**8. Indoor environmental risk factors for respiratory conditions**

#### **8.1. Overcrowding**

tion are trichothecenes, generated by fungi *Stachybotrys chartarum* (macrocyclic trichothecenes,

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

9

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,

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,

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)

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‐

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)

Poorly ventilated and crowded indoor environments are favourable conditions for viral 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

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

before settlings on surfaces, where viruses can remain infectious for hours or days.

before settlings on surfaces, where viruses can remain infectious for hours or days.

trichodermin, sterigmatocystin and satratoxin G) [10].

554 Current Air Quality Issues

**6.3 Viruses in Indoor Environment** 

**6.3. Viruses in indoor environment**

poorly ventilated environments [72].

pressed patients are most at risk.

**6.4. Protozoa in indoor environment**

are most at risk.

poorly ventilated environments (Verreault *et al.,* 2008).

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

Many children are exposed to very crowded conditions at home, schools (Figure 5.) etc., and this increases risk of transmission of illness. Most studies in developing countries have found that the average area of habitable space per person is well below the WHO recommendation of 12m2 [15].

According to a study by [7], the mean number of occupancy among children under the age of 5 admitted in a tertiary health facility for ARIs was 6.0±1.5 as compared to 4.0±1.0 among controls. A positive association was found between the level of occupancy and indoor total bacterial count. A similar study by [70] recorded the highest bacterial burden in an over‐ crowded environment. This suggests that the number of persons in the household is directly proportional to the level of bacteria build-up in the indoor environment.

#### **8.2. Environmental tobacco smoke among parents**

More than 150 published studies have shown a significant relationship between Environmen‐ tal Tobacco Smoke (ETS) and respiratory illness in children. Meta-analyses revealed a strong evidence for associations between both prenatal maternal smoking and postnatal ETS exposure and risk of ARI in children [21].

[6] in their study indicated that parental smoking or any other smoker in the house as a risk factor for ARIs in children under the age of 5 (OR = 4.7; CI = 0.9-2.17, p<0.05). This could be due to the accumulation of emissions from cigarette smoking in the indoor environment as a result of inadequate ventilation [13].

#### **8.3. Household biomass fuel**

Biomass fuel is any material derived from plants or animals which is deliberately burnt by humans. Firewood combustion for cooking is a common practice in most rural communities of developing nations including Nigeria [4]. Majority of the households burn biomass fuels in open fireplaces, consisting of simple arrangements as three rocks (Figure 7.), a U-shaped hole in a block of clay, a pit in the ground or in poorly functioning earth or metal stoves. The process of combustion in most of these stoves is incomplete, resulting in substantial emissions which, in the presence of poor ventilation, produce very high levels of indoor pollution (WHO, 2000).

**Plate 3.** Overcrowding condition in a typical school setting

Many of the substances in biomass smoke have adverse health effects. The most important ones are carbon monoxide, nitrous oxides, sulphur oxides, formaldehyde and polycyclic organic matter, including carcinogens such as benzo[a]pyrene. Particles with diameters <10 microns (PM10), and particularly those <2.5 microns in diameter (PM2.5), can penetrate deeply into the lungs (USEPA, 1997).

A Nigerian study on the concentration of indoor air pollutants due to the use of firewood for cooking and its effects on the lung function of women living in the selected homes found that the concentration of PM10 and gaseous emissions such as CO and NO2 significantly exceeded the WHO limits by several folds. Chronic exposure to high level of the indoor air pollutants particularly the respirable particulate matter could possibly compromise the lung function status of women [4].

[47] in their study of the effects of stove intervention on household air pollution and the respiratory health of women and children in rural Nigeria, demonstrated an association between cooking with biomass fuel, increased prevalence of respiratory symptoms and presence of obstructive lung disease. The high frequency of respirator y and other exposurerelated symptoms seen in mothers and children at baseline (pre-intervention) were substan‐ tially reduced a year later following replacement of the traditional stoves with low-emission stoves (Fig.3). This observation is consistent with the report of higher frequency of respiratory symptoms, especially cough in women exposed to biomass smoke in Mozambique [24], Nepal [60], Pakistan [61], Mexico [56] and Guatemala [20, 64].

Although the incidence of some respiratory symptoms may be lower in children compared to mothers, it is evident that the children are also exposed to the same PM2.5 and CO levels, as 94.1% of the mothers always have their children with them during cooking [47]. Studies have also suggested that children exposed to household air pollution early in life may have impaired lung development, indicating that the impact of exposure to biomass smoke may continue into adulthood [2].

