Many sources of indoor air pollution are present in our homes and workplaces, and even at low levels, they can cause a wide variety of health problems. Certain pollutants can cause breathing problems and some people experience dizziness, headaches, burning eyes, aching throats or fatigue. Other pollutants can cause allergies, asthma, or even more serious chronic illnesses including respiratory disease. And recent studies have shown that tens of thousands of people suffer the risk of increased mortality from exposure to fine particulate matter, which is now thought to play a role in chronic obstructive pulmonary disease (COPD) and even heart disease.

Though children and the elderly are the most vulnerable to the health effects of poor indoor air quality, virtually everyone is affected at some level as indoor air pollutants are so common. Newer homes and offices have airtight ventilation systems that foster bacterial growth and the accumulation of chemical and other pollutants, while older buildings have high levels of chemicals and even heavy metals such as lead in the indoor air.

Millions of people inhale too much carbon monoxide, and a host of other airborne hazards such as formaldehyde, chlorine, benzene, lead, arsenic, hydrogen fluoride, hydrogen sulfide, sulfuric acid, nitric acid, and pesticides. With each breath of polluted air, the lung's tissues are damaged slightly and this accumulates over time. Young people exposed to high levels of pollutants in their homes for years are at serious risk to develop health problems as they age. And the elderly are especially susceptible to serious problems as their lung capacity tends to already be diminished.

According to the American Lung Association, air pollution may inflict annually between $40 and $50 billion in health costs and cause around 120,000 premature American deaths. And it is estimated that up to 20% of all Europeans suffer from asthma due to indoor air pollution from a wide variety of toxins ranging from tobacco smoke to volatile organic compounds. In addition a significant portion of all cancers in the U.S. and Europe are attributed to airborne pollutants. Even without outdoor exposure, this pollution collects inside our homes and workplaces, making it crucial that steps are taken to mitigate the problem.

Illnesses/Diseases affected by poor indoor air quality

·         Asthma

Some people are born with a predisposition toward developing asthma. However, what actually triggers the disease can vary from person to person. Common triggers include environmental tobacco smoke, air pollution, pollen, allergens from animals and insects, abrupt weather changes, biological contaminants such as mold, and viral infections.

Studies show that children whose parents smoke are twice as likely to develop asthma as children of nonsmoking parents. Also, children whose mothers smoked during pregnancy tend to be born with smaller airways, which greatly increases their chances of developing the disease.

Far too many Americans -- about 20 million people -- are intimately acquainted with the symptoms of an asthma attack. When asthma strikes, your airways become constricted and swollen, filling with mucus. Your chest feels tight -- you may cough or wheeze -- and you just can't seem to catch your breath. In severe cases, asthma attacks can be deadly. They kill 5,000 people every year in the United States.

Asthma is a chronic, sometimes debilitating condition that has no cure. It keeps kids out of school (for a total of 14 million lost school days each year, according to the Centers for Disease Control) and sidelines them from physical activity. Employers lose 12 million work days every year when asthma keeps adults out of the workplace. The disease is also responsible for nearly 2 million emergency-room visits a year.

Understanding what might trigger an asthma attack helps asthma sufferers keep their disease in check. Sometimes it's as simple as avoiding dust, tobacco smoke or cockroach droppings. But what if the air outside your home is filled with asthma triggers?

In recent years, scientists have shown that air pollution from cars, factories and power plants is a major cause of asthma attacks. And more than 159 million Americans -- over half the nation's population -- live in areas with bad air. A research study published in 2002 estimated that 30 percent of childhood asthma is due to environmental exposures, costing the nation $2 billion per year. And studies also suggest that air pollution may contribute to the development of asthma in previously healthy people. 

Present results provide new evidence of the relation between workplace exposure to indoor molds and adult-onset asthma.

Air Pollutants that Trigger Asthma

• Ground Level Ozone: A toxic component of smog, ozone triggers asthma attacks and makes existing asthma worse. It may also lead to the development of asthma in children. Ozone is produced at ground level when tailpipe pollution from cars and trucks reacts with oxygen and sunlight. Ground level ozone is a big problem in cities with lots of traffic, such as Los Angeles, Houston and New York City. In 2004, according to the American Lung Association, 136 million people lived in areas that violated ozone air quality standards.
• Sulfur Dioxide (SO2 ): A respiratory irritant associated with the onset of asthma attacks, sulfur dioxide is produced when coal and crude oil are burned. Coal-fired power plants, particularly older plants that burn coal without SO2 pollution controls, are the worst SO2 polluters. One in five Americans lives within 10 miles of a coal-fired power plant. Oil refineries and diesel engines that burn high-sulfur fuel also release large amounts of SO2 into the air.
• Particulate Matter: This term refers to a wide range of pollutants -- dust, soot, fly ash, diesel exhaust particles, wood smoke and sulfate aerosols -- which are suspended as tiny particles in the air. Some of these fine particles can become lodged in the lungs and could trigger asthma attacks. Studies have shown that the number of hospitalizations for asthma increases when levels of particulate matter in the air rise. Coal-fired power plants, factories and diesel vehicles are major sources of particulate pollution. Around 81 million people live in areas that fail to meet national air quality standards for particulate matter.
• Nitrogen oxide (NOx): A gas emitted from tailpipes and power plants, nitrogen oxide contributes to the formation of ground-level ozone and smog. It also reacts with other air pollutants to form small particles that can cause breathing difficulties, especially in people with asthma.

