Indoor Air Pollutants

1.   What are indoor air pollutants?
2.   How can I or my child be exposed?
3.   How can indoor air pollutants affect my family's health?
4.   Is there a medical test to tell whether my child or I have been exposed to
      high levels of indoor air pollutants?
5.   What can I do to limit exposure to indoor air pollutants to myself and my
6.   References

What are indoor air pollutants?

Indoor air may contain a complex mixture of potential pollutants. The most important of these pollutants include: environmental tobacco smoke, combustion products, volatile organic compounds, and bioallergens. In our discussion below, we will answer each question with regard to these four potential pollutants.
How can I or my child be exposed?

Your child can be exposed to different environmental pollutants in different ways. Each of the four most important potential pollutants (environmental tobacco smoke, combustion products, volatile organic compounds, and bioallergens) is discussed separately below.

Environmental Tobacco Smoke (ETS)

– ETS is also known as second-hand smoke. Any time someone smokes indoors, ETS is produced.

– ETS is considered a leading component of indoor air pollution considering the number of children exposed and potential negative health effects.

– According to an EPA report, 19% of children under 7 years of age in the U.S. were exposed to ETS from someone in their household in 1999. This has decreased from 29% of households in 1994. [3]

– Since children may spend much of their time indoors, they may receive a relatively high degree of exposure to ETS.

Possible sources of exposure to ETS include:
  • The home
  • The homes of relatives and friends
  • Child care settings
  • Public facilities such as restaurants, stores, etc.
  • Automobiles
Jump to Effects of ETS

Combustion Products

Combustion, or burning, is a process that occurs when a fuel source (wood, gas, coal) is burned. This process uses oxygen and creates various combustion products. The most important of these are carbon monoxide (CO), nitrogen dioxide (NO2), and particulate matter. Common sources of higher levels of these combustion products in the home include:
  • improperly maintained gas stoves
  • improperly ventilated wood stoves
  • fireplaces
  • kerosene heaters
Jump to Effects of Combustion Products

Volatile Organic Compounds (VOCs)

VOCs are chemicals likely to vaporize into the air at room temperature. Examples include formaldehyde, certain hydrocarbons (compounds made of hydrogen and carbon) and others. The vast majority of exposure to VOCs occurs through breathing.

Exposure to VOCs may be increased if ventilation is poor.

Possible sources of exposure to VOCs in the home include:
  • Fumes from paints, paint removers, lacquers, or other coatings
  • Fumes from home building materials such as pressed wood. Exposure from this source is more likely to be increased during new home construction or renovation.
  • Fumes from furnishings such as carpets and some furniture.
  • Newly constructed mobile homes that contain pressed-wood products are an important source of high formaldehyde levels. [34] This may be due in part to the low ventilation in mobile homes.
  • Jump to Effects of VOCs


    Bioallergens are small proteins from a variety of sources that can trigger an immune response in at-risk individuals. The most important bioallergens include: cockroach antigen, dust mite antigen, molds, and cat antigen.

    Cockroach antigen

    Cockroach antigen is a protein found in the outer shell of the cockroach.When cock- roaches shed parts of their shell, these antigens can be released into the air and subsequently inhaled. Exposure to higher levels of cockroach antigens occur in places cockroaches regularly inhabit, including:
    • The kitchen
    • The bathroom
    • Family eating areas
    Exposure to cockroach antigen is an especially important health problem in inner city areas. Several studies have shown that people dwelling in the inner city tend to be more sensitized to cockroach antigens than people living in other areas.[40][41] This has important implications regarding the develop- ment of asthma and is discussed later in the health effects section.

    Dust-mite antigen

    Dust-mite antigen is an enzyme passed in the feces of dust-mites.Dust-mites are microscopic insects that inhabit house dust. They tend to be found in highest concentrations in places where people sleep.

    Dust mites also tend to survive well in humid conditions and may be more abundant in humid climates. Some of the dust-mite feces are found indoor air and can be breathed in to the lungs where they can exert health effects.

    Common sources of exposure to dust-mite antigens include:
    • bedding materials
    • couches
    • pillows
    • carpets
    • stuffed animals
    • old books

    Since molds are nearly everywhere in our environment, we are all probably exposed to some degree. The main route of exposure is through breathing. However, certain molds can also be absorbed across skin.

