**5. Indoor air environment**

Indoor environments are fundamental environmental factors capable of impacting health [16, 32]. Air quality of indoor environments is one of the main factors affecting the health, wellbeing and productivity of people. The effect on health rises as exposure to and density of air pollution increases [35, 42].

In indoor air environments (non-industrial), the most important source of airborne bacteria is the presence of humans (Kim and Kim, 2007). Major indoor activities such as talking, sneezing, coughing, etc. can concentrate airborne biological particulate matter in the indoor environ‐ ment. House dust, pets and their bedding material, wood materials and furniture stuffing could serve as reservoir from which spores of *Alternaria, Aspergillus, Botrytis, Cladosporium, Penicillium, Scopulariopsis* spp. and yeast cells are occasionally released into the indoor air [17].

## **6. Bioaerosols in the indoor air environment**

Bioaerosols consist of aerosols containing microorganisms (bacteria, fungi, viruses) or organic compounds derived from microorganisms (endotoxins, metabolites, toxins and other micro‐ bial fragments) (Heikkienen*et al.,* 2005). Aerosols of biological origin form a significant portion of the total atmospheric aerosols, sometimes reaching up to 50% of all aerosol particles [37].

Bioaerosols vary in size (20 nm to >100 nm) and composition depending on the source, aerosolisation mechanisms and environmental conditions prevailing at the site [53]. The inhalable fraction (PM2.5) is of primary concern because it is the most susceptible portion of the bioaerosols to reach the deeper parts of the respiratory system (Pope *et al.,* 1995).

(c) (d)

**4. Housing and indoor air quality**

**5. Indoor air environment**

pollution increases [35, 42].

**6. Bioaerosols in the indoor air environment**

etc.).

550 Current Air Quality Issues

Housing is a place people spend most of their time and one of 'the main settings that affect human health' [12]. It is well established that housing is a 'key determinant of health' [62]. Good housing and good health go together [62]. Housing, as a neglected site for public health action, has been identified in a number of recent publications (Breysse *et al.,* 2005). Housing, however, encompasses a large range of factors, including biological (mould, cockroaches, dust mites, etc.), chemical (tobacco smoke, paints, etc.) and structural (moisture, heat ventilation,

A large number of the population in Nigeria resides in houses with poor housing conditions (as shown in Figure 2.). Provision of adequate housing has been a problem in developing countries like Nigeria. Shortage of decent accommodation, particularly in cities, has resulted in individuals occupying bungalows or rooms above specified capacity. More so, in the quest to provide themselves with urgent accommodation, people have resorted to building houses outside required specifications and/or at indecent locations. Because of this problem, there is

Indoor environments are fundamental environmental factors capable of impacting health [16, 32]. Air quality of indoor environments is one of the main factors affecting the health, wellbeing and productivity of people. The effect on health rises as exposure to and density of air

In indoor air environments (non-industrial), the most important source of airborne bacteria is the presence of humans (Kim and Kim, 2007). Major indoor activities such as talking, sneezing, coughing, etc. can concentrate airborne biological particulate matter in the indoor environ‐ ment. House dust, pets and their bedding material, wood materials and furniture stuffing could serve as reservoir from which spores of *Alternaria, Aspergillus, Botrytis, Cladosporium, Penicillium, Scopulariopsis* spp. and yeast cells are occasionally released into the indoor air [17].

Bioaerosols consist of aerosols containing microorganisms (bacteria, fungi, viruses) or organic compounds derived from microorganisms (endotoxins, metabolites, toxins and other micro‐ bial fragments) (Heikkienen*et al.,* 2005). Aerosols of biological origin form a significant portion of the total atmospheric aerosols, sometimes reaching up to 50% of all aerosol particles [37].

Bioaerosols vary in size (20 nm to >100 nm) and composition depending on the source, aerosolisation mechanisms and environmental conditions prevailing at the site [53]. The

no available information on the indoor air quality of living homes in the country.

**Plate 1.** Typical housing structure in urban (a and b) and rural (c and d) settings in Nigeria

Indoor air contains a complex mixture of bioaerosols such as fungi, bacteria and allergens along with non-biological particles (e.g., dust, smoke, particles generated by cooking, organic and Indoor air contains a complex mixture of bioaerosols such as fungi, bacteria and allergens along with non-biological particles (e.g., dust, smoke, particles generated by cooking, organic and inorganic gases) [33]. Airborne microorganisms might pose an environmental hazard when present in high concentrations in indoor environments resulting in health problems [68].

