Biological Contaminants



The following information is from the EPA's website.

See also our Shop/Indoor Climate pages for laboratory analysis of pollutants in your home or office.

Biological contaminants include bacteria, moulds, mildew, viruses, animal dander and cat saliva, house dust, mites, cockroaches, and pollen.

There are many sources of these pollutants. Pollens originate from plants; viruses are transmitted by people and animals; bacteria are carried by people, animals, and soil and plant debris; and household pets are sources of saliva and animal dander. The protein in urine from rats and mice is a potent allergen. When it dries, it can become airborne. Contaminated central air handling systems can become breeding grounds for mould, mildew, and other sources of biological contaminants and can then distribute these contaminants through the home.

By controlling the relative humidity level in a home, the growth of some sources of biologicals can be minimized. A relative humidity of 30-50 percent is generally recommended for homes. Standing water, water-damaged materials, or wet surfaces also serve as a breeding ground for moulds, mildews, bacteria, and insects. House dust mites, the source of one of the most powerful biological allergens, grow in damp, warm environments.

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. Moulds 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 micro-organisms that can grow in large building ventilation systems. However, these diseases can also be traced to micro-organisms 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.

Reducing Exposure to Biological Contaminants

    * Install and use exhaust fans that are vented to the outdoors in kitchens and bathrooms and vent clothes dryers outdoors.
      These actions can eliminate much of the moisture that builds up from everyday activities. There are exhaust fans on the market that produce little noise, an important consideration for some people. Another benefit to using kitchen and bathroom exhaust fans is that they can reduce levels of organic pollutants that vaporize from hot water used in showers and dishwashers.
    * Ventilate the attic and crawl spaces to prevent moisture build-up. 
      Keeping humidity levels in these areas below 50 percent can prevent water condensation on building materials.
    * If using cool mist or ultrasonic humidifiers, clean appliances according to manufacturer's instructions and refill with fresh water daily. 
      Because these humidifiers can become breeding grounds for biological contaminants, they have the potential for causing diseases such as hypersensitivity pneumonitis and humidifier fever. Evaporation trays in air conditioners, dehumidifiers, and refrigerators should also be cleaned frequently.
    * Thoroughly clean and dry water-damaged carpets and building materials (within 24 hours if possible) or consider removal and replacement.
      Water-damaged carpets and building materials can harbour mould and bacteria. It is very difficult to completely rid such materials of biological contaminants.
    * Keep the house clean. House dust mites, pollens, animal dander, and other allergy-causing agents can be reduced, although not eliminated, through regular cleaning. 
    * Do a Space Clearing (see Services section) to raise the level of energy and clarity in your home.  Creepy crawlies hate nothing more than good, strong energy!
    * People who are allergic to these pollutants should use allergen-proof mattress encasements, wash bedding in hot (130 F) water, and avoid room furnishings that accumulate dust, especially if they cannot be washed in hot water. Allergic individuals should also leave the house while it is being vacuumed because vacuuming can actually increase airborne levels of mite allergens and other biological contaminants. Using central vacuum systems that are vented to the outdoors or vacuums with high efficiency filters may also be of help.
    * Take steps to minimize biological pollutants in basements. 
      Clean and disinfect the basement floor drain regularly. Do not finish a basement below ground level unless all water leaks are patched and outdoor ventilation and adequate heat to prevent condensation are provided. Operate a dehumidifier in the basement if needed to keep relative humidity levels between 30 - 50 percent.

About Cockroaches

Droppings or body parts of cockroaches can be asthma triggers.

Cockroaches are commonly found in crowded cities and the southern United States. Certain proteins, called allergens, are found in cockroach faeces and saliva and can cause allergic reactions or trigger asthma symptoms in some individuals. Cockroach allergens likely play a significant role in asthma in many inner-city areas.

