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Review

Impact of Indoor Air Pollution in Pakistan—Causes and Management

by
Ayesha Kausar
1,2,3,*,
Ishaq Ahmad
1,2,3,
Tianle Zhu
4 and
Hassan Shahzad
3
1
NPU-NCP Joint International Research Center on Advanced Nanomaterials and Defects Engineering, Northwestern Polytechnical University, Xi’an 710072, China
2
UNESCO-UNISA Africa Chair in Nanosciences/Nanotechnology, iThemba LABS, Somerset West 7129, South Africa
3
NPU-NCP Joint International Research Center on Advanced Nanomaterials and Defects Engineering, National Centre for Physics, Islamabad 44000, Pakistan
4
School of Space and Environment, Beihang University, Beijing 100191, China
*
Author to whom correspondence should be addressed.
Pollutants 2023, 3(2), 293-319; https://doi.org/10.3390/pollutants3020021
Submission received: 21 February 2023 / Revised: 18 March 2023 / Accepted: 2 June 2023 / Published: 6 June 2023
(This article belongs to the Section Air Pollution)
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Abstract

:
This state-of-the-art review is designed to provide a factual analysis of indoor air pollution in Pakistan. Primarily, the main sources of indoor air pollution and related air pollutants were analyzed. Key sources of indoor air pollution include household energy sources (biomass, wood, coal, tobacco, and low temperatures) producing particulate matter (PM), dust particles, smoke, COx, noxious gases, bioaerosols, airborne microflora, and flame retardants. According to the literature, rural regions of Pakistan using biomass indoor fuels have a high indoor PM concentration in the range of 4000–9000 μg/m3. In rural/urban regions, indoor smoking also leads to high PM2.5 levels of ~1800 μg/m3, which can cause pulmonary infections. In hospitals, PM concentrations were detected up to 1000 μg/m3, causing repeated infections in patients. Indoor ingestion of dust containing polychlorinated biphenyl concentrations was observed at high levels (~8.79–34.39 ng/g) in cities; this can cause serious health effects such as cancer risks and a loss of working productivity. Moreover, indoor microflora and bacteria (~10,000–15,000 cfu m−3) in urban/rural regions cause respiratory/cancer risks. In this context, indoor air quality (IAQ) monitoring and management strategies have been somewhat developed; however, their implementation in Pakistan’s rural/urban indoor environments is still needed. Various challenges were identified for monitoring/regulating IAQ. There is a firm need for industry–academia–research cooperation and for the involvement of government/agencies to support indoor air pollution control/management and for intervention strategies.

Graphical Abstract

1. Introduction

Indoor air pollution has become a global challenge due to increasing health hazards and socio-economic risks [1]. In developing countries such as Pakistan, the lack of an appropriate analysis of indoor air quality (IAQ) management and protection strategies has caused health and economic risks. Indoor activities such as cooking, heating, cleaning, smoking, use of building materials, as well as the infiltration of outdoor air continuously increase the indoor air pollution level [2]. The choice of household fuel (biomass, wood, coal, charcoal, crop residue, animal dung, etc.) can contribute to >80% of indoor pollution. In recent decades, concentrations of major indoor air pollutants (particulate matter (PM), gaseous pollutants, dust, smoke, and bioaerosols) have been continuously increasing in Pakistan [3,4]. Consequently, rising indoor pollutant concentrations have resulted in numerous diseases including respiratory, asthmatic, allergic, cardiovascular, carcinogenic, and other health issues [5,6]. According to the World Health Organization (WHO), indoor air pollution has increased the annual disease burden and mortality rate in Pakistan [7]. For example, safe PM2.5 and PM10 concentrations levels are 25 μg/m3 and 50 μg/m3, respectively (as per WHO). The safe concentration level for ozone is ~150–200 μg/m3. Similarly, WHO provides safe indoor levels for various other indoor pollutants. Subsequently, the implementation of IAQ management policies, monitoring devices, and sustainable WHO solutions are key challenges for improving IAQ in Pakistan [8,9,10]. In this context, IAQ sensing systems [11,12,13], filtration/adsorption media [14,15,16], UV photocatalysts [17], and advanced techniques need to be adopted in Pakistan.
In this novel, state-of-the art, and comprehensive review, the current situation of IAQ in Pakistan was analyzed using multiple occurrences of indoor air pollution around the major cities and rural regions of Pakistan. Key sources of indoor air pollution, primary pollutants, and health effects were surveyed. Consequently, the necessity of IAQ assessment, control, and monitoring technologies was analyzed. The involvement of academic/research institutes, government organizations, and stakeholders for long-term planned studies on indoor air pollution was found to be crucial. In this context, linking indoor air control/management to appropriate policy interventions (as per WHO standards) is also indispensable.
Recent strategies need to be focused for eradicating essential indoor pollutants and for IAQ control and monitoring in Pakistan. Using advanced materials in these technologies can offer a promising way to improve IAQ. In this context, various nanomaterials, membranes, nanoporous materials, nanohybrids, and polymeric nanocomposites can be designed and employed to reduce indoor pollution. The future of IAQ control/monitoring in Pakistan depends on using advanced nanomaterial-based sensing, filtration/adsorption, and photocatalysts to remove indoor pollutants. Subsequently, key pollutants, health effects, and control methods need to be analyzed in Pakistan. In this context, there are some reports in the previous literature that have studied indoor pollution in Pakistan but not in an updated form which depicts the current state. Among related studies, a minireview was undertaken by Colbeck et al. [18] in 2010. However, the article was published more than a decade ago, and contains analyses of few research reports, probably due to the limited available data at that time. Poor IAQ in Pakistan was attributed to wood-based fuel and indoor smoking, and few directions were proposed for improving the situation. However, the implementation of legislation on tobacco smoking in public places and the adoption of safe fuel were suggested. As compared to previous studies, our review presents a recent sketch of the state of IAQ in Pakistan with comprehensive coverage of the literature, knowledge, and the needs of policy implementations to remove indoor air pollution. However, as compared to past decades, there has not been much improvement in IAQ in Pakistan, especially in rural areas. There is still a need for safe indoor fuel choices, stoves producing less smoke, house designs with separate kitchens, and public awareness regarding smoking.
To the best of our knowledge, such a specific recent review on indoor pollution in Pakistan, with a well-arranged outline and an in-depth interpretation of recent publications, has not been seen in the literature before. The novelty of this review depends upon innovative topic selection and arrangement to form a framework and on the inclusion of all possible relevant studies of the indoor pollution situation in Pakistan. Moreover, the included literature is comprehensively discussed to depict the situation of indoor pollution. On this review topic, some previous research reports have been observed, nevertheless, the reported literature is not in a compiled and updated form that portrays the current state of IAQ in Pakistan. For this particular review, the literature was obtained from various databases such as Scopus, Science Direct, Web of Science, etc., because limited studies have been carried out regarding indoor air pollution in Pakistan. It is not possible for researchers to make future developments regarding IAQ management in Pakistan without access to prior knowledge of the recent literature. Accordingly, the relevant literature published between 2016 and 2023 in the Scopus database is shown in Figure 1.