    Exposure to higher levels of molds tends to occur in areas with high moisture and low ventilation. Possible sources of exposure in the home include:
    • Water-damaged roofs and walls
    • Accumulated water in plant pots
    • Molds growing in pet urine
    • Damp basements
    Cat antigen

    Cat antigen is a small protein found in the saliva and dander of house cats.Unlike many other antigens, the cat antigen tends to persist for long periods in indoor and outdoor environments. Exposure to cat antigen can occur near any surface that the house cat has spent time, including:
    • Carpets
    • Couches
    • Beds
    Jump to Effects of Bioallergins
    How can indoor air pollutants affect my family's health?

    The health effects of indoor air pollutants will depend on several factors:
    • particular pollutant involved
    • level and time course of exposure
    • health status of the exposed individual, etc.
    We will discuss the health effects of each of the main indoor air pollutants (environmental tobacco smoke (ETS), bioallergens, combustion products, and volatile organic compounds) with regards to acute and chronic exposure.

    Environmental Tobacco Smoke (ETS)

    Children have an increased sensitivity to ETS compared with adults due to their relatively higher respiratory rates and differences in metabolism. [46]

    Acute effects:
    • ETS may cause immediate coughing, irritation of eyes, nasal passages, and throat.
    • ETS has been associated with increased risk of sudden infant death syndrome (SIDS) [13][14]
    Chronic effects:
    • Developmental-

      Mothers who smoke during pregnancy tend to have children with lower birth weights compared with unexposed children. [43][44][68]

      Children exposed only to ETS may also have relatively decreased birth weights and be small for their gestational age [43][44][45][68]
    • Neurobehavioral-

      Several human studies have strongly suggested that mothers who actively smoke during pregnancy are more likely to have children with decreased IQ, decreased language skills, and increased behavioral problems. [7][42][55][56]

      Infants exposed to ETS in the womb and after birth are also more likely to have problems with language, decreased IQ, and increased behavioral problems. [7][54][57][58]
    • Pulmonary-

      Several human studies have also suggested infants exposed to ETS are more likely to be hospitalized for pneumonia. [9][10]

      Some human studies suggest that children exposed to ETS perform more poorly on lung function testing later in life. [36][52]

      Several human studies suggest that chronic ETS exposure worsens asthma symptoms in children with pre-existing asthma. [36][53]

      There is limited human evidence that ETS causes lung cancer. Some human studies have suggested that ETS may increase risk of lung cancer later in life. However, other human studies argues against this association. [15][50][69][70]
    • Reproductive-

      One human study suggests that exposure to ETS may increase risk of pain during menstrual periods for women of reproductive age. [16]

    The bioallergens exert their health effects by triggering the immune system. Most of the health effects from the bioallergens involve the respiratory system since the immune response occurs within the lungs.However, the health effects that may occur depend on the specific type of immune reaction that takes place and the susceptibility of the individual.

    Bioallergens can exert their effects through a process known as allergic sensitization.After an individual is exposed to threshold amounts of the allergen over a sufficient period time, the person’s immune system may react to very small amounts of the antigen or nonspecific stimuli (cold weather, exercise, air pollutants, etc.).In the lung tissue, if this exposure continues over time, this may cause asthma.The health effect of these bioallergens will be discussed in terms of acute and chronic exposure.
    • Cockroach antigen:

      — Acute exposure: The acute effects of cockroach antigen include worsening of asthma symptoms, coughing, sneezing, itching, irritation of the eyes, etc.

      — Chronic exposure: Chronic exposure to this antigen likely increases rates of allergic sensitization. This in turn may worsen existing allergic rhinitis (common "allergy") or asthma [37][39]
    • Dust-mite antigen:

      — Acute exposure: In sensitized individuals, dust-mite antigen may cause sneezing, itching, irritation of the eyes, coughing and wheezing.

      — Chronic exposure: Several human studies strongly suggest that chronic exposure to dust-mites can cause a person to become sensitized to the anti- gen. This may then worsen existing allergic rhinitis (common "allergy") or asthma. [37][39]
    • Molds:

      The health effects of molds have been studied in both occupational and general environmental settings such as home or school.