Actions You Can Take

An important key to pest management is to free your home of places for pests to hide and to keep them from food and water. Pesticides are toxic for people as well as pests; try to use pest management methods that present the least risk. Some of these methods are:

    * Do not leave out food or garbage.
    * Store food in airtight containers.
    * Clean all food crumbs or spilled liquids right away.
    * Wash dishes as soon as you are done using them.
    * Keep counters, sinks, tables and floors clean and clear of clutter.
    * Fix plumbing leaks and other moisture problems.
    * Take piles of boxes, newspapers, and other items where cockroaches may hide out of your home.
    * Make sure trash in your home is properly stored in containers with lids that close securely, and remove trash daily.
    * Try using poison baits, boric acid, or traps first before using pesticidal sprays.


Mould and Your Health  

All moulds have the potential to cause health effects. Moulds produce allergens, irritants and in some cases, toxins that may cause reactions in humans. The types and severity of symptoms depend, in part, on the types of mould present, the extent of an individual's exposure, the ages of the individuals and their existing sensitivities or allergies.
Allergy-like symptoms such as eye, nose, throat, headache, fatigue and dizziness can result from exposure to these microbiological contaminants. Chronic exposure can lead to Hypersensitivity pneumonitis, allergic asthma and chronic allergy symptoms. Some species of mould produce toxic substances called Mycotoxins and release them into the environment. Many of these Mycotoxins are neurotoxins or immuno-suppressors. Mycotoxins can cause adverse health effects at very low concentrations. Some of the moulds that are known to produce mycotoxins are commonly found in moisture damaged building materials. Exposure pathways include inhalation, ingestion and skin contact.
Several moulds also release Microbial Volatile Organic Compounds into the air. These volatile carbon/oxygen based gases are emitted as part of the microbial metabolism and produce the odour associated with the presence of mould in the home. MVOCs are known irritants. Exposure to MVOCs from mould has been linked to headaches, nasal irritation, dizziness, fatigue and nausea.
Allergic reactions to mould are common and can be set off by breathing spores or skin contact to mould when the person has an increased level of sensitivity. Reactions my be immediate or delayed and may include fever, sneezing, runny nose and/or burning eyes. It has been reported that repeated or even a single exposure to mould may cause a previously non-sensitive individual to become sensitive. The more prolonged the exposure, the greater the risk of developing sensitivity.
Asthma attacks have been triggered by mould exposure. The irritants produced by moulds may also worsen asthma in non-allergic (non-sensitized) people.
A disease that resembles pneumonia called Hypersensitivity Pneumonitis may develop during either a short, acute exposure or chronic exposure. This is a rare disease and very debilitating.
Persons with compromised immune systems may fall prey to opportunistic infections as a result of their bodies' inability to protect itself against common mould exposure.
Moist indoor environments also lead to rapid and continuous growth of bacteria. Many bacteria are known to cause diseases. Although non-pathogenic bacteria do not cause disease, they can challenge the immune system when inhaled in large doses. Non-Pathogenic bacteria can become opportunistic pathogens (disease-causing) on cancer patients or others with compromised immune systems. Negative gram bacteria produce Endotoxins, which can cause fever, headaches, chills, impaired organ function, shock and respiratory distress.
High humidity, condensation and moisture damaged building materials create an environment which supports the rapid and continuous growth of moulds, mildews and bacteria in the home. The recommended "Comfort Zone" for relative humidity in the home is 40% RH to 60% RH. Deviations from this range can coincide with increased levels of bacteria, viruses, mould and other factors that reduce air quality and lead to respiratory problems, including sinus problems and asthma. Some indoor air quality specialists recommend that relative humidity be maintained at less than 55% to control fungal proliferation.
Excess moisture in the home is also a problem because it leads to decay of building materials; it creates conditions that support wood-destroying insect infestations and supports dust mite activity, which in turn can contribute to allergies and asthma. (Dust mites require humidity of over 60% to thrive. Populations are wiped out when humidity levels are below 50%.)
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