Source: Oluwole et al., 2013

[6] in their study indicated that parental smoking or any other smoker in the house as a risk factor for ARIs in children under the age of 5 (OR = 4.7; CI = 0.9-2.17, p<0.05). This could be due to the accumulation of emissions from cigarette smoking in the indoor environment as a

Biomass fuel is any material derived from plants or animals which is deliberately burnt by humans. Firewood combustion for cooking is a common practice in most rural communities of developing nations including Nigeria [4]. Majority of the households burn biomass fuels in open fireplaces, consisting of simple arrangements as three rocks (Figure 7.), a U-shaped hole in a block of clay, a pit in the ground or in poorly functioning earth or metal stoves. The process of combustion in most of these stoves is incomplete, resulting in substantial emissions which, in the presence of poor ventilation, produce very high levels of indoor pollution (WHO, 2000).

Many of the substances in biomass smoke have adverse health effects. The most important ones are carbon monoxide, nitrous oxides, sulphur oxides, formaldehyde and polycyclic organic matter, including carcinogens such as benzo[a]pyrene. Particles with diameters <10 microns (PM10), and particularly those <2.5 microns in diameter (PM2.5), can penetrate deeply

result of inadequate ventilation [13].

**Plate 3.** Overcrowding condition in a typical school setting

into the lungs (USEPA, 1997).

**8.3. Household biomass fuel**

556 Current Air Quality Issues

**Figure 3.** Comparison of household particulate matter (a) and carbon monoxide (b) concentration levels before and 1 year after distribution and monitored use of low-emission stoves. The dotted lines represent WHO recommended lev‐ els. It has been highlighted to show that cooking time concentrations of PM2.5 and CO in all households sampled were significantly above the recommended levels before distribution and monitored use of low-emission cooking stoves

Over 40 % of the participating mothers and children in our study had mild to moderate obstructive defects. This impaired lung function is likely caused by particulate matter (PM) in firewood smoke, which is believed to induce oxidative injury through its ability to carry adherent metals into the lungs and cause inflammation [57].

**Plate 4.** Simple arrangement of three stones where biomass burns in an indoor environment

Exposure to these pollutants is reported to be higher in women and children (Figure 8.) [1, 11]. It has been shown that exposure to biomass fuel smoke is responsible for a number of respiratory diseases such as Acute Respiratory Infections (ARI), Chronic Obstructive Pulmo‐ nary Disease (COPD), Tuberculosis and Asthma; Low Birth Weight; Cataract and Blindness [14]. The adverse effects on respiratory health of products of incomplete solid-fuel combustion are summarized in Table 1.


**Table 1.** Adverse effects on respiratory health associated with indoor air pollution

Source: Oluwole et al., 2013

firewood smoke, which is believed to induce oxidative injury through its ability to carry

adherent metals into the lungs and cause inflammation [57].

**Plate 4.** Simple arrangement of three stones where biomass burns in an indoor environment

Carbon monoxide Low birth weight, increase in perinatal deaths.

**Table 1.** Adverse effects on respiratory health associated with indoor air pollution

Polycyclic aromatic hydrocarbons Lung cancer, cancer of mouth, nasopharynx and larynx.

Exposure to these pollutants is reported to be higher in women and children (Figure 8.) [1, 11]. It has been shown that exposure to biomass fuel smoke is responsible for a number of respiratory diseases such as Acute Respiratory Infections (ARI), Chronic Obstructive Pulmo‐ nary Disease (COPD), Tuberculosis and Asthma; Low Birth Weight; Cataract and Blindness [14]. The adverse effects on respiratory health of products of incomplete solid-fuel combustion

**Compound Potential Health Effect**

Breathable particulate matter Wheezing, exacerbation of asthma, respiratory infections, chronic

Nitrogen oxides Wheezing, exacerbation of asthma, respiratory infections, reduced lung function in children.

Sulphur oxides Wheezing, exacerbation of asthma, exacerbation of chronic obstructive

pulmonary disease, cardiovascular disease.

bronchitis and chronic obstructive pulmonary disease.

Source: Oluwole et al., 2013

558 Current Air Quality Issues

are summarized in Table 1.

Source: Perez et al., 2011

**Plate 5.** Mother and child exposed to biomass emissions in an indoor environment

#### **8.4. Dampness in indoor environments**

Numerous studies have examined the potential association between damp housing conditions and respiratory ailments among occupants. It was discovered that increase humidity leads to increase mould growth and exposure, which could result in asthma and other respiratory conditions. The presence of home dampness has been reported to affect about 38% of Canadian homes [18]. A Canadian study found that children living in damp or mouldy homes were 32% more likely to have bronchitis [18] (secure.cihi.ca). Substantial problems have been identified in some First Nations communities due to a combination of inappropriate housing design, poor construction, inadequate maintenance and poor ventilation [41].