2. Indoor Air Pollution

The indoor environmental conditions in residential buildings, educational, and work places directly affect human health [19]. According to the WHO, indoor air pollution may affect ~4–5 million people per year worldwide [20]. Most of rural and urban humans spend 90% of their time indoors [21]. Human activities, construction materials, and outdoor air have been major sources of indoor pollution [22,23,24]. The resulting indoor pollutants have been identified as PM, noxious gases, bacteria, fungi, insects, etc. [25,26,27]. The major indoor toxic gases involve the oxides of carbon (COx) (carbon monoxide (CO) and carbon dioxide (CO2)) [28], oxides of nitrogen (NOx) (nitric oxide (NO) and nitrogen dioxide (NO2)) [29,30], oxides of sulfur (SOx) (sulfur dioxide (SO2)) [31], PM [32,33,34], radon [35,36], volatile organic matter (VOC) [37], carbonaceous aerosols/biological aerosols/microorganisms (bacteria, viruses, fungi) [38,39,40], and pesticides [41]. Common human health effects observed due to indoor pollutants comprise respiratory diseases, allergic diseases, lung cancer, nervous system malfunctioning, kidney cancer, and cardiovascular diseases [42]. The succeeding sections of this review cover various sources as well as pollutants in indoor environments in the rural/urban regions of Pakistan.

3. Sources and Key Indoor Air Pollutants in Pakistan

This section of the review analyzes the key indoor air pollutants and their sources in Pakistan. This points towards the current indoor pollution situation in the rural/urban areas of Pakistan and also the desired steps to improve the IAQ levels (Figure 2).

3.1. Indoor Particulate Matter and Dust Ingestion

Among indoor pollutants, PM has been considered as the most abundant contaminant [43,44,45]. Here, PM2.5 and PM10 were identified as important indoor air pollutants [46,47,48]. According to a study on the indoor environment of Lahore city, a rise in PM2.5 concentration in the outdoor air improved the indoor pollution [49]. The study was conducted between the period of 2019 and 2020. To realize the current situation of air pollution in Lahore, the PM2.5 concentration data were obtained as well as evaluated (WHO standard PM2.5 concentrations ~25 μg/m3). The industrial growth, traffic, and seasonal changes were the main contributing factors to indoor pollution [50,51]. During winter and post-monsoon season in Lahore, the high PM concentrations have been observed due to the excessive burning of plant residues [52]. The needs of monitoring indoor/outdoor air quality using IAQ equipment and policy implementation have been analyzed in Pakistan.
Subsequently, the literature reports have shown an abundant generation of PM2.5 and PM10 in indoor environments in Pakistan [53]. Nafees et al. [54] investigated the rise in indoor PM2.5 levels in the restaurants/cafés/clubs in Karachi. According to indoor monitoring results, the PM2.5 level was observed in the range of 25–390 μg/m3. The increasing indoor pollutant levels were attributed to indoor hospitality, smoking, and public gatherings. Using biomass fuels in kitchens mainly contributed to indoor pollution in rural and semi-urban areas in Pakistan [55,56]. The rising PM10 and PM2.5 concentrations in kitchens and associated living rooms have been investigated [57]. Accordingly, the indoor biomass smoke has increased the health risks [58]. Colbeck et al. [59] evaluated indoor pollution due to PM10, PM2.5, and PM1 in rural areas of Pakistan.. The kitchens using biomass fuel had PM10, PM2.5, and PM1 concentrations of 3.80, 4.36, and 4.11, respectively. The mass concentrations of particles (PM10, PM2.5, PM1) were monitored using the GRIMM aerosol spectrometer Model 1.108 and Model 1.101 (Grimm Aerosol Technik GmbH, Ainring, Germany) devices. The GRIMM monitors showed a sensitivity of ~ 1 particle/liter with a reproducibility of ±2%. The high PM concentration levels were observed in the range of 4000–8555 μg/m3. The other sources for rising PM levels were identified in the form of cleaning and smoking in the kitchenette and living areas [60]. Junaid et al. [61] discovered higher indoor PM concentrations in rural/urban areas, as compared with the WHO standards for PM10 (50 μg/m3) and PM2.5 (25 μg/m3) levels. The >50% population fulfil their energy needs by the indoor conventional biomass burning. The rising indoor PM levels also revealed high respiratory and mortality rates in Pakistan [62]. In the same way as Pakistan, the indoor air pollution has been examined for other developing South Asian countries (having similar indoor conditions) such as Nepal, Bangladesh, Bhutan, etc. [63].
A few of the latest studies have better analyzed the situation of indoor pollution in Pakistan [7,17,64]. Asghar et al. [65] studied PM as a major source of air pollution in Haripur city, Pakistan. The Youngteng yt-hpc 3000a handle particulate counter was used to measure the PM2.5 and PM10 concentrations. The sensors installed in these devices automatically detected the PM levels and displayed readings on the device screen. The permissible limits for the PM2.5 and PM10 were ~35 µg/m3 and 150 µg/m3, respectively (as per standards of the Environmental Protection Agency Pakistan). The PM2.5 hourly mean concentrations increased in the range of 23.7–126.0 μg/m3, whereas the PM10 concentrations rose from 39.0 to 166.3 μg/m3. The outside traffic in Haripur caused high indoor concentrations of PM2.5 and PM10. Furthermore, the high PM levels led to respiratory infections in the population. Aslam et al. [66] measured the PM2.5, PM10, CO, NO2, SO2, and O3 concentrations in different places in Lahore city. The industrial and vehicle emissions in the outside environment were found to improve the indoor pollution and led to epidemiological and asthma problems. A total of 64% of asthma patients were reported in Lahore hospitals, which mainly included females involved in indoor activities. Jiao et al. [67] studied the PM1, PM2.5, and PM10 concentrations in residents near brick kilns in specific locations in Northern Pakistan. The high PM1, PM2.5, and PM10 concentrations were studied as 3377, 2305, and 3567.67 µg/m3, respectively. The PM levels were found to be higher than the Pakistan National Environmental Quality Standards, which caused serious health risks such as respiratory diseases and asthma problems [68].
In the developing countries, dust is an important factor contributing to the indoor air pollution. The major sources for dust include the outside traffic/human activities, indoor electronics, building materials used, as well as pest control actions [69,70,71]. The indoor furniture, sofas, carpets, etc., contribute to >80% of indoor dust [72]. Ali and co-workers [73] investigated the indoor dust as the major source of organic contaminants in rural areas. The flame retardants/pesticides such as polybrominated diphenyl ether, polychlorinated biphenyl, tri-(2-butoxyethyl)phosphate, and triphenyl phosphate were detected in the indoor dust. For adults and toddlers, the dust ingestion levels were found to be high, ~0.65 and 15.2 ng/kg bw/day, respectively [74]. Khalid et al. [75] found polychlorinated biphenyls as the main organic pollutants in the indoor dust of Lahore, Faisalabad, and Bahawalnagar. The concentrations of polychlorinated biphenyl were observed as about 34.39 ng/g, 9.94 ng/g, and 8.79 ng/g for Lahore, Faisalabad, and Bahawalnagar, respectively. Hence, the dust ingestion caused health effects such as skin damage, liver/gastrointestinal diseases, immune/nervous system ailments, and cancer risks [76,77].