      — Acute exposure: Exposure to molds may cause irritation of the eyes, nose, throat, sneezing, or coughing. In some susceptible individuals, exposure to molds has been associated with life- threatening worsening of asthma. [60][61]

      Exposure to very toxic strains of molds in susceptible children has been associated with pulmonary hemorrhage (bleeding within the lungs) and pulmonary hemosiderosis (build-up of toxic iron-containing proteins in the lungs). [25][26] One of the toxic molds that might be associated with these problems is called Stachybotros.

      — Chronic exposure: Chronic mold exposure can produce health ef- fects. Some human studies suggest that chronic mold exposure may aggravate asthma symptoms and increase rates of immunological sensitization. [27][71]

      Several human studies also suggest that such exposure alters the levels of white blood cells in the immune system. However, the significance of this finding is not clear. [35][36]
    • Cat antigen:
      • Acute exposure:

        Exposure may trigger an asthma attack in a susceptible individual.
      • Chronic exposure:

        There is limited human evidence that exposure to cats may increase rates of sensitization to cat antigen in susceptible individuals. [72] However, not all studies support this relationship. [78]
    Combustion products
    • Carbon Monoxide (CO):

      — Hemoglobin (Hb) is a substance in red blood cells responsible for transporting oxygen to all tissues of the body. CO combines with Hb and makes it unable to carry oxygen.This produces the following health effects, depending on the time course and level of exposure:
      • Acute, high level exposure:

        Exposure to high levels may cause death. Other possible health effects include severe confusion, shortness of breath, or loss of conscious- ness. Moderate exposures may produce fatigue, headache, or confusion.

        Exposure to high levels of CO is more likely in the home if improperly maintained or ventilated gas/wood stoves, fireplaces, or kerosene heaters are present.
      • Chronic effects of acute, high-level exposure:

        Acute exposure to high levels of CO may produce various chronic neurological problems long after the exposure is gone. [22][23]

        Chronic, low-level exposure: There is limited human evidence that chronic, low-level CO exposure may cause health effects. [76]
      • Nitrous Dioxide (NO2):

        Acute, high-level exposure: Exposure to NO2 may cause irritation of the upper respiratory system as well as cough.

        Chronic, low-level exposure: There is little human evidence available concerning the adverse health effects of this type of exposure. One study has suggested that this type of exposure to NO2 may increase bronchitis, wheezing, and asthma among school age girls. [29] How- ever, other human studies have argued against this association. [19][33]
      • Particulate Matter:

        Acute, high-level exposure: Exposure to indoor particulate matter may cause irritation of the upper respiratory system, cough, and wheezing. [74]

        Chronic, low-level exposure: There is little human evidence demonstrating health effects from this type of exposure. [73][75]
    Volatile Organic Compounds (VOCs)
    • Acute, high-level exposure:

      Such exposure to VOCs may cause irritation of the skin, nose, eyes, throat as well as headache, nausea, and vomiting.
    • Chronic, low-level exposure:

      There is limited human evidence suggesting negative health effects from this type of exposure.[63][64]

      Several human studies have suggested that exposure to VOCs may exacerbate asthma symptoms in susceptible individuals. [62][67]

      Several occupational studies have suggested that formaldehyde exposure may increase the risk of cancer in the nose and throat. However, the evidence is conflicting and not all studies support this relationship. [79-81].

    Is there a medical test to tell whether my child or I have been exposed to high levels of indoor air pollutants?

    For some of the pollutants, there are medical tests available while for others there is no test. Each pollutant will be discussed separately (carbon monoxide (CO), nitrous and sulfur dioxides (NO2, SO2), volatile organic compounds, and bioallergens):
    • CO:

      There is a test available to detect exposure to CO.The test measures the amount of a substance called carboxyhemoglobin in the blood and must be performed within a few days of exposure.

      If you suspect your child may be poisoned with CO, remove the child from the likely source of exposure and call 911. If emergency help is not available, remove the child from the likely source of exposure and immediately take the child to the nearest emergency room. Make sure the child gets plenty of fresh air.
    • NO2, SO2:

      There are no medical tests available to detect the levels of these chemicals in the body.
    • VOCs:

      There is a medical test available that can detect the levels of some VOC’s in the body.

      These tests are useful mainly in research settings, not for clinical practice.
    • Bioallergens:

      Skin testing can be used to estimate the degree of immune sensitization to some bioallergens. It is widely available in clinical practice. [38][59]

      There are medical tests that can detect whether antibodies to various bioallergens are present. An antibody is a protein made by the immune system in response to an antigen. However, these tests cannot tell precisely when the exposure took place or estimate the amount of exposure.

