Biological contaminants include bacteria, viruses, animal dander and cat saliva, house dust, mites, cockroaches, and pollen. There are many sources of these pollutants. By controlling the relative humidity level in a home, the growth of some sources of biological contaminates can be minimized. A relative humidity of 30-40 percent is generally recommended for homes. Standing water, water-damaged materials or wet surfaces also serve as a breeding ground for molds, mildews, bacteria and insects. House dust mites, the source of one of the most powerful biological allergens, grow in damp, warm environments.

Sources

• pollen, which originate from plants

• viruses, which are transmitted by people and animals

• mold

• bacteria, which are carried by people, animals, and soil and plant debris

• household pets, which are sources of saliva and animal dander (skin flakes)

• droppings and body parts from cockroaches, rodents and other pests or insects

• viruses and bacteria

• 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 mold, mildew and other sources of biological contaminants and can then distribute these contaminants through the home

• Back up or sewer and drains often results is heavy bacterial contamination

Many of these biological contaminants are small enough to be inhaled.

Biological contaminants are, or are produced by, living things. Biological contaminants are often found in areas that provide food and moisture or water. For example:

• damp or wet areas such as cooling coils, humidifiers, condensate pans or poorly vented bathrooms can be moldy

• draperies, bedding, carpet and other areas where dust collects may accumulate biological contaminants

Health Effects from Biological Contaminants

Some biological contaminants trigger allergic reactions, including:

• hypersensitivity pneumonitis

• allergic rhinitis

• some types of asthma

Infectious illnesses, such as influenza, measles and chicken pox are transmitted through the air. Certain molds produce and 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.

Mold, dust mites, pet dander and pest droppings or body parts can trigger asthma. Biological contaminants, including molds and pollen can cause allergic reactions for a significant portion of the population. Tuberculosis, measles, staphylococcus infections, Legionella and influenza are known to be transmitted by air.