen can be especially irritating to some individuals. They may suffer from hay fever or asthma. At times bronchitis, bronchial asthma and dermatitis are also probable health effects.
Specific dust particles, cause respiratory diseases such as silicosis, asbestosis, and others.
Plants and Animals :
Particles such as sulfates and nitrates interact with moisture on leaves. The result is a build up of acid which burns holes in leaves. Animal feed, either raw vegetation or processed feed, can convey or absorb particulate pollutants, thus rendering the feed unusable or unsafe. Particulate matter may be either harmful, harmless, or beneficial to plants. Particulate matter may either absorb light, scatter light, or reflect light, resulting in decreased visibility, and reduction of light available for photosynthesis.   Particulate matter can also affect precipitation patterns.
Millions of dollars are spent each year to clean items soiled by suspended particulate matter.

 

To read the EPA's fact sheet on the health and environmental effects of particulate matter Click Here.
 

To summarize these effects in a manner presented in a US EPA document, refer the following table:


Source: http://www.epa.gov/airprogm/oar/sect812/appen_d.pdf
 

Effects of Various Pollutants

 Certain individuals in the general population are affected more than the rest of the population. They include, the elderly population, children, (To see the EPA's "Children's Health Protection" program page, Click Here) pregnant women and handicapped individuals.

The health effects of criteria and hazardous air pollutants are significantly different. Lead is an exception in this discussion. The criteria pollutants have a threshold dose below which there are no known adverse effects and are not bioaccumulated in tissues. See the page on Criteria Pollutants for more information on them.

Hazardous air pollutants are too many and may target many organs in the body. The effects of HAPs occur after long latent period. A complete list of the 189 Hazardous air pollutants has been given in Appendix C. Also complete information on each of these HAPs can be read from the EPA's Health Effects Notebook for Hazardous Air Pollutants, by Clicking Here.
 
Also, the Integrated Risk Information System (IRIS), prepared and maintained by the U.S. Environmental Protection Agency (U.S. EPA), is an electronic data base containing information on human health effects that may result from exposure to various chemicals in the environment. This provides easy access to a lot of information on the health effects of a wide range of pollutants. Click Here to visit IRIS.

Sources of Common Contaminants and Their Health Effects

Common Sources 
Contaminants 
Potential Health Effects 
Household Items, such as Batteries, Thermometers, and Paints  mercury Toxic to kidneys.  

Can cause eye and skin irritation; chest pain; tremor; fatigue; weakness. 

Car Radiators and De-icing Agents  ethylene glycol  Can cause abdominal pain; vomiting; weakness; dizziness; central nervous system depression. 
Photocopy Machines  chromium Toxic to kidneys; potential human carcinogen. 
Dry Cleaning Agents and Degreasers  trichloroethane and trichloroethylene  Central nervous system depression: decreased alertness, headaches, sleepiness, loss of consciousness.  

Kidney changes: decreased urine flow, swelling (especially around eyes), anemia.  

Liver changes: fatigue, malaise, dark urine, liver enlargement. 

Herbicides for Vegetation Control  chlorophenoxy compounds; 2;4- dichlorophenoxyacetic acid  Chloracne, weakness or numbness of arms and legs, long-term nerve damage. 
dioxin  Dioxin causes chloracne and may aggravate pre-existing liver and kidney disease. 
Pesticides chlorinated ethanes; DDT; lindane  Acute symptoms of apprehension, irritability, dizziness, disturbed equilibrium, tremor, and convulsions. 
Cyclodienes (aldrin; chlordane; dieldrin; endrin); chlorocyclohexanes  Acute symptoms of apprehension, irritability, dizziness, disturbed equilibrium, tremor, and convulsions.  

Liver toxicity and permanent kidney damage.  

Chlorocyclohexanes can cause anemia. 

Organophosphate: diazanon; dichlorovos; dimethoate; trichlorfon; malathion; methyl parathion; parathion  

carbamate: aldicarb; baygon; zectran 

All cause a chain of internal reactions leading to neuromuscular blockage.  

Acute symptoms include headaches, fatigue, dizziness, increased salivation and crying, profuse sweating, nausea, vomiting, cramps, diarrhea, tightness in the chest, and muscle twitching. 