Mayo Clinic researchers recently released study data showing children who lived near major highway or railroad intersections have higher diagnoses of asthma.

·         Allergies

ALLERGY AND HYPERSENSITIVITY

Hypersensitivity reactions can best be portrayed as exaggerated immune responses to foreign organic or inorganic substance (antigens). Allergic reactions are highly individualized. In other words, exposure conditions that elicit an allergic response in certain people may have no effect on other similarly exposed individuals.

Multiple factors influence human capacity to mount an allergic response, the most common being genetic makeup. Much of our understanding about allergies comes from studying human reaction to natural antigens such as pollen, fungi, bacteria, house dust, and animal dander. Examples of allergies key to indoor air considerations include both antibody-mediated (asthma and rhinitis) and cell-mediated (hypersensitivity pneumonitis) types of hypersensitivity.

Asthma, allergic rhinitis, and common allergies are attributed to indoor air pollutants. An estimated 40 million Americans suffer from some type of allergic disease.[13] In the work setting, these diseases are a frequent cause of low productivity and absenteeism.

During the past two decades, there also has been an alarming trend of increasing asthma mortality in the general population. These reactions are learned immune regimens; that is, previous exposure to an antigen always precedes an allergic response. Responses are produced as a result of an abnormal release of a potent vasoactive substance such as histamine, heparin, serotonin, esterase, prostaglands, and leukotrienes following interaction of allergen with specialized host cells, such as mast cells and basophils.[14] These biologically active substances can cause two phenomena within the host:
1. Smooth muscle contraction in nasal passages, dilation of small blood vessels, and continued inflammatory factor release in nasal tissue, resulting in itchy eyes and nasal irritation/congestion (rhinitis)

2. Immediate and/or delayed smooth muscle contraction in pulmonary bronchi resulting in a reversible narrowing of the airways (asthma).

Exposure to soluble high-molecular-weight antigens such as peptides, proteins, glycoprotein, and polysaccharides can lead to allergies such as asthma and rhinitis. When combined with a suitable protein carrier, however, even low-molecular-weight chemicals and metals can elicit an allergic response.

·         COPD

Pollutants that exist within homes and buildings also may be harmful to persons with COPD or asthma. Many older persons spend up to 90 percent of their time indoors, often at home. Common indoor environmental hazards that may trigger COPD and asthma attacks include tobacco smoke (direct and second-hand smoke), animal dander, dust mites and cockroaches, mold, dust and pollen. Other sources of indoor air pollution that may trigger a COPD or asthma attack include combustion products of oil, gas, kerosene and coal, and building materials and furnishings made of pressed wood products. Pesticides, household cleaning products and substances with irritating odors also may exacerbate these diseases.

·         Cancer

A number of indoor contaminants, such as asbestos, radon, tobacco smoke, and benzene, are known human carcinogens. Other indoor contaminants, such as certain chlorinated solvents, polycyclic aromatic hydrocarbons, aldehydes, and pesticides, are considered likely to cause cancer in humans.

The National Academy of Sciences, in its latest report on radon health science (NAS 1998), concluded that radon is the second leading cause of lung cancer in the country. NAS has estimated that about 12 percent of the lung cancer deaths in the United States are linked to radon. They calculate the number of lung cancer cases attributable to radon exposure to range from 15,000 to 22,000 annually.

Environmental tobacco smoke is estimated to cause an additional 3,000 lung cancer deaths in nonsmokers each year (U.S. EPA 1992). Other forms of cancer have also been found to be associated with indoor pollutants (e.g., leukemia with benzene; bladder cancer with ETS).

·         Reproductive and Developmental Effects

During the period 1991 to 1994, almost 900,000 children had elevated blood levels, which can cause a variety of developmental delays, including effects on intelligence quotient (IQ); vision, hearing and stature deficits; and learning disabilities (U.S. DHHS 1997a). Several studies indicate that common indoor pollutants such as lead and ETS can also impair fetal development. A California report estimates that 9,700 to 18,600 cases of low birth weight in infants are caused each year by ETS (NCI 1999).

Many other environmental agents, including a number of chemicals commonly found indoors (e.g., tobacco smoke, some pesticides, lead and other heavy metals, alcohols, and plastic additives), are suspected of causing developmental toxicity in humans (U.S. EPA 1991a, NCI 1999). Endocrine disruptors (e.g., certain pesticides and plasticizers), which affect the normal function of sex and thyroid hormones, present a new area of concern for reproductive toxicity. Adverse effects on a developing child may result from exposure prior to conception in either parent, exposure during pregnancy, or post-natal exposure. These effects range from low birth weight to genetic diseases to lower IQs and infertility.

While the proportion of reproductive and developmental effects due to indoor environmental factors is currently unknown, the impact could be serious. Approximately 3 percent of newborn children have one or more significant malformations at birth. By age one, about 3 percent more are recognized to have serious developmental defects. Lifetime health-care costs for children born each year with birth defects are estimated to be more than $8 billion.

A study by researchers at Queensland University in Brisbane, Australia warns that women exposed to air pollution in urban areas during pregnancy have smaller fetuses than those in areas with cleaner air. This is the first study to show that air pollution affects fetal development.