**Plate 1: Typical housing structure in urban (a and b) and rural (c and d) settings in Nigeria** 

inorganic gases) (Hargreaves *et al.,* 2003). Airborne microorganisms might pose an environmental hazard when present in high concentrations in indoor environments resulting in health problems (Stetzenbach *et al.,* 2004). Bioaersosols contribute to about 5%--34% of indoor air pollution [66]. The source of bioaerosols in indoor air includes furnishing and building materials, microbiological contamination within the walls and ceilings and floor activities. The outdoor environ‐

6

Bioaersosols contribute to about 5%--34% of indoor air pollution (Srikanth *et al.,* 2008). The source of bioaerosols in indoor air includes furnishing and building materials, microbiological

ments are oftentimes major sources of indoor bioaerosols as particles are transferred indoor through openings of the building envelope (windows, doors). However, one of the most important factors affecting indoor air quality is how the building is heated, ventilated, airconditioned and its occupancy [9].

#### **6.1. Bacteria in indoor air environment**

Airborne bacteria are major issues in indoor environments. The potential health risks resulting from exposure to airborne bacteria can occur at workplaces and residential locations [28]. A study conducted in Nigeria by [7] in day care centres, reported that the genera of bacteria isolated from the indoor environment included *Pseudomonas, Staphylococcus* and *Bacillus* spp., in both wet and dry seasons.

Elsewhere, the most important bacterial strains found in an indoor atmosphere are represen‐ tatives of the genera *Bacillus, Micrococcus, Kocuria and Staphylococcus, Streptomyces albus, Pantoea agglomerans, Pseudomonas chlororaphis, Arthrobacter globiformis, Thermoactinomyces vulgaris and Corynebacterium* spp.[23]. and wet surfaces of bathrooms and kitchen (Ojima et al., 2002). Water may also originate from leaks in plumbing or roof, or be a result of condensation or harsh rain or snowing (Speirs et al., 1995). Standing water is a potential source

of bacteria, and once disturbed, bacteria may become airborne (Speirs et al., 1995).

Cases Controls AIHA Guideline

#### Figure 3. Mean Indoor TBC among cases and controls as compared with AIHA Guideline Source: Ana et al., 2013

et al., 2002).

Source: Ana et al., 2013 **Figure 2.** Mean Indoor TBC among cases and controls as compared with AIHA Guideline

dry season Aspergillus , Penicillum , Geotricum and Fusarium spp.,

in indoor air, regardless of the type of surface (Grant et al., 1989).

contamination is dampness (Green et al., 2006).

6.2. Fungi in indoor air environments The building-associated fungi consist of filamentous microfungi (moulds) and yeasts. The most common fungal genera occurring in indoor environments are Penicillium, Aspergillus, Cladosporium, Alternaria and yeasts (Hyvärinen Also, in a study designed to determine the burden of airborne microbes in indoor environment that predispose children under the age of 5 to acute respiratory infections, the indoor airborne bacterial load among cases (9.6x102 cfu/m3 ) was higher than the acceptable limit

In the same study carried out by Ana and Umar, (2013) they showed that genera of fungi isolated in indoor environment of day care centres included Aspergillus, Penicillum , Geotricum , Fusarium and Candida spp., and in the

Their presence in indoor air is as a result of transportation from outside environment via building materials, carpets, furniture, wallpapers, etc. Ventilation and air-conditioning systems are another common way of penetraton of fungi into the buildings. The rate of further growth, spreading and multiplication depends exclusively on moisture content

Natural food source for fungi vary from plant, animal and human particles in house dust, to fragments of construction materials such as floor and wall textile coverings, furniture, residue of cooking traces, food storage and paper materials. Since these materials occur in good quantity in every building, and considering that optimal temperature for fungi growth ranges from 10–35 ºC, the only limiting factor for development of fungi and mould (≤5.0x10<sup>2</sup> cfu/m3 ) proposed by the American Industrial Hygiene Association (AIHA, 2001) for residential locations compared to controls (3.5x10<sup>2</sup> cfu/m3 ) [7] (Fig. 2).