Electrical Transformers and Other Industrial Uses  polychlorinated biphenyls (PCBs)  Various skin ailments, including chloracne.  

May cause liver toxicity.  

Carcinogenic to animals. 

Commercial Solvents  benzene; ethyl benzene; toluene; xylene  Benzene suppresses bone marrow function, causing blood changes; chronic exposure can cause leukemia.  

Central nervous system depression: decreased alertness, headaches, sleepiness, loss of consciousness.  

Defatting dermatitis. 

carbon tetrachloride; chloroform; ethyl bromide; ethyl chloride; ethylene dibromide; ethylene dichloride; methyl chloride; methyl chloroform; methylene chloride; tetrachloroethane; tetrachloroethylene; trichloroethylene; vinyl chloride  Central nervous system depression: decreased alertness, headaches, sleepiness, loss of consciousness.  

Kidney changes: decreased urine flow, swelling (especially around eyes), anemia.  

Liver changes: fatigue, malaise, dark urine, liver enlargement, jaundice. 

Various Commercial and Industrial Manufacturing Processes  arsenic; beryllium; cadmium; chromium; lead; mercury  All are toxic to kidneys. Decreased mental ability, weakness, headache, abdominal cramps, diarrhea, and anemia. Also affects blood-forming mechanisms and the peripheral nervous system.  

Long-term exposure to lead can cause permanent kidney and brain damage.  

Cadmium can cause kidney and lung disease.  

Chromium, beryllium, arsenic, and cadmium have been implicated as human carcinogens. 

PCBs  Various skin ailments, including chlor acne; may cause liver toxicity; carcinogenic to animals. 
Chemical Manufacturing  benzene; ethyl benzene; toluene; xylene  Benzene suppresses bone marrow function, causing blood changes; chronic exposure can cause leukemia.  

Central nervous system depression: decreased alertness, headaches, sleepiness, loss of consciousness.  

Defatting dermatitis. 

Steel and Glass Manufacturing  chromium; lead; mercury  All are toxic to kidneys. Lead causes decreased mental ability, weakness, headache, abdominal cramps, diarrhea, and anemia. Also affects blood-forming mechanisms and the peripheral nervous system.  

Long-term exposure to lead can cause permanent kidney and brain damage.  

Chromium has been implicated as a human carcinogen. 

Chrome Plating Operations  chromium Toxic to kidneys; potential human carcinogen. 
 
Source : The US EPA Superfund Emergency Program
http://www.epa.gov/oerrpage/superfund/programs/er/hazsubs/sources.htm

QUESTIONS

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Why the study of health effects of air pollution is important?

bullet

What is a major culprit in most of the health effects?

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In how many ways can the effects be categorized into? Explain them.

bullet

How are the studies of health effects classified?

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What are the various advantages and disadvantages of studies of health effects?

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What analysis is rigorously used in laboratory research/ animal studies?

bullet

What is exactly epidemiological studies?

bullet

What are the various effects of criteria pollutants?

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What is the chemical causing health problems to mucous membrane and respiratory tract?

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Give an example for the hazard caused by SO2?

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Differentiate between acute injury and chronic injury?

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What does SO2 do with silver and copper contacts with sulfide films?

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What are the ill-effects of formaldehyde?

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What are the ill-effects of ethylene?

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Is hydrocarbon a criteria pollutant or not? Explain.

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What are the sources of ozone?

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What is the use of atmospheric ozone?

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What are the ill-effects of ozone on humans?

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What are the ill-effects of ozone on plants and materials?

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What are the ill-effects of NO2 on humans?

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What are the ill-effects of NO2 on plants and materials?

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What are the ill-effects of CO on humans?

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What is the major source of lead?

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What are the ill-effects of lead?

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Explain the terms PM2.5 and PM10?

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What are the ill-effects of particulate matter on humans, plants and animals?

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List the sources and effects of at least 20 HAPs?

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Explain the terms "dose" and "receptor"?

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What are the two major parameters in the calculation of diameters?

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Give an equation for calculating geometric standard deviation.

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What is Count Median Diameter?

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What are the two web pages of web screening interface?

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What are the system requirements to execute the screening interface?

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How a web screening interface be accessed?

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State any 2 case studies to provide the evaluation techniques of screening web interface.

 

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