The air pollution of concern is from urban areas, which tends to be mainly caused by automobile emissions, especially sulphur dioxide from diesel engines. Nitrogen dioxide and particulate matter from automobile engines are also included.

·         Other Health Effects

Indoor environments can cause or amplify many other health effects as well. The American Heart Association estimates that 35,000 to 40,000 cardiovascular deaths per year among nonsmokers can be attributed to ETS exposure (Taylor et al. 1991). Recent studies have shown that, compared to those who had not been exposed, ETS was associated with a 20 percent increase in the progression of atherosclerosis (hardening of the arteries) (Howard et al. 1998). Carbon monoxide (CO) poising associated with the improper use and maintenance of fuel-burning appliances kills more than 200 people per year in this country and results in about 10,000 admissions to hospital emergency rooms for treatment (U.S. CPSC 1997). An additional 600 to 700 accidental deaths from CO poisoning occur indoors from other sources, including automobiles (Cobb and Etzel 1991). The agent for Legionnaires' disease, a potentially deadly pneumonia which affects 10,000 to15, 000 people each year, is associated with cooling systems, whirlpool baths, humidifiers, food market vegetable misters, and other indoor sources, including residential tap water (EPA et al. 1994; U.S. DHHS 1997b). Effects associated with toxins from indoor fungi and bacteria range from short-term irritation to immunosuppression and cancer (EPA et al. 1994).

A new study investigated the association between short-term exposure to ambient fine particulate matter and the risk of stroke and found that even low pollutant levels may increase that risk. 

·         Multiple Chemical Sensitivity (MCS)
Because of varying sensitivity to airborne chemicals and irritants, individuals with heightened sensitivities may react to a particular indoor air quality problem while others display no ill effects. Symptoms that are limited to only one or a individuals can also occur when only their area contains the airborne pollutant. In other cases, complaints may be widespread. In addition to different degrees of reaction, an indoor air pollutant or problem can trigger different reactions in different people.

·         Ozone
According to the EPA some health effects of overexposure to ozone are decreases in lung function, aggravation of asthma, throat irritation and coughing, chest pain and shortness of breath, inflammation of lung tissue, and higher susceptibility to respiratory infection

·         What are the symptoms of particle exposure?

Even if you are healthy, you may experience temporary symptoms, such as irritation of the eyes, nose, and throat; coughing; phlegm; chest tightness; and shortness of breath.

If you have lung disease, you may not be able to breathe as deeply or as vigorously as normal, and you may experience coughing, chest discomfort, wheezing, shortness of breath, and unusual fatigue. If you have any of these symptoms, reduce your exposure to particles and follow your doctor's advice. Contact your doctor if symptoms persist or worsen. If you have asthma, carefully follow your asthma management plan when particle levels are high. Your doctor can help you develop a plan if you don't have one.

If you have heart disease, particle exposure can cause serious problems in a short period of time even heart attacks with no warning signs. So don't assume that you are safe just because you don't have symptoms. Symptoms such as chest pain or tightness, palpitations, shortness of breath, or unusual fatigue may indicate a serious problem. If you have any of these symptoms, follow your doctor's advice.

Over the past fifteen years an increasing number of studies have reported associations between the levels of PM in the air and adverse respiratory and cardiovascular effects in people (e.g., increases in daily mortality, illness, hospital admissions and emergency room visits). Scientists have observed these associations even at relatively low ambient levels that are prevalent in the U.S. and Western Europe. Research is currently underway to better understand the nature of the relationship between PM and disease - especially how PM affects human health.

The health effects of PM are likely to depend on several factors, including the size and composition of the particles, the level and duration of exposure, and age and sensitivity of the exposed person. Symptoms of exposure may include a sore throat, persistent cough, burning eyes, wheezing, shortness of breath, tightness of chest, and chest pain. PM may also trigger asthma or may lead to premature death, particularly in the elderly who have preexisting cardiovascular and respiratory diseases.

·         Health effects of Dust Mite Allergens

Mites are one of the major indoor triggers for people with allergies and asthma. Dust mite exposure can even cause asthma.

Chronic, ongoing exposure to dust mites at home can dramatically impact the health of people with asthma and those who are allergic or particularly sensitive to mites.  These allergens cause an immune system response, known as allergic rhinitis. A dust mite allergy can range from mild to severe. A mild case may cause an occasional runny nose, watery eyes and sneezing. In severe cases, the condition is ongoing, or chronic, resulting in persistent sneezing, cough, congestion, facial pressure or severe asthma attack.   People with asthma who are sensitive to mites face an increased risk of flare-ups or an asthma attack.

• Formaldehyde:  Children show up at clinics with cold and flu symptoms that never seemed to subside no matter how many times they are treated. Formaldehyde is also contained in vaccinations. The EPA lists formaldehyde as a human carcinogen. Formaldehyde is included on the list and can cause watery eyes, aburning sensations in the eyes and throat, nausea and difficulty in breathing in some humans exposed at elevated levels (above 0.1 parts per million). It is a carcinogen and can cause dermatitis, aggressive behavior, bronchial spasm and other medical conditions. The release of formaldehyde into the air may cause health problems, such as coughing; eye, nose, and throat irritation; skin rashes, headaches, and dizziness. Formaldehyde causes asthma, bronchitis, sinus infections, and headaches.  Formaldehyde is also a carcinogen, and it has been linked to leukemia.