Like fungi, bacterial growth takes place in the presence of sufficient moisture. In the indoor environments, sources of required moisture for microbial growth include drip pans of aircooling devices, freezers or refrigerator, humidifiers and wet surfaces of bathrooms and kitchen [45]. Water may also originate from leaks in plumbing or roof, or be a result of condensation or harsh rain or snowing [65]. Standing water is a potential source of bacteria, and once disturbed, bacteria may become airborne [65].

#### **6.2. Fungi in indoor air environments**

ments are oftentimes major sources of indoor bioaerosols as particles are transferred indoor through openings of the building envelope (windows, doors). However, one of the most important factors affecting indoor air quality is how the building is heated, ventilated, air-

Airborne bacteria are major issues in indoor environments. The potential health risks resulting from exposure to airborne bacteria can occur at workplaces and residential locations [28]. A study conducted in Nigeria by [7] in day care centres, reported that the genera of bacteria isolated from the indoor environment included *Pseudomonas, Staphylococcus* and *Bacillus* spp.,

Elsewhere, the most important bacterial strains found in an indoor atmosphere are represen‐ tatives of the genera *Bacillus, Micrococcus, Kocuria and Staphylococcus, Streptomyces albus, Pantoea agglomerans, Pseudomonas chlororaphis, Arthrobacter globiformis, Thermoactinomyces vulgaris and Corynebacterium* spp.[23]. and wet surfaces of bathrooms and kitchen (Ojima et al., 2002). Water may also originate from leaks in plumbing or roof, or be a result of condensation or harsh rain or snowing (Speirs et al., 1995). Standing water is a potential source

of bacteria, and once disturbed, bacteria may become airborne (Speirs et al., 1995).

Figure 3. Mean Indoor TBC among cases and controls as compared with AIHA Guideline

**Figure 2.** Mean Indoor TBC among cases and controls as compared with AIHA Guideline

The building-associated fungi consist of filamentous microfungi (moulds) and yeasts. The most common fungal genera occurring in indoor environments are Penicillium, Aspergillus, Cladosporium, Alternaria and yeasts (Hyvärinen

cfu/m3

Also, in a study designed to determine the burden of airborne microbes in indoor environment that predispose children under the age of 5 to acute respiratory infections, the indoor airborne

Cases Controls AIHA Guideline

Cases Controls AIHA Guideline

) was higher than the acceptable limit

Category

In the same study carried out by Ana and Umar, (2013) they showed that genera of fungi isolated in indoor environment of day care centres included Aspergillus, Penicillum , Geotricum , Fusarium and Candida spp., and in the

Their presence in indoor air is as a result of transportation from outside environment via building materials, carpets, furniture, wallpapers, etc. Ventilation and air-conditioning systems are another common way of penetraton of fungi into the buildings. The rate of further growth, spreading and multiplication depends exclusively on moisture content

Natural food source for fungi vary from plant, animal and human particles in house dust, to fragments of construction materials such as floor and wall textile coverings, furniture, residue of cooking traces, food storage and paper materials. Since these materials occur in good quantity in every building, and considering that optimal temperature for fungi growth ranges from 10–35 ºC, the only limiting factor for development of fungi and mould

Source: Ana et al., 2013

Source: Ana et al., 2013

0

200

400

600

800

Indoor TBC (CFU/m³)

1000

1200

et al., 2002).

6.2. Fungi in indoor air environments

bacterial load among cases (9.6x102

contamination is dampness (Green et al., 2006).

dry season Aspergillus , Penicillum , Geotricum and Fusarium spp.,

in indoor air, regardless of the type of surface (Grant et al., 1989).

conditioned and its occupancy [9].

552 Current Air Quality Issues

in both wet and dry seasons.

**6.1. Bacteria in indoor air environment**

The building-associated fungi consist of filamentous microfungi (moulds) and yeasts. The most common fungal genera occurring in indoor environments are *Penicillium*, *Aspergillus*, *Cladosporium*, *Alternaria* and yeasts [36].

In the same study carried out by [6] they showed that genera of fungi isolated in indoor environment of day care centres included *Aspergillus, Penicillum, Geotricum, Fusarium* and *Candida* spp., and in the dry season *Aspergillus, Penicillum, Geotricum* and *Fusarium* spp.,

Their presence in indoor air is as a result of transportation from outside environment via building materials, carpets, furniture, wallpapers, etc. Ventilation and air-conditioning systems are another common way of penetraton of fungi into the buildings. The rate of further growth, spreading and multiplication depends exclusively on moisture content in indoor air, regardless of the type of surface [30].