#### **8.5. House dust mites and cockroaches in indoor environments**

House Dust Mites (HDMs) thrive in the dust of homes, particularly in the presence of high indoor relative humidity (secure.cihi.ca). In order to survive and multiply they require a relative humidity in excess of 45%–50%, but their activity, including feeding and maturation is more rapid at higher rates of relative humidity, which was confirmed in field studies [79].

Cockroaches are implicated as a major cause of asthma among inner city children in the U.S., resulting in increased hospital admissions, school absenteeism, and unscheduled medical visits for asthma [58].

#### **8.6. Sanitation and housing quality** hospital admissions, school absenteeism, and unscheduled medical visits for asthma (Rosenstreich et al., 1997).

[15] found that children with respiratory illness come from houses with poorer sanitation than controls, while in developed countries promotion of hand washing has been associated with reduced incidence of respiratory illness. 8.6. Sanitation and housing quality Cardoso et al., (2004) found that children with respiratory illness come from houses with poorer sanitation than controls, while in developed countries promotion of hand washing has been associated with reduced incidence of

activity, including feeding and maturation is more rapid at higher rates of relative humidity, which was confirmed in

Cockroaches are implicated as a major cause of asthma among inner city children in the U.S., resulting in increased

#### **8.7. Indoor air meteorological conditions** respiratory illness.

A case-control study carried out in Ibadan among houses of children under the age of 5 revealed that a higher proportion of houses visited among cases and controls recorded indoor relative humidity (RH) values above the comfort level (30%–60%)(Fig. 4). The high RH (above comfort level) observed among a large proportion of houses among cases could be as a result of high moisture content. The mean indoor and outdoor air RH among cases (69.6 ± 4.7; 67.2 ± 5.0) was found to be higher than among controls (63.1 ± 6.5; 66.1 ± 7.1) [7]. With such high relative humidity levels, microorganisms such as fungi and bacteria can survive on non-living materials including dusts (Choa *et al.,* 2002). High relative humidity above 70% also tends to favour the survival of viruses that infect the membrane of the respiratory tract. 8.7. Indoor air meteorological conditions A case-control study carried out in Ibadan among houses of children under the age of 5 revealed that a higher proportion of houses visited among cases and controls recorded indoor relative humidity (RH) values above the comfort level (30%–60%)(Fig. 4). The high RH (above comfort level) observed among a large proportion of houses among cases could be as a result of high moisture content. The mean indoor and outdoor air RH among cases (69.6 ± 4.7; 67.2 ± 5.0) was found to be higher than among controls (63.1 ± 6.5; 66.1 ± 7.1) (Ana et al., 2013). With such high relative humidity levels, microorganisms such as fungi and bacteria can survive on non-living materials including dusts (Choa et al., 2002). High relative humidity above 70% also tends to favour the survival of viruses that infect the membrane of the respiratory tract.

#### **8.8. Inhalable particulate matter burden** 8.8. Inhalable particulate matter burden

Particulate matter (PM) has been recognized in recent years as the most dangerous and widely spread air pollutant [43] affecting more people than any other pollutant and contributing to the risk of developing cardiovascular and respiratory diseases, as well as lung cancer. PM10 is associated with increased mortality and morbidity in many cities worldwide and the risk is greatly pronounced among susceptible populations, including the elderly, children and people with pre-existing health conditions [55]. Particulate matter (PM) has been recognized in recent years as the most dangerous and widely spread air pollutant (Manandhar et al., 2010) affecting more people than any other pollutant and contributing to the risk of developing cardiovascular and respiratory diseases, as well as lung cancer. PM10 is associated with increased mortality and morbidity in many cities worldwide and the risk is greatly pronounced among susceptible populations, including the elderly, children and people with pre-existing health conditions (Pudpong et al., 2011).

Key: Low = <30%, Comfort = 30 – 60%, High = >60% Source: Ana et al, 2013

Figure 9. Indoor relative humidity for houses among cases and controls **Figure 4.** Indoor relative humidity for houses among cases and controls

[6] in their study of inhalable particulate matter burden in selected day care centres in Ibadan, Nigeria, observed that the mean indoor PM10 readings for wet season (73.4 ± 54.4µg/m³) and dry season (296.3 ± 61.6µg/m³) significantly exceeded the WHO guideline limit of 50µg/m³ (Table 2).The indoor/outdoor PM10 ratio was 1.38 ± 0.97 and being greater than 1 indicated a possible indoor source of pollution. High particulate matter concentration observed was indicative of the poor indoor air quality condition in the day care centres.


**Table 2.** Indoor particulate matter concentration in the wet and dry seasons