Formaldehyde, a colorless, pungent-smelling gas, can cause watery eyes, burning sensations in the eyes and throat, nausea, and difficulty in breathing in some humans exposed at elevated levels (above 0.1 parts per million). High concentrations may trigger attacks in people with asthma. There is evidence that some people can develop a sensitivity to formaldehyde. It has also been shown to cause cancer in animals and may cause cancer in humans.

The U.S. Environmental Protection Agency (EPA) has released a draft assessment of the dangers of formaldehyde that finds that pregnant women, children, and asthmatics are particularly susceptible to the health effects of inhaling the chemical.

Formaldehyde was already a known carcinogen; the draft assessment just released by EPA adds information about its non-cancer effects, which include eye, nose, and throat irritation, decreased lung function, decreased immune system function, neurological damage, and reproductive damage.

• NO and NO2:  Causative for meningeal inflammation and headaches.

·         Swine Flu:  The symptoms of H1N1 (SO) flu resemble those of seasonal flu and include fever, cough, sore throat, body aches, headache, chills and fatigue. Some people have reported diarrhea and vomiting as well.

·         Benzene, a known carcinogen, can produce myeloid leukemia, Hodgkin's disease, and lymphomas. It is a poison by inhalation and a skin and eye irritant. Birth defects and adverse reproductive effects were found in animals exposed to benzene, and effects were seen at less than one part per million.

·         Carbon monoxide is an odorless, colorless gas that interferes with the distribution of oxygen to the body. Depending on the amount inhaled, this gas can impede coordination, worsen cardiovascular conditions, and produce fatigue, headache, confusion, nausea, and dizziness. Very high levels can cause death.

·         Nitrogen dioxide is a colorless, odorless gas that irritates the mucous membranes in the eye, nose and throat and causes shortness of breath after exposure to high concentrations. Prolonged exposure to high levels of this gas can damage respiratory tissue and may lead to chronic bronchitis.

·         Household cleaning agents, personal care products, pesticides, paints, hobby products, and solvents may be sources of hundreds of potentially harmful chemicals. Such components in many household and personal care products can cause dizziness, nausea, allergic reactions, eye/skin/respiratory tract irritation, and cancer.

• Air pollution is a heterogeneous, complex mixture of gases, liquids, and particulate matter. Epidemiological

studies have demonstrated a consistent increased risk for cardiovascular events in relation to both short- and long-term exposure to present-day concentrations of ambient particulate matter. Several plausible mechanistic pathways have been described, including enhanced coagulation/thrombosis, a propensity for arrhythmias, acute arterial vasoconstriction,

systemic inflammatory responses, and the chronic promotion of atherosclerosis. The purpose of this statement is to

provide healthcare professionals and regulatory agencies with a comprehensive review of the literature on air pollution

and cardiovascular disease. In addition, the implications of these findings in relation to public health and regulatory policies are addressed. Practical recommendations for healthcare providers and their patients are outlined. In the final section, suggestions for future research are made to address a number of remaining scientific questions. (Circulation. 2004;109:2655-2671.)

Over the last decade, however, a growing body of epidemiological and clinical evidence has led to a heightened concern about the potential deleterious effects of ambient air pollution on health and its relation to heart disease and stroke. Of special interest are several environmental air pollutants that include carbon monoxide, oxides of nitrogen, sulfur dioxide, ozone, lead, and particulate matter (“thoracic particles” [PM10] _10 _m in aerodynamic diameter, “fine particles”

[PM2.5] _2.5 _m, and “coarse particles” [PM10 to 2.5]). These pollutants are associated with increased hospitalization3 and mortality due to cardiovascular disease,4–6 especially

in persons with congestive heart failure, frequent arrhythmias, or both.7 The well-established causal associations between active and passive smoking with heart disease and stroke support the plausibility of an adverse effect of PM on the cardiovascular system

·         People with diabetes, heart failure, chronic obstructive pulmonary disease and inflammatory diseases such as rheumatoid arthritis are at increased risk of death when they are exposed to particulate air pollution, or soot, for one or more years, according to a study to be presented at the American Thoracic Society International Conference
The researchers compared this information with 12-month averages of PM10, a type of particulate matter air pollution that includes particles with a diameter of 10 micrometers or less than 0.0004 inches or one-seventh the width of a human hair.

The study found that for an increase of 10 micrograms/per cubic meter of PM10 over two years, the risk of dying was increased by:

32% for people with diabetes
28% for people with COPD
27% in people with congestive heart failure
22% for people with inflammatory disease such as rheumatoid arthritis or lupus

• Increasing numbers of children around the world are suffering from respiratory problems - coughing, wheezing and asthma attacks.

When all these measurements were concluded in La Plata at the end of 2006, thousands of pieces of data had to be compiled and correlated. It is possible to draw some notable conclusions from the columns of numbers and tables.
They show, for instance, that the different respiratory disease symptoms in the industrial areas included in the study affect between a quarter and a third of all children.