3.2. Indoor Smoke, COx, VOC, and Pollutants from Household Energy Sources, Tobacco, and Building Materials

Around three billion of the world’s population in developing countries depend on biomass to meet their household energy needs [78,79,80]. Relative to the developed countries, the indoor air pollution levels have been found to be quite high in developing countries [81]. Using biomass fuel, wood, coal, crop residues, animal dung, etc., produced high amounts of COx, CO, and VOC in the indoor air [82]. Due to indoor pollution, the increasing risks of chronic respiratory and cardiac diseases were observed in the developing countries [83]. Pakistan is a predominantly rural country having an average family size of five to seven members [84]. As per an estimate, about 90% of the rural and 50% of the urban population rely on biomass fuels in Pakistan [85,86,87]. However, this consumption was decreased for the population with improved income and economic conditions [88]. Hence, the biomass households were mostly found among the low-income population in developing countries (Figure 3). In urban areas, clean and efficient indoor energy sources such as liquified petroleum gas and electricity were used.
Biomass fuel is consumed in almost all provinces of Pakistan including Punjab, Sindh, Baluchistan, and Khyber Pakhtunkhwa. The wood as a fuel was used for households in the rural regions of Baluchistan, whereas the rural regions in Panjab utilized crop residues [89]. Similar indoor fuels were consumed in the rural regions of Khyber Pakhtunkhwa. In Sindh rural regions, wood, coal, crop residues, animal dung, and agricultural waste were employed to fulfil the indoor energy needs [90]. Here, the biomass consumption was observed as lower than that of Baluchistan due to urbanization [91,92,93]. Ahmed et al. [94] performed a comparative analysis on the fuel types used in the South Asian countries (Pakistan, India, and Bangladesh). Figure 4 shows indoor cooking fuels used in Pakistan, India, and Bangladesh. The statistical relationship between the indoor cooking fuel and women’s health has been studied [95]. The choice of an appropriate cooking fuel was the top concern to maintain the human health [96].
Nasir et al. [97] suggested that the household solid fuel was responsible for the indoor pollution, due to COx and VOC production in large amounts. According to this study, poverty played an important role in selecting an inappropriate fuel and causing indoor pollution [98]. Therefore, the increasing need for sustainable intervention strategies has been analyzed for reducing the indoor pollution [99]. Khan et al. [100] surveyed cross-sectional data from Pakistan (rural regions) for employing wood, crop residues, charcoal, coal, kerosene, and animal dung. Due to unhealthy indoor fuel producing excessive amounts of CO2 and CO, acute ailments and respiratory infections were observed in children (under five years) [101]. Consequently, using cleaner household fuels has been found essential in these areas [102]. Naz et al. [103] reported the household fuel and cooking activities as major causes of respiratory diseases and deaths in young children. In this context, avoiding the inappropriate indoor fuel and changes in the housing/kitchen designs have been suggested. Fatmi et al. [104] studied the production of indoor noxious gases due to the biomass fuel burning. Using biomass directly influenced the women’s and children’s health. Accordingly, the small and close houses with non-ventilated kitchens led to high levels of indoor smoke and pollutants, which increased the negative health effects [105]. High indoor PM levels were observed in the range of 200–5000 μg/m3, due to biomass fuel burning. Moreover, a high carbon monoxide concentration was found of ~29.4 ppm, which caused serious health effects. Shams et al. [106] measured the CO concentration in gas-fired kitchens of 54 bungalows and 25 apartments. The 8 hourly CO concentrations were found in the range of 2.13–5.29 ppm, which was higher than the WHO standards. Therefore, the CO level monitoring in the gas-fired kitchens was found essential.
Since 2009, biogas was used as an indoor fuel in rural areas of Pakistan to minimize the serious indoor health effects [107]. Recently, a study by Yasmin et al. [108] mentioned the adoption/non-adoption of biogas in the rural areas of Punjab. The multinomial logit regression was used to analyze the adoption behavior (Figure 5 and Table 1). According to the Pakistan Bureau of Statistics, nearly 52–67% population live in the rural areas. Formerly, domestic biomass or animal dung were used in these areas causing serious health issues [109]. Afterwards, the biogas utilization was enhanced in the rural areas due to high average education and awareness of people, improved kitchen designs, as well as building concrete houses.
In addition to fuel smoke, indoor smoking activities have caused harms to health as well as environmental issues [110]. Tobacco smoke (a secondhand smoke) caused major indoor pollution [111]. Naeem et al. [112] explored the indoor pollution due to tobacco smoke which caused hostile health effects in Lahore. The indoor smoking produced CO2 emissions as well as other airborne pollutants. The studies were conducted on 208 individuals, out of which 90% were non-smokers, while 9.1% were active smokers. A total of 38% of indoor inhabitants claimed headaches, whereas 15–23% individuals suffered from coughing/sneezing and eye irritation due to indoor air pollutants’ exposure. Hence, tobacco smoke directly influenced the public health. Zaidi et al. [113] reported that secondhand smoke caused a noteworthy public health threat. A portable air quality monitoring device was used; the TSI SidePak AM510 Personal Aerosol Monitor (TSI, St Paul, MN, USA) with an air drawing pump. The aerosol monitor was fitted with the 2.5 μm impactor for measuring the PM concentrations, using the mass-Median aerodynamic diameter of ≤2.5 μg. The data were collected from 39 indoor restaurants, bars, and cafes. The high concentration of PM2.5 ≤2.5 microns diameter was observed in tobacco smoke in Pakistan. The high level of PM2.5 ~1745 μg/m3 was obtained from smoking places, whereas the non-smoking zones had lower PM2.5 levels (~101 μg/m3). Moreover, the secondhand smoke caused cardiovascular and respiratory health risks [114,115].
The comparative analysis of the air quality of Pakistan and south-east Asian countries (India, Nepal, Sri Lanka, Bangladesh, and Bhutan) was performed [116]. The assessment was performed for CO, NO2, SO2, O3, Pb, PM10, and PM2.5 pollutants. The WHO standards were considered for comparison. The air quality level of Pakistan was found higher than the WHO standards. As compared to Sri Lanka, Bangladesh, and Bhutan, the Pakistan air quality level was observed lower and needed improvement. Consequently, the implementation of IAQ policies for public health monitoring was observed indispensable in Pakistan. Table 2 depicts the comparative data of air quality in Pakistan as well as South Asian countries.
The air quality data trends of Pakistan, India, Nepal, Bangladesh, Bhutan, and Sri Lanka were analyzed. According to a careful analysis, the poor indoor air quality led to environmental, health, and sustainability issues in the South Asia countries [117]. In Pakistan, the mean annual exposure to PM2.5 was 58.3 µg/m3 (1990), which steadily increased to 60.34 µg/m3 in 2017. The mean annual exposure to PM2.5 in India was higher (81.3 µg/m3) in 1990, which was further increased (90.9 µg/m3) in 2017. Moreover, Nepal’s exposure to PM2.5 was highest among all countries (~99.7 µg/m3) in 2017 (Figure 6). Hence, it can be concluded that the pollution exposure situation in Pakistan was worse than Bhutan and Sri Lanka, however, it was a little better than India and Bangladesh. However, the IAQ monitoring and regulatory standards need to be adopted in Pakistan.
Additionally, building materials have been major sources of indoor PM, VOC, radioactivity, and other pollutants in Pakistan. The radioactive pollution was mainly released from building and decorating materials. The ceramic building materials and natural stones caused the radioactive pollution. Radon was also generated from the bricks, stones, concrete, and asbestos-based building materials [118]. Volatile toxins were released from decorating materials such as paints, dyes, carpet, etc. The floor boards and sticking panels were sources of formaldehyde pollution. All these pollutants were major causes of cancer risks [119]. The wall/floor/roof coatings and paints had VOC levels of ~50–100 g/L. In Azad Kashmir City of Pakistan, the radon (from soil, gravel, sands, and bricks) exhalation rate was observed in the range of 171–649 mBq m−2 h−1 [120]. In addition, the clinical and toxicological studies reported bacterial, fungal, and algal growth on the interior and exterior of buildings. Moreover, the microbes’ colonization was detected on the stone/wall surfaces due to water, pH, and climatic factors. The resulting indoor PM, airborne particles, and bioaerosols caused several infectious and respiratory diseases. In Pakistan, the green building materials, low emissivity windows, as well as low VOC paints must be adopted for the ecofriendly and health purposes. Moreover, the cool bricks and fly ash bricks were suggested as the upcoming green materials in Pakistan [121].

