• Irritant or allergic conjunctivitis (burning, sensation of dryness, redness) 

 
• Rhinorrhea, nasal obstruction
• Irritant rhinitis
• Allergic rhinitis, chronic sinusitis 

 
• Chest tightness, cough +/- fever, shortness of breath with exertion
• Nonspecific abnormalities (no chest X-ray or lung function abnormalities can be documented)
• Asthma
• Hypersensitivity pneumonitis
• Infectious pneumonia

-  Legionella pneumonia
-  Aspergillus pneumonia (in
    immunosuppressed persons)
-  Tuberculosis
-  Others (most common in
    immunosuppressed persons) 

 
• Dryness, irritation of the throat 

General Symptoms

 
• Headaches, lethargy, fatigue, poor concentration
• Nonspecific complaints
• Systemic effects of hypersensitivity pneumonitis
• Variant of organic dust toxic syndrome (humidifier fever)
• Carbon monoxide poisoning 

 
• Dryness, irritation, rash 

Relative Humidity
Should remain between 35 and 55%. Lower humidity leads to skin drying, irritation. High humidity leads to growth of molds (Aspergillus, Stachybotrys, etc.) and bacteria which cause other illness. 

Ventilation
Poor ventilation allows carbon dioxide to accumulate as well as other gases. This can be a problem in modern, airtight buildings. 

Lighting
UV rays from fluorescent lighting cause photochemical reactions which lead to formation of "smog" that can irritate eyes. 

Odors
Odors, such as those of swine confinement buildings, may seep into the home from the outside. Approximately 30% of persons may respond with headache, malaise, etc. The mechanism by which this occurs is a point of much debate. 

**Secondhand Smoke
Short-term effects include mucous membrane irritation. Long-term effects include lung cancer from inhalation of carcinogens within the smoke. There is also good evidence that passive cigarette smoke in the home contributes to the development of asthma in children and causes increased risk for respiratory infections. 

Asbestos
Inhalation of fibers causes inflammation and tumors. This is manifested as pleural plaques (benign scar-like changes seen on chest X-ray or during surgery or autopsy), fibrosis (asbestosis), and cancers in the lung. Can also cause cancer of the lining of the lung (pleura) and in the abdominal and abdominal cavity (mesothelioma). 

Asbestos fibers are ubiquitous in the environment (from insulation, brake linings, etc.), but more common in urban areas and are often found in low numbers in lungs of healthy persons. There is NOT any strong evidence that asbestos insulation causes risk to those who live in buildings that have asbestos insulation. The OSHA TLV is now 0.2 fibers/c³, while most buildings have 0.00003 to 0.00024 fibers/cm³. Low exposures from living and working in buildings is estimated at 1 million times less than exposures around the time of WWII, which caused recognition of asbestos-related cancers. 

**Carbon Monoxide
Carbon monoxide exposure occurs through inhalation. This substance binds to the hemoglobin molecule with a much greater affinity (200 times) than oxygen. Thus, oxygen is displaced (the amount dissolved in the blood is not enough to sustain life) and leads to tissue hypoxia. Tissues most dependant on large amounts of oxygen suffer most (brain, heart). 

Severe exposures can cause brain damage, evident after recovery from the acute effects. It can also cause heart attacks. The most common source of carbon monoxide poisoning in the home is from incorrectly vented furnaces and heaters. However, one must remember that carbon monoxide poisoning can also occur after use of methylene chloride containing varnish removers in a poorly ventilated setting. 

Volatile Organic Compounds (VOCs)
This group consists of the large group of volatile organic compounds with melting points below room temperature and boiling points ranging from 50-100 to 240-260 degrees C. The most important source of these VOCs is gasoline burned in motor vehicles. VOCs may also be emitted by home furnishings as well as consumer products used for cleaning. 

Formaldehyde is a good example of a VOC. It is emitted from a long list of materials that are part of the structure of houses and which are used within the home. Ten to twenty percent of the population reacts to this gas by developing eye irritation, neuropsychologic effects, lower respiratory effects, etc. Levels in residences have been reported as high as 0.13 ppm. 

Nitrogen Dioxide (NO₂)
Concentrations are high at times in homes that use gas stoves and kerosine heaters. There is some evidence that high N0₂ levels are linked to a greater prevalence of respiratory symptoms in school children. Persons with underlying lung disease may also be sensitive to N0₂. 

Wood Smoke
This can cause exacerbation of asthma because it acts as an irritant. It may be a cause of chronic bronchitis. Respiratory symptoms may be more common in homes where there is a woodburning stove. Modern airtight stoves with a well-functioning chimney or flue reduce carbon monoxide and particle levels in the home.

Radon
Radon forms in the soil from radium and uranium. Breakdown products of radon (radon daughters) in the lung after radon inhalation may cause lung cancer in some persons. This effect is best understood in miners exposed to radon gas underground. This can occur in non-smokers, but is more likely if the person does smoke. 

At this time, it does not appear that the risk from radon exposure in the home is a large one. Some authors argue that radon exposure in the home is too low to cause lung cancer. 

**Animal Dander
Dander from cats and dogs that live indoors as family pets is a very important cause of allergic symptoms in sensitized people. These people can suffer from asthma, allergic rhinitis, and allergic conjunctivitis. Dander can persist in the environment long after the pet no longer lives in the home. 

**Mites (Dermatophagoides pteronyssinus and D. farinae)
Mites live in carpet, bedding, etc., and consume skin particles from humans. They are a common source of allergy (asthma and allergic rhinitis) and are the offending substance in "house dust." 

Management of this problem includes keeping humidity low, good ventilation, frequent vacuuming, removing carpets, and covering pillows and mattresses. 

**Cockroaches
Cockroach antigen is associated with allergic asthma. This may be one cause of the increased prevalence of asthma in inner city populations. 

**Mold Spores
These can cause an allergic reaction (rhinitis and/or asthma). Hypersensitivity pneumonitis is another type of allergic reaction which consists of fever, chills, dry cough, and a flu-like feeling, all or some of which happen 4-6 hours after repeated mold spore inhalation (like from a humidifier) in susceptible persons. It consists of an inflammatory reaction in the lung which causes release of mediators of inflammation from the lung. These circulate and cause fever and other systemic effects. If persons are immunocompromised (for example, from cancer), fungi can cause infection in the lung. 

Endotoxin
This is a substance that is part of the cell wall of gram-negative bacteria, such as Pseudomonas. When inhaled, it can cause fever, chills, malaise, and headaches. This occurs through activation of macrophages in the lung, as well as other cells there, releasing mediators of inflammation (much like hypersensitivity pneumonitis). 

It is probably another cause of "humidifier fever." Effects of chronic, moderate level exposure reported from work places include bronchitis and an asthma-like syndrome. 

Glucans
These are substances which are part of the cell wall of molds. They activate the immune system. Some believe they are the cause of nonspecific complaints in persons negatively affected by time spent in certain buildings. 

**Factors Dr. Von Essen considers to be most important in terms of the impact on human health.