In the suburbs and in the countryside only half as many children tend to be affected and even in the city centre only around one or two per cent more children are affected than in the relatively unpolluted areas. The lung function of children from the industrial area was also significantly impaired. The researchers had not been expecting to find such a marked contrast.

• Mycotoxins from mold - Very little is currently known about acute idiopathic pulmonary hemorrhage among infants. This is a newly recognized problem and knowledge is expected to be evolving rapidly. In view of the severity of the problem, environmental controls to eliminate water problems and to reduce the growth of indoor molds are wise. Until more is known about the etiology of idiopathic pulmonary hemorrhage, prudence dictates that pediatricians try to ensure that infants under 1 year of age are not exposed to chronically moldy, water-damaged environments.

New evidence that indoor air pollution from toxigenic fungi may play a role in human illness has implicated that mycotoxins could have a much bigger role in chronic disease than was previously thought possible (CAST 2003).
Mycotoxins can be carcinogenic (causes cancer), teratogenic (causes birth defects), mutagenic (causes mutation or damage to genetic material), immunosuppressive (decreases the immune system), tremorgenic (causes tremors or damage to the central nervous system), hemorrhagic (causes bleeding), hepatotoxic (damages the liver), nephrotoxic (damages the kidneys) and neurotoxic (damages nerve tissue).

Human exposure to mycotoxins can occur by several ways, including ingestion, contact, and inhalation.

·         Health Effects of Environmental Tobacco Smoke

In 1992, EPA completed a major assessment of the respiratory health risks of ETS (Respiratory Health Effects of Passive Smoking: Lung Cancer and Other Disorders EPA/600/6-90/006F). The report concludes that exposure to ETS is responsible for approximately 3,000 lung cancer deaths each year in nonsmoking adults and impairs the respiratory health of hundreds of thousands of children.

Infants and young children whose parents smoke in their presence are at increased risk of lower respiratory tract infections (pneumonia and bronchitis) and are more likely to have symptoms of respiratory irritation like cough, excess phlegm, and wheeze. EPA estimates that passive smoking annually causes between 150,000 and 300,000 lower respiratory tract infections in infants and children under 18 months of age, resulting in between 7,500 and 15,000 hospitalizations each year. These children may also have a build-up of fluid in the middle ear, which can lead to ear infections. Older children who have been exposed to secondhand smoke may have slightly reduced lung function.

Asthmatic children are especially at risk. EPA estimates that exposure to secondhand smoke increases the number of episodes and severity of symptoms in hundreds of thousands of asthmatic children, and may cause thousands of non-asthmatic children to develop the disease each year. EPA estimates that between 200,000 and 1,000,000 asthmatic children have their condition made worse by exposure to secondhand smoke each year. Exposure to secondhand smoke causes eye, nose, and throat irritation. It may affect the cardiovascular system and some studies have linked exposure to secondhand smoke with the onset of chest pain.

Secondhand smoke has been classified as a Group A carcinogen by the U.S. Environmental Protection Agency (EPA), a rating used only for substances proven to cause cancer in humans. A study conducted in 2005 by the California EPA concluded that each year approximately 3,400 lung cancer deaths in nonsmoking adults are attributable to ETS. Exposure to secondhand smoke also causes eye, nose, and throat irritation. It may affect the cardiovascular system and some studies have linked exposure to secondhand smoke with the onset of chest pain. ETS is an even greater health threat to people who already have heart and lung illnesses.

Infants and young children whose parents smoke in their presence are at increased risk of lower respiratory tract infections (pneumonia and bronchitis) and are more likely to have symptoms of respiratory irritation like coughing, wheezing, and excess phlegm. In children under 18 months of age, passive smoking causes between 150,000 and 300,000 lower respiratory tract infections, resulting in 7,500 to 15,000 hospitalizations each year, according to EPA estimates. These children may also have a buildup of fluid in the middle ear, which can lead to ear infections. Slightly reduced lung function may occur in older children who have been exposed to secondhand smoke. In the United States, 21 million children live in homes where residents or visitors smoke in the home on a regular basis.

Children with asthma are especially at risk from ETS. The EPA estimates that exposure to ETS increases the number of asthma episodes and the severity of symptoms in 400,000 to 1 million children annually. Secondhand smoke may also cause thousands of non-asthmatic children to develop the disease each year.

·         Health Effects From Biological Contaminants

Some biological contaminants trigger allergic reactions, including hypersensitivity pneumonitis, allergic rhinitis, and some types of asthma. Infectious illnesses, such as influenza, measles, and chicken pox are transmitted through the air. Molds and mildews release disease-causing toxins. Symptoms of health problems caused by biological pollutants include sneezing, watery eyes, coughing, shortness of breath, dizziness, lethargy, fever, and digestive problems.

Allergic reactions occur only after repeated exposure to a specific biological allergen. However, that reaction may occur immediately upon re-exposure or after multiple exposures over time. As a result, people who have noticed only mild allergic reactions, or no reactions at all, may suddenly find themselves very sensitive to particular allergens.

Some diseases, like humidifier fever, are associated with exposure to toxins from microorganisms that can grow in large building ventilation systems. However, these diseases can also be traced to microorganisms that grow in home heating and cooling systems and humidifiers. Children, elderly people, and people with breathing problems, allergies, and lung diseases are particularly susceptible to disease-causing biological agents in the indoor air.