3.3. Bioaerosols and Airborne Microflora in Residential Environments

The indoor air has been the main source of bioaerosols [122,123,124]. The bioaerosol concentrations in the indoor environments depend upon the building material, furniture, indoor inhabitants, and air from outside [125,126,127]. The indoor animals/pets in the rural and urban environments have produced bioaerosols in large amounts [128]. Mukhtar et al. [129] considered the bioaerosols (especially fungi) as hidden indoor killers in Pakistan. The genus Aspergillus of fungi was a predominant contaminant that caused serious health effects. This bioaerosol has been observed in numerous indoor buildings (houses, café, hospitals, laboratories) in Pakistan. Regular monitoring strategies have been required to investigate bioaerosol concentrations and health effects [130]. Nasir et al. [131] studied the bioaerosols in residential microenvironments in rural/urban sites. Among indoor bioaerosols, the Gram-negative bacteria and fungi were mainly detected [132]. The size distribution of the culturable indoor total bacteria, Gram-negative bacteria, and fungi was studied at the rural site. The six stage Andersen viable impactor was used for studying the indoor and outdoor bioaerosols. The impactor was designed for the particles of various size, shape, density, and aerodynamic size. The effects of humidity, temperature, and visible mold growth were recorded regarding human health and construction materials. The relative humidity and temperature were recorded using the Gasprobe IAQ 4 158 (BW Technologies Ltd., Mississauga, ON, Canada). The indoor temperature was about 26–28 °C. The mean indoor relative humidity was in the range of 51–67%. The indoor bacteria concentration was found to be quite high at about 14,650 cfu/m3. The size distribution of indoor bacteria was around 55–93%, that was higher than the indoor fungi [133]. The size distributions of indoor bacteria, Gram-negative bacteria, and fungi were also studied at the urban sites. High levels of the Gram-negative bacteria and fungi were observed [134]. Colbeck and co-workers [135] studied thirty residential houses in Lahore for indoor bioaerosols and PM levels. The indoor bioaerosols and PM were produced from cooking, cleaning, and smoking, along with the infiltrated outdoor air. The indoor air was simultaneously monitored in the kitchens and living rooms. The effect of ventilation on the IAQ level was observed for the change in indoor microenvironment per hour. High bioaerosol and PM2.5 levels were observed during the winter season in Lahore. The low ventilation rates elevated the indoor bioaerosol and PM2.5 levels.
Microflora have been a major source of toxins in the indoor environments [136,137]. Sidra et al. [138] monitored the microflora and PM in thirty houses in Lahore. The occurrences of airborne microorganisms and PM2.5 were measured using the real time aerosol monitors (DustTrak model 8520; TSI Inc., Shoreview, MN, USA) in kitchens and living rooms. The temperature, relative humidity, and CO2 levels were documented using the Gas probe IAQ (BW technologies). The temperature measured during the monitoring was about 18–37.8 °C, in the kitchens and living rooms. The average relative humidity levels were found to be around 20–75% in the kitchens and living rooms. Figure 7 demonstrates the percentage of different bacterial species detected in the kitchens and living rooms of different houses in Lahore.
The microflora concentrations in kitchens and living rooms were found in the range of 9829–14,469 cfu m−3. The seasonal variations in the indoor microflora in kitchens and living rooms were observed. Out of 30 houses, the inhabitants in 16 houses revealed severe allergic reactions. The Staphylococcus spp. was found as a dominant bacterial species with about 37% and 35.4% concentrations in kitchens and living rooms, respectively. Hence, the bioaerosols and microflora were major sources, which caused the indoor pollution.