      Another important medical test is the bronchial challenge test. Sensitized individuals with respiratory symptoms are exposed to small amounts of one or more known bioallergens. The subsequent airway response can then be measured to assess the person’s degree of sensitization. This test is available in certain medical centers.

    What can I do to limit exposure to indoor air pollutants to myself and my child?

    Ways to limit exposure are discussed according to the four most common indoor air pollutants: environmental tobacco smoke, bioallergens, combustion products, and volatile organic compounds. Additional general comments are at the end of the section.
    • Environmental Tobacco Smoke (ETS): [1]

      Don't smoke. This is probably the single most important thing you can to do improve the quality of indoor air. If you are pregnant, it is especially important not to smoke.

      If you are unable to quit, only smoke while outside. Do not allow any other household members or guests to smoke inside the house. If you are a mother breastfeeding your child, do not smoke at least an hour prior to breast- feeding. Chemicals from the smoke can enter your milk and reach your child.

      Do not smoke while you and your child are in the car or any other enclosed space.
    • Bioallergens:
      • Dust mites:

        If you suspect that a family member is sensitive to dust mite antigen, wash bedding every 2 weeks in hot water (>120° F) to kill dust mites living in these items. Also, encase pillows and mattresses in plastic coverings and remove any stuffed animals and old books from the bedroom.

        Consider using a water-seal vacuum cleaner instead of a regular vacuum cleaner to decrease dust-mite antigen in carpets.

        If you suspect that a family member is sensitized to dust mite antigen, remove possible sources of dust mites in the home, including carpets and drapes.Consider tile and blinds instead.
      • Molds: [1]

        If your house has sustained water damage from a flood or a leak, remove all water damaged items within 24 hours.

        If molds have already started to grow on carpets, walls or other objects, first wash the moldy surface with soap and water. Next, wash the surface with a solution of 1 part bleach to 4 parts water. Be sure to wear rubber gloves while doing this. If you are sensitive to molds, ask someone who is not sensitive to molds to do the cleaning.
      • Cockroach antigen:

        The key to reducing cockroach antigen is to

        One way to so this is to meticulously clean all food debris in the kitchen, tabletop, and floors. This will reduce the food supply available to the cockroaches. Also, encourage all members of the household to eat only in the dining room or kitchen.

        Use caulk to seal all crevices of the pipes under the kitchen sink and bathroom. This will help reduce cockroach entry into the home.

        To control existing cockroaches, use sticky traps and boric acid first. If these do not work, consider professional extermination services.
      • Cat antigen:

        If you or your child are sensitive to cat antigen, consider giving the cat away. This will eliminate the source of exposure. If you are unwilling to do this, scrub your cat with soap and water at least once a week. This may reduce, but not eliminate, the amount of cat antigen present in the home.
    • Combustion products:

      If you have a gas stove, wood stove, or fireplace, have it checked by a professional at least once a year. [1]

      If you have a fireplace, gas stove, wood stove, or kerosene heater, make sure the room is well ventilated. Also, the fireplace should be regularly cleaned and the soot should be less than 1 inch thick. [1]

      Only burn old, dry wood in the fireplace. Burning of wet or green wood results in increased release of particles into the air.

      Never use a stove as a space heater.

      Never burn charcoal indoors. [1]

      Don’t run cars or lawnmowers in a closed garage. [37]

      Install an approved CO detector in bedrooms. [37]
    • VOCs: [1]

      Do not store unused paints and building supplies inside the home. If you have these products, dispose of them properly in authorized collection points such as your local municipal waste dump.

      If you suspect that some of your furnishings are giving off VOCs, make sure the room is well ventilated. Try to eliminate the source of exposure.

      If it is not possible to eliminate the source of exposure, seal the polluting surface with polyurethane or some other non-toxic sealant.
    • General:

      The EPA has not yet taken a stand on the use of air cleaners. However, it is probably more important to reduce the possible sources of exposure to indoor air pollutants than to use an air filter. If you do choose to use an air-filter, use a single HEPA-grade filter in your child’s bedroom.

      Do not use an air-filter that generates ozone. Exposure to ozone may cause breathing difficulties or other negative health effects.


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