·         Health Effects of Combustion Products

Carbon monoxide (CO) is a colorless, odorless gas that interferes with the delivery of oxygen throughout the body. At high concentrations it can cause unconsciousness and death. Lower concentrations can cause a range of symptoms from headaches, dizziness, weakness, nausea, confusion, and disorientation, to fatigue in healthy people and episodes of increased chest pain in people with chronic heart disease. The symptoms of carbon monoxide poisoning are sometimes confused with the flu or food poisoning. Fetuses, infants, elderly people, and people with anemia or with a history of heart or respiratory disease can be especially sensitive to carbon monoxide exposures.

Nitrogen dioxide (NO₂) is a reddish-brown, irritating odor gas that irritates the mucous membranes in the eye, nose, and throat and causes shortness of breath after exposure to high concentrations. There is evidence that high concentrations or continued exposure to low levels of nitrogen dioxide increases the risk of respiratory infection; there is also evidence from animal studies that repeated exposures to elevated nitrogen dioxide levels may lead, or contribute, to the development of lung disease such as emphysema. People at particular risk from exposure to nitrogen dioxide include children and individuals with asthma and other respiratory diseases.

Particulates, released when fuels are incompletely burned, can lodge in the lungs and irritate or damage lung tissue. A number of pollutants, including radon and benzo(a)pyrene, both of which can cause cancer, attach to small particles that are inhaled and then carried deep into the lung. Particulates can cause eye, nose, throat, and lung irritation, and can increase respiratory problems, especially in those with preexisting medical conditions, such as cardiovascular illness and immune system diseases. Certain chemicals attached to the particles may cause lung cancer if they are inhaled. The risk of lung cancer increases with the length and amount of exposure. The health effects from inhaling particles depend on many factors, including the chemical makeup and size of the particles.

Sulfur dioxide irritates the eyes, nose, and the respiratory tract at low levels of exposure. At high levels, it causes the lung airways to narrow. This results in chest tightness, wheezing, or breathing problems.

POLYCYCLIC AROMATIC HYDROCARBONS (PAHs) - Lung, Stomach, Bladder,
and Skin Cancer, Nose, Throat and Eye Irritation

·         Health Effects of Household Chemicals

The ability of organic chemicals to cause health effects varies greatly, from those that are highly toxic, to those with no known health effect. As with other pollutants, the extent and nature of the health effect will depend on many factors including level of exposure and length of time exposed. Eye and respiratory tract irritation, headaches, dizziness, visual disorders, and memory impairment are among the immediate symptoms that some people have experienced soon after exposure to some organics. At present, not much is known about what health effects occur from the levels of organics usually found in homes. Many organic compounds are known to cause cancer in animals; some are suspected of causing, or are known to cause, cancer in humans.

·         Health Effects From Pesticides

Irritation to eye, nose, and throat; damage to central nervous system and kidney; increased risk of cancer.  Symptoms may include headache, dizziness, muscular weakness, and nausea. Chronic exposure to some pesticides can result in damage to the liver, kidneys, endocrine and nervous systems.

Both the active and inert ingredients in pesticides can be organic compounds; therefore, both could add to the levels of airborne organics inside homes. Both types of ingredients can cause the effects discussed in this document under "Household Products," however, as with other household products, there is insufficient understanding at present about what pesticide concentrations are necessary to produce these effects.

Exposure to high levels of cyclodiene pesticides, commonly associated with misapplication, has produced various symptoms, including headaches, dizziness, muscle twitching, weakness, tingling sensations, and nausea. In addition, EPA is concerned that cyclodienes might cause long-term damage to the liver and the central nervous system, as well as an increased risk of cancer.

There is no further sale or commercial use permitted for the following cyclodiene or related pesticides: chlordane, aldrin, dieldrin, and heptachlor. The only exception is the use of heptachlor by utility companies to control fire ants in underground cable boxes.

·         Health Effects of Exposure to Lead

Lead affects practically all systems within the body. At high levels it can cause convulsions, coma, and even death. Lower levels of lead can adversely affect the brain, central nervous system, blood cells, and kidneys.

The effects of lead exposure on fetuses and young children can be severe. They include delays in physical and mental development, lower IQ levels, shortened attention spans, and increased behavioral problems. Fetuses, infants, and children are more vulnerable to lead exposure than adults since lead is more easily absorbed into growing bodies, and the tissues of small children are more sensitive to the damaging effects of lead. Children may have higher exposures since they are more likely to get lead dust on their hands and then put their fingers or other lead-contaminated objects into their mouths. In adults, lead can increase blood pressure and cause fertility problems, nerve disorders, muscle and joint pain, irritability, and memory or concentration problems.

·         Health Effects of Sick Building Syndrome

A number of well-identified illnesses, such as Legionnaires' disease, asthma, hypersensitivity pneumonitis, and humidifier fever, have been directly traced to specific building problems. These are called building-related illnesses. Most of these diseases can be treated, nevertheless, some pose serious risks.