3.4. Low-Temperature Health Hazards

Pakistan lies in extreme temperate zones [139]. The Pakistani climate has wide variations between extreme hot and cold temperature conditions [140]. In urban areas, the building materials used affect the indoor temperature during winter/summer [141]. Likewise, the indoor thermal environment has been maintained in residential buildings through the roof thermal insulation [142]. Indoor air-conditioning and heating systems contributed to about 30% of indoor CO2 emissions [137]. In rural areas in Peshawar, wood, mud bricks, leaves, and stones have been used as the raw building materials to maintain the comfortable indoor atmosphere. However, the indoor environment cannot be maintained in extremely cold rural areas such as Swat, Mansehra, Gilgit, etc. [143]. The cold weather has been found to be responsible for the indoor pollution due to the excessive fuel burning, less ventilation, as well as less cleaning possibilities. In the cold regions, the PM, CO, SOx, NOx, VOC, ozone, and lead were major indoor pollutants [144]. The air pollutant levels were found to be higher than the WHO safe standards [145]. In this contest, workplaces have been designed for cold environments and desired working conditions [146]. Subsequently, the indoor cold environments led to health hazards and low work productivity. The cold indoor environment caused health risks such as mental discomfort, respiratory, and skin complications [147]. In this case, safe heating systems must be used to maintain moderate indoor temperatures and to avoid the health effects. The indoor pollution control and monitoring systems must be utilized for attaining the safe IAQ levels [116].

4. Indoor Air Effluence Threats

4.1. Major Health Hazards of Indoor Air Contamination

As discussed in the previous sections, there are various sources of indoor pollution and potential pollutants in Pakistan. This section briefly summarizes probable health hazards due to the indoor pollution in Pakistan [148]. The pollutants have been generated from the indoor smoke of household fuels and smoking activities [149,150,151]. The pollutants from indoor fuels, tobacco, and dust include PM, COx, NOx, VOC, radon, ozone, flame retardants, bioaerosol, and microflora [152,153,154]. However, the health impacts of the indoor pollutants have been inadequately explored in the rural/urban locations. The influence of indoor PM2.5, CO, polyaromatic hydrocarbons, and formaldehyde pollutants (indoor fuel and dust) have caused chronic respiratory symptoms, asthma, and breath shortening [155]. For this purpose, the 8-channel indoor air quality monitor was used. Furthermore, continuous indoor exposure to these pollutants has produced cardiovascular mortality [156]. Farah et al. [157] studied the rural areas of Faisalabad. The 240 indoor inhabitants studied were focused on including the men and women. The health risks due to biomass fuel emissions involved breathing problems (60%), coughing (70%), asthma (38%), eye irritation (43%), allergies (33%), lung cancer (6%), along with other health issues. Here, the appropriate kitchen locations, lower cooking durations, safe fuel types, and pollution-free stoves have minimized the indoor air pollution. Kouser and Munir [158] investigated the acute respiratory infections due to indoor air pollution. The studies were carried out on community-level women and children under five years. The PM concentrations in the indoor air were responsible for the respiratory infections. The household fuel was suggested to be replaced with the safe energy sources, which prevented the health issues in indoor inhabitants [159].
Tariq et al. [160] reported that PM2.5, formaldehyde, and CO were responsible for chronic respiratory diseases such as breath shortening, bronchitis, and asthma in Karachi. Aslam et al. [161] scrutinized the effects of indoor polychlorinated biphenyls on human health in the Pakistani population. The pollutants were inhaled or ingested through the indoor air. The polychlorinated biphenyls were found to cause a high cancer risk of about 4.32 × 10−4 to the indoor inhabitants. Khan et al. [162] investigated the damaging effects of flame retardants (indoor dust) on human health in rural and industrial inhabitants. The indoor flame retardants caused cardiac, respiratory, and carcinogenic effects [163,164]. Hamid et al. [165] studied the polyaromatic hydrocarbon in Rawalpindi and Islamabad, cities of Pakistan. The high polyaromatic hydrocarbon concentrations of about 2132 pgm−3 (air) and ~90.0 ng·g−1 (dust) were observed. The indoor air and dust directly entered the human body through inhalation, which caused the respiratory system ailments and cancer risks [166]. The sustainable indoor fuels were suggested to meet the energy necessities and to lower the polyaromatic hydrocarbon generation [167]. Rafique et al. [168] studied radon in the indoor, enclosed residential houses. The radioactive radon concentrations increased the risk of lung cancer in the 35–55 years old population. The investigations of the indoor air pollutants and diseases provide the baseline data in Pakistan for taking further steps by the government/agencies and policy interventions.

4.2. Impact of Interior Physical Environment on Productivity of Indoor Workers/Academicians

Human productivity has been associated with indoor air pollution [169,170,171]. Saleem et al. [172] studied the indoor population in the higher education institutes of the Khyber Pakhtunkhwa in Pakistan. The institutes from Abbottabad, Peshawar, Mansehra, and Hazara were selected for the indoor air pollution investigations. It was observed that the building designs with the optimum ventilation, temperature comfort, as well as pollution monitoring contributed better towards the high indoor productivity of the academicians/workers. Cao et al. [72] discovered that the office dust contains high concentrations of toxic brominated or phosphorated flame retardants, which affected human health and workers’ productivity. The mean concentrations of flame retardants in the offices were observed as high around 128,000 ng·g−1, which caused the serious health effects. In the same way as other indoor pollutants, the dust particle concentration follows the seasonal order of winter > autumn > summer. Kamal et al. [173] investigated the effects of polycyclic aromatic hydrocarbons on the health and work efficiency of the auto-repairing and petroleum refinery workers. The high concentrations of polycyclic aromatic hydrocarbons were detected in white blood cells of the workers, which reduced the working efficiency and caused the lifetime cancer risks [174]. Lin et al. [175] measured the polyfluoroalkyl substances in the populations of northwestern Pakistan and western Afghanistan areas. The perfluoro butanoic acid was found as the major constituent of polyfluoroalkyl. The inhalation of polyfluoroalkyl in northwestern Pakistan and western Afghanistan areas was in the range of 0.07–3.98 and 0.01–0.33 pg/kg bw/d, respectively. The populations in both the countries revealed high carcinogenic effects.

4.3. Indoor Pollution in Hospital Environment

In Pakistan, the indoor pollution in the hospital environment has affected the work productivity of the doctors/nursing staff and the health of patients [176,177,178]. However, very few studies have been reported in this respect. Nimra et al. [179] correlated the airborne PM in operating theatres with the infection probability in patients. To study the effects of airborne PM on indoor air quality and patients’ health, various sensing devices have been used. The PM2.5 in air was monitored using the real time aerosol monitor (DustTrak, Model 8520, TSI Inc.). In addition, the CO2, CO, temperature, and relative humidity were monitored using the Gas Probe (BW technologies). In operating theatres, the DustTrak DRX Aerosol Monitor (Model 8533, TSI Inc.) was utilized for sampling. The studies were conducted in two major hospitals of Lahore, i.e., Services Hospital and Shalamar Hospital. In the orthopedic operating theatres, the high PM concentrations in the range of 757–970 μg/m3 were observed. Such high PM concentrations caused repeated infections in the patients who underwent operations. In this situation, the vertical laminar air-flow ventilation was used for cleaning the indoor air. In addition, the operation theater cleaning, personal hygiene, building age, and pollutant infiltration played important roles in maintaining the healthy indoor air quality in the hospitals to prevent infections/diseases [180].

