**4. Health effects induced by indoor exposure to biological contaminants**

Indoor air contamination can generate a multitude of effects on human health. The effects are especially on the respiratory system. Allergic reactions can be induced by the exposure to different biological agents that are identified in indoor air. Also, there is evidence to suggest that exposure to biological pollutants in indoor air can be associated with symptoms with neurological basis like headaches, fatigue, and forgetfulness.

Some of the effects on the respiratory system related to the biological contamination of indoor air are due to the inflammation of the airways. This can appear in both allergic (with the implication of IgE and IgG antibodies) and nonallergic respiratory diseases. The separation between those two entities is important in the case of asthma and rhinitis.

### **4.1. Rhinitis**

**2.6. Mycotoxins**

492 Current Air Quality Issues

**2.8. Viruses**

These are toxins (secondary metabolites) produced by fungi that interfere with RNA synthesis and can cause DNA damage. Some mycotoxins like aflatoxins produced by *Aspergillus flavus* and *Aspergillus parasiticus* induce carcinogenic effects [2, 11]. Indoor exposure to mycotoxins produced by *Stachybotrys chartarum* can be associated with acute pulmonary hemorrhage.

Fungi can produce around 200 volatile organic compounds. The identification of the VOCs in indoor air shows that there is a fungal growth present, even if the quantitative measurements are negative [11]. One of the most important substances that can be identified in indoor air is

Indoor air humidity can induce a longer survival time of respiratory viruses and increased risk

Indoor air levels of bacterial concentrations of <1, 000 CFU/m3 can be regarded as "low, " and

the crowdedness of the room and the efficiency of the ventilation and thus are a measure of

Characterizing the bacterial flora in the sample may give additional information about the sources of the bacteria present. If Gram-positive cocci and corynebacteria, the common bacteria

The presence of Gram-negative bacteria shows an active bacterial growth due to the presence

Gram-positive bacteria with exo- and endospores like *Streptomyces* and *Bacillus* can grow on moist building materials. Their spores are very resistant and can survive even if the air

The presence of fecal bacteria like the group of *Enterobacteriaceae* is considered heavy contam‐ ination of indoor air, coming probably from a sewage leakage. The presence of actinomycetes

The presence of two groups of bacteria, that is, *Legionella* and actinomycetes, has a special

*Legionella* spp. are Gram-negative environmental bacteria that have found a remarkable ecological niche in man-made water systems, especially in those serving air conditioning

can be regarded as "high" [1]. These numbers reflect mainly

**3. Exposure evaluation of biological contamination of indoor air**

of the human skin, are the dominating groups, this indicates human sources [1].

**2.7. Fungi and Volatile Organic Compounds (VOC) in indoor air**

formaldehyde that can induce cancer.

concentrations of >5, 000 CFU/m3

of water indoors.

humidity is low.

importance in indoor air.

systems for heat transfer [1].

the hygienic quality of the indoor air.

shows the growth of microbes in the building material.

of respiratory infection and allergic diseases.

Rhinitis is induced by the inflammation of the mucosa of the upper respiratory tract. Symptoms of rhinitis are nasal congestion, rhinorrhea, sneezing, and conjunctivitis. Rhinitis can be of allergic or nonallergic cause [1, 11].

#### **4.2. Asthma**

Allergic asthma involves IgE-mediated sensitivity and eosinophils in presence of an atopic underlying reaction of the respiratory airways [1, 12-18]. Among adults, there is also an increasing prevalence of asthma. People with moderate to severe asthma will react adversely toward biological and other contaminants in the indoor environment due to a nonspecific bronchial hyperresponsiveness. That is an exaggerated bronhoconstrictor response to numer‐ ous numbers of stimuli. The severity of asthma and the need of medication in house dust mite allergic patients is closely related to the amount of endotoxin in house dust in a dose-dependent manner [1].

Pollen allergens interact with other sources of fine particles in polluted air, which concentrate the allergens and trigger asthma attacks. As for the interaction between biological and nonbiological agents, airborne particles such as diesel exhaust particles have an adjuvant activity for IgE antibody and cytokine production [1]. The intranasal instillation of ragweed allergens with diesel exhaust particles in allergic patients significantly increased allergenspecific IgE production and enhanced Th2-type cytokine mRNA expression compared to allergic patients instilled with ragweed alone [1].

Both allergens and viruses have been known to worsen asthma symptoms. A study in the UK demonstrated that allergen exposure and viral infections act synergistically to trigger exacer‐ bations in adults [1].

#### **4.3. Chronic bronchitis**

Chronic bronchitis is defined as cough with phlegm (productive cough) for at least 3 months per year for 2 years or more [1, 17-19]. Chronic bronchitis may be present with or without airways obstruction. The underlying mechanism is an increase in mucus secreting glands and alterations in the characteristics of the mucus itself [1]. Airway inflammation is present, and an increased number of neutrophils can be observed [1].

Subjects with chronic bronchitis may also have symptoms such as dyspnea, chest tightness, and wheezing, and there is thus a considerable overlap in symptoms between allergic asthma, nonallergic asthma, and bronchitis [1]. Biological contamination through the presence of endotoxin and β-glucan can be incriminated in the pathogenesis of bronchitis [1].

### **4.4. Chronic airflow obstruction**

Several studies have shown associations between chronic airflow obstructions as measured by spirometry (particularly FEV1) and organic dust exposures in industrial and agricultural occupational populations [1, 19]. Endotoxin exposure may play an important role.

#### **4.5. Hypersensitivity Pneumonitis (HP) or Extrinsic Allergic Alveolitis (EAA) [1, 2, 20]**

The disease, also known as "farmers lung" or "pigeon breeder's lung, " is one of the most severe diseases induced by fungi and thermophilic actinomycetes (spore-forming bacteria) exposure. The clinical aspect of HP is represented by severe pulmonary disease with pneu‐ monia-like fever, cough, tightness of chest, shortness of breath, inflammation of pulmonary parenchyma, and development of pulmonary granulomas. HP is very similar to organic dust toxic syndrome (ODTS).

#### **4.6. Organic Dust Toxic Syndrome (ODTS)**

The disease is similar to influenza and is characterized by symptoms like acute fever, dry cough, dyspnea, chest tightness, headache, shivering, malaise, fatigue, and muscle and joint pains. ODTS is a nonallergic neutrophil-mediated airway inflammation [1].

#### **4.7. Atopic allergic dermatitis**

This disease can be induced by exposure to the biological indoor air pollutants.

#### **4.8. Sick building syndrome**

In the 1988s, the concept of "sick building syndrome" (SBS) was established by the WHO [1, 3, 21, 22]. The label sick building syndrome (SBS) can be applied when the inhabitants or occupants of different indoor spaces develop acute health problems or discomfort inside the rooms. The exposed people have the following symptoms: eye, nose, and throat irritation and dryness; itching and dryness of skin and eyes; dry cough; nausea; vomiting; headache; difficulty in concentration; fatigue; etc. The symptoms disappear after cessation of the exposure.