Sometimes, however, building occupants experience symptoms that do not fit the pattern of any particular illness and are difficult to trace to any specific source. This phenomenon has been labeled sick building syndrome. People may complain of one or more of the following symptoms: dry or burning mucous membranes in the nose, eyes, and throat; sneezing; stuffy or runny nose; fatigue or lethargy; headache; dizziness; fatigue; lethargy; nausea; irritability and forgetfulness; sinus congestion; chest tightness; shortness of breath; fever; chills; skin irritation. There is no single manner in which these health problems appear. In some cases, problems begin as workers enter their offices and diminish as workers leave; other times, symptoms continue until the illness is treated. Sometimes there are outbreaks of illness among many workers in a single building; in other cases, health symptoms show up only in individual workers.

In the opinion of some World Health Organization experts, up to 30 percent of new or remodeled commercial buildings may have unusually high rates of health and comfort complaints from occupants that may potentially be related to indoor air quality.

·         Many health effects are associated with biological contaminants:

Some may trigger allergic reactions, including hypersensitivity pneumonitis, allergic rhinitis, and some types of asthma. Allergic reactions occur only after repeated exposure to a specific biological allergen. However, that reaction may occur immediately upon re-exposure or after multiple exposures over time. As a result, people who have noticed only mild allergic reactions, or none at all, may suddenly find themselves very sensitive to particular allergens.

Infectious diseases, such as influenza, measles, tuberculosis, and chicken pox, are transmitted through the air.

Some molds and mildews can release disease-causing toxins. These toxins can damage a variety of organs and tissues in the body, including the liver, central nervous system, digestive tract, and immune system. Some diseases, like humidifier fever, can be traced to microorganisms that grow in home heating and cooling systems, although it is not certain whether the disease is an allergic reaction or a toxic response.

 Symptoms of exposure to biological contaminants include sneezing, watery eyes, coughing, shortness of breath, dizziness, lethargy, fever, and digestive problems. Children, elderly people, and people with breathing problems, allergies, and lung diseases are particularly susceptible to disease-causing biological agents in the indoor air.

·         Tuberculosis

The transmission of airborne infectious diseases is increased where there is poor indoor air quality^27,28. The rising incidence of tuberculosis is at least in part a problem associated with crowding and inadequate ventilation. Evidence is increasing that inadequate or inappropriately designed ventilation systems in health care settings or other crowded conditions with high-risk populations can increase the risk of exposure²⁹.

The incidence of tuberculosis began to rise in the mid 1980s, after a steady decline. The 1989 increase of 4.7 percent to a total of 23,495 cases in the United States was the largest since national reporting of the disease began in 1953, and the number of cases has continued to increase each year³⁰. Fresh air ventilation is an important factor in contagion control. Such procedures as sputum induction and collection, bronchoscopy, and aerosolized pentamidine treatments in persons who may be at risk for tuberculosis (e.g., AIDS patients) should be carried out in negative air pressure areas, with air exhausted directly to the outside and away from intake sources³¹. Unfortunately, many health care facilities are not so equipped. Properly installed and maintained ultraviolet irradiation, particularly of upper air levels in an indoor area, is also a useful means of disinfection³².

·         Legionnaires' Disease

A disease associated with indoor air contamination is Legionnaires' Disease, a pneumonia that primarily attacks exposed people over 50 years old, especially those who are immunosuppressed, smoke, or abuse alcohol. Exposure to especially virulent strains can also cause the disease in other susceptible populations. The case fatality rate is high, ranging from five to 25 percent. Erythromycin is the most effective treatment. The agent, Legionella pneumophila, has been found in association with cooling systems, whirlpool baths, humidifiers, food market vegetable misters, and other sources, including residential tap water³³. This bacterium or a closely related strain also causes a self-limited (two- to five-day), flu-like illness without pneumonia, sometimes called Pontiac Fever, after a 1968 outbreak in that Michigan city.

·         Allergic Reactions

A major concern associated with exposure to biological pollutants is allergic reactions, which range from rhinitis, nasal congestion, conjunctival inflammation, and urticaria to asthma. Notable triggers for these diseases are allergens derived from house dust mites; other arthropods, including cockroaches; pets (cats, dogs, birds, rodents); molds; and protein-containing furnishings, including feathers, kapok, etc. In occupational settings, more unusual allergens (e.g., bacterial enzymes, algae) have caused asthma epidemics. Probably most proteins of non-human origin can cause asthma in a subset of any appropriately exposed population³⁴.

The role of mites as a source of house dust allergens has been known for 20 years^34,35. It is now possible to measure mite allergens in the environment and IgE antibody levels in patients using readily available techniques and standardized protocols. Experts have proposed provisional standards for levels of mite allergens in dust that lead to sensitization and symptoms. A risk level where chronic exposure may cause sensitization is 2µg Der pI (Dermatophagoides pteronysinus allergen I) per gram of dust (or 100 mites /g or 0.6 mg guanine /g of dust). A risk level for acute asthma in mite-allergic individuals is 10µg (Der pI) of the allergen per gram of dust (or 500 mites /g of dust).

Controlling house dust mite infestation includes covering mattresses, hot washing of bedding, and removing carpet from bedrooms. For mite allergic individuals, it is recommended that home relative humidities be lower than 45 percent. Mites desiccate in drier air (absolute humidities below 7 kg.). Vacuum cleaning and use of acaricides can be effective short-term remedial strategies. One such acaracide, Acarosan, is registered with EPA to treat carpets, furniture, and beds for dust mites.