5. Harmful Effects of the Indoor Pollution

  • Around 2.4 billion people worldwide (i.e., one-third of the global population) use open fires and stoves fueled by the biomass (wood, animal dung, crop, etc.), coal, and kerosene for cooking. These burning activities produce several harmful indoor air pollutants [181].
  • The indoor air pollution has been responsible for >4 million deaths per year, including over 2 million deaths of children (under 5 years) [20].
  • The effects of indoor pollution were observed in the form of >6 million premature deaths per annum [20].
  • The indoor air pollution has led to diseases such as pulmonary infections, lung cancer, strokes, heart diseases, chronic lung diseases, and so on [182,183].
  • Women and children seem to be more influenced by indoor cooking activities, which have caused great health effects [184].
  • The Environmental Protection Agency (EPA) refers to the IAQ within and around buildings. According to the EPA, the indoor pollution can cause major environmental risks to the public health. The common indoor pollutants include CO, radon, pests, dust, mites, lead, smoke, bacteria, bioaerosols, etc., in addition to the increased humidity and precipitation levels.
  • The indoor pollutants have caused short term effects such as eye irritation, nasal itching, throat rashes, headaches, fatigue, dizziness, asthma symptoms, etc. However, the long-term effects due to chronic exposure to indoor pollutants include the respiratory/heart diseases, as well as cancer effects.
  • According to a careful estimate, acute lung cancer risks of ~6% have been reported in the adult population due to unhealthy fuel usage [157].
  • According to a study in Pakistan, using unhealthy indoor fuels and living rooms with attached kitchens produced a child mortality rate of about 145 deaths/1000 live births [103]. On the other hand, houses using clean fuel or separate kitchens have ~10 deaths/1000 live births. Moreover, up to 80 deaths/1000 women have been reported because of indoor kitchen fuels [185]. Comparatively, the male population was found to be less affected.
  • In this concern, using clean fuels and safe indoor burning sources can reduce the indoor pollution to protect from health hazards. As per the WHO guidelines, safe fuels include solar energy, electricity, biogas, natural gas, and liquefied petroleum gas, which minimize the environmental pollution [186].

6. Indoor Air Quality Management and Challenges on Monitoring/Regulating IAQ in Pakistan

According to an analysis of IAQ levels of Pakistan and south-east Asian countries, the policy implementations have been found indispensable for maintaining the public health [187]. In this context, the real-time monitoring stations have been installed across the main cities of Pakistan such as Islamabad, Lahore, Karachi, and Peshawar, and the measured air quality levels were uploaded on the open access website [188]. Figure 8 displays the locations of the monitoring stations. The PM2.5 hourly real-time data were obtained from the official website. The image detection-based air quality research was performed through image processing and machine learning methods. In this method, the color of the sky can vary the PM2.5 and PM10 concentration detection using the visual camera images. Subsequently, the sensitivity was high and found to be affected by the weather conditions. In day time, high resolution camera images can be obtained. However, the image quality was compromised in the evening and night times. It was found difficult to access the remote areas with camera devices. On the other hand, the satellite images more effectively accessed the air quality situation. The indoor air cleaning set-ups have been designed and installed in offices, corporate spaces, and urban houses in Pakistan. The installation of air cleaning units can reduce the indoor dust pollution, VOC, and PM, which enhance the worker’s productivity [189,190]. There has been an increasing need to educate the public regarding indoor pollution and installing air monitoring units in Pakistan [191,192].
Table 3 presents the situation of indoor pollutants in rural and urban areas of Pakistan. Currently, the indoor air pollution scenarios include the sources, pollutants, and reasonable solutions desirable for controlling the contamination conditions. One important solution has been the use of renewable energy sources [193,194,195]. The solar power plants have been used in the Punjab, Sind, Baluchistan, and Kashmir regions in Pakistan [196]. The employment of solar energy plants can fulfil the current energy crises in Pakistan [197]. Using indoor ventilation systems can also reduce indoor air pollution levels [198].
Using air-conditioners can easily clean the indoor air [199,200,201]. The air-conditioner filters have been used to filter dust in Lahore [202]. The air-conditioners can also filter the organochlorine pesticides [203]. In this way, the organochlorine pesticides concentration in the range of 7.53–1272.87 ng/g can be settled. The indoor setting of the organochlorine pesticide pollutants has been found to cause a lifetime cancer risk [204]. Moreover, the residential, schools, and office building designs must be reconsidered to avoid the pollution sources and to improve the IAQ levels. Poverty has also greatly contributed to the choice of indoor fuel and indoor air pollution [205]. Therefore, the collective efforts of individuals, industries, and local governments have been desirable in Pakistan for improving the economic conditions of the rural inhabitants. The Pakistani government must facilitate individuals and local governments for creating awareness among the rural population for using safe indoor fuel.

7. Need of Industry–Academia–Research Cooperation to Support Indoor Air Pollution Control

In Pakistan, people living in rural and semi-urban areas are not much aware of indoor air pollution problems. In particular, there is no knowledge about harmful indoor cooking vapors, indoor PM, dust, smoking, germs, aerosols, radon, etc., in the rural population. The academic people can play an important role for the public awareness regarding indoor pollutants and their better cultural habits. In order to control the indoor air pollution and to avoid harmful effects, the immediate education and awareness is desirable in the rural areas in Pakistan. As discussed in the above sections, stove burning using unhealthy fuels has been reported as a major source of indoor pollution. There is a complete lack of awareness in the population about using safe indoor fuels and taking necessary cleaning and ventilation steps. The academics can conduct planned visits to such areas and deliver their knowledge to keep the healthy indoor environments and cultural awareness. In developing countries such as Pakistan, there should be educational and awareness camps regarding the indoor air pollution to educate the common public. Such efforts will make Pakistan a healthier place to live safely for the next several generations.
In Pakistan, only a few government/non-government organizations and academic institutes have been found working to improve the indoor air quality situation using advanced monitoring strategies, policy interventions, as well as adopting renewable energy technologies [206]. The theoretical models must be developed for establishing strong links between the indoor air quality management, academic/research institutes, along with the desired policy interventions in Pakistan.
We think that the role of academia is important for interpreting the fundamental science involved in the pollution sources and generation. The research institutions in Pakistan can further explore the impacts of indoor pollutants and monitoring strategies. Accordingly, the government organizations must develop work plans, collate databases, and engage policymakers for the efficient solutions. Furthermore, the local and private organizations can be involved in approving the indoor environmental management legislation and for providing incentives for setting up mechanisms for indoor environmental protection. The active communications between different stakeholders and government organizations are needed for the active policy implementations. Moreover, the government organizations and research institutes must conduct the long-term planned studies in various rural and urban areas of Pakistan to estimate current and changing pollutant concentrations in the indoor environments. The long-term studies on the health effects of indoor air pollution also need to be performed. According to our analysis, the proper conferences and policy developments by Pakistani stakeholders are required to define the action agenda to control, monitor, and regulate the IAQ levels and human health. The public awareness of using safe fuel, heating systems, and IAQ monitoring/regulation systems have been found to be indispensable in the rural/urban areas of Pakistan [207,208,209]. Hence, the overall IAQ situation can be improved through the serious involvement of individuals, local/private organizations, as well as academic and research institutions.