Natural food source for fungi vary from plant, animal and human particles in house dust, to fragments of construction materials such as floor and wall textile coverings, furniture, residue of cooking traces, food storage and paper materials. Since these materials occur in good quantity in every building, and considering that optimal temperature for fungi growth ranges from 10–35 ºC, the only limiting factor for development of fungi and mould contamination is dampness [31].

Fungi may be extremely harmful for human health, but may also destroy the building itself (Figure 4.), particularly wooden parts, such as roofs and other materials. Some fungi species produce strong allergens, which initiate immune reaction type I (IgE mediated). For example, the indoor contamination with *Alternaria, Penicillium, Aspergillus* and *Cladosporium* spp., is related to asthma and other allergic respiratory diseases. Some of these species, such as *Penicillium* and *Aspergillus* can also induce type III allergy (IgG mediated), while at high concentrations, may also initiate combined type III and IV reaction manifested as hypersensi‐ tivity pneumonitis. Major fungal allergens are isolated and identified (such as Cla h I from *Cladosporium herbarum*, Alt a I and Alt a II from *Alternaria alternata* and Asp f I and Asp f III from *Aspergillus fumigatus*) [22].

Fungi mycotoxins have strong genotoxic, carcinogenic and immunotoxic potential. The carcinogenic effects of aflatoxin (mycotoxin produced by *Aspergillus flavus* and *Aspergillus parasiticus*) are well known. The most important mycotoxins related to indoor air contamina‐ tion are trichothecenes, generated by fungi *Stachybotrys chartarum* (macrocyclic trichothecenes, trichodermin, sterigmatocystin and satratoxin G) [10].

**Plate 2: Fungi on the wall and ceiling of a typical indoor environment Plate 2.** Fungi on the wall and ceiling of a typical indoor environment

#### **6.3. Viruses in indoor environment**

**6.3 Viruses in Indoor Environment**  Viruses are small (20--400 nm), obligate intracellular parasites. They represent a common cause Viruses are small (20-400 nm), obligate intracellular parasites. They represent a common cause of infectious disease acquired indoors, as they are easily transmitted especially in crowded, poorly ventilated environments [72].

of infectious disease acquired indoors, as they are easily transmitted especially in crowded, poorly ventilated environments (Verreault *et al.,* 2008). Airborne transmission of viral agents occurs when viruses travel on relatively large respiratory droplets (> 10 μm) that people sneeze, cough or exhale during conversation or breathing Airborne transmission of viral agents occurs when viruses travel on relatively large respiratory droplets (> 10 µm) that people sneeze, cough or exhale during conversation or breathing (primary aerosolisation). A single cough can release hundreds of droplets while a single sneeze can release about 40 000 droplets at speeds of up to 50--200 miles per hour with each droplet containing millions of viral particles. Aerosol droplets travel only short distances (1-2 meters) before settlings on surfaces, where viruses can remain infectious for hours or days.

(primary aerosolisation). A single cough can release hundreds of droplets while a single sneeze can release about 40 000 droplets at speeds of up to 50--200 miles per hour with each droplet containing millions of viral particles. Aerosol droplets travel only short distances (1--2 meters) before settlings on surfaces, where viruses can remain infectious for hours or days. Poorly ventilated and crowded indoor environments are favourable conditions for viral transmission. Hospitals, in particular, are environments where viral aerosols can be particu‐ larly hazardous, since patients tend to be especially prone to infection due to pre-existing illness. Elderly patients, children, cancer patients, immunocompromised or immunosup‐ pressed patients are most at risk.

#### Poorly ventilated and crowded indoor environments are favourable conditions for viral **6.4. Protozoa in indoor environment**

transmission. Hospitals, in particular, are environments where viral aerosols can be particularly hazardous, since patients tend to be especially prone to infection due to pre-existing illness. Elderly patients, children, cancer patients, immunocompromised or immunosuppressed patients are most at risk. Protozoa may also be present in indoor air in damp buildings. [77] detected amoebae in 22% of the 124 samples of various materials collected from buildings with evident mois‐ ture damage. Field studies on the presence and concentrations of protozoa in indoor air, as well as health aspects of these microorganisms in given conditions, are still lacking, with

9

the exception of one in vitro study conducted by the same authors, who suggested that amoebae act synergistically with certain bacteria, enhancing their cytotoxic and proinflammatory potential [78].