·         Hypersensitivity Pneumonitis

Another class of hypersensitivity disease is hypersensitivity pneumonitis, which may include humidifier fever. Hypersensitivity pneumonitis, also called allergic alveo-litis, is a granulomatous interstitial lung disease caused by exposure to airborne antigens. It may affect from one to five percent or more of a specialized population exposed to appropriate antigens (e.g., farmers and farmers' lung, pigeon breeders and pigeon breeders' disease)³⁷. Continued antigen exposure may lead to end-stage pulmonary fibrosis. Hypersensitivity pneumonitis is frequently misdiagnosed as a pneumonia of infectious etiology. The prevalence of hypersensitivity pneumonitis in the general population is unknown.

Outbreaks of hypersensitivity pneumonitis in office buildings have been traced to air conditioning and humidification systems contaminated with bacteria and molds³⁸. In the home, hypersensitivity pneumonitis is often caused by contaminated humidifiers or by pigeon or pet bird antigens. The period of sensitization before a reaction occurs may be as long as months or even years. Acute symptoms, which occur four to six hours postexposure and recur on challenge with the offending agent, include cough, dyspnea, chills, myalgia, fatigue, and high fever. Nodules and nonspecific infiltrates may be noted on chest films. The white blood cell count is elevated, as is specific IgG to the offending antigen. Hypersensitivity pneumonitis generally responds to corticosteroids or cessation of exposure (either keeping symptomatic people out of contaminated environments or removing the offering agents).

·         Humidifier Fever

Humidifier fever is a disease of uncertain etiology³⁹. It shares symptoms with hypersensitivity pneumonitis, but the high attack rate and short-term effects may indicate that toxins (e.g., bacterial endotoxins) are involved. Onset occurs a few hours after exposure. It is a flu-like illness marked by fever, headache, chills, myalgia, and malaise but without prominent pulmonary symptoms. It normally subsides within 24 hours without residual effects, and a physician is rarely consulted. Humidifier fever has been related to exposure to amoebae, bacteria, and fungi found in humidifier reservoirs, air conditioners, and aquaria. The attack rate within a workplace may be quite high, sometimes exceeding 25 percent.

Bacterial and fungal organisms can be emitted from impeller (cool mist) and ultrasonic humidifiers. Mesophilic fungi, thermophilic bacteria, and thermophilic actinomycetes -- all of which are associated with development of allergic responses -- have been isolated from humidifiers built into the forced-air heating system as well as separate console units. Airborne concentrations of microorganisms are noted during operation and might be quite high for individuals using ultrasonic or cool mist units. Drying and chemical disinfection with bleach or 3% hydrogen peroxide solution are effective remedial measures over a short period, but cannot be considered as reliable maintenance. Only rigorous, daily, and end-of-season cleaning regimens, coupled with disinfection, have been shown to be effective. Manual cleaning of contaminated reservoirs can cause exposure to allergens and pathogens.

·         Mycotoxins

Another class of agents that may cause disease related to indoor airborne exposure is the mycotoxins. These agents are fungal metabolites that have toxic effects ranging from short-term irritation to immunosuppression and cancer. Virtually all the information related to diseases caused by mycotoxins concerns ingestion of contaminated food⁴⁰. However, mycotoxins are contained in some kinds of fungus spores, and these can enter the body through the respiratory tract. At least one case of neurotoxic symptoms possibly related to airborne mycotoxin exposure in a heavily contaminated environment has been reported⁴¹. Skin is another potential route of exposure to mycotoxins. Toxins of several fungi have caused cases of severe dermatosis. In view of the serious nature of the toxic effects reported for mycotoxins, exposure to mycotoxin-producing agents should be minimized.

• Chlorinated Chemicals – domestic water and dry cleaning
  Several chlorinated chemicals can cause cancer and other serious health problems.

These chemicals can come from consumer products you buy in the store, dry-cleaned

clothes, and treated municipal water. Air levels of these chemicals, therefore, are

generally higher in your home than outdoors. Cancer is the primary health risk for people who are exposed to certain chlorinated chemicals for long periods of time. Figure 1 shows the relative cancer risk from equal exposures to five chlorinated chemicals associated with cancer. Liver cancer is the most common type of cancer associated with exposure to chlorinated chemicals. However, the lungs and kidneys may also be affected.

Cancer is not the only health problem that can be caused by chlorinated chemicals.

If there are high levels of these chemicals in your home or where you work, you may

feel tired, dizzy, or nauseous, or have a headache. Your eyes, nose, and throat may

burn or feel sore and scratchy. These are warning signs and should be heeded. High

levels of these chemicals can prevent your central nervous system from functioning

properly. They can also cause diseases of the liver, kidneys, and lungs. In addition,

exposure to methylene chloride can cause an increase in the amount of

carboxyhemoglobin in the blood. When this happens, your blood cannot absorb the

oxygen you need. This results in a medical condition similar to carbon monoxide

poisoning.

The level of danger and the seriousness of the illnesses that may occur are determined

by the amount of the chemical in the air you breathe and the length of time you breathe

it. Small children can be more at risk since they are often more active and breathe

more rapidly than adults; therefore, their exposure is generally greater. In some

situations, people also can be exposed orally or through the skin. Exposure to very

high levels of these chemicals can result in the failure of one or more major organs,

such as the liver, kidneys, or lungs, and can lead to death.