8. Conclusions

In this review, the overall situation of the indoor pollution in rural and urban areas of Pakistan has been described considering the pollutant type, indoor pollution sources, exposure level, and health hazards. Cooking, combustion, and burning have been identified as the major sources of the emission of indoor pollutants. Additionally, indoor smoking and dust also produce airborne toxins. In this context, the major indoor pollutants include PM, COx, NOx, VOC, bioaerosols, microflora, flame retardants, and other airborne, noxious organic compounds. The indoor air pollutants cause several harmful health effects. Therefore, strategies are required for developing and implementing the IAQ level enhancement strategies. The construction materials such as paints, coatings, floors, furniture, etc., must be developed using safe and inert materials emitting low VOC and indoor pollutants. Indoor garages must be built outdoors to minimize the indoor CO pollution. In addition, the indoor surfaces must be kept clean and dry to prevent moisture, germs, and bacteria. For controlling and managing indoor pollution, the indoor ventilation systems must be used. However, the ventilation cannot completely remove PM, VOC, toxic gases, and microorganisms in the air. The outdoor air infiltration is also a source of indoor pollutants. Thus, the advanced IAQ technologies such as filtration, adsorption, UV photocatalyst, indoor green plants, etc., must be adopted to minimize the indoor pollution. For IAQ monitoring, the advanced sensors may result in the removal of indoor pollutants. Among various pollutants, the PM such as PM1, PM2.5, and PM10 have been observed as major toxins emerging from indoor fuels, heating, and smoking sources. Consequently, the PM concentrations were found high ~10,000 μg/m3 in the indoor living places in Pakistan. The indoor PM pollutants affected the respiratory, pulmonary, cardiac, as well as nervous systems, which increased the cancer and mortality risks in adults. Furthermore, indoor dust has been found as a major source of airborne flame retardants. Subsequently, the ingestion of airborne flame retardants was found to be high at ~35 ng/g. The indoor microflora concentration was also detected as high in the range of 10,000–15,000 cfu m−3. The indoor flame retardants and microflora caused cancer and respiratory ailments in children and adults. The poor IAQ can also affect the work productivity in offices, work places, and academic buildings. In rural areas, the unsafe indoor fuels need to be replaced with efficient and less polluting fuels. Moreover, the residential designs and building materials need to be improved to minimize indoor pollution.
In our view, the indoor air pollution issues can be prevented through the public awareness and practical guidance to manage the safe IAQ levels. In this respect, immediate management practices must be adopted. It has been found to be extremely important to learn the principles for keeping the good indoor air quality. The maintenance of healthy and comfortable indoor environments demands urgent integration of monitoring and control systems along with the adaptations of indoor air quality standards. The buildings must be reassembled to attain good IAQ management practices. Creating necessary action plans can improve the IAQ and reduce IAQ problems. In this way, health risks can be minimized and indoor comfort and productivity can be increased. For attaining the safe indoor environment, there has been a strong need for long-term pollution studies, IAQ monitoring devices, government/agencies’ involvement, policy making, interventions, as well as a role for academia–industry links. These efforts can open future ways towards a safe, healthy, and ecological indoor environment in Pakistan.

Author Contributions

Conceptualization, A.K.; data curation, A.K.; writing—original draft preparation, A.K.; writing—review and editing, A.K., I.A., T.Z. and H.S. All authors have read and agreed to the published version of the manuscript.

Funding

This research received no external funding.

Data Availability Statement

Not applicable.

Conflicts of Interest

The authors declare no conflict of interest.

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Pollutants 03 00021 g001 550
Figure 1. Trend in yearly publications on indoor air pollution in Pakistan.
Figure 1. Trend in yearly publications on indoor air pollution in Pakistan.
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Figure 2. Steps to move forward from indoor air pollution to accomplishment of safe indoor air quality.
Figure 2. Steps to move forward from indoor air pollution to accomplishment of safe indoor air quality.
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Figure 3. Sources of fuel used from rural to urban areas vs. indoor air pollution and cost consumption in Pakistan.
Figure 3. Sources of fuel used from rural to urban areas vs. indoor air pollution and cost consumption in Pakistan.
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Figure 4. Type of indoor cooking fuel used [94]. Reproduced with permission from Elsevier.
Figure 4. Type of indoor cooking fuel used [94]. Reproduced with permission from Elsevier.
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Figure 5. Study area of rural central Punjab in Pakistan [108]. Reproduced with permission from Springer.
Figure 5. Study area of rural central Punjab in Pakistan [108]. Reproduced with permission from Springer.
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Figure 6. Population-weighted exposure to ambient PM2.5 pollution expressed in µg/m3 [117].
Figure 6. Population-weighted exposure to ambient PM2.5 pollution expressed in µg/m3 [117].
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Figure 7. Percentage of bacterial species observed in kitchens and living rooms of different houses in Lahore [138]. Three housing categories were defined as follows: * = Small: ≤ 126.5 m2; ** = Medium: > 126.5 m2 to 253 m2; *** = Large: > 253 m2. Reproduced with permission from Research Repository.
Figure 7. Percentage of bacterial species observed in kitchens and living rooms of different houses in Lahore [138]. Three housing categories were defined as follows: * = Small: ≤ 126.5 m2; ** = Medium: > 126.5 m2 to 253 m2; *** = Large: > 253 m2. Reproduced with permission from Research Repository.
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Figure 8. Study area and distribution of monitoring stations [188].
Figure 8. Study area and distribution of monitoring stations [188].
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Table
Table 1. Details of study of districts according to Pakistan Bureau of Statistics (2020) [108].
Table 1. Details of study of districts according to Pakistan Bureau of Statistics (2020) [108].
VariablesUnitDistricts
FaisalabadSargodhaJhang
PopulationTotalMillions5.42.62.8
MalePercentage50.751.552.0
FemalePercentage49.948.548.0
UrbanPercentage47.728.123.4
RuralPercentage52.371.976.6
Average
household size		Persons living in one houseNumber of persons7.26.56.5
House typePacca (cemented)Percentage69.877.7537.5
Kacha (mud)Percentage30.1722.2462.5
Mode of cookingGasPercentage of housing units26.79.05.1
OtherPercentage of housing units73.391.094.9
Number of animalsBuffaloes and cowsThousands242114951890
Financial institutionsCommercial banksNumber of branches365331
Microfinance institutionsNumber of banks223
Economic growthAverage annual growthPercentage2.51.972.16
Table
Table 2. Comparison of the air quality of Pakistan and South Asian countries [116]. Sustainable Development Policy Institute (open access).
Table 2. Comparison of the air quality of Pakistan and South Asian countries [116]. Sustainable Development Policy Institute (open access).
Parameters (Time Average)PakistanAir Quality Level for South Asia Countries (µg/m3)WHO
Standard
IndiaNepalSri
Lanka		BangladeshBhutan
Carbon Monoxide (CO) (8 h)5210,00010,000102000Not Applicable
Nitrogen Dioxide (NO2) (24 h)808080100Not givenNot givenNot Applicable
Sulphur Dioxide (SO2) (24 h)12080708036580125
Ozone (O3) (1 h)130180Not given200235Not given150–200
Lead (Pb) (Annual)10.500.5Not given0.5Not given0.5–1
Particulate Matter (PM10) (24 h)15010012010015010050
Particulate Matter (PM2.5) (24 h)3560Not given5065Not given25
Table
Table 3. Indoor pollutants, sources, and health effects in various rural and urban areas of Pakistan.
Table 3. Indoor pollutants, sources, and health effects in various rural and urban areas of Pakistan.
Region in
Pakistan		Indoor SettingSourcePollutantConcentrationHealth HazardsRef.
LahoreLiving areaTraffic/seasonal changesPM2.5>25 μg/m3Not reported[49]
KarachiRestaurants/cafés/clubsIndoor smoking; heating;
cooking;
hospitality		PM2.525–390 μg/m3Not reported[54]
Rural areas of PakistanLiving area/KitchenUse of biomass fuel;
indoor cooking		PM10, PM2.5, PM14000–8555 μg/m3Not reported[59]
Rural and urban areas of PakistanLiving area/KitchenIndoor biomass burningPM2.5, PM10PM10 (>50 μg/m3); PM2.5 (>25 μg/m3)Not reported[61]
Haripur cityLiving area/KitchenOutside trafficPM2.5, PM10PM2.5 23.7–126.0 μg/m3;
PM10 39.0–166.3μg/m3;		Not reported[65]
LahoreLiving area/KitchenOutside air due to industrial and traffic pollutionPM2.5, PM10, CO, NO2, SO2, O3Not reported64% of asthma patients[66]
Northern
Pakistan		Living area/KitchenBrick kilnsPM1, PM2.5, and PM10PM1, PM2.5, and PM10 concentrations 3377, 2305, and 3567.67 µg/m3, respectively.Not reported[67]
Rural areasLiving area/KitchenIndoor
dust exposure/ingestion		Polybrominated
diphenyl ether,
polychlorinated
biphenyl, tri-
(2-butoxyethyl)
phosphate, triphenyl phosphate		~15.2 ng/kg bw/dayNot reported[73]
Lahore, Faisalabad, BahawalnagarLiving area/KitchenIndoor dust; polychlorinated biphenyl concentrationsPolychlorinated biphenyls~34.39 ng/g, 9.94 ng/g, and 8.79 ng/g in Lahore, Faisalabad, Bahawalnagar, respectivelyNot reported[75]
Rural regionsLiving area/KitchenUnhealthy fuel (wood, crop residues, charcoal, coal, kerosene, and animal dung)Exposure to CO2, CONot reportedRespiratory infections in children[100]
Rural regionsLiving area/KitchenIndoor biomass; fuel burningPM, CO2, COPM level 200–5000 μg/m3 carbon monoxide (CO) level
~29.4 ppm		Not reported[104]
Bungalows and apartmentsLiving area/KitchenGas-fired kitchensCOCO concentrations in the range 2.13–5.29 ppmNot reported[106]
LahoreLiving area/KitchenTobacco smokePM;
CO2 emissions		Not reportedCoughing/
sneezing;
eye irritation		[112]
Pakistan citiesIndoor restaurants, bars, and cafesIndoor smokingPM, CO2 emissionsHigh PM2.5 level ~1745 μg/m3Not reported[113]
Urban/Rural areasLiving area/KitchenIndoor bacteriaBioaerosolsConcentration high i.e., 14,650 cfu/m3Not reported[131]
LahoreKitchens and living roomsMicroflora concentrationsMicroflora~9829–14,469 cfu m−3Not reported[138]
Rawalpindi and IslamabadLiving area/KitchenIndoor airPolyaromatic hydrocarbon~2132 pgm−3;
in dust ~90.0 ng·g−1		Respiratory
system/cancer risks		[165]
Urban areasOfficesIndoor airBrominated or phosphorated flame retardantsFlame
retardants concentration 128,000 ng·g−1		Loss of indoor working
productivity		[72]
LahoreHospitals;
operating theatres		Indoor airPMPM
concentrations
757–970 μg/m3		Repeated
infections in
patients		[179]
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Kausar, A.; Ahmad, I.; Zhu, T.; Shahzad, H. Impact of Indoor Air Pollution in Pakistan—Causes and Management. Pollutants 2023, 3, 293-319. https://doi.org/10.3390/pollutants3020021

AMA Style

Kausar A, Ahmad I, Zhu T, Shahzad H. Impact of Indoor Air Pollution in Pakistan—Causes and Management. Pollutants. 2023; 3(2):293-319. https://doi.org/10.3390/pollutants3020021

Chicago/Turabian Style

Kausar, Ayesha, Ishaq Ahmad, Tianle Zhu, and Hassan Shahzad. 2023. "Impact of Indoor Air Pollution in Pakistan—Causes and Management" Pollutants 3, no. 2: 293-319. https://doi.org/10.3390/pollutants3020021

APA Style

Kausar, A., Ahmad, I., Zhu, T., & Shahzad, H. (2023). Impact of Indoor Air Pollution in Pakistan—Causes and Management. Pollutants, 3(2), 293-319. https://doi.org/10.3390/pollutants